Dual Pump for Two Separate Fluids With Means for Heat Exchange Between the Fluids

This invention relates to heat exchangers using peristaltic pumps to circulate a separate fluid on opposite sides of a heat-conductive wall and enhance heat transfer rates between the fluids. In the prior art there are many types of peristaltic pumps; Bogachev U.S.S.R., Pat. No. 118704 discloses a pump using an elastic casing squeezed from opposite sides by spherical rollers whereby the casing is extended to sealing contact, generating a peristaltic pumping action; in a second version, cylindrical rollers deflect a double-convex casing to sealing contact but also spreads the casing laterally: This is unlike the invention; in Bogachev's patent there is no possibility of heat-exchange between two fluids. Other peristaltic pumps roll-down a flexible tubing or deform it rythmically with cam-actuated fingers to move a fluid, substantially unlike the invention. Peristaltic pumps also generally have high running friction, short life of the elastomer and low speed and pressure output, deficiencies substantially overcome by the invention. Heat exchangers are not known to use peristaltic pumps and most often are passive elements where fluids must be circulated by outside means; also heat transfer rates suffer by incomplete turbulence of the fluids. Peristaltic pumping of the invention substantially overcomes these deficiencies.

Running rollers deflect a linear diaphragm to sealing contact with a heat-conductive platen and form moving volumetric chambers between rollers. A primary fluid is circulated on one side of the platen; similarly a secondary fluid is circulated on the other side. Heat is transferred thru the platen between the fluids. Each pump features a flat elastomeric diaphragm which is being made to bulge by increasing its width by the squeezing of its edges, forming the working chamber. Pins in combination with fixed cams provide a deformable structural ceiling for the diaphragm and shape the working chamber. During operation, the rollers deflect the pins which in turn flatten and contract the diaphragm to sealing contact with the platen. When released from the sealing contact, the diaphragm resiliently bulges away from the platen to produce a vacuum and fill the chamber. One object of the invention is to improve on prior art peristaltic pumps by providing lower rolling friction, lower wear, higher speed and pressure output.

Another object of the invention is to improve on prior art heat exchangers by providing an accelerated rate of heat transfer, yet integrating means of pumping processed fluids at the same time.

Another object is the ability of handling gases and two-phase fluids, compressing or expanding them at variable rates, while exchanging heat, to achieve improved thermodynamic cycles.

Finally to make this invention simple, easy to fabricate and low in cost.

FIG. 1 is a plane view of a form of heat exchanger according to the invention.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1.

FIG. 3 thru FIG. 7 are magnified cross-sectional views taken respectively along line 3--3 thru 7--7 of FIG. 1.

FIG. 3 thru FIG. 7 illustrate the building steps of a form of the invention. Referring to FIG. 3, flat elastomeric diaphragm 1 is laid on both sides of a heat-conductive platen 2. In FIG. 4 clamp bars 3A, 3B and cam bars 4A, 4B, 5A, 5B are installed as shown and fastened with screws 6. As the screws are tightened the clamp bars exert pressure on the diaphragm edges displacing some of the elastomer outside the clamping area, thus increasing the effective width of the diaphragms and making each diaphragm bulge. This forms, with the platen, two conduits along the linear extent of said platen. The diaphragm material is a hard elastomer preferably of the "Elastoplastics" type such as polyurethane, copolyester, or even the softer plastics such as the fluoroplastics, in the preferred hardness range of 90A to 55D. Both diaphragms should be of the same durometer but to illustrate an example in FIG. 4, the upper diaphragm is harder than the lower one; under the clamping pressure the lower diaphragm will have more elastomer displaced than the upper one and consequently the lower bulge will be greater than the upper one. In FIG. 5, pins 7 are added, they are missing in FIG. 4 to show the free bulging of the diaphragm, but should be installed at the same time as clamp bars and cam bars. The cam bars have closely spaced slots 12 of varying depth which guide and retain the pins. During assembly the pins flatten and shrink the bulge to a variable distance from the platen. This distance or working stroke is a small percentage of the free bulge height. For the harder upper diaphragm the bulge is simply flattened and shrunk. For the softer lower diaphragm the bulge top collapses and forms a multi-node shape. In FIG. 6, running rollers 8 deflect the pins which in turn depress the diaphragm to sealing contact with the platen. The diaphragm springs back or bulges behind the rollers, thus causing a suction or vaccum which fills the pumping chamber formed thereby, and thus renders the pump self-priming and capable of continuous pumping without the requirement of positive pressure on the fluid at the inlet. The softer diaphragm although multi-node reduces the area or lumen of the working chamber, it provides for a strong spring-back and a consequent strong suction. In FIG. 7, end blocks 9A and 9B are closing both ends and both sides of the assembly to establish inlets and outlets by letting the diaphragm expand in cavities leading to ports. In FIG. 2, showing a length-wise cross-section of the invention, it can be seen that the fluid 1 working chamber is tapered from the inlet to the outlet: This is determined by the cam bar slots which are guiding and retaining the pins. Change in the depth of the cam bar slots will produce a different working chamber shape. Fluid 2 working chamber is uniform. It is now particularly called to attention that one feature of the invention is to use a low-cost flat diaphragm that can be made to bulge to form the working chamber and furthermore, in combination with pins and cams, that the working chamber can be shaped to any configuration, especially important for the process of gases to obtain various volumetric ratios and pressure curves. It can be seen that under the roller action the diaphragm flattens and shrinks completely to sealing contact with the platen without spreading out laterally but gets slightly thicker than the original thickness in the process, because of the contraction. Equally spaced rollers 8 with reaction rollers 10 form part of a conveyor system with drive and idle sprockets, including a reaction track 11, adjustable to position the rollers for correct occlusion of the diaphragm; as this is known technology, it is not fully shown. A separate conveyor running in opposite direction is used for each fluid to increase the heat transfer by the well known counter flow principle. Another advantage of diaphragm, pins and cams combination is a lower rolling friction and lower wear due to the interrupted progression of the diaphragm squeeze by separated pins: this allows the overoccluded elastomer to expand between pins rather than to extrude under the roller. It also eliminates the "fold effect" which a roller produces on a flexible tubing and which makes the tubing creep ahead of motion; since the tubing end is fixed, the creep length must be swallowed by extrusion under the roller and results in added friction. The invention decouples roller from elastomer to avoid the "fold effect". The pins provide a strong ceiling for the diaphragm and with a low dynamic elastomer deformation the result is that speed and output pressure are higher than usual peristaltic pumps. Most importantly, heat transfer is maximized because of high velocity, hydrodynamic effect and full fluid turbulence by the rolling action. A typical operation is shown in FIG. 2. Running rollers progressively flatten a portion of the elastomer along the linear extent of the platen to produce moving volumetric chambers. Gaseous fluid 1 is inducted into an enlarging chamber until the next roller blocks the inlet and a volume VI is trapped; because of the shape of the working chamber, determined by the cams and pins combination, volume VI is compressed until roller opens the outlet at volume V2 achieving a compression ratio of V1/V2. Similarly on the other side a fluid 2, now a liquid, enters the enlarging chamber until next roller traps the liquid at volume V3. The volumetric chamber is now kept parallel by the cams and pins combination so as not to compress a liquid; volume V3 is circulated until roller opens the outlet and squeezed out. Fluid 1 and 2 move in opposite directions to each other for counterflow advantage. During operation heat of compression is rejected to the cooling liquid to achieve a near-isothermal process. The invention is reversible; a compressor can be made an expander by feeding compressed gas at the former compressor outlet; in an action opposite to the compressor, compressed gas will be expanded in the now expanding working chamber while the diaphragm will transmit gas pressure to the roller for motor action, so the expander will move in a direction opposite to the compressor. Heated liquid can be used to heat the expanding gas near-isothermally and increase the work output such as in heat engine application, or the liquid can be cooled by the expanding gas in heat pump application. Although not shown, it is within the scope of this invention to expand the present embodiment into a heat pump or heat engine based on the Stirling or similar cycles. The Stirling heat engine cycle uses these processes in succession: isothermal compression (cooled)-constant-volume (heated)-isothermal expansion (heated)-constant-volume (cooled). All these processes are nearly achievable in the invention by modulating the working chamber with the pins and cams combination, at the same time providing the required cooling or heating. Heat engine may be especially well adapted to work with low-grade temperature heat sources such as solar energy and working gas may be a two-phase refrigerant. The invention described can also be arranged in obvious other configurations from straight linear to cylindrical linear or annular linear. The annular linear embodiment would have a compact size for lighter applications; it could use orbiting conical rollers carried by spiders rather than the larger size conveyor system. The cylindrical linear configuration would also use orbiting rollers, arranged inside and outside the cylinder, carried by spiders in the general manner suggested by the said U.S.S.R. disclosure, either with or without the roller equalizing means therein shown. In all modifications the linear paths of straight or annular or cylindrical would have a corresponding linear path for the pumping conduits. The term "pump" as used herein also includes "motor" since the same structure operating in the same way will extract, as well as add, energy to a fluid stream.