US3788385A

US3788385A - Dry type, liquid-solid cooling system

Info

Publication number: US3788385A
Application number: US00091931A
Authority: US
Inventors: T Delahunty
Original assignee: Chicago Bridge and Iron Co
Current assignee: Chicago Bridge and Iron Co
Priority date: 1970-11-23
Filing date: 1970-11-23
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: AU448009B2; AU3391571A; CA946732A; DE2138903A1; NL7110695A; GB1300899A

Abstract

To cool a hot first material it is brought into heat exchange with a particulate solid second material which liquefies through such heat exchange, the liquefied second material is removed from heat exchange with the first material, cooled and converted into solid particulates, and the solid particulates of the second material are brought into heat exchange recontact with the hot first material. The system is useful in the cooling of hot water from an electric power generating plant.

Description

United States Patent Delahunty Jan. 29, 1974 DRY TYPE, LIQUID-SOLID COOLING SYSTEM Primary ExaminerCharles Sukalo Attorney, Agent, or FirmMerriam, Marshall, Shapiro [75] Inventor. 'IIllerry Wayne Delahunty, La Grange, & Klose [73] Assignee: Chicago Bridge & Iron Company,

Oak Brook, Ill. [57] ABSTRACT To cool a hot first material it is brought into heat ex [22] Flled' 1970 change with a particulate solid second material which [21] Appl. No.: 91,931 liquefies through such heat exchange, the liquefied second material is removed from heat exchange with the first material, cooled and converted into solid parg 165/2 161/ ticulates, and the solid particulates of the second ma- [58] Fie'ld 2 1 104 terial are brought into heat exchange recontact with the hot first material. The system is useful in the cool- [56] References Cited ing of hot water from an electric power generating FOREIGN PATENTS OR APPLICATIONS 9/l959 Great Britain 165/107 plant.

29 Claims, 5 Drawing Figures PRIMARY COOLANT AIR A I\ A T PROCESS STEAM STEAM TURBINE a CONDENSER PROCESS 4/ l5 INTERMEDIATE COOLANT Pmmmmem Y 3.788.385

SIIEEI 1 0F 3 F [GI 28 PRIMARY COOLANT 2 A A A ,26 IO VAIR PROCESS STEAM \A A A T \27 l8 II STEAM TURBINE a j 24 22 Q CONDENSER '4 2o 25 '23 2 PROCESS H20 4/ I5 INTERMEDIATE COOLANT PROCESS STEAM STEAM TURBINE 8 CONDENSER PROCESS H20 INTERMEDIATE COOLANT INVENTOR. TERRY WAYNE DELAHUNTY BY WW, WMJMfK/M ATTORNEYS.

PATENTEDJMQIQM 3788585 saw 2 BF 3 PRIMARY COOLANT 6O STEAM AIR 40 1 56 SLURRY 42 FLgW; I I (r l '5l Y INTERMEDIATE COOLANT 55 FIG-4 INTERMEDIATE COOLANT 55 INVENTOR. TERRY WAYNE DELAHUNTY B I W, WMMJWdKM ATTORNEYS.

' 58 f PRIMARY COOLANT STEAM PATENTEUJAM 2 9 1914 3788.385

snmaora INVENTOR. TERRY WAYNE DELAHUNTY ATTORNEYS.

DRY TYPE, LIQUID-SOLID COOLING SYSTEM This invention relates to processes and systems for cooling. More particularly, this invention is concerned with processes and apparatus useful for removing heat from a cooling fluid, such as is employed in power generating plants.

There are many instances in which it becomes necessary to remove heat in material processing operations as well as heat from electric power or steam generating plants. The heat removal is generally accomplished by means of an intermediate cooling fluid, which can be a gas but most often is a liquid i.e. water, although other liquids are also used. After the intermediate cooling liquid has absorbed heat, its reuse as a cooling liquid requires that its heat content be reduced to an acceptable level. This can be achieved by a number of procedures but for large scale cooling it is common to cool the liquid in a cooling tower which employs air as the heat sink.

The previously described cooling system can be illustrated further by reference to a power generating plant. In the production of electric power, heat is first produced by atomic energy or combustion of a fossil fuel such as oil or coal. The heat produced is then used to convert water into steam. The steam is conducted at high pressure to a turbine which it drives. The turbine is of course coupled to a generator which produces electric power. The spent steam from the turbine is then condensed by indirect heat exchange with cooling water. The condensed steam is recycled and reheated to steam again. The cooling water becomes very hot in condensing the steam. The large amount of hot water is commonly disposed of, without significant cooling, into rivers and lakes but this is undesirable in some areas because it causes the temperature of natural bodies of water to rise excessively leading to ecological imbalance. In the newer power generating plants the hot water is cooled in an evaporative cooling tower by contacting it with a stream of air. Huge hyperbolic natural draft cooling towers are now quite extensively used for this purpose. While a large amount of the hot water is cooled in this manner, extensive amounts are expelled as water vapor forming huge artificial clouds which contaminate the atmosphere for miles, form fog and condense to artificial rain. An evaporative cooling tower serving a 1,000 megawatt electric generating plant intrudes approximately 900,000 gallons per hour of water vapor into the atmosphere, causing not only air pollution but a significant usage of water resources. Also, the emissions contain minute droplets of dirty circulating water, called drift, which adds 100,000 gallons per hour to the water consumption rate and also carries 1.6 tons per day of solids into the air. A cooling system is thus required which reduces or avoids the problems and disadvantages present in the described methods.

According to the present invention there is provided a novel cooling method, and apparatus therefore, which provides advantages over prior cooling methods and which lowers or eliminates undesirable characteristics or short-comings of other processes. The cooling method of the present invention is broadly characterized by the use of a material as a primary coolant which is a solid at ambient temperature and pressure. The coolant is employed as solid particulates which become melted and liquid while providing cooling by absorbing heat from a hot material. The cooling ability i.e. the

heat absorbing capacity, of the solid particulates is very high because of the heat of fusion as well as sensible heat absorbed by the melted particulates. After the coolant has absorbed heat and has become liquefied it is reconverted by cooling into solid particulates. The solid particulates can then be recycled into heat exchange with the hot material. Cooling of the liquefied solid material is advisably, but not necessarily, accomplished in a cooling tower by means of air flow. Since the coolant is a solid at ambient temperature, no undesirable water vapor, clouds or fogs are emitted from the cooling tower to contaminate the atmosphere. Instead, contact with air flowing through the tower cools the material to solid particulate form. The particles settle by gravity and are reused for further cooling. Only hot air need be expelled from the tower under properly controlled operation.

The invention in a broad embodiment thus comprises a process of cooling a hot first material in which the hot first material is brought into heat exchange relationship with a stream of particulate solid second material which liquefies through such heat exchange, the stream of liquefied second material is removed from heat exchange with the first material, the liquefied second material is cooled and converted into solid particulates and the solid particulates are recontacted in heat exchange with the hot first material. Advisably, the first material is a liquid, and the second material is a solid, at ambient temperature. Furthermore, the heat exchange between the first and second materials is advisably effected by direct contact between these materials. It is also an important feature of the invention to employ first and second materials which remain essentially mutually insoluble during the process. When the process is employed in a power generating plant the first material is advisably water and the second material is one which is essentially insoluble in water. It is also advantageous that the second material be one which has a specific gravity less than water.

When the heat exchange between the first and second materials is effected by direct contact between the materials, they can be separated by gravity settling, centrifugation or some other suitable means. When gravity settling is used, the layer of first material can be circulated through a power generation plant as an intermediate coolant to condense spent steam. The liquid layer of normally solid second material can be dispersed, as by spraying, with cooling to form solid particulates which can then be recycled and reused for cooling as appropriate.

It is also an aspect of the invention to effect cooling by means of a dispersion or slurry of the solid particulate material in a separate liquid which can be water in the case of a power generating plant. An aqueous dispersion of the solid material can be used to condense spent steam. The absorbed heat melts the solid material and results in a liquid-liquid dispersion. This liquidliquid dispersion is then separated into its components and the liquid formed from the normally solid material is cooled and reconverted into solid particulates. The solid particulates can then be reused in forming a coolant dis-persion in water.

The invention will now be described further in conjunction with the attached drawings in which:

FIG. 1 illustrates one embodiment of the invention as applied to a power generating plant in which an intermediate coolant (water) is cooled by solid particulate material which thereby melts and is thereafter reconverted to particulate material;

FIG. 2 is similar to FIG. 1 except that in the embodiment of FIG. 2 the liquefied solid material is sprayed upwardly, instead of downwardly as in FIG. 1, to cool and reform solid particulates;

FIG. 3 illustrates another embodiment of the invention in which a dispersion of solid particulates in water is used as a coolant to condense spent steam;

FIG. 4 is similar to FIG. 3 except that in FIG. 4 the solid particulates are reformed by spraying the liquefied solid upwardly in a cooling tower instead of downwardly as in FIG. 3; and

FIG. 5 illustrates still another embodiment of the invention using a dispersion of solid particulates in water as the coolant and a lake or river as the heat sink;

With reference to FIG. 1, process steam developed by heat from an atomic reactor or fossil fuel furnace (not shown) is delivered by conduit to combined steam turbine-condenser 11. The spent steam from the turbine is condensed and recycled by conduit 13 in a closed loop for reformation into steam. Cooling water is circulated through coils 14 to condense the spent steam. The water is thereby heated. The hot water leaves coils 14 by conduit 15 which conveys it into hyperbolic cooling tower 16. By means of sprayhead 17 located on the end of conduit 15 inside of the cooling tower the hot Water is sprayed downwardly onto a floating layer 18 of liquefied, normally solid, primary coolant material. The water is cooled as it drops downwardly by contact with solid particulates which form from liquefied primary coolant material sprayed from sprayhead 19. Additional cooling is effected when the hot water from sprayhead 17 contacts layer 18. The cooled water settles through layer 18 to provide a cooled water reservoir 20 in the bottom portion of the cooling tower. Cooled water is removed from reservoir 20 and conveyed by conduit 21, pump 22 and conduit 23 to condenser coils l4.

Liquefied solid material is removed from layer 18 by conduit 24, pump 25 and conduit 26 and isconveyed to sprayhead 19 from which it is sprayed to form small droplets which are cooled by air entering cooling tower ports 27 and flowing upwardly countercurrent to the downward flow of the droplets and out mouth 28. The small droplets solidify as they fall through the air. These solid particulates then fall through the hot water spray emitted from sprayhead 17 thereby cool the hot water. In doing so the solid particles are liquefied or melted and combine with layer 18 of melted primary coolant.

The solid primary coolant used in the process described in conjunction with FIG. 1 should not be soluble in water, should have a specific gravity less than water, be non-corrosive, be nontoxic with essentially no odorous fumes, be essentially non-oxidizing and have appropriate thermal properties. It can be an inorganic or organic material. Its melting point should be generally no less than 10F. above the seasonally highest ambient temperature. For example, during the summer months, the melting point might be 1 10F. while during the winter months, the melting point might be 60F. Some representative materials which can be used are butyl stearate (s.g. 0.855; m.p. 68F), docosane (s.g. 0.778; 112F), tricosane (s.g. 0.779; m.p. ll8.4F) and cetyl alcohol (s.g. 0.818; m.p. 120F). It is also feasible to use industrial paraffin waxes which are blends of the pure paraffin waxes such as docosane, tricosane and other materials.

The system shown diagrammatically in FIG. 2 is essentially identical to that shown in FIG. 1 so that the same identifying numbers have been used for the same elements. The only difference between the figures is that sprayhead 30 in FIG. 2 sprays the melted or liquefied primary coolant upwardly instead of downwardly as does sprayhead 19 in FIG. 1. Upward spraying may be more useful since it provides more time for the droplets to be in contact with the cooling air.

Another embodiment of the invention is shown in FIG. 3 in which process steam is conducted by conduit 40 to combined turbine-condenser 41. Spent steam from the turbine is condensed by cooling coil 42 and the condensed water is recycled by conduit 43 in a closed loop for regeneration into process steam by an atomic reactor or fossil fuel furnace.

Solid particulate material 44 in the bottom portion of cooling tower 45 is conveyed by conduit 46 to the intersection 47 with conduit 48. Water is supplied by conduit 48 to intersection 47. The solid particulates mix with the water at intersection 47 to form a slurry or dispersion which is conveyed by conduit 49 to coil 42. The solid particulates in the dispersion melt or liq uefy in coil 42 to form a liquid-liquid dispersion. This dispersion is conveyed from coil 42 by conduit 50 to reservoir tank 51. The liquid-liquid dispersion separates into two layers in tank 51 with the water layer 52 below the layer 53 of liquefied solid material which of course in this instance must have a specific gravity less than water and be insoluble in water. Water is conveyed from layer 52 by conduit 54 and pump 55 to conduit 48 for recycling.

Liquefied material is conveyed from layer 53 by conduit 56, pump 57 and conduit 58 to sprayhead 59 from which it is sprayed into hyperbolic cooling tower 45. As the spray falls downwardly it is cooled by air which enters the cooling tower through ports 60 and flows upwardly and out tower mouth 61. This cooling converts the material into solid particulates which settle onto the reservoir 44 of solid particulates. This system avoids emission of water vapor into the atmosphere and the artificial formation of fog and rain. It also provides excellent cooling because of the large amount of heat which can be absorbed as sensible heat and heat of fusion by the conversion of the solids to a liquid.

The system of FIG. 4 is identical to that shown in FIG. 3 with one exception. The exception is sprayhead in FIG. 4 which sprays the liquefied solid material upwardly instead of downwardly as is done by sprayhead 59 in FIG. 3.

FIG. 5 illustrates still another embodiment of the invention. In this embodiment, process steam is conveyed by conduit to combined turbine-condenser 81. The spent steam from the turbine is condensed by coils 82 and the resulting water is conveyed by conduit 83 in a closed loop for reconversion into steam.

Conduit 84 conveys a liquid-liquid dispersion or slurry from coil 82 to sprayhead 85 located below the surface of a body of water such as a river or a lake. Vertical wall 86, surrounding sprayhead 85, has its bottom edge raised above the bed of the body of water so that cool water can circulate thereunder and flow upwardly within the space enclosed by wall 86.

The liquid-liquid dispersion sprayed from sprayhead 85 consists of water and a liquefied or melted solid material dispersed therein. The cooling effect of the river or lake water solidifies the liquefied solid material into solid particulates which float as a mass 87 on the body of the water. Wall 88 surrounds an area wider than that surrounded by wall 86 to assure retainment of the floating particulates without escape. Wall 88 extends above the surface of the body of water sufficiently far to prevent loss of the floating particulates through wind or wave action. The lower edge of wall 88 is spaced outwardly from, and lower than, the upper edge of wall 86 to provide a path through which water can flow from within the space surrounded by wall 86 and beneath the floating particulate mass 87 to effect continual circulation of water.

An aqueous slurry or dispersion of the particulates is removed from the floating mass 87 by conduit 89, pump 90 and conduit 91 and conveyed to coil 82 for cooling and condensing the spent steam as previously described.

Solid materials which have already been described in conjunction with the system of FIG. 1 can be used equally well in the systems illustrated by FIGS. 2 to 5.

Although the invention has been described with particular reference to an electric generating plant it is not intended to restrict the invention to such use. The cooling system has much wider applicability whether the heat ultimately is exhausted to the air or to a body of water.

The embodiments which employ air-cooling permit a power company to choose a plant site away from water resources, often on less expensive real estate and in closer proximity to the electric consumers, thereby reducing transmission line costs. The expense of cooling water treatment facilities may be reduced and the plant may be located near to a fossil fuel source.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom as modifications will be obvious to those skilled in the art.

What is claimed is: l. A process of cooling a hot liquid first material, the material being liquid at the ambient temperature, comprising:

bringing the hot liquid first material into heat exchange relationship with a particulate solid second material which is solid at the ambient temperature and which liquefies through such heat exchange,

removing the liquefied second material from heat exchange with the first material,

cooling and converting the removed liquefied second material into solid particulates, and

recontacting the solid particulate second material in heat exchange with the hot liquid first material.

2. The process of claim 1 in which the heat exchange is effected by direct contact between the first and second materials.

3. The process of claim 2 in which the first material is water and the second material is essentially insoluble in water.

4. The process of claim 3 in which the second material has a specific gravity less than water.

5. The process of effecting heat exchange and cooling which comprises directly contacting a hot liquid first material, said material being liquid at ambient temperature, with a second material, which is solid at ambient temperature and essentially insoluble in the first material, in solid particulate form to liquefy the second material,

separating the liquid second material from the first liquid material,

cooling and converting the separated liquid second material into solid particulate form, and

recycling the solid particulate second material into contact with hot liquid first material.

6. The process of claim 5 in which the first material is hot water.

7. The process of claim 6 in which the hot water is an intermediate coolant obtained from a power generation plant.

8. The process of claim 5 in which the liquid second material has a specific gravity less than the hot liquid first material and the liquids are separated from each other by gravity.

9. The process of effecting heat exchange and cooling which comprises directly contacting a hot liquid first material, said material being liquid at ambient temperature, with a second material, which is solid at ambient temperature and essentially insoluble in the first material, in solid particulate form to liquefy the second material,

said liquid second material having a specific gravity less than the hot liquid first material,

separating the liquid second material from the first liquid material by gravity into two layers, circulating the liquid first material through a power generation plant as an intermediate coolant, dispersing and cooling the second material liquid layer in air into solid particulates, and recycling the solid particulates of the second material into contact with the hot first liquid material recycled from the power generation plant.

10. The process of claim 9 in which the first material is water and the second material melts at 10F above the ambient air temperature.

11. The process of effecting heat exchange and cooling which comprises spraying hot water obtained as an intermediate coolant from a power generation plant into intimate contact with a second material, which is solid at ambient temperature and essentially insoluble in hot water in solid particulate form to liquefy the second material,

separating the liquid second material from the water by settling the liquids into two layers in a reservoir chamber,

recycling the solid particulate second material into contact with hot water.

12. The process of claim 11 in which liquid second material from the layer thereof is removed and sprayed into a cooling tower through which air flows upwardly to cool the sprayed liquid second material into solid particulates.

13. The process of claim 12 in which the reservoir is located in the bottom portion of the tower.

14. The process of claim 12 in which the water is sprayed into contact with the solid particulate material in the cooling tower below the flow of air.

15. The process of claim 12 in which the solid particles fall downwardly countercurrent to the air flow.

16. The process of effecting heat exchange and cooling which comprises:

forming a dispersion comprising a first liquid material and a second solid particulate material dispersed in the first liquid material, said first material being liquid at ambient temperature and said second material being solid at ambient temperature and insoluble in liquid form in the first material, feeding the dispersion in indirect heat exchange through a heat source adequate to melt the second material to thereby form a liquid-liquid mixture,

separating the liquid-liquid mixture into liquid first material and liquid second material,

cooling and converting the liquid second material into solid particulate form,

recycling the solid particulate second material into contact with the separated liquid first material to reform the dispersion, and

repeating the described process.

17. The process of claim 14 in which the first material is hot water.

18. The process of claim 17 in which the hot water is an intermediate coolant obtained from a power generation plant.

19. The process of claim 17 in which the liquid second material has a specific gravity less than the hot liquid first material and the liquids are separated into two layers by gravity settling in a reservoir chamber.

20. The process of claim 19 in which the liquids are separated into two layers by gravity, the second material liquid layer is dispersed and cooled in air into solid particulates and the solid particulates are dispersed in liquid from the first material liquid layer to reform the dispersion.

21. The process of claim 17 in which the second ma terial melts at F. above the ambient air temperature.

22. The process of claim 16 in which liquid second material from the layer thereof is removed and sprayed into a cooling tower through which air flows upwardly to cool the sprayed liquid second material into solid particulates.

23. The process of claim 22 in which the solid particulates are removed from the cooling tower and dispersed in liquid first material withdrawn from the reservoir.

24. The process of effecting heat exchange and cooling which comprises:

feeding a dispersion comprising a first liquid material and a second solid particulate material dispersed in the first liquid material, said first material being liquid at ambient temperature and said second material being solid at ambient temperature, insoluble in and of a different specific gravity in liquid form than the first material, in indirect heat exchange through a heat source adequate to melt the second material to thereby form a liquid-liquid mixture,

spraying the liquid-liquid mixture into a reservoir of the first material having a temperature low enough to solidify the second material in particulate form dispersed in the reservoir of first material, and

removing particulate second material with liquid first material from the reservoir and refeeding it in indirect heat exchange through the heat source. 25. The process of claim 24 in which the second material has a specific gravity less than the first material.

26. The process of claim 25 in which the first material is water.

27. The process of claim 24 in which the heat source is a power generation plant.

28. The process of claim 27 in which the reservoir of the first material is a portion of a river or lake of fresh water.

29. A process of cooling a hot first material comprising:

bringing the hot first material into heat exchange relationship with a particulate solid second material which liquefies through such heat exchange,

recontacting the solid particulate second material in heat exchange with the hot first material.

@7 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION gatent :3 3,7 3 5 Dated January 29 1974 Inventor(s) Terry Wayne Delahunty ppears in the above-identified patent It is certified that error a hereby corrected as shown below:-

.and that said Letters Patent are I E" ,"1

line 63, "dis-persion" should be di spersior 1 --r;

Column 2,

line 18, "claim 14" should be -claim l6-'--.

Column 7,

Signedand sealed this zlst da 'oiE May l9"74.

(SEAL) Attest:

C.. MARSHALL DANN Commissioner'of Patents EDWARD M.FLETCHER,JR. Attesting Officer

Claims

1. A process of cooling a hot liquid first material, the material being liquid at the ambient temperature, comprising: bringing the hot liquid first material into heat exchange relationship with a particulate solid second material which is solid at the ambient temperature and which liquefies through such heat exchange, removing the liquefied second material from heat exchange with the first material, cooling and converting the removed liquefied second material into solid particulates, and recontacting the solid particulate second material in heat exchange with the hot liquid first material.

5. The process of effecting heat exchange and cooling which comprises directly contacting a hot liquid first material, said material being liquid at ambient temperature, with a second material, which is solid at ambient temperature and essentially insoluble in the first material, in solid particulate form to liquefy the second material, separating the liquid second material from the first liquid material, cooling and converting the separated liquid second material into solid particulate form, and recycling the solid particulate second material into contact with hot liquid first material.

6. The process of claim 5 in which the first material is hot water.

9. The process of effecting heat exchange and cooling which comprises directly contacting a hot liquid first material, said material being liquid at ambient temperature, with a second material, which is solid at ambient temperature and essentially insoluble in the first material, in solid particulate form to liquefy the second material, said liquid second material having a specific gravity less than the hot liquid first material, separating the liquid second material from the first liquid material by gravity into two layers, circulating the liquid first material through a power generation plant as an intermediate coolant, dispersing and cooling the second material liquid layer in air into solid particulates, and recycling the solid particulates of the second material into contact with the hot first liquid material recycled from the power generation plant.

10. The process of claim 9 in which the first material is water and the second material melts at 10*F. above the ambient air temperature.

11. The prOcess of effecting heat exchange and cooling which comprises spraying hot water obtained as an intermediate coolant from a power generation plant into intimate contact with a second material, which is solid at ambient temperature and essentially insoluble in hot water in solid particulate form to liquefy the second material, separating the liquid second material from the water by settling the liquids into two layers in a reservoir chamber, cooling and converting the separated liquid second material into solid particulate form, and recycling the solid particulate second material into contact with hot water.

16. The process of effecting heat exchange and cooling which comprises: forming a dispersion comprising a first liquid material and a second solid particulate material dispersed in the first liquid material, said first material being liquid at ambient temperature and said second material being solid at ambient temperature and insoluble in liquid form in the first material, feeding the dispersion in indirect heat exchange through a heat source adequate to melt the second material to thereby form a liquid-liquid mixture, separating the liquid-liquid mixture into liquid first material and liquid second material, cooling and converting the liquid second material into solid particulate form, recycling the solid particulate second material into contact with the separated liquid first material to reform the dispersion, and repeating the described process.

17. The process of claim 14 in which the first material is hot water.

21. The process of claim 17 in which the second material melts at 10*F. above the ambient air temperature.

24. The process of effecting heat exchange and cooling which comprises: feeding a dispersion comprising a first liquid material and a second solid particulate material dispersed in the first liquid material, said first material being liquid at ambient temperature and said second material being solid at ambient temperature, insoluble in and of a different specific gravity in liquid form than the first material, in indirect heat exchange through a heat source adequate to melt the second material to thereby form a liquid-liquid mixture, spraying the liquid-liquid mixture into a reservoir of the first material having a temperature low enough to solidify the second material in particulaTe form dispersed in the reservoir of first material, and removing particulate second material with liquid first material from the reservoir and refeeding it in indirect heat exchange through the heat source.

25. The process of claim 24 in which the second material has a specific gravity less than the first material.

26. The process of claim 25 in which the first material is water.

29. A process of cooling a hot first material comprising: bringing the hot first material into heat exchange relationship with a particulate solid second material which liquefies through such heat exchange, removing the liquefied second material from heat exchange with the first material, cooling and converting the removed liquefied second material into solid particulates, and recontacting the solid particulate second material in heat exchange with the hot first material.