Abstract:
An apparatus for cooling a target in a region having a first pressure. The apparatus includes a compressor for compressing a gas to a second pressure higher than the first pressure, means for cooling the compressed gas to a selected temperature downstream of the compressor, and means for discharging the compressed gas towards the target at a selected rate downstream of the cooling means. A pressure tank is provided downstream of the compressor for receiving compressed gas from the compressor and supplying the gas to the discharging means. The second pressure, selected temperature, and selected rate are chosen so as to cool the target upon expansion of the gas in the region. A method of cooling a target using the apparatus is also disclosed.

Description:
The present application claims the benefit under 35 U.S.C. Section 119(e) of U.S. provisional application Ser. No. 60/131,490 filed Apr. 29, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an apparatus and method for cooling bodies or chambers using the phenomenon of cooling by decompression and expansion of compressed gas. 
     BACKGROUND TO THE INVENTION 
     Methods for cooling bodies, such as objects, in gases is known. For example, objects are cooled in commonly-used refrigerators and freezers by contact with cooled air. The air is cooled by passing relatively warm air over a heat exchanger in which there is a cooler fluid. The fluid is cooled by evaporative cooling of a low boiling liquid, e.g. a CFC or HCFC fluorocarbon, in a closed cycle system. 
     Methods for cooling gases and liquids are also known, apart from evaporative cooling. One method involves bubbling gas though a cool liquid. For example, M. A. Krongold, in U.S. Pat. No. 4,607,489, which issued Aug. 26, 1986, discloses cooling gas by bubbling the gas through a cryogenic liquid. B. Adolfsson, in PCT Publication WO95/09124, published Apr. 6, 1995, discloses introducing carbon dioxide below the surface of a liquid, wherein the expansion of the carbon dioxide cools the liquid. 
     The phenomenon of cooling gases by their expansion is known. The present invention utilizes this phenomenon to cool a target such as bodies or chambers, preferably without the necessity of closed cycle systems or environmentally or physiologically problematic materials such as CFCs or HCFCs. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention provides an apparatus for cooling a target in a region having a first pressure. The apparatus includes a compressor for compressing a gas to a second pressure higher than the first pressure, means for cooling the compressed gas to a selected temperature downstream of the compressor, means for discharging the compressed gas towards the target at a selected rate downstream of the cooling means, and a pressure tank downstream of the compressor for receiving compressed gas from the compressor and supplying the gas to the discharging means. The second pressure, selected temperature, and selected rate are chosen so as to cool the target upon expansion of the gas in the region. 
     In a first embodiment, the apparatus may be for cooling a chamber. The chamber may be a vehicle interior, such as a cabin of an automobile, a room in a building, or an interior of a movable structure, such as a trailer. The gas may be air and the discharging means may be adapted to discharge air into the chamber. 
     In a second embodiment, the apparatus may be for cooling a part of an animal and the discharging means may be in the form of a hand-manipulable tube with an expansion nozzle at one end of the tube. 
     In a third embodiment, the apparatus may be for cooling a liquid. The discharging means may be positioned in the liquid for discharging compressed gas into the liquid to thereby cool the liquid. 
     There may be two or more of the aforesaid pressure tanks arranged in parallel for alternately receiving compressed air from the compressor and alternately supplying the air to the discharging means. 
     The cooling means may be associated with the pressure tank to cool compressed gas in the pressure tank to the selected temperature. 
     Furthermore, the compressor may be a primary compressor and the pressure tank may be a primary pressure tank. The apparatus may further include an ancillary compressor upstream of the primary compressor for pre-compressing air to be further compressed by the primary compressor, and an ancillary pressure tank, downstream of the ancillary compressor, for receiving compressed air from the ancillary compressor and supplying compressed air to the primary compressor. 
     The apparatus may further include a turbine downstream of the primary pressure tank and coupled to the ancillary compressor, the turbine being adapted to receive compressed air from the primary pressure tank and convert energy in the compressed air into energy for powering the ancillary compressor. 
     The apparatus may also include means associated with the primary compressor for selectively taking air from the ancillary pressure tank or the is atmosphere and directing the air to the primary compressor. 
     The primary compressor may be adapted to compress air to between 290 psi and 3000 psi. 
     The selected temperature may be about ambient temperature and the cooling means may be a heat exchanger. Furthermore, there may be a fan associated with the heat exchanger for cooling the heat exchanger. 
     In accordance with another aspect, the invention provides a method for cooling a target in a region having a first pressure including the steps of: 
     (a) providing a compressor for compressing a gas to a second pressure greater than the first pressure; 
     (b) providing means for cooling the compressed gas to a selected temperature downstream of the compressor; 
     (c) providing means for discharging the gas towards the target in the region at a selected rate; and 
     (d) providing a pressure tank, downstream of the compressor and upstream of the discharging means, for receiving compressed gas from the compressor and supplying the gas to the discharging means; 
     wherein the second pressure, selected temperature, and selected rate are chosen so as to cool the target upon expansion of the gas in the region. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be described with reference to the drawings in which: 
     FIG. 1 is a diagrammatic view of an apparatus according to a first preferred embodiment of the invention in the form of an air conditioner for a cabin of an automobile; 
     FIG. 2 is a diagrammatic view of an apparatus according to a second preferred embodiment of the invention in the form of a hand tool for cooling parts of animals; 
     FIG. 3 is a schematic view of a container being cooled using a plurality of air jets; 
     FIG. 4 is a diagrammatic view of an air conditioner for an automobile according to a third preferred embodiment of the invention; and 
     FIG. 5 is a diagrammatic view of an apparatus according to a fourth preferred embodiment of the invention for cooling liquids. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, an air conditioner  5  for a vehicle (which in this embodiment is an automobile) according to a first preferred embodiment, is shown. The air conditioner  5  has an air inlet  11  which leads into a compressor  12  for compressing the air, as will be further described. Compressor  12  is connected to a pair of parallel pressure tanks  14   a,    14   b  by means of respective pipes  13   a,    13   b.  The pressure tanks  14   a,    14   b  store compressed air received from the compressor  12  for subsequent discharge. Furthermore, the pressure tanks  14   a,    14   b  have respective heat exchangers  15   a,    15   b  therein for cooling the stored compressed air to about ambient temperature. The heat exchangers  15   a,    15   b  are in turn cooled by respective fans  10   a,    10   b  in a known manner. Pressure tanks  14   a,    14   b  are connected to respective tubes  16   a,    16   b  leading into a cabin  21  of the automobile. The tubes  16   a,    16   b  have respective outlets  17   a,    17   b  which, in turn, have respective mufflers  18   a,    18   b  and filters  22   a,    22   b  associated therewith for reasons as will be explained. Control valves  19   a,    19   b  are provided in the tubes  16   a,    16   b  for controlling the discharge of cooled compressed air, as will also be further explained. 
     In operation, air from outside the automobile is sucked into compressor  12  and compressed to a selected pressure higher than the pressure in the cabin  21  (which, in this example, is about 14.65 psi or about 101 Kpa). In this embodiment, the selected pressure is approximately 1600 psi. However, the pressure may be in the range of about 290 psi to about 2900 psi (about 2 Mpa to about 20 Mpa). Control means (not shown) regulates valves  6   a,    6   b  to cause compressed air from compressor  12  to be supplied alternately to pressure tanks  14   a,    14   b  when pressure within the pressure tanks  14   a,    14   b  falls below a threshold value. Similarly, the control means turns compressor  12  off when the pressure within pressure tanks  14   a,    14   b  is at or above the threshold value. The pressure tanks  14   a,    14   b  store the compressed air which is cooled by the heat exchangers  15   a,    15   b  to about ambient temperature as determined by temperature sensors (not shown) in the pressure tanks  14   a,    14   b.    
     When the cabin  21  is to be cooled, as determined by a thermostat (not shown) contained in the cabin  21 , the control means opens one of the valves  19   a,    19   b  and cooled compressed air is discharged into the cabin  21  from the associated pressure tank  14   a,    14   b  through the associated tube  16   a,    16   b,  and outlet  17   a,    17   b.  The expansion of the cooled compressed air into the cabin  21  produces a cooling effect. If the supply of cooled compressed air contained in the subject pressure tank  14   a,    14   b  has been reduced to a level insufficient to effect cooling of the cabin  21 , the valve  19   a,    19   b  that was opened is closed and the other valve  19   a,    19   b  is opened to allow cooled compressed air to be discharged from the other pressure tank  14   a,    14   b.  As mentioned above, the supply of compressed air within pressure tanks  14   a,    14   b  is replenished automatically by the control means. However, the compressed air is not discharged from the pressure tanks  14   a,    14   b  until it has been cooled to about ambient temperature. It will be appreciated that the capacity of the compressor  12  to compress air, and the capacity of the heat exchangers  15   a,    15   b  to cool the compressed air in the pressure tanks  14   a,    14   b,  will be engineered (as is known in the art) to ensure that there is a constant supply of cooled compressed air available to cool the cabin  21  when required. 
     In this embodiment, the cooled air produced by expansion of the compressed air is circulated within the cabin by means of a fan (not shown). However, circulation of cooled air may also occur merely by convection and the kinetic energy of the released air. 
     The mufflers  18   a,    18   b  are provided to reduce the noise from expansion of the air. The filters  22   a,    22   b  are used to clean the discharged air of dust and other airborne particles. 
     The compressor  12  is powered by the motor of the automobile. The cooling heat exchangers  15   a,    15   b  associated with the pressure tanks  14   a,    14   b  are placed so that air may pass over the heat exchangers  15   a,    15   b  in the same way as air passes over the radiator for the motor of the automobile. Thus, the cooling effect of the fans  10   a,    10   b,  is supplemented by the cooling produced by outside air flowing over the heat exchangers  15   a,    15   b  while the automobile is in motion. When the automobile is stationary, the fans  10   a,    10   b  provide the only source for cooling of the heat exchangers  15   a,    15   b.    
     It will be understood that, for greater energy and cooling efficiency, some of the air from the cabin  21  can be recirculated into intake  11 . It will be further understood that in order to minimize ice build-up within the air conditioner  5 , means can be provided to remove moisture from the compressed air, in a known manner. 
     The heat exchangers  15   a,    15   b,  although being internal to pressure tanks  14   a,    14   b,  may alternatively be external to pressure tanks  14   a,    14   b,  e.g. cooling fins on the outside of the tanks. In this embodiment, the heat exchangers are cooled using fans  10   a,    10   b.  However, it will be appreciated that the heat exchangers may be a part of known closed cycle cooling systems is employing a low boiling fluid therein, e.g. a CFC or HCFC. In the alternative, the heat exchangers may be cooled using known water cooling systems. 
     It will appreciated that there may be more than two pressure tanks in parallel or there may be only a single pressure tank, as in the case of the other preferred embodiments of the invention to be now described. In such cases, the capacity of the compressor and cooling means will be adjusted accordingly. 
     Referring to FIG. 2, a hand tool  30  for cooling parts of animals or humans, such as warts, is shown. The hand tool  30  has an air inlet  31 , compressor  32 , air outlet  33 , and pressure tank  34  with external cooling fins  35  for cooling the air in the pressure tank  34  to close to ambient temperature. A flexible tube  36  from pressure tank  34  is coupled to another flexible tube  40  which, in turn, is coupled to a tubular wand  39  having an expansion nozzle at one end. The expansion nozzle has a manually operable valve  38  close to an outlet  37  of the nozzle. 
     In operation, air from inlet  31  is compressed by compressor  32  and cooled in pressure tank  34 . The compressed air is released on demand by means of the manually operable valve  38 . Flexible tube  40  allows the outlet  37  to be directed to the part of the body to be cooled, e.g. a wart. Depending on the application, other gases may be used such as nitrogen, helium and carbon dioxide. 
     FIG. 3 illustrates schematically another application of the principle employed by the present invention. Compressed gas is supplied to a plurality of jets  41  directed at a container  42 . The expansion of compressed gas exiting the jets  41  cools the gas which, in turn, cools the container  42 . The advantage of using a plurality of jets  41  is that cool gas may be applied to a large surface area of the container  42  thereby achieving an increase in the rate of cooling of the contents of the container  42 . The rate of cooling is further increased by the fact that the gas is not essentially stationary as in the case of conventional refrigerators, for example. 
     Referring now to FIG. 4, an air conditioner  50  for cooling a cabin  61  of an automobile according to a third preferred embodiment of the invention is shown. The air conditioner  50  has an air inlet  51  which allows air to flow passively into an ancillary compressor  63  for compressing the air. In this embodiment, air inlet  51  is outside of the automobile cabin  61 . However, inlet  51  may alternatively be inside cabin  61 , or with suitable valves and controllers, there may be air inlets both inside and outside cabin  61 . Ancillary compressor  63  is connected by pipe  64  to ancillary pressure tank  65  for storing compressed air from the ancillary compressor  63 . Ancillary pressure tank  65  is, in turn, connected by pipe  66 , via valve  70 , to primary compressor  52  for further compressing the air. Primary compressor  52  also has an air inlet pipe  67  connected to an air inlet (not shown) outside cabin  61  from receiving air from atmosphere. It should be appreciated, however, that the air inlet may be inside cabin  61  or, with suitable valves and controllers, there may be air inlets both inside and outside cabin  61 . Control means (not shown) operate to open a valve  68  in the air inlet pipe  67  when pressure in ancillary tank  65  is low, as detected by pressure gauge  69 . When the pressure in ancillary tank  65  is at or above a threshold value, the control means causes valve  68  to close and valve  70  to open (as will be further described). 
     Primary compressor  52  is connected to a primary pressure tank  54  by means of a pipe  53 . Primary pressure tank  54  stores compressed air from the primary compressor and has heat exchanger fins  55  attached thereto for cooling the compressed air stored in the tank  54  to about ambient temperature. 
     Primary pressure tank  54  is connected to tube  56  which has an outlet into turbine  58 . Air entering turbine  58  is able to turn rotors (not shown) which are mounted on shaft  62 . A tube  57  receives air leaving the turbine  58  and discharges it into the cabin  61 . Tube  56  has a control valve  59  therein for regulating the discharge of cooled compressed air into the cabin  61 . Turbine  58  is connected by shaft  62  to ancillary compressor  63 . Thus, the flow of compressed air past the rotors of the turbine cause it to turn and generate current for powering ancillary compressor  63 . In this embodiment, the compressors  52  and  63 , and pressure tanks  54  an  65  are outside the cabin  61  and tube  57  extends through interior wall  60  into the cabin  61 . Although, turbine  58  is outside cabin  61 , it may alternatively be inside cabin  61 . 
     In operation, when the cabin  61  needs to be cooled, as determined by a temperature sensor (not shown) in the cabin  61 , valve  59  is opened by the control means and cooled compressed air is discharged through tube  56  from primary pressure tank  54 . The compressed air partially expands and cools as it flows through turbine  58 . Some of the kinetic energy of the expanding air is converted by the turbine  58  into useful power which is used to operate ancillary compressor  63  which compresses air from inlet  51 . The compressed air is then stored in ancillary pressure tank  65 . 
     When the pressure in ancillary pressure tank  65  is at or above a predetermined pressure, as determined by pressure gauge  69  of the control means, valve  68  is closed and valve  70  is opened so that the compressed air from the ancillary pressure tank can flow into primary compressor  52  for further compressing. The further compressed air is then stored and cooled to about ambient temperature in primary pressure tank  54 . When the pressure in ancillary pressure tank  65  is below the predetermined pressure, valve  68  is opened and valve  70  is closed by the control means so that atmospheric air is drawn directly into primary compressor  52 . Thus, this embodiment is intended to achieve some cost savings by capturing some of the energy from discharged air and using the energy to pre-compress air in the ancillary compressor. 
     As mentioned above, the air inlet connected to air inlet pipe  67  may be inside cabin  61 . In such event, the apparatus  50  permits the recirculation of air within the system. 
     The air conditioner  50  may be modified for use in cooling liquids, as shown in FIG. 5 (which appears next to FIG.  2 ). This Figure shows a liquid cooling apparatus  80  which is similar in every respect to the air conditioner  50  except as follows. The apparatus  80  has an outlet  82  configured so that it may be positioned in a liquid  84  contained in a vessel  86 . Thus, compressed air may be bubbled through the liquid  84  to cool the liquid  84 . In this embodiment, the control means includes a manually operable switch (not shown) used to open valve  86  to release cooled compressed gas from a primary pressure tank  88 . Thus, the discharge of the cooled compressed gas into the liquid may be controlled at will. It will be understood that other gases may be used such as carbon dioxide, and that the capacity of the compressors and cooling fins will vary to suit the application. 
     Although not shown in the drawings, the apparatus of the invention may be installed in a building for cooling a room of the building. In buildings with forced air heating, cooling and ventilating systems, cooled compressed air may be discharged into a plenum which leads into a forced air heating, cooling and ventilating system of the building. 
     The apparatus may also be installed in a trailer pulled by a truck or a refrigerator car pulled by a locomotive to cool the interiors of these structures. 
     As is known, the temperature differential between the compressed gas and expanded gas is controlled by the pressure differential. Therefore, the rate of cooling can be altered by altering the pressure to which the gas is compressed for a given pressure in the region of the target (i.e. object or chamber) to be cooled. The rate of cooling can also be altered by the rate of discharge of the compressed gas towards the target, as well as by the temperature to which the pressurized gas is cooled by the cooling means of the apparatus prior to discharge. It will be appreciated that the pressure to which the gas is compressed, the temperature to which the gas is cooled, and the rate of discharge of the gas towards the target are selected to effect the desired cooling of the target, will vary to suit the particular application, and can be determined by simple experimentation. 
     One advantage of the present invention is the use of universally available gases, e.g. air, as the cooling medium, instead of CFCs, HCFCs, etc., for example. Another advantage associated with systems having electrically driven compressors is that the capacity for cooling can be generated at times when demand for electricity is off peak, thus providing for more efficient use of electrical generating resources. 
     It will be appreciated that the foregoing description is by way of example only and is not meant to limit the scope of the invention as defined by the following claims.