Method for Suppressing the Formation of Ice in Natural or Man-Made Bodies of Water

1. Field of the Invention

This invention relates to a method of suppressing the formation of ice in natural or man-made bodies of water, with particular reference to the use of heat transfer means for direct replacement of heat lost to the atmosphere during cold winter season when the air temperature is below that necessary for the formation of ice in said bodies of water.

2. Description of the Prior Art

Means for providing extended or possibly winterlong navigation for commercial shipping in water-way systems located in cold climate areas becomes an increasingly desirable factor as the systems are developed for man's use. This is particularly true in view of the relatively high cost of land based commercial shipping systems.

Ice begins to form when the air temperature is well below freezing and the water temperature is close to freezing. The most favorable conditions for ice formation are a clear, cold night with little or no wind. Ice sheets form first in sheltered areas such as harbors or bays. Whether an ice cover forms or does not form across a river or canal depends on the temperature of the air, the temperature of the water, the velocity of the wind, and the velocity and turbulence of the water. In any event, once an uncontrolled ice cover has formed, continued air temperatures below the freezing point of water will cause the ice cover to grow larger and thicken to the point where continued navigation by commercial shipping is impossible.

Extension of the navigation season or possible winter-long navigation requires maintenance of bays, harbors, and canals, locks or rivers connecting larger bodies of water. In large bodies of water away from shore areas, the winter ice cover is rather thin or discontinuous and can be easily traversed by commercial ships. It is in bays, harbors, shipping locks, canals and rivers that thick ice covers pose a major problem. Ice-breakers have been used to keep bays, harbors, canals, locks and rivers open, but repeated passages in the same track can cause weakening and damage to side retaining walls and shore areas. In addition, certain restricted areas cannot be reached with ice breakers. Bubbler systems for airlifting warm bottom waters to the surface and dusting techniques to prevent ice cover formation have been used with varying degrees of success but are expensive to maintain and sensitive to changes in weather and water conditions.

In general, the present invention provides a method for suppressing the formation of ice in natural or man-made bodies of water such as lakes, rivers, sounds, straits, bays, shipping canals, shipping locks, harbors and the like. The method is particularly useful in areas where ice breakers or the like cannot be efficiently operated.

The method provides for the direct replacement of heat lost to the atmosphere from a body of water during cold seasonal days when the air temperature is below that necessary for the formation of an ice cover on said body of water. This replacement of heat results in maintaining the upper layer of water in the body of water just above freezing, thus suppressing the formation of an ice cover therein. By relating heat losses to differences in temperature between air and water, the rate of transfer of heat between surfaces of various bodies of water and the atmosphere can be established with a fair degree of accuracy. It has been found that this rate may be taken at about 95 British Thermal Units (B.T.U.), transferred per day per square foot of water surface per degree fahrenheit, and is independent of the surface character of the body of water in question, that is, the surface of rapids, the surface of lakes, and the surface of smooth sections of canals or rivers all have about the same cooling coefficient or ratio of heat transfer.

The present invention takes advantage of low level thermal energy sources by using liquid compositions to store heat near the body of water in which it is desired to suppress the formation of an ice cover. The compositions freeze substantially above 0.degree.C. (32.degree.F.) and have relatively large latent heats of fusion associated with their melting and freezing phase change, which heat can be transferred to the surface layer of the body of water by heat transfer means. Heat transfer apparatus may be utilized which is of a permanent type located in retaining side walls and/or in the top layer of water adjacent the sides of a body of water to prevent natural bridging of an ice cover on the same or may be a traveling heat exchanger disposed in a barge, scow or the like which moves along a desired path in a body of water. When a traveling heat exchanger is used such as a barge or scow, it is necessary to utilize intermediate compositions which have freezing temperatures substantially above 0.degree.C. (32.degree.F.) but below that of the compositions which are used to store heat near a body of water. By utilizing the release of the relatively large latent heats of fusion of the compositions when they freeze coupled with the temperature differencial driving forces from the freezing temperature of the storage compositions to the freezing temperature of the intermediate compositions, if used, and then to the water which is just above freezing, a large heat transfer can be accomplished from the heat storage compositions to a body of water.

Many compositions useful in the present invention are described in a copending application Ser. No. 268,468, filed July 3, 1972, issued as U.S. Pat. No. 3,834,456 on Sept. 10, 1974, entitled "Aqueous Organic Heat-Sink Fluids" by Ewart C. Clarke and David N. Glew, which application is herein fully incorporated by reference. The compositions described in the copending application are single-phase solutions comprising water and at least one organic component which are mixed in proportions such that a homogeneous, crystalline, ice-like solid hydrate is formed upon freezing. The aqueous organic compositions have latent heats of fusion in the order of about 140 B.T.U. per pound. Examples of compositions found in the copending application which are particularly useful in the present invention are mixtures comprising one mole of pinacol and six moles of water which composition freezes at about 45.degree.C. (113.degree.F.), and one mole of butane-2,3-diol and six moles of water which composition freezes at about 14.degree.C. (57.degree.F.). Another beneficial property of many of the organic compositions described is a relatively low percent expansion or contraction of the same during freezing which significantly reduces mechanical stress on their encapsulating structures.

The thermal energy source utilized to regenerate or melt the heat storage compositions can be provided in numerous ways as, for example, from condenser water of steam power plants, nuclear energy power reactors, solar energy, exhaust gases or cooling water of deisel engines or the like and direct heating with fossil fuels. The thermal energy sources may also be used in combination as, for example, where solar energy, used as the primary source to regenerate or melt the storage compositions, is supplemented with fossil fuel heat during peak loads when the available solar energy is inadequate.

In addition, warm bottom waters may also be pumped to the surface and used in combination with fixed position or traveling heat exchangers to relieve the strain on other thermal energy sources. In some instances, it may even be practical to use bottom water as a primary thermal energy source to regenerate or melt the heat storage compositions of the fixed storage facilities or the traveling heat exchanger as, for example, where bottom water from a large industrial holding pond is used to melt the heat storage composition in a barge heat exchanger. Of course, the extent bottom water is utilized in combination with other thermal energy sources is governed by its temperature and location relative to the area where an ice cover is being controlled.

The objects and advantages of the present invention are even more apparent when taken in conjunction with the accompanying drawings in which like characters of reference designate corresponding materials and parts throughout the several views thereof, in which:

FIG. 1 is a schematic representation of a barge constructed as a traveling heat exchanger according to principles of the present invention;

FIG. 2 is a cross-sectional schematic representation of a large heat storage unit and regeneration system, and a heat exchanger barge illustrating the method of transferring heat from the storage unit to the barge;

FIG. 3 is a partial plan view illustrating a canal in which ice cover formation is suppressed by direct transfer of heat from a heat storage unit to heat exchanger means in the retained side walls and in the water adjacent said side walls;

FIG. 4 is a plan view illustrating a modified traveling barge heat exchanger which incorporates side distribution booms to increase the effective width of coverage of the same; and

FIG. 5 is a partial isometric view illustrating another modified traveling barge heat exchanger which incorporates a submerged pumping unit to pump bottom water into the distribution tubes of the barge.

The following description illustrates the manner in which the principles of the invention are applied but are not to be construed as limiting the scope of the invention.

More specifically referring to FIG. 1, a traveling heat exchanger 10 in the form of a self propelled barge 12 which is utilized to transfer heat to the top portion of a body of water 14 is illustrated. The barge 12 has heat exchanger conduits 16 through which water from the body of water 14 passes and absorbs heat. Barge 12 is substantially filled with an aqueous organic composition 18 comprising one mole of butane-2,3-diol and six moles of water which freezes at about 14.degree.C. (57.degree.F.) and has a latent heat of fusion of about 140 B.T.U. per pound. The barge 12 also includes a cover 17, a flow control device 11 to control the flow of water through conduits 16, a heat regeneration unit 13, only partially represented to avoid unnecessary detail, which is used to supply heat from an external source to the composite 18, and a deisel engine 15 used to drive the barge 12. The cooling system 19 of the deisel engine 15 is tied into the regeneration unit 13 in order to take advantage of the waste heat generated in the same by transferring it to the composition 18. Other conventional details of the barge 12 such as a cabin, steering mechanism, signal lights, anchors and the like are not shown so that the more important functional elements can be clearly illustrated. The barge 12 and other functional elements therein can be made from the usual construction materials such as steel.

Referring now to FIG. 2, a heat storage unit 20 which is used to supply heat to the barge 12 is illustrated. The reference numerals illustrating the parts of barge 12 are the same as shown in FIG. 1. The storage unit 20 includes a tank 21 which has insulated walls 22 (insulation not shown) to prevent excess heat loss to the atmosphere during cold weather. The tank 21 is substantially filled with an aqueous organic composition 23 comprising one mole of pinacol and six moles of water which freezes at about 45.degree.C. (113.degree.F.) and has a latent heat of fusion of about 140 B.T.U. per pound. The heat storage unit 20 also includes solar energy collectors 24 as the primary means for accumulating stored heat in composition 23, a secondary thermal energy unit 27 such as a fossil fuel furnace to supplement the solar energy collectors 24, heat transfer lines 25, a centrifical pump 26, couplings 28 and valves 29-33.

The present invention is based on a principle of storing large quantities of heat near its point of use in the form of latent heat of fusion of the compositions 18 and 23. What this means is, that in carrying out the present invention, the compositions 18 and 23 are allowed to freeze, thus releasing their relatively large latent heats of fusion which are introducted into and/or near the area necessary to suppress ice cover formation on the body of water 14. Of course, the compositions 18 and 23 also supply heat from their liquid phases when utilized at temperatures in excess of their freezing points, but the quantity supplied would generally be small in comparison with that supplied by their latent heats of fusion. In addition, the freezing temperatures of the compositions 18 and 23 are sufficiently high to provide an adequate driving force differential temperature to accomplish the require heat transfer.

Heat should be stored in composition 23 during warm weather when the air temperature is above 0.degree.C. (32.degree.F.). The number and size of the solar energy collectors 24 and the secondary thermal energy unit 27 will depend on the amount of heat which must be stored, but, in any event, should be sufficient to melt the composite 23 before cold weather sets in when the air temperature is below 0.degree.C. (32.degree.F.). The heat is transferred from the collectors 24 and unit 27 by an intermediate transfer fluid, such as a common glycol-water solution, disposed in transfer lines 25. During storing of heat in composition 23, valves 30, 32 and 33 are closed and valves 29 and 31 are open. The centrifical pump 26 then continuously pumps the transfer fluid through transfer lines 25 moving the heat from collectors 24 and thermal energy unit 27, if used, into the composition 23.

During the cold weather season, heat is transferred from the barge 12 to the water adjacent the surface of the body of water 14 until the composition 18 is completely frozen. The barge 12 is then moved into position adjacent the retaining wall 37 of the body of water 14 and coupled to the heat storage unit 20 through couplings 28. The composition 18 is then regenerated or melted by transferring heat through transfer lines 25 and regeneration unit 13. To accomplish this, valves 29, 32, 33, 34 and 35 are opened and valves 30, 31, and 36 are closed. Thereafter, pump 26 continuously pumps the intermediate transfer fluid through transfer lines 25 and the regeneration unit 13 until sufficient heat has been transferred to melt composition 18. The valve procedure is reversed to place barge 12 back in operation on the body of water 14.

Referring now to FIG. 3, a modification of the present invention incorporating permanent heat transfer systems in a partial section of a shipping canal 40 is illustrated. This modification provides for the use of permanent heat exchangers 42 and 43 located in retaining side walls 45 or in the top layer of water 44 adjacent the side walls 45, respectively, to prevent natural bridging of an ice cover between the side walls 45. Heat storage tanks 21 of the same type shown in FIG. 2 and direct transfer lines 41 are used to transfer heat to the heat exchangers 42 and 43. Piles 46 are included to protect heat exchangers 43 from damage by ships passing through the canal 40. By preventing the formation of natural bridging between the retaining side walls 45, any ice cover that forms in the canal 40 will be carried by the current of the water 44 into larger connecting bodies of water where it can be easily traversed by ships or, if necessary, broken up with an ice breaker.

Referring to FIGS. 4 and 5, two modified versions of barge 12 are illustrated. The barge 12 shown in FIG. 4 incorporates means to increase the width of its effective path over that defined by the normal flow of heated water 43 through the same. To this end, the barge 12 includes distribution conduit booms 41 located on each side of the same. The booms 41 are coupled by rotatable joints 42 to the heat exchanger conduits 16, shown in FIGS. 1 and 2, in barge 12 thereby providing distribution of heated water streams 44 from the sides of barge 12. The rotatable joints 42 allow the booms 41 to be rotated as much as 90.degree. away from the sides of barge 12, thus providing significant control of the effective width covered by barge 12.

The barge 12, shown as a partial isometric section of the front end thereof in FIG. 5, incorporates means for pumping warm bottom waters up to and through the heat transfer system of barge 12. The bottom water pumping system includes a raising and lowering mechanism 51, a receiver-distributor tank 52 and a pump platform 53 having a submergible pump 54 and an intake 55. The pump platform 53 is also shown in phantom line in its lowered position. Other details such as additional super structure, a temperature indicator to locate the warmest bottom water and a sonar sensor device to control the depth of the pump platform 53 are not shown in FIG. 5 and would be a matter of choice to persons skilled in the art. Other value means not shown are also provided in the receiver-distributor tank 52 to control the flow of bottom water to conduits 16 in barge 12 either as the total flow thereto or in combination with other surface water introduced into the system. Additional value means may also be provided in tank 52 for diverting the bottom water through the heat regeneration unit 13 of barge 12, shown in FIGS. 1 and 2, when the bottom waters are used to melt or regenerate the heat storage composition of barge 12.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.