Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B17/00—Sorption machines, plants or systems, operating intermittently, e.g. absorption or adsorption type
  • F25B17/08—Sorption machines, plants or systems, operating intermittently, e.g. absorption or adsorption type the absorbent or adsorbent being a solid, e.g. salt
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B39/00—Evaporators; Condensers
  • F25B39/02—Evaporators
  • F25B39/026—Evaporators specially adapted for sorption type systems
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D2400/00—General features of, or devices for refrigerators, cold rooms, ice-boxes, or for cooling or freezing apparatus not covered by any other subclass
  • F25D2400/28—Quick cooling

Definitions

• the invention relates to temperature changing devices and, in particular, to portable or disposable food or beverage coolers.
• An alternate method for providing a cooled material on demand is to use portable insulated containers.
• 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.
• insulated containers are much more bulky and heavy than the food or beverage.
• 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, utilization 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.
• a portable cooling device 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.
• 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 utility in all these areas.
• 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.
• 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 rapid initial cooling effect gradually slows as a result of the both decrease in temperature of the object to be cooled and decrease in the heat transfer area of the first chamber.
• the decrease in heat transfer area is due to the fact that the portion of the first chamber in contact with the liquid decreases as the liquid vaporizes and the liquid level drops.
• the evaporation process is limited by the surface area from which the liquid can boil.
• the systems do not effectively minimize the amount of liquid which is entrained in the vapor phase caused by uncontrolled boiling of the evaporating liquid.
• one objective of the present invention is to provide a self-contained sorption cooling device with a means to alleviate the decrease in heat transfer as the liquid vaporizes and therefore speed the cooling process.
• Another object of the present invention is to accelerate the evaporation process by increasing the surface area from which the liquid can evaporate. As a result, the cooling process will be accelerated as well.
• Another object of the present invention is to control the evaporation process by limiting liquid entrainment in the vapor phase.
• the present invention is a miniaturized cooling device comprising a first chamber containing a liquid which preferably has a vapor pressure at 20'C of at least about 9 mm Hg, a second chamber containing a sorbent for the liquid, a conduit connecting the first and second chambers. a valve in the conduit for preventing flow through the conduit between the chambers and means for opening the valve.
• the second chamber is initially evacuated. Thus, when the valve is opened, the first and second chambers are connected and fluid communication between them is possible. This causes a drop in pressure in the first chamber because the second chamber is evacuated.
• the drop in pressure causes the liquid in the first chamber to vaporize, and, because this liquid-to-gas phase change can occur only if the liquid removes heat equal to the latent heat of vaporization of the evaporated liquid from the first chamber, the first chamber cools.
• the vapor passes through the conduit and into the second chamber where it is absorbed and adsorbed by the sorbent.
• the sorbent also absorbs all of the heat contained in the absorbed or adsorbed vapor, and, if the absorption-adsorption process involves a chemical reaction, the sorbent must also absorb the reaction heat.
• the liquid is water
• the first chamber's interior surface may be provided with a wicking material for the liquid.
• the wicking material lines the interior surface of the first chamber and consists of a highly hydrophilic material, such as gel-forming polymers and water-wicking polymers capable of coating the interior of the first chamber.
• the liquid is mixed with a nucleating agent that promotes ebullition of the liquid.
• a phase separator for preventing unvaporized liquid from the first chamber from passing through the conduit into the second chamber may advantageously be included in the device.
• the sorbent material may be an adsorbent or absorbent, and the second chamber preferably contains sufficient sorbent to absorb or adsorb substantially all of the liquid in the first chamber.
• the entire device is preferably disposable.
• the vaporization process causes the level of the liquid in the first chamber to drop, but, in the preferred embodiment, the wicking material retains the liquid on the interior surface of the first chamber. This maintains a substantial area of contact between the liquid and the interior surface of the first chamber to avoid a reduction in the effective heat transfer area of the first chamber and a resultant slowing of the cooling process.
• the present invention provides a self-contained rapid cooling device that cools a food, beverage, or other material or 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 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.
• a self-contained rapid cooling device that cools a food, beverage, or other material or 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 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.
• the figure is a schematic representation of a cooling device according to the present invention.
• the cooling device 10 has a first chamber
• the cooling device 10 also includes a second chamber 20 surrounded by a thermal insulator 22 which is at least partially filled with a sorbent 24.
• the second chamber may also advantageously be evacuated to the extent that it contains only the vapor of the refrigerant liquid.
• first and second chambers 12 and 20 Connecting the first and second chambers 12 and 20 is a conduit 28 and a valve 30 interposed in the conduit 28, allowing fluid communication between the chambers 12 and 20 through the conduit 28 only when the valve 30 is open.
• the operation of the cooling device 10 is suspended (i.e., the system is static and no cooling occurs) until the valve 30 is opened, at which time the conduit 28 provides fluid communication between the first and second chambers 12 and 20. Opening the valve 30 between the first and second chambers 10 and 20 causes a drop in pressure in chamber 12 because the second chamber 20 is evacuated.
• the drop in pressure in the first chamber 12 upon opening of the valve 30 causes the liquid 18 to boil at ambient temperature into a liquid-vapor mixture 32.
• This liquid- to-gas phase change can occur only if the liquid 18 removes heat equal to the latent heat of vaporization of the evaporated liquid 18 from the first chamber 12. This causes the first chamber 12 to cool. The cooled first chamber 12, in turn, removes heat from its surrounding material as indicated by the arrows 33.
• the liquid-vapor mixture 32 is directed through a liquid-vapor collector and separator 34 of conventional design, which separates the liquid 18 from the vapor, allowing the separated liquid 18 to return to the first chamber 12 through the liquid return line 38 and allowing the vapor to pass through the conduit 28 into the second chamber 20.
• a liquid-vapor collector and separator 34 of conventional design, which separates the liquid 18 from the vapor, allowing the separated liquid 18 to return to the first chamber 12 through the liquid return line 38 and allowing the vapor to pass through the conduit 28 into the second chamber 20.
• the vapor is absorbed or adsorbed by the sorbent 24. This facilitates the maintenance of a reduced vapor pressure in the first chamber 12 and allows more of the liquid 18 to boil and become vapor, further reducing the temperature of chamber 12.
• the continuous removal of the vapor maintains the pressure in the first chamber 12 below the vapor pressure of the liquid 18, so that the liquid 18 boils and produces vapor continuously until sorbent 24 is saturated, until the liquid 18 has boiled away or until the temperature of the liquid 18 has dropped below its boiling point.
• the level of the liquid 18 in the first chamber 12 drops.
• the wicking material 16 retains the liquid 18 on the interior surface 14 of the first chamber 12 to prevent a reduction in the area of contact between the liquid 18 and the interior surface 14 which would cause a reduction in the effective heat transfer surface area of the first chamber 12 and would thus slow the cooling process.
• 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 all three of 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.
• 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.
• 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.
• 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 ⁇ C of at least about 25 mm Hg and, more preferably, at least about 35 mm Hg.
• solid nucleating agents may be used, such as the conventional boiling stones used in chemical laboratory applications.
• the sorbent material used in the second chamber 20 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, sulphuric acid, lithium chloride, ethylene glycol and sodium sulfate.
• any of a number of materials may be chosen, depending upon the requirements of the system and the particular refrigerant liquid 18 being used.
• the wicking material may be something as simple as cloth or fabric having an affinity for the refrigerant liquid 18 and a substantial wicking ability.
• the wicking 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 wicking 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 consists of alkyl, aryl and a ino derivative polymers of vinylchloride acetate, vinylidene chloride, tetrafluoroethylene, methyl methacrylate, hexanedoic acid, dihydro-2,5-furandione, propenoic acid, 1, 3-isobenzofurandione, 1 h-pyrrole-2,5-dione or hexahydro-2 h-azepin-2-one.
• the wicking material may be sprayed, flocked, or otherwise coated or applied onto the interior surface of the first chamber.
• the wicking material is electrostatically deposited onto that surface.
• the wicking 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 first chamber.
• the wicking material is able to control any violent boiling of the evaporator and thus reduce any liquid entrainment in the vapor phase.
• the wicking material is a polymer forming a porous space-filling or sponge-like structure, and it may fill all or part of the first chamber.
• the thermal insulator 22 may be any conventional insulation material, but is preferably an inexpensive, easily-formed material such as a low-cost polystyrene foam.
• the valve may be selected from any of the various types shown in the prior art.
• 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; opening the valve between the first chamber 12 and the second chamber 20, whereby the pressure in the first chamber is reduced, causing the liquid to boil, forming a vapor, which vapor is collected by the sorbent material; and 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.
• the process is preferably a one-shot process; thus, opening of the valve 30 in the conduit 28 connecting the first chamber 12 and the second chamber 20 is preferably irreversible.
• 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 either the first chamber 12 or the second chamber 20.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Sorption Type Refrigeration Machines (AREA)

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Publications (2)

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• 1988
  • 1988-07-01 IN IN457/MAS/88A patent/IN171470B/en unknown
  • 1988-07-05 WO PCT/US1988/002258 patent/WO1989000271A1/en not_active Application Discontinuation
  • 1988-07-05 EP EP19880906703 patent/EP0368910A4/en not_active Withdrawn
  • 1988-07-05 JP JP63506713A patent/JPH02504304A/ja active Pending
  • 1988-07-06 IN IN474/MAS/88A patent/IN172154B/en unknown
  • 1988-07-06 CA CA000571231A patent/CA1298093C/en not_active Expired - Fee Related

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Non-Patent Citations (1)

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