WO1992002770A1

WO1992002770A1 - Vacuum insulated sorbent-driven refrigeration device

Info

Publication number: WO1992002770A1
Application number: PCT/US1991/005321
Authority: WO
Inventors: Gary V. Steidl; Cullen N. Sabin; Dennis A. Thomas
Original assignee: International Thermal Packaging, Inc.
Priority date: 1990-08-01
Filing date: 1991-07-26
Publication date: 1992-02-20
Also published as: AU8712591A

Abstract

Disclosed is a self-contained, rapid cooling device (10) that retains heat produced from the cooling process and can be stored for indefinite periods without losing its colling potential. Also disclosed is a method for using the device. The device consists of two chambers (12, 18) with the second chamber (18) substantially surrounding the first (12). A liquid is suspended by a wettable material (24) adjacent to the interior surface of the second chamber. This liquid undergoes a phase change into a vapor which cools the outer surface (26) of the device. The vapor is allowed to flow out of the second chamber (18) and into the first chamber (12), which contains a sorbent (14) for the vapor. The device is self-contained, because a material (16) in contact with the sorbent removes the heat from the sorbent to prevent a reduction in the cooling effect produced by the vaporizing liquid. In addition, a vaccum is created within the second chamber (18) which insulates the first chamber (12) and keeps the heated sorbent (14) from diminishing that cooling effect.

Description

VACUUM INSULATED SORBENT-DRIVEN REFRIGERATION DEVICE

Background of the Invention There are many foods and beverages that may be stored almost indefinitely at average ambient temperature of 20^o-25^oC but that should be cooled immediately before consumption. In general, the cooling of these foods and beverages is accomplished by electrically-run refrigeration units. The use of these units to cool such foods and beverages is not always practical because refrigerators generally require a source of electricity, they are not usually portable, and they do not cool the food or beverage quickly. An alternate method for providing a cooled material on demand is to use portable insulated containers. However, these containers function merely to maintain the previous temperature of the food or beverage placed inside them, or they require the use of ice cubes to provide the desired cooling effect. When used in conjunction with ice, insulated containers are much more bulky and heavy than the food or beverage. Moreover, in many locations, ice may not be readily available when the cooling action is required.

Ice cubes have also been used independently to cool food or beverages rapidly. However, use of ice independently for cooling is often undesirable because ice may be stored only for limited periods above 0"C. Moreover, ice may not be available when the cooling action is desired. In addition to food and beverage cooling, there are a number of other applications for which a portable cooling device is extremely desirable. These include medical applications, including cooling of tissues or organs; preparation of cold compresses and cryogenic destruction of tissues as part of surgical procedures; industrial applications, including production of cold water or other liquids upon demand; preservation of biological specimens; cooling of protective clothing; and cosmetic applications A portable cooling apparatus could have widespread utilit in all these areas.

Most attempts to build a self-contained miniaturize cooling device have depended on the use of a refrigeran liquid stored at a pressure above atmospheric pressure, s that the refrigerant vapor could be released directly t the atmosphere. Unfortunately, many available refrigeran liquids for such a system are either flammable, toxic, harmful to the environment, or exist in liquid form at suc high pressures that they represent an explosion hazard i quantities suitable for the intended purpose. Conversely, other available refrigerant liquids acceptable fo discharge into the atmosphere (such as carbon dioxide) have relatively low heat capacities and latent heats of vaporization. As a result, some cooling devices which release carbon dioxide are more bulky than is commercially acceptable for a portable device.

An alternate procedure for providing a cooling effect in a portable device is to absorb or adsorb the refrigerant vapor in a chamber separate from the chamber in which the evaporation takes place. In such a system, the refrigerant liquid boils under reduced pressure in a sealed chamber and absorbs heat from its surroundings. The vapor generated from the boiling liquid is continuously removed from the first chamber and discharged into a second chamber containing a desiccant or sorbent that absorbs the vapor.

The use of two chambers to produce a cooling effect around one chamber is illustrated in U.S. Patent Nos. 4,250,720 and 4,736,599 to Siegel and Great Britain Patent No. 2,095,386 to Cleghorn, et al. These patents disclose a two-chamber apparatus connected by a tube. The Siegel patent uses water as the refrigerant liquid, while the Cleghorn, et al. patent is not limited to water. The Siegel patent envisions the use of such a cooling device to cool food or beverages. However, both systems produce heat in the absorption chamber, and the chamber must be distanced from the area cooled by the first chamber so that the cooling effect is not compromised.

None of the prior art effectively deals with the problem of heat buildup in the sorbent chamber and possible transfer back to the material being cooled; thus, none of the prior sorption-cooling devices are fully suitable for use in miniaturized food, beverage and other cooling systems.

Accordingly, one objective of the present invention is to provide a self-contained sorption cooling device with a means for isolating the heat produced in the sorbent so that heat transfer back to the material being cooled is minimized. Another objective is to provide a cooling device with a valve that will open in response to a pressure change.

Other objectives will become apparent from the appended drawing and the following Detailed Description of the Invention.

Summary of the Invention The present invention is a self-contained cooling apparatus comprising a first evacuated chamber containing a sorbent. and a second chamber which substantially surrounds the first chamber. The second chamber contains a vaporizable liquid that is supported adjacent to the outer wall of the chamber by a wettable material. A valve is placed between the chambers to prevent gaseous communication between them until desirable. An actuator opens the valve, thereby connecting the first and second chambers and permitting the liquid to vaporize and diffuse into the first chamber, where it is received by the sorbent.

Actuating the valve causes a drop in pressure in the second chamber because the initial vacuum in the first chamber draws the majority of the gas pressure out of the second chamber. This drop in pressure over the liquid in the second chamber causes it to boil and vaporize, thereby absorbing heat. An amount of heat equal to the latent heat of vaporization of the liquid must be absorbed by th liquid for vaporization to occur. Since the liquid i supported adjacent to the outer wall of the second chambe by the wettable material, most of this heat is draw through this wall, from the exterior of the device, causin the cooling effect. The vapor then diffuses out of th second chamber and into the first chamber, where it i absorbed or adsorbed by the sorbent. The sorbent the gains the heat contained in the absorbed or adsorbed vapor, and, if the absorption-adsorption process involves a exothermic chemical reaction, the sorbent must also absorb the reaction heat.

The heat contained within the sorbent may optionally be removed from the sorbent by a heat removing material. Preferably, that heat removing material is a phase change material which is thermally coupled to the sorbent. It has a thermal mass different from the material comprising the first chamber in contact with the sorbent and has a heat capacity greater than that of the sorbent. Heat is isolated within the first chamber by a vacuum which insulates and largely surrounds the first chamber. A vacuum .in the first chamber draws the majority of the gas and vapor out of the second chamber and into the first chamber, thereby creating a partial vacuum within the second chamber. Since the second chamber substantially surrounds the first chamber, the vacuum in the second chamber functions as a thermal insulator of the first chamber. Although the vacuum in the second chamber is not total, it need not be. Any significant vacuum will greatly reduce the amount of heat conduction because there are simply fewer gas molecules available to transfer the heat. Indeed, a perfect vacuum is unobtainable in any application due to technological difficulties in removing all molecules of gas from a given space and because some water vapor molecules are always present.

During the operation of the device, the flow of the vapor from the second chamber into the first chamber also functions to sweep heat escaping from the first chamber back into the first chamber, along with the vapor. This feature aids the device in retaining accumulated heat within its first chamber and away from the unvaporized liquid in the second chamber. In a preferred embodiment, the exterior wall of the first chamber is polished or metallized to produce a reflective finish, which reduces heat escape by radiation. In another preferred embodiment, the exterior of the first chamber is coated with a thin thermal insulator which further reduces the escape of heat from the first chamber. The exterior surface of this insulator may also be polished or metallized.

In one preferred embodiment, the first chamber is supported within the second chamber at points by thermally insulating materials, and in another, the exterior of the device is fluted. In still another preferred embodiment, the liquid is water and in one, the wettable material supporting the liquid is a highly hydrophilic polymer. The liquid may be mixed with a nucleating agent that promotes ebullition of the liquid.

The present invention provides a self-contained rapid cooling, device that cools a food, beverage or other material article from ambient temperature on demand in a timely manner, exhibits a useful change in temperature, retains the heat produced from the cooling process or retards the transfer of the heat from the sorbent back to the material being cooled, can be stored for unlimited periods without losing its cooling potential, and is able to meet government standards for safety in human use. Description of the Drawings

Figure 1 is a perspective view of a fluted cooling device according to the present invention, wherein the first chamber is wholly contained within the second chamber. Figure 2 is a horizontal cross-section of the device taken along the line 2-2 in Figure 1.

Figure 3 is a vertical cross-section of the same device taken along the line 3-3 in Figure 1.

Figure 4 is a close up vertical cross-section of the valve of the same device, again taken along the line 3-3, but with the valve in the open position. Figure 5 is a partial vertical cross-section of the device, incorporating an optional insulative coating about the first chamber.

Figure 6 is a partial vertical cross-section of the device wherein a different valve design has been used Figure 7 is the same view as Figure 6, but with the valve in an open position.

Figure 8 is the same view as Figure 6 , wherein a mechanical valve retainer has been incorporated.

Figure 9 is the same view of the device as Figure 8, but with the valve retainer disengaged and the valve in an open position.

Detailed Description of the Preferred Embodiment As is shown in the figures, the cooling device 10 has a first chamber 12 that is at least partially filled with a sorbent 14, which is optionally in contact with a heat- removing material 16. This first chamber 12 is initially evacuated, but the vacuum need not be total. The initial pressure in the first chamber is preferably significantly lower than normal atmospheric pressure. The cooling device also includes a second chamber 18 which surrounds the first chamber 12 and insulates it when evacuated. The second chamber can be evacuated either during operation of the device, by connecting it to the first evacuated chamber via the valve 20, or it can be initially evacuated. Again, the vacuum need not be total. The interior surface of the outer wall of the second chamber 18 (cooling wall 26) is wetted with a refrigerant liquid 22 and is preferably lined with a wettable material 24 which supports the refrigerant liquid 22. The wettable material 24 holds the refrigerant liquid against the cooling wall 26 prior to and during operation of the device 10 and increases the surface area of the liquid 22. During operation of the device, the liquid vaporizes and absorbs heat from the cooling wall 26. Positioned between the first chamber 12 and the second chamber 18 is a valve 20, which allows gaseous communication between the chambers 12 and 18 only when the valve 20 is open.

The operation of the cooling device 10 is suspended (i.e., the system is static and no cooling occurs) until the valve 20 is opened, at which time gaseous communication between the first chamber 12 and second chamber 18 occurs. Opening the valve 20 between the first and second chambers 12 and 18 causes a drop in pressure in the second chamber 18 because the first chamber 12 is initially evacuated. The drop in pressure in the second chamber 18 upon opening of the valve 20 results in a vacuum forming within the second chamber 18 which causes the liquid 22 to boil at ambient temperature to form a vapor. This liquid-to-gas phase change can occur only if the liquid 22 removes heat equal to the latent heat of vaporization of the evaporated liquid 22 from its surroundings. Most of this heat is absorbed from the fluted cooling wall 26 of the device 10 because the liquid 22 is held adjacent to it by the wettable material 24. The cooled fluted wall 26, in turn, removes heat from its surroundings as indicated by the arrows 28. Little heat is absorbed from the interior of the second chamber 18 due to the substantial vacuum within it after the valve 20 is opened.

As the vaporized liquid diffuses into the first chamber 12, the vapor is absorbed or adsorbed by the sorbent 14. This facilitates the maintenance of a reduced vapor pressure in the second chamber 18 and allows more of the liquid 22 to boil and become vapor, further reducing the temperature of the fluted wall 26. The continuous removal of the vapor maintains the pressure in the second chamber 18 below the vapor pressure of the liquid 22, so that the liquid 22 boils and produces vapor continuously until the sorbent 14 is saturated, until the liquid 22 has boiled away, or until the temperature of the liquid 22 has dropped below its boiling point.

When the sorbent 14 absorbs or adsorbs the vapor, a heat of sorption is generated. The optional heat-removing material 16, which is thermally coupled to the sorbent 14 (and preferably is mixed with the sorbent 14) removes heat from the sorbent 14, preventing or slowing a rise in temperature in the sorbent 14. This reduction of temperature in the sorbent 14 slows the absorption and conduction of heat by the interior wall 30 and thereby reduces the amount of interior heat escaping from the first chamber 12, which absorption might compromise the cooling capacity of the device by reducing the amount of exterior heat absorbed by the device.

The spatial relationship of the chambers and the wettable material function to maximize the exterior cooling effect of the device. The channeling of the vapor flow from the second chamber 18 around and then into the first chamber 12 functions to sweep any heat escaping from the first chamber 12 back into the first chamber 12, along with the vapor. The positioning of the second chamber 18 so that it substantially surrounds the first chamber 12, combined with the substantial vacuum within the second chamber during operation of the device, form an insulating barrier around the first chamber 12. Also, the wettable material 24 is located on the inside surface of the exterior fluted wall 26, as far away from the first chamber as possible. The wettable material 24 is thus separated from the warm first chamber 12 by the vacuum within the second chamber 18. This spacing slows the escape of heat from the first chamber 12, thereby forcing the liquid 22 within the wettable material 20 to absorb the majority of its heat of vaporization from the exterior of the device.

The vacuum maintained in the second chamber 18 during operation of the device 10, and its insulative effect, can be enhanced by designing the first chamber 12 with a larger open volume than the second chamber 18. With this design, when the initially evacuated first chamber 12 is connected to the second chamber 18 by the valve 20, a substantial vacuum will still remain in both chambers. This occurs because most of the gas pressure from the second chamber 18 will escape to the first chamber 12, where it will not significantly increase the gas pressure due to its larger volume. Another preferred means of increasing the vacuum in the second chamber 18 is to evacuate it during construction of the device, as is done with the first chamber 12. In a preferred embodiment, the exterior surface of the interior wall 30 is polished or metallized to achieve a high gloss finish. This finish slows the escape of heat from the interior wall 30 by radiation. In another preferred embodiment, the first chamber 12 is also coated with a thin thermal insulator 32 (fig. 5) which helps retain heat within the first chamber 12. The insulator 32 can be comprised of plastic, glass, ceramic or another material known by those skilled in the art to be a poor conductor of heat. The exterior surface of the insulation coating can also be metallized or polished to a high gloss to reduce heat loss by radiation. In another preferred embodiment, insulating supports 34 are placed between the first chamber 12 and the second chamber 18 at points where they must be -in contact for structural support. These supports thermally separate the two chambers 12 and 18 to further increase the efficiency of the device. In still another preferred embodiment, the outer surface of the device is fluted. Fluting the device serves two important functions. First, it increases the ability to absorb heat by increasing the surface area of the cooling wall 26. Second, since fluting has a superior ability to withstand exterior pressure, it strengthens the wall so it can support the vacuum within the device.

It is also preferred that there is enough sorbent 14 within the first chamber 12 so that substantially all of the liquid 22 is absorbed or adsorbed in the sorbent 14. By having an excess of sorbent 14, the device ensures that a vacuum will remain in the second chamber 18 at the most critical time to ensure insulation about the first chamber 12 after the sorption process is complete. Moreover, it is preferable that, while there is not an absolute vacuum in the second chamber 18, it is at a pressure substantially lower than atmospheric during and after evaporation so that a substantial vacuum exists to insulate the first chamber 12.

The chambers themselves may be constructed of any of a number of different materials including both metals (i.e. aluminum, tin, steel) and plastics (i.e. injection molded plastic, vacuum molded plastic) . In applications requiring the greatest efficiency, a material exhibiting poor thermal conductivity should be chosen for the first chamber 12 and a highly conductive material is preferred for the second chamber 18. This will result in maximum thermal absorption and retention. In applications where a low manufacturing cost is of great importance, inexpensive materials such as plastics may be substituted for more efficient materials. The particular application will dictate what materials are preferred. For use in beverage cans, a drawn, fluted aluminum device is preferred in such an embodiment, the first and second chambers 12, 18 are each formed of drawn aluminum, preferably with an integral bottom and sides and a crimp-sealed top formed as a separate piece.

Two important components of the present invention are the evaporating liquid and the sorbent. The liquid and the sorbent must be complimentary (i.e., the sorbent must be capable of absorbing or adsorbing the vapor produced by the liquid) , and suitable choices for these components would be any combination able to make a useful change in temperature in a short time, meet government standards for safety and be compact.

The refrigerant liquids used in the present invention preferably have a high vapor pressure at ambient temperature, so that a reduction of pressure will produce a high vapor production rate. The vapor pressure of the liquid at 20*C is preferably at least about 9 mm Hg, and more preferably is at least about 15 or 20 mm Hg. Moreover, for some applications (such as cooling of food products) , the liquid should conform to applicable government standards in case any discharge into the surroundings, accidental or otherwise, occurs. Liquids with suitable characteristics for various uses of the invention include: various alcohols, such as methyl alcohol and ethyl alcohol; ketones or aldehydes, such as acetone and acetaldehyde; water; and freons, such as freon C318, 114, 21, 11, 114B2, 113 and 112. The preferred liquid is water.

In addition, the refrigerant liquid may be mixed with an effective quantity of a miscible nucleating agent having a greater vapor pressure than the liquid to promote ebullition so that the liquid evaporates even more quickly and smoothly, and so that supercooling of the liquid does not occur. Suitable nucleating agents include ethyl alcohol, acetone, methyl alcohol, propyl alcohol and isobutyl alcohol, all of which are miscible with water. For example, a combination of a nucleating agent with a compatible liquid might be a combination of 5% ethyl alcohol in water or .5% acetone in methyl alcohol. The nucleating agent preferably has a vapor pressure at 25^βC of at least about 25 mm Hg and, more preferably, at least about 35 mm Hg. Alternatively, solid nucleating agents may be used, such as the conventional boiling stones used in chemical laboratory applications.

The sorbent material used in the first chamber 12 is preferably capable of absorbing and adsorbing all the vapor produced by the liquid, and also preferably will meet government safety standards for use in an environment where contact with food may occur. Suitable sorbents for various applications may include barium oxide, magnesium perchlorate, calcium sulfate, calcium oxide, activated carbon, calcium chloride, glycerine, silica gel, alumina gel, calcium hydride, phosphoric anhydride, phosphoric acid, potassium hydroxide, sulfuric acid, lithium chloride, ethylene glycol and sodium sulfate.

The heat-removing material may be one of three types: (1) a material that undergoes a change of phase when heat is applied; (2) a material that has a heat capacity greater than the sorbent; or (3) a material that undergoes an endothermic reaction when brought in contact with the liquid refrigerant.

Suitable phase change materials for particular applications may be selected from paraffin, naphthalene, sulphur, hydrated calcium chloride, bromocamphor, cetyl alcohol, cyanamide, eleudic acid, lauric acid, hydrated sodium silicate, sodium thiosulfate pentahydrate, disodiu phosphate, hydrated sodium carbonate, hydrated calcium nitrate, Glauber's salt, potassium, sodium and magnesium acetate. The phase change materials remove some of the heat from the sorbent material simply through storage of sensible heat. In other words, they heat up as the sorbent heats up, removing heat from the sorbent. However, the most effective function of the phase change material is in the phase change itself. An extremely large quantity of heat can be absorbed by a suitable phase change material in connection with the phase change (i.e., change from a solid phase to a liquid phase, or change from a liquid phase to a vapor phase) . There is typically no change in the temperature of the phase change material during the phase change, despite the relatively substantial amount of heat required to effect the change, which heat is absorbed during the change. Phase change materials which change from a solid to a liquid, absorbing from the sorbent their latent heat of fusion, are the most practical in a closed system. However, a phase change material changing from a liquid to a vapor is also feasible. Thus, an environmentally-safe liquid could be provided in a separate container (not shown) in contact with the sorbent material (to absorb heat therefrom) but vented in such a way that the boiling phase change material carries heat away from the sorbent material and entirely out of the system.

Another requirement of any of the phase change materials is that they change phase at a temperature greater than the expected ambient temperature of the material to be cooled, but less than the temperature achieved by the sorbent material upon absorption of a substantial fraction (i.e., one-third or one-quarter) of the refrigerant liquid. Thus, for example, in most devices according to the present invention which are intended for use in cooling a material such as a food or beverage, the phase change material could change phase at a temperature above about 30"C, preferably above about 35°C but preferably below about 70*C, and most preferably below about 60°C. Of course, in some applications, substantially higher or lower phase change temperatures may be desirable. Indeed, many phase change materials with phase change temperatures as high as 90^βC, 100^βc or llθ°c may be appropriate in certain systems.

Materials that have a heat capacity greater than that of the sorbent simply provide a thermal mass in contact with the sorbent that does not effect the total amount of heat in the system, but reduces the temperature differential between the material being cooled and the first chamber 12, with two results. First, the higher the temperature gradient between two adjacent materials, the more rapid the rate of heat exchange between those two materials, all else being equal. Thus, such thermal mass materials in the first chamber 12 slow the transfer of heat out of the first chamber 12. Second, many sorbent materials function poorly or do not function at all when the temperature of those materials exceeds a certain limit. Heat-absorbing material in the form of a thermal mass can substantially reduce the rate of the sorbent's temperature increase during the cooling cycle. This, in turn, maintains the sorbent at a lower temperature and facilitates the vapor-sorption capabilities of the sorbent. Various materials which have a high specific heat include cyanamide, ethyl alcohol, ethyl ether, glycerol, isoamyl alcohol, isobutyl alcohol, lithium hydride, methyl alcohol, sodium acetate, water, ethylene glycol and paraffin wax.

Care must be taken, of course, when selecting a high specific heat material (or high thermal mass material) to ensure that it does not interfere with the functioning of the sorbent. If the heat-absorbing material, for example, is a liquid, it may be necessary to package that liquid or otherwise prevent physical contact between the heat- absorbing material and the sorbent. Small individual containers of heat-absorbing material scattered throughout the sorbent may be utilized when the sorbent and the heat- absorbing material cannot contact one another. Alternatively, the heat-absorbing material may be placed in a single package having a relatively high surface area in contact with the sorbent to facilitate heat transfer from the sorbent into the heat-absorbing material.

The third category of heat-removing material (material that undergoes an endothermic reaction) has the advantage of completely removing heat from the system and storing it in the form of a chemical change. The endothermic material may advantageously be a material that undergoes an endothermic reaction when it comes in contact with the refrigerant liquid (or vapor) . In this embodiment of the invention, when the valve 20 is opened and vapor is permitted to flow from the second chamber 18 into the first chamber 12, the vapor comes in contact with some of the endothermic material, which then undergoes an endothermic reaction, removing heat from the sorbent 14. Such endothermic materials have the advantage that the heat is more or less permanently removed from the sorbent, and little, if any, of that heat can be retransferred to the material being cooled. This is in contrast to phase change materials and materials having a heat capacity greater than the sorbent material, both of which may eventually give up their stored heat to the surrounding materials, although such heat exchange (because of design factors that retard heat transfer, such as poor thermal conductivity of the sorbent 14) generally does not occur with sufficient rapidity to reheat the cooled material prior to use of that material. Heat-absorbing materials which undergo an endothermic reaction may variously be selected from such compounds as H₂B0₃, PbBr₂, KBr0₃, KC10₃, K₂Cr₂0₇, KC10₄, K₂S, Snl₂, NH4CI, KMnθ4 and CSCIO4. Furthermore, the heat-removing material may be advantageously in contact with the sorbent. In various embodiments of the invention, the sorbent and heat-removing material could be blended, the heat-removing material could be in discrete pieces mixed with the sorbent, or the material could be a mass in contact with, but not mixed into, the sorbent. In selecting the wettable material 24, any of a number of materials may be chosen, depending upon the requirements of the system and the particular refrigerant liquid 22 being used. The wettable material may be something as simple as cloth or fabric having an affinity for the refrigerant liquid 22 and a substantial wetting ability. Thus, for example, when the refrigerant liquid is water, the wettable material may be cloth, sheets, felt or flocking material which may be comprised of cotton, filter material, natural cellulose, regenerated cellulose, cellulose derivatives, blotting paper or any other suitable material.

The most preferred wettable material would be highly hydrophilic, such as gel-forming polymers which would be capable of coating the interior surface of the evaporation chamber. Such materials preferably consist of alkyl, aryl and amino derivative polymers of vinylchloride acetate, vinylidene chloride, tetrafluoroethylene, methyl methacrylate, hexanedoic acid, dihydro-2,5-furandione, propanoic acid, 1,3-isobenzofurandione, 1 h-pyrrole-2,5- dione or hexahydro-2 h-azepin-2-one.

The wettable material may be sprayed, flocked, or otherwise coated or applied onto the interior surface of the second chamber 18. In a preferred embodiment, the wettable material is electrostatically deposited onto that surface. In another embodiment, the wettable material is mixed with a suitable solvent, such as a non-aqueous solvent, and then the solution is applied to the interior surface of the second chamber 18.

In another preferred embodiment, the wettable material is able to control any violent boiling of the evaporator and thus reduces any liquid entrainment in the vapor phase. In such an embodiment, the wettable material is a polymer forming a porous space-filling or sponge-like structure.

The valve 20 may be selected from any of the various types shown in the prior art, or may be of novel construction. The valve 20 is located between the first chamber 12 and the second chamber 18 so that it .prevents vapor from being received by the sorbent 14 until desirable. However, if the entire cooling device 10 is within a pressurized container, a pressure responsive valve can be used which can actuate the cooling device upon the release of the pressure within the container.

In a preferred embodiment, as illustrated in Figure 4, the valye consists of a valve seat 36 at the opening of the first chamber 12 and a diaphragm 38 located above the valve seat 36. The diaphragm 38 is adapted to flex downward against the valve seat 36 when the pressure exterior to the device is above normal atmospheric pressure, thereby closing the valve 20 and sealing the first chamber 12. When the pressure exterior to the device is then reduced to normal atmospheric, the diaphragm 38 moves upward, pulling away from the valve seat 36 and unsealing the first chamber 12. This configuration makes it possible for the device to remain inactive while under high pressure, such as when place in a pressurized beverage can, and in operation when the pressure is reduced, such as when the soda can is opened.

The diaphragm 38 may be affixed to the second chamber 18 or may be an integral part of it. In one embodiment, the lid of the second chamber serves as the diaphragm 38. The diaphragm 38 is made of a flexion resistant material, such as spring steel, and is preferably coated with a resilient sealing agent proximate to the valve seat to enhance the seal.

In another preferred embodiment, as illustrated in Figures 6-9, a seal 40 is affixed to the interior surface of the diaphragm 38 proximate to the valve seat. The seal 40 is adapted to seal the first chamber 12 when the diaphragm 38 is in its flexed position, instead of the diaphragm 38 sealing the first chamber 12 itself. This configuration allows for a greater variety of valve seat designs because the seal 40 is not as limited in its shape as the diaphragm and may be constructed of any number of materials which can be bonded to the diaphragm and can effectively seal the first chamber. Suitable materials include rubber, synthetic rubber, metal, silicone, polytetrafluoroethylene, polyurethane, elastomers, and other polymers. The seal 40 may also be made of a hard substance such as metal, but preferably the hard substance is coated with a resilient sealing agent proximate to the valve seat, to enhance the seal. Such a sealing agent may also be desirable when using other materials.

In the preferred embodiment, as shown in Figures 3, 4, 8 and 9, a mechanical means is incorporated into the device for holding the valve in a closed position until the device is placed in an environment where the pressure is above normal atmospheric, at which time the means is deactivated and the valve is held closed by the above normal pressure alone. In one embodiment (shown in Figures 3 and 4), this is accomplished by affixing a cocking post 42 and cocking yoke 44 to the device at a point where it exerts pressure on the diaphragm 38, causing it to flex and seal the first chamber 12. Preferably the cocking post 42 is held in a cocked position by a soluble substance 46 (as shown in Figure 3) , which will dissolve and release the cocking post 42 from t_he yoke 44 when the device is placed in contact with an appropriate solvent. This configuration holds the valve in a closed position until it can be placed in a pressurized container with a solvent in it, such as a beverage can. The solvent (e.g. , the liquid beverage) then dissolves the soluble substance and releases the valve retainer, leaving only the pressure to hold the valve closed and the device inoperative. When the pressure is released, such as when a soda can is opened, the valve can open and the device commences operation.

In another preferred embodiment, the cocking yoke 44 and post 42 are not used, and instead, a valve retainer 48 is attached to the device 10 at a point where it exerts pressure on the diaphragm 40, causing it to flex and seal the first chamber 12. Preferably the valve retainer 48 is attached to the device 10 at one or more points by a soluble substance, which will dissolve when the device is placed in contact with an appropriate solvent, returning the device to pressure activation. In another preferred embodiment, a pressure sensitive valve is not incorporated and only a valve retainer or cocking yoke and post assembly are used, which again are held in place by a soluble substance. In this configuration, the device is simply placed in the liquid to be cooled under conditions of normal pressure, the soluble substance dissolves, and the device commences operation. In either of the preferred embodiments, the soluble substance will preferably dissolve in an aqueous liquid and is preferably comprised of a sugar compound or a water soluble salt or polymer.

The invention also includes a method of using the cooling device described herein. This method includes the step of providing a cooling device of the type set forth herein in its various embodiments; opening the valve between the first chamber 12 and the second chamber 18, whereby the pressure in the second chamber is reduced, causing the liquid to boil, forming a vapor, which vapor is collected by the sorbent material; removing vapor from the second chamber by collecting the same in the sorbent until an equilibrium condition is reached wherein the sorbent is substantially saturated or substantially all of the liquid originally in the first chamber has been collected in the sorbent; and simultaneously removing heat from the sorbent by means of the heat-removing material described above. The process is preferably a one-shot process; thus, opening of the valve 20 connecting the first chamber 12 and the second chamber 18 is preferably irreversible. At the same time, the system is a closed system; in other words, the refrigerant liquid does not escape the system, and there is no means whereby the refrigerant liquid or the sorbent may escape the device 10. Although the invention has been described in the context of certain preferred embodiments, it is intended that the scope of the invention not be limited to the specific embodiment set forth herein, but instead be measured by the claims that follow.

Claims

WHAT IS CLAIMED IS:

1. A self-contained cooling device comprising: a first evacuated chamber containing a sorbent; a second chamber, substantially surrounding the first chamber, which is adapted to insulate the first chamber when substantially evacuated; a liquid which, in operation of the device, evaporates to form a vapor; a wettable material adjacent to the interior wall of the second chamber, which is adapted to hold the liquid adjacent to the outer walls of the device prior to and during operation of the device; a valve for preventing gaseous communication between the first and second chamber until desirable; and a means for actuating the valve, thereby commencing operation of the device.

2. The apparatus of Claim 1, wherein the valve is activated by a change in pressure exterior to the device.

3. The apparatus of Claim 1, wherein the valve is held closed by a soluble substance, until the material to be cooled dissolves the substance.

4. The apparatus of Claim 3, wherein the soluble substance is a sugar compound or water soluble salt or polymer.

5. The apparatus of Claim 1, wherein the valve consists of a valve seat on one chamber and a diaphragm associated with the other chamber, wherein the diaphragm is adapted to flex toward the valve seat when exposed to an exterior pressure above normal atmospheric, thereby sealing the first chamber, and unflex under normal atmospheric pressure, thereby unsealing the first chamber.

6. The apparatus of Claim 5, wherein the diaphragm is made from deflection resistant material.

7. The apparatus of Claim 5, wherein the diaphragm is made of spring steel.

8. The apparatus of Claim 5, wherein the diaphragm is coated with a resilient sealing agent proximate to the valve seat.

9. The apparatus of Claim 5, wherein a cap is affixed to the interior surface of the diaphragm and is adapted to seal the first chamber at the valve seat when the diaphragm is flexed and unseal the first chamber when the diaphragm is unflexed.

10. The apparatus of Claim 9, wherein the cap is made of rubber, synthetic rubber, plastic, metal, silicone, polytetrafluoroethylene, polyurethane, elastomers, and other polymers capable of forming a seal against the valve seat.

11. The apparatus of Claim 9, wherein the cap is coated with a resilient sealing agent proximate to the valve seat.

12. The apparatus of Claim 5, further comprising mechanical means for holding the valve in a closed position until the device is placed in an environment of above atmospheric pressure, at which time the holding means is released and the valve is held closed by the above normal atmospheric pressure alone.

13- The apparatus of Claim 5, wherein a soluble substance is used to attach a solid restraint to the device in such a manner that it holds the diaphragm in a flexed position, which forces the valve to remain closed and the first chamber sealed until the soluble substance is dissolved by a suitable solvent, thereby releasing the solid restraint and allowing to valve to return to normal pressure activation.

14. The apparatus of Claim 13, wherein the soluble substance can be dissolved by an aqueous liquid.

15. The apparatus of Claim 13, wherein the soluble substance is a sugar compound or water soluble salt or polymer.

16. The apparatus of Claim 1, wherein the wettable material consists of a hydrophilic gel-forming polymer.

17. The apparatus of Claim 1, wherein the wettable material consists of alkyl, aryl and amino derivative polymers selected from the group comprising vinylchloride acetate, vinylidene chloride, tetrafluoroethylene, methyl methacrylate , hexanedoic acid, dihydro-2,5- furandione,propanoic acid, 1,3-isobenzofurandione, 1 h- pyrrole-2,5-dione and hexahydro-2 h-azepin-2-one.

18. The apparatus of Claim 1, wherein the liquid is water.

19. The apparatus of Claim 1 , wherein the second chamber is initially evacuated.

20. The apparatus of Claim 1, wherein the first chamber contains sufficient sorbent to absorb or adsorb substantially all of the liquid in the second chamber.

21. The apparatus of Claim 1, further comprising a method thermally coupled to the sorbent for removing heat from the sorbent.

22. The Apparatus of Claim 1, wherein the first chamber is supported within the second chamber by thermally insulating materials.

23. The apparatus of Claim 1, wherein the outer surface-of the device is fluted.

24. The apparatus of Claim 1, wherein the first chamber is coated with a thermally insulating material.

25. The apparatus of Claim 24, wherein the surface of the insulating material is polished or metallized for a reflective finish.

26. A method for cooling, comprising the steps of: (a) providing a cooling device comprising: i) a first evacuated chamber containing a sorben ; ii) a second chamber, substantially surrounding the first chamber, which is adapted to insulate the first chamber when substantially evacuated; iϋ) a liquid which, in operation of the device, evaporates to form a vapor; iv) a wettable material, predominately affixed to the interior wall of the second chamber, which is adapted to hold the liquid near the cooling wall of the device and away from the wall of the first chamber; v) a valve for preventing gaseous communication between the first and second chamber until desirable; and vi) a means for actuating the valve, thereby commencing operation of the device; (b) opening the valve to permit communication between the first chamber and second chamber, whereby the pressure in the second chamber is reduced, causing the liquid to boil, forming a vapor, which vapor is collected by the sorbent material in the first chamber;

(c) removing vapor from the first chamber by collecting it in the sorbent until an equilibrium is reached, wherein the sorbent is substantially saturated or substantially all of the liquid originally in the second chamber has been collected in the sorbent; and

(d) containing heat generated in the sorbent within the first chamber by means of a vacuum in the second chamber, which substantially surrounds the first chamber.

27. The method of Claim 26, wherein the valve is actuated by a drop in pressure exterior to the device.

28. The method of Claim 26, wherein the valve is held closed by a soluble substance, until the material to be cooled dissolves the substance.

29. The method of Claim 26, wherein said method comprises a one-shot process.

30. A pressure activated valve comprising: a sealed chamber; a valve seat within the chamber; a diaphragm associated with the chamber, wherein the diaphragm is adapted to flex toward the valve seat when the chamber is exposed to an exterior pressure above normal atmospheric, thereby sealing the first chamber, and unflex when the chamber is exposed to normal atmospheric pressure, thereby unsealing the first chamber; and a means for holding the valve in a closed position until the device is placed in an environment of above normal atmospheric pressure, at which time the holding means is released and the valve is held closed by the above normal atmospheric pressure alone.

31. The valve of Claim 30, wherein the diaphragm is made from deflection resistant material.

32. The apparatus of Claim 30, wherein the diaphragm is made of spring steel.

33. The apparatus of Claim 30, wherein the diaphragm is coated with a resilient sealing agent proximate to the valve seat.

34. The apparatus of Claim 30, wherein a cap is affixed to the interior surface of the diaphragm and is adapted to seal the first chamber at the valve seat when the diaphragm is flexed and unseal the first chamber when the diaphragm is unflexed.

35. The apparatus of Claim 34, wherein the cap is made of rubber^', synthetic rubber, plastic, metal, silicone, polytetrafluoroethylene, polyurethane, elastomers, and other polymers capable of forming a seal against the valve seat.

36. The apparatus of Claim 34, wherein the cap is coated with a resilient sealing agent proximate to the valve seat.

37. The valve of Claim 30, wherein the holding means comprises a solid restraint attached to the device at one or more points by a soluble substance in such a manner that it holds the diaphragm in a flexed position, forcing the valve to remain closed and the first chamber sealed, until the soluble substance is dissolved by a suitable solvent, thereby releasing the solid restraint and allowing to valve to return to normal pressure activation.

38. The valve of Claim 37, wherein the soluble substance can be dissolved by an aqueous liquid.

39. The valve of Claim 38, wherein the soluble substance is a sugar compound or water soluble salt or polymer.