Two-phase heat-transfer systems

[00002] The present application is a continuation-in-part of my PCT patent application Ser. No. 92/01654, filed Mar. 11, 1992, titled AIRTIGHT TWO-PHASE HEAT-TRANSFER SYSTEMS, and of my application Ser. No. 07/400,738, filed Aug. 30, 1989, now U.S. Pat. No. 5,333,677 titled EVACUATED TWO-PHASE HEAT-TRANSFER SYSTEMS; the cited PCT application being a continuation-in part of my application Ser. No. 07/400,738, filed Aug. 30, 1989, now U.S. Pat. No. 5,333,677 titled EVACUATED TWO-PHASE HEAT-TRANSFER SYSTEMS and of my then-pending application Ser. No. 07/696,853, filed May 7, 1991, now abandoned titled TWO-PHASE HEAT-TRANSFER SYSTEMS; the last-cited patent application being a continuation-in-part of my application Ser. No. 07/400,738, filed Aug. 30, 1989, now U.S. Pat. No. 5,333,677 titled EVACUATED TWO-PHASE HEAT-TRANSFER SYSTEMS and of my then-pending application Ser. No. 06/815,642, filed Jan. 2, 1986, now abandoned titled TWO-PHASE HEAT-TRANSFER SYSTEMS; the first of the two last-cited patent applications being a continuation-in-part of the second of the two last-cited patent applications; and the second of the two last-cited patent applications being a continuation-in-part of five following then-pending applications:

• • [00003] (a) Ser. No. 06/374,707, filed May 4, 1982, now abandoned titled TWO-PHASE HEAT-TRANSFER SYSTEMS,
  • [00004] (b) Ser. No. 06/362,148, filed Mar. 26, 1982, now abandoned titled VAPOR-GENERATING SYSTEMS,
  • [00005] (c) Ser. No. 06/361,784, filed Mar. 25, 1982, now abandoned titled POWER SYSTEMS,
  • [00006] (d) Ser. No. 06/355,520, filed Mar. 5, 1982, now abandoned priority date Jul. 7, 1980 (namely filing date of PCT/US80/0089), titled SOLAR TWO-PHASE HEAT-TRANSFER SYSTEMS, and
  • [00007] (e) Ser. No. 06/235,980, filed Feb. 19, 1981, now abandoned titled FORCED REFRIGERANT CIRCULATION SOLAR HEATING SYSTEMS.

[00008] The first four of the five last-cited applications were continuations-in-part or divisional applications of then co-pending applications

• • [00009] (1) Ser. No. 252,206, filed Apr. 8, 1981, titled FORCED REFRIGERANT-CIRCULATION SOLAR HEATING SYSTEMS,
  • [00010] (2) Ser. No. 252,205, filed Apr. 8, 1981, titled TWO-PHASE SOLAR HEATING SYSTEMS,
  • [00011] (3) Ser. No. 144,275, filed Apr. 28, 1980, titled SOLAR POWER SYSTEM, now U.S. Pat. No. 4,358,929, and
  • [00012] (4) Ser. No. 902,950, filed May 5, 1978, titled SOLAR HEATING SYSTEM, now U.S. Pat. No. 4,340,030.

[00013] The last two patent applications were continuations-in-part of then Ser. No. 457,271, filed Apr. 2, 1974, titled HEATING AND COOLING SYSTEMS, now U.S. Pat. No. 4,211,207; and application Ser. No. 235,980, filed Feb. 19, 1981, was a divisional application of then-pending application Ser. No. 902,950, and was filed for the purpose of provoking an interference with Bottum U.S. Pat. No. 4,220,138, filed Jan. 24, 1978.

[00014] The general technical field of the present invention pertains to systems that include one or more fluid circuits for transferring heat from one or more heat sources to one or more heat sinks with a heat-transfer fluid circulating around the one or more fluid circuits; a heat sink—to which heat is released by the heat-transfer fluid—having, at an instant in time, a maximum temperature below the maximum temperature of the heat source from which the released heat is absorbed at that instant in time. Such heat-transfer systems—which by the foregoing description exclude heat pumps—can be grouped into two general categories:

• • [00015] (a) single-phase heat-transfer systems having only fluid circuits whose heat-transfer fluid remains in the same phase (liquid or vapor phase) throughout a circulation cycle; and
  • [00016] (b) two-phase heat-transfer systems, having at least one fluid circuit whose heat-transfer fluid changes—at least under some operating conditions—at least in part from its liquid phase to its vapor phase and from its vapor phase back to its liquid phase during a circulation cycle.
    I shall hereinafter use the term ‘heat-transfer system’ to refer collectively to both single-phase and two-phase heat-transfer systems, and the term ‘refrigerant’ to refer to the heat-transfer fluid of the latter systems.

[00018] The specific technical field of the present invention pertains to two-phase heat-transfer systems. Such systems include, in addition to a heat-transfer fluid, hereinafter named a refrigerant, an evaporator and a condenser. The evaporator has one or more refrigerant passages in which the refrigerant absorbs heat from a heat source, at least in part, by changing from its liquid to its vapor phase. The condenser has one or more refrigerant passages in which the refrigerant releases heat to a heat sink, at least in part, by changing back from its vapor phase to its liquid phase at pressures which, at an instant in time, do not exceed the lowest pressure at which the refrigerant changes phase in the one or more evaporator refrigerant passages at that instant in time. Two-phase heat-transfer systems also include means for transferring refrigerant vapor from the evaporator refrigerant passages to the condenser refrigerant passages, and means for transferring liquid refrigerant from the condenser refrigerant passages to the evaporator refrigerant passages. The two just-cited means, and the evaporator and condenser refrigerant passages, form a circuit around which the refrigerant circulates while the refrigerant alternates between its liquid and its vapor phases. I shall refer to such a circuit as a ‘refrigerant principal circuit’.

[00019] Two-phase heat-transfer systems may have one or more refrigerant principal circuits with the same or different kinds of refrigerant, and each of these refrigerant principal circuits may have associated with it one or more refrigerant auxiliary circuits in the sense that they share a refrigerant-circuit segment with each refrigerant principal circuit. Refrigerant auxiliary circuits differ from refrigerant principal circuits in that

• [00020] (a) the former circuits may include evaporator or condenser refrigerant passages, but not both; and in that
• [00021] (b) only liquid refrigerant circulates around those circuits.

[00022] The invention disclosed in the present document pertains exclusively to airtight two-phase heat-transfer systems, namely to two-phase heat-transfer systems which, in the absence of a failure, do not ingest air while they are active or while they are inactive.

[00023] Many potentially important applications exist for two-phase heat-transfer systems whose refrigerant has, while they are not operating, saturated-vapor pressures substantially below ambient atmospheric pressure. However, prior-art embodiments of such two-phase heat-transfer systems have often been unable to compete successfully with single-phase heat-transfer systems. This is in particular true in the case of internal-combustion-engine prior-art two-phase cooling systems which have so far never been mass-produced, and have been used only in a few concept-demonstration vehicles and in a few ground installations.

[00024] I assert that a principal reason for the fact recited in the immediately preceding sentence is that most prior-art internal-combustion-engine two-phase cooling systems ingest air each time they are deactivated and their refrigerant approaches ambient air temperatures. I also assert that the prior-art describes no generally useful techniques for eliminating air ingestion from internal-combustion-engine cooling systems without

• [00025] (a) constraining operating pressures to be essentially equal to the current atmospheric pressure or to differ from the current atmospheric pressure by a constant amount; or without
• [00026] (b) using expensive glandless valves, and hermetically-sealed pumps, and requiring unacceptably-thick refrigerant-passage walls; and, in the case of internal-combustion engines with separate cylinder blocks and cylinder heads, without also using impractical cylinder-head gaskets.

[00027] The handicaps of prior-art internal-combustion-engine airtight two-phase cooling systems recited above under (a) and (b) apply also to many other airtight two-phase heat-transfer systems, whose refrigerant has, while they are not operating, saturated-vapor pressures substantially below ambient atmospheric pressure. Nevertheless, the prior art discloses no techniques for maintaining the internal pressure of inactive airtight two-phase heat-transfer systems above their refrigerant saturated-vapor pressure without imposing at least one of the constraints recited above under (a) and (b).

[00028] In addition to the handicaps recited above under (a) and (b), prior-art airtight two-phase heat-transfer systems in general, and internal-combustion-engine airtight two-phase cooling a systems in particular, have several additional major handicaps which must be eliminated before airtight two-phase heat-transfer systems can realize their full potential. The nature of those additional handicaps will become apparent whilst reading this DESCRIPTION.

[00029] Non-airtight two-phase heat-transfer systems do not have some of the handicaps of prior-art airtight two-phase heat-transfer systems. However, the air ingested by non-airtight systems has often been a sufficient handicap for them to be unable to compete successfully with single-phase heat-transfer systems. A prominent example where this has happened are steam building-heating systems which have been superseded by hot-water building-heating systems primarily because of the unacceptable rate of corrosion caused by air ingestion.

[heading-00030] 1. General Remarks

[00031] Terms between single quotation marks are defined in this DESCRIPTION. Some of those terms are defined in section III,A,2 under the heading PRELIMINARY DEFINITIONS, and others are defined elsewhere in this DESCRIPTION.

[heading-00032] 2. Preliminary Definitions

[00033] Certain terms used in describing and claiming the invention disclosed in the present document shall have the following meaning:

[00034] 1. The term ‘refrigerant’ is used to denote a fluid employed—under at least some operating conditions—to absorb heat, at least in part by changing from a liquid to a vapor and to release the absorbed heat at least in part by changing from a vapor back to a liquid. A refrigerant is said to ‘absorb latent heat’ when the refrigerant changes from a liquid to a vapor and to ‘release latent heat’ when the refrigerant changes from a vapor to a liquid; and a refrigerant is said to ‘absorb sensible heat’ when the refrigerant's (sensible) temperature rises while the refrigerant remains in one of the refrigerant's two phases (namely while the refrigerant remains in either its liquid phase or in its vapor phase) and to ‘release sensible heat’ when the refrigerant's (sensible) temperature falls while the refrigerant remains in one of the refrigerant's two phases. I intend the last four terms in quotation marks to apply to refrigerants which are a non-azeotropic mixture of single-component fluids as well as to refrigerants which are single-component fluids or an azeotropic mixture of single-component fluids. I shall often herein refer for brevity to fluids which are a non-azeotropic mixture of single-component fluids as ‘non-azeotropic fluids’. I shall also often refer herein to single-component fluids, and to fluids which are an azeotropic mixture of single-component fluids, collectively as ‘azeotropic-like fluids’, where the word ‘like’ indicates that, in contrast to non-azeotropic fluids, both single-component and azeotropic fluids boil at only one temperature while subjected to a given constant pressure. It follows from my definition of the term ‘refrigerant’ that the term ‘refrigerant’ is used herein to denote the function of a heat-transfer fluid and not the nature of a heat-transfer fluid; and is not used herein to restrict the kinds of heat-transfer fluid employed in the systems of the present invention to a particular class of fluids such as fluids more volatile than H₂O, and especially not to exclude water as for example in U.S. Pat. No. 4,120,289 (Bottum), 17 Oct. 1978, and U.S. Pat. No. 4,220,138 (Bottum), 02 Sep. 1980. Liquid refrigerant is said to ‘evaporate’ when it is changing from a liquid to a vapor, and refrigerant vapor is said to ‘condense’ when it is changing from a vapor to a liquid. And refrigerant is said to absorb heat by evaporation when refrigerant absorbs heat while changing from a liquid to a vapor, and to release eat by condensation when refrigerant releases heat while changing from a vapor to a liquid.

[00035] 2. The term ‘evaporator’ denotes means for transmitting heat from a heat source to a refrigerant and for evaporating liquid refrigerant; the evaporator having one or more surfaces which are the bounds of one or more enclosed spaces, named by me refrigerant passages, where refrigerant absorbs heat from the heat source at least in part by changing from a liquid to a vapor.

[00036] 3. The term ‘preheater’ denotes means for transmitting heat from a heat source to a refrigerant and for heating, namely increasing the (sensible) temperature of, liquid refrigerant; the preheater having one or more surfaces which are the bounds of one or more enclosed spaces, named by me refrigerant passages, where refrigerant absorbs heat from the heat source solely while the refrigerant is in the refrigerant's liquid phase.

[00037] 4. The term ‘superheater’ denotes means for transmitting heat from a heat source to a refrigerant and for heating, namely increasing the (sensible) temperature of, refrigerant vapor; the superheater having one or more surfaces which are the bounds of one or more enclosed spaces, named by me refrigerant passages, where refrigerant absorbs heat from the heat source solely while the refrigerant is in the refrigerant's vapor phase.

[00038] 5. The term ‘condenser’ denotes means for transmitting heat from a refrigerant to a heat sink and for condensing refrigerant vapor; the condenser having one or more surfaces which are the bounds of one or more enclosed spaces, named by me refrigerant passages, where refrigerant releases heat to the heat sink at least in part by changing from a vapor to a liquid.

[00039] 6. The term ‘subcooler’ denotes means for transmitting heat from a refrigerant to a heat sink and for cooling, namely decreasing the (sensible) temperature of, liquid refrigerant; the subcooler having one or more surfaces which are the bounds of one or more enclosed spaces, named by me refrigerant passages, where refrigerant releases heat to the heat sink solely while the refrigerant is in the refrigerant's liquid phase.

[00040] 7. The term ‘desuperheater’ denotes means for transmitting heat from a refrigerant to a heat sink and for cooling, namely decreasing the (sensible) temperature of, refrigerant vapor; the desuperheater having one or more surfaces which are the bounds of one or more enclosed spaces, named by me refrigerant passages, where refrigerant releases heat to the heat sink solely while the refrigerant is in the refrigerant's vapor phase.

[00041] 8. The term ‘hot heat exchanger’ denotes a member of the family consisting of all evaporators, preheaters, and superheaters.

[00042] 9. The term ‘cold heat exchanger’ denotes a member of the family consisting of all condensers, subcoolers, and desuperheaters.

[00043] 10. The term ‘heat exchanger’ denotes any heat exchanger; including any member of the family consisting of all hot heat exchangers, and all cold heat exchangers, as defined in definitions (8) and (9). I note that no restriction is imposed on the nature of the heat source of the hot heat exchangers defined under (2), (3), (4), and (8) in this section III, A, or on the nature of the heat sink of the cold heat exchangers, defined under (5), (6), (7), and (9), in this selfsame section; and it therefore follows—in contrast to the definition of the term ‘heat exchanger’ found in the art—that the heat exchangers cited hereinafter in this DESCRIPTION may—except where otherwise stated—include heat exchangers for transmitting heat from a solid to a fluid, and from a fluid to a solid, and are not restricted to heat exchangers for transmitting heat from a fluid to another fluid. A heat exchanger has a fluid inlet, and in particular a refrigerant inlet, consisting of a set of one or more inlet ports and a fluid outlet, and in particular a refrigerant outlet, consisting of a set of one or more outlet ports.

[00044] 11. The term ‘principal heat exchanger’ denotes a heat exchanger whose purpose is to transfer heat from a heat source of a two-phase heat-transfer system to one of the system's one or more refrigerants, or to transfer heat from a refrigerant of a two-phase heat-transfer system to one of the system's one or more heat sinks. A principal heat exchanger may be a hot heat exchanger, and in particular an evaporator, a preheater, or a superheater; or it may be a cold heat exchanger, and in particular a condenser, a subcooler, or a desuperheater. In this DESCRIPTION and in the CLAIMS, the terms ‘evaporator’, ‘preheater’, ‘superheater’, ‘condenser’, ‘subcooler’, and ‘desuperheater’, refer, for brevity, to principal heat exchangers, except where the qualifier ‘accessory’ is explicitly stated or obviously implied.

[00045] 12. The term ‘accessory heat exchanger’ in general, and the terms ‘accessory evaporator’, ‘accessory condenser’, ‘accessory subcooler’, etc. in particular, denote heat exchangers used for accessory functions. Examples of such accessory heat exchangers are the accessory condensers used to assist in removing refrigerant vapor from a refrigerant-vapor and non-condensable gas mixture, and which, to this end, transfer heat from the mixture to a heat sink, and accessory heat exchangers used to transfer heat from an inert gas to a heat sink and from a heat source to an inert gas.

[00046] 13. The term ‘separating surfaces’ denotes any set of surfaces (including surfaces forming a centrifugal separator) for separating the liquid and vapor phases of wet refrigerant vapor flowing over the set of surfaces. Separating surfaces may be an integral part of the refrigerant passages of an evaporator.

[00047] 14. The term ‘separator’ denotes means for separating the liquid and vapor phases of wet 2 refrigerant vapor; the separator having a vessel, named ‘separator vessel’, for storing, whenever appropriate, liquid refrigerant. A separator may include separating surfaces (often referred to as baffles) to help separate the liquid and the vapor phases of wet refrigerant vapor in the separator.

[00048] 15. The term ‘2-port separator’ denotes a separator having a first set of one or more ports through which usually wet refrigerant vapor enters the separator and liquid refrigerant exits the separator; and a separate second set of one or more ports through which refrigerant vapor exits the separator, the refrigerant vapor exiting the separator usually being drier than the refrigerant vapor entering the separator.

[00049] 16. The term ‘3-port separator’ denotes a separator having a first set of one or more ports through which usually wet refrigerant vapor enters the separator; a separate second set of one or more ports through which refrigerant vapor exits the separator, the refrigerant vapor exiting the separator usually being drier than the refrigerant vapor entering the separator; and a separate third set of one or more ports through which liquid refrigerant usually exits the separator but may also enter the separator.

[00050] 17. The term ‘3*-port separator’ denotes a separator having a first set of one or more ports through which usually wet refrigerant vapor enters the separator and through which liquid refrigerant exits the separator; a separate second set of one or more ports through which refrigerant vapor exits the separator, the refrigerant vapor exiting the separator usually being drier than the refrigerant vapor entering the separator; and a separate third set of one or more ports through which liquid refrigerant enters the separator.

[00051] 18. The term ‘4-port separator’ denotes a separator having a first set of one or more ports through which usually wet refrigerant vapor enters the separator; a separate second set of one or more ports through which refrigerant vapor exits the separator, the refrigerant vapor exiting the separator usually being drier than the refrigerant vapor entering the separator; a separate third set of one or more ports through which liquid refrigerant exits the separator; and a separate fourth set of one or more ports through which liquid refrigerant enters the separator.

[00052] 19. The term ‘separating assembly’ denotes means for separating the liquid and vapor phases of wet refrigerant vapor that does not include a vessel for storing liquid refrigerant. A separating assembly may be an integral part of a separator.

[00053] 20. The term ‘2-port separating assembly’ denotes a separating assembly having a first set of one or more ports through which usually wet refrigerant vapor enters the assembly and liquid refrigerant exits the assembly, and a separate second set of one or more ports through which refrigerant vapor exits the assembly, the refrigerant vapor exiting the assembly usually being drier than the refrigerant vapor entering the assembly. A 2-port separating assembly almost always includes separating surfaces.

[00054] 21. The term ‘3-port separating assembly’ denotes a separating assembly having a first set of one or more ports through which usually wet refrigerant vapor enters the assembly; a separate second set of one or more ports through which refrigerant vapor exits the assembly, the refrigerant vapor exiting the assembly usually being drier than the refrigerant vapor entering the assembly; and a separate third set of one or more ports through which liquid refrigerant exits the assembly. A 3-port separating assembly may include no separating surfaces other than the internal surfaces of the assembly's refrigerant passages, and may, for example, merely be a shallow V-tube having the first set of one or more ports essentially at the top of one of the two arms of the vee, the second set of one or more ports essentially at the top of the other arm of the vee, and the third set of one or more a ports essentially at the bottom of the vee.

[00055] 22. The term ‘separating device’ in this DESCRIPTION, and synonymously the term ‘separating means’ in the CLAIMS, denotes means for separating the liquid and vapor phases of wet refrigerant vapor. A separating device or means may be (1) a separator which includes a distinguishable separating assembly, (2) a separator which has no distinguishable separating assembly, or (3) a separating assembly.

[00056] 23. The term ‘refrigerant-circuit’ denotes a fluid circuit around which, whenever appropriate, a refrigerant circulates.

[00057] 24. The term ‘refrigerant line’ denotes a conduit for transferring refrigerant between components such as heat exchangers, separators, separating assemblies, refrigerant valves, refrigerant pumps, and receivers (see definition 41).

[00058] 25. The term ‘refrigerant-circuit segment’ denotes a part of a refrigerant circuit. A refrigerant-circuit segment may include several refrigerant lines connected in parallel, or the refrigerant passages of several similar, or several dissimilar, components, connected in parallel. These components include refrigerant valves (see definition 29), heat exchangers, separators, refrigerant pumps (see definition 33), and receivers (see definition 41).

[00059] 26. The term ‘refrigerant space’ denotes an enclosed space containing essentially only refrigerant. The term ‘refrigerant space’ subsumes the space inside a refrigerant line, and the space inside a refrigerant passage of a heat exchanger, a refrigerant pump, or a refrigerant valve.

[00060] 27. The term ‘refrigerant enclosure’ denotes a structure delineating the bounds of a set of one or more fluidly-connected refrigerant spaces containing in essence only refrigerant.

[00061] 28. The term ‘valve’ denotes a device by which the flow of a fluid, in its liquid or in its vapor phase, can be started, stopped, or regulated, by any known means capable of exerting a force on the particular fluid in the valve's one or more fluid passages. Examples of such a force include a mechanical, a magneto-hydrodynamic, an electro-dynamic, an electro-osmotic, and a capillary, force. Where the force is a mechanical force, the flow of the fluid through the valve's one or more fluid passages is started, stopped, or regulated, by a movable mechanical part which respectively opens, shuts, or partially obstructs, the valve's one or more fluid passages. The term ‘valve’, where the force is a mechanical force, includes an actuator for controlling the position of the movable mechanical part.

[00062] 29. The term ‘refrigerant valve’ denotes a valve where the fluid whose flow is controlled by the valve is a refrigerant in its liquid or in its vapor phase, and where the one or more fluid passages are refrigerant passages.

[00063] 30. The term ‘pump’ denotes a device for generating an increase in fluid pressure causing a fluid to flow in a desired direction. A pump has one or more fluid passages through which the fluid flows while the pump is active. A pump may be driven by any known means capable of exerting a force on the particular fluid in the pump's one or more fluid passages. Examples of such a force include a mechanical, a pneumatic, an hydraulic, a magneto-hydrodynamic, an electro-dynamic, an electro-osmotic, and a capillary, force. Where (1) means used to drive a pump is used exclusively to drive the pump and the pump is not driven by any other means, the term ‘pump’ includes the pump-driving means; and where (2) means used to drive a pump is also used for another purpose, or is merely an alternative means for driving a pump, the term ‘pump’ excludes the one or more pump-driving means. An example of the case recited under (1) in the present definition is an electric motor used to drive a pump where the electric motor is used exclusively to drive the pump; an example of the former of the two cases recited under (2) in the present definition is an engine used to drive a vehicle which is also used to drive a pump; and an example of the latter of the two cases recited under (2) in the present definition is a pump driven by an engine used to drive a vehicle and alternatively by an electric motor.

[00064] 31. The term ‘inherent capacity’, where the subject is a pump, denotes the fluid mass-flow rate induced by the pump, through the pump's one or more fluid passages under the action of the device or means driving the pump, for a given fluid pressure at the point where a fluid enters the pump's one or more fluid passages and for a given fluid-pressure rise in the pump's one or more fluid passages. The inherent capacity of a pump may, for a given fluid density, be essentially constant, or the inherent capacity of a pump may, for a given fluid density, be varied by the device driving the pump. In the particular case where the pump exerts a mechanical force on the fluid flowing through its one or more fluid passages, the pump's inherent capacity can be varied, for example, by one or more of the three techniques known as pump-speed control, pump-vane control, and on-off control. The fluid mass-flow rate delivered, under the earlier-cited fluid-pressure conditions in this definition, at a given point by a pump with a constant inherent capacity, or with a variable inherent capacity, may be modified by using a flow-control valve in series with the pump, or a flow-control valve in parallel with the pump. I shall refer to the latter valve as a ‘pump-recirculation valve’. (Pump-recirculation valves may be an integral part of a pump.)

[00065] 32. The term ‘effective capacity’ where the subject is a pump, denotes the fluid mass-flow rate delivered by a pump at a given fluid-circuit segment cross-section after the inherent capacity of the pump has been modified by the pump's recirculation valve or by a flow-control valve upstream from the given segment. The flow-control valve is, depending on the type of pump, located upstream from or downstream from the pump.

[00066] 33. The term ‘refrigerant pump’ denotes a pump causing liquid refrigerant to flow through a refrigerant-circuit segment in a desired direction. A refrigerant pump has one or more refrigerant passages through which liquid refrigerant flows while the refrigerant pump is active.

[00067] 34. The term ‘refrigerant principal circuit’ denotes a refrigerant circuit which includes the one or more refrigerant passages of an evaporator, and the one or more refrigerant passages of a condenser, (where the evaporator and the condenser are principal heat exchangers).

[00068] 35. The term ‘refrigerant auxiliary circuit’ denotes a refrigerant circuit, other than a refrigerant principal circuit. A refrigerant auxiliary circuit may include the one or more refrigerant passages of an evaporator and no condenser refrigerant passages; or the one or more refrigerant passages of a condenser and no evaporator refrigerant passages; or no evaporator or condenser refrigerant passages. Refrigerant circulating around an auxiliary refrigerant circuit remains in the same fluid phase during a circulation cycle; whereas refrigerant circulating around a refrigerant principal circuit changes—during each circulation cycle—at least in part, under most operating conditions, from the refrigerant's liquid phase to the refrigerant's vapor phase and from the refrigerant's vapor phase back to the refrigerant's liquid phase.

[00069] 36. The term ‘forced refrigerant-circulation principal circuit’, or more briefly, ‘FRC principal circuit’, denotes a refrigerant principal circuit around which a refrigerant circulates continuously or intermittently, primarily under the forced action of a refrigerant pump, while the refrigerant is transferring heat from a heat source to a heat sink.

[00070] 37. The term ‘natural refrigerant-circulation principal circuit’, or more briefly, ‘NRC principal circuit’, denotes a refrigerant auxiliary circuit around which a refrigerant circulates usually continuously, solely under the combined action of gravity and of the heat supplied by a heat source, while the refrigerant is transferring heat from the heat source to a heat sink.

[00071] 38. The term ‘forced refrigerant-circulation auxiliary circuit’, or more briefly, ‘FRC auxiliary circuit’, denotes a refrigerant circuit around which a refrigerant circulates continuously or intermittently, primarily under the forced action of a pump, while the refrigerant is transferring heat from a heat source to a heat sink.

[00072] 39. The term ‘natural refrigerant-circulation auxiliary circuit’, or more briefly, ‘NRC auxiliary circuit’, denotes a refrigerant auxiliary circuit around which a refrigerant circulates usually continuously, solely under the combined action of gravity and of heat supplied by a heat source, while the refrigerant is transferring heat from the heat source to a heat sink.

[00073] 40. The term ‘refrigerant principal configuration’, or more briefly ‘principal configuration’, denotes a material structure for transferring heat from one or more heat sources to one or more heat sinks; the configuration comprising

• [00074] (a) a refrigerant;
• [00075] (b) one or more refrigerant circuits having one and only one refrigerant principal circuit;
• [00076] (c) one or more hot principal heat exchangers and one or more cold principal heat exchangers, each having one or more refrigerant passages which are a part of at least one of the one or more refrigerant circuits, the hot principal heat exchangers including an evaporator and the cold principal heat exchangers including a condenser; and
• [00077] (d) one or more additional components—such as separating devices, refrigerant valves, refrigerant pumps, and receivers (see definition 41)—having one or more spaces or passages which are a part of the one or more refrigerant circuits, the one or more additional components excluding refrigerant-vapor expanders performing work and refrigerant-vapor compressors.
  I emphasize that the term ‘refrigerant principal configuration’, or more briefly ‘principal configuration’ as used in this DESCRIPTION and in the CLAIMS denotes a material structure and is an abbreviation c, for the more cumbersome term ‘refrigerant-principal-configuration structure’. I shall refer to the heat source from which the refrigerant in (the one or more refrigerant passages of) a hot heat exchanger of a principal configuration absorbs heat as the hot heat exchanger's heat source; and to the heat sink to which the refrigerant in (the one or more refrigerant passages of) a cold heat exchanger releases heat as the cold heat exchanger's heat sink. I note that the heat source of a hot heat exchanger of a principal configuration may be the refrigerant of another principal configuration; and I note that the heat sink of a cold heat exchanger of a principal configuration may also be the refrigerant of another principal configuration.

[00079] 41. The term ‘liquid-refrigerant receiver’, or more briefly ‘receiver’, denotes a vessel for storing, whenever appropriate, liquid refrigerant, provided the vessel is not a part of a separator.

[00080] 42. The term ‘1-port receiver’, or equivalently ‘surge-type receiver’, denotes a receiver having a single set of one or more ports through which liquid refrigerant enters and exits the receiver.

[00081] 43. The term ‘2-port receiver’, or equivalently ‘feed-through receiver’, denotes a receiver having a first set of one or more ports through which refrigerant condensate enters the receiver, and a second set of one or more ports through which liquid refrigerant, stored in the receiver, exits the receiver.

[00082] 44. The term ‘refrigerant-vapor transfer means’ denotes means, including one or more distinguishable refrigerant spaces, for transferring refrigerant vapor exiting a principal configuration's one or more evaporator refrigerant passages to the principal configuration's one or more condenser refrigerant passages. In particular, the term ‘refrigerant-vapor transfer means’ may, for example, (1) merely consist of a single refrigerant line, not excluding an essentially zero-length refrigerant line such as a port; or (2) may include space inside a separating device occupied by refrigerant vapor, one or more refrigerant lines for transferring refrigerant vapor exiting the one or more evaporator refrigerant passages to the separating device, and one or more refrigerant lines for transferring refrigerant vapor from the separating device to the one or more condenser refrigerant passages; the one or more refrigerant lines not excluding refrigerant lines forming a manifold.

[00083] 45. The term ‘liquid-refrigerant principal transfer means’ denotes means, including one or more distinguishable refrigerant spaces, for transferring liquid refrigerant exiting a principal configuration's one or more condenser refrigerant passages to the principal configuration's one or more evaporator refrigerant spaces. In particular, the term ‘liquid-refrigerant principal transfer means’ may, for example, (1) merely consist of a single refrigerant line; (2) may include a refrigerant line and the one or more refrigerant passages of a refrigerant pump and/or the one or more refrigerant passages of a refrigerant valve; or (3) may include a receiver not excluding a 1-port receiver, the one or more refrigerant passages of a refrigerant pump, a refrigerant line for transferring liquid refrigerant from the receiver to the one or more refrigerant-pump refrigerant passages, one or more refrigerant lines for transferring liquid refrigerant exiting one or more condenser refrigerant passages to the receiver, and one or more refrigerant passages for transferring liquid refrigerant from the one or more refrigerant-pump refrigerant passages to the one or more evaporator refrigerant passages; the last-cited one or more refrigerant lines not excluding & refrigerant lines forming a manifold.

[00084] 46. The term ‘liquid-refrigerant auxiliary transfer means’ denotes means for transferring liquid refrigerant, the means including one or more distinguishable refrigerant spaces which (1) are a part of a refrigerant principal configuration, but which (2) are not a part of a liquid-refrigerant principal transfer means. An important example of a liquid-refrigerant auxiliary transfer means is means for transferring liquid refrigerant from the separating device of a principal configuration to one or more points of the configuration's refrigerant principal circuit. Such a liquid-refrigerant auxiliary transfer means may, for instance, consist of (1) merely a single refrigerant line; (2) several refrigerant lines forming a manifold; or (3) the one or more refrigerant passages of an evaporator-overfeed pump, a refrigerant line for transferring liquid refrigerant from the separating device to the one or more refrigerant passages of the evaporator-overfeed pump, and one or more refrigerant lines for transferring liquid refrigerant from the one or more refrigerant passages of the evaporator-overfeed pump to one or more evaporator refrigerant passages, the one or more refrigerant lines not excluding refrigerant lines forming a manifold.

[00085] 47. The term ‘type 1 evaporator refrigerant auxiliary circuit’ denotes, in a principal configuration having several refrigerant circuits, a refrigerant auxiliary circuit which includes the one or more refrigerant passages of the configuration's evaporator; and which excludes

• [00086] (a) the one or more refrigerant passages of the configuration's condenser, and
• [00087] (b) the one or more refrigerant-pump refrigerant passages which are a part of the configuration's refrigerant principal circuit.

[00088] 48. The term ‘type 2 evaporator refrigerant auxiliary circuit’ denotes, in a principal configuration with several refrigerant circuits, a refrigerant auxiliary circuit which includes the one or more refrigerant passages of the configuration's evaporator and the one or more refrigerant-pump refrigerant passages which are a part of the configuration's refrigerant principal circuit; and which excludes the one or more refrigerant passages of the configuration's condenser.

[00089] 49. The term ‘evaporator refrigerant auxiliary circuit’ denotes a member of the family of all refrigerant auxiliary circuits consisting of type 1 evaporator refrigerant auxiliary circuits and type 2 evaporator refrigerant auxiliary circuits.

[00090] 50. The term ‘type 1 separator’ denotes all 3-port and 4-port separators having two sets of ports which are a part of a type 1 evaporator refrigerant auxiliary circuit.

[00091] 51. The term ‘type 2 separator’ denotes all 3-port and 4-port separators having two sets of ports which are a part of a type 2 evaporator refrigerant auxiliary circuit.

[00092] 52. The term ‘type 1′ separator’ denotes all 2-port and 3*-port separators having no set of ports which is a part of an evaporator refrigerant auxiliary circuit.

[00093] 53. The term ‘type 1 separating assembly’ denotes a 3-port separating assembly having two sets of ports which are a part of a type 1 evaporator refrigerant auxiliary circuit.

[00094] 54. The term ‘type 2 separating assembly’ denotes a 3-port separating assembly having two CD sets of ports which are a part of a type 2 evaporator refrigerant auxiliary circuit.

[00095] 55. The term ‘type 1′ separating assembly’ denotes a 2-port separating assembly having no set of ports which is a part of an evaporator refrigerant auxiliary circuit.

[00096] 56. The term ‘type 1 separating device or means’ denotes a type 1 separator or a type 1 separating assembly.

[00097] 57. The term ‘type 2 separating device or means’ denotes a type 2 separator or a type 2 separating assembly.

[00098] 58. The term ‘type 1′ separating device or means’ denotes a type 1′ separator or a type 1′ separating assembly.

[00099] 59. The term ‘subcooler refrigerant auxiliary circuit’ denotes a refrigerant auxiliary circuit which includes (1) the one or more refrigerant passages of a subcooler of a principal configuration, and (2) the one or more refrigerant passages of a refrigerant pump of the configuration; and which excludes (1) the one or more refrigerant passages of the configuration's evaporator, and (2) the one or more refrigerant passages of the configuration's condenser.

[00100] 60. The term ‘condensate-return pump’, or more briefly ‘CR pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of a refrigerant principal circuit and of no other refrigerant circuit.

[00101] 61. The term ‘evaporator-overfeed pump’, or more briefly ‘EO pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of a type 1 evaporator refrigerant auxiliary circuit and of no other refrigerant circuit.

[00102] 62. The term ‘dual-return pump’, or more briefly ‘DR pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of a refrigerant principal circuit and of a type 2 evaporator refrigerant auxiliary circuit belonging to the same principal configuration as the refrigerant principal circuit, and which are a part of no other refrigerant circuit.

[00103] 63. The term ‘subcooler-circulation pump’, or more briefly ‘SC pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of a subcooler refrigerant auxiliary circuit and of no other refrigerant circuit.

[00104] 64. The term ‘hybrid-flow pump’, or more briefly ‘HF pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of a refrigerant principal circuit and of a subcooler refrigerant auxiliary circuit belonging to the same principal configuration as the refrigerant principal circuit, and which are a part of no other refrigerant circuit.

[00105] 65. The term ‘principal-circulation pump’, or more briefly ‘PC pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of a refrigerant principal circuit. The one or more refrigerant passages of a principal-circulation pump may, for example, be (1) a part of no other refrigerant circuit, as in the case of a condensate-return pump; (2) also a part of a type 2 evaporator refrigerant auxiliary circuit of the same principal configuration, as in the case of a dual-return pump; or (3) also a part of a certain type of subcooler refrigerant auxiliary circuit of the same principal configuration, as in the case of a hybrid-flow pump.

[00106] 66. The term ‘liquid-refrigerant reservoir’, or more briefly ‘LR reservoir’, denotes a vessel for storing liquid refrigerant, the vessel not being a part of a principal configuration.

[00107] 67. The term ‘liquid-refrigerant ancillary transfer means’, or more briefly ‘ancillary transfer means’, denotes means for transferring liquid refrigerant from an LR reservoir to a principal configuration and for transferring liquid refrigerant from the principal configuration to the LR reservoir. An ancillary transfer means usually includes one or more refrigerant lines, and may also include the one or more refrigerant passages of one or more refrigerant pumps, and/or the one or more refrigerant passages of a refrigerant valve. However, an ancillary transfer means may sometimes merely be a port through which liquid refrigerant, in the LR reservoir, flows into the principal configuration's one or more refrigerant circuits, and through which liquid refrigerant, in the principal configuration's one or more refrigerant circuits, flows into the LR reservoir.

[00108] 68. The term ‘liquid-transfer pump’, or more briefly ‘LT pump’, denotes a refrigerant pump having one or more refrigerant passages which are a part of an ancillary transfer means and of no other liquid-refrigerant transfer means.

[00109] 69. The term ‘refrigerant ancillary configuration’, or more briefly ‘ancillary configuration’, denotes a material structure for storing liquid refrigerant and for transferring liquid refrigerant between the ancillary configuration's LR reservoir and a principal configuration; the ancillary configuration comprising the LR reservoir and an ancillary transfer means, and no principal heat exchanger.

[00110] 70. The term ‘refrigerant configuration’ denotes a material structure consisting in essence of a single principal configuration and one or more ancillary configurations, and having only one refrigerant enclosure.

[00111] 71. The term ‘airtight refrigerant configuration’ denotes a refrigerant configuration having a refrigerant enclosure

• [00112] (a) from which essentially all air has been removed;
• [00113] (b) from which, after the enclosure has been charged with the correct amount of refrigerant mass, essentially no refrigerant escapes (except in the case of failure); and
• [00114] (c) into which, after the enclosure has been charged with the correct amount of refrigerant mass, essentially no air enters (except in the case of failure) either because
  • [00115] (1) the refrigerant's pressure at each point of the enclosure always stays above the current pressure of air outside the enclosure at the selfsame point, or because
  • [00116] (2) the refrigerant enclosure is made of airtight components joined together so that essentially no air can enter the enclosure even at a point where the refrigerant's pressure (inside the enclosure) is below the current pressure of air outside the enclosure at the selfsame point.
    The qualifier ‘essentially’, used under (a) in the present definition, signifies that the amount of air remaining in the refrigerant enclosure—after the action recited under (a)—is small enough not to affect adversely significantly the heat-transfer effectiveness of, or the refrigerant in, the airtight refrigerant configuration. {Essentially all air may be removed from the refrigerant enclosure by using any known means, including a vacuum pump or a scavenging gas (which may be the refrigerant's vapor.)} The qualifier ‘essentially’, used under (b) in the present definition, signifies that the rates at which refrigerant escapes—including during occasional purges of non-condensable gases—from the refrigerant enclosure are low enough for no make-up refrigerant to be needed for typically several years (after the time at which the refrigerant enclosure was charged with refrigerant). And the qualifier ‘essentially’, used under (c) in the present definition, signifies the rates at which air enters the refrigerant enclosure are low enough for the resulting increase in the mass of air contained in it not to affect adversely significantly the heat-transfer effectiveness of, or the refrigerant in, the airtight refrigerant configuration for typically several years.

[00118] 72. The term ‘inert gas’ denotes a gas which does not react chemically in a significantly adverse manner with the refrigerant employed, or with the internal surfaces of the walls of an airtight enclosed space within which the refrigerant and the inert gas are contained, during the operating life of the equipment having the airtight enclosed space. Consequently, the term ‘inert gas’, used in this DESCRIPTION and in the CLAIMS, not only denotes gases usually referred to as inert (such as the noble gases); but also denotes gases such as hydrogen and CO₂, or gases such as multi-element gases containing hydrogen and CO₂, where they do not react chemically in a significantly adverse manner with the refrigerant, or with the internal surfaces of the walls of an airtight enclosed space within which the refrigerant and the inert gas are contained, during the operating life of the equipment having the airtight enclosed space. In particular, the term ‘inert gas’ includes a gas containing a significant amount of oxygen at the time the gas is inserted in an enclosed space—made immediately thereafter airtight—even where the walls of the enclosed space include one or more metals; provided (1) the refrigerant's heat-transfer properties are essentially unaffected, and provided (2) the one or more metals have essentially not been corroded, by the time essentially all the inserted oxygen has been absorbed by the one or more metals. Thus air may—depending on the refrigerant employed, and on the surfaces with which the refrigerant is in direct contact—be an inert gas. The term ‘inert gas’ also denotes a gas which does not condense over the entire range of operating and environmental conditions experienced by airtight configurations (see definition 86) containing an inert gas.

[00119] 73. The term ‘inert-gas reservoir’, or more briefly ‘IG reservoir’, denotes a vessel for storing inert gas; but may contain refrigerant vapor mixed primarily with the inert gas, and may even contain liquid refrigerant.

[00120] 74. The term ‘gas-transfer valve’, or more briefly ‘GT valve’, denotes a valve where the fluid whose flow is controlled by the valve is an inert gas, and where the one or more fluid passages are inert-gas passages interconnecting two spaces containing inert gas.

[00121] 75. The term ‘gas-transfer pump’, or more briefly ‘GT pump’, denotes a pump for causing inert gas to flow in a desired direction. A GT pump has one or more inert-gas passages through which inert gas flows while the GT pump is active.

[00122] 76. The term ‘condensate-type refrigerant-vapor trap’ denotes means for removing refrigerant vapor from a fluid which is a mixture of inert gas and refrigerant vapor, the means including means for condensing at least a portion of the refrigerant vapor mixed with the inert gas. A condensate-type refrigerant-vapor trap has a first set of one or more ports through which the inert-gas and refrigerant-vapor enters the trap, and a separate second set of one or more ports through which inert gas, or inert gas and refrigerant vapor, exit the trap. Where inert gas and refrigerant vapor exit a condensate-type refrigerant-vapor trap the mass-flow rate at which refrigerant vapor exits the trap is, under most operating conditions, lower than the mass-flow rate at which refrigerant vapor enters the trap. A condensate-type refrigerant-vapor trap may also have a separate third set of one or more ports through which liquid refrigerant exits the trap. In condensate-type refrigerant-vapor traps having no third set of ports, liquid refrigerant, generated in the traps, exit the traps through their first set of one or more ports.

[00123] 77. The term ‘inert-gas line’ denotes a conduit for transferring inert gas, or a mixture of inert gas and refrigerant vapor, between the components of an airtight configuration. An inert-gas line may at times also contain a small amount of liquid refrigerant.

[00124] 78. The term ‘inert-gas transfer means’, or more briefly ‘IG transfer means’, denotes means for transferring inert gas from an IG reservoir to a principal configuration's one or more refrigerant circuits. An IG transfer means usually includes one or more inert-gas lines; and may also (1) include the one or more inert-gas passages of one or more GT pumps, and/or the one or more inert-gas passages of one or more gas-transfer valves; and/or (2) the one or more inert-gas passages of a condensate-type refrigerant-vapor trap.

[00125] 79. The term ‘inert-gas configuration’, or more briefly ‘IG configuration’, denotes a material structure for storing inert gas, and for controlling the transfer of inert gas between the IG configuration and the one or more refrigerant circuits of a principal configuration. An IG configuration includes an IG reservoir, and active means for causing said inert-gas transfer. The inert gas may, in at least a part of an IG configuration, be mixed with refrigerant vapor.

[00126] 80. The term ‘inert-gas passive configuration’, or more briefly ‘IGP configuration’, denotes a material structure for storing inert gas and for transferring inert gas between the IGP configuration and the one or more refrigerant circuits of a principal configuration, the IGP configuration including no active means for causing said inert-gas transfer. Consequently, the IG transfer means of an IGP configuration includes no GT-pump inert-gas passages and no GT-valve inert-gas passages. However, an IGP configuration may include one or more valves which perform a different function from that of a GT valve. Examples of non-GT valves are charging, purging, and pressure-relief valves.

[00127] 81. The term ‘refrigerant & inert-gas space’ or more briefly ‘R&IG space’, denotes an enclosed space containing essentially only refrigerant and inert gas.

[00128] 82. The term ‘refrigerant & inert-gas enclosure’, or more briefly ‘R&IG enclosure’, denotes a structure determining the bounds of a set of fluidly-connected R&IG spaces containing collectively in essence only refrigerant and inert gas.

[00129] 83. The term ‘refrigerant & inert-gas configuration’, or more briefly ‘R&IG configuration’, denotes a material structure consisting in essence of

• [00130] (a) a single principal configuration and one or more IG configurations, or of
• [00131] (b) a single principal configuration, one or more IG configurations, and one or more ancillary configurations;
  and having only one R&IG enclosure.

[00133] 84. The term ‘refrigerant and inert-gas passive configuration’, or more briefly ‘R&IGP configuration’ denotes a material structure consisting in essence of

• [00134] (a) a single principal configuration and one or more IGP configurations, or of
• [00135] (b) a single principal configuration, one or more IGP configurations, and one or more ancillary id configurations;
  and having only one R&IG enclosure.

[00137] 85. The modifier ‘airtight’ (1) in the term ‘airtight refrigerant & inert-gas configuration’, or ore briefly ‘airtight R&IG configuration’, or (2) in the term ‘airtight refrigerant and inert-gas passive configuration’, or more briefly ‘airtight R&IGP configuration’, denotes respectively an R&IG configuration, or an R&IGP configuration, having an R&IG enclosure

• [00138] (a) from which, after the enclosure has been charged with the correct amounts of refrigerant and inert gas, essentially no refrigerant or inert gas escapes (except in the case of failure); and
• [00139] (b) into which, after the enclosure has been charged with the correct amount of refrigerant mass, essentially no air enters (except in the case of failure) either because
  • [00140] (1) the total pressure of the refrigerant and the inert gas, at each point of the enclosure, always stays above the current pressure of the air outside the enclosure at the selfsame point, or because
  • [00141] (2) the R&IG enclosure is made of components joined together so that essentially no air can enter the enclosure even at a point where the total pressure of the refrigerant and the inert gas (inside the enclosure) is below the current pressure of air outside the enclosure at the selfsame point.
    The qualifier ‘essentially’, used under (a) in the present definition, signifies that the rates at which refrigerant, or inert gas, escapes—including during occasional purges of non-condensable gases—from the refrigerant enclosure are low enough for no make-up refrigerant and no make-up inert gas to be needed for typically several years (after the time at which the refrigerant enclosure was charged with refrigerant and inert gas). And the qualifier ‘essentially’, used under (b) in the present definition, signifies the rates at which air enters the refrigerant enclosure are low enough for the resulting increase in the mass of air contained in it not to affect adversely significantly the heat-transfer effectiveness, the refrigerant, or the inert gas, in the R&IG enclosure for typically several years.

[00143] 86. The term ‘airtight configuration’ denotes an airtight refrigerant configuration, an airtight R&IG configuration, or an airtight R&IGP configuration.

[00144] 87. The term ‘supplementary-configuration means’ in the CLAIMS denotes a refrigerant ancillary configuration, an IG configuration, or an IGP configuration.

[00145] 88. The term ‘inside’, where the subject is an airtight refrigerant configuration, is an abbreviation for the phrase ‘inside the refrigerant enclosure of the airtight refrigerant configuration’. The term ‘inside’, where the subject is an airtight R&IG configuration, is an abbreviation for the phrase ‘inside the R&IG enclosure of the airtight R&IG configuration’. The term ‘inside’, where the subject is an airtight R&IGP configuration, is an abbreviation for the phrase ‘inside the R&IGP enclosure of the airtight R&IGP configuration’. Lastly, the term ‘inside’, where the subject is an airtight configuration, is an abbreviation for, as applicable, the phrases ‘inside the airtight refrigerant configuration’, ‘inside the airtight R&IG configuration’, or ‘inside the airtight R&IGP configuration’.

[00146] 89. The term ‘total pressure’, where the subject is an airtight configuration, a principal configuration, a refrigerant ancillary configuration, an IG configuration, or an IGP configuration, denotes the sum of the partial refrigerant pressure and the partial inert-gas pressure inside one of the five last-cited configurations.

[00147] 90. The term ‘airtight two-phase heat-transfer system’ denotes a system which includes an airtight configuration.

[00148] 91. The term ‘supercharger’ denotes any device employed to increase the pressure, and hence the density, of the combustion or intake air supplied to an internal combustion engine. In particular, the term ‘supercharger’ includes a mechanically-driven supercharger, and an exhaust-gas-driven supercharger, usually referred to as a ‘turbocharger’.

[00149] 92. The term ‘hot fluid’ denotes a heat source of an airtight configuration, or more specifically a heat source of an airtight configuration's principal configuration. A hot fluid may be a liquid, a gas, or a fluid which changes from its vapor to its liquid phase while it releases heat. In the last of the just-cited three cases the hot fluid may, in particular, be the refrigerant of another airtight configuration. A hot fluid of an airtight configuration transmits heat to the airtight configuration's refrigerant through one or more of the three modes of heat transfer known in the art as conduction heat transfer, convection heat transfer, and radiation heat transfer.

[00150] 93. The term ‘cold fluid’ denotes a heat sink of an airtight configuration, or more specifically of a heat sink of the airtight configuration's principal configuration. A cold fluid may be a liquid, a gas, or a fluid which changes from its liquid to its vapor phase while it absorbs heat. In the last of the just-cited three cases the cold fluid may, in particular, be the refrigerant of another airtight configuration. The refrigerant of an airtight configuration transmits heat to a cold fluid of the airtight configuration through one or more of the three modes of heat transfer known in the art as conduction heat transfer, convection heat transfer, and radiation heat transfer.

[00151] 94. The terms ‘hot-fluid valve’ and ‘cold-fluid valve’ denote a valve where the fluid whose flow is controlled by the valve is respectively a hot fluid and a cold fluid, in either their liquid or their vapor phase, and where the one or more fluid passages are respectively hot-fluid passages and cold-fluid passages.

[00152] 95. The terms ‘hot-fluid pump’ and ‘cold-fluid pump’ denote a pump for causing respectively a hot fluid and a cold fluid—in either their liquid or their vapor phase—to flow in a desired direction. The device has one or more fluid passages through which the hot or cold fluid flows while the device is active.

[00153] 96. The term ‘motor’ denotes any means for generating mechanical power irrespectively of the source of energy transformed by the motor into mechanical power. Thus, for example, the term ‘motor’ subsumes an internal-combustion engine and an electric motor.

[00154] 97. The term ‘signal’ denotes any means—including electrical, pneumatic, and hydraulic means—for transmitting information about a thing, and in particular information relating to the current value of a parameter characterizing the state of the thing; or for transmitting information about a required action to be performed by an active device—and in particular about the action to be performed by a refrigerant pump or by a refrigerant valve.

[00155] 98. The term ‘transducer’ denotes any means for transforming a parameter characterizing state of a thing—and in particular of a refrigerant—into a signal representing the current value the thing's characterizing parameter.

[00156] 99. The term ‘control unit’ denotes a unit which receives signals from transducers and, on the basis of instructions stored in the unit, generates signals controlling the activities of one or more controllable elements such as pumps and valves. A control unit is usually a microcontroller, with a self-checking capability, having a microprocessor, a read-only memory for storing preselected instructions, a random-access memory for storing signals received by the control unit, and analog and/or digital input-output units for receiving signals from transducers and for supplying signals to one or more controllable elements and to system-status indicators. I distinguish between (1) a principal control unit, referred to in this DESCRIPTION as a ‘central control unit’, or more briefly as a ‘CCU’, because it corresponds to the central control units of the systems disclosed in my co-pending U.S. patent application Ser. No. 400,738, filed 30 Aug. 1989, and (2) a ‘minimum-pressure-maintenance control unit’, or more briefly an ‘MPMCU’, used only to control a system of the invention while the system's principal configuration is inactive.

[00157] 100. The term ‘active’, where used to indicate the state of a principal configuration, denotes that refrigerant is circulating at a significant rate around at least one of the principal configuration's refrigerant circuits.

[00158] 101. The term ‘inactive’, where used to indicate the state of a principal configuration, denotes that refrigerant is circulating at a significant rate around none of the principal configuration's one or more refrigerant circuits.

[00159] 102. The term ‘void fraction’, where the subject is a point along and inside a refrigerant line or a refrigerant passage, denotes the proportion of space occupied by refrigerant vapor at said point, the void fraction being zero where no refrigerant vapor is present and unity where no liquid refrigerant is present.

[00160] 103. The term ‘flooded’, where the subject is a point on the one or more refrigerant-side heat-transfer surfaces of the condenser of a principal configuration, denotes,

• [00161] (a) where the one or more refrigerant-side heat-transfer surfaces are the one or more internal surfaces—including extended internal surfaces—of a tube or duct, that the void fraction in the tube or duct is zero in the immediate neighborhood of the point; and
• [00162] (b) where the one or more refrigerant-side heat-transfer surfaces are the one or more external surfaces—including extended external surfaces—of a tube or duct, that the one or more external surfaces of the tube or duct are immersed in liquid refrigerant in the immediate neighborhood of the point.

[00163] 104. The term ‘pre-prescribed’, where used to qualify the way in which something occurs, denotes that way has been specified during the design of a system of the invention. And the term ‘certain pre-prescribed’, where used to qualify operating conditions of a system of the invention, denotes the operating conditions have been specified during the design of the system.

[00164] 105. The term ‘characterizing parameter’ denotes a parameter providing information about the state of a thing; and in particular the state of (1) an airtight configuration; (2) a heat source of an airtight configuration; (3) the equipment in which the heat source is located; (4) a heat sink of an airtight configuration; (5) the equipment in which the heat sink is located; or (6) the environment of an airtight configuration, where the term ‘environment’ is defined in definition (112). Where an airtight configuration is a refrigerant configuration, the state of an airtight configuration includes the state of the airtight configuration's structure and the state of the airtight configuration's refrigerant; and where an airtight configuration is an R&IG configuration, the state of the airtight configuration includes the state of the airtight configuration's refrigerant, and the state of the airtight configuration's inert gas. (A characterizing parameter may merely be the position of a manually-operated on-off switch.)

[00165] 106. The term ‘preselected’ where used to qualify the value of a parameter characterizing the state of a thing, or to specify an operating condition, or a range of operating conditions, denotes that the value of the parameter, the operating condition, or the range of operating conditions, respectively, has been specified during the design of a system of the invention. The preselected value of a characterizing parameter—where not otherwise stated or obvious from the context—may be (1) a single value, (2) a value below a preselected upper limit, (3) a value above a preselected lower limit, or (4) a value between a preselected upper limit and a preselected lower limit. A preselected single value, a preselected upper limit, or a preselected lower limit, may (1) be fixed, (2) have a range of manually selectable fixed values, or (3) change with time in a pre-prescribed way as a function of one or more preselected characterizing parameters.

[00166] 107. The term ‘preselected range of operating conditions’, and the term ‘preselected range of environmental conditions’, where the subject is an airtight configuration, denote respectively the entire range of operating conditions under which the airtight configuration is designed to function and the entire range of environmental conditions under which the airtight configuration has a specified property; the preselected range of operating conditions and environmental conditions being specified, during the airtight configuration's design, in terms of preselected ranges for the values of one or more preselected characterizing parameters.

[00167] 108. The term ‘steady-state conditions’, where the subject is an airtight configuration, denotes operating conditions under which all characterizing parameters affecting refrigerant flow, and where applicable inert-gas flow, in the airtight configuration, change at a negligible rate compared to the slowest response rate of the airtight configuration's one or more refrigerant circuits, and where applicable inert-gas circuits.

[00168] 109. The term ‘transient conditions’, or more briefly ‘transient’, where the subject is an airtight configuration, denotes operating conditions under which at least one characterizing parameter affecting refrigerant flow, and where applicable inert-gas flow, changes at a faster rate than the slowest response rate of the airtight configuration's one or more refrigerant circuits, and where applicable inert-gas circuits.

[00169] 110. Each of the two terms ‘upstream’ and ‘downstream’ denotes the relative location of two points, or of two components, with respect to the direction of flow of, as applicable, a refrigerant, an inert gas, a hot fluid, or a cold fluid. The last-cited two terms apply to the case where, as applicable, the refrigerant, the hot fluid, or the cold fluid, flows in only one direction under steady-state conditions, and refer to the direction of flow of respectively the refrigerant, the hot fluid, or the cold fluid, under those conditions.

[00170] 111. The term ‘amount of liquid’ denotes the volume occupied by a liquid.

[00171] 112. The term ‘heating load’ denotes the rate at which heat is transmitted from a heat source to a refrigerant. (A heat source may be a refrigerant.)

[00172] 113. The term ‘cooling load’ denotes the rate at which heat is transmitted from a refrigerant. (A heat sink may be a refrigerant.)

[00173] 114. The term ‘environment’, where the subject is an airtight configuration, denotes the one or more contiguous and/or remote material substances which surround an airtight configuration, and which collectively determine the temperature to which the airtight configuration's refrigerant tends while the refrigerant's circulation is zero around all of the one or more refrigerant circuits of the airtight configuration's principal configuration. For example, in most applications where an airtight configuration is located inside a building, the airtight configuration's environment is the air inside that building in direct contact with the airtight configuration; and the walls, ceiling, and floor, with which the airtight configuration exchanges heat. And, in the case where the airtight configuration is located in an open space, the airtight configuration's environment is the air in direct contact with the airtight configuration; and the bodies, including celestial bodies, outside the airtight configuration with which the airtight configuration exchanges heat.

[00174] 115. The term ‘controllable element’ in this DESCRIPTION, and synonymously the term ‘controllable means’ in the CLAIMS, denotes an active device which can be controlled by a signal. Examples of controllable elements or means are refrigerant pumps and valves, hot-fluid pumps and valves, cold-fluid pumps and valves, controllers of electric motors or of the burners of a boiler, and electrical switches for starting and stopping internal-combustion engines. A controllable element or means may be a part of a system of the invention, or of another system with which a system of the invention interacts. In either of the two cases cited in the immediately-preceding sentence, a controllable element or means (1) may be controlled exclusively by a system of the invention or only in part by a system of the invention, or (2) may not be controlled by a system of the invention even though it is a part of a system of the invention. The signal cited in this definition 113 includes a signal generated by a transducer which is an integral part of the controllable element or means, as for example in the case where the controllable element is a thermostat.

[00175] 116. The term ‘system-controllable element’ in the DESCRIPTION, and synonymously the term ‘system-controllable means’ in the CLAIMS, denotes a controllable element or means which is controlled at least in part by the system. A system-controllable element or means may be a part of a system of the invention, or of another system with which the system of the invention interacts. Where in this DESCRIPTION it is obvious that a controllable element is a system-controllable element I shall simply refer to a system-controllable element as a ‘controllable element’. Examples of cases where a controllable element is obviously a system-controllable element include the cases where a controllable element is described as being controlled, or is shown in the FIGURES as being controlled, by a signal supplied by a central control unit, or by a minimum-pressure-maintenance control unit, of the system.

[00176] 117. In the context of a system of the invention, (1) the term ‘control mode’ denotes a set of one or more preselected rules for controlling one or more system-controllable elements or means, the set of one or more preselected rules including a single rule for controlling each system-controllable element or means in a pre-prescribed way as a function of one or more preselected characterizing parameters; (2) the expression ‘has several control modes’ denotes the system includes means for executing each of the several control modes; and (3) the expression ‘is in a control mode’ denotes the system is executing a control mode. ‘A preselected rule’ may be an instruction stored in a control unit; or may be, as for example in the case of a thermostat, a rule inherent in the design of a system-controllable element or means. In the context of a system of the invention having several control modes and in the context of a recited system action, the expression ‘in at least one of several control modes’ denotes the system executes the recited action in at least one of the system's one or more control modes. The term ‘control mode’ may include a set of one or more rules requiring none of the one or more system-controllable elements or means to be controlled by the system.

[00177] 118. In the context of a system of the invention (1) the term ‘transition rule’ denotes a set of one or more preselected rules for changing from one of the system's several control modes to another of the system's several control modes; and (2) the expression ‘has several transition rules’ denotes the system includes means for executing each of the several transition rules. The term ‘transition rule’ may include a set of one or more preselected rules for changing (1) from a control mode where none of the the one or more system-controllable elements or means is controlled by the system to another control mode where at least one of the one or more system-controllable elements or means is controlled by the system; and (2) from a control mode where at least one of the one or more system-controllable elements or means is controlled by the system to a control mode where none of the system-controllable elements or means is controlled by the system.

[00178] 119. The term ‘system-control means’, in the CLAIMS, denotes the devices employed to control the system-controllable elements or means of a system of the invention, and subsumes, where applicable, a central control unit, a minimum-pressure-maintenance control unit, one or more transducers, and the means used to control the one or more system-controllable elements or means of the system. Where a system-controllable element or means of a system of the invention is controlled by a transducer and an actuator which are an integral part of the system-controllable element or means, the transducer and the actuator of the system-controllable means are a part of the system-control means of the system to which the system-controllable means belongs. An example of a system-controllable element or means having its own transducer and actuator is a thermostatically-controlled valve.

[00179] 120. The term ‘and/or’ denotes, as applicable, that two or more material things referred to may be, or may not be, located in the selfsame structure; or that two or more events, or two or more actions, referred to may occur, or may not occur, simultaneously.

[00180] 121. The term ‘major paragraph’ denotes text in this DESCRIPTION between a heading and a horizontal line consisting of dashes, or text between two horizontal lines consisting of dashes.

[00181] 122. The term ‘minor paragraph’ denotes in this DESCRIPTION a subparagraph within a major paragraph.

[00182] 123. The term ‘one or more airtight refrigerant circuits’ denotes a set of one or more refrigerant circuits which ingest essentially no ambient air after they have been charged with refrigerant.

[00183] 124. The phrase ‘an airtight configuration having an enclosure’ denotes that an airtight configuration has a refrigerant enclosure (see definition 27) or an R&IG enclosure (see definition 82).

[00184] 125. The phrases ‘inside an airtight configuration’ and ‘inside the airtight configuration’ are abbreviations for respectively the phrases ‘inside the enclosure of an airtight configuration’ and ‘inside the enclosure of the airtight configuration’.

[00185] 126. The term ‘refrigerant-circuit configuration’ is in essence synonymous with the term ‘refrigerant principal configuration’. The only difference between the last two terms is that the former term is used where a system of the invention has no supplementary-configuration means (see definition 87) fluidly connected to a refrigerant-circuit configuration, whereas the latter term is used to denote a refrigerant-circuit configuration of a system of the invention fluidly connected to supplementary-configuration means.

[00186] 127. The term ‘evacuated refrigerant-circuit configuration’ denotes a refrigerant-circuit configuration having a refrigerant enclosure

• [00187] (a) from which essentially all air has been removed;
• [00188] (b) from which, after the enclosure has been charged with the appropriate amount of refrigerant mass, essentially no refrigerant escapes (except in the case of failure); and
• [00189] (c) into which, after the enclosure has been charged with the appropriate amount of refrigerant mass, essentially no air enters (except in the case of failure) either because
  • [00190] (1) the pressure of the refrigerant in the enclosure always stays above ambient atmospheric pressure, or because
  • [00191] (2) the enclosure is made of airtight components joined together so that essentially no air can enter into the enclosure even when the pressure of the refrigerant in the enclosure is below ambient atmospheric pressure.
    The term ‘evacuated refrigerant circuit’ may, where desired, be used to emphasize that a refrigerant circuit belongs to an evacuated refrigerant-circuit configuration. The qualifier ‘essentially’ used under (a) above in the present definition signifies that the amount of air remaining in the enclosure of an evacuated refrigerant-circuit configuration, after “essentially all air is removed”, is small enough for the remaining air not to affect adversely significantly the performance of the evacuated refrigerant-circuit configuration. Essentially all air may be removed from the enclosure of a refrigerant-circuit configuration by using any known method and means. For example, air may be removed by a vacuum pump or by flushing air out of the enclosure with a gas. The qualifier ‘essentially’ used under (b) above in the present definition signifies that the rates at which refrigerant escapes—including during occasional purges of non-condensable gases—from the enclosure of a correctly constructed evacuated refrigerant-circuit configuration are low enough for self-regulation to be achieved, without the need for make-up refrigerant, for typically several years after the time at which the enclosure was charged with an appropriate amount of refrigerant mass. And the qualifier ‘essentially’ used under (c) above in the present definition signifies that the rates at which air enters the enclosure of a correctly constructed evacuated refrigerant-circuit configuration are low enough for the resulting increase in the amount of air contained in the enclosure not to affect adversely significantly the performance of the configuration for typically several years after the time at which the enclosure was charged with an appropriate amount of refrigerant mass.

[00193] 128. The term ‘evacuated configuration’ denotes an airtight refrigerant configuration, or an evacuated refrigerant-circuit configuration.

[00194] 129. The term ‘active’, where used to indicate the state of an evacuated configuration, denotes that refrigerant is circulating at a significant rate around at least one of the evacuated configuration's refrigerant circuits.

[00195] 130. The term ‘inactive’, where used to indicate the state of an evacuated configuration, denotes that refrigerant is circulating at a significant rate around none of the evacuated configuration's one or more refrigerant circuits.

[00196] A first general purpose of the invention is to devise airtight configurations (see definitions) and control techniques for endowing airtight two-phase heat-transfer systems with a property named ‘minimum-pressure maintenance’. This property ensures, broadly speaking, that the pressure inside an entire airtight configuration, or inside a part of an airtight configuration, is maintained at or above a preselected minimum pressure, higher than the refrigerant's lowest saturated-vapor pressure while the airtight configuration's principal configuration is inactive and while the airtight configuration is in thermal equilibrium with its environment. For example, in the case where an airtight configuration's lowest thermal equilibrium temperature with its environment is 0° C. while it is inactive, and where the configuration's refrigerant is water, the refrigerant's lowest saturated-vapor pressure is 0.61 kPa, and the preselected minimum pressure would be higher than 0.61 kPa. (0.61 kPa is the saturated-vapor pressure of water corresponding to 0° C.) I distinguish, as explained in section III,D, between ‘complete minimum-pressure maintenance’ and ‘partial minimum-pressure maintenance’.

[00197] A second general purpose of the invention is to devise airtight configurations and control techniques for endowing airtight configurations with one or more of the properties named ‘freeze protection’, ‘self regulation’, ‘refrigerant-controlled heat release’, ‘gas-controlled heat release’, ‘refrigerant-controlled heat absorption’, and ‘evaporator liquid-refrigerant injection’; and to devise evacuated configurations and control techniques for endowing evacuated configurations with the property named ‘evaporator liquid-refrigerant injection’.

[00198] Other important purposes of the invention will be disclosed later in this DESCRIPTION.

[00199] The eight properties cited in this section III,B are disclosed and discussed in sections III,D to III,H. I note that the three properties named ‘complete minimum-pressure maintenance’, ‘partial minimum-pressure maintenance’, and ‘freeze protection’, pertain to airtight configurations while their principal configuration is inactive. The other five of the eight properties cited in this section pertain to airtight configurations while their principal configuration is active.

[00200] The invention disclosed in this DESCRIPTION covers two-phase heat-transfer systems that include an airtight configuration, or an evacuated configuration, and associated control system for transferring heat from one or more heat sources to one or more heat sinks and for achieving at least one of the eight properties cited in section III,B. The term ‘two-phase heat-transfer systems includes ‘two-phase heat-transfer heating systems’ and ‘two-phase heat-transfer cooling systems’ where the qualifiers ‘heating’ and ‘cooling’ indicate the primary purpose of a two-phase heat-transfer system. I shall, in this DESCRIPTION, use the terms ‘two-phase heating systems’ and ‘two-phase cooling systems’ as abbreviations for respectively the terms ‘two-phase heat-transfer heating systems’ and ‘two-phase heat-transfer cooling systems’. It follows that the two last-cited abbreviations do not include heat pumps and refrigerators.

[00201] The airtight configurations used in systems of the invention are combinations of

• [00202] (a) a principal configuration and an ancillary configuration, and no IG or IGP configuration {see definitions (40), (69), (79), and (80)};
• [00203] (b) a principal configuration, an ancillary configuration, and an IG or an IGP configuration; or
• [00204] (c) a principal configuration and an IG or an IGP configuration, and no ancillary configuration.

[00205] I shall refer to the combination specified under (a) (in the immediately-preceding minor paragraph) as a ‘type A combination’; to the combination specified under (b) as a ‘type B combination’; and to the combination specified under (c) as a ‘type C combination’.

[00206] All airtight configurations of the invention have, by definition, only a single principal configuration. However type A combinations may have one or more ancillary configurations; type B combinations may have one or more ancillary configurations and one or more IG or IGP configurations; and type C combinations may have one or more IG or IGP configurations.

[00207] Many systems of the invention, in addition to including one or more airtight configurations, also include the parts of other material structures cooperating with the airtight configurations to achieve at least one or more of the eight properties recited in section III,B. Those parts include control units and components (including their associated supporting structures) cooperating with the one or more airtight configurations. Examples of such cooperative components include equipment generating certain heat sources, such as the burners of boilers, hot-fluid pumps such as the burners' blowers, and cold-fluid pumps such as the fans of fan-coil units and the radiators of internal-combustion-engines.

[00208] An airtight configuration of the invention, or an evacuated configuration of the invention, has one or more hot heat exchangers and one or more cold heat exchangers. I shall refer to the heat source from which the refrigerant in (the one or more refrigerant passages of) a hot heat exchanger absorbs heat as the ‘hot heat exchanger's heat source’; and, where the heat exchanger is an evaporator, a preheater, or a superheater, I shall refer to the heat source as the ‘evaporator's heat source’, as the ‘preheater's heat source’, or as the ‘superheater's heat source’, respectively. And I shall refer to the heat sink to which the refrigerant in (the one or more refrigerant passages of) a cold heat exchanger releases heat as the ‘cold heat exchanger's heat sink’; and where the heat exchanger is a condenser, a subcooler, or a desuperheater, I shall refer to the heat sink as the ‘condenser's heat sink’, as the ‘subcooler's heat sink’, or as the ‘desuperheater's heat sink’, respectively. The hot heat exchangers of an airtight configuration of the invention may have the same heat source or different heat sources; and similarly the cold heat exchangers of an airtight configuration of the invention may have the same heat sink or different heat sinks.

[00209] All hot heat exchangers of an airtight configuration of the invention have, by definition, one or more refrigerant passages wherein the refrigerant absorbs heat, released by the hot heat exchanger's heat source, while the airtight configuration to which the hot heat exchanger belongs has an active principal configuration. And all cold heat exchangers of an airtight configuration have one or more refrigerant passages wherein the refrigerant releases heat, absorbed by the cold heat exchanger's heat sink, while the airtight configuration to which the cold heat exchanger belongs has an active principal configuration.

[00210] In applications where the heat source of a hot heat exchanger is a hot fluid which is at least in part in direct contact with the walls of the hot heat exchanger's (one or more) refrigerant passages, the hot heat exchanger usually has one or more surfaces which bound one or more enclosed spaces or one or more open spaces, named ‘fluid ways’, to which the hot fluid—while the airtight configuration to which the hot heat exchanger belongs is active—releases heat absorbed by refrigerant in the hot heat exchanger's refrigerant passages. Similarly, in applications where the heat sink of a cold heat exchanger is a cold fluid which is at least in part in direct contact with the walls of the cold heat exchanger's (one or more) refrigerant passages, the cold heat exchanger usually has one or more surfaces which bound one or more enclosed spaces or one or more open spaces, named ‘fluid ways’, from which the cold fluid—while the airtight configuration to which the cold heat exchanger belongs is active—absorbs heat released by refrigerant in the cold heat exchanger's refrigerant passages. Examples of enclosed spaces, in the sense intended by me, are the space inside a tube or inside a rectangular duct; the space inside an annulus formed by concentric tubes; the space between the internal surface(s) of an open or a closed cylinder and the external surfaces of several interconnected tubes inside the cylinder; and the space between the internal surface(s) of an open or a closed rectangular duct and the external surfaces of several rectangular ducts inside the rectangular duct. And examples of open spaces, in the sense intended by me, are the space inside a building or the space inside a room of a building, the space outside a building, the space inside a water reservoir, and the space occupied by a lake.

[00211] A heat source of a hot heat exchanger of an airtight configuration of the invention is always also a heat source of the airtight configuration, or more specifically of the airtight configuration's principal configuration; and a heat sink of a cold heat exchanger of the airtight configuration is always also a heat sink of the airtight configuration, or more specifically of the airtight configuration's principal configuration. Thus the set of one or more heat sources of an airtight configuration of the invention, or equivalently of the airtight configuration's principal configuration, is the set of the one or more heat sources of the airtight configuration's one or more hot heat exchangers; and the set of one or more heat sinks of the airtight configuration, or equivalently of the airtight configuration's principal configuration, is the set of the one or more heat sinks of the airtight configuration's one or more cold heat exchangers.

[00212] The heat source of a hot heat exchanger may be a material substance remote from the hot heat exchanger. Examples of remote heat sources are the sun, flames, and high-temperature metal slabs and rods not in contact with the refrigerant passages of the hot heat exchanger. The heat source may also be a material substance at least in part contiguous to, or in the fluid ways of, a hot heat exchanger. Examples of the latter heat source include

• [00213] (a) material substances with a finite thermal capacity which release heat without changing phase, such as (1) the combustion gas of a fossil fuel, including the combustion gas of an internal combustion engine and the combustion gas of a boiler or a furnace, (2) the gas generated during an exothermic industrial process in a furnace, (3) the flue gas of a steam boiler, hot water boiler, or a hot air furnace, (4) the exhaust gas of a gas turbine, (5) the fluid (gas or liquid) used in an industrial process, and (6) a solid being cooled;
• [00214] (b) material substances with a finite thermal capacity which release heat at least in part while changing phase, such as (1) the working fluid in a steam engine's condenser, and (2) a salt used to store heat;
• [00215] (c) a nuclear fuel generating heat by fission or fusion;
• [00216] (d) electrical and electronic equipment such as (1) electric heating elements, (2) the windings of an electric motor or of an electric generator, (3) electronic equipment, and (4) transformers;
• [00217] (e) infrared and photovoltaic arrays and radio-active isotope generators;
• [00218] (f) material substances having a quasi-infinite thermal capacity, such as the earth's atmosphere, the sea, a large lake, a large water reservoir, or a large geothermal heat source.

[00219] The heat sink of a cold heat exchanger may be, for example, a material substance, such as an extra-terrestrial body or a terrestrial body (such as the wall of a room) remote from the system: or it may be a material substance, at least in part, contiguous to or in the fluid ways of the cold heat exchanger. Examples of the latter heat sink include

• [00220] (a) material substances with a finite thermal capacity which absorb heat without changing phase, such as
  • [00221] (1) the fossil fuel or combustion air supplied to a boiler, a furnace or a gas turbine,
  • [00222] (2) hot water or hot air supplied to an industrial process or used to heat a building,
  • [00223] (3) material, used in an industrial process, which is undergoing an endothermic reaction,
  • [00224] (4) a solid being heated;
• [00225] (b) material substances with a finite thermal capacity which absorb heat at least in part while changing phase, such as
  • [00226] (1) water in a steam boiler,
  • [00227] (2) a salt used to store heat,
  • [00228] (3) H₂O coming out of solution in the generator of a lithium-bromide refrigeration absorption system;
• [00229] (c) material substances having a quasi-infinite thermal capacity, such as the earth's atmosphere, the sea, a large lake, or a large water reservoir.

[00230] Heat may be transmitted from a hot heat exchanger's heat source to refrigerant in the hot heat exchanger, and from refrigerant in a cold heat exchanger to the cold heat exchanger's heat sink, by radiation, convection, or conduction, or by a combination of any two, or of all three, of the foregoing heat-transmittal mechanisms. For example, in the case where the heat source is the sun and the one or more refrigerant passages of a hot heat exchanger are made of glass transparent to thermal radiation, heat is transmitted from the heat source to the refrigerant in the hot heat exchanger essentially only by radiation; and, in the case where the heat source is the flame and combustion gas in a fired steam boiler (having refrigerant passages exposed to radiation from the flame), heat is transmitted from the heat source to the refrigerant in the boiler by radiation, convection, and conduction.

[00231] Airtight configurations, or evacuated configurations, of the invention not only include configurations employing a refrigerant whose refrigerant pressure is below ambient atmospheric pressure while they are inactive, but also configurations employing a refrigerant whose pressure stays below ambient atmospheric pressure while they are active. In particular, airtight refrigerant configurations of the invention include airtight refrigerant configurations, employing H₂O as their refrigerant, that operate exclusively at subatmospheric pressures. Such configurations, in contrast to non-airtight refrigerant configurations employing H₂O as their refrigerant, need no vacuum pump to operate at sub-atmospheric pressures.

[00232] The refrigerant used in an airtight configuration, or an evacuated configuration, of the invention may be, in principle, any fluid whose liquid and vapor phases can coexist over the entire range of operating refrigerant evaporation temperatures of interest in the particular application considered. The phrase ‘any fluid’ is intended to include not only single-component fluids, and (multi-component) azeotropic fluids, which evaporate at a single (sensible) temperature at a given pressure, but also (multi-component) non-azeotropic fluids which evaporate over a range of temperatures at a given pressure.

[00233] Examples of single-component or azeotropic refrigerants which are in principle suitable for the systems of the present invention include refrigerants suitable for heat pipes, tube thermo-siphons, loop thermosiphons, and heat pumps.

[00234] A partial list of single-component and azeotropic refrigerants which have been considered for, or used in, heat pipes and heat pumps is given respectively in P. D. Dunn and D. A. Reay, ‘Heat Pipes’, 2nd Edition, published 1969 by Pergamon Press (London), see page 293; and ‘Thermodynamic Properties of Refrigerants’, published 1969 by ASHRAE (New York), see Table of Contents. And a partial list of non-azeotropic, non-aqueous refrigerants which have been considered for heat pumps is given in a paper by Prof. Thore Bentsson and Dr. Hans Schnitzer, ‘Some Technical Aspects on Nonazeotropic Mixtures as Working Fluids’, presented in September 1984 at the International Symposium on ‘The Large Scale Applications of Heat Pumps’ organized and sponsored by BHRA, The Fluid Engineering Centre, Cranfield, Bedford, England. In addition to the fluids listed in the papers cited in this minor paragraph, a number of non-azeotropic aqueous refrigerants are in principle suitable for the systems of the present invention. These include aqueous solutions of glycol, ethanol, methanol, or acetone. Some of the foregoing azeotropic-like refrigerants—such as chlorofluorocarbons—are no longer acceptable, but I envisage the evacuated configurations of the invention employing acceptable substitutes such as Isceon 69S.

[00235] In practice, the usefulness of a refrigerant for a given application is limited by a number A of constraints. For example, the refrigerant evaporation pressures, and the refrigerant saturated-vapor specific volumes, corresponding to the refrigerant evaporation and condensation temperatures of interest must not be unacceptably high; the refrigerant must not decompose chemically at the highest temperatures which may occur while the system, in which the refrigerant is employed, is active or is inactive; and the cost of the system's refrigerant must not be unacceptably high.

[00236] The materials from which the inside surfaces of the walls of the refrigerant passages of an airtight configuration, or an evacuated configuration, of the invention are made must be compatible with their refrigerant. And, where heat-exchanger refrigerant passages of the configuration come into direct contact with a heat source or a heat sink, the materials from which the outside surfaces of the walls of these refrigerant passages are made must also be compatible with the heat source or the heat sink. The term ‘compatible’ is used herein to indicate that the materials from which refrigerant passages are made have no unacceptable adverse effect on the refrigerant, the heat source, or the heat sink; and also, conversely, to indicate that the refrigerant, the heat source, or the heat sink, have no unacceptable adverse effect on the materials from which the walls of refrigerant passages are made.

[00237] A system of the invention having several airtight configurations may use

• [00238] (a) the same kind of refrigerant in all the system's airtight configurations, or
• [00239] (b) different kinds of refrigerants in each of the system's airtight configurations;
  and may have
• [00241] (a) the same set of one or more heat sources, or the same set of one or more heat sinks, or both, for all the system's airtight configurations, or
• [00242] (b) different sets of one or more heat sources, or different sets of one or more heat sinks, or both, for each of the system's airtight configurations.
  Furthermore, a heat source of an airtight configuration of a system of the invention may be the refrigerant of another airtight configuration of the same system; and a heat sink of an airtight configuration of a system of the invention may be the refrigerant of another airtight configuration of the same system.

[00244] The systems of the invention may be used in a land vehicle, a surface vehicle, a submerged vehicle, or an airborne vehicle—as well as in a fixed ground installation—provided these systems are not required to operate efficiently whilst the vehicle in which they are installed is undergoing a steady-state acceleration having a substantial component normal to the local gravitational field or a substantial component parallel and opposite to this field. What constitutes a ‘substantial’ component depends on the particular system considered, but a component, to be substantial, might often have to be as large as 0.5 g, 0.75 g, or even larger.

[00245] Systems of the invention comprise systems having a heat source controlled in part or entirely by them as well as a heat source not controlled by them. The equipment associated with the former heat source is usually a part of a system of the invention; whereas the equipment associated with the latter heat source is usually not a part of a system of the invention. Examples of heat sources which are controlled by, and which—together with their associated equipment—are entirely a part of, a system of the invention comprise finite thermal-capacity heat sources such as the combustion gases of a steam boiler of the invention used to heat buildings or to supply heat to industrial processes. And examples of heat sources which are not controlled by a system of the invention include

• [00246] (a) finite thermal-capacity heat sources such as the combustion gases inside the cylinders of an internal-combustion engine or the combustion gases of a conventional steam boiler, and such as the exhaust gases of a gas turbine or a blast furnace, or the flue gases of a conventional steam boiler; and
• [00247] (b) quasi-infinite thermal-capacity heat sources such as the sun and the sea.
  I note that, in the particular case where a system of the invention is used to cool an internal combustion engine, the engine's coolant passages (which constitute the system's evaporator) are a part of the system, although the entire engine is not a part of the system.

[00249] Systems of the invention also comprise systems having a heat sink controlled by them as well as heat sinks not controlled by them. The former heat sink—and its associated equipment—is usually a part of a system of the invention; whereas the latter heat sink—and most or all of its associated equipment—is not a part of a system of the invention.

[heading-00250] 1. General Remarks

[00251] Minimum-pressure maintenance may, as mentioned in section III,B, be complete or partial. The qualifier ‘complete’ denotes that the internal pressure inside an entire airtight configuration always stays at or above a preselected minimum pressure; and the qualifier ‘partial’ denotes that the internal pressure inside only a part of an airtight configuration always stays at or above a preselected minimum pressure. The latter property is useful where only a part of an airtight configuration would be subjected to an unacceptably high net external pressure, or would ingest air, if its internal pressure fell substantially below a preselected minimum pressure. Examples of such a part are an air-cooled condenser which would be subjected to unacceptably high crushing pressures, or a refrigerant pump with mechanical seals through which air would be ingested, if the internal pressure of those parts fell substantially below a preselected minimum pressure above the lowest refrigerant saturated-vapor pressure inside an airtight configuration while the configuration is inactive.

[heading-00252] 2. Type A Combinations

[00253] Complete minimum-pressure maintenance is achieved with type A combinations by

• [00254] (a) filling completely their principal configuration with liquid refrigerant, supplied by its associated ancillary configuration, just before, at the time, or soon after, the principal configuration becomes inactive,
• [00255] (b) keeping their principal configuration filled completely with liquid refrigerant, at an internal pressure no less than a preselected minimum pressure, while the principal configuration remains inactive, and
• [00256] (c) transferring back to the ancillary configuration excess liquid refrigerant just before, at the time, or soon after, the principal configuration becomes active.
  The phrase ‘excess liquid refrigerant’ refers to the amount of liquid refrigerant in the principal configuration in excess of the appropriate amount of liquid refrigerant for achieving preselected requirements, including freeze protection, preselected specific self-regulation conditions, preselected heat-release control conditions, or preselected heat-absorption control conditions.

[00258] Partial minimum-pressure maintenance is achieved with type A combinations by

• [00259] (a) isolating with two or more closed refrigerant valves one or more refrigerant-circuit segments of their principal configuration just before, at the time, or soon after, the principal configuration becomes inactive;
• [00260] (b) filling completely the one or more refrigerant-circuit isolated segments with liquid refrigerant, and keeping them filled with liquid refrigerant at an internal pressure no less than a preselected minimum pressure while the principal configuration remains inactive; and
• [00261] (c) opening the one or more refrigerant valves just before, at the time, or soon after, the principal configuration becomes active and removing the amount of liquid refrigerant in the principal configuration in excess of the appropriate amount of liquid refrigerant for achieving, as applicable, preselected specific self-regulation conditions, preselected heat-release conditions, or preselected heat-absorption conditions.
  3. Type B and C Combinations

[00263] Complete minimum-pressure maintenance is achieved with type B and C combinations by

• [00264] (a) inserting in their principal configuration (essentially) inert gas, supplied by its associated IG or IGP configuration, just before, at the time, or soon after, the principal configuration becomes inactive,
• [00265] (b) keeping enough inert gas in the principal configuration to ensure the configuration's internal pressure does not fall below a preselected minimum pressure while the configuration remains inactive, and
• [00266] (c) transferring back to the IG or to the IGP configuration essentially all or a part of the inert gas in the principal configuration just before, at the time, or soon after, the principal configuration becomes active.

[00267] Partial minimum-pressure maintenance is achieved with type C combinations by

• [00268] (a) isolating with two or more closed refrigerant valves one or more refrigerant-circuit segments of their principal configuration just before, at the time, or soon after, the principal configuration becomes inactive;
• [00269] (b) inserting enough inert gas in the one or more isolated refrigerant-circuit segments to ensure the one or more segments' internal refrigerant pressure does not fall below a preselected minimum pressure while the configuration remains inactive; and
• [00270] (c) transferring back to the IG or to the IGP configuration essentially all the inert gas in the principal configuration just before, at the time, or soon after, the principal configuration becomes active.

[00271] Inert-gas transfer between a principal and an IG configuration is controlled primarily by one or more controllable elements of the IG configuration; whereas inert-gas transfer between a principal and an IGP configuration is controlled primarily by the total pressure in the one or more refrigerant circuits of the principal configuration.

[00272] Partial minimum-pressure maintenance is achieved in type B combinations either in the way it is achieved in type A combinations or in the way it is achieved in type C combinations.

[00273] The purpose of freeze protection is to prevent liquid refrigerant freezing in the principal configuration of an airtight configuration while the entire principal configuration, or while one or more parts of the principal configuration, are exposed to refrigerant subfreezing temperatures.

[00274] Freeze protection with a type A or with a type B combination is achieved in essence by

• [00275] (a) using an LR reservoir large enough to store all liquid refrigerant that is located inside the combination's principal configuration, and that could be exposed to refrigerant subfreezing temperatures while the principal configuration is inactive;
• [00276] (b) ensuring the LR reservoir is located in a space whose temperature exceeds the refrigerant's freezing temperature;
• [00277] (c) removing from the principal configuration all liquid refrigerant that could be exposed to refrigerant subfreezing temperatures when or soon after the principal configuration becomes inactive and storing the liquid refrigerant removed in the LR reservoir;
• [00278] (d) preventing, while the principal configuration is inactive, an amount of liquid refrigerant, large enough to cause damage, returning—by gravity, or by diffusion and condensation, or both—from the LR reservoir to the principal configuration; and by
• [00279] (e) transferring from the LR reservoir to the principal configuration, when or soon after the principal configuration becomes active, an amount of liquid refrigerant that ensures the principal configuration contains the appropriate amount of refrigerant mass for the desired operating mode and the prevailing operating conditions.

[00280] I note that the kind of freeze-protection method just outlined differs considerably from the freeze-protection method recited in section III,F of my co-pending U.S. patent application Ser. No. 400,738, filed 30 Aug. 1989: the former method stores liquid refrigerant that could be exposed to subfreezing temperatures outside the principal configuration whereas the latter method stores liquid refrigerant that could thus be exposed inside the principal configuration.

[heading-00281] 1. General Remarks

[00282] Techniques, named ‘self-regulation techniques’ have been devised by me to ensure, broadly speaking, that a principal configuration transfers heat—under pre-prescribed operating conditions—efficiently over the entire range of those operating conditions. I have named the property achieved by using self-regulation techniques ‘self regulation’.

[00283] Self regulation of a principal configuration is achieved by

• [00284] (a) correctly configuring and sizing the configuration,
• [00285] (b) controlling correctly, where applicable, the configuration's one or more refrigerant pumps and also, where applicable, the configuration's one or more refrigerant valves, and by
• [00286] (c) charging the configuration with an appropriate amount of refrigerant mass.
  The self-regulation techniques devised by me for achieving self regulation, with the principal configuration of an airtight configuration, take advantage of the fact that—in contrast to principal configurations of non-airtight principal configurations such as those used in conventional steam-heating systems—no need exists
• [00288] (a) to provide and control the supply of make-up refrigerant to ensure the principal configuration remains charged with an appropriate amount of refrigerant mass, and
• [00289] (b) to provide control techniques for coping with the presence—especially immediately following activation (start-up)—of a significant amount of air in the refrigerant circuits of principal configurations belonging to non-airtight configurations.

[00290] Self regulation of a principal configuration is defined precisely in terms of a preselected set of ‘specific self-regulation conditions’ formulated for a particular heat-transfer application. However, these specific conditions always satisfy collectively, in the case of a principal configuration with an FRC principal circuit, four conditions, named ‘universal self-regulation conditions’, which do not depend on the particular application considered. Only the first three of the four universal self-regulation conditions apply to a principal configuration with an NRC principal circuit. The four universal self-regulation conditions are discussed next.

[heading-00291] 2. Universal Self-regulation Conditions

[00292] The four universal self-regulation conditions require—for a pre-prescribed set of operating conditions—the refrigerant flow, in a principal configuration with a principal refrigerant pump, to be controlled so that, with the principal configuration charged with an appropriate amount of refrigerant mass,

• [00293] (A) the amount of liquid refrigerant, in the one or more refrigerant passages of the configuration's evaporator, is large enough to preclude refrigerant vapor, exiting the one or more evaporator refrigerant passages, being superheated by an amount exceeding a preselected superheat upper limit which can be chosen to be in essence equal to zero;
• [00294] (B) refrigerant vapor, entering the one or more refrigerant passages of the configuration's condenser, has a quality above or equal to a preselected lower limit which may be chosen in essence equal to unity;
• [00295] (C) the amount of liquid refrigerant, backing-up into the one or more condenser refrigerant passages, is small enough to preclude the area of the one or more condenser refrigerant-side heat-transfer surfaces, flooded by the backing-up liquid refrigerant, exceeding a preselected flood upper limit which may be chosen equal to zero, and
• [00296] (D) the configuration's principal-circulation pump has an available net positive suction head high enough to preclude it cavitating significantly.
  I note that the term ‘essentially dry’ in the second self-regulation condition denotes that the amount of liquid refrigerant entering the condenser's refrigerant passages is not large enough to degrade the condenser's performance significantly, but does not preclude the amount of liquid refrigerant in the refrigerant vapor being detectable by known means. I also note that the third self-regulation condition is in essence equivalent to requiring that the amount of liquid refrigerant backing-up into the one or more condenser refrigerant passages be small enough to preclude liquid refrigerant, exiting the one or more condenser refrigerant passages, being subcooled—as a result of the liquid refrigerant back-up—by an amount exceeding a preselected subcool upper limit which may be chosen in essence equal to zero.

[00298] I shall refer individually to the four universal self-regulation conditions just recited as ‘self-regulation conditions (A), (B), (C), and (D)’, respectively. And I shall say that a principal configuration with an FRC principal circuit ‘achieves self regulation’, or alternatively ‘is in its self-regulation mode’, when the four self-regulation conditions are satisfied irrespectively of whether all preselected specific self-regulation conditions for that configuration are satisfied. And I shall further say that an airtight configuration ‘achieves self regulation’ or alternatively ‘is in its self-regulation mode’ if the airtight configuration's principal configuration achieves self regulation or is in its self-regulation mode; and that an airtight configuration satisfies a particular self-regulation condition when the airtight configuration's principal configuration satisfies that particular condition.

[00299] The foregoing four conditions, irrespectively of the specific self-regulation conditions selected for a particular heat-transfer application, can be achieved without using a refrigerant-vapor throttling valve; thereby allowing—for the entire pre-prescribed operating conditions—the absolute value of the difference between

• [00300] (a) the pressure of the refrigerant exiting the one or more refrigerant passages of the evaporator, and
• [00301] (b) the pressure of the refrigerant entering the one or more refrigerant passages of the condenser, to be maintained below a pre-selected upper limit having a finite value, including an arbitrarily small finite value. (The absolute value of the last-cited pressure difference can be maintained below an arbitrarily small finite value by using, for the passages through which refrigerant vapor is transferred from the evaporator to the condenser, cross-sectional areas large enough for the total friction-induced pressure drop in these passages to be maintained below that arbitrarily small finite value.)

[00302] I note that self-regulation conditions (A) to (C) can be achieved by principal configurations, having an FRC principal circuit, with far fewer spatial constraints than by principal configurations having an NRC principal circuit. In particular, the former configurations can satisfy self-regulation conditions (A) to (C) with their condenser below as well as above, or at the same height as, their evaporator; whereas the latter configurations cannot satisfy self-regulation conditions (A) to (C) with their condenser below their evaporator, and this makes the latter systems unsuitable for many important applications.

[00303] I also note that a principal configuration having an FRC principal circuit, may often be preferable to a principal configuration having an NRC principal circuit even in applications where the configuration's condenser may be, or is required to be, placed above the configuration's evaporator. Examples of such applications include applications where the condenser of a principal configuration with an NRC principal circuit would have to be placed at an unacceptably-great height—say at a height of over ten meters—above the evaporator of the principal configuration to allow the net refrigerant static head in the NRC principal circuit to overcome the total friction-induced pressure drop around this circuit. (The total friction-induced pressure drop around an NRC principal circuit may be high because the refrigerant mass-flow rate per unit refrigerant passageway cross-sectional area is high in the evaporator refrigerant passages, or in the condenser refrigerant passages, or in both, because of system requirements.)

[heading-00304] 3. Specific Self-regulation Conditions

[00305] Each specific self-regulation condition is expressed in terms of a preselected quantity, named a ‘self-regulation quantity’, and a preselected constraint on the current value of that quantity. This constraint may be expressed in any one of the following four ways:

• [00306] (a) a desired value of the current value of the self-regulation quantity,
• [00307] (b) a desired upper limit and a desired lower limit within which the current value is required to stay,
• [00308] (c) a desired upper limit below which the current value is required to stay, or
• [00309] (d) a desired lower limit above which the current value is required to stay.

[00310] The self-regulation quantities chosen for a set of specific self-regulation conditions may, even in the absence of a refrigerant auxiliary circuit, include

• [00311] (a) the amount Q*₁ by which refrigerant vapor is superheated at a preselected location, along the principal configuration's refrigerant-vapor transfer means; or
• [00312] (b) the amount Q*₂ by which liquid refrigerant is subcooled at a preselected location, along the principal configuration's liquid-refrigerant principal transfer means; or
• [00313] (c) both the specific self-regulation conditions just recited under (a) and (b).
  In the case where a principal configuration has an evaporator refrigerant auxiliary circuit, the self-regulation quantities, chosen from a set of specific self-regulation conditions, may also include the ratio Q*₃ of refrigerant mass-flow rate through the one or more refrigerant passages of the configuration's evaporator to refrigerant mass-flow rate through the one or more refrigerant passages of the configuration's condenser. And, in the case where, for example, the principal configuration also has a subcooler refrigerant auxiliary circuit, the self-regulation quantities chosen for a set of specific self-regulation conditions may further include the ratio Q*₄ of refrigerant mass-flow rate through the one or more refrigerant passages of the configuration's subcooler to refrigerant mass-flow rate through the one or more refrigerant passages of the configuration's condenser. In the former of the last two cases an EO pump would usually be employed, and the specific self-regulation conditions would almost always include a condition requiring the EO pump not to cavitate significantly under pre-prescribed operating conditions. In the latter of the last two cases, an SC pump is used and the specific self-regulation conditions would almost always include a condition requiring the SC pump not to cavitate significantly under pre-prescribed operating conditions.

[00315] The foregoing four specific self-regulation quantities are intended to be only illustrative examples of self-regulation quantities and not to constitute an exhaustive list of these quantities.

[00316] The pre-selected specific self-regulation quantity may be

• [00317] (a) a function of one or more ‘internal characterizing parameters’, namely of one or more of several parameters characterizing an airtight configuration's state;
• [00318] (b) a function of one or more ‘external characterizing parameters’, namely of one or more of several parameters characterizing an airtight configuration's one or more heat sources, and where applicable associated equipment; an airtight configuration's one or more heat sinks, and where applicable associated equipment; or an airtight configuration's environment; or
• [00319] (c) a function of both one or more internal characterizing parameters and one or more external characterizing parameters.
  And the desired value of, or the desired limits or limit for, a self-regulation quantity may have a preselected fixed value, or may have a value which changes in a pre-prescribed way as a function of one or more preselected characterizing parameters (which need not include the characterizing parameters in terms of which the self-regulation quantity is expressed).

[00321] Internal characterizing parameters are those characterizing the state of a thing which is a part of an airtight configuration. This thing is usually the airtight configuration's enclosure or the airtight configuration's refrigerant. Examples of parameters characterizing an airtight configuration's enclosure are its temperature at a location of the enclosure. And examples of parameters characterizing the state of the refrigerant are

• [00322] (a) a measure of (the height of) the level (with respect to a reference level) of the refrigerant liquid-vapor interface surface in the configuration's receiver or in the configuration's separator; and, where identifiable, in the configuration's evaporator or the configuration's condenser;
• [00323] (b) a measure of refrigerant flow rate at a location in the configuration; and
• [00324] (c) a measure of the refrigerant pressure or refrigerant temperature at a location inside the configuration, or a measure of the change in refrigerant pressure or refrigerant temperature between two separate locations inside the configuration.

[00325] External characterizing parameters are those characterizing the state of a thing which is not a part of an airtight configuration. Examples of things which are not a part of an airtight configuration are a heat source, a heat sink, and ambient air, of the configuration. In applications where a heat source is a fluid, referred to henceforth as a ‘hot fluid’, and a heat sink is also a fluid, referred to henceforth as a ‘cold fluid’, examples of parameters characterizing the hot fluid and the cold fluid are:

• [00326] (a) a measure of the flow rate, temperature, or pressure, of the hot fluid or of the cold fluid at a given location, or equivalently at a given point; and
• [00327] (b) a measure in the change of the flow rate, temperature or pressure, of the hot fluid or of the cold fluid between two different locations, or equivalently between two different points.

[00328] The measures of internal or of external characterizing parameters recited in the immediately-preceding two minor paragraphs may be direct measures or indirect measures.

[heading-00329] Examples of indirect measures are:

[none]

• [00330] (a) The evaporation temperature of an azeotropic-like refrigerant in an airtight configuration is—under steady-state conditions—an indirect measure of the condensation temperature in the airtight configuration in cases where the refrigerant's saturated-vapor temperature drop in the configuration's refrigerant-vapor transfer means is negligible.
• [00331] (b) The (total) refrigerant mass-flow rate through the evaporator refrigerant passages of an airtight configuration, with no evaporator refrigerant auxiliary circuit, is—under steady-state conditions—an indirect measure of the (total) refrigerant mass-flow rate through the condenser refrigerant passages of the configuration.
• [00332] (c) The speed of a low-slip positive-displacement pump is an indirect measure of the volumetric-flow rate of the liquid flowing through the pump and an indirect measure—albeit sometimes a less accurate one—of the mass-flow rate of the liquid flowing through the pump.

[00333] Most techniques used for satisfying a set of specific self-regulation conditions consist in essence in

• [00334] (a) specifying
  • [00335] (1) the characterizing parameters in terms of which the self-regulation quantity is to be expressed,
  • [00336] (2) the functional relationship between the specified characterizing parameters and the self-regulation quantity, and
  • [00337] (3) the desired value, or the desired limit or limits, as applicable, chosen to constrain the values assumed by the self-regulation quantity; and in
• [00338] (b) providing means for
  • [00339] (1) determining the current values of the preselected characterizing parameters,
  • [00340] (2) computing the current value of the specified self-regulation quantity in terms of the current values of the preselected characterizing parameters in accordance with the pre-prescribed functional relationship,
  • [00341] (3) storing the desired value, or the desired limit or limits, under (a)(3) above (in this minor paragraph) and comparing the current value of the self-regulation quantity with the desired value, or the desired limits or limit, under (a)(3) above; and for
  • [00342] (4) controlling the refrigerant flow so that—within the bounds imposed by internal and external constraints—the current value of the self-regulation quantity tends toward the desired value for this quantity, or tends to assume a current value within the range of current values allowed by the desired limits or limit.

[00343] The choice of a set of specific self-regulation conditions for a particular heat-transfer application depends greatly, but not solely,

• [00344] (a) on pertinent facts about the refrigerant being considered for the application; and
• [00345] (b) on pertinent facts about the one or more heat sources and the one or more heat sinks involved in the application.
  For instance, for the purpose of choosing liquid-refrigerant subcooling requirements for a specific set of self-regulation conditions, pertinent facts about the refrigerant include whether the refrigerant is an azeotropic-like or a non-azeotropic fluid (see definition 1); and pertinent facts about the one or more heat sources and the one or more heat sinks include which of the following five cases apply:
  case (A): a heat source which releases heat while being at a spatially substantially-uniform temperature and a heat sink which absorbs heat while being at a spatially substantially-uniform temperature, the spatially substantially-uniform temperature of the heat sink being, at any given instant in time, below the spatially substantially-uniform temperature of the heat source;
  case (B): a heat source which releases heat while being at a spatially substantially-uniform temperature and a heat sink which absorbs heat while undergoing a significant rise in temperature, the highest temperature of the heat sink being, at any given instant in time below the spatially substantially-uniform temperature of the heat source;
  case (C): a heat source which releases heat while undergoing a significant drop in temperature and a heat sink which absorbs heat while being at a spatially substantially-uniform temperature, the spatially substantially-uniform temperature of the heat sink being, at any given instant in time, below the lowest temperature of the heat source;
  case (D): a heat source which releases heat while undergoing a significant drop in temperature and a heat sink which absorbs heat while undergoing a significant rise in temperature, the highest temperature of the heat sink being, at any given instant in time, below the lowest temperature of the heat source; and
  case (E): a heat source which releases heat while undergoing a significant drop in temperature and a heat sink which absorbs heat while undergoing a significant rise in temperature, the highest temperature of the heat sink being, at any given instant in time, above the lowest temperature of the heat source and below the highest temperature of the heat source.

[00352] Examples of spatially substantially-uniform temperature heat sources are a fluid which releases heat while undergoing a change in phase with no significant pressure drop, and a metal slab being cooled. Examples of a spatially substantially-uniform heat sink are a fluid which absorbs heat while undergoing a change in phase with no significant pressure drop, and a water reservoir, with no significant temperature gradient, within which a cold heat exchanger is immersed. Examples of heat sources which release heat while undergoing a substantial drop in temperature, and of heat sinks which absorb heat while undergoing a substantial rise in temperature, are fluids which respectively release and absorb heat without changing phase at low mass-flow rates.

[heading-00353] 1. Preliminary Remarks

[00354] The rate at which radiant energy is transmitted from a high-temperature refrigerant in cold heat exchanger to remote substances, such as the walls or floors of a building or extraterrestrial bodies, can be changed by a shutter opaque to thermal radiation. This shutter is used to intercept partly, or even totally, thermal radiant energy emitted by the refrigerant itself or by the cold heat exchanger's heat-transfer surfaces. In the former case, the cold heat-exchanger heat-transfer surfaces are transparent to thermal radiant energy and, in the latter case, those heat-transfer surfaces are made of heat-conducting material.

[00355] The rate at which heat is transmitted from a refrigerant in a cold heat exchanger to a contiguous cold fluid can be changed by cold-fluid valves (including dampers or shutters), and/or by cold-fluid pumps. Where the cold fluid absorbs heat without changing phase, the two last-cited devices are used to change the cold fluid's mass-flow rate. And, where the cold fluid absorbs heat by changing from a liquid to a vapor, those two devices are used to change the amount of liquid cold fluid in direct contact with the cold heat exchanger's external heat-transfer surfaces.

[00356] I shall hereinafter use the term ‘externally-controlled heat release’, or more briefly the term ‘EC heat release’, to denote the methods of heat-release control outlined in the immediately-preceding two minor paragraphs. (The qualifier ‘externally-controlled’ refers to the fact that the means used to achieve heat-release control are not a part of an airtight configuration.) The techniques for controlling shutters opaque to thermal radiation, and cold-fluid valves (including dampers or shutters) and pumps, are well known. They shall therefore not be discussed in this DESCRIPTION.

[00357] The rate at which a refrigerant in a cold heat exchanger releases heat to remote substances or to a contiguous cold fluid can—where a cold heat exchanger is a condenser—also be changed by controlling the amount of liquid refrigerant in the condenser's refrigerant passages. I shall hereinafter use the term ‘refrigerant-controlled heat release’, or more briefly ‘RC heat release’, to denote heat-release control achieved by changing the amount of liquid refrigerant in the condenser refrigerant passages of a principal configuration.

[00358] I note that RC heat release is an operating mode of an airtight configuration, and is achieved by controlling the refrigerant of an airtight configuration in a way which differs from the way it would be controlled to achieve self regulation. By contrast, EC heat release is not an operating mode of an airtight configuration and is not achieved by controlling the refrigerant of an airtight configuration. Consequently, self regulation and RC heat release are two mutually exclusive operating modes of a two-phase heat-transfer system; whereas self regulation and EC heat release are not mutually exclusive operating modes of a two-phase heat-transfer system, and can therefore coexist. Furthermore, RC heat release and EC heat release are also not mutually exclusive operating modes of a two-phase heat-transfer system, and can therefore also coexist.

[00359] The rate at which a refrigerant in a cold heat exchanger releases heat to remote substances, or to a contiguous fluid, can—where the cold heat exchanger is a condenser—alternatively be changed by controlling the amount of inert-gas mass in the condenser's refrigerant passages. I shall hereinafter use the term ‘gas-controlled heat release’, or more briefly ‘GC heat release’ to denote heat-release control achieved by changing the amount of inert-gas mass in the condenser refrigerant passages of a principal configuration.

[00360] I note that GC heat-release, in contrast to RC heat release, can coexist with self regulation; and that GC heat release, like RC heat release, can coexist with EC heat release.

[heading-00361] 2. Refrigerant-controlled Heat Release

[00362] The purpose of RC heat release is usually to control the rate at which refrigerant releases heat in the condenser refrigerant passages of a principal configuration at a preselected refrigerant pressure or equivalently, in the case of an azeotropic-like refrigerant, at a preselected refrigerant saturated-vapor temperature. The preselected refrigerant pressure may be fixed or may change in a pre-prescribed way.

[00363] RC heat release is achieved with type A, or with type B, combinations by controlling the amount of liquid refrigerant in the one or more condenser refrigerant passages of their principal configuration in pre-prescribed ways, which fall into three general categories.

[00364] The first general category of RC heat-release techniques achieve heat-release control by satisfying self-regulation condition (B) and violating self-regulation condition (C); namely by supplying a condenser's refrigerant passages with essentially dry refrigerant, and by increasing the amount of liquid refrigerant, backing-up into those passages, above that allowed by self-regulation condition (C).

[00365] The second general category of RC heat-release techniques achieve heat-release control by violating self-regulation condition (B) and satisfying self-regulation condition (C); namely by supplying wet refrigerant vapor to a condenser's refrigerant passages whilst not allowing liquid refrigerant to back-up into those passages by an amount exceeding that allowed by self-regulation condition (C).

[00366] The third general category of RC heat-release techniques achieve heat-release control by violating self-regulation conditions (B) and (C).

[00367] In the particular case where a condenser is a split condenser including several component condensers (see section V,B,12), liquid refrigerant can be inserted into, and extracted from, component condensers independently by using several ancillary configurations or even by using a single ancillary configuration.

[heading-00368] 3. Gas-controlled Heat Release

[00369] Broadly speaking, the purpose of GC heat release is the same as that as RC heat release. However, where GC heat release is used, the preselected pressure at which the rate of heat release is controlled is usually the total pressure of the refrigerant and inert gas. (This total pressure is of course essentially equal to the refrigerant pressure at a point, inside an airtight configuration, where the partial pressure of the inert gas is negligible.)

[00370] GC heat-release is achieved with type B, or with type C, combinations having an IG configuration by transferring inert gas from their IG reservoir to their condenser's refrigerant passages, and from their condenser's refrigerant passages to their IG reservoir, in a pre-prescribed way. Inert gas can be inserted into, or extracted from, those passages through the condenser's refrigerant inlet, through the condenser's refrigerant outlet, or through one or more ports along the condenser's refrigerant passages.

[00371] In the particular case where a condenser is a split condenser including several component condensers, inert gas can be inserted into, or extracted from, component condensers independently by using several IG configurations, or even by using only a single IG configuration.

[heading-00372] 1. Preliminary Remarks

[00373] The rate at which radiant thermal energy is transmitted from a remote high-temperature material substance, such as a flame or the sun, to a refrigerant in a hot heat exchanger can be changed by a shutter opaque to thermal radiation. This shutter is used to intercept partly, or even totally, thermal radiant-energy absorbed by the refrigerant itself or by the hot heat exchanger's heat-transfer surfaces. In the former case, the hot heat exchanger heat-transfer surfaces are transparent to thermal radiation and, in the latter case, those heat-transfer surfaces are made of heat-conducting material.

[00374] The rate at which heat is transmitted from a hot fluid to a contiguous refrigerant in a hot heat exchanger can be changed by hot-fluid valves (including dampers or shutters), and/or by hot-fluid pumps. Where the hot fluid releases heat without changing phase, the two last-cited devices are used to change the hot fluid's mass-flow rate. And, where the hot fluid releases heat by changing from a vapor to a liquid, those two devices are used to change the amount of liquid hot fluid in direct contact with the hot heat exchanger's external heat-transfer surfaces.

[00375] I shall hereinafter use the term ‘externally-controlled heat absorption’, or more briefly the term ‘EC heat absorption’, to denote methods of heat absorption control outlined in the immediately-preceding two minor paragraphs.

[00376] The rate at which a refrigerant in a hot heat exchanger absorbs heat from a remote substance, or from a contiguous hot fluid, can—where the hot heat exchanger is an evaporator—also be changed by controlling the amount of liquid refrigerant in, and/or the refrigerant mass-flow rate through, the evaporator's refrigerant passages. I shall hereinafter use the term ‘refrigerant-controlled heat absorption’, or more briefly the term ‘RC heat absorption’, to denote heat-absorption control recited in the immediately-preceding sentence.

[00377] I note that RC heat absorption—like RC heat release—is an operating mode of an airtight configuration, and is achieved by controlling the refrigerant of an airtight configuration in a way which differs from the way it would be controlled to achieve self regulation. By contrast, EC heat absorption—also like EC heat release—is not achieved by controlling the refrigerant of an airtight configuration. Consequently, self regulation and RC heat absorption—like self regulation and RC heat release—are two mutually-exclusive operating modes of a two-phase heat-transfer system; whereas self regulation and EC heat absorption—also like self regulation and EC heat release—are not mutually-exclusive operating modes of a two-phase heat-transfer system, and can therefore coexist. Furthermore, RC heat absorption and EC heat absorption are not mutually-exclusive operating modes of a two-phase heat-transfer system, and can therefore also coexist.

[heading-00378] 2. Refrigerant-controlled Heat Absorption

[00379] The purpose of RC heat absorption is usually to control the rate at which refrigerant absorbs heat in all, or in a part of, the evaporator refrigerant passages of a principal configuration at a preselected refrigerant saturated-vapor pressure or equivalently, in the case of an azeotropic-like refrigerant, at a preselected refrigerant saturated-vapor temperature. The preselected refrigerant pressure may be fixed or may change in a pre-prescribed way.

[00380] RC heat absorption is achieved with type A, or with type B, configurations by controlling the amount of liquid refrigerant in the one or more evaporator refrigerant passages of their principal configuration in pre-prescribed ways. Pre-prescribed ways for achieving heat absorption often violate self-regulation condition (A); namely they decrease the amount of liquid refrigerant in the evaporator refrigerant passages below that allowed by self-regulation condition (A).

[00381] In the particular case where an evaporator is a split evaporator including several component evaporators (see section V,B,12), liquid refrigerant can be inserted into, and extracted from, component evaporators independently by using several ancillary configurations, or even by using only a single ancillary configuration.

[00382] The purpose of liquid-refrigerant injection is to achieve at least one of several objectives. These objectives include (1) preventing refrigerant vapor being trapped in one or more parts of the evaporator refrigerant passages of a system of the invention, thereby eliminating potential hot spots; (2) increasing the refrigerant's heat-transfer coefficients in the system's evaporator refrigerant passages; and (3) increasing the refrigerant's critical flux in those passages.

[00383] To achieve one or more of the foregoing several objectives, the systems of the invention use liquid-refrigerant injectors, or more briefly LR injectors, to inject liquid refrigerant into the system's evaporator refrigerant passages. LR injectors are usually passive devices having one or more orifices whose total cross-sectional area is smaller than the cross-sectional area of the inlet through which liquid refrigerant is supplied to them. LR injectors achieve their objectives by one or more of several techniques. These techniques include (1) promoting turbulence in evaporator refrigerant passages; (2) distributing liquid refrigerant in preselected vapor spaces inside evaporator refrigerant passages; and (3) distributing liquid refrigerant over preselected internal surfaces of those passages.

[00417] The symbol ‘⊙’ used in certain FIGURES denotes that the signal represented by a letter with one or more superscripts which include a ‘dash’, and with one or more subscripts, is transmitted (1) from a transducer to a control unit, where the arrow associated with the signal points toward the signal, and (2) from a control unit to a control table element or means—such as a pump or a valve—where the arrow associated with the signal points away from the symbol. And a first of the two symbols

[heading-00418] inside the block representing a heat exchanger, represents the one or more refrigerant passages of the heat exchanger; and a second of the two symbols

[heading-00419] inside the block representing a heat exchanger, represents the one or more fluid ways of the heat exchanger.

[00420] Several numerals occur often in the FIGURES. Elements designated by certain of those numerals are listed for convenience below.

[00002]

Numeral	Item
1	generic non-pool evaporator
4	generic condenser
7	2-port condensate receiver
10	condensate-return pump
13	1-port condensate receiver
21	type 1 separator
21*	type 1 separating assembly
27	evaporator-overfeed pump
42	type 2 separator
42*	type 2 separating assembly
46	dual-return pump
63	subcooler-circulation pump
81	generic pool evaporator
113	condensate-receiver proportional liquid-level transducer
125	separator proportional liquid-level transducer
126	pool-evaporator proportional liquid-level transducer
400	refrigerant principal configuration
401	variable-volume liquid refrigerant reservoir
404	liquid-refrigerant transfer pump
420	air-transfer pump
424	fixed volume liquid-refrigerant reservoir
435	bidirectional liquid-transfer valve in parallel with a liquid-
	refrigerant-transfer pump
436	bidirectional liquid-transfer valve in series with a liquid-
	refrigerant-transfer pump
441	variable-volume inert-gas reservoir
443	gas-transfer pump
446	condensate-type refrigerant-vapor trap
453	fixed-volume inert-gas reservoir
475	bidirectional gas-transfer valve in parallel with a gas-transfer
	pump
476	bidirectional gas-transfer valve in series with a gas-transfer
	pump
477	bidirectional drain valve in parallel with a gas-transfer pump
485	proportional two-way gas-transfer valve
486	on-off gas-transfer valve
500	piston engine
502	cylinder block
503	cylinder head
504	cylinder-block coolant (refrigerant) passages
505	cylinder-head coolant (refrigerant) passages
508	air-cooled condenser
510	condenser fan
514	proportional refrigerant absolute-pressure transducer
516	proportional refrigerant-temperature transducer
531	liquid-refrigerant injectors
551	air-cooled subcooler
552	subcooler fan
561	air-heated evaporator
562	intake-air temperature transducer
594	water-cooled condenser
603, 617	principal-configuration proportional absolute-pressure
	transducer
604	two-step engine-wall temperature transducer
605	inert-gas reservoir proportional absolute-pressure transducer
606	inert-gas reservoir gas-temperature transducer
621	pulley-and-clutch
634	proportional engine-wall temperature transducer
640	dual-return receiver

[00421] The optimal number and kind of airtight configurations used in a system of the invention, the desired properties of those configurations, and the particular refrigerant—and where applicable inert-gas—control techniques employed to achieve those properties, depend on the particular heat-transfer application considered. It follows that the best mode for carrying out the invention, namely the preferred embodiment of a system of the invention, depends on the particular heat-transfer application considered.

[00422] In this part (part V) of this DESCRIPTION I first describe principal, ancillary, and IG, configurations suitable for various preferred embodiments of the invention, and then give examples of those embodiments in the context, for specificity, of a particular category of applications. Each of these embodiments is expected to be a preferred embodiment for some specific useful application. The statements made about the principal configurations of airtight configurations apply to the refrigerant-circuit configurations of evacuated configurations.

[00423] All principal configurations include only one refrigerant principal circuit. A refrigerant principal circuit includes, by definition, the one or more refrigerant passages of an evaporator, the one or more refrigerant passages of a condenser, means for transferring refrigerant vapor exiting the one or more refrigerant passages of an evaporator to the one or more refrigerant passages of a condenser, and means for transferring liquid refrigerant exiting the one or more refrigerant passages of a condenser to the one or more refrigerant passages of an evaporator. The refrigerant-vapor transfer means may transfer in part, or even over its entire length, only liquid refrigerant under certain special operating conditions. And the principal configuration may also include refrigerant auxiliary circuits around which only liquid refrigerant circulates.

[00424] Almost all principal configurations of preferred embodiments of the invention can be divided into twelve groups designated by roman numerals I to XII. In grouping principal configurations of the invention, I distinguish between

• [00425] (a) evaporators in which a readily identifiable, essentially-horizontal, refrigerant liquid-vapor undulating interface surface (albeit possibly segmented) exists, and in which pool boiling prevails, for at least most of their operating time during their operating life; and
• [00426] (b) evaporators in which no readily identifiable, essentially horizontal, refrigerant liquid-vapor undulating interface surface exists, and in which forced-convection boiling and two-phase flow prevails, for at least most of their operating time during their operating life.

[00427] I shall hereinafter refer to the former kind of evaporators as ‘pool evaporators’, or more briefly as ‘P evaporators’; and to the latter kind of evaporators as ‘non-pool evaporators’, or more briefly as ‘NP evaporators’.

[00428] Most P evaporators have a single-level liquid-vapor interface surface while they are active as well as while they are inactive. However, P evaporators also include evaporators which have a multi-level liquid-vapor interface surface while they are active. Electrode-type electric steam boilers are examples of P evaporators having a two-level liquid-vapor interface surface while they are active.

[00429] I note that, by definition, group I to VI configurations have NP evaporators and group VII to XII configurations have P evaporators. I also note that NP and P evaporators may have a single, or may have several, bottom, top, or multi-level refrigerant inlet ports, and/or several bottom, top, or multi-level refrigerant outlet ports.

[00430] I further note that, in classifying principal configurations belonging to a given group, I distinguish between configurations having a preheater and those having no preheater, and between configurations having a superheater and those having no superheater, only if the principal configurations have an evaporator refrigerant auxiliary circuit. I therefore, for simplicity, show no preheater and no superheater in FIGURES used in classifying principal configurations and having no evaporator refrigerant auxiliary circuit.

[00431] Examples of known P evaporators are, in the steam-generating industry, fire-tube steam boilers, cast-iron steam boilers, resistance-type electric steam boilers, and electrode-type electric steam generators; and, in the refrigeration industry, flooded shell-and-tube coolers and flooded evaporators. And examples of known NP evaporators are, in the steam-generating industry, water-tube steam boilers and coil-type steam boilers; and in the refrigeration industry, direct-expansion air-cooled evaporators, direct-expansion shell-and-tube coolers, direct-expansion shell-and-coil coolers, tube-in-tube coolers, plate coolers, and Baudelot coolers.

[00432] By contrast with evaporators, I shall not distinguish, in grouping principal configurations, between condensers in which

• [00433] (a) a readily identifiable, essentially horizontal, refrigerant liquid-vapor interface surface exists, and condensers in which
• [00434] (b) no readily identifiable liquid-vapor interface surface exists.
  Examples of known condensers include shell-and-tube condensers, shell-and-coil condensers, tube-in-tube condensers, coil condensers, and evaporative condensers; and may include a section or zone in which liquid refrigerant is subcooled, although subcoolers are usually employed where liquid refrigerant is to be subcooled by a large amount, say over 10° C.

[00436] I note that certain condensers, such as shell-and-tube condensers, in which refrigerant flows through the space between the shell and the tubes, can be used for storing liquid refrigerant without flooding or submerging even part of the condensers’ heat transfer surfaces, and can therefore also perform the function of a 2-port or feed-through receiver, one of the ports of the 2-port receiver being the condensers' horizontal cross-section just below their lowest heat-transfer surface. Thus the receiver (of a principal configuration) may be an integral part of a condenser. I also note that, in classifying principal configurations belonging to the same group, I do not distinguish between principal configurations having a desuperheater and those having no desuperheater. I therefore, for simplicity, show no desuperheater in the FIGURES used in grouping principal configurations.

[heading-00437] 1. Group I Configurations

[00438] The key distinctive characteristic of group I configurations, compared to other groups of configurations with an NP evaporator, is that they have no auxiliary circuit.

[00439] I distinguish between group I configurations having a refrigerant pump and those that have no refrigerant pump; and designate the former subgroup of configurations by the symbol I_F and the latter subgroup of configurations by the symbol I_N, where the subscripts ‘F’ and ‘N’ stand, respectively, for forced refrigerant circulation and natural refrigerant circulation. I also distinguish between group I configurations having a subcooler and group I configurations having no subcooler. However, I do not distinguish between group I configurations having a preheater and those having no preheater (or between group I configurations having a superheater and those having no superheater).

[00440] I use a superscript to indicate the absence or the presence of a subcooler. Thus the symbols I_F^o and I_N^o designate classes of group I configurations with no subcooler and the symbols I_F^s and I_N^s designate classes of group I configurations with a subcooler.

[00441] A class I_F^o configuration, with a 2-port or feed-through receiver, is shown in FIG. 1. NP evaporator 1, hereinafter referred to as evaporator 1, has a refrigerant inlet 2 and a refrigerant outlet 3; condenser 4 has a refrigerant inlet 5 and a refrigerant outlet 6; 2-port condensate receiver 7 has an inlet 8 and an outlet 9; refrigerant pump 10 has an inlet 11 and an outlet 12; and refrigerant circulates around refrigerant principal circuit 2-3-5-6-8-9-11-12-2 primarily under the a 10. A class I_F^o configuration may have a 1-port receiver instead of a 2-port receiver as shown in FIG. 1A, where surge-type receiver 13 has a common inlet and outlet 14 connected to refrigerant line 6-11 at a point 15, and where line 16-17 is merely a pressure equalization line. Class I_N^o configurations read on FIGS. 1 and 1A provided obvious elevation constraints are satisfied. (The constraints, where no receiver is used, require in essence evaporator 1 to be at least no higher than condenser 4; and, where a receiver is used, require in essence evaporator 1 to be at least no higher than, as applicable, receiver 7 or receiver 13.)

[00442] A class I_F^s configuration with a 2-port receiver is shown in FIG. 2. A class I_F^s configuration differs from a class I_F^o configuration by the addition of subcooler 18 having a refrigerant inlet 19 and a refrigerant outlet 20 connected to receiver outlet 9 and refrigerant pump inlet 11, respectively, as shown in FIG. 2. I note that the position of pump 10 and subcooler 18 around the refrigerant principal circuit can be interchanged so that refrigerant inlet 19 of subcooler 18 is connected to refrigerant pump outlet 12, refrigerant outlet 20 of subcooler 18 is connected to evaporator inlet 2, and refrigerant pump inlet 11 is connected to receiver outlet 9. Liquid refrigerant subcooled in subcooler 18 is preheated, before being evaporated, in the refrigerant passages of evaporator 1. Class I_N^s configurations read on FIG. 2 provided obvious elevation constraints are satisfied.

[heading-00443] 2. Group II Configurations

[00444] The key distinctive characteristic of group II configurations, compared to other groups of configurations with an NP evaporator, is that they have a separator and a single refrigerant auxiliary circuit of the kind named a type 1 evaporator refrigerant auxiliary circuit, (and therefore, in particular, have no subcooler refrigerant auxiliary circuit). Group II configurations may have no refrigerant pump, a CR pump, an EO pump, or both a CR pump and an EO pump.

[00445] I distinguish between group II configurations having a refrigerant pump, and those that have no refrigerant pump and are designated by the symbol II_NN. (In the symbol II_NN, the first subscript indicates natural refrigerant circulation around the refrigerant principal circuit, and the second subscript indicates natural refrigerant circulation around their evaporator refrigerant auxiliary circuit.)

[00446] I use the symbol II_FN to designate the subgroup of group II configurations in which the refrigerant circulates around their refrigerant principal circuit primarily under the forced action of a CR pump, and around their evaporator refrigerant auxiliary circuit solely under the combined natural action of gravity and heat absorbed from the evaporator's heat source. I also use the symbol II_FF to designate the subgroup of group II configurations in which their refrigerant circulates around the refrigerant principal circuit primarily under the forced action of a CR pump, and around their evaporator refrigerant auxiliary circuit primarily under the forced action of an EO pump. I further use the symbol II_NF to designate the subgroup of group II configurations in which the refrigerant circulates around the refrigerant principal circuit solely under the combined natural action of gravity and heat absorbed from a heat source, and around the refrigerant auxiliary circuit primarily under the forced action of an EO pump.

[00447] I use a first superscript to indicate the absence or the presence of a subcooler; a second superscript to indicate the presence or absence of a superheater; and a third superscript to indicate the absence or presence of a preheater. In the case of the first superscript, a ‘o’ (zero), an ‘s’, an ‘s′’, and an ‘s″’, indicate that group II configurations, designated by the symbols with these superscripts, have respectively

• [00448] (a) no subcooler;
• [00449] (b) a subcooler which has one or more refrigerant passages that are a part of the refrigerant principal circuit and not a part of the evaporator refrigerant auxiliary circuit;
• [00450] (c) a subcooler which has one or more refrigerant passages that are a part of the evaporator refrigerant principal circuit and not a part of the refrigerant principal circuit; and
• [00451] (d) a first subcooler which has one or more refrigerant passages that are a part of the refrigerant principal circuit and not a part of the evaporator refrigerant auxiliary circuit, and a second subcooler which has one or more refrigerant passages that are a part of the evaporator refrigerant auxiliary circuit and not a part of the evaporator refrigerant principal circuit.
  In the case of the second superscript, a ‘o’ (zero) and an ‘s’ indicate that group II configurations, designated by symbols with these superscripts, have no superheater, and have a superheater, respectively. And in the case of the third superscript, a ‘o’ (zero), a ‘p’, a ‘p′’, and a ‘p″’, indicate that group II configurations, designated by symbols with these superscripts, have respectively
• [00453] (a) no preheater;
• [00454] (b) a preheater having one or more refrigerant passages that are a part of the refrigerant principal circuit and not a part of the evaporator refrigerant auxiliary circuit;
• [00455] (c) a preheater having one or more refrigerant passages that are a part of the evaporator refrigerant principal circuit and not a part of the refrigerant principal circuit; and
• [00456] (d) a first preheater having one or more refrigerant passages that are a part of the refrigerant principal circuit and not a part of the evaporator refrigerant auxiliary circuit, and a second preheater having one or more refrigerant passages that are a part of the evaporator refrigerant auxiliary circuit and not a part of the refrigerant principal circuit.
  Thus each of the four configuration subgroups II_NN, II_FN, II_FF, and II_NF consists of fourteen classes of configurations, each of which is designated by fourteen combinations of superscripts, namely by combinations ooo, soo, s′oo, s″oo, sop, s′op′, s″op″, oso, sso, s′so, s″so, ssp, s′sp, s″sp″; and thus configuration subgroups II_NN, II_FN, II_FF, and II_NF, consist of fifty-six classes. I note that all of the foregoing fifty-six classes may have a 3-port separator, but that only those with no EO pump can have a 4-port separator.

[00458] A class II_FN^ooo configuration with a 3-port (type 1) separator and a 2-port receiver is shown in FIG. 3. Type 1 separator 21 has a vapor inlet 22 connected to evaporator refrigerant outlet 3, vapor outlet 23 connected to condenser refrigerant inlet 5, and liquid port 24 connected to node or mergence point 25 at some point along refrigerant line 12-2. Refrigerant circulates around the refrigerant principal circuit 2-3-22-23-5-6-8-9-11-12-25-2 primarily around the evaporator refrigerant auxiliary circuit 2-3-22-24-25-2 solely under the combined action of gravity and heat absorbed from a heat source (not shown). A class II_FN^ooo configuration with a 4-port (type 1) separator is shown in FIG. 4. In this case, separator 21 has a liquid inlet 26—in addition to vapor inlet 22, vapor outlet 23, and liquid port 24—and refrigerant-pump outlet 12 is connected to liquid inlet 26 instead of to a point along refrigerant line 12-2 as shown in FIG. 3. Whereas the evaporator refrigerant auxiliary circuit in the case of a 4-port separator is—except for the absence of node 25—the same as that for a 3-port separator, the refrigerant principal circuit in the case of a 4-port separator also includes liquid inlet 26 and liquid port 24 so that refrigerant flows (under steady state conditions) primarily under the action of pump 10 around refrigerant principal circuit 2-3-22-23-5-6-8-9-11-12-26-24-2. A class II_FN^ooo configuration with 3-pot separator and a 1-port receiver is shown in FIG. 3A, and a class II_FN^ooo configuration with a 4-port separator and a 1-port receiver is shown in FIG. 4A. A class II_FN^ssp configuration with a 4-port separator is shown in FIG. 5. Class II_FN^ooo configurations read on FIGS. 3A, 4A, 5, and 6, provided obvious elevation constraints are satisfied.

[00459] A class II_NF^ooo configuration with a 3-port separator and a 2-port receiver is shown in FIG. 6. This configuration differs from that shown in FIG. 3 by the absence of CR pump 10 and the addition of EO pump 27. The absence of CR pump 10 requires, for operability, that condenser 4 not be below evaporator 1, whereas the condenser of subgroup II_FN and II_FF configurations can be either above or below their evaporator. Furthermore, the presence of pump 27 imposes additional constraints on the relative elevations of the condenser and the evaporator of subgroup II_NF configurations. Class II_NF^ooo configurations read on FIG. 6.

[00460] A class II_FF^s″sp″ configuration with a 2-port receiver is shown in FIG. 7. Class II_FF^s″sp″ configurations differ from class II_FN^ooo configurations with a 3-port separator by the addition, in the manner shown in FIG. 7, of

• [00461] (a) EO pump 27 having an inlet 28, and an outlet 29;
• [00462] (b) subcooler 18 having a refrigerant inlet 19 and a refrigerant outlet 20;
• [00463] (c) superheater 30 having a refrigerant inlet 31 and a refrigerant outlet 32;
• [00464] (d) subcooler 33 having a refrigerant inlet 34 and a refrigerant outlet 35;
• [00465] (e) preheater 36 having a refrigerant inlet 37 and a refrigerant outlet 38, and
• [00466] (f) preheater 39 having a refrigerant inlet 40 and a refrigerant outlet 41.

[00467] Class II_NN^s″sp″ configurations read on FIG. 7 provided obvious elevation constraints are satisfied.

[00468] I note that, in the refrigerant-circuit configuration shown in FIG. 7, refrigerant flows through subcoolers 18 and 33 before flowing through CR pump 10 and EO pump 27, respectively. However, group II configurations with subcoolers include refrigerant-circuit configurations in which the positions of a subcooler and a refrigerant pump along a refrigerant-circuit segment are interchanged; and, as a result of this, refrigerant flows through the subcooler after flowing through the refrigerant pump instead of flowing through the subcooler before flowing through the refrigerant pump.

[heading-00469] 3. Group III Configurations

[00470] The key distinctive characteristic of group III configurations, compared to other groups of configuration with an NP evaporator, is that they have a separator and a single refrigerant auxiliary circuit of the kind named a type 2 evaporator refrigerant auxiliary circuit, (and therefore, in particular, have no subcooler refrigerant auxiliary circuit). Group III configurations have a DR pump only, or a DR pump and a CR pump.

[00471] I use the symbol III_FN to designate group III configurations having no CR pump, and the symbol III_FF to designate group III configurations having a CR pump.

[00472] I distinguish between four classes of subgroup III_FN configurations, and use the symbols III_FN^oo, III_FN^so, III_FN^os, and III_FN^ss, to designate these four classes. In the last four symbols, the subscript F is used to indicate that refrigerant circulates around both the refrigerant principal circuit, and around the evaporator refrigerant auxiliary circuit, under the forced action of a DR pump; and the first and second superscripts are used to indicate the absence or presence of a subcooler and a superheater, respectively. I also distinguish between type 2 separators used in group III configurations and type 1 separators used in group II configurations because the former separators perform a significantly different function from the latter; and can, in particular, also perform the function of a receiver. However, I do not distinguish between subgroup III_FN configurations having a preheater and those having no preheater.

[00473] A class III_FN^ooo configuration with a 3-port (type 2) separator and no separate receiver is shown in FIG. 8. Type 2 separator 42 has a vapor inlet 43 connected to evaporator refrigerant outlet 3, a vapor outlet 44 connected to condenser refrigerant inlet 5, and a liquid outlet 45. DR pump 46 has an inlet 47 connected to condenser refrigerant outlet 6 and an outlet 48 connected to evaporator refrigerant inlet 2; and separator liquid outlet 45 is connected to refrigerant line 6-47 at point 49. Refrigerant circulates around refrigerant principal circuit 2-3-43-44-5-6-49-47 around evaporator refrigerant auxiliary circuit 2-3-43-45-49-47-48-2, primarily under the force action of DR pump 46. A class III_FN^ooo configuration with a 4-port separator having a liquid inlet 50 is shown in FIG. 8A.

[00474] A class III_FN^ss configuration with a 3-port separator and no separate receiver is shown in FIG. 9. A class III_FN^ss configuration differs from a class III_FN^oo configuration by the addition of subcooler 51, with refrigerant inlet 52 and refrigerant outlet 53, and of superheater 54 with refrigerant inlet 55 and refrigerant outlet 56. A class III_FN^oo configuration is obtained by deleting in FIG. 9 superheater 54; and a class III_FN^oo configuration is obtained by deleting in FIG. 9 subcooler 51.

[00475] I note that, in the class III_FN^ss configuration shown in FIG. 9, the refrigerant flows through subcooler 51 before flowing through pump 46. However, class III_FN^ss configurations, as well as class III_FN^so configurations, also include configurations in which the positions, around the refrigerant principal circuit, of DR pump 46 and subcooler 51 are interchanged so that DR pump 46 is located between node or mergence point 49 and subcooler 51, and so that subcooler refrigerant outlet 53 is connected to evaporator refrigerant inlet 2. I also note that, although no receiver has been shown in FIGS. 8, 8A, and 9, subgroup III_FN configurations may also sometimes have either a 1-port receiver or a 2-port receiver.

[00476] A class III_FF^ss configuration with a 3-port separator and a receiver is shown in FIG. 9A. Class III_FF^so configurations are obtained from FIGS. 9 and 9A by deleting superheater 54; class III_FF^os configurations are obtained from the two last-cited FIGURES by deleting subcooler 51; and class III_FF^oo configurations are obtained from the two last-cited FIGURES by deleting subcooler 51 and superheater 54.

[heading-00477] 4. Group IV Configurations

[00478] The key distinctive characteristic of group IV configurations, compared to other groups of configurations with an NP evaporator, is that they have a single refrigerant auxiliary circuit of the kind named a subcooler refrigerant auxiliary circuit which, by definition, always includes the one or more refrigerant passages of a subcooler, and the one or more refrigerant passages of a pump, and which may also include the one or more refrigerant passages of a preheater; but which always excludes the one or more refrigerant passages of an evaporator, and the one or more refrigerant passages of a condenser. Broadly speaking, group IV configurations are combinations of a group I configuration with a subcooler refrigerant auxiliary circuit.

[00479] I use the symbols IV_FF, IV_FF*, IV_F*F, and IV_NF, where the subscript ‘_F*’ denotes the presence of an HF pump, to designate subgroups of group IV configurations with respectively

• [00480] (a) a CR pump and an SC pump,
• [00481] (b) a CR pump and an HF pump,
• [00482] (c) an HF pump and an SC pump, and
• [00483] (d) an SC pump and no CR or HF pump.
  I use a superscript to indicate the absence or presence of a subcooler, other than a subcooler having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit: a ‘o’ (zero) and an ‘s’ indicate respectively the absence and presence of such a subcooler.

[00485] A class IV_FF^s configuration with a 2-port receiver is shown in FIG. 10. Subcooler 57 has a refrigerant inlet 58 and a refrigerant outlet 59; preheater 60 has a refrigerant inlet 61 and a refrigerant outlet 62; and refrigerant circulates, under the forced action of SC pump 63, around subcooler refrigerant auxiliary circuit 66-58-59-61-62-67-64-65-66, where 64 and 65 are the inlet and outlet, respectively, of SC pump 63, and where node 66 is located along the refrigerant line connecting CR pump outlet 12 to subcooler refrigerant inlet 58, and where node 67 is located along the refrigerant line connecting preheater refrigerant outlet 62 to evaporator refrigerant inlet 2. A class IV_FF^s configuration can be looked at as a class I_F^s configuration to which has been added a subcooler refrigerant auxiliary circuit whose subcooler and preheater refrigerant passages are a part of the configuration's refrigerant principal circuit.

[00486] A class IV_FF^o configuration is obtained by deleting subcooler 18 from a class IV_FF^s configuration; and class IV_NF^s and IV_NF^o configurations are obtained by deleting SC pump 63 from respectively class IV_FF^s and IV_FF^o configurations.

[00487] A subgroup IV_FF* configuration differs from a subgroup IV_FF configuration in that SC pump 63 is replaced, in the manner shown in FIG. 10A, by HF pump 68 having an inlet 69 and an outlet 70; and a subgroup IV_F*F configuration differs from a subgroup IV_FF configuration in that CR pump 10 is replaced, in the manner shown in FIG. 11, by HF pump 68.

[00488] Subgroup IV_NF configurations are obtained by deleting CR pump 10 from sub-group IV_FF configurations. Refrigerant outlet 6 of condenser 4 must be no lower than refrigerant inlet 2 of evaporator 1 in all group IV configurations having no CR pump. This is a necessary and not a sufficient requirement for operability. (In fact, the requirements for operability on the height of outlet 6 are more complex in group IV configurations with no CR pump than in group II configurations with no CR pump and no EO pump.)

[00489] Examples of group IV configurations having a subcooler refrigerant auxiliary circuit with no preheater refrigerant passages are obtained by deleting preheater 60 in FIGS. 10, 10A, and 11.

[heading-00490] 5. Group V Configurations

[00491] The key distinctive characteristic of group V configurations, compared to other groups of configurations with an NP evaporator, is that they have, in addition to a subcooler refrigerant auxiliary circuit, a type 1 evaporator refrigerant auxiliary circuit. Broadly speaking, group V configurations are combinations of group II configurations with a subcooler refrigerant auxiliary circuit which may include the one or more refrigerant passages of a preheater.

[00492] I distinguish between group V configurations with a subcooler refrigerant auxiliary circuit having a subcooler whose refrigerant passages are a part of the configurations' refrigerant principal circuit (as well as of the subcooler refrigerant auxiliary circuit) and group V configurations with a subcooler refrigerant auxiliary circuit having a subcooler whose refrigerant passages are not a part of the configurations' refrigerant principal circuit. I shall refer to the former subcooler refrigerant auxiliary circuit as an ‘interactive-type subcooler refrigerant auxiliary circuit’, or more briefly as an ‘I-type subcooler refrigerant auxiliary circuit’; and to the latter subcooler refrigerant auxiliary circuit as a ‘non-interactive-type subcooler refrigerant auxiliary circuit’, or more briefly as a ‘NI-type subcooler refrigerant auxiliary circuit’. Group V configurations with an I-type subcooler refrigerant auxiliary circuit have a 3-port (type 1) separator and group V configurations with an NI-type subcooler refrigerant auxiliary circuit have either a 5-port (type 1) or a 6-port (type 1) separator.

[00493] I use a first superscript to indicate the absence or presence of a subcooler, other than a subcooler having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit; a second superscript to indicate the absence or presence of a superheater; and a third superscript to indicate the presence or absence of a preheater other than a preheater having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit. In the case of the first superscript, a ‘o’ (zero), an ‘s’, an ‘s′’, and an ‘s″’, indicate that group V configurations, designated by the symbols with these superscripts, have respectively

• [00494] (a) no subcooler other than a subcooler having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit,
• [00495] (b) a subcooler having one or more refrigerant passages that are a part of the refrigerant principal circuit and of no other refrigerant circuit,
• [00496] (c) a subcooler having one or more refrigerant passages that are a part of the evaporator refrigerant auxiliary circuit and of no other refrigerant circuit, and
• [00497] (d) a first subcooler having one or more refrigerant passages that are a part of the refrigerant principal circuit and of no other refrigerant circuit, and a second subcooler having one or more refrigerant passages that are a part of the evaporator refrigerant auxiliary circuit and no other refrigerant circuit.
  In the case of the second superscript, I use the superscript ‘o’ (zero) and ‘s’ to indicate that group V configurations, designated by symbols with these superscripts have no superheater, and have a superheater, respectively. And in the case of the third superscript, I use a ‘o’ (zero), a ‘p’, a ‘p′’, and a ‘p″’, to indicate that group V configurations with these superscripts, have respectively
• [00499] (a) no preheater other than a preheater having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit;
• [00500] (b) a preheater having one or more refrigerant passages that are a part of the refrigerant principal circuit and of no other refrigerant circuit;
• [00501] (c) a preheater having one or more refrigerant passages that are a part of the evaporator refrigerant auxiliary circuit and of no other refrigerant circuit; and
• [00502] (d) a first preheater having one or more refrigerant passages that are a part of the refrigerant principal circuit and of no other refrigerant circuit, and a second preheater having one or more refrigerant passages that are a part of the evaporator refrigerant auxiliary circuit and of no other refrigerant circuit.

[00503] In the case of group V configurations with an I-type subcooler refrigerant auxiliary circuit, I use the symbols V_FF, V_FF*, V_F*F, and V_NF, to designate subgroups of group V configurations with respectively

• [00504] (a) a CR pump and an SC pump,
• [00505] (b) a CR pump and an HF pump,
• [00506] (c) an HF pump and an SC pump, and
• [00507] (d) an SC pump and no CR or HF pump.
  Each of the foregoing four subgroups of group V configurations may have no EO pump or may have an EO pump. I designate subgroup V_FF, V_FF*, V_F*F, and V_NF, configurations with no EO pump by the symbols V_FFN, V_FF*N, V_F*FN, and V_NFN, respectively; and subgroup V_FF, V_FF*, V_F*F, and V_NF, configurations with an EO pump by the symbols V_FFF, V_FF*F, V_F*FF, and V_NFF, respectively.

[00509] A class V_FFF^s″sp′ configuration with an I-type subcooler refrigerant auxiliary circuit and with a 2-port receiver is shown in FIG. 12. A class V_FFF^s″sp′ configuration with an I-type subcooler auxiliary refrigerant circuit can be looked at as a class II_FF^s″sp configuration with a 3-port (type 1) separator to which has been added a subcooler refrigerant auxiliary circuit whose subcooler and preheater refrigerant passages are a part of the configuration's refrigerant principal circuit.

[00510] A class V_FF*F^s″sp′ configuration differs from a class V_FFF^s″sp′ configuration in that SC pump 63 is replaced, in the manner shown in FIG. 12A, by HF pump 68; and a class V_F*FF^s″sp′ configuration differs from a class V_FFF^s″sp′ configuration in that CR pump 10 is replaced, in the manner shown in FIG. 13, by HF pump 68. And, in general, sub-subgroup V_FF*F configurations differ from sub-subgroup V_FFF configurations in the same way as (class) V_FF*F^s″sp′ configurations differ from (class) V_FFF^s″sp′configurations; and sub-subgroup V_F*FF configurations differ from sub-subgroup V_FFF configurations in the same way as (class) V_F*FF^s″sp′ configurations differ from (class) V_FFF^s″sp′ configurations.

[00511] Sub-subgroup V_FFN, V_FF*N, and V_F*FN, configurations are obtained by deleting EO pump 27 from subgroup V_FFF, V_FF*F, and V_F*FF, configurations, respectively; subgroup V_NFF and V_NF*F configurations are obtained by deleting CR pump 10 from subgroup V_FFF and V_FF*F configurations, respectively; and subgroup V_NFN configurations are obtained by deleting EO pump 27 from subgroup V_NFF configurations. (Refrigerant outlet 6 of condenser 4 must be no lower than refrigerant inlet 2 of evaporator 1 in all group V configurations that do not have a CR pump or an HF pump.)

[00512] Examples of group V configurations having an I-type subcooler refrigerant auxiliary circuit with no preheater refrigerant passages are obtained by deleting preheater 60 in FIGS. 12, 12A, and 13.

[00513] In the case of group V configurations with an NI-type subcooler refrigerant auxiliary circuit, I use the symbols V_FF and V_NF to designate subgroups of group V configurations with a CR pump, and no CR pump, respectively; the symbols V_FFF and V_FFN to designate subgroups of subgroup V_FF configurations with an EO pump, and no EO pump, respectively; and the symbols V_NFF and V_NFN to designate subgroups of subgroup V_NF configurations with an EO pump, and no EO pump, respectively.

[00514] A class V_FFN^ssp configuration with an NI-type subcooler refrigerant auxiliary circuit, a 6-port (type 1) separator, and a 2-port receiver, is shown in FIG. 5A, and a class V_FFF^s″sp″ configuration with an I-type refrigerant auxiliary circuit, a 5-port (type 1) separator, and a 2-port receiver, is shown in FIG. 7A. The former group V configuration can be looked at as a class II_FN^ssp configuration in which the 4-port separator has been replaced by a 6-port separator and to which an NI-type subcooler refrigerant auxiliary circuit has been added; and the latter group V configuration can be looked at as a class II_FF^s″sp″ configuration in which the 3-port separator has been replaced by a 5-port separator and to which an NI-type subcooler refrigerant auxiliary circuit has been added. The subcooler refrigerant auxiliary circuit in FIGS. 5A and 7A includes subcooler 71, having a refrigerant inlet 72 and a refrigerant outlet 73; a preheater 74, having a refrigerant inlet 75 and a refrigerant outlet 76; and SC pump 63, which controls the circulation of liquid refrigerant around subcooler refrigerant auxiliary circuit 77-72-73-64-65-75-76-78 where 77 and 78 are respectively a liquid outlet and a liquid inlet of type 1 separator 21. 1 note that the positions of SC pump 63 and subcooler 71 around the NI-type subcooler refrigerant auxiliary circuit can be interchanged.

[00515] Examples of group V configurations having an NI-type subcooler refrigerant auxiliary circuit with no preheater are obtained by deleting preheater 74 in FIGS. 5A and 7A.

[heading-00516] 6. Group VI Configurations

[00517] The key distinctive characteristic of group VI configurations, compared to other groups of configurations with an NP evaporator, is that they have, in addition to a subcooler refrigerant auxiliary circuit, a type 2 evaporator refrigerant auxiliary circuit. Broadly speaking, group VI configurations are combinations of group III configurations with a subcooler refrigerant auxiliary circuit.

[00518] I distinguish—as in the case of group V configurations—between group VI configurations with an I-type subcooler refrigerant auxiliary circuit and group VI configurations with an NI-type subcooler refrigerant auxiliary circuit. Group VI configurations with an I-type subcooler refrigerant auxiliary circuit may—unlike group V configurations with an l-type subcooler refrigerant auxiliary circuit—have a 4-port (type 2) separator as well as a 3-port (type 2) separator; and group VI configurations with an NI-type subcooler refrigerant auxiliary circuit may—like group V configurations with an NI-type subcooler refrigerant auxiliary circuit—have either a 5-port (type 2) separator or a 6-port (type 2) separator. However, the differences between group VI configurations with 3-port and 4-port separators, and between group VI configurations with 5-port and 6-port separators, are only minor; and therefore only 3-port separator and 5-port separator group VI configurations are shown. (4-port separator group VI configurations and 6-port separator group VI configurations can be deduced easily respectively from the three 3-port separator group VI configurations shown (see FIGS. 14, 14A, and 15) and from the one 5-port group VI configuration shown (see FIG. 9A) by comparing FIG. 8A with FIG. 8.)

[00519] In the case of group VI configurations with an I-type subcooler refrigerant auxiliary circuit, I use the symbol VI_FF to designate group VI configurations with a DR pump and an SC pump; the symbol VI_FF* to designate the subgroup of group VI configurations with a DR pump and an HF pump, and the symbol VI_F*F to designate the subgroup of group VI configurations with an HF pump and an SC pump. I use a first superscript to indicate the absence or presence of a subcooler, other than a subcooler having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit; and a second superscript to indicate the absence or presence of a superheater. In the case of the first superscript, a ‘o’ (zero), and an ‘s’ indicate that group VI configurations, designated by the symbols with these superscripts, have respectively

• [00520] (a) no subcooler other than a subcooler having one or more refrigerant passages that are a part of the subcooler refrigerant auxiliary circuit, and
• [00521] (b) a subcooler having one or more refrigerant passages that are a part of the refrigerant principal circuit and not of the subcooler refrigerant auxiliary circuit.
  In the case of the second superscript, a ‘o’ (zero) and an ‘s’ indicate that group VI configurations, designated by symbols with these superscripts, have no superheater, and have a superheater, respectively.

[00523] A class V_FF^ss configuration with a 3-port separator and a 2-port receiver is shown in FIG. 14. A class VI_FF^ss configuration can be looked at as a class III_F^ss configuration to which has been added a subcooler refrigerant auxiliary circuit whose subcooler and preheater passages are a part of the configuration's refrigerant principal circuit.

[00524] A class VI_FF*^ss configuration differs from a class VI_FF^ss configuration in that SC pump 63 is replaced, in the manner shown in FIG. 14A, by HF pump 68; and a class VI_F*F^ss configuration differs from a class VI_FF^ss configuration in that DR pump 46 is replaced, in the manner shown in FIG. 15, by HF pump 68. And, in general, subgroup VI_FF* configurations differ from subgroup VI_FF configurations in the same way as class VI_FF*^ss configurations differ from class VI_FF^ss configurations; and subgroup VI_F*F configurations differ from subgroup VI_FF configurations in the same way as class VI_F*F^ss configurations differ from class VI_FF^ss configurations.

[00525] Subgroup VI_NF configurations are obtained by deleting DR pump 46 from subgroup VI_FF configurations.

[00526] Examples of group VI configurations having an I-type subcooling refrigerant auxiliary circuit with no preheater refrigerant passages are obtained by deleting preheater 60 from FIGS. 14, 14A, and 15.

[00527] In the case of group VI configurations with an NI-type subcooler refrigerant auxiliary circuit, there exist only subgroup VI_FF configurations.

[00528] A class VI_FF^ss configuration with an NI-type subcooler refrigerant auxiliary circuit and a 5-port separator is shown in FIG. 9B. This configuration can be looked at as a class III_FF^ss configuration in which the 3-port separator has been replaced by a 5-port separator and to which NI-type subcooler refrigerant auxiliary circuit 79-72-73-64-65-75-76-80 has been added, where numerals 79 and 80 designate respectively a liquid-refrigerant outlet and a liquid-refrigerant inlet of separator 42.

[00529] Examples of group VI configurations having an NI-type subcooler refrigerant auxiliary circuit with no preheater refrigerant passages are obtained by deleting preheater 74 in FIGS. 5A and 7A.

[heading-00530] 7. Group VII and VIII Configurations

[00531] Group VII and VIII configurations are derived from respectively group I to VI configurations by replacing the NP evaporator in the latter configurations by a P evaporator. Thus, for example, a class VII_F^s configuration is a class I_F^s configuration in which NP evaporator 1 has been replaced by P evaporator 81 (see FIGS. 16 and 16A), and a class X_FF^s configuration is a class IV_FF^s configuration in which NP evaporator 1 has been replaced by P evaporator 81 (see FIG. 16B). Numeral 123 designates the refrigerant liquid-vapor interface inside a P evaporator.

[heading-00532] 8. Group II*, III*, V*, VI*, VIII*, IX*, XI*, and XII*, Configurations

[00533] Group II*, V*, VIII*, and XI*, configurations are, by definition, principal configurations derived from respectively group II, V, VIII, and XI, configurations by replacing type 1 separator 21 by type 1 separating assembly 21*; and group III*, VI*, IX*, and XII*, configurations are, by definition, principal configurations derived from respectively group III, VI, IX, and XII, configurations by replacing type 2 separator 42 by type 2 separating assembly 42*, and by adding a receiver whenever the four last-cited groups have no receiver and a receiver is required. (A receiver is usually required unless condenser 4 can also perform the function of a receiver. An example of such a condenser is a shell-and-tube condenser with refrigerant outside its tubes.) Thus, for example, a class VIII*_FN^ooo configuration is a class VIII_FN^ooo configuration in which separator 21 has been replaced by separating assembly 21* (see FIG. 17); and a class IX*_FN^oo configuration is a class IX_FN^oo configuration in which separator 42 has been replaced by separating assembly 42* (see FIG. 18), and to which—where the class IX_FN^oo configuration has no receiver—a receiver has been added. (The receiver may be a 1-port or a 2-port receiver.)

[00534] However, whereas in symbols designating classes belonging to group III, VI, IX, and XII, configurations, the first superscript is either a ‘o’ (zero) or an ‘s’; in symbols designating classes belonging to group III*, VI*, IX*, and XII*, configurations the first superscript can, in addition to a ‘o’ or an ‘s’, also be an ‘s′’, an ‘s″’, or an ‘s′″’. A ‘o’ indicates classes belonging to group III* and IX* configurations having no subcooler; and classes belonging to group VI* and XII* configurations having no subcooler other than a subcooler whose one or more refrigerant passages are a part of the configurations' subcooler refrigerant auxiliary circuit. An ‘s’ indicates classes belonging to group III* and IX* configurations having a subcooler whose one or more refrigerant passages are a part of the configurations' principal refrigerant circuit and evaporator refrigerant auxiliary circuit, and of no other refrigerant circuit; and classes belonging to group VI* and XII* configurations having a subcooler whose one or more refrigerant passages are a part of the configurations' principal refrigerant circuit and evaporator refrigerant auxiliary circuit, and of no other refrigerant circuit other than a subcooler whose one or more refrigerant passages are a part of the configurations' subcooler refrigerant auxiliary circuit. An ‘s′’ indicates classes belonging to group III* and IX* configurations having a subcooler whose one or more refrigerant passages are part of the configurations' one or more evaporator refrigerant auxiliary circuits and of no other refrigerant circuit; and classes belonging to group VI* and XII* configurations having a subcooler whose one or more refrigerant passages are part of the configurations' one or more evaporator refrigerant auxiliary circuits, and of no other refrigerant circuit other than a subcooler whose one or more refrigerant passages are a part of the configurations' subcooler refrigerant auxiliary circuit. An ‘s″’ indicates classes belonging to group III* and IX* configurations having a first subcooler whose one or more refrigerant passages are part of the configurations' refrigerant principal circuit and of the configurations' evaporator refrigerant auxiliary circuit; and a second subcooler whose one or more refrigerant passages are part of the evaporator refrigerant auxiliary circuit, and of no other refrigerant circuit; and classes belonging to group VI* and XII configurations having a first subcooler whose one or more refrigerant passages are part of the configurations' refrigerant principal circuit and of the configurations' evaporator refrigerant auxiliary circuit; and a second subcooler whose one or more refrigerant passages are part of the evaporator refrigerant auxiliary circuit, and of no other refrigerant circuit other than a subcooler whose one or more refrigerant passages are a part of the configurations' subcooler refrigerant auxiliary circuit. And an ‘s′″’ indicates classes belonging to group III* and IX* configurations having a subcooler whose one or more refrigerant passages are part of the refrigerant principal circuit, and of no other refrigerant circuit; and classes belonging to group VI* and XII* configurations having a subcooler whose one or more refrigerant passages are part of the refrigerant principal circuit, and of no other refrigerant circuit other than a subcooler whose one or more refrigerant passages are a part of the configurations' subcooler refrigerant auxiliary circuit.

[heading-00535] 9. General Remarks on Principal Configurations

[00536] In FIGS. 1 to 15, and in FIGS. 17 and 18, refrigerant inlet 2 represents a set of one or more points or ports through which liquid enters NP evaporator 1, and refrigerant outlet 3 represents a set of one or more points or ports through which refrigerant vapor exits evaporator 1. Similarly, in FIGS. 16, 16A, and 16B, refrigerant inlet 82 represents a set of one or more points or ports through which liquid refrigerant enters P evaporator 81 and refrigerant outlet 83 represents a set of one or more points or ports through which refrigerant vapor exits evaporator 81. I note that the ports of an evaporator refrigerant inlet may not be at the same level, and that the ports of an evaporator refrigerant outlet may not be at the same level. I also note that the set of ports of an evaporator refrigerant inlet may be higher or lower than, or on the same level as, the set of ports of an evaporator refrigerant outlet.

[heading-00537] 10. Specialized Configurations

[00538] The present invention includes, in addition to the groups of principal configurations discussed in section V, several specialized groups of principal configurations which may be preferred for certain special applications.

[00539] A first specialized group of principal configurations consists of principal configurations having a type 1′ separator. The principal configuration shown in FIG. 19 is an example of configurations having a type 1′ separator designated by numeral 98 and having a vapor inlet port 99 and a vapor outlet port 100.

[00540] A second group of specialized principal configurations consists of principal configurations having an upper special header through which liquid refrigerant is distributed to the one or more refrigerant passages of their evaporator, the special header being, under most operating conditions, filled only partially with liquid refrigerant. The principal configuration shown in FIG. 20 is an example of a principal configuration having such a special header. The principal configuration shown in FIG. 20, where numeral 93 designates the special header, can be viewed as a class III_FN^oo configuration with a refrigerant inlet above its refrigerant outlet, which has been modified by replacing its upper liquid header by special header 93.

[00541] A third specialized group of principal configurations consists of principal configurations having a liquid-refrigerant auxiliary transfer means for transferring by gravity liquid refrigerant in a pool evaporator to the liquid-refrigerant principal transfer-means segment upstream from the principal configuration's refrigerant principal pump. Three examples of such specialized configurations are shown in FIGS. 21 to 23. The principal configuration shown in FIG. 21 can be viewed as a class III*_FN^oo configuration to which liquid-refrigerant line 94-95 has been added, thereby providing means for transferring by gravity liquid refrigerant in evaporator 1 to the configuration's liquid-refrigerant principal transfer-means segment upstream from DR pump 46. The principal configuration in FIG. 22 can be viewed as a class III*_FN^oo configuration to which liquid-refrigerant line 94-96 has been added, thereby again providing means for transferring by gravity liquid refrigerant to the configuration's liquid-refrigerant principal transfer-means segment upstream from DR pump 46. And the principal configuration shown in FIG. 23 can be viewed as a class II*_FN^ooo configuration to which liquid-refrigerant line 94-97 has been added, thereby providing means for transferring liquid-refrigerant to the configuration's liquid-refrigerant principal transfer-means segment upstream from refrigerant principal pump 360 having an inlet 361 and an outlet 362. (I note that, after the addition of refrigerant line 94-97, the principal pump of the class II*_FN^ooo configuration is neither a CR pump nor a DR pump.) I shall refer to a P evaporator having (liquid-refrigerant) overflow outlet 94 as an ‘overflow P evaporator’ to distinguish it from a ‘non-overflow P evaporator’ having no such overflow outlet. I would mention that I distinguish between an evaporator overflow outlet and an evaporator drain outlet. The former outlet controls, under most operating conditions, the level of liquid refrigerant in a P evaporator; whereas the latter outlet does not.

[heading-00542] 11. Integral Evaporator-separator Combinations

[00543] The principal configurations of the invention include configurations in which a type 1 or a type 1′ separator is physically an integral part of an NP evaporator. Any integral evaporator-separator combination, employed in conventional (namely in airtight) steam generators and in refrigeration equipment, can also be employed in the airtight configurations of the invention—provided the evaporator-separator combination used is constructed with materials and joining techniques compatible with the refrigerant employed and suitable for airtight configurations. Examples of evaporator-separator combinations range from an evaporator-separator combination having a single evaporator refrigerant passage, and a separator whose separator vessel is a small sphere, to an evaporator-separator combination having, like the so-called four-drum Stirling-type boilers, hundreds of refrigerant passages. I give here just enough examples of evaporator-separator combinations to show how they fit into the principal configurations. I use in these examples a class II_FN^ooo configuration with a 2-port receiver and certain principal configurations with a type 1′ separator; but other—although not all—principal configurations with a type 1, or a type 1′, separator could also have been used.

[00544] The integral evaporator-separator combination shown in FIGS. 24 and 24A, in FIGS. 24B and 24C, in FIG. 24D, and in FIG. 24E, have respectively a 3-port type 1 separator, a 4-port type 1 separator, a 2-port type 1′ separator, and a 3*-port type 1′ separator; the type 1 separators being designated by numeral 21 and the type 1′ separators by numeral 98, both types having a cylindrical separator vessel whose axis is normal to the paper. Four of the foregoing six combinations also have a liquid header, designated by numeral 101, the axis of the liquid header being also normal to the paper. All six combinations have several evaporator refrigerant passages designated by numeral 102; and four evaporator-separator combinations have a type 1 evaporator refrigerant auxiliary circuit having a liquid-refrigerant-return segment consisting of one or more refrigerant lines designated collectively by numeral 103.

[00545] In FIGS. 24 and 24B, alphanumeric symbols 102a and 102b designate respectively the left-hand and right-hand banks (in planes normal to the paper) of the evaporator's refrigerant passages, and alphanumeric symbols 22a and 22b designate respectively the left-hand and right-hand rows of separator-vessel ports (in planes normal to the paper) corresponding to vapor inlet 22 of a type 1 separator. In FIGS. 24A and 24C to 24E, numeral 102 designates a single bank of evaporator refrigerant passages. In FIGS. 24A and 24C, numeral 22 designates a single row of separator-vessel ports corresponding to vapor inlet 22. In FIG. 24A numeral 103 designates a single liquid-refrigerant return line, and numeral 24 designates a single separator-vessel port, and, in FIGS. 24, 24B and 24C, numeral 103 designates a single bank of liquid-refrigerant return lines and numeral 24 designates a single row of separator-vessel ports corresponding to liquid outlet 24 of a type 1 separator, each member of the bank of liquid-refrigerant return lines including, in the case of FIG. 24C, the set of refrigerant lines shown. In FIG. 24D, numeral 99 designates a row of separator-vessel ports corresponding to vapor inlet 99 in FIG. 19. Finally, in FIG. 24E, numeral 104 designates the liquid inlet of the 3*-port type 1′ separator shown, numeral 105 designates a row of separator-vessel inlet-outlet ports through which liquid refrigerant exits separator 98 and through which refrigerant vapor enters separator 98, and numeral 100 designates, as in FIG. 24D, a separator-vessel outlet port through which refrigerant vapor exits separator 98. (Evaporator refrigerant passages 102 in FIG. 24E must be large enough to allow so-called ‘sewer flow’ to occur.)

[heading-00546] 12. Component Heat Exchangers, Component Heat Sources, and Component Heat Sinks

[00547] Each of the heat exchangers represented by a rectangle in the FIGURES may be a ‘unitary heat exchanger’ consisting, by definition, of a single unit; or may be a ‘split heat exchanger’ that includes, by definition, several separate and physically-distinct heat-exchanger units I shall hereinafter refer to as ‘component heat exchangers’. Component heat exchangers of the same split heat exchanger may have their refrigerant passages connected in series, in parallel, or both in series and in parallel; the refrigerant passages of all component heat exchangers of a given split heat exchanger constituting the split heat exchanger's refrigerant passages. In the particular case where a heat exchanger is a hot heat exchanger, a cold heat exchanger, an evaporator, a preheater, a superheater, a condenser, a subcooler, and a desuperheater, I shall refer to the heat exchanger's component heat exchangers respectively as ‘component hot heat exchangers’, ‘component cold heat exchangers’, ‘component evaporators’, ‘component preheaters’, ‘component superheaters’, ‘component condensers’, ‘component subcoolers’, and ‘component desuperheaters’.

[00548] A heat source of a given split hot heat exchanger may be either a ‘unitary heat source’, consisting, by definition, of a single not readily-divisible heat source; or may be a split heat source consisting of several readily-distinguishable component heat sources. A unitary hot heat exchanger has almost always a unitary heat source, but a split hot heat exchanger may have either a unitary heat source or a split heat source. In the former case all the component heat exchangers of the split hot heat exchanger have the selfsame heat source, whereas in the latter case at least two of the component heat exchangers of a split hot heat exchanger have readily-distinguishable component heat sources of the split heat source. Similarly, a heat sink of a given split cold heat exchanger may be either a ‘unitary heat sink’, consisting, by definition, of a single not readily-divisible heat sink; or may be a split heat sink consisting of several readily-distinguishable component heat sinks. A unitary cold heat exchanger has almost always a unitary heat sink, but a split cold heat exchanger may have either a unitary heat sink or a split heat sink. In the former case all the component heat exchangers of the split cold heat exchanger have the selfsame heat sink, whereas in the latter case at least two of the component heat exchangers of a split cold heat exchanger have readily-distinguishable component heat sources of the split heat sink.

[00549] I note that in certain embodiments of the invention the selfsame heat exchanger is under certain operating conditions a hot heat exchanger, and is under certain other operating conditions a cold heat exchanger.

[heading-00550] 13. Compoment Seperating Devices, Component Receivers, Component Refrigerant Pumps, and Component Refrigerant Valves

[00551] Briefly—as in the case of heat exchangers—separating devices, receivers, refrigerant pumps, refrigerant valves, and other elements of airtight configurations, may be a ‘unitary element’ consisting, by definition, of a single unit; or may be a ‘split element’ that includes, by definition, several separate and physically-distinct units I shall hereinafter refer to, in general, as ‘component elements’ and for example specifically as ‘component separating devices’, ‘component receivers’, ‘component refrigerant pumps’, and ‘component refrigerant valves’. In particular, a refrigerant principal circuit, or a refrigerant auxiliary circuit, may include one or more refrigerant-circuit segments with several sets of parallel branches. Each branch of a set of parallel branches may, for example, include a component preheater, a component NP evaporator, and a component separating device; and another set of parallel branches may include a component condenser, a component receiver, and a component subcooler. Furthermore, a refrigerant principal circuit, or a refrigerant auxiliary circuit of a principal configuration may have sub-branches merging into branches which in turn merge into a single refrigerant-circuit segment. Thus, for example, a single principal configuration may—as in a system reduced to actual practice by S. Molivadas—have sixteen parallel branches, each of which contains four component NP evaporators, connected in series to four parallel branches, each of which contains a component separating device and more specifically a component separator; and four parallel branches, each of which contains a component condenser.

[heading-00552] 14. Split Refrigerant Principal Configurations

[00553] All the principal configurations discussed so far have a single evaporator and a single condenser, either of which may be a unitary or a split heat exchanger. I shall refer to the foregoing principal configurations as ‘unitary principal configurations’. In certain applications, the refrigerant principal circuit of a principal configuration may consist of several branches which have either (1) a common component evaporator and different condensers, or (2) a common component condenser and different evaporators. I shall refer to the last-cited principal configurations as ‘split principal configurations’. Examples of split principal configurations are given later in this DESCRIPTION.

[00554] The branches of a spiit principal configuration have the selfsame refrigerant and a common refrigerant principal-circuit segment. However, each of these branches can often be thought of conceptually as belonging to distinct principal configurations which can be grouped and classified in the same way as unitary principal configurations.

[heading-00555] 15. Subatmospheric Airtight Configurations

[00556] I use the term ‘subatmospheric airtight configurations’ to denote airtight configurations whose refrigerant pressure always stays—except in the case of a failure—below ambient atmospheric pressure while they are active and while they are inactive.

[00557] I note that prior-art so-called vapor, vacuum, and variable-vacuum, steam systems have non-airtight configurations. Consequently, their configurations, while inactive, ingest air until their refrigerant pressure reaches ambient atmospheric pressure, and therefore this pressure does not always stay below ambient atmospheric pressure. Furthermore, all of the foregoing three prior-art systems are operated at positive as well as negative gauge pressures; typically at positive gauge pressures up to 5 psig (0.345 bar gauge) in the case of vacuum and variable-vacuum systems. It follows that the refrigerant-circuits (water-steam circuits) of the three prior-art systems cited above must use components designed to withstand internal working pressures as well as external working pressures, and to meet the requirements of applicable pressure-vessel and pressure-piping codes.

[00558] By contrast, airtight configurations having aqueous solutions as their refrigerant, and maximum heat-sink temperatures substantially below (say at least 15° C. below) the refrigerant's saturated-vapor temperature at ambient atmospheric pressure, can be operated so that their refrigerant pressure always stays below ambient atmospheric pressure. It follows that the refrigerant circuits of such configurations can be equipped with one or more pressure-relief devices that release refrigerant (into the ambient air) when their refrigerant exceeds only slightly ambient atmospheric pressure (because, for example, of a system malfunction).

[00559] Subatmospheric airtight configurations—namely airtight configurations whose refrigerant pressure always stays below ambient atmospheric pressure—are not restricted to a particular kind of refrigerant, and may use any azeotropic-like or non-azeotropic refrigerant. Neither are subatmospheric airtight configurations restricted to transferring heat to heat sinks at temperatures below the boiling point of their refrigerant at ambient atmospheric pressures. For example, a subatmospheric airtight configuration whose refrigerant is lithium can transfer heat to heat sinks well above 1000° C. even at ambient atmospheric pressures at sea level.

[00560] The refrigerant passages of subatmospheric airtight configurations need not be capable of withstanding net internal pressures. This allows heat exchangers to be made with techniques which greatly reduce their cost, and which make them immune to damage by frozen refrigerants that, like H₂O, expand when they change from their liquid to their solid phase. For example, a heat exchanger can be made of two flat or tubular sheets of material—such as copper, copper-plated steel, or aluminum—joined together only around their perimeter by, for instance, brazing or welding. One or both sheets have corrugations, waffle-like patterns, or hybrid patterns, that form, when the two sheets are held against each other, a panel having refrigerant passages connected to a refrigerant inlet, and to a refrigerant outlet, located at opposite ends of the two sheets' common perimeter. FIGS. 25 and 26 show a cross-section of two sheets of thermally-conducting material. The two sheets are designated by the numerals 106 and 107. Sheet 106 is a flat sheet whereas sheet 107 is embossed, or is stamped, to form parallel channels over at least a part of its surface. The cross-sections of the last-cited channels are designated by numerals 108a to 108e in FIGS. 25 and 26. Sheets 106 and 107 are joined together only around their perimeter. (Points 109 and 110 in FIGS. 25 and 26 represent two sides of that perimeter). Consequently, when the pressure exerted by a fluid or by a solid, located between sheets 106 and 107, exceeds the ambient atmospheric 5 pressure of a fluid surrounding sheets 106 and 107, these two sheets will move apart as shown in FIG. 26. However, when the pressure exerted by a fluid located between sheets 106 and 107 is less than the pressure of the surrounding fluid, the surrounding fluid will press sheets 106 and 107 together. In this second case, channels 108a to 108e form, as shown in FIG. 25, separate and distinct fluid passages. Fluid passages formed in the manner just described can be used as refrigerant passages of any one of the six kinds of heat exchangers cited in definitions (2) to (7) in part III,A of this DESCRIPTION, provided the pressure of the surrounding fluid exceeds the refrigerant pressure inside channels 108a to 108e while the principal configuration of the airtight configuration containing those channels is active.

[heading-00561] 16. Principal-configuration Controllable Elements

[00562] ‘Principal-configuration controllable elements’, referred to in the CLAIMS as ‘principal-configuration controllable means’, are, by definition, elements of a principal configuration controlled by the two-phase heat-transfer system to which the principal configuration belongs. Principal-configuration controllable elements include refrigerant pumps and refrigerant valves.

[00563] The control of controllable elements of an airtight configuration, and in particular of a principal configuration, of the invention may be two-step, multi-step, or proportional: usually two-step or proportional in the case of unidirectional controllable pumps, and usually three-step or proportional in the case of bidirectional controllable pumps such as certain refrigerant pumps, certain hot-fluid pumps and cold-fluid pumps, and certain other fluid pumps. I shall say that a set of one or more system-controllable elements is controlled so that the characterizing parameter controlled by the set stays close to, or tends to, a preselected value where the preselected value is a single value. Proportional control can be achieved by using a modulated analog signal or by using a modulated pulsed signal.

[heading-00564] 1. Liquid-refrigerant Reservoirs

[00565] The liquid-refrigerant (LR) reservoirs used in type A or in type B combinations can be any known kind of suitable fixed-volume reservoir, or any known kind of suitable variable-volume reservoir having an internal volume which can be changed by the two-phase heat-transfer system to which the variable-volume reservoir belongs. The word ‘suitable’ in the immediately preceding sentence denotes properties such as compatibility with the liquid refrigerant stored in an LR reservoir, and the ability to withstand the range of refrigerant pressures and temperatures over which the LR reservoir is to be used.

[00566] Examples of variable-volume reservoirs are (1) structures, such as bellows-type and bladder-type devices, and (2) combinations of a deformable and a rigid structure, such as a rigid cylinder with for instance a cylindrical or a spheroidal shape, which together form a space within which liquid refrigerant is stored. I shall refer to the former reservoirs as ‘type 1 variable-volume reservoirs’ and to the latter reservoirs as ‘type 2 variable-volume reservoirs’, but I shall designate all variable-volume LR reservoirs by the same numeral.

[00567] In the case cited under (1) in the immediately-preceding minor paragraph, an external rigid structure may have to be used to constrain lateral and/or longitudinal motions of the variable-volume reservoir. Whether or not such an external frame is necessary depends on (1) the material or materials from which the reservoir is made, and (2) the tilts and accelerations to which it will be subjected. In type II_R ancillary configurations (see section V,C,2,b,ii), the rigid structure mentioned in the immediately-preceding sentence may be provided by the mechanism used to provide the external mechanical force; and in type III_R ancillary configurations (see section V,C,2,b,iii), the rigid structure may be provided by a rigid container in which the deformable structure is partly or entirely enclosed.

[heading-00568] 2. Types of Ancillary Configurations

[00569] a. Definitions of Type I_R to VI_R Configurations

[00570] Most of the (refrigerant) ancillary configurations which can be used in type A and type B combinations (of the invention) can be grouped into six general types:

• [00571] (a) type I_R configurations which have a variable-volume reservoir, and which employ a (refrigerant) liquid-transfer pump, or more briefly an LT pump, to change the amount of liquid refrigerant stored in the reservoir;
• [00572] (b) type II_R configurations which have a variable-volume reservoir, and which employ a mechanism to change the reservoir's internal volume—by exerting an external mechanical force on the reservoir—and thereby change the amount of liquid refrigerant stored in the reservoir;
• [00573] (c) type III_R configurations which have a variable-volume reservoir, and which employ a fluid, outside the reservoir, to change the reservoir's internal volume—by exerting an external pressure on the reservoir—and thereby change the amount of liquid refrigerant in the reservoir;
• [00574] (d) type IV_R configurations which have a fixed-volume (LR) reservoir, containing a fixed amount of inert gas in direct contact with liquid refrigerant in the reservoir, and which employ an LT pump to change the amount of liquid refrigerant in the reservoir;
• [00575] (e) type V_R configurations which have a fixed-volume reservoir, containing a fixed amount of inert gas in direct contact with liquid refrigerant in the reservoir, and which employ external means to change the temperature of the inert gas contained in the reservoir, and thereby change the amount of liquid refrigerant in the reservoir; and
• [00576] (f) type VI_R configurations which have a fixed-volume reservoir, containing a variable amount of inert gas in direct contact with liquid refrigerant in the reservoir, and which employ an inert-gas configuration to change the amount of inert gas in the reservoir, and thereby change the amount of liquid refrigerant in the reservoir.

[00577] b. Typical Type I_R to VI_R Configurations

[00578] i. Type I_R Configurations

[00579] FIG. 27 shows typical components employed in a type I_R configuration. In FIG. 27, numeral 400 denotes a principal configuration; and numeral 401 designates a variable-volume LR reservoir having an inlet-outlet refrigerant port 402 (through which liquid refrigerant can flow in either direction). The variable-volume LR reservoir is attached to fixed structure 417.

[00580] The LR reservoir shown is a type 1 bellows-type reservoir with a flexible corrugated cylindrical wall 403, but the LR reservoir could, as mentioned earlier, be any kind of variable-volume reservoir.

[00581] Numeral 404 (in FIG. 27) designates an LT pump having inlet-outlet ports 405 and 406, and numeral 407 designates an inlet-outlet port or node at which liquid refrigerant in the ancillary configuration merges with refrigerant in the principal configuration—usually with liquid refrigerant in the principal configuration's refrigerant principal circuit. Pump 404 is a bidirectional pump capable of inducing liquid-refrigerant flow from port 405 toward port 402, or liquid-refrigerant flow from port 406 toward port 407. Port 407 can be located at any point of the principal configuration at which the refrigerant void fraction is essentially zero at the time liquid refrigerant is being transferred from the principal configuration to the ancillary configuration. Pump 404 would in most applications be a positive-displacement pump.

[00582] In the particular case where

• [00583] (a) the LR reservoir's corrugated cylindrical wall offers a resistance which is small compared to the pressure p_R of the liquid refrigerant in reservoir 401 and to the pressure p_A of the reservoir's ambient fluid, which is usually the earth's atmosphere, and where
• [00584] (b) the relevant friction-induced refrigerant-pressure drops and gravity-induced pressure on the refrigerant are also small compared to both p_R and p_A,
  the pressure head which must be produced by pump 404 is approximately equal to the difference (p_R−p_A) In the foregoing particular case, the maximum pressure head which must be produced by pump 404 can often be reduced by using a spring 478 to equalize the head which must be produced by pump 404 in the two directions of refrigerant flow induced by it. For example, if the ambient fluid is the atmosphere at sea level, the value of p_A will be about one atmosphere, and if the normal operating value of p_R is two atmospheres, a spring exerting a pressure of one-half atmosphere on reservoir 401, in the same direction as p_A, will reduce the maximum required pressure head of pump 404 from one atmosphere to one-half atmosphere.

[00586] ii. Type II_R Configurations

[00587] FIG. 28 shows an example of a rudimentary mechanism for exerting an external mechanical force on a type 1 variable-volume reservoir. In this rudimentary example, vise 408—comprising fixed jaw 409, movable jaw 410, slide 411, and screw 412—is driven by reversible electric motor 413. Jaws 409 and 410 are bonded to respectively the lower and upper walls of reservoir 401. This bonding allows vise 408 to exert a bidirectional force capable of increasing and decreasing the internal volume of reservoir 401. A type II_R configuration usually has a single reversible electric motor, but it may also have instead two non-reversible electric motors.

[00588] The foregoing rudimentary vise-type mechanism may be optimal in the case where the maximum absolute value of the difference (p_R−p_A) is a fraction of a bar and the diameter of the reservoir 401 is only a couple of centimeters. However, in cases where the maximum value of the last-cited pressure difference, or the last-cited diameter, is substantially larger, a pair of screws on opposite sides of the bellows, in a plane containing the bellows' center line, would usually be preferred. These two screws would be driven through gears, by a single motor.

[00589] In the case of a type 2 variable-volume reservoir, the position of the deformable device could be controlled by a motor driving a single screw as shown in FIG. 29. In FIG. 29, variable-volume reservoir 401 has a rigid structure, designated by numeral 414, and a deformable structure designated by numeral 415. Plate 416 is bonded to deformable structure 415 and is moved up and down, without rotating, by screw 412 and by motor 413. Motor 413 moves up and down with screw 412, but its case is prevented from rotating by keys (not shown). A spring (not shown) between plate 416 and fixed structure 417 may be used where desirable. (The last-cited spring could be concentric with screw 412.)

[00590] Screw 412 may be turned manually, instead of by an electric motor or other non-manually controlled device. FIG. 30 illustrates the particular case where screw 412 is turned manually using handwheel 479. Air-permeable device 418 in FIGS. 29 and 30 allows air to enter and exit the space between fixed structure 417 and deformable structure 415.

[00591] iii. Type III_R Configurations

[00592] FIG. 31 illustrates the case where the fluid is compressed air and reservoir 401 is a type 1 variable-volume reservoir having a flexible corrugated wall 403. In FIG. 31, reservoir 401 is located in rigid closed cylinder 419. One of the ends of reservoir 401 is bonded to one of the ends of cylinder 419, but wall 403 can slide inside cylinder 419. Air-transfer pump 420 changes the internal volume of reservoir 401 by varying the pressure of the air in space 421.

[00593] FIG. 31A illustrates the case where the fluid outside the reservoir is a hydraulic fluid. In FIG. 31A, hydraulic pump 422 varies the mass of hydraulic fluid in space 421 by transferring hydraulic fluid between space 421 and hydraulic-fluid reservoir 423 which may, but need not, be at atmospheric pressure.

[00594] iv. Type IV_R Configurations

[00595] FIG. 32 shows a type IV_R ancillary configuration. In FIG. 32, numeral 424 designates a fixed-volume LR reservoir having a liquid-refrigerant inlet-outlet port 425, and numeral 426 designates the quasi-horizontal interface surface, inside reservoir 424, between liquid refrigerant on the one hand and inert gas mixed with refrigerant vapor on the other hand. The fixed mass of inert gas, inserted permanently in reservoir 424, allows LT pump 404 to vary substantially the amount of liquid refrigerant in reservoir 424.

[00596] v. Type V_R Configurations

[00597] FIG. 33 shows a type V_R ancillary configuration in the particular case where the temperature of the inert gas inside reservoir 424 is changed by, for example, circulating a liquid in coil 427, and by varying the temperature of the liquid being circulated.

[00598] vi. Type VI_R Configurations

[00599] FIG. 34 shows a type V_R configuration in which the amount of inert gas in reservoir 424 is varied by inserting inert gas in, and extracting inert gas from, reservoir 424 through inert-gas pipe 428-429 connected, at point 429, to inert-gas (IG) configuration 430. (Line 449-454 is a liquid-refrigerant line for returning liquid refrigerant removed from inert gas in IG configuration 430.)

[00600] c. Alternative Type I_R To VI_R Ancillary Configurations

[00601] One of several alternative forms of each of the type I_R to VI_R ancillary configurations shown in FIGS. 27 to 34, and 31A, may be preferable in certain applications. I mention next a few typical examples.

[00602] In certain applications it may be desirable for port 407—where liquid refrigerant in the ancillary configuration merges with liquid refrigerant in the principal configuration—to be replaced (see, for example, FIGS. 27A and 32A; FIGS. 28A, 29A, 30A, and 31B; and FIGS. 33A, and 34A) by inlet 431 where liquid refrigerant, in the ancillary configuration, exits the ancillary configuration and enters the principal configuration, and by outlet 432 where refrigerant, in the principal configuration, exits the principal configuration and enters the ancillary configuration. In the eight last-cited FIGURES, numerals 433 and 434 designate unidirectional (one-way) valves. I shall hereinafter refer collectively to ancillary configurations with a common inlet-outlet port as ‘one-port ancillary configurations’ and to ancillary configurations with separate and distinct inlet and outlet ports as ‘two-port ancillary configurations’.

[00603] An example of applications where two-port ancillary configurations may be desirable are those where the preferred refrigerant is a non-azeotropic fluid such as an aqueous glycol solution. The reasons for which two-port ancillary configurations may be desirable, where the last-cited solutions are employed as a refrigerant, are given in section V,F,2.

[00604] Bidirectional LT pumps, air-transfer pumps, and hydraulic pumps, may be unavailable, or may be too costly, for the particular requirements of certain applications. Where this is true, two unidirectional LT pumps, air-transfer pumps, or hydraulic pumps, as applicable, can obviously be employed instead of a single bidirectional LT pump, air-transfer pump, or hydraulic pump, respectively. FIGS. 27B and 32B illustrate the particular case where a bidirectional LT pump has been replaced by two unidirectional LT pumps, namely the particular case where bidirectional LT pump 404 has been replaced by unidirectional LT pumps 404A and 404B.

[00605] A first alternative to employing two unidirectional LT pumps, air-transfer pumps, or hydraulic pumps (where a bidirectional LT pump, air-transfer pump, or hydraulic pump, is not available or is too costly) is to employ a single unidirectional LT pump, air-transfer pump, or hydraulic pump, in parallel with a bidirectional (two-way) valve. This alternative is shown, for the particular case of a refrigerant pump and a variable-volume LR reservoir, in FIG. 27C, where numeral 435 designates a refrigerant bidirectional (two-way) liquid-transfer valve, or more briefly a bidirectional LT valve, in parallel with a unidirectional LT pump. (Valve 435 can, for example, be a motorized valve.) In cases where a bidirectional LT valve is employed with variable-volume LR reservoir 401, a spring—like internal spring 478 (see FIG. 27)—may often have to be used to contract or to expand reservoir 401, and thus help to ensure liquid refrigerant flows from reservoir 401 lo the principal configuration, or vice versa, when valve 435 is open. Alternatively, for example, a gas, located for instance between double flexible LR reservoir walls 437, (see FIG. 35) could be used to perform the function of a spring. A unidirectional LT pump and a bidirectional LT valve can be used with a type I_R, or with a type IV_R, configuration; a unidirectional air-transfer pump and a bidirectional air-transfer valve can be used with a type III_R configuration employing compressed air; and a unidirectional hydraulic pump and a bidirectional hydraulic-fluid valve can be used with a type II_R configuration employing an hydraulic fluid.

[00606] A second alternative to employing two unidirectional LT pumps, air-transfer pumps, or hydraulic pumps, is to use known means for reversing the direction of flow induced by a unidirectional LT pump, between two points. Examples of such means are described in section V,N of my co-pending U.S. patent application Ser. No. 400,738, filed 30 Aug. 1989.

[00607] In cases where liquid refrigerant leaks through bidirectional LT pump 404, unidirectional LT pump 404A, or unidirectional LT pump 404B, while it is not running, a bidirectional LT valve can be used in series with any one of the three last-cited pumps to eliminate, or to help reduce, the rate at which refrigerant leaks through each of those pumps while it is not running. Bidirectional valves can be used for a similar purpose, in series with an air-transfer pump or a hydraulic pump. The particular case where a bidirectional LT valve is used in series with a bidirectional LT pump is shown in FIG. 32C for the case where the LR reservoir is a fixed-volume reservoir. Numeral 436 in FIG. 32C designates a bidirectional LT valve in series with a unidirectional LT pump. (Valve 436 is open while pump 404 is running and is closed while pump 404 is not running, and could be a solenoid valve.)

[heading-00608] 1. Inert-gas Reservoirs

[00609] The inert-gas (IG) reservoirs used in type B and in type C combinations (of the invention) can be any kind of suitable fixed-volume reservoir, or any kind of suitable variable-volume reservoir having an internal volume which can be changed by the two-phase heat-transfer system to which the variable-volume reservoir belongs. The word ‘suitable’, in the immediately-preceding sentence, denotes properties such as compatibility with the inert gas and with the refrigerant (which may be contained in the inert gas), and the ability to withstand the range of inert-gas pressures and temperatures over which an IG reservoir is to be used.

[00610] Variable-volume IG reservoirs may, like variable-volume LR reservoirs, be divided into type 1 variable-volume reservoirs and into type 2 variable-volume reservoirs.

[heading-00611] 2. Types of Inert-gas Configurations

[00612] a. Definitions of Type I_G to V_G Configurations

[00613] Most of the inert-gas (IG) configurations which can be used in type B and type C combinations can be grouped into five general types:

• [00614] (a) type I_G configurations which have a variable-volume (IG) reservoir, and which employ a (inert-) gas-transfer pump, or more briefly a GT pump, to change the mass of inert gas in the variable-volume reservoir;
• [00615] (b) type II_G configurations which have a variable-volume reservoir, and which employ a mechanism to change the reservoir's internal volume—by exerting an external force on the reservoir—and thereby change the mass of inert gas in the reservoir;
• [00616] (c) type III_G configurations which have a variable-volume reservoir, and which employ a fluid, outside the reservoir, to change the reservoir's internal volume—by exerting an external force on the reservoir—and thereby change the mass of inert gas in the reservoir;
• [00617] (d) type IV_G configurations which have a fixed-volume reservoir, and which employ a GT pump to change the mass of inert gas in the reservoir; and
• [00618] (e) type V_G configurations which have a fixed-volume reservoir and which employ means to change the temperature of the inert gas in the reservoir, and thereby change the mass of inert gas in the reservoir.

[00619] The five types of IG configurations listed under (a) to (e) in this section V,D,2 are usually employed to insert inert gas in, and to extract inert gas from, a principal configuration, but can also be used to insert inert gas in, and to extract inert gas from, an LR reservoir. The foregoing five types of IG configurations are described in section V,D,2,b.

[00620] b. Typical Type I_G to V_G Configurations

[00621] i. Type I_G Configurations

[00622] FIG. 36 shows a type I_G configuration where numeral 400 designates a principal configuration; where numeral 440 designates a port, at a point of the principal configuration where the (refrigerant) void fraction is high, through which inert gas flows in both directions; and where numeral 441 designates a variable-volume IG reservoir, containing usually essentially only an inert gas, which has an inlet-outlet inert-gas port 442 (through which inert gas can flow in either direction). Reservoir 441 can—as in the case of a variable-volume LR reservoir—be a type 1 or a type 2 variable-volume reservoir. (A bladder-type type 1 variable-volume reservoir is shown, as an example, in FIG. 36.)

[00623] GT pump 443 is a bidirectional GT pump having ports 444 and 445 through which it can induce inert-gas flow either from port 444 to port 445 or from port 445 to port 444. Alternatively, a unidirectional GT pump can be used together with means for reversing the direction of inert-gas flow between ports 444 and 445.

[00624] When GT pump 443 induces inert gas to flow from port 440 toward port 442, it will at times be mixed with a small amount of refrigerant vapor. Condensate-type refrigerant-vapor trap 446, having inlet-outlet gas port 447, and inlet-outlet gas port 448, is used to help ensure no significant amount of refrigerant vapor enters GT pump 443 and reservoir 441. To this end, trap 446 includes means for cooling, and thereby condensing, refrigerant vapor contained in inert gas. Liquid refrigerant, generated by condensation in trap 446, is returned by gravity from liquid outlet 449 of trap 446 to principal-configuration inlet 450.

[00625] ii. Type II_G Configurations

[00626] FIG. 37 shows a type II_G configuration where a mechanism is used instead of GT pump 443. (A bellows-type type 1 variable-volume reservoir is shown, as an example, in FIG. 37.) 35 The mechanism shown, as an example, is a vise-type mechanism including (1) reversible electric motor 413, which drives screws 412A and 412B through pinion 451 and through gear wheels 452A and 452B; and (2) fixed jaw 409 and movable jaw 410. A type II_G configuration usually has a single reversible electric motor, but may also have two non-reversible electric motors. The mechanism shown in FIG. 37 could be controlled manually if motor 413 were replaced with, for example, a handwheel.

[00627] iii. Type III_G Configurations

[00628] FIG. 38 shows a type III_G configuration where the fluid, outside the reservoir, is air. The bellows-type type 1 variable-volume reservoir shown, as an example, is located in rigid closed cylinder 419. One of the ends of reservoir 441 is bonded to one of the ends of cylinder 419, but corrugated wall 403 can slide inside cylinder 419. Air-transfer pump 420 changes the internal volume of reservoir 441 by varying the mass of the air in space 421.

[00629] FIG. 38A shows a type III_G configuration where the fluid, outside the reservoir, is a hydraulic fluid. In FIG. 38A, hydraulic pump 422 varies the mass of hydraulic fluid in space 421 by transferring hydraulic fluid between space 421 and hydraulic-fluid reservoir 423 which may be, but need not be, at atmospheric pressure.

[00630] iv. Type IV_G Configurations

[00631] FIG. 39 shows a type IV_G configuration. In FIG. 39, numeral 453 designates a fixed-volume IG reservoir having an inlet-outlet port 454. (A spherical type 1 reservoir is shown as an example.) GT pump 443 is used to transfer inert gas between principal configuration 400 and reservoir 453.

[00632] v. Type V_G Configurations

[00633] FIG. 40 shows a type V_G configuration where the temperature of the inert gas in reservoir 453 is changed, for example, by circulating a liquid in coil 427, and by varying the temperature of the liquid being circulated.

[00634] c. Alternative Type I_G to V_G Inert-gas Configurations

[00635] One of several alternative forms of each of the type I_G to V_G configurations shown in FIGS. 36 to 40, and in FIG. 38A, may be preferable in certain applications. I mention next a few typical examples.

[00636] In certain applications it may be desirable for port 440 to be replaced by inlet 470 (see, for example, FIGS. 36A to 40A) where inert gas in the IG configuration enters the principal configuration, and by outlet 471 where inert gas in the principal configuration exits the principal configuration and enters the IG configuration. In FIGS. 36A, 37A, 38B, 39A, and 40A, numerals 472 and 473 designate unidirectional valves. I shall hereinafter refer collectively to inert-gas configurations with a common inlet-outlet port as ‘one-port inert-gas configurations’ and to inert-gas configurations with separate and distinct inlet and outlet ports as ‘two-port inert-gas configurations’.

[00637] In certain applications bidirectional GT pumps, air-transfer pumps, and hydraulic pumps, may be unavailable, or may be too costly, for the particular requirements of those applications. Where this is true, two unidirectional GT pumps, air-transfer pumps, or hydraulic pumps, as applicable, can obviously be employed instead of a single bidirectional GT pump, air-transfer pump, or hydraulic pump, respectively. FIGS. 36B and 39B illustrate the particular case where a bidirectional GT pump has been replaced by two unidirectional GT pumps, namely the particular case where GT pump 443 has been replaced by unidirectional GT pumps 443A and 443B.

[00638] A first alternative to employing two unidirectional GT pumps, air-transfer pumps, or hydraulic pumps (where a bidirectional GT pump, air-transfer pump, or hydraulic pump, is not available or is too costly) is to employ a single unidirectional GT pump, air-transfer pump, or hydraulic pump, in parallel with a bidirectional (two-way) gas-transfer valve, or more briefly a bidirectional GT valve. This alternative is shown, for the particular case of a GT pump and a fixed-volume IG reservoir, in FIG. 36C, where numeral 475 designates a bidirectional GT valve in parallel with a unidirectional GT pump. (Valve 475 can, for example, be a motorized valve.) A unidirectional GT pump and a bidirectional GT valve can be used with a type I_G, or with a type IV_G, configuration; a unidirectional air-transfer pump and a bidirectional air-transfer valve can be used with a type III_G configuration employing compressed air; and a unidirectional hydraulic pump and a bidirectional hydraulic-fluid valve can be used with a type III_G configuration employing an hydraulic fluid.

[00639] A second alternative to employing two unidirectional GT pumps, air-transfer pumps, or hydraulic pumps, is to use known means for reversing the direction of flow, induced by a unidirectional GT pump, between two points.

[00640] In cases where inert gas leaks through bidirectional GT pump 443, unidirectional GT pump 404A, or unidirectional GT pump 404B, while it is not running, a bidirectional GT valve can be used in series with any one of the three last-cited pumps to eliminate, or to help reduce, the rate at which inert gas leaks through each of those pumps while it is not running. The particular case where a bidirectional GT valve is used in series with a bidirectional GT pump is shown in FIG. 39C for the case where the IG reservoir is a fixed-volume reservoir. Numeral 476 in FIG. 39C designates a bidirectional GT valve in series with a bidirectional GT pump. (Valve 476 is open while pump 443 is running and is closed while pump 443 is not running.)

[00641] In cases where inert gas entering an IG reservoir contains some refrigerant vapor, condensed refrigerant vapor, accumulating in the IG reservoir, can be removed by providing a bidirectional drain valve, in parallel with a GT pump. FIG. 39D shows the particular case where bidirectional drain valve 477 is used in parallel with bidirectional GT pump 443, and where the IG reservoir is a fixed-volume reservoir. Valve 477 is opened occasionally to allow liquid refrigerant accumulating in reservoir 453 to drain back into principal configuration 400. (Valves 476 and 477, in contrast to valve 475, would usually be two-step valves.)

[heading-00642] 3. Condensate-type Refrigerant-vapor Traps

[00643] The complexity of the condensate-type refrigerant-vapor traps employed in inert-gas configurations depends on the particular application in which they are being used.

[00644] The condensate-type refrigerant-vapor trap shown in FIGS. 36D, 37B, 38C, 39E, and 40B includes trap accessory condenser 456 having inlet-outlet gas ports 457 and 458, trap accessory condenser 459 having inlet-outlet gas ports 460 and 461, and liquid-refrigerant diverter 462, or more briefly LR diverter 462, having inlet-outlet gas ports 463 and 464, and liquid outlet 465. Condensers 456 and 459 are used to reduce the mass-flow rate at which refrigerant vapor enters, as applicable, variable-volume IG reservoir 441, or fixed-volume IG reservoir 453.

[00645] Most of the refrigerant vapor—where present—in inert gas entering condenser 456 is condensed in condenser 456. The resulting liquid refrigerant is entrained by the inert gas in which the liquid refrigerant is contained toward LR diverter 462, where the entrained liquid refrigerant is diverted to liquid outlet 465. Inert gas, entering LR diverter 462 at 463, exits at 464. Residual refrigerant vapor, in inert gas exiting at 464, is condensed in condenser 459 and the resulting liquid refrigerant is returned by gravity in gas line 460-464 which has a cross-sectional area large enough for liquid refrigerant and gas to flow in opposite directions.

[00646] Condensers 456 and 459 may, for example, be air-cooled condensers, water-cooled condensers, or (liquid) refrigerant-cooled condensers. In the first case, condensers 456 and 459 may merely be a finned tube; and, in the second and third cases, condensers 456 and 459 may merely be a tube with a coil, wrapped around the tube, carrying a cold fluid, and LR diverter 462 may, for example, be a small vessel or a tee, whose ports are inlet-outlet gas ports 463 and 464, and liquid outlet 465.

[00647] Condensers 456 and 459, and LR diverter 462, may be combined into a single unit. A first example of a single-unit condensate-type refrigerant-vapor trap is shown in FIGS. 36E, 37C, 38D, 39F, and 40C, for the case where condensers 456 and 459 are finned tubes and LR diverter 462 is a tee. And a second example of a single-unit condensate-type refrigerant-vapor trap is shown in FIGS. 36F, 37D, 38E, 39G, and 40D, for the case where condenser 456 and LR diverter 462 (in FIGS. 36D, 37B, 38C, 39E, and 40B) consist in essence of vessel 480, with three ports, having coil 481 wrapped around it; and where condenser 459 is a tube having coil 482 wrapped around it. In the former five FIGURES numerals 466 and 467 designate the fins of respectively condensers 456 and 459; and, in the latter five FIGURES numerals 481 and 482 designate the coils of, respectively, condensers 456 and 459.

[00648] I note that condenser 456 is often not necessary, and that, in this case, a principal configuration's receiver may replace LR diverter 462. Where a receiver is used also as a diverter, condenser 456, inert-gas lines 440-447-457 and 458-463, and liquid-refrigerant line 449-450, are eliminated.

[heading-00649] 4. Inert-gas Special Configurations and Inert-gas Passive Configurations

[00650] Inert-gas (IG) special configurations differ from IG configurations essentially only in that they transfer inert gas between the LR reservoir of a type VI_R ancillary configuration and an IG reservoir instead of between a principal configuration and an IG reservoir. Liquid refrigerant exiting trap 446 at outlet 449 is returned by gravity either

• [00651] (a) to a point of the ancillary configuration, for example—as shown in FIG. 34—to point 454 of fixed-volume LR reservoir 424.
• [00652] (b) to point 450 of the principal configuration, as shown in FIG. 41.
  Points 429 and 455 in FIGS. 34 and 41 may coincide with points 447 and 449, respectively, of trap 446. (In the case where point 455 coincides with point 449, liquid-refrigerant line 455-450 in FIG. 41 corresponds to liquid-refrigerant line 449-450 in FIGS. 36 to 40.)

[00654] Inert-gas passive (IGP) configurations can, like IG configurations, be one-port configurations or two-port configurations. An IGP configuration can, also like an IG configuration, have a condensate-type refrigerant-vapor trap.

[00655] I mentioned in section V,P of my U.S. patent application Ser. No. 400,738, filed 30 Aug. 1989, the need to remove a non-condensable gas, and in particular hydrogen, which may be generated inside the refrigerant passages of an airtight refrigerant configuration or of an evacuated refrigerant-circuit configuration. And I mentioned the use of membranes permeable to a non-condensable gas, but not permeable to the airtight configuration's refrigerant, as a means for getting rid of a non-condensable gas. Another means for getting rid of a particular non-condensable gas is to use, at one or more locations inside an airtight refrigerant configuration, a solid or a liquid, not miscible with the refrigerant, which will absorb that non-condensable gas; for example, to use hydrazine to absorb hydrogen. Still another means for getting rid of a non-condensable gas is to use a non-condensable-gas trap similar to that described on page 48 of NASA Technical Briefs, December 1990.

[00656] In FIG. 42, non-condensable-gas trap 490 is represented merely by the trap's tube, and is located in the vapor header of condenser 4, but could be located in a refrigerant line where the (refrigerant) void fraction is high; or in a receiver, or a separator, at a point where the void fraction is high. Also tube 491 of trap 490 need not be vertical, and can even be horizontal if it includes a wick. The refrigerant-circuit configuration shown in FIG. 42 is a class I_F^o principal configuration, but trap 490 can be used, where required, with any other principal configuration of a type A combination, or with any refrigerant-circuit configuration of an evacuated configuration.

[00657] The immediately-following text in this minor paragraph is an excerpt from page 48 cited in the first minor paragraph of this section V,E. “The trap . . . includes a tube of stainless steel or other poorly thermally conductive material . . . attached to a tap on top of the main vapor line where the vapor flows toward the condenser. Subcooled liquid from the outlet of the condenser cools the upper end of the tube below the vapor temperature. A small fraction of the flow in the main vapor line enters the trap and travels to the upper end. There, the vapor condenses, and the liquid is returned to the main line by gravity. (In the absence of gravity, it could be returned by the capillary action of a wick.) Noncondensable gas . . . entrained in the upward flow of vapor accumulates gradually, thereby increasing the effective thermal conductance of the upper end of the trap and decreasing the temperature T₁ measured by a thermocouple near the upper end. When T₁ decreases to a preset differential above T₂, the temperature of the incoming coolant, a solenoid valve at the upper end opens momentarily to vent the noncondensable gas.”

[00658] In FIG. 104, numeral 492 designates a coil through which flows the fluid, referred to as ‘the coolant’ in the preceding quotation, employed to condense the refrigerant in the trap; numeral 493 designates a pair of transducers for determining the temperature differential between two points of the trap; numeral 494 designates a solenoid valve; numeral 495 designates a control unit which receives the signals generated by transducers 493, and which controls valve 494. Numeral 496 designates a wick; numeral 497 designates an optional manual valve; and numeral 498 designates a segment of a refrigerant space of a principal configuration where the void fraction is high and through which refrigerant vapor flows in the direction indicated by the arrows.

[00659] The trap shown on page 48 of the cited NASA document uses, as mentioned in the above quotation, subcooled refrigerant to condense refrigerant vapor in the trap. However, cold water can be used, instead of subcooled refrigerant. (The qualifier ‘cold’, in the immediately-preceding sentence, indicates that water, flowing in the last-cited coil, is substantially colder than refrigerant entering the trap.) Alternatively, in certain applications, where air surrounding the trap is cold enough, coil 492 in FIG. 104 can be replaced merely by fins in thermal contact with the trap.

[00660] I note that the only significant difference between non-condensable gas traps and the condensate-type refrigerant-vapor traps discussed in this DESCRIPTION is that the former traps include a unidirectional device for causing and controlling the discharge of gas into an airtight configuration's, or into an evacuated configuration's, surroundings; whereas the latter traps include no such device.

[heading-00661] 1. Preliminary Remarks

[00662] I discuss in this section V,F applications where the properties complete minimum-pressure maintenance and self regulation are required, and where refrigerant-controlled heat release, or more briefly RC heat-release, is usually also required.

[00663] Piston-engine cooling applications provide good examples of applications where a heat source (1) requires the evaporator refrigerant passages of a principal configuration to have sharp bends and non-uniform cross-sections; (2) subjects those passages to spatially highly non-uniform heat fluxes; and (3) has temperatures far above the maximum-permissible temperatures for those passages and the refrigerant in them.

[00664] By contrast, piston-engine intercooling systems provide good examples of applications where a heat source (1) does not require the evaporator refrigerant passages of a principal configuration to have sharp bends and non-uniform cross-sections; (2) does not subject those passages to spatially highly non-uniform heat fluxes; and (3) has no temperatures above the maximum-permissible temperatures for those passages and the refrigerant in them.

[00665] In sections V,F,2 and V,F,3 I describe type A combinations, and their associated control techniques, for the case where the combinations' condenser is an air-cooled condenser. The most prominent examples of piston-engine cooling and intercooling systems with air-cooled condensers are probably those installed in automobiles and trucks. However, piston-engine cooling and intercooling systems with air-cooled condensers are also suitable for other automotive vehicles such as locomotives, for certain industrial fixed installations, and for certain passenger and cargo planes.

[00666] In section V,F,4 I describe type A combinations, and their associated control techniques, for the case where the combinations' condenser is a water-cooled condenser. The most prominent examples of piston-engine cooling systems with water-cooled condensers are probably those installed in ships and motor boats, and those installed in industrial fixed installations adjacent to a large body of water such as the sea.

[00667] Because all the type A combinations discussed in this section V,F have no partial minimum-pressure maintenance, I shall for brevity refer in this section V,F to complete minimum-pressure maintenance simply as ‘minimum-pressure maintenance’. This property, as mentioned in section III,D, is achieved in type A combinations by filling completely their principal configuration with liquid refrigerant.

[heading-00668] 2. Cooling Systems with an Air-cooled Condenser

[00669] a. Cooling Systems with a Pool Evaporator

[00670] i. Refrigerant Configuration and Control System

[00671] FIGS. 43 to 45 show a system used to cool piston engine 500 having crankcase 501, cylinder block 502, and cylinder-head 503. I assume engine 500 is an in-line engine with 4 cylinders and is transversely-mounted on an automotive vehicle. (However, the limitations ‘in-line’, ‘4 cylinders’, ‘transversely-mounted’, and ‘automotive vehicle’, are made for specificity only, and do not affect the inventive elements disclosed in this section V,F,2,a.) Engine 500 has (1) in its cylinder block, a set of interconnecting, or of non-interconnecting, refrigerant passages represented symbolically by spaces designated by numeral 504; and (2) in the cylinder head, a set of interconnecting, or of non-interconnecting, refrigerant passages represented symbolically by the space designated by numeral 505. (Space 505 includes the space in cylinder head 503 below as well as above usually-segmented liquid-vapor interface surface 123 represented symbolically by a continuous line.) Refrigerant passages 504 are the engine's ‘cylinder-block coolant passages’, refrigerant passages 505 are the engine's ‘cylinder-head coolant passages’, and refrigerant passages 504 and 505 are collectively the ‘engine's coolant passages’. The engine-cooling system shown in FIGS. 43 to 45 has a refrigerant configuration which is a combination of a type I_R ancillary configuration with a class VIII_FN^ooo principal configuration whose pool-evaporator refrigerant passages are the engine's coolant passages. The evaporator has a refrigerant inlet 82′ having usually one, two, or four, ports and a refrigerant outlet 83″, having four ports (but which may also, for example, have only one port or only two ports). Refrigerant circulating in the principal configuration is assumed, in this section V,F,2,a, to be cooled primarily by an air-cooled condenser.

[00672] Refrigerant vapor, generated in the evaporator and exiting at 83″, is transferred from the evaporator to type 1 separator 21 by vapor manifold 506, having four refrigerant vapor lines (see FIG. 43A). Separator 21 has a vapor inlet 22, which has four ports. Alternatively, for example, inlet 22 may have a single port. In this second case, the four vapor-lines of manifold 506 merge into a single vapor line connected to that single port. Under most operating conditions, essentially dry refrigerant vapor exits separator 21 at 23 and enters upper header 507 of air-cooled condenser 508 at 5. (I use the numeral 5 to designate the refrigerant inlet of any condenser.) Refrigerant vapor entering header 507 flows through several condenser refrigerant passages 399 and condensed refrigerant vapor, generated in passages 399, exits lower header 509 of condenser 508 at 6 and enters 2-port condensate receiver 7 at inlet 8. (I use the numeral 6 to designate the refrigerant outlet of any condenser.) Liquid refrigerant, accumulating in receiver 7, exits at outlet 9, enters inlet 11 of CR pump 10, exits outlet 12 of CR pump 10, and enters at 82′ the evaporator formed by the coolant passages of engine 500. Liquid refrigerant, separated from refrigerant vapor in separator 21, exits at liquid outlet 24 and, after by-passing refrigerant passages 399 of condenser 508, merges at 25 with liquid refrigerant exiting pump 10 at 12. Under most operating conditions, liquid refrigerant in those coolant passages forms liquid-vapor interface surface 123. Interface surface 123 may consist of several separate and distinct segments.

[00673] The class VIII_FN^ooo principal configuration described in the immediately preceding two minor paragraphs has a refrigerant principal circuit 82′-83″-22-23-5-6-8-9-407-11-12-25-82′ and a type 1 evaporator refrigerant auxiliary circuit 82′-83″-22-24-25-82′. The refrigerant configuration shown in FIG. 43 is a combination of that principal configuration with a type I_R ancillary configuration. This configuration includes variable-volume reservoir 401 having inlet-outlet port 402, reversible LT pump 404 having inlet-outlet ports 405 and 406, and liquid-refrigerant ancillary transfer means 402-405-406-407, where numeral 407 denotes a port or node where refrigerant in the ancillary configuration merges with refrigerant in the principal configuration.

[00674] The cooling system shown in FIGS. 43 to 45 also includes condenser fan 510, having a propeller 511 and an electric motor 512, and the control system described next.

[00675] The control system includes central control unit 513 (see FIG. 44), or more briefly CCU 513, which, on the basis of signals received from several transducers and preselected instructions stored in CCU 513, controls pump 10, pump 404, and fan 510. The particular transducers used by the system in FIG. 43 are

• [00676] (a) proportional liquid-level transducer 126 which generates a signal L′_P providing a measure of the current value of the level L_P of liquid-vapor interface surface 123 in the cylinder-head coolant passages of engine 500;
• [00677] (b) proportional liquid-level transducer 113 which generates a signal L′_R providing a measure of the current value of the level L_R of liquid-vapor interface surface 116 in receiver 7;
• [00678] (c) proportional refrigerant absolute-pressure transducer 514 which generates a signal p′_R providing a measure of the current value of the refrigerant pressure p_R at a preselected location in the principal configuration;
• [00679] (d) proportional refrigerant-temperature transducer 516 which generates a signal T′_R providing a measure of the current value of the refrigerant temperature T_R at a preselected location in the principal configuration;
• [00680] (e) a two-step (on-off) first engine-status transducer (not shown) which generates a signal S′_E1 indicating whether engine 500 is running or not running; and
• [00681] (f) a proportional absolute-pressure transducer (not shown) which generates a signal p′_A providing a measure of the current value of the ambient atmospheric pressure p_A.

[00682] The signals generated by the six last-listed transducers are supplied to CCU 513 which computes, on the basis of preselected instructions stored in CCU 513, see FIG. 44, the control quantities C_CR, C_LT, and C_CF, and generates the signals C′_CR, C′_LT, and C′_CF, supplied respectively to CR pump 10, LT pump 404, and to condenser fan 510.

[00683] The control system also includes Minimum-Pressure Maintenance Control Unit 518, or more briefly MPMCU 518, see FIG. 45. This unit operates only while engine 500 in FIG. 43, which I shall hereinafter in this section V,F,2,a refer to as ‘the engine’, is not running. MPMCU 518 is supplied, as shown in FIG. 45, only with signals p′_R, p′_A, and S′_E1, and computes, on the basis of preselected instructions stored in it, control quantity C_LT while the engine is not running (as indicated by signal S′_E1). MPMCU 518 would usually be physically an integral part of a cooling system's CCU, but is shown as a separate and distinct unit for clarity in describing the system's operation. Furthermore, CCU 513 and MPMCU 518 would usually be a part of the engine's management system.

[00684] ii. Unsafe and Safe States

[00685] I shall say that a piston-engine cooling system is in an ‘unsafe state’, when running the engine being cooled by the system is unsafe in the sense that the engine could be damaged, by inadequate cooling, if it started running, or if it continued running. And I shall say that a piston-engine cooling system is in a ‘safe state’ when running the engine being cooled by the system is safe in the sense that the engine would not be damaged by inadequate cooling if it started running, or if it continued running. More precisely, I shall say that the system is in an unsafe state when any one of the following four relations is true:
L_P<L_P,SAFE; L_R<L_R,SAFE; p_R>p_R,SAFE; and T_R>T_R,SAFE;  (1), (2), (3), (4)
and that the system is in a safe state when all of the following four relations are true:
L_P≧L_P,SAFE; L_R≧L_R,SAFE; p_R≦p_R,SAFE; and T_R≦T_R,SAFE.  (5), (6), (7), (8)
Symbols L_C, L_R, L_P, p_R, and T_R, were defined earlier in this section V,F,2,a. The remaining symbols in the last eight relations are defined next: the symbol L_P,SAFE denotes the minimum value of L_P at which the engine should be allowed to run; the symbol L_R,SAFE denotes the minimum value of L_R for which the cooling system's refrigerant pump does not cavitate significantly; and symbols p_R,SAFE and T_R,SAFE denote the maximum values of p_R and T_R, respectively, at which the engine should be allowed to run. (Although condition (6) would not damage the engine directly, it would usually do so indirectly in the sense that it would soon cause the value of L_P to fall below L_P,SAFE.)
iii. Typical Operating Method

[00691] I now outline a typical method of operating the system shown in FIGS. 43 to 45. I shall hereinafter, in this section V,F,2,a,iii, refer to the system shown in FIGS. 43 to 45 as ‘the system’.

[00692] I start at an instant in time when the engine being cooled by the system is not running and is started, say, by an operator manually. When the engine is started, CCU 513 and all its associated transducers and controllable elements are energized, if they are not already energized.

[00693] CCU 513, as soon as it is energized, and subsequently at frequent preselected periodic time intervals while it remains energized, performs a system safety check to determine whether the system is in a safe state. If it is not, an audible and/or visual warning signal is generated to indicate that the system is in an unsafe state, and the engine, after being stopped by the operator, is inhibited from being started. If the unsafe state has occurred because p_R or T_R, or both, have exceeded their safe values, CCU 513 runs fan 510 at its maximum capacity until their safe values are no longer exceeded, and then de-energizes itself automatically. Thereafter MPMCU 518, which is always energized while the system is in a safe state, remains energized and controls LT pump 404 in the same way as in control mode 0. (See next major paragraph.) If the system has become unsafe because of an insufficient refrigerant charge, MPMCU 518 will de-energize itself automatically. (The refrigerant charge is insufficient when relation (1) or (2) is satisfied.)

[00694] I shall describe the operation of systems of the Invention, while they are in their safe state, in terms of ‘control modes’ and ‘transition rules’ between control modes (see definitions 115 and 116 in section III,A). In FIG. 43, the system-controllable elements are CR pump 10, LT pump 404, and condenser fan 510, and are, as a set, controlled differently in each of four different control modes while the system shown in FIGS. 43 to 45 is in a safe state.

[00695] A first mode, mode 0, of the four different control modes, is used to achieve minimum-pressure maintenance.

[00696] A second control mode, mode 1, is used, in the case of a non-azeotropic refrigerant, to achieve quasi-uniform refrigerant-component concentrations after the refrigerant temperature T_R falls below a preselected temperature T_R,MIN, which is (1) lower than the refrigerant's lowest saturated-vapor temperature, while the system's principal configuration is active, and which is (2) higher than the freezing temperature of the refrigerant-component with the highest freezing temperature. The elapsed time Δt, from the instant at which T_R falls below T_R,MIN, is determined by a clock, usually a software clock incorporated in CCU 513. This clock is stopped and reset after a preselected time interval unless the engine is running or starts running. If the engine was stopped and starts running before Δt is equal to the preselected time interval, the clock is stopped and reset at the instant the engine starts running.

[00697] A third control mode, mode 2, is used to achieve refrigerant-controlled heat release, or more briefly RC heat release, which is the particular form of Internally-controlled heat release, or more briefly IC heat release, used in type A combinations.

[00698] A fourth control mode, mode 3, is used to achieve self regulation and, whenever required, also to achieve simultaneously EC heat release. The particular EC heat-release technique used by the system employs a fan (fan 510).

[00699] In mode 0, pump 10 and fan 510 do not run; and MPMCU 518 ensures pump 404 is controlled so that p_R tends to p_RD^o, where p_RD^o is a preselected desired current value for p_R while the system is in mode 0.

[00700] In mode 1 (used only where the refrigerant is a non-azeotropic refrigerant), CCU 513 ensures: (1) pump 10 runs at a preselected effective capacity, usually near or equal to the pump's full effective capacity; (2) pump 404 is controlled so that p_R tends to p_RD, where p_RD is a preselected desired current value for p_R while the system is in modes 1 to 3; and (3) fan 510 does not run.

[00701] In mode 2, CCU 513 ensures: (1) pump 10 is controlled so that L_P tends to L_PD, where L_PD is a preselected desired current value for L_P high enough for all high heat-flux zones of the cylinder-head coolant passages to be covered with liquid refrigerant when the value of L_P is close to L_PD, and low enough for refrigerant vapor exiting separator 21 at 23 to be essentially dry; (2) pump 404 is controlled so that p_R tends to p_RD; and (3) fan 510 does not run.

[00702] In mode 3, CCU 513 ensures: (1) pump 10 is controlled so that p_R tends to p_RD; (2) pump 404 is controlled so that L_R tends to L_RD; and (3) fan 510 is controlled so that p_R tends to p_RD.

[00703] The preselected desired current value p_RD^o, p_RD, or L_PD, (of respectively p_R, p_R, or L_P) may be a constant, or may be a value which changes in a pre-prescribed way as a function of one or more preselected characterizing parameters.

[00704] In the case of p_RD^o, a typical preselected characterizing parameter is the ambient atmospheric pressure p_A, and a typical pre-prescribed way is the relation
p_RD^o=p_A+Δ^op,  (9)
where Δ^op is usually, but not necessarily, a fixed quantity. In the case of p_R, typical preselected characterizing parameters and typical pre-prescribed ways are discussed in section V,H. And, in the case of L_P, the desired current value L_PD is usually a constant unless the condenser overfeed techniques described in section V,F,2,d are used, or unless the vehicle-tilt compensating techniques described in section V,F,2,f are used.

[00707] In the case of a non-azeotropic refrigerant, the transition rules between modes 0, 1, 2, and 3 are (where ‘eng.’ is an abbreviation for ‘engine’):

[00002]

(a)	0 to 1: no transition	(g)	1 to 0: eng. not running
			and clock stops running
(b)	0 to 2: eng. starts running	(h)	2 to 0: no transition
(c)	0 to 3: no transition	(i)	3 to 0: no transition
(d)	1 to 2: eng. starts running and TR ≧	(j)	2 to 1: TR < TR,MIN
	TR,MIN
(e)	1 to 3: no transition	(k)	3 to 1: no transition
(f)	2 to 3: LR < LR,MAX − ΔLR,	(l)	3 to 2: pR < pRD − ΔpR,
	where ΔLR > 0		where ΔpR > 0

In rule (I), the value of Δp_R must be chosen large enough for the value of (p_RD−Δp_R) to be smaller than the value of p_R at which CCU 513 stops fan 510 running while the system is in mode 3.

[00709] In the case of an azeotropic-like refrigerant, mode 1 is eliminated and therefore transitions 0 to 1, 1 to 2, 2 to 1, and 1 to 0, are eliminated and the transition rule under (h) is changed to:

[heading-00710] (h′) modes 2 to 0: eng. not running and T_R<T_R,MIN.

[00711] I note that, when the engine is started, the system may be in control mode 1, 2, or 3; but not in control mode 0 since, with the postulated transition rules, the system cannot be in control I mode 0 while the engine is running.

[00712] iv. Comments on Refrigerant Configuration and Control System

[00713] In this section V,F,2,a,iv I make miscellaneous comments on the refrigerant configuration and control system described in section V,F,2,a,i.

[00714] Where CR pump 10 is a high-slip positive displacement pump or a centrifugal pump, it is usually highly desirable, particularly in the case of two-step (on-off) control, to use unidirectional (one-way) valve 220, as shown in FIG. 43B, to prevent liquid refrigerant flowing from the engine's coolant passages toward receiver 7 through pump 10 while pump 10 is not running.

[00715] Liquid refrigerant, exiting separator 21 at 24, can be returned to one or more points of refrigerant passages 504 or to one or more points of refrigerant passages 505, instead of to point outside the engine's refrigerant passages 504 and 505.

[00716] Proportional liquid-level transducer 113 can be used for three-step control, namely for controlling pump 404 so that it induces an essentially constant positive flow rate, an essentially constant negative flow rate, or no flow rate. If only three-step control of pump 404 is acceptable, a possibly less expensive three-step liquid-level transducer could be used provided the dead zones between steps are large enough to prevent unacceptably-fast cycling of pump 404. Similarly, a two-level (on-off) liquid-level transducer could be used to control two-step (on-off) operation of pump 10. (Three-step and two-step control of respectively pumps 404 and 10 has—among other disadvantages—the disadvantage of making it impracticable to control L_R in mode 3, and L_P in modes 2 and 3, as accurately as with proportional control.)

[00717] Although not essential, the control system may also include two-step liquid-level transducer 517 (see FIG. 43C) which generates a signal L′_C,MAX indicating whether the current value L_C of the refrigerant liquid-vapor interface surface, in air-cooled condenser 508, exceeds or does not exceed a preselected fixed value L_C,MAX corresponding to a level near the bottom of header 507. One of the purposes for which transducer 517 could be used is mentioned later in the last major paragraph of this section V,F,2,a,iv.

[00718] Also, although not essential, the control system may further include two-step liquid-level transducer 519 (see FIG. 43D) which generates a signal L′_H,MAX indicating whether liquid refrigerant has reached the highest point of the system's principal configuration. The information provided by transducer 519 can be used for several purposes, including

• [00719] (a) confirming liquid refrigerant has reached the last-cited highest point before CCU 513 changes the system's control mode from mode 2 to mode 1, thereby increasing system reliability; and
• [00720] (b) assisting in charging the system with refrigerant correctly, and in determining whether the system still has, at a point in time after it has been charged with refrigerant, a sufficient amount of liquid-refrigerant volume to fill the system's principal configuration completely.
  Transducer 519 is located in separator 21 in FIG. 43D because the highest point inside the principal configuration shown in FIG. 43D is in separator 21.

[00722] Finally, in several applications, MPMCU 518 is not required. In this case, mode 0 denotes that the system is in a safe state and that the system's CCU is de-energized. The value of p_R while CCU 513 is de-energized may, for example, be chosen equal to the value of p_RD at the instant T_R falls below T_R,MIN.

[00723] v. Other Refrigerant Configurations and Control Systems.

[00724] It should be clear, from the teachings so far in this DESCRIPTION, that the class VIII_FN^ooo principal configuration shown in FIG. 43 is only one of many kinds of principal configurations with a pool evaporator and an air-cooled condenser which may be preferred for cooling a particular piston engine. Other kinds of preferred principal configurations, in the case of type A combinations, may, for certain piston-engine cooling applications, include class VIII_FN^soo, VIII_FF^ooo, VIII_FN^soo VIII*_FN^ooo, and VIII*_FN^soo, configurations; and, see section V,F,2,g, also class XI_NN^oo, XI_NN^so, XI_FN^oo, XI_FN^so, XI_FF^oo, XI_FF^so, XI*_FN^oo, and XI*_FN^so, configurations, and the specialized configurations shown in FIGS. 21, 22, and 23. (In refrigerant configurations with a subcooler the subcooler would be located ahead of pump 10, or of pump 46, as applicable.)

[00725] I would explain that principal configurations with a subcooler are, in some installations, desirable, or even necessary, to increase the amount of subcool of liquid refrigerant exiting, as applicable, receiver 7, and/or separator 42*, while the system is in control mode 3—to increase, for example, the net positive suction head available, as applicable, to pump 10 or to pump 46. The subcooler used may merely be a quasi-horizontal section of a refrigerant line which is located roughly in the same plane as refrigerant passages 399, and which is exposed to ram air and/or to the airflow induced by fan 510. An example of such a refrigerant line, in the case of a class VIII_FN^soo configuration, is finned refrigerant-line segment 9-522 shown in FIG. 43E.

[00726] I would also explain that in some installations having a principal configuration with a type 1 separator, a refrigerant pump may be desirable, or may be necessary, to return liquid refrigerant from the separator to the configuration's pool evaporator. Examples of installations where this is necessary are those where the desired location of separator 21 results in the level of the refrigerant liquid-vapor interface surface in it being below the level of the refrigerant liquid-vapor interface surface in refrigerant passages 505. FIG. 43F shows a class VIII_FF^ooo principal configuration where EO pump 27 is the refrigerant pump used to return liquid refrigerant exiting separator 21 to mergence point 25. Examples of techniques for controlling pump 27 include techniques for controlling it as a function of the level of liquid refrigerant in separator 21.

[00727] I would further explain that the control-mode rules of CR pump 10 and LT pump 404 can be reversed in control modes 2 and 3 if node 407, where the principal and the ancillary configuration join, were for example located (see FIG. 43G) on refrigerant line 24-25. In particular, in mode 2, pump 10 can be used to control the value of p_R and pump 404 can be used to control the value of L_P.

[00728] It should also be clear from the teachings so far in this DESCRIPTION that a type II_R, type III_R, type IV_R, type V_R, or type VI_R, ancillary configuration could have been used instead of the type I_R ancillary configuration shown in FIG. 43. With types II_R to VI_R configurations, the same control modes and transition rules as those described in section V,F,2,a,iii would apply, except that the controllable element (pump 404) of a type I_R configuration would be replaced by the controllable element of one of the other five types of ancillary configurations; namely, for example, by motor 413 in the case of a type II_R configuration and, as applicable, by handwheel 479, by air-transfer pump 420, or by hydraulic pump 422, in the case of a type III_R configuration.

[00729] Type I_R to VI_R two-port ancillary configurations are often desirable where the refrigerant employed is a two-component non-azeotropic fluid. A typical example of the locations of inlet 431 and outlet 432 are shown in FIG. 43H for the case where a type I_R configuration is used, and where the refrigerant's component with the lower freezing temperature also has the higher evaporation temperature. (See section V,F,2,d,i.)

[00730] A damper or shutter with a controllable aperture upstream from an air-cooled condenser (with respect to the direction of airflow through the condenser) can be used to regulate the volumetric airflow of air through the condenser, and thereby control the rate at which the condenser releases heat to the air surrounding the condenser. I shall refer in this DESCRIPTION to this last-cited kind of heat-release control as ‘shutter-controlled heat-release’, or more briefly ‘SC heat-release’. SC heat release can be used with a system of the invention having an air-cooled condenser instead of, or in addition to, RC heat release. SC heat release is a particular form of externally-controlled passive heat release, or more briefly EC passive heat release.

[00731] I choose the refrigerant configuration shown in FIG. 431 to describe a typical way of achieving SC heat release instead of, or in addition to, RC heat release. In FIG. 43I, numerals 580, 581, and 582, designate respectively condenser shutter 580 controlled by electric motor 581 via control link 582. Where SC heat release is used instead of RC heat release, the shutter aperture is changed so that, for example, the refrigerant pressure, at a preselected location in the principal configuration, tends toward a preselected value. In the particular case of the refrigerant configuration shown in FIG. 43I, mode 2 is replaced by mode 2(s) during which the system's CCU (not shown) ensures (1) pump 10 is controlled so that L_P tends to L_PD; (2) pump 404 is controlled so that L_R tends to L_RD; (3) fan 510 does not run; and (4) shutter motor 581 is controlled by signal C′_SC, supplied by the system's CCU (not shown), so that p_R tends to p_RD.

[00732] Where SC heat release is used, in addition to RC heat release, mode 2 is replaced by modes 2_A(s) and 4_B(s). In mode 2_A(s), the system's CCU (not shown) ensures (1) pump 10 is controlled so that L_P tends to L_PD; (2) pump 404 is controlled so that p_R tends to p_RD; (3) fan 510 does not run; and (4) motor 581 is controlled so that T_R tends to a preselected value T_RD higher than T_R,MIN. And, in mode 2_B(s), the system's CCU ensures (1) pump 10 is controlled so that L_P tends to L_PD; (2) pump 404 is controlled so that p_R tends to p_RD; (3) fan 510 does not run; and (4) shutter 580 is (completely) open.

[00733] The transition rules between modes 2_A(s) and 2_B(s) are

• [00734] (a) 2_A(S) to 2_B(s): L_C≧L_C,MAX
• [00735] (b) 2_B(S) to 2_A(s): L_C<L_C,MAX
  and are based on information provided by transducer 517; and the transition rules, given in section V,F,2,a,iii between mode 2 and the other control modes are replaced by

[00002]

(a)	0 to 2A(s): eng. starts running	(b)	0 to 2B(s):
(c)	1 to 2A(s): eng. starts running and TR ≧ TR,MIN		no transition
(d)	1 to 2B(s): no transition	(e)	2A(s) to 3:
			no transition
(f)	2B(s) to 3: LR < LR,MAX − ΔLR, where ΔLR > 0
(g)	2A(s) to 0: no transition with a non-azeotropic
	refrigerant
	2A(s) to 0: TR < TR,MIN with an azeotropic-like
	refrigerant
(h)	3 to 2A(s): no transition
(i)	3 to 2B(s): pR < pRD − ΔpR, where ΔpR > 0.

[00737] b. Cooling Systems with a Non-pool Evaporator

[00738] i. Preliminary Remarks

[00739] The evaporator in FIG. 43 is a pool evaporator, or more briefly a P evaporator, because, under most operating conditions, a liquid-vapor interface surface (surface 123) is located in the evaporator or, more specifically, in refrigerant passages 505 of the cylinder head of engine 500 shown in FIG. 43. In the case of a wide-angle V-engine, say a 90° V-engine, surface 123 would essentially be non-existent, and therefore a conventional P evaporator would be impracticable. And, even in the case of a 60° V-engine, the area of interface surface 123 would usually be undesirably small even if the engine's cylinder-head coolant passages are shaped in the way shown in U.S. Pat. No. 4,656,974 (Hayashi). Furthermore, locating a liquid-vapor interface surface inside refrigerant passages 505 is often highly undesirable, even in the case of an in-line engine, where the engine is installed in a vehicle. This is particularly true with engines installed in cross-country vehicles, ships, and motor-boats, and with long engines installed in trucks. The absence of a liquid-vapor interface surface inside an engine's cylinder-head coolant passages allows those passages to be smaller. That absence eliminates the need, in the case of the examples cited in the immediately-preceding sentence, to divide the cylinder-head coolant passages of a multi-cylinder engine into several compartments, and to control the liquid-refrigerant level in each compartment independently. (See, for example, U.S. Pat. No. 4,584,971 (Neitz et al).)

[00740] I have therefore devised two-phase engine-cooling systems with no liquid-vapor interface surface in refrigerant passages 505; namely I have devised engine-cooling systems having a non-pool evaporator, or more briefly an NP evaporator. I next give examples of such cooling systems for the case of a V-engine, but similar systems can also be used with an in-line engine, an engine with opposed cylinders, or a radial engine.

[00741] ii. First Refrigerant Configuration, Control System, and Operating Method

[00742] The cooling system shown in FIGS. 46, 47, and 45, has a class II_FN^ooo configuration in which refrigerant exiting the configuration's two NP component evaporators is supplied to separator 21 at a level below the level of liquid-vapor interface surface 521. One of these two component evaporators is formed by the coolant passages of a first bank of cylinders designated by the alphanumeric symbol 500a and the other of the two component evaporators is formed by the coolant passages of a second bank of cylinders designated by the alphanumeric symbol 500b. In FIG. 46, alphanumeric symbols with the letter ‘a’ designate things associated with cylinder bank 500a and alphanumeric symbols with the letter ‘b’ designate things associated with cylinder bank 500b. The relative position of air-cooled condenser 508, with respect to the two banks of cylinders shown in FIG. 46, is usually appropriate for a transversely-mounted engine. A longitudinally-mounted engine would usually have air-cooled condenser 508 mounted so that refrigerant line 5-23 and the horizontal segment of refrigerant line 9-407-11-12-522 would, if they were straight lines, be roughly parallel to the axis of the crankshaft (not shown) of engine 500 shown in FIG. 46.

[00743] Liquid refrigerant, after flowing through node 522, enters at 530′a the NP component evaporator formed by the coolant passages of cylinder bank 500a, and very low-quality refrigerant vapor exits at 3″a; and liquid refrigerant enters at 530′b the NP component evaporator, formed by the coolant passages of cylinder bank 500b, and very low-quality refrigerant vapor exits at 3″b. Substantially dry refrigerant vapor exits separator 21 at 23 and liquid refrigerant in separator 21 exits at 24 and is returned to refrigerant passages 505a and 505b at points 523″a and 523″b, respectively, after flowing through node 524. Each of the alphanumeric symbols 530′a, 530′b, 3″a, 3″b, 523″a, and 523″b, designates a set of ports. The number of ports in each set need not be the same and can range from one to several ports. In the latter case, the number of ports in each set would typically be equal to the number of cylinders in a bank of cylinders, or to a multiple or submultiple of the number of cylinders in a bank of cylinders.

[00744] The location of vapor inlets 22a and 22b of separator 21 below liquid-vapor interface surface 521 helps ensure the refrigerant vapor quality is always low enough to assure potential hot spots in cylinder-head refrigerant passages 505a and 505b are always essentially wetted everywhere with liquid refrigerant without locating separator 21 at heights unacceptable—even in a fixed ground installation—to get the required evaporator overfeed. (See section V,F,2,b,iii.) The cross-sectional area of interface surface 521 is large enough to ensure the velocity of refrigerant vapor passing through that interface surface is small enough for refrigerant vapor exiting separator vapor outlet 23 to be substantially dry without using, in separator 21, separating surfaces that would cause an unacceptably high pressure drop, for example a pressure drop in excess of say 0.01 bar in the case of an aqueous glycol solution at a pressure of one bar.

[00745] Relations (1) to (8) in section V,F,2,a,ii can also be used to determine whether the cooling system shown in FIGS. 46, 47, and 45, is in an unsafe state or in a safe state, and the typical operating method described in section V,F,2,a,iii can also be used to describe the operation of the last-cited system, provided the symbols L_P and L_PD are replaced by the symbols L_S and L_SD (defined below), and provided numeral 123 is replaced by numeral 521. In FIG. 46, proportional liquid-level transducer 125 generates signal L′_S providing a measure of the level L_S of liquid-vapor interface surface 521, and CCU 525 (see FIG. 47) controls pump 10 so that L_S tends to L_SD, where L_SD is the preselected desired current value of L_S.

[00746] The refrigerant configuration shown in FIG. 46—although preferred for certain installations—has, for many installations, at least two handicaps compared to alternative refrigerant configurations having a forced-circulation evaporator refrigerant auxiliary circuit. Firstly, refrigerant lines 3″a-22a and 3″b-22b must have a large-enough cross-sectional area to allow ‘sewer flow’, namely to allow liquid refrigerant and refrigerant vapor to flow in opposite directions; and secondly, separator 21 must be located above refrigerant outlets 3″a and 3″b.

[00747] iii. Second Refrigerant Configuration, Control System, and Operating Method

[00748] The engine-cooling system shown in FIGS. 46A, 48, and 45 differs from the system shown in FIGS. 46, 47, and 45, in that it has EO pump 27 and therefore has a class II_FF^ooo principal configuration; and in that refrigerant exiting the configuration's two component evaporators is supplied to separator 21 at a level above, instead of below, liquid-vapor interface surface 521. CCU 526 shown in FIG. 48, and MPMCU 518 shown in FIG. 45, are used to control the refrigerant configuration shown in FIG. 46A. The amount of evaporator overfeed generated by EO pump 27 must be high enough for the maximum value q_EV,MAX of the quality q_EV of refrigerant vapor exiting the two component evaporators to be low enough to ensure the hottest spots of the surfaces of the walls of refrigerant passages 505a and 505b are essentially everywhere in direct contact with liquid refrigerant. To this end, the maximum permissible value of q_EV,MAX may be as low as 0.15 or even lower, and liquid refrigerant may have to be returned from separator 21 to several locations of the coolant passages of each bank of cylinders. Furthermore, in the case where the refrigerant is, like an aqueous glycol solution, a non-azeotropic fluid, the last-cited control technique must satisfy an additional condition: the amount of overfeed generated by EO pump 27 must be high enough to ensure, and the locations for supplying the overfeed generated by that pump must be placed so that, the refrigerant's liquid phase in the coolant passages of the engine shown in FIG. 46 is mixed sufficiently for that phase to be in quasi-thermal equilibrium throughout those passages. To this end, the maximum-permissible value of q_EV,MAX may also be as low as 0.15 or even lower, and liquid refrigerant may have to be supplied to several locations of the coolant passages of cylinder bank 500a and of cylinder bank 500b.

[00749] The system shown in FIGS. 46A, 47, and 45, can be operated by using similar control modes, and the selfsame transition rules, as those described in section V,F,2,a,iii. I shall refer to the control modes used to operate the system shown in the three last-cited FIGURES as control modes 0′, 1′, 2′, and 3′. In these control modes, CR pump 10, LT pump 404, and condenser fan 510, are operated in the same way as in control modes 0, 1, 2, and 3, respectively. However, the former four control modes differ from the latter four control modes in that they include rules for operating EO pump 27. These rules are (1) in mode 0′ pump 27 does not run; (2) in mode 1′ pump 27 runs at or near maximum capacity; and (3) in modes 2′ and 3′ pump 27 is controlled in the way discussed next. The transition rules between modes 0′, 1′, 2′, and 3′, can be identical to those between modes 0, 1, 2, and 3, in section V,F,2,a,iii.

[00750] Pump 27 can be controlled by any technique which, explicitly or implicitly, maintains the value of q_EV at or below a preselected value q_EV,MAX low enough to prevent burn-out. This can, for example, be accomplished by controlling pump 27 so that the value of q_EV tends toward a desired preselected value q_EV,D which may be fixed, or which may change in a pre-prescribed way as a function of one or more preselected characterizing parameters.

[00751] Because, under steady-state conditions $\begin{array}{cc}{q}_{\mathrm{EV}}=\frac{{\stackrel{\circ }{m}}_C}{{\stackrel{\circ }{m}}_E}=\frac{{\stackrel{\circ }{m}}_C}{{\stackrel{\circ }{m}}_C+{\stackrel{\circ }{m}}_{\mathrm{EO}}}=\frac{1}{1+\left({\stackrel{\circ }{m}}_{\mathrm{EO}}/{\stackrel{\circ }{m}}_C\right)},& \left(10\right)\end{array}$
where {dot over (m)}_C is the refrigerant mass-flow rate induced by pump 10, where {dot over (m)}_EO is the refrigerant mass-flow rate induced by pump 27, and where {dot over (m)}_E is the refrigerant mass-flow rate exiting at 3″a and 3″b, it follows that the quality q_EV of refrigerant vapor exiting the component evaporators, formed by the coolant passages of cylinder banks 500a and 500b, is—under steady-state conditions—a single-valued function of the evaporator-overfeed ratio $\begin{array}{cc}{r}_{\mathrm{EO}}=\frac{{\stackrel{\circ }{m}}_{\mathrm{EO}}}{{\stackrel{\circ }{m}}_C}=\frac{{\stackrel{\circ }{m}}_{\mathrm{EO}}}{{\stackrel{\circ }{m}}_E-{\stackrel{\circ }{m}}_{\mathrm{EO}}}.& \left(11\right)\end{array}$

[00753] Consequently, the desired preselected value q_EV,D can be obtained by controlling r_EO or, almost equivalently, by controlling the ratio of the volumetric-flow rates F_CR and F_EO induced respectively by pumps 10 and 27. Techniques for controlling the ratio of F_CR and F_EO are disclosed in section V,B,3,e of my co-pending U.S. patent application Ser. No.400,738, filed 30 Aug. 1989. (Where pumps 10 and 27 are low-slip positive displacement pumps driven by stepping motors, or by pulse-width controlled motors, CCU 526 can use the signals generated by it, to control those motors, as a measure of the volumetric flow rates F_CR and F_EO induced respectively by pumps 10 and 27. Consequently no flow-rate transducers are necessary to obtain a measure of F_CR and a measure of F_EO.) The foregoing techniques for controlling the ratio F_EO over F_CR, and thus almost equivalently the value of r_EO, are used whenever pump 10 is running. However, pump 10 may not always run while the engine shown in FIG. 46A is running, and consequently the just-cited techniques for controlling the value of r_EO must be supplemented with a technique for ensuring q_EV does not exceed q_EV,MAX while pump 10 is not running. To this end, pump 27 is controlled, in modes 2′ and 3′, in for example the way described in the immediately-following minor paragraph.

[00754] Whenever the engine-cooling system shown in FIGS. 46A, 47, and 45, is in mode 2′, or in mode 3′, CCU 526 inquires whether pump 10 is running. If pump 10 is running, CCU 526 controls the value of F_EO so that it is equal to the current value of F_CR multiplied by r_EO,D, where r_EO,D is the desired value of r_EO. And, if pump 10 is not running, CCU 526 sets the value of F_EO equal to the product of F_CR,1 and r_EO,D, where F_CR,1 is a finite value of F_CR which, for example, may be the value of F_CR at which pump 10 starts running while the system is in mode 2′ or in mode 3′. The value r_EO,D of r_EO is chosen so that $\begin{array}{cc}{r}_{\mathrm{EO},D}>\frac{1}{q_{\mathrm{EV},\mathrm{MAX}}}-1& \left(12\right)\end{array}$

[00755] iv. Other Refrigerant Configurations and Control Systems

[00756] It should be clear, from the teachings so far in this DESCRIPTION, that the class II_FN^ooo principal configuration shown in FIG. 46, and the class II_FF^ooo configurations shown in FIGS. 46A and 46B are only three of many kinds of principal configurations with an NP evaporator which may be preferred for cooling a particular piston engine. Other kinds of preferred principal configurations, in the case of type A combinations, include class II_FN^soo, II_FF^soo, II*_FN^ooo, II*FN^soo, III*_FN^oo, III*_FNso, III*_FF^oo, and III*_FF^so, configurations. (In refrigerant-circuit configurations with a subcooler, the subcooler would be located ahead of pump 10, or of pump 46, as applicable, and would—as in the case of configurations with a P evaporator—be merely a rudimentary subcooler.) I note that subgroup III_FN configurations are generally included in preferred configurations only where their condenser is higher than their evaporator.

[00757] All suitable principal configurations for piston-engine cooling systems with an NP evaporator must have sewer flow, or a substantial evaporator-overfeed ratio, or both. This is achieved in the case of subgroup II_FN and II_FF configurations in the way described in respectively sections V,F,2,b,ii and V,F,2,b,iii. I note that an alternative version of the class II_FF^ooo principal configuration shown in FIG. 46A would be the principal configuration shown in FIG. 46B where EO pump 27 has been added to the principal configuration shown in FIG. 46.

[00758] A substantial evaporator-overfeed ratio can also be obtained by operating the DR pump of subgroup III_FF and III*_FF configurations like the EO pump of a subgroup II_FF configuration; namely by operating DR pump 46 so that the volumetric-flow rate F_DR induced by it varies in a pre-prescribed way as a function of the volumetric-flow rate F_CR induced by CR pump 10.

[00759] The EO and DR pump control techniques described so far in this section V,F,2,b may often be unsatisfactory because of unacceptably large differences between the current value of {dot over (m)}_C and the current value of {dot over (m)}_V during transients, where {dot over (m)}_V is the mass-flow rate of essentially-dry refrigerant vapor in the principal configuration's refrigerant-vapor transfer means. In cases where such unacceptably large differences would occur, the EO and DR pump control techniques described so far can

• [00760] (a) be supplemented by techniques described in section V,H,4; or
• [00761] (b) be replaced (1) by the alternative control techniques also described in section V,H,4, or (2) by the dual flow-rate control technique described in the immediately-following major paragraph.

[00762] The last-cited control technique—which can, with obvious changes, be used with either an EO or a DR pump—is described in this major paragraph using as an example a system, hereinafter referred to in this major paragraph as ‘the system’, consisting of the class III*_FN^oo principal configuration, and the type IV_R ancillary configuration, shown in FIG. 49; CCU 527 shown in FIG. 50; and MPMCU 518 shown in FIG. 45.

[00763] The particular dual flow-rate control technique employed by the refrigerant configuration shown in FIG. 49 (1) uses refrigerant vapor-flow transducer 136 to generate a signal F′_V providing a measure of the current value of the refrigerant-vapor volumetric-flow rate F_V in the refrigerant configuration's refrigerant-vapor transfer means, and (2) uses liquid-refrigerant flow transducer 142 to generate a signal F′_DR providing a measure of the current value of the liquid-refrigerant volumetric-flow rate F_DR induced by DR pump 46. CCU 527

• [00764] (a) computes the refrigerant-vapor mass-flow rate {dot over (m)}_V, corresponding to F_V, where {dot over (m)}_V provides—under steady-state conditions—an accurate measure of ({dot over (m)}_E−{dot over (m)}_EO);
• [00765] (b) computes the liquid-refrigerant mass-flow rate {dot over (m)}_DR corresponding to F_DR; and
• [00766] (c) generates a signal C′_DR which controls DR pump 46 so that it induces a (liquid) volumetric-flow rate F_DR large enough to ensure the current value of r_EO is large enough for the current value of q_EV not to exceed q_EV,MAX.

[00767] In FIG. 49, numeral 528 designates a bidirectional (two-way) refrigerant-blocking valve having one or more refrigerant passages which are a part of a type 2 evaporator refrigerant auxiliary circuit and of no other refrigerant circuit. Valve 528 is controlled by signal C′_RBV.

[00768] The system has, like all systems of the invention discussed so far, four control modes (in the case of a non-azeotropic refrigerant) which I refer to, in general, as modes 0, 1, 2, and 3. (I use dashes, as in section V,F,2,b,iii, only where I need to distinguish between different versions of those control modes.) Briefly, to recapitulate, modes 0, 1, 2, and 3, designate modes I shall refer to respectively as a minimum-pressure-maintenance mode; a mixing mode; an RC heat-release mode; and a combined self-regulation and EC heat-release mode. (The term ‘mixing mode’ refers to the action of mixing the components of a non-azeotropic refrigerant to achieve a more spatially-uniform concentration of its components.) The system has four controllable elements: DR pump 46, LT pump 404, condenser fan 510, and refrigerant bidirectional valve 528.

[00769] In mode 0, pump 46 and fan 510 do not run; valve 528 is open; and MPMCU 518 ensures pump 404 is controlled so that p_R tends to p_RD^o.

[00770] In mode 1, CCU 527 ensures (1) pump 46 runs at a preselected capacity, usually near or equal to the pump's full capacity; (2) pump 404 is controlled so that p_R tends to p_RD; (3) fan 510 does not run; and (4) valve 528 is closed.

[00771] In mode 2, CCU 527 ensures (1) pump 46 is controlled so that q_EV does not exceed q_EV,MAX; (2) pump 404 is controlled so that p_R tends to p_RD; (3) fan 510 does not run; and (4) valve 528 is open.

[00772] In mode 3, CCU 527 ensures (1) pump 46 is controlled so that q_EV does not exceed q_EV,MAX; (2) pump 404 is controlled so that L_R tends to L_RD; (3) fan 510 is controlled so that p_R tends to p_RD; and (4) valve 528 is open.

[00773] The transition rules between the four modes recited in this major paragraph can be identical to those given in section V,F,2,a,iii.

[00774] I note that there is no identifiable liquid level in separating assembly 42*. Therefore, CCU 527 determines whether the refrigerant-circuit configuration shown in FIG. 49 is in a safe, or in an unsafe, state solely on the basis of relations (2), (3), (4), (6), (7), and (8).

[00775] I also note that the location of the inlet and outlet of the two-port ancillary configuration shown in FIG. 49 is correct for a two-component non-azeotropic refrigerant's component whose component with the lower freezing temperature also has the lower evaporation temperature. (See section V,F,2,d.)

[00776] I further note that, where the signal C′_DR used to control DR pump 46 provides a sufficiently accurate measure of F_DR, transducer 142 can be eliminated.

[00777] It should be clear from the teachings so far in this DESCRIPTION that a type II_R, type III_R, type IV_R, or type VI_R, ancillary configuration can be used instead of the type I_R ancillary configuration shown in FIGS. 46, 46A, 46B, and 49.

[00778] Shutter-controlled heat release can be used with a cooling system of the invention having an NP evaporator in the same way as with a cooling system of the invention having a P evaporator.

[00779] c. Location of Evaporator Refrigerant Inlets and Outlets

[00780] Everywhere in this DESCRIPTION I distinguish between NP-evaporator liquid-refrigerant inlets and P-evaporator liquid-refrigerant inlets, and between NP-evaporator refrigerant-vapor outlets and P-evaporator refrigerant-vapor outlets. And I also everywhere in this DESCRIPTION distinguish, where applicable, between cylinder-block evaporator (liquid-refrigerant) inlets and (refrigerant-) vapor outlets on the one hand, and cylinder-head evaporator (liquid-refrigerant) inlets and (refrigerant-) vapor outlets on the other hand, by adding to numerals designating cylinder-block evaporator inlets and vapor outlets a single-dash superscript, and by adding to numerals designating cylinder-head evaporator inlets and vapor outlets a double-dash superscript. I further distinguish in this section V,F (and I have already done this in FIGS. 46, 49, and 51A), and in section V,G, between different kinds of cylinder-block and cylinder-head inlets in the way described next, where the abbreviation NPE denotes an NP evaporator and the abbreviation PE denotes a P evaporator.

[00002]

Numeral
NPE	PE	Inlet Designated
2	82:	Inlet through which liquid refrigerant, exiting a principal
		configuration's (principal) condenser, and exiting the
		principal configuration's separating device, enters the
		principal configuration's evaporator
523	593:	Inlet through which essentially only liquid refrigerant
		exiting a principal configuration's separating device enters
		the principal configuration's evaporator
530	550:	Inlet through which essentially only liquid refrigerant
		exiting a principal configuration's (principal) condenser
		enters the principal configuration's evaporator

[00781] An evaporator liquid-refrigerant inlet, or an evaporator refrigerant-vapor outlet, may consist of one or more ports. In the case where that inlet, or that outlet, consists of several ports, the several ports may be located at the same level or at different levels.

[00782] I stated in section V,F,2,b,iii that liquid refrigerant may have to be supplied to several locations in the coolant passages of a bank of cylinders. This is true not only with the class II_FF^ooo principal configuration discussed in the last-cited section, but also with any principal configuration. Preferred locations depend not only on the orientation of a piston engine's bank of cylinders but also on design details such as the precise configuration of cylinder-block and cylinder-head coolant passages. Liquid refrigerant can be delivered to these passages by nozzles to increase the velocity with which liquid refrigerant is injected into them, thereby generating turbulence and eliminating hot spots. I shall refer to the last-cited nozzles as ‘liquid-refrigerant injection nozzles’ or more briefly as ‘LR injection nozzles’. I use numeral 531 to designate a set of one or more LR injection nozzles.

[00783] A typical example of LR injection-nozzle locations is given in FIG. 51 for the particular case of engine 500 with a single bank of cylinders, a class II_FF^ooo principal configuration, and a liquid-refrigerant inlet 2″ having a set of ports consisting of two subsets of ports on opposite sides of the engine's cylinder-head. Numeral 535 designates an ancillary configuration (of any type).

[00784] In the typical example shown in FIG. 51, the number of ports—and associated LR injection nozzles—in each subset of ports would typically be equal to the number of cylinders in the bank of cylinders, or to a multiple or a submultiple of the number of cylinders in the bank of cylinders. In the particular case where the number of ports, in each subset of ports, is equal to, or larger than, the number of cylinders in the bank of cylinders, refrigerant passages 505 can be subdivided—to help balance refrigerant flows in a cylinder bank's cylinder heads—into a set of several separate and distinct refrigerant passages. The number of these separate and distinct refrigerant passages, where used, can be equal to, or a multiple of, or a submultiple of, the number of cylinders in a cylinder bank, but must not exceed the number of ports in each subset of ports.

[00785] Turbulence promoters in the form of fins inside an engine's coolant passages, and/or in the form of grooves in the internal surfaces of those passages, are used by the invention, where desirable, to promote or to enhance turbulent refrigerant flow inside the engine's coolant passages.

[00786] The typical example shown in FIG. 51 assumes that refrigerant passages 504 (in the cylinder-block coolant passages) and refrigerant passages 505 (in the cylinder-head coolant passages) are interconnected through several ports (not shown), and that (refrigerant) sewer flow occurs in refrigerant passages 504. Sewer flow, in passages 504, may in many cases require the ports interconnecting passages 504 and 505 to be unacceptably large. In such cases, refrigerant-vapor transfer-means segment 3′-537 (consisting of one or more refrigerant lines) can be used (see FIG. 51A) to by-pass refrigerant vapor, generated in passages 504, around interconnecting ports 538.

[00787] d. Supplementary Control Techniques for Non-azeotropic Refrigerants

[00788] i. General Remarks

[00789] The refrigerants envisaged by me for piston-engine cooling and intercooling systems exposed to subfreezing water temperatures include azeotropic-like and non-azeotropic refrigerants. The former refrigerants include ethanol, methanol, acetone, HCFCs, and HFCs; and the latter include aqueous glycol, ethanol, methanol, and acetone, solutions.

[00790] Most of the non-azeotropic refrigerants I have in mind are—like the four last-cited solutions—two-component non-azeotropic refrigerants. I shall therefore, in this section V,F,2,d, consider only two-component non-azeotropic refrigerants. However, the techniques described in this same section also apply to non-azeotropic refrigerants with more than two components.

[00791] In the particular case of a two-component non-azeotropic refrigerant, the spatial distribution of the concentration of one of its components at a given point automatically determines the spatial distribution of the concentration of its other component at that point. I therefore need to consider the spatial distribution of the concentration of only one component.

[00792] Let c(x,y,z) be the concentration, at a point (x,y,z) of the liquid phase of the refrigerant's component with the higher evaporation (boiling) temperature (at a given pressure); let c be the concentration of the liquid phase of that component when its concentration is spatially uniform throughout a refrigerant-circuit configuration; and let {overscore (c)}_E(x,y,z), or more briefly {overscore (c)}_E, be the mean value of the concentration of the liquid phase of that component in the configurations evaporator. Then, while a principal configuration is active, the value of {overscore (c)}_E will in general exceed the value of c, and consequently the mean value {overscore (T)}_RS,E (of the refrigerant's saturated-vapor temperature T_RS in a configuration's evaporator) will exceed the value of the refrigerant's saturated-vapor temperature T_RS,O corresponding to the value of c. The difference ({overscore (T)}_RS,E−T_RS,O), if substantial, is undesirable, and I have therefore devised supplementary control techniques for reducing it. I distinguish between two-component non-azeotropic refrigerants, which I shall refer to as ‘group H refrigerants’, whose component with the lower freezing temperature has—as in aqueous glycol solutions—the higher evaporation temperature; and other two-component non-azeotropic refrigerants, which I shall refer to as ‘group L refrigerants’, whose component with the lower freezing temperature has—as in ethanol, methanol, and acetone, solutions—the lower evaporation temperature. I also note that the foregoing supplementary control techniques are essentially, but not necessarily exactly, the same for both group H and group L refrigerants.

[00793] ii. Cooling Systems with no Evaporator Refrigerant Auxiliary Circuit

[00794] In the just-cited case, the value of {overscore (c)}_E−c) depends, for a given refrigerant and a given evaporator-overfeed ratio r_EO, on the value of the ratio $\begin{array}{cc}{r}_M\equiv \frac{M_E}{M_L},& \left(13\right)\end{array}$
and decreases as r_M increases. In relation (13), M_E is the mass of liquid refrigerant in the evaporator and M_L is the mass of liquid refrigerant in the principal configuration outside the evaporator.

[00796] The value of ({overscore (c)}_E−c), and the corresponding value of {overscore (T)}_RS,E (at a given refrigerant pressure), may be acceptable, for certain two-component non-azeotropic refrigerants, for values of r_M as low as unity—even where the evaporator-overfeed ratio is high. Examples of such two-component refrigerants are those which—like aqueous ethanol solutions—have component evaporation temperatures which do not differ greatly. (The boiling temperature at standard pressure of water and ethanol are respectively 100° C. and 77.7° C., and therefore differ by only 22.3° C.) By contrast, the value of {overscore (c)}_E, and the corresponding value of {overscore (T)}_RS,E, may not be acceptable for certain other two-component non-azeotropic refrigerants, even for values of r_M as high as 3 or even higher—even where the evaporator-overfeed ratio is high. Examples of such two-component non-azeotropic fluids are ethylene glycol solutions and propylene glycol solutions. (The evaporation temperature, at standard pressure, of the former solution is 198° C. and of the latter solution is 187° C., and therefore these two temperatures differ from the boiling temperature of water by 98° C. and 87° C., respectively.) I consider as an example, in greater detail, a spatially uniform concentration of ethylene glycol equal to 0.5. Then, when r_M is equal to unity, the value of ({overscore (c)}_c−c) is, with a high value of r_EO (say over 10), about 0.34, which at one atmosphere corresponds to a value of {overscore (c)}_E of about 0.84 and to a value of {overscore (T)}_RS,E of about 127° C. This temperature corresponds to an often undesirably-high rise in temperature above the boiling temperature of water at standard atmospheric pressure. With a design I have in mind, I expect the value of r_M to be as high as 7 while some piston-engine cooling systems of the invention are in mode 3. This value corresponds, for c equal to 0.5, to a value of {overscore (c)}_E equal to about 0.57, and to values of {overscore (T)}_RS,E of about 109° C. and 105° C. at respectively one atmosphere and 0.8 atmosphere. This is usually acceptable. By contrast, when the system is in mode 2 and the system's condenser is almost completely filled with liquid refrigerant, the value of r_M may approach unity and {overscore (T)}_RS,E may approach 127° C. at one atmosphere, which is usually undesirable. I have therefore devised the techniques disclosed next to reduce, where necessary, the value of {overscore (c)}_E and {overscore (T)}_RS,E while the system is in mode 2. (These techniques can also be used for the same purpose in mode 3 at the expense of a larger condenser.)

[00797] All the techniques devised by me for reducing the concentration {overscore (c)}_E and the temperature {overscore (T)}_RS,E are based on the fact that, for a given value of r_M, the value of {overscore (c)}_E decreases as the value of the ratio q_CV decreases, where $\begin{array}{cc}{q}_{\mathrm{CV}}=\frac{{\stackrel{\circ }{m}}_V}{{\stackrel{\circ }{m}}_V+{\stackrel{\circ }{m}}_L}=\frac{1}{1+\left({\stackrel{\circ }{m}}_L/{\stackrel{\circ }{m}}_V\right)}=\frac{1}{1+r_{\mathrm{CO}}};& \left(14\right)\end{array}$
where q_CV, {dot over (m)}_V, and {dot over (m)}_L, are respectively the quality of refrigerant vapor, the mass-flow rate of dry refrigerant vapor, and the mass-flow rate of liquid refrigerant, entering condenser 508 at refrigerant inlet 5; and where $\begin{array}{cc}{r}_{\mathrm{CO}}=\frac{{\stackrel{\circ }{m}}_L}{{\stackrel{\circ }{m}}_V}& \left(15\right)\end{array}$
is a ratio I shall refer to as the ‘condenser-overfeed ratio’.

[00800] The purpose of separator 21 is to ensure the value of {dot over (m)}_L is essentially zero in mode 3. However, the purpose of operating the engine-cooling system in mode 2 is to decrease condenser effectiveness. This was achieved with the techniques described in sections V,F,2,b, and V,F,2,c, by backing-up liquid refrigerant in condenser refrigerant passages 399. Because condenser effectiveness decreases as r_CO increases, the same result can be achieved by causing liquid refrigerant to enter passages 399 through condenser refrigerant inlet 5 instead of through condenser refrigerant outlet 6. This second way of decreasing condenser effectiveness decreases the value of {overscore (c)}_E for a given value of r_M, thereby also decreasing the value of {overscore (T)}_E for a given value of p_R. The value of {dot over (m)}_L can be made to have a substantial value with several techniques.

[00801] The first set of techniques for achieving a required value of r_M includes using a liquid-level independent-control technique to raise the level L_P of interface surface 123 sufficiently for, as applicable, separator 21, separating assembly 21*, or separating assembly 42*, to become ineffective and cause wet refrigerant, instead of essentially dry refrigerant, to be supplied to air-cooled condenser 508. To this end, the value L_PD3 of L_PD in mode 3 would still be chosen low enough for separator 21, separating assembly 21*, or separating assembly 42*, to supply essentially dry refrigerant to condenser refrigerant passages 399, but the value L_PD2 of L_PD in mode 2 would be chosen high enough to cause separator 21, separating assembly 21*, or separating assembly 42*, to become sufficiently ineffective for the ratio r_CO to tend toward a value high enough to prevent the value of {overscore (c)}_E, or of {overscore (T)}_RS,E, exceeding a preselected maximum value. A measure of {overscore (c)}_E can be obtained by measuring the value of c_E inside refrigerant passages 505 at a point below interface surface 123, and a measure of {overscore (T)}_RS,E can be obtained by measuring the refrigerant temperature T_R also at a point in refrigerant passages 505 below that interface surface. Then, for example, in the case of the subgroup VIII_FN, VIII_FF, II_FN and II_FF, configurations shown in respectively FIGS. 43, 43E, 46, and 46A or 46B, CR pump 10 could, for instance, be controlled so that
T_R−T_RS,O≦ε_RS,  (16)
where the value of T_RS,O, as a function of the values of T_R and c, can be computed for a given refrigerant and stored in a system's CCU; where ε_RS is a preselected positive quantity equal to a few degrees Celsius; and where LT pump 404 would usually be controlled so that p_R tends to p_RD.

[00804] The second set of techniques for achieving a required value of {dot over (m)}_L includes by-passing, as applicable, separator 21, separating assembly 21*, or separating assembly 42*, with a liquid-refrigerant line connecting directly liquid refrigerant in refrigerant passages 504, or refrigerant passages 505, at a point below interface surface 123, to a point of refrigerant-vapor line 23-5, or to a point of condenser header 507; and to cause liquid refrigerant to flow in that liquid-refrigerant line when the engine-cooling system is in mode 2. This can be done in several ways. One of these ways is shown in FIG. 43I for the case of a principal configuration having a type 1 separator. In FIG. 43I, condenser-overfeed pump 539, or more briefly CO pump 539, having an inlet 540 and an outlet 541, and liquid-refrigerant lines 542-540 and 541-543, are used to transfer liquid refrigerant from refrigerant passages 505 to refrigerant-vapor line 23-5 (or to header 507), after by-passing separator 21. CO pump 539 is used to control the rate {dot over (m)}_L by inducing a volumetric-flow rate F_CO. While the engine-cooling system is in mode 2, LT pump 404 is controlled so that L_R tends so L_RD, CR pump 10 is controlled so that L_P tends to L_PD, and CO pump 539 can again be controlled so that relation (16) is satisfied. Alternatively, CO pump 539 can be controlled so that
r_CO≧r_CO,MIN  (17)
where r_CO,MIN is a precomputed quantity, not necessarily fixed, stored in the cooling system's CCU (not shown). (For example, r_CO,MIN may be a function of p_R.) To this end, the cooling system's CCU determines the current value of {dot over (m)}_V from a signal F′_V generated by refrigerant vapor-flow transducer 136, and the cooling system's CCU generates a signal C′_CO which controls pump 539 so that
{dot over (m)}_L≧{dot over (m)}_V·r_CO,MIN  (18)

[00808] iii. Cooling Systems with an Evaporator Refrigerant Auxiliary Circuit

[00809] In the just-cited case, the values of ({overscore (c)}_EA−c) and ({overscore (T)}_RS,EA−T_RS,O) depend, for a given refrigerant and a given evaporator-overfeed ratio r_E,O, on the value of the ratio $\begin{array}{cc}{r}_{\mathrm{MA}}\equiv \frac{M_{\mathrm{EA}}}{M_{\mathrm{LA}}}& \left(19\right)\end{array}$
and decrease as r_MA increases. In the expression ({overscore (c)}_EA−c), the quantity {overscore (c)}_EA is the mean value of the concentration c_EA, in a principal configuration's evaporator refrigerant auxiliary circuit, of the liquid phase of the refrigerant's component with the higher evaporation temperature in the expression ({overscore (T)}_RS,EA−T_RS,O); the quantity {overscore (T)}_RS,EA is the mean value of the refrigerant saturated-vapor temperature T_RS in the principal configuration's evaporator refrigerant auxiliary circuit; and in relation (19), M_EA is the mass of liquid refrigerant in the evaporator refrigerant auxiliary circuit, and M_LA is the mass of liquid refrigerant in the principal configuration outside that auxiliary circuit.

[00811] The ratio r_MA is—like the ratio r_M—expected usually to be sufficiently high while the engine-cooling system is in mode 3, but not high enough while the system is in mode 2, and I have therefore devised several sets of techniques, similar to those devised for the case of cooling systems with P evaporators, to reduce, where necessary, the values of {overscore (c)}_EA and {overscore (T)}_RS,EA while engine-cooling systems with an NP evaporator are in mode 2. I next describe only essential differences between the two sets of techniques.

[00812] The essential difference between the first set of supplementary control techniques devised for engine-cooling systems with a P evaporator and the first set of supplementary control techniques devised for engine-cooling systems with an NP evaporator, is that in the former systems the effectiveness of, as applicable, separator 21, separating assembly 21*, or separating assembly 42*, is reduced indirectly by raising the level of liquid refrigerant in their P evaporator; whereas in the latter systems the effectiveness of separator 21 is reduced directly by raising the level of liquid refrigerant in their separator.

[00813] The essential difference, between the second set of supplementary control techniques devised for engine-cooling systems with a P evaporator and the second set of supplementary control techniques devised for engine-cooling systems with an NP evaporator, is that in the former systems liquid refrigerant is transferred to a point of refrigerant (vapor) line 23-5, or of condenser header 507, from the evaporator; whereas in the latter systems liquid refrigerant is transferred to that line, or to that header, from—as applicable—separator 21, liquid-refrigerant line 24-25, refrigerant line 21*-25, or refrigerant line 45*-49. FIG. 46C shows, for the case of a principal configuration with a type 1 separator, CO pump 539, and refrigerant lines 545-540 and 541-546, used to transfer liquid from point 545 of separator 21 to point 546 of refrigerant line 23-5.

[heading-00814] e. Location of Inlet and Outlet Ports of Two-port Ancillary Configurations

[00815] The supplementary control techniques disclosed in section V,F,2,d are, as mentioned in that section, essentially the same for group H and group L refrigerants. However, the control techniques, for helping ensure the concentration of the components of a two-component non-azeotropic refrigerant are spatially quasi-uniform throughout a cooling system's configuration before it cools down, depend in part on whether the refrigerant is a group H or a group L refrigerant. The reason for this is that

• [00816] (a) in the case of a P evaporator, the concentration of the component of the refrigerant with the lower freezing temperature, which I shall refer to as the freeze-proof component, will be high in the evaporator and low outside the evaporator where a group H refrigerant is employed;

[00817] whereas that concentration will be low in the evaporator and high outside the evaporator where a group L refrigerant is employed; and similarly

• [00818] (b) in the case of an NP evaporator (with a substantial amount of overfeed), the concentration of the freeze-proof component will be high in the evaporator refrigerant auxiliary circuit and low outside that circuit where a group H refrigerant is employed; whereas that concentration will be low in the evaporator refrigerant auxiliary circuit and high outside that circuit where a group L refrigerant is employed.

[00819] It follows that a two-port ancillary configuration should preferably usually be connected to the principal configuration associated with it, so that

• [00820] (a) with a group H refrigerant, the ancillary configuration extracts liquid refrigerant from all appropriate point of the principal configuration's evaporator refrigerant auxiliary circuit and inserts liquid refrigerant at an appropriate point of the principal configuration outside that circuit; and so that
• [00821] (b) with a group L refrigerant, the ancillary configuration extracts liquid refrigerant from an appropriate point of the principal configuration outside the evaporator refrigerant auxiliary circuit and inserts liquid refrigerant at an appropriate point inside that circuit.
  The former of the two cases just cited under (a) and (b) is shown, for example, in FIG. 43H; and the latter of these same two cases is shown, for example, in FIG. 49.

[00823] It also follows that a one-port ancillary configuration should preferably usually be connected, to the principal configuration associated with it, so that

• [00824] (a) with a group H refrigerant, the ancillary configuration extracts liquid refrigerant from an appropriate point of the principal configuration's evaporator refrigerant auxiliary circuit; and so that
• [00825] (b) with a group L refrigerant, the ancillary configuration extracts liquid refrigerant at an appropriate point of the principal configuration outside the evaporator refrigerant auxiliary circuit.
  The former of the two cases just cited under (a) and (b) is shown, for example, in FIG. 43G; and the latter of these same two cases is shown, for example, in FIGS. 43 and 46.

[00827] f. Vehicle-tilt Compensating Techniques

[00828] i. Preliminary Remarks

[00829] Piston-engine cooling systems having an NP evaporator can be designed so that their performance is not affected adversely during large tilts, with respect to a local horizontal plane, of the vehicle on which they are installed. For example, such cooling systems can be made immune to tilts of up to at least 30 degrees, in any direction, where, as applicable, their separator has, or their receiver is, in the absence of tilt, a vertical cylindrical vessel with a length-to-diameter ratio of, say, no less than 2. By contrast, the performance of cooling systems having a P evaporator, a shallow separator, or a shallow receiver, may be affected adversely by tilts of 15 degrees or less. I use the term ‘shallow’ to denote, in the case of a vertical cylindrical vessel, a length to diameter ratio of less than one.

[00830] In the case of automobiles designed for road-only service, and in the case of ships, tilts exceeding, say, 15 degrees are, while the engine is running, unusual for long time intervals, but may occur for short time intervals. For such short time intervals (say less than one minute), I have devised the vehicle-tilt compensating techniques, described in the next two subsections of this section V,F,2,f, for two-phase engine-cooling systems with a P evaporator, an NP evaporator and a shallow separator, or with a shallow receiver.

[00831] ii. Cooling Systems with a Pool Evaporator

[00832] The vehicle-tilt compensating techniques devised for cooling systems with a P evaporator are based on the premise that whereas potential hot spots of the walls of cylinder-head passages 505 must remain immersed continuously in liquid refrigerant, a temporary degradation in cooling-system performance is acceptable if it causes the temperature of liquid refrigerant in passages 505 to rise temporarily by only a few degrees Celsius. The last-cited techniques are disclosed using the refrigerant configuration shown in FIG. 43.

[00833] I assume, for specificity only, that the one or more cylinder axes of the engine being cooled are vertical when the vehicle on which the engine is mounted is placed on a horizontal surface, and that therefore the angle θ of the cylinder axes, with respect to the normal to interface surface 123 (see FIG. 43), is equal to the vehicle tilt angle with respect to a local horizontal plane. And I use the letter φ to designate the azimuth angle of the vertical plane, containing the angle θ, with respect to a vertical plane fixed to the engine.

[00834] The value L_P,MIN of L_P at which potential hot spots of the walls of refrigerant passages 505 remain just immersed in liquid refrigerant is a function of 0 which, in general, is in turn a function of φ or, in symbols
L_{P, MIN}=L_P,MIN {θ(φ)}  (20)
Relation (20) is stored in the engine-cooling system's CCU. This CCU uses relation (20) to compute a current value L_PD high enough for L_P to stay above L_P,MIN, and then generates a signal L′_P which controls CR pump 10 so that L_P tends to L_PD.
This action will ensure the potential hot spots cited earlier remain immersed in liquid refrigerant at the expense of a degradation in cooling-system performance whenever the level of interface surface 123 rises sufficiently for separator 21 to be unable to deliver essentially dry refrigerant vapor to condenser 508.

[00838] Suitable tilt transducers include two inclinometers at right angles to each other in a plane, fixed to the engine, which is horizontal when the engine's cylinder axes are vertical. Typical examples of inclinometers are LVDT-type transducers. Inclinometers 548 and 549 (see FIG. 43K which is a perspective view of cylinder-head 503 shown in FIG. 43) generate signals θ′₁ and θ′₂, respectively, providing measures of their inclinations with respect to a local horizontal plane.

[00839] In cases where tilt in only one vertical plane is of interest only one inclinometer is used. The signal generated by it could, in some applications, only be a two-step, or at most a three-step signal.

[00840] iii. Cooling Systems with a Non-pool Evaporator and Shallow (Type 1) Separator Having Vapor Inlets Below Liquid Level

[00841] The vehicle-tilt compensating techniques devised for cooling systems with an NP evaporator and with a shallow separator, and in particular with a shallow type 1 separator, having a set of one or more vapor inlets below interface surface 521, are similar to those devised for cooling systems having a P evaporator. Namely, the techniques devised to ensure the potential hot spots of the walls of a P evaporator remain immersed in liquid refrigerant during vehicle tilts are used to ensure the last-cited separator's set of vapor ports remains covered by liquid refrigerant during those tilts. The only essential difference is that signals θ′₁ and θ′₂ provide measures of the inclination, with respect to a local horizontal plane, of separator 21, and not of the inclination of a bank of cylinders which may, as in the case of a V engine, have a different inclination from another bank of cylinders of the same engine. FIG. 46D shows transducers 548 and 549 mounted oil separator 21.

[00842] g. Cabin-heating

[00843] Cabin heating, when desired, can be performed by using one or more refrigerant circuits which are an integral part of the refrigerant configuration used to cool an internal-combustion piston engine. This can be done in several ways which can be divided into two sets: ways which use single-phase heat-transfer and ways which use two-phase heat-transfer.

[00844] In the former case, the class VIII_FN^ooo configuration shown in FIG. 43, the class VIII_FF^ooo configuration shown in FIG. 43F, the class II_FN^ooo principal configuration shown in FIG. 46, and the class II_FF^ooo configuration shown in FIG. 46A or in FIG. 46B, become respectively class XI_FN^ooo, class XI_FF^ooo, class V_FN^ooo, and class V_FF^ooo, configurations with a non-interactive-type subcooler refrigerant auxiliary circuit, or more briefly an NI-type subcooler refrigerant auxiliary circuit. And, in the latter case, the refrigerant configurations shown in FIGS. 43, 43F, 46, 46A, and 46B, become split principal configurations with two branches sharing the same evaporator, but having different condensers.

[00845] In the cabin-heating refrigerant circuits described next, I shall use alphanumeric symbols to denote components and points. The numeral in these symbols, where already used in this DESCRIPTION, designates the same kind of component as, or the corresponding point to, respectively the component, or the point, already designated by that numeral in this DESCRIPTION; and the letter ‘h’ in those alphanumeric symbols signifies that those symbols designate a component or a point belonging either exclusively or primarily to a cabin-heating circuit.

[00846] An example of a cabin-heating circuit employing an NI subcooler refrigerant auxiliary circuit is shown in FIG. 43L for the case where an engine-cooling system has a P evaporator. In this figure, liquid refrigerant exits cylinder-head refrigerant passages 505 at 87h, enters SC pump 63h at 64h and exits at 65h, enters cabin-heating air-cooled subcooler 551h at 72h and exits at 73h, and is returned to the refrigerant passages 505 at 88h. Because an NI subcooler auxiliary circuit is, by definition, a single-phase circuit, it can, together with associated subcooler fan 552h, be operated in any one of the known ways used with cabin-heating systems employing, as their heat-transfer fluid, the coolant of a piston-engine single-phase cooling system.

[00847] An example of a cabin-heating circuit employing an NI subcooler refrigerant auxiliary circuit is shown in FIG. 46E for the case where an engine-cooling system has an NP evaporator. The subcooler refrigerant auxiliary circuit is the same as that shown in FIG. 43L; except that point 771h at which liquid refrigerant enters the circuit, and point 78h at which liquid refrigerant exits the circuit, are points of separator 21 instead of points of refrigerant passages 505.

[00848] I note that the subcooler refrigerant auxiliary circuit shown in FIG. 46E could also have been added to separator 21 in FIG. 46A or in FIG. 46B.

[00849] I also note that SC pump 63h can also be used to perform the function of a CO pump. To this end, outlet 73h of subcooler 551h is connected, whenever required, to a point of the refrigerant principal circuit between, as applicable, separator vapor outlet 23, separator vapor outlet 44, separating-assembly vapor outlet 23*, or separating-assembly vapor outlet 44*, on the one hand; and condenser refrigerant passages 399 on the other hand. FIG. 46F shows a way of doing this using the class II_FN^ooo principal configuration shown in FIG. 46 as an example. In FIG. 46F, numeral 555 designates a (three-way) liquid-refrigerant diverter valve having an inlet 556, outlet 557, and outlet 558. Valve 555 is controlled by signal C′_RDV1, generated by the configuration's CCU (not shown) so that the valve supplies, as required, liquid refrigerant to outlet 557 or to outlet 558. Outlet 558 is connected to point 559 of refrigerant-vapor line 23-5 by liquid-refrigerant line 558-559.

[00850] An example of one or more cabin-heating circuits which are a branch of a split principal configuration, with two parallel branches sharing the selfsame P evaporator, is shown in FIG. 43M. The cabin-heating branch of the split principal configuration shown in FIG. 43M can be thought of as belonging conceptually to a class VIII_FN^ooo (principal) configuration which includes separator 21h, condenser 508h, and CR pump 10h. Because the cabin-heating branch of the split principal configuration has a type 1 separator, pump 10h can, while the cabin-heating branch is active, be controlled as a two-step, as well as a continuous, function of the level L_Rh of liquid-vapor interface surface 116h in receiver 7h. In the former case, the engine-cooling system's CCU uses signal L′_Rh supplied by liquid-level transducer 113h to generate a signal C′_CRh which

• [00851] (a) starts pump 10h running whenever L_Rh rises above a first preselected level L_Rh2 and keeps pump 10h running while L_Rh stays at or above a second preselected level L_Rh1 lower than L_Rh2; and
• [00852] (b) stops pump 10h running whenever L_Rh falls below L_Rh1 and keeps pump 10h not running while L_Rh stays at or below L_Rh1.
  And, in the latter case, CCU 513 generates a signal C′_CRh which—in addition to the actions recited under (a) and (b) in this paragraph—
• [00854] (c) changes, while pump 10h is running, the pump's effective capacity F_CRh so that F_CRh increases when L_Rh increases and, conversely, so that F_CRh decreases when L_Rh decreases.
  The cabin-heating heat-transfer circuit may be activated and deactivated manually or automatically by a thermostat which senses cabin temperature and is set to a desired preselected temperature.

[00856] An example of one or more cabin-heating circuits, which are a branch of a split principal configuration with two parallel branches sharing the selfsame NP evaporator and the selfsame separator, is shown in FIG. 46G. The cabin-heating branch of the split principal configuration shown in FIG. 46G can be thought of as a class I_F^o configuration. Because the refrigerant vapor supplied by separator 21 at 553h is essentially dry, CR pump 10h (in FIG. 46G) can be controlled effectively as a function of L_R by a signal C′_CRh, supplied by the engine-cooling system's CCU. This CCU would then control pump 10h in the way described under (a), (b), and (c), in the immediately-preceding minor paragraph.

[00857] I note that a cabin-heating branch, using two-phase heat transfer, could use other refrigerant circuits; and, in particular, (1) refrigerant circuits with a constant-capacity DR pump, or (2) a natural refrigerant-circulation circuit, with a refrigerant valve, where interface surface 116h is above interface surface 521.

[heading-00858] 3. Intercooling Systems with an Air-cooled Condenser

[00859] a. General Remarks

[00860] Certain internal-combustion piston engines use a supercharger, which may be either a mechanically-driven supercharger or a turbocharger. The efficiency and shaft power of such engines can be, and has been, increased by intercooling; namely by cooling the compressed air discharged by a supercharger before it is supplied to the engine's one or more combustion chambers.

[00861] Intercoolers of the present invention may, like prior-art intercoolers, be independent of (namely separate and distinct from) a piston-engine's cooling system, or be an integral part of a piston-engine's cooling system. Independent intercoolers are generally preferred because they can be used to lower the air delivered, by a piston-engine's supercharger to the engine's cylinders, below the temperature of the engine's coolant. However, intercoolers which are an integral part of a piston-engine's cooling system, in the sense that they share the system's condenser, are within the scope of the invention disclosed in this DESCRIPTION. Such intercoolers would be a branch of a split principal configuration with two branches sharing the radiator (condenser) of the engine being intercooled.

[00862] At this time (1991), an aqueous ethylene glycol solution is the generally preferred refrigerant for single-phase piston-engine cooling systems exposed to temperatures below zero degrees Celsius; and is one of the preferred refrigerants for two-phase piston-engine cooling systems exposed to such temperatures. By contrast, the generally preferred refrigerant for cooling compressed air discharged by the supercharger of a piston engine is often not an aqueous ethylene (or an aqueous propylene) glycol solution. The reason for this is that it is often desirable to cool the air discharged by such a supercharger down to at least 60° C. with a refrigerant that boils, at acceptable absolute pressures, down to at least 55° C. Minimum acceptable refrigerant absolute pressures for intercooling are considerably lower than those for piston-engine cooling primarily because of the absence of cylinder-head gaskets. Nevertheless, I expect the cost of an intercooler to start rising rapidly as the minimum pressure, to which the system's principal configuration is subjected, falls below about 0.5 bar. The temperature at which an aqueous 50% ethylene or propylene glycol solution starts to boil exceeds 70° C. at even 0.3 bar. Consequently, refrigerants with lower boiling points than those of aqueous ethylene and propylene glycol solutions may be preferable for independent intercoolers.

[00863] Suitable refrigerants in freezing climates for independent intercoolers with a minimum-pressure-maintenance capability include ethanol, methanol, acetone, and their aqueous solutions.

[00864] The purpose of an intercooler is to maintain the temperature T_Iⁱ of air exiting the intercooler and supplied to the engine's cylinders, at a preselected desired temperature T_IDⁱ; where T_IDⁱ may have a fixed value or may have a value which varies in a pre-prescribed way as a function of one or more preselected parameters which include ambient air temperature, ambient air pressure, supercharger-output air temperature, supercharger-output air pressure, and parameters characterizing the state of the engine.

[00865] Where no minimum-pressure-maintenance and no refrigerant-controlled heat-release capabilities are required, several of the refrigerant-circuit configurations and control techniques disclosed in my co-pending U.S. patent application Ser. No. 400,738, filed 30 Aug. 1989, can be used for piston-engine intercoolers.

[00866] I would mention that, particularly where a non-azeotropic refrigerant is used, it is sometimes desirable to confirm that the intercooler's principal configuration is filled completely with liquid refrigerant. Several methods can be used to do this. A first of those several methods is to use a two-step liquid-level transducer at the highest point of the principal configuration, and to determine whether liquid refrigerant has reached that transducer, but this first method is impracticable for intercoolers subjected to substantial tilts. A second of those several methods, which is also applicable to intercoolers subjected to substantial tilts, is to use an absolute-pressure transducer to obtain a measure of refrigerant pressure, and a refrigerant-temperature transducer in the same neighborhood to obtain a measure of refrigerant (sensible) temperature; to compute the refrigerant saturated-vapor temperature corresponding to the measured refrigerant pressure; to compare the measured refrigerant sensible temperature and the computed refrigerant saturated-vapor temperature; and to use the fact that the latter temperature exceeds the former temperature by a preselected amount as confirmation that the principal configuration is completely filled with liquid refrigerant.

[00867] Preferred intercoolers of the invention usually have NP evaporators. I note that a substantial evaporator-overfeed ratio is not needed to prevent hot spots in the evaporator refrigerant passages of an intercooler; and is usually also not needed to prevent, in the case of a non-azeotropic refrigerant, a refrigerant saturated-vapor temperature rise in those passages. The reason for this is that such a temperature rise usually has no adverse effect comparable to that which would be caused by it if it occurred in a piston-engine's coolant passages. Consequently, preferred principal configurations for piston-engine intercoolers of the invention need not include means for overfeeding their evaporator. Therefore, in principle, any group I to III, VII to IX, II*, III*, VIII*, or IX*, configuration, usually with a refrigerant principal pump, and no preheater, superheater, or desuperheater, might be a preferred principal configuration.

[00868] b. A Fast-response Intercooler

[00869] I shall describe typical ways of operating an independent fast-response intercooler using

• [00870] (a) a type A combination employing, as an example (see FIG. 52), a class II_FN^ooo principal configuration, a type I_R ancillary configuration, and a non-azeotropic refrigerant; and
• [00871] (b) CCU 563 (see FIG. 53), and MPMCU 518 (see FIG. 45).

[00872] The numeral in the alphanumeric symbols used in FIG. 52 indicates the type of component, or the nature of the point, designated by those symbols, and the letter ‘i’ in those symbols indicates that the component or the point designated pertains to an intercooler. In particular, symbol 560i in FIG. 52 designates a section of a piston engine's air-intake conduit in which the intercooler's evaporator is located. That section is located downstream—with respect to the direction of air flow—from the engine's supercharger and upstream from the engine's air-intake manifold. Symbol 561i designates the intercooler's air-heated evaporator, and symbol 562i designates an air-intake temperature transducer which generates a signal T′_Iⁱ providing a measure of the temperature of the intake air after it has passed through evaporator 561i. Each numeral in FIG. 52, where it has been used earlier in this DESCRIPTION, designates the same component or the same point as that designated by the same numeral earlier. Thus, the numeral 2 in symbol 2i designates the refrigerant inlet of an NP evaporator and 508 in symbol 508i designates an air-cooled condenser. Similarly, each symbol representing a signal, or a quantity corresponding to that signal, designates the same signal or the same quantity as that designated by the same symbol where it has been used earlier in this DESCRIPTION without the superscript ‘i’. The superscript ‘i’ in those symbols indicates that the signal, or the quantity, designated pertains to an intercooler. Thus, for example, the symbol p′_R in the symbol p′_Rⁱ designates a signal generated by transducer 514i providing a measure of the current value of the refrigerant pressure p_Rⁱ at a preselected location of an intercooler's principal configuration.

[00873] I note that the rise in the intake-air temperature entering an intercooler's evaporator can be very rapid just after the supercharger starts operating, and therefore that the intercooler—if it were completely filled with liquid refrigerant while the engine is running and the supercharger is not running—would often not be able to reach mode 3 fast enough to maintain T_Iⁱ at its preselected desired value T_IDⁱ unless, as applicable, pump 404, motor 413, air-transfer pump 420, or hydraulic pump 422, is unacceptably large. Consequently, the invention includes, where desirable, means for preventing the refrigerant pressure of an intercooler using a type A (or incidentally also a type B) combination from falling below a preselected minimum value—while the engine is running and the supercharger is not running—without requiring the combination's principal configuration to be filled completely with liquid refrigerant. To this end, I use heat available in the engine's exhaust. (I could alternatively use an electric heating element. This, however, would consume a substantial amount of utilizable power whereas using exhaust-gas heat does not.)

[00874] Many piston engines have means for heating their intake air with their exhaust gases during cold weather. Instead of using the exhaust gases of a piston engine to heat its intake air directly, I use those gases to heat its intake air indirectly through the engine's intercooler by heating a refrigerant-circuit segment of its principal configuration. I can thus achieve minimum-pressure maintenance with a principal configuration only filled partially with liquid refrigerant while, at the same time, transferring heat to the engine's intake air through the intercooler's principal configuration.

[00875] FIG. 52 shows the particular case where the refrigerant-circuit segment healed by the engine's exhaust gases, which I shall refer to as the heated segment, is a segment of liquid-refrigerant auxiliary transfer means 24i-25i. In FIG. 52, exhaust gas from pipe 565 is drawn off at 566i, at a rate controlled by exhaust-gas damper 567i, and returned to pipe 565 at a point 568i, downstream from point 566i, after passing through segment 569i-570i containing heated segment 571i.

[00876] In FIG. 52, refrigerant-circuit segment 572i-573i is a segment of liquid-refrigerant auxiliary transfer means 24i-25i with a sufficiently large cross-sectional area for the level L_X of refrigerant liquid-vapor interface surface 574i in that segment to be detectable by three-step liquid-level transducer 575i. Transducer 575i generates a signal L′_Xⁱ indicating whether L_Xⁱ is between two preselected fixed levels in segment 592i-573i. The preselected desired value L_XDⁱ of L_Xⁱ, is any value between those fixed levels. A proportional liquid-level transducer, can be used instead of a three-step liquid-level transducer.) The segment of transfer means 24i-25i between enlarged segment 572i and separator port 24i has a cross-sectional area sized for sewer flow.

[00877] In FIG. 52, numeral 576i designates a three-step liquid-level transducer indicating whether the level L_Cⁱ of refrigerant liquid-vapor interface surface 577i in condenser 508i is within two preselected fixed levels in condenser header 507i. The preselected desired value L_CDⁱ of L_Cⁱ is any value between those two fixed levels. A proportional liquid-level transducer, can be used instead of a two-step liquid-level transducer.)

[00878] I now describe a first typical control technique for reducing the response time of the heat-transfer rate of an intercooler of the invention, immediately after the supercharger (with which the intercooler is associated) starts running, by utilizing heat from the engine's exhaust gases. To this end, while the engine is running and the supercharger is not running, I use heat from the engine's exhaust gases to allow minimum-pressure maintenance to be achieved with no liquid-refrigerant in refrigerant-vapor transfer-means segment 23i-5i, and with the value of L_Cⁱ equal to L_CDⁱ. This ensures the intercooler (1) can start releasing heat, without significant delay, when the supercharger starts running (provided the engine has been running for a few seconds, or at most for a few tens of seconds, before the supercharger starts running); and (2) can change to mode 3 much faster than it could if the refrigerant circuits of the intercooler's principal configuration were filled completely with liquid refrigerant.

[00879] I shall, in this section V,F,3,b, refer (1) to the intercooler shown in FIGS. 52, 53, and 45, as ‘the intercooler’; (2) to the supercharger discharging the compressed air cooled by the intercooler as ‘the supercharger’; and (3) to the engine driving the supercharger as ‘the engine’.

[00880] The intercooler has five control modes: control modes 0_E, 0_S, 1, 2, and 3. Control modes 1, 2, and 3, designate—as in the case of engine-cooling systems—respectively a mixing mode (used only with non-azeotropic refrigerants); an RC heat-release mode; and a combined self-regulation and EC heat-release mode, where the EC heat-release mode is a fan-controlled heat-release mode. Control mode 0_E designates a minimum-pressure-maintenance mode during which the engine (with the intercooler) is not running, and corresponds to control mode 0 in the case of an engine-cooling system; and control mode 0_S designates a combined minimum-pressure-maintenance mode during which the engine is running and the engine's supercharger is not running, and is a combined minimum-pressure-maintenance and fast-response-separation mode. CCU 563i (shown in FIG. 53) is energized only in modes 0_S, 1, 2, and 3.

[00881] The first typical control technique does not use intercooler shutter 580i; and thus has only four system-controllable elements: CR pump 10i, LT pump 404i, fan 510i, and damper 567i.

[00882] In mode 0_E, pump 10i and fan 510i do not run; damper 567i is in a preselected position (say closed, open, or half open); and MPMCU 564i controls pump 404i so that p_Rⁱ tends to p_RD^oi where p_RD^oi is a preselected value of p_Rⁱ. (CCU 563i places damper 567i in that preselected position at the instant in time when it is de-energized.)

[00883] In mode 0_S, CCU 563i ensures (1) pump 10i is controlled so that the level L_Xⁱ tends to L_XDⁱ; (2) pump 404i is controlled so that a refrigerant liquid-vapor interface surface forms in header 507i and thereafter has a level which tends to L_CDⁱ (while the intercooler is in mode 0_S); (3) fan 510i does not run; and (4) damper 567i is controlled so that T_Iⁱ tends to T_IDⁱ.

[00884] In mode 1 (used only with a non-azeotropic refrigerant), CCU 563i ensures (1) pump runs at a preselected capacity, usually near or equal to the pump's full capacity; (2) pump 404i is controlled so that p_Rⁱ tends to p_RD^oi, (3) fan 510i does not run; and (4) damper 567i is closed.

[00885] In mode 2, CCU 563i ensures (1) pump 10i is controlled so that L_Sⁱ tends to L_SDⁱ; (2) pump 404i is controlled so that T_Iⁱ tends to T_IDⁱ; (3) fan 510i does not run; and (4) damper 567i is closed.

[00886] In mode 3, CCU 563i ensures (1) pump 10i is controlled so that L_Sⁱ tends to L_SDⁱ; (2) pump 404i is controlled so that L_Rⁱ tends to L_RDⁱ; (3) fan 510i is controlled so that p_Rⁱ tends to p_RD^oi; and (4) damper 567i is closed.

[00887] The transition rules between the last-cited five modes are:

[00002]

(a)	0E to 0S	: engine starts running and supercharger does not
		start running
(b)	0E to 1	: no transition
(c)	0E to 2	: engine and supercharger start running
(d)	0E to 3	: no transition
(e)	0S to 1	: no transition
(f)	0S to 2	: supercharger starts running (while engine is
		running)
(g)	0S to 3	: no transition
(h)	1 to 2, or to 3	: no transition
(i)	2 to 3	: LRi < LR,MAXi − ΔLMAXi
(j)	0S to 0E	: engine stops running (and supercharger stops
		running)
(k)	1 to 0E	: engine not running and clock stops running
(l)	2 or 3, to 0E	: no transition
(m)	1 to 0S	: no transition
(n)	2 to 0S	: supercharger stops running while engine is
		running
(o)	3 to 0S	: no transition
(p)	3 to 1, or to 2	: no transition
(q)	3 to 2	: TIi < TIOi − ΔTIi, where ΔTIi > 0

In transition rules (a), (c), and (f), small delays between the event specified and the corresponding transition may be desirable and can be preselected. For example, a small delay may be desirable in transition rule (a) between the time the engine starts and the cited transition occurs to allow the exhaust gases, after a cold start, to be hot enough to ensure the refrigerant pressure does not momentarily fall below its minimum-permissible value.

[00889] I note that while the intercooler is in mode 2, the refrigerant pressure might, in very cold climates and under certain operating conditions, fall below its minimum-permissible value. If such an occurrence is possible, an additional control mode can be added during which damper 567i is partially opened to allow exhaust gases to supplement heat supplied by the intake air entering evaporator 561i, and thereby ensure the refrigerant's pressure does not fall below its minimum-permissible value.

[00890] I now describe a second typical control technique for reducing the response time of the intercooler. The second typical control technique allows the intercooler to achieve, after a given small time interval (say a few seconds) after the supercharger starts running, a much larger heat-transfer rate than that achievable with the first typical control technique after the same time interval. To this end, I use the engine's exhaust gases to allow the refrigerant liquid-vapor interface surface, upstream from CR pump 10i, to be located in receiver 7, instead of in condenser header 507i, while the intercooler is in mode 05. Whenever required, or whenever desirable, the invention (see for example FIG. 52) includes the use of controllable condenser-shutter 580i, driven by shutter-control motor 581i, through control arm 582i, to regulate the rate at which ram air flows past condenser refrigerant passages 399i and, whenever required, to ensure that rate is essentially zero. Motor 581i is controlled by signal C′_CSⁱ supplied by the intercooler's CCU (not shown). Shutter 580i is required whenever the intercooler's heat-transfer rate, while the engine is running and the supercharger is not running, is too high for the current value of T_Iⁱ to stay close to T_IDⁱ. And shutter 580i may be desirable, even if heat from the engine's exhaust gases is sufficient to keep T_Iⁱ close to T_IDⁱ, to reduce the size of heated segment 571i, or to allow pump 10i, as applicable, to run at a lower speed or to cycle on-and-off at a lower rate.

[00891] To implement the intercooler second typical control technique, I need only

• [00892] (a) to add, in each of the control modes 0_E, 1, 2, and 3, recited in the immediately-preceding major paragraph, the rule for controlling shutter 580i; namely in modes 0_E and 1 the shutter is in a preselected position (closed, open, or half-open), and in modes 2 and 3 the shutter is open; and
• [00893] (b) to change mode 0_S to mode 0′_S in which CCU 563 ensures (1) pump 10i is controlled as in mode 0_S; (2) pump 404i is controlled so that L_R tends to L_RD; (3) fan 510i does not run; (4) damper 567i is controlled in the same way as in mode 0_S; and (5) shutter 580i is closed.

[00894] The CCU for implementing the second typical control technique differs in essence from CCU 563 only in that it also generates a signal C′_CSⁱ for controlling shutter motor 581i; and the MPMCU for implementing that technique is the same as MPMCU 518.

[heading-00895] 4. Cooling Systems with a Water-cooled Condenser

[00896] a. General Remarks

[00897] A first principal difference, in piston-engine cooling applications, between type A combinations having a water-cooled condenser and type A combinations having an air-cooled condenser is that

• [00898] (a) the rate at which the former combinations release heat can, where required, be controlled by changing the flow rate of the water used to cool their condenser; whereas the rate at which the latter combinations release heat obviously cannot be thus controlled since their condenser is cooled by air and not by water; and that
• [00899] (b) ‘water-controlled heat release’, which is a particular form of EC heat release, is usually sufficient to control the rate at which heat is released by a water-cooled condenser.
  It follows that, for piston-engine cooling applications, preferred embodiments of type A combinations with a water-cooled condenser usually employ, instead of control mode 2, a control mode I shall refer to as control mode 2₀, whose primary purpose is to ensure p_R does not fall below PR,MN between the time the engine starts running and the time the system is in mode 3. The modifier ‘usually’ has been employed to allow for the special case where it may be desirable to use RC heat release instead of, or in addition to, water-controlled heat release. RC heat release may be desirable, or even required, in the particular case where it is not practicable to achieve a negligible minimum heat-release rate by, for example, (1) removing the cooling water from the cooling-system's condenser; (2) stopping the condenser's cooling-water circulation pump in the case of active EC heat release; or (3) stopping the cooling water flowing through the condenser with a valve, in the case of passive EC heat release.

[00901] A second principal difference, in piston-engine cooling applications, between type A combinations with a water-cooled condenser and type A combinations with an air-cooled condenser is that the former combinations are often installed in a building or on a ship and that consequently their refrigerant is usually never exposed to water-freezing temperatures, whereas the refrigerant of the latter combinations is in most applications exposed, at some time, to such temperatures. It follows that, for piston-engine cooling installations, the preferred refrigerant for type A combinations with a water-cooled condenser is often water (with, where required, passivation and anti-corrosion additives). Exceptions include installations in motor boats with no permanent heated engine room.

[00902] Because of the facts mentioned in the two immediately-preceding minor paragraphs. I shall limit my discussion of type A combinations with a water-cooled condenser to combinations having no freeze-protection capability (even where their refrigerant is water) and no RC heat-release capability.

[00903] b. Refrigerant Configuration and Control System

[00904] FIG. 54 shows a refrigerant configuration which may be a preferred configuration in the case where piston engine 500 is an in-line engine with a vertical bank of cylinders installed on a platform subjected to at most small tilts. The refrigerant configuration shown in FIG. 54 employs water as its refrigerant; and has in essence a class III_FN^ooo configuration with liquid-refrigerant inlet 2″ in refrigerant passages 505, and with refrigerant-vapor outlets 3″ and 3′ in refrigerant passages 505 and 504, respectively. The techniques which can be used for implementing control mode 1 in the case where the refrigerant is a non-azeotropic fluid should be obvious in view of the earlier teachings in this DESCRIPTION.

[00905] Liquid refrigerant entering at 2″ is supplied to refrigerant passages 505 inside one or more spaces bounded by one or more weirs 599. In the particular case where inlet 2″, consists of a number of ports equal to the number of cylinders of engine 500 in FIG. 54, weirs 599 may divide the space bounded by them into a number of spaces equal to the number of cylinders. The purpose of weirs 599 is to ensure the high heat-flux zones of refrigerant passages 505 remain immersed in liquid refrigerant while the rate at which liquid refrigerant flows through inlet 2″ is higher than the rate at which liquid, within the space bounded by weirs 599, evaporates. (Liquid refrigerant spilling over weirs 599, and not evaporated in refrigerant passages 505, enters refrigerant passages 504 through ports 538, and is evaporated in passages 504 whenever the current refrigerant-side temperatures of the walls of passages 504 are higher than the saturated-vapor temperature of the refrigerant in passages 504.) The rate at which liquid refrigerant is supplied at inlet 2″ is chosen high enough to ensure that refrigerant vapor exiting at outlets 3″ and 3′ is wet.

[00906] I said in the first minor paragraph of this section V,F,4,b that the refrigerant configuration shown in FIG. 54 has “in essence a class III_FN^oo configuration”. I used the qualifier “in essence” in the phrase within quotation marks to allow for the fact that, although the evaporator formed by the coolant passages of the piston engine shown in FIG. 54 is primarily an NP evaporator, weirs 599 provide that evaporator with a liquid-vapor interface surface in a part of refrigerant passages 505.

[00907] The refrigerant configuration shown in FIG. 54 has a water-cooled condenser 594 having refrigerant inlet 5, refrigerant outlet 6, cooling-water inlet 595, cooling-water outlet 596, refrigerant passages 399, and cooling-water passages 597. The flow-rate of cooling water through passages 597 is controlled by cold-water (or cooling-water) pump 598, or more briefly by CW pump 598, which is supplied with cooling water from a source of water (not shown). Cooling water exiting condenser 594 at 596 is disposed of at an acceptable location. An example, in the case of a piston-engine cooling system in a ship, of a suitable source of water is sea water (after, where required, it has been treated) and a suitable location for disposing water exiling condenser 594 is the sea.

[00908] c. Unsafe and Safe States

[00909] I shall say that the system to which the refrigerant configuration shown in FIG. 54 belongs is in an unsafe state when either of relations (3) and (4) is true, and that that system is in a safe state when relations (7) and (8) are true.

[00910] d. Typical Operating Method

[00911] I now outline a typical method of operating a system having the refrigerant configuration shown it) FIG. 54. I shall hereafter, in this section V,F,4,d, refer to the system having the last-cited refrigerant configuration as ‘the system’.

[00912] The system-controllable elements of the system are DR pump 46, LT pump 404, and ‘cold-water pump’ 598. (Pump 598 is a particular kind of cold-fluid pump.) The system has three control modes: modes 0, 2₀, and 3, where—as in sections V,F,2 and V,F,3—mode 0 is a minimum-pressure-maintenance mode while the engine is not running; where mode 2₀ is in essence a minimum-pressure-maintenance mode while the engine is running; and where mode 3 is a combined self-regulation and EC heat-release mode. The particular EC heat-release technique employed uses CW pump 598. The system includes CCU 590 shown in FIG. 55 and MPMCU 518 shown in FIG. 45.

[00913] In mode 0, pump 46 and pump 598 do not run and MPMCU 518 ensures pump 404 is control led so that p_R tends to p_RD^o.

[00914] In mode 2₀, CCU 590 ensures (1) pump 46 is controlled in a pre-prescribed way as a function of the engine's fuel mass-flow rate {dot over (m)}_F, or almost equivalently as a function of the engine's fuel volumetric-flow rate F_F; (2) pump 404 is controlled so that p_R tends to p_RD^o; and (3) pump 598 does not run. (The sensor providing a measure of the fuel-flow rate is not shown.)

[00915] In mode 3, CCU 590 ensures (1) pump 46 is controlled in a pre-prescribed way as a function of the current value of the engine fuel-flow rate F_F; (2) pump 404 is controlled so that the level L_D of liquid-vapor interface surface 139, as indicated by signal L′_D generated by liquid-level transducer 145, tends to a preselected, usually fixed, value L_DD; and (3) pump 598 is controlled so that p_R tends to p_RD.

[00916] The transition rules between modes 0, 2₀, and 3, are:

[00002]

(a)	0 to 20	: eng. starts running	(d)	2O to 0 : eng. stops running
(b)	0 to 3	: no transition	(e)	3 to 0 : no transition
(c)	20 to 3	: pR > pRDO + ΔpR1	(f)	3 to 2O : pR < pRDO + ΔpR2

In the foregoing transition Δp_R1 and Δp_R2 are small positive quantities, and Δp_R1 is larger than Δp_R2.

[00918] Refrigerant-pump control as a function of fuel-flow rate is discussed in section V,H.

[00919] e. Other Refrigerant Configurations and Control Systems

[00920] Any of the other refrigerant configurations and control systems described or mentioned in section V,F,2 can also be used with piston engines cooled by a system of the invention using a type A combination and a water-cooled condenser. The preferred refrigerant configuration and control system depends on the details of the particular application of interest.

[heading-00921] 5. Elimination of Minimum-pressure-maintenance Control Unit

[00922] a. Preliminary Remarks

[00923] In discussing minimum-pressure-maintenance with type A combinations having no MPMCU, I distinguish between combinations having (1) a type I_R, or a type III_R, configuration; and (2) a type II_R, a type IV_R, or a type V_R, configuration. Combinations having no MPMCU and a type I_R, or a type III_R configuration often can, while their principal configuration is inactive, maintain the current value (p_R−p_A) at a preselected value accurately over a wide range of environmental temperatures. By contrast, type A combinations having no MPMCU and a type II_R, a type IV_H, or a type V_R, configuration usually cannot do so.

[00924] In a system of the invention with a type A combination and no MPMCU, control mode 0 is eliminated and is replaced by a control mode 0₀ in which by definition none of the controllable elements of the type A combination, and in particular of its ancillary configuration, are controlled by the system.

[00925] I next give two examples of operating methods where an MPMCU is not employed, and where control mode 0 is replaced by control mode 0₀. The first example is a type A combination having a type I_R configuration with a spring. The second example is a type A combination having a type III_R configuration which can maintain the value of (p_R−p_A) between a preselected upper limit and a preselected lower limit while the combination is inactive. (If the AT pump used allows air to flow through it at a sufficient rate while it is not running, a type III_R configuration could be used to make the value of (p_R−p_A) equal to zero while the combination is inactive.)

[00926] b. Example with a Type I_R Ancillary Configuration

[00927] The principal configuration employed in the first example, see FIG. 56, is in essence the specialized principal configuration shown in FIG. 22 to which a subcooler refrigerant auxiliary circuit has been added. DR pump 46 is driven by engine 500 shown in FIG. 56, being cooled through belt 583 and pulley 584. The location of node 407 is suitable for an H-group refrigerant.

[00928] I assume, for specificity only, that, in mode 0₀, the minimum-permissible refrigerant pressure is the current ambient atmospheric pressure. I choose a spring (spring 478) which exerts a contracting force large enough to offset the expanding force exerted by corrugated cylindrical wall 403, and thus ensure the refrigerant pressure does not fall below ambient atmospheric pressure while the system's principal configuration is inactive. Clearly spring 478 can alternatively be chosen to exert a force which results in a preselected non-zero (positive or negative) current value of (p_R−p_A) while the principal configuration is inactive.

[00929] The system having the refrigerant configuration shown in FIG. 56 has the following six control modes, namely modes 0_0A, 0_0B, 1_A, 1_B, 2, and 3.

[00930] Mode 0_0A is a minimum-pressure-maintenance mode while engine 500 is not running, and corresponds to mode 0₀. And mode 0_0B is a minimum-pressure-maintenance mode while engine 500 is running but cold, and the effective capacity of pump 46 is zero although the engine is running. The purpose of mode 0_0B is to accelerate engine warm-up while T_R is lower than T_R,MIN.

[00931] Mode 1_A is used to achieve the same purpose as mode 1, namely to mix the components of a non-azeotropic refrigerant so that the concentrations of their liquid phases are approximately spatially uniform. And mode 1_B, which I name ‘the dry-up-prevention mode’, is used to continue cooling the engine, after it stops running; while T_R is at or above T_R,MIN.

[00932] Modes 2 and 3 have the same purposes as those recited in section V,G,2,a,iii.

[00933] Three-step liquid-level transducer 592 generates a signal L′_R indicating whether L_R has risen above an upper limit L_R,MAX or fallen below a lower limit L_R,MIN. (A proportional liquid-level transducer, or two two-level liquid-level transducers can be used instead of transducer 592.) Refrigerant-selector valve 585h and cabin-heating subcooler fan 552h are controlled manually by an operator or automatically by the cabin climate-control system. Cabin-heating SC pump 63h is controlled by the system's CCU only during modes 1_A and 1_B; and then only in the sense that the system's CCU causes pump 63h to run while the system is in any one of those two modes it if is not running (because the cabin-heating system has been turned off). Refrigerant-selector valve 586 has an inlet 587, an inlet 588, and an outlet 589; and is in position 1 in modes 1_A and 1_B, and in position 2 in all other modes, where position 1 causes liquid refrigerant to enter valve 586 through inlet 587 and where position 2 causes liquid refrigerant to enter valve 586 through inlet 588. Refrigerant-blocking valve 528 is closed only in mode 1_A and bidirectional two-step (on-off) recirculation-control valve 591 is open only in mode 0_0B. (I note that valve 528, instead of being controlled by the system's CCU, could be a thermostatically-control led valve which closes when T_R<T_R,MIN, and which opens when T_R>(T_R,MIN+ΔT_R), where ΔT_R is a small positive quantity.) The system's CCU controls pump 63h, valve 586, valve 528, and valve 591, with signals C′_SCH, C′_RSV1, C′_RBV, and C′_RCV, respectively. The remaining system-controllable elements of the refrigerant configuration shown in FIG. 56 are condenser fan 510, LT pump 404b, and LT valve 435, and are controlled as described next by signals C′_CF, C′_LT, and C′_LTV1, respectively.

[00934] In mode 0_0A, no system-controllable elements are controlled. In mode 0_0B, (1) pump 404B and valve 435 are controlled only in certain applications where this is desirable, so that P_R tends to p_RD^o, and (2) fan 510 does not run. In mode 1_A, (1) pump 404B and valve 435 are controlled so that p_R tends to p_RD^o, and (2) fan 510 does not run. In mode 1_B, (1) pump 404B and valve 435 are controlled so that p_R tends to p_RD^o, and (2) fan 510 runs at a preselected effective capacity, namely usually at a preselected speed. In mode 2, (1) pump 404B and valve 435 are controlled so that p_R tends to p_RD, and (2) fan 510 does not run. And in mode 3, pump 404B and valve 435 are controlled so that L_R stays close to L_RD, and (2) fan 510 is controlled so that p_R tends to p_RD.

[00002]

(a)	0OA to 0OB	: engine starts running
(b)	0OA to 1A, 1B, 2, or 3	: no transition
(c)	0OB to 1A or 1B	: no transition
(d)	0OB to 2	: TR ≧ TR,MIN
(e)	0OB to 3	: no transition
(f)	1A to 1B, 2, or 3	: no transition
(g)	1B to 2 or 3	: no transition
(h)	2 to 3	: LR < LR,MIN
(i)	0OB to 0OA	: engine stops running
(j)	1A to 0OA	: engine not running and clock stops
		running
(k)	1B, 2, or 3 to 0OA	: no transition
(l)	1A to 0OB	: engine starts running
(m)	1B, 2 or 3 to 0OB	: no transition
(n)	1B to 1A	: TR < TR,MIN
(o)	2 or 3 to 1A	: no transition
(p)	2 to 1B	: engine stops running
(q)	3 to 1B	: no transition
(r)	3 to 2	: pR < pRD − ΔpR, where ΔpR > 0

[00935] Where an engine is a multicylinder engine installed on a platform which subjects it to substantial tilts in its longitudinal direction, the engine should usually have separate and distinct cylinder-head coolant passages for each cylinder. For example, an in-line engine with 4 cylinders should usually have four sets of separate and distinct cylinder-head coolant passages, four liquid-refrigerant inlet ports, four liquid-refrigerant outlet (overflow) ports, and four refrigerant-vapor outlet ports.

[00936] c. Example with a Type III_R Ancillary Configuration

[00937] I use as an example the refrigerant configuration shown in FIG. 56A, and I assume, for specificity only that, in mode 0_0A the minimum-permissible and maximum-permissible refrigerant pressures are 1.1 bar and 1.9 bar, respectively.

[00938] The type III_R configuration used has a high-slip unidirectional air-transfer pump 420A and leakproof two-step bidirectional air valve 483 in series with it. Pump 420A, while not running, allows air to leak through it in the reverse direction at a high-enough rate for it (1) not to have to be bidirectional or (2) not to need a bidirectional valve in parallel with it to allow air to exit space 421 at a fast-enough rate to control p_R in mode 2 and to control L_R in mode 3. Valve 483 is leakproof in the sense that it does not allow air from space 421 to leak through it, while it is closed and pump 420A is not running, for pressures across it up to, say, one bar. The CCU of the refrigerant configuration shown in FIG. 56A, before deactivating itself and changing to mode 0₀, controls pump 420A with signal C′_AT so that p_R tends to 1.5 bar and, when p_R reaches that value, stops pumps 420A running, closes valve 483 with signal C′_ATV1, and deactivates itself. This should, at least in temperate quasi-arctic climates, ensure p_R stays between 1.1 and 1.9 bar when the configuration shown in FIG. 56A is in mode 0_0A and stays at the same altitude.

[00939] An alternative refrigerant configuration to that shown in FIG. 56A would have a spring located in space 421 instead of valve 483. If a spring were located in space 421, it could be used, like spring 478 in FIG. 56, to offset the force exerted by corrugated cylindrical wall 403. Where the value of p_R is allowed to fall below p_A by an amount corresponding to the force exerted by wall 403, no spring need be used to offset that force. This last statement is of course also true in the case of the refrigerant configuration shown in FIG. 56. Clearly, a spring located in space 421 in FIG. 56A can alternatively be chosen so that the current value of (p_R−p_A) has a preselected (positive or negative) non-zero current value while the principal configuration shown in FIG. 56A is inactive.

[00940] d. Other Ancillary Configurations

[00941] The inert gas in the L_R reservoir of a type A combination having a type IV_R, or a type V_R, ancillary configuration has essentially a constant volume in mode 0₀. Consequently the pressure of that inert gas will, in that mode, change its value as a function of ambient temperature T_A; and therefore so will the current value of p_R. Also, the value of the pressure of the inert gas in the LR reservoir is essentially unaffected by changes in ambient atmospheric pressure p_A. It follows that, in applications where substantial changes in T_A and/or in p_A occur, the resulting changes in the current value of (p_R−p_A) may be unacceptable. In such applications an MPMCU would have to be used with type A combinations having a type IV_R, or a type V_R, ancillary configuration.

[00942] I note that the invention includes modified type I_R, II_R, and III_R, ancillary configurations which—although they have a variable-volume reservoir—contain an inert gas (like ancillary configurations with a fixed volume).

[heading-00943] 1. Preliminary Remarks

[00944] I discuss in this section V,G applications where the properties complete minimum-pressure maintenance and self regulation are required, and where gas-controlled heat release, or more briefly GC heat release, is usually also required.

[00945] In sections V,G,2 and V,G,3 I describe type C combinations, and their associated control techniques, for the case where the combinations' condenser is an air-cooled condenser. And, in section V,G,4 I describe type C combinations, and their associated control techniques, for the case where the combinations' condenser is a water-cooled condenser.

[00946] Because all the type A combinations discussed in this section V,G have no partial minimum-pressure maintenance, I shall refer for brevity, in this section V,G, to complete minimum-pressure maintenance simply as ‘minimum-pressure maintenance’. This property, as mentioned in section III,D, is achieved in type C combinations by inserting an inert gas in their principal configuration.

[heading-00947] 2. Cooling Systems with an Air-cooled Condenser

[00948] a. Cooling Systems with a Pool Evaporator

[00949] i. First Refrigerant & Inert-gas Configuration, Control System, and Operating Method

[00950] FIGS. 57 to 59 show a system used to cool piston engine 500, hereinafter referred to respectively as ‘the system’ and ‘the engine’ in this section V,G,2,a. The refrigerant & inert-gas configuration, or more briefly the R&IG configuration, shown in FIG. 57 has a class XI_FF^ooo principal configuration and a type IV_G configuration having a fixed-volume IG reservoir designated by numeral 453, a GT pump designated by numeral 443, and a condensate-type refrigerant-vapor trap designated by numeral 446. (Although I have shown a two-port IG configuration, I do not intend to imply that a two-port IG configuration must be used.)

[00951] The R&IG configuration shown in FIG. 57 is charged with an appropriate amount of refrigerant mass M_R and an appropriate mass of inert gas M_G. (The term ‘inert gas’ includes air {see definition 72.}) I denote the current amount of inert-gas mass stored in an IG reservoir by the symbol M_GR; and the maximum amount of inert-gas mass that can be stored in an IG reservoir by the symbol M_GR,MAX, where M_GR,MAX is approximately equal to M_G. And I also denote the current value of the internal volume of a variable-volume IG reservoir, or the fixed volume of an IG reservoir, by V_GR; and the maximum internal volume of a variable-volume IG reservoir by V_GR,MAX. I further denote the current total pressure in an IG reservoir by p*_GR, and the design maximum operating pressure in an IG reservoir by p*_GR,MAX.

[00952] The control system includes CCU 600 and MPMCU 601 shown respectively in FIGS. 58 and 59. CCU 600, on the basis of signals from transducers, and of preselected instructions stored in CCU 600, generates signals used to control CR pump 10, EO pump 27, GT pump 443, condenser fan 510, SC pump 63h, and refrigerant liquid-diverter valve 555 having an inlet 556 and outlets 557 and 558. And MPMCU 601, on the basis of signals from transducers and preselected instructions stored in MPMCU 601, generates signals used to control CR pump 10 and GT pump 443 when they are not being controlled by CCU 600. EO pump 27 is used primarily because separator 21 is below the level of surface 123.

[00953] Proportional absolute-pressure transducer 603 performs a different function from that performed by absolute-pressure transducer 514 in type A combinations; and it is for this reason that I have designated the former transducer by a different numeral from that used to designate the latter transducer. More specifically, transducer 603 generates a signal p*′_R which provides, at a preselected location in the principal configuration of an R&IG configuration, (1) a measure of the total pressure p*_R in the principal configuration, which is in general the current value of the sum of the partial refrigerant pressure and the partial inert-gas pressure; and which is in particular (2) a measure of the current value of the refrigerant pressure p_R in the absence of inert gas or a measure of the current value of the inert-gas pressure p_G in the absence of refrigerant.

[00954] Proportional absolute-pressure transducer 605 generates a signal p*′_GR providing a measure of the current value of the total pressure p*_GR in reservoir 453, and proportional gas-temperature transducer 606 generates a signal T′_GR providing a measure of the current value of the inert-gas temperature T_GR in reservoir 453.

[00955] The terms ‘unsafe state’ and ‘safe state’, in the case of engine-cooling systems using type C combinations, have the same meanings as those given in section V,F,2,ii. However, the set of conditions indicating whether an engine-cooling system using a type C combination is in an unsafe state, or in a safe state, are different, Namely, I shall say that the last-cited system is in an unsafe state, while the engine is running and hot, when one of the following four relations is true:
L_P<L_P,SAFE; L_R<L_R,SAFE; p*_R>p*_R,SAFE; and T_R>T_R,SAFE;  (1), (2), (3*), (4)
and I shall say that the last-cited system is in a safe state, while the engine is running and hot, if all of the following four relations are true:
L_P≧L_P,SAFE; L_R≧L_R,SAFE; p*_R≦p*_R,SAFE; and T_R≦T_R,SAFE.  (5), (6), (7*), (8)
An engine is, by definition, hot when the current value of T_R exceeds T_R,MIN, as defined earlier.

[00960] I now outline a typical method of operating the system shown in FIGS. 57 to 59. I shall hereinafter, in this section V,G,2,a,i, refer to the system shown in FIGS. 57 to 59 as ‘the system’.

[00961] I start at an instant in time when the engine being cooled by the system is not running and is started, say, by an operator manually. When the engine is started, CCU 600 and all its associated transducers and controllable elements are energized, if they are not already energized.

[00962] CCU 600, as soon as it is energized, and subsequently at frequent preselected periodic time intervals while it remains energized, performs a system safety check to determine whether the system is in a safe state. If it is not, an audible and/or visual warning signal is generated to indicate that the system is in an unsafe state, and the engine, after being stopped by the operator, is inhibited from being started. If the unsafe state has occurred because p_R or T_R, or both, have exceeded their safe values, CCU 600 runs fan 510 at its maximum capacity until their safe values are no longer exceeded, and then de-energizes itself automatically. MPMCU 601, which is always energized while the system is in a safe state, remains energized and controls LT pump 404 in the same way as in control mode 0*. (See next major paragraph.) If the system has become unsafe because of an insufficient refrigerant charge, MPMCU 601 will de-energize itself automatically. (The refrigerant charge is insufficient when relation (1) or (2) is satisfied.)

[00963] I shall describe the operation of systems of the invention with a type C combination, while they are in their safe state, in terms of control modes and transition rules. In FIG. 57, the system-controllable elements are CR pump 10, EO pump 27, GT pump 443, air-condenser fan 510, liquid-refrigerant diverter valve 555, and SC pump 63h, controlled respectively by signals C′_CR, C′_EO, C′_GT, C′_CF, C′_RDV1, and C′_SCH. The last-cited six controllable elements are, as a set, controlled differently in control modes 0*, 1*, 2*, and 3*, which roughly correspond respectively to control modes 0, 1, 2, and 3, used with type A combinations. Namely, mode 0* is a minimum-pressure-maintenance mode, mode 1* is a mixing mode (used only with a non-azeotropic refrigerant), mode 2* is a gas-controlled heat-release mode, and mode 3* is a combined self-regulation and EC heat-release mode. However, minimum-pressure maintenance in mode 0* is achieved by using an inert gas instead of liquid refrigerant; mixing refrigerant components in mode 1* is achieved by circulating liquid refrigerant around a refrigerant auxiliary circuit, and not around the refrigerant principal circuit; and heat-release control in mode 2* is achieved by using inert gas instead of liquid refrigerant, and by achieving self regulation, and mode 2* is consequently in fact a combined self-regulation and gas-controlled heat-release mode. Mode 3*, like mode 3, is used to achieve self regulation and, whenever required, also to achieve EC heat release. CCU 600 controls (cabin-heating) SC pump 63h only when the system is in mode 1*. At all other times, pump 63h is controlled by the engine operator or automatically by the cabin-heating system.

[00964] In mode 0*, pump 27 and fan 510 do not run, and diverter valve 555 is in position 1, namely by definition valve 555 is in a position which causes liquid refrigerant entering at inlet 556 to exit at outlet 557; and MPMCU 601 controls pump 10 so that L_P tends to L_PD, and controls pump 443 so that p*_R tends to p*_RD^o, where p*_RD^o is the preselected desired current value for p*_R while the system is in mode 0*.

[00965] In mode 1*, CCU 600 ensures (1) pump 10 is controlled so that L_P tends to L_PD; (2) pump 27 is controlled so that L_S tends to L_SD; (3) pump 443 is controlled so that p*_R tends to p*_RD, where p*_RD is a preselected desired current value for p*_R while the system is in modes 1* to 3*; (4) fan 510 does not run; and (5) valve 555 is in position 2, namely by definition valve 555 is in a position which causes liquid refrigerant entering at inlet 556 to exit at outlet 558; and (6) pump 63h runs at or near its maximum capacity.

[00966] In mode 2*, CCU 600 ensures (1) pump 10 is controlled so that L_P tends to L_PD; (2) pump 27 is controlled so that L_S tends to L_SD; (3) pump 443 is controlled so that p*_R tends to p*_RD; (4) fan 510 does not run; and (5) valve 555 is in position 1.

[00967] In mode 3*, CCU 600 ensures (1) pump 10 is controlled so that L_P tends to L_PD; (2) pump 27 is controlled so that L_P tends to L_PD; (3) pump 443 is control led so that p*_GR tends to p*_GR,3, where p*_GR.3 is a preselected value of p*_GR discussed in the immediately-following major paragraph; (4) fan 510 is controlled so that p*_R tends to p*_RD; and (5) valve 555 is in position 1.

[00968] The transition rules between the last four modes are (where ‘eng.’ is an abbreviation for ‘engine’):

[00002]

(a)	0* to 1*: no transition	(h)	2* to 0*: no transition
(b)	0* to 2*: eng. starts running and TR ≧	(i)	3* to 0*: no transition
	TR,MIN
(c)	0* to 3*: no transition	(j)	2* to 1*: tR < TR,MIN
(d)	1* to 2*: eng. starts running	(k)	3* to 1*: no transition
(e)	1* to 3*: no transition	(l)	3* to 2*: p*R < p*RD −
(f)	2* to 3*: p*GR = p*GR,3 and p*R >		Δp*R2
	p*RD + Δp*R1
(g)	1* to 0*: eng. not running and clock
	stops running

In rule (f), Δp*_R1 is a finite positive quantity; and, in rule (I), Δp*_R2 is a finite positive quantity large enough for the value (p*_R−Δp*_R2) not to be larger than the value of p*_R at which CCU 600 stops fan 510 running while the system is in mode 3*. The clock mentioned in rule (g) is used in the way described in the third minor paragraph of the second major paragraph of section V,F,2,a,iii.

[00970] In general, the preselected value p*_GR,3 may be a fixed value, or a value which changes in a pre-prescribed way as a function of p*_GR and T_GR.

[00971] In the former case, proportional absolute-pressure transducer 605 can be replaced by a two-step pressure transducer indicating whether p*_GR is close to p*_GR,MAX, transducer 606 can be eliminated, and the value of p*_GR,MAX is typically chosen equal to the design maximum operating value p*_GR,MAX of p*_GR.

[00972] In the latter case signal T′_GR, generated by transducer 606, is used to compute the value p*_GR,3 of p*_GR at which the principal configuration contains essentially no inert gas at a preselected typical value of T_R when the system is in mode 3*. Assuming reservoir 453 contains essentially only inert gas, the value of p*_GR,3 can be computed, as a function of T_GR, by using van der Waal's equation. Where the values of p*_GR,3 are low enough, the equation of state of a perfect gas can be used instead of van der Waal's equation. In either case, the preselected function for computing p*_GR,3 is stored in CCU 600.

[00973] Where condensate-type refrigerant-vapor trap 446 is not used, or allows a significant amount of refrigerant vapor to enter and condense in reservoir 453, the preselected function for computing p*_GR,3 can be chosen so that it takes into account the effect of the presence of liquid refrigerant in reservoir 453. To this end, the independent variables of the last-cited function would also include p*_GR and L_GR, where L_GR is the current level of liquid refrigerant in reservoir 453. The current value of L_GR can be obtained by using a proportional liquid-level transducer (not shown). I note that the value of p*_GR, in addition to the value of T_GR, is needed to compute the solubility of the inert gas in the liquid refrigerant in reservoir 453 because that solubility affects the value of p*_GR,3.

[00974] An alternative to using transition rule (f), in this section V,G,2,a,i, is to use the transition rule given next: $\left(f^{\prime }\right)2^{*}\mathrm{to}{3}^{*}\text{:}{T}_{\mathrm{RS}}^e=T_{\mathrm{RS}}^{*e}\mathrm{and}{p}_R^{*}>p_{\mathrm{RD}}^{*}+\Delta p_{\mathrm{R1}}^{*},$
where T*_RS^θ is a measure of the actual current value of the refrigerant's saturated-vapor temperature at a location near outlet 471 where inert gas exits the principal configuration, and where T*_RS^θ is a measure of the saturated-vapor temperature the refrigerant would have H its pressure at outlet 471 were equal to the current value p*_R^θ of the total pressure in the principal configuration near outlet 471. The value of T_RS^θ is lower than that of T*_RS^θ when inert gas is present at outlet 471 and becomes equal to T*_RS^θ when no inert gas is present at outlet 471. The current value of T_RS^θ can be obtained by locating proportional temperature transducer 616 at outlet 471, as shown in FIG. 57A, generating a signal T_R^θ′. Alternatively, refrigerant-temperature transducer 516 may provide an adequate measure of T_RS^θ. The current value of T*_RS^θ can be obtained by locating proportional absolute-pressure transducer 617 at outlet 471, as shown in FIG. 57A, generating a signal p*_R^θ′. Transducer 617 need not necessarily be a second proportional absolute-pressure transducer. It could be merely transducer 603 relocated at outlet 471. Alternatively, transducer 603, as originally located—or relocated in refrigerant-vapor transfer-means segment 21-5—may provide an adequate measure of p*_R^θ. In the case of a non-azeotropic refrigerant, the value of T*_RS^θ depends on the concentrations of its components. These concentrations can often be predicted as a function of p*_RS^θ for a given refrigerant when the concentrations of its components are known. For example, it is known that, near atmospheric pressure, the concentration of ethylene glycol having a mean spatial concentration of 50% in an aqueous solution, has a concentration of between 3% and 4% in the solution's vapor. And this allows T*_RS^θ to be computed by the system's CCU quite accurately when the current value of p*_R^θ is near one atmosphere.

[00976] ii. Comments on First Refrigerant & Inert-gas Circuit Configuration, Control System, and Operating Method

[00977] Pump 443 would not need to run in mode 3* if no inert gas leaked through pump 443 toward the principal configuration while pump 443 is not running and p*_GR is equal to p*_GR,MAX. The control-mode rule for pump 443 in mode 3* assumes pump 443 is not leakproof when p*_GR is equal to p*_GR,MAX, and assumes pump 443 will have to run occasionally, or even continuously (at a very low flow rate), to maintain p*_GR close to p*_GR,MAX while the system shown in FIGS. 57 to 59 is in mode 3*.

[00978] CR pump 10 is controlled in mode 0* (namely while the engine is not running and cold) so that L_P stays close to L_PD to ensure liquid refrigerant covers the engine's high heat-flux zones by the time they need to be cooled. Controlling pump 10 in mode 0* would be unnecessary if (1) pump 10 were a zero-slip positive displacement pump (or had in series with it a unidirectional valve (see FIG. 43B) which is leakproof in its no-flow direction); or if (2) pump 10 had a large-enough capacity to cover the engine's high heat-flux zones by the time they need to be cooled.

[00979] GT pump 443 is controlled in mode 0* so that p*_R stays close to
p*_RD^o=p_A+Δ*^op,  (9′)
(where Δ*^op is usually a fixed quantity) for the following two reasons: firstly, to compensate for inert-gas leaking through pump 443 while it is not running, and secondly to compensate for changes in ambient-air temperature and pressure. Controlling pump 443 would be unnecessary if (1) it were a zero-slip positive displacement pump (or had in series with it a unidirectional valve (see FIG. 39C) which is leakproof in its no-flow direction); and if (2) compensating for changes in ambient-air temperature, or in ambient-air pressure, were unnecessary. (The ambient-air pressure may change not only because of changes in atmospheric pressure at a given altitude, but also because of changes in altitude. Substantial changes in altitude may occur even while the engine is not running because, for example, the engine is installed in an automobile being shipped by air, or by train or other land-based vehicle over a mountain.)

[00982] Compensating for changes in ambient-air temperature is unnecessary if, when the engine; stops running, the value of p*_R is chosen high enough for the current value of p*_R, at the design lowest ambient-air temperature, not to fall below the minimum permissible value for p*_R. And compensating for changes in ambient-air pressure is unnecessary if, at the design lowest ambient-air pressure, the system does not ingest air and is not damaged by crushing pressures.

[00983] Pump 63h, except during mode 1*, is not controlled by the system, but is controlled manually, or automatically, by a thermostat (located in the passenger cabin in the case of a passenger automobile). If control of pump 63h in mode 1* by CCU 600 is not acceptable, an additional refrigerant pump, or a refrigerant valve, and an associated refrigerant-circuit segment, would have to be added where the system employs a non-azeotropic refrigerant to achieve refrigerant-component mixing.

[00984] I note that for liquid refrigerant to circulate around refrigerant auxiliary circuit 87h-556-558-559-5-6-8-9-11-12-550′ in mode 1*, point 560 must be higher than point 5. I also note that, where the R&IG configuration shown in FIG. 57 is installed with condenser 508 high enough with respect to the engine, for no liquid refrigerant to be contained in it in mode 0*, liquid refrigerant exiting valve 555 at 558 in mode 1* could be supplied to condenser liquid header 509, or perhaps even to receiver 7 instead of to point 559.

[00985] iii. Second Refrigerant & Inert-gas Configuration, Control System, and Operating Method

[00986] The specialized principal configurations shown in FIGS. 21 to 23 may often be preferred in ground installations and perhaps in small vehicles subjected to small tilts. The last-cited principal configurations are preferably used with an engine-driven pump; and, in the case of ground installations where pressurized air is available, perhaps alternatively with an air-driven pump. I next describe a typical system of the invention, hereinafter referred to as ‘the system’ in this section V,G,2,b,iii, which has the principal configuration shown in FIG. 60, a CCU (not shown), and no MPMCU.

[00987] The system employs water as its refrigerant, and drives for example an electric generator, installed in a heated building; except for condenser 508, fan 510, air-transfer pump 420, IG variable-volume reservoir 441, and rigid closed cylinder 419′ containing reservoir 441. Cylinder 419′ is located preferably in the shade and may have a finned outer surface. (Fins may often not be necessary.) Cylinder 419′ differs from cylinder 419 in FIG. 38 as follows. Firstly, space 421′ communicates with the atmosphere through air-permeable device 608. Secondly, air-transfer pump 420 inserts air into, and extracts air from, cylindrical space 610 formed between the corrugated walls 403 of reservoir 441 and the cylindrical surface of cylinder 419′. And thirdly, the upper side 611 of reservoir 441 extends past walls 403 and is in sliding airtight contact with the cylindrical surface of cylinder 419′.

[00988] The system also includes (1) proportional absolute-pressure transducer 603; (2) two-step engine-wall temperature transducer 604 which generates a signal T′_W,MAX indicating whether the current engine-wall temperature at a critical high heat-flux zone is close to its design maximum operating value; (3) IG reservoir contact switch 612 which generates a signal V′_GR,MAX indicating whether the current value of internal volume V_GR of reservoir 441 is at, or close to, its maximum value V_GR,MAX; (4) two-step liquid-level transducer 613 which generates a signal L′_RD used to indicate whether the liquid refrigerant level, while the principal configuration is inactive, is close to a preselected level L₀L′₀; (5) spring 614 capable of exerting, whilst fully extended, a force corresponding to a pressure at least equal to the maximum value of p*_R^o; and (6) pressure-relief valve 615 set at a value high enough fully to compress spring 614. Transducer 604 may, for example, consist of one or more bimetallic temperature switches. In the case where several bimetallic switches are used, the number of bimetallic switches in multi-cylinder engines would be equal to, or a submultiple of, the number of cylinders. The purpose of receiver 7, which may not be needed, is (1) to keep the liquid refrigerant level substantially below the building's roof, while the system's principal configuration is inactive, and (2) to prevent liquid refrigerant backing-up into separating assembly 42*.

[00989] The system is charged with liquid refrigerant until transducer 613 indicates the level of liquid-refrigerant is close to L₀L′₀, where the level L₀L′₀ is chosen so that the amount of refrigerant mass M_R in the R&IG configuration shown in FIG. 60 is sufficient to ensure—under all operating conditions—that the amount of liquid refrigerant in that configuration is sufficient for refrigerant liquid-vapor interface 123 in refrigerant passages 505 to reach the level of outlet 94; while, at the same time, the refrigerant liquid-vapor interface surfaces in refrigerant circuit segment 8-9-49 and in refrigerant line 45*-49 are at a level (1) high enough for pump 46 not to cavitate significantly, and (2) low enough for liquid refrigerant not to back-up into separating assembly 42*. I note that level L₀L′₀ need not be above point 8, but must be above point 94. The system is also charged with an amount of inert gas mass M_G sufficient for the value of p*_R^o not to fall below the current ambient atmospheric pressure over the entire range of expected ambient atmospheric pressures at the location where the building is installed, and over the entire range of expected temperatures in that building. While the R&IG configuration is being charged, spring 614 ensures V_GR has its design minimum value. Typical acceptable relative elevations (not to scale) of points 94, 45, 8, and 9, are shown in FIG. 60.

[00990] The system has three control modes: modes 0*₀, 2*, and 3*, where mode 0*₀ is, by definition, a minimum-pressure-maintenance mode in which the system controls none of its controllable elements.

[00991] In mode 2*, the system's CCU ensures (1) pump 420 is controlled so that p*_R tends to p*_RD; and (2) fan 510 does not run. And, in mode 3*, (1) pump 420 is controlled so that V_GR stays close to V_GR,MAX; and (2) fan 510 is controlled so that p*_R tends to p*_RD. The preselected desired value p*_RD for p*_R may be fixed, or may change in a pre-prescribed way as a function of one or more characterizing parameters. A typical characterizing parameter, when the engine cooled by the system drives an electric generator, is the mechanical load to which the generator subjects the engine.

[00992] The transition rules between modes 0*₀, 2*, and 3*, are

[00002]

	(a)	0*O to 2*	: engine starts running
	(b)	0*O to 3*	: no transition
	(c)	2* to 3*	: VGR = VGR,MAX and TW > TWD,MAX
	(d)	2* to 0*O	: engine stops running and TW < TWD
	(e)	3* to 0*O	: no transition
	(f)	3* to 2*	: TW ≦ TWD,MAX − ΔTW;

where T_W0 is low enough to prevent liquid refrigerant being evaporated, and where ΔT_W is a small positive value.

[00994] I note that transducer 604 can be eliminated if transition rules (c), (d), and (f) are replaced respectively by transition rules

[00002]

	(c′) 2* to 3*	: VGR = VGR,MAX and p*R > p*RD + Δp*R1
	(d′) 2* to 0*O	: TR < TR,MIN
	(f′) 3* to 2*	: p*R < p*RD − Δp*R2

where Δp*_R1, and Δp*_R2 have fixed positive values, and where the value of T_R is provided by a refrigerant temperature transducer which need only be a two-step transducer.

[00996] I also note that if points 45* and 8 are high enough above interface surface 123, pump 46 can be eliminated.

[00997] iv. Other Refrigerant & Inert-gas Configurations and Control Systems

[00998] It should be clear from the teachings so far in this DESCRIPTION, and from my pending U.S. patent application Ser. No. 400,738, filed 30 Aug. 1989, that the class XI_FF^ooo principal configurations shown in FIGS. 57 and 60 are only two of many kinds of principal configurations with a pool evaporator and an air-cooled condenser which may be preferred for cooling a piston engine. Other kinds of preferred principal configurations, in the case of type C combinations, include class and VIII_NN^ooo, VIII_FN^ooo, VIII_FN^soo, VIII_FF^soo, VIII_FF^s′oo, VIII_FF^s″oo, VIII*_FN^ooo, VIII*_FN^soo, IX_FN^oo, IX_FN^so, XI_FF^so, XI_FF^s′o, XI_FF^s′′oo, XI*_FN^oo, and XI*_FN^so, configurations. (In refrigerant configurations with a subcooler, the subcooler would be located upstream from pump 10, pump 46, or pump 27, as applicable.) Other kinds of preferred principal configurations also include the specialized principal configurations shown in FIGS. 21 and 23.

[00999] I would explain that principal configurations with a subcooler are desirable, or even necessary, in certain installations to increase—while the system is in mode 3*—the amount of subcool of liquid refrigerant exiting, as applicable, receiver 7, separator 21 or 42, or separating assembly 21* or 42*; and thus increase the net positive suction head available, as applicable, to pump 10, to pump 46, or to pump 27. The subcooler used may merely be a finned quasi-horizontal refrigerant-line segment located roughly in the same plane as refrigerant passages 399, and exposed to ram air and/or to the airflow induced by fan 510. An example of such a finned segment, in the case of a class VIII_FN^ooo configuration, is segment 9-522 shown in FIG. 43E.

[01000] It should also be clear from the teachings so far in this DESCRIPTION that type II_G, IV_G, and V_G, IG configurations can also be used with type C combinations and may be preferred IG configurations in certain installations.

[01001] It should further be clear from the foregoing teachings that a shutter can be used upstream from a condenser of a type C combination, as well as upstream from a condenser of a type A combination, to control the rate at which the condenser releases heat. The shutter, if desirable, can be made of thermally-insulating material to accelerate engine warm-up in cold climates. How shutter-control led heat release can be accomplished with type C combinations should be clear in view of the earlier discussion in this DESCRIPTION of shutter-control led heat release with type A combinations.

[01002] b. Cooling Systems with a Non-pool Evaporator

[01003] i. Preliminary Remarks

[01004] Type C combinations, in common with type A combinations, are suitable for a much wider range of piston-engine cooling applications when they have an NP evaporator instead of a P evaporator because they can be used with any cylinder orientation and impose much less stringent constraints on the tilts of the platform on which they are installed.

[01005] ii. Refrigerant & Inert-gas Configuration and Control System

[01006] The first system chosen as an example has the class III_FN^oo principal configuration and the type IV_G ancillary configuration, shown in FIG. 61, and a CCU (not shown) but no MPMCU. I shall hereinafter, in sections V,G,2,b,ii to V,G,2,b,iv, refer to the cooling system having the R&IG configuration shown in FIG. 61 as ‘the system’, and to the engine cooled by it as ‘the engine’. DR pump 46 includes component DR pumps 46A and 46B driven by a belt through common pulley-and-clutch 621, and through a common shaft (not shown) at right angles to the sheet on which FIG. 61 is drawn. Pump 46A has a refrigerant inlet 47A and a refrigerant outlet 48A; and pump 46B has a refrigerant inlet 47B and a refrigerant outlet 48B.

[01007] The system has the following transducers: (1) two-step liquid-level transducer 613; (2) two-step liquid-level transducer 622; (3) proportional absolute-pressure transducer 603; (4) proportional engine-wall temperature transducer 634; and (5) two-step absolute-pressure transducer 626. The signals generated by the foregoing five transducers are supplied to the system's CCU.

[01008] Signal L′_R0, generated by transducer 613, is used to indicate whether the system is charged with a correct amount of liquid refrigerant. (To this end, transducer 613 is located at level L₀L′₀, where L₀L′₀ is the correct liquid-refrigerant level while the system's principal configuration is inactive.) Signal L′_RR, generated by transducer 622, is used to indicate whether liquid refrigerant—draining out of fixed-volume IG reservoir 453 through one or more ports 623 at the bottom of the cylindrical part 624 of reservoir 453—has reached in vessel 625 a preselected release level L_RR determined by the location of transducer 622. Signal p*′_GR,MAX, generated by transducer 626, indicates p*_GR has reached its design maximum operating value p*_GR,MAX. And signals p*′_R and T′_W, generated by transducers 603 and 634, respectively, are used by the system's CCU to generate signals C′_PC, C′_GT, C′_CF, C′_RDV1, C′_RDV2, C′_RR, and C′_SC, used to control respectively DR-pump clutch 621, GT pump 443, condenser fan 510, liquid-refrigerant diverter valve 555, liquid-refrigerant diverter valve 630 having an inlet 631 and outlets 632 and 633, liquid-refrigerant release (drain) valve 487, and SC pump 63h.

[01009] The class XI*_FN^oooo principal configuration shown in FIG. 61 differs from the group XI* configurations mentioned in section V,B,8 in that it has (1) in addition to receiver 7, dual-return receiver 640, namely a receiver which is supplied with non-evaporated refrigerant as well as with liquid refrigerant generated by the condensation of evaporated refrigerant (in condenser 508); and in that it has (2) liquid-refrigerant drain line 645-646 which is used to ensure no liquid refrigerant accumulates, particularly during a cold start, in refrigerant passages 504 and 505. The particular dual-return receiver shown in FIG. 61 has a first liquid-refrigerant inlet 641, a second liquid-refrigerant inlet 642, a first liquid refrigerant outlet 643, and a second liquid-refrigerant outlet 644;

[01010] The type IV IG configuration shown in FIG. 61 has a condensate-type refrigerant-vapor trap consisting only of accessory condenser 459 having inert-gas passages 650 and headers 651 and 652. Residual refrigerant vapor exiting condenser 459 and accumulating in reservoir 453 is returned, as mentioned earlier, to principal-configuration point 440A (which could have been chosen to coincide with point 440).

[01011] The system's R&IG configuration is first charged with liquid refrigerant until transducer 613 generates signal L′_R0 indicating the refrigerant liquid level in refrigerant-vapor line 44-5 has reached level L₀L′₀; and is then charged with inert gas until the R&IG configuration's internal pressure p*_R, reaches a preselected value p*_R^o, where the preselected value p*_R^o may be different for different R&IG-configuration mean temperatures. Valve 477 is kept open by say a manual override, while the system's R&IG configuration is being charged with refrigerant and subsequently with inert gas.

[01012] iii. Unsafe and Safe States

[01013] I shall say that the system is in an unsafe state when relation (3′) or (4) is satisfied, and that the system is in a safe state when relations (3′) and (4) are satisfied.

[01014] iv. Typical Operating Method

[01015] The system, while in a safe state, has six control modes, namely modes 0*_0A, 0*_0B, 1*_A, 1*_B, 2*, and 3*.

[01016] Mode 0*_0A is a minimum-pressure-maintenance mode while the engine is not running and corresponds to control mode 0*₀ in section V,G,2,a,iii. And mode 0*_0B is a minimum-pressure-maintenance mode while the engine is running but cold, and the effective capacity of pump 46 is zero although the engine is running. The purpose of mode 0*_0B is to accelerate engine warm-up, while T_W is below a preselected value T_WD1 by supplying no liquid refrigerant to the engine's coolant passages while the value of T_W is less than T_TWD1. T_WD1 is a preselected value of T_W substantially lower than the maximum permissible value T_W,MAX of T_W, and higher than the value T_RS^o, of the saturated-vapor temperature T_RS, corresponding to p*_RD^o. (T_WD1 may, for example, be 120° C.).

[01017] Mode 1*_A is used to achieve the same purpose as control mode 1*, namely is used to mix the components of a non-azeotropic refrigerant so that the concentrations of their liquid phases are approximately spatially uniform. However, the particular R&IG configuration shown in FIG. 61 will achieve the last-cited purpose only in the case of a group H refrigerant. Mode 1*_B, which I name ‘the dry-up-prevention mode’, is used to continue supplying liquid refrigerant to the system's evaporator, and thus to continue cooling the engine, while T_W is at or above T_WD2, after the engine stops running. T_WD2 is usually less than the minimum value T_RS,MIN of the refrigerant saturated-vapor temperature T_RS at which the system is designed to operate and can often be chosen equal to T_WD1. And modes 2* and 3* have the same purposes as those recited in section V,G,2,a,iii.

[01018] Liquid-refrigerant diverter valve 655h and cabin-heating fan 552h are controlled manually or automatically by the cabin climate-control system. Valve 477 is operated in the same way in all modes where the system's CCU is energized, namely in all modes except mode 0*_0A. And the clutch of pulley-and-clutch 621 is engaged in all control modes except mode 0*_0B. The remaining system-controllable elements are controlled as described next.

[01019] In mode 0*_0A, no system-controlleable elements are controlled.

[01020] In mode 0*_0B, (1) pump 443 is controlled so that p*_R tends to p*_RD^o; (2) fan 510 does not run; (3) valve 555 is in position 1, namely liquid refrigerant entering at 556 exits at 557; and (4) valve 630 is in position 1, namely liquid refrigerant entering at 631 exits at 633.

[01021] In mode 1*_A, (1) pump 443 is controlled so that p*_R tends to p*_RD^o; (2) fan 510 does not run; (3) valve 555 is in position 2, namely liquid refrigerant entering at 556 exits at 558; and (4) valve 630 is in position 1.

[01022] In mode 1*_B (1) pump 443 is controlled so that p*_R tends to p*_RD^o; (2) fan 510 runs at a preselected effective capacity, or at a preselected speed; (3) valve 555 is in position 1; and (4) valve 630 is in position 2, namely liquid refrigerant entering at 631 exits at 632.

[01023] In mode 2*, (1) pump 443 is control led so that T_W tends to T_WD; (2) fan 510 does not run; (3) valve 555 is in position 1; and (4) valve 630 is in position 2.

[01024] In mode 3*, pump 443 is controlled so that p*_GR stays close to p*_GR,MAX; (2) fan 510 is controlled to that T_W tends to T_WD; (3) valve 555 is in position 1; and (4) valve 630 is in position 2.

[01025] The transition rules between control modes are:

[00002]

(a)	0*OA to 0*OB	: engine starts running
(b)	0*OA to 1*A, 1*B, 2*, or 3*	: no transition
(c)	0*OB to 1*A or 1*B	: no transition
(d)	0*OB to 2*	: TW > TWD,1
(e)	0*OB to 3*	: no transition
(f)	1*A to 1*B, 2*, or 3*	: no transition
(g)	1*B to 2* or 3*	: no transition
(h)	2* to 3*	: p*GR = p*GR,MAX and TW = TWD +
		ΔTW1
(i)	0*OB to 0*OA	: engine stops running
(j)	1*A to 0*OA	: engine not running and clock stops
		running
(k)	1*B, 2*, or 3* to 0*OA	: no transition
(l)	1*A to 0*OB	: engine starts running
(m)	1*B, 2* or 3* to 0*OB	: no transition
(n)	1*B to 1*A	: TW < TWD,2
(o)	2* or 3* to 1*A	: no transition
(p)	2* to 1*B	: engine stops running
(q)	3* to 1*B	: no transition
(r)	3* to 2*	: TW < TWD − ΔTW2

In transitions (e) and (r), ΔT_W1 and ΔT_W2, respectively, are small positive values.