WO2008150434A1

WO2008150434A1 - Heat exchanger

Info

Publication number: WO2008150434A1
Application number: PCT/US2008/006827
Authority: WO
Inventors: Rodney Hugelman
Original assignee: Whitemoss, Inc.
Priority date: 2007-05-31
Filing date: 2008-05-30
Publication date: 2008-12-11

Abstract

A heat exchanger in which a high pressure first fluid refrigerant is circulated through channels in heat exchange tubes and transfers heat to a second refrigerant fluid which is at a low pressure. The first fluid refrigerant flows in one direction through the heat exchanger and the second refrigerant fluid travels in an opposite direction. The first fluid refrigerant is preferably carbon dioxide. A system that employs the heat exchanger is a two loop system in which a first loop is a low pressure hot liquid loop that uses the heat exchanger to heat the working fluid that supplies heat for the end use such as a hot water heater or heat pump. The second loop is a low pressure cold liquid loop that uses a second heat exchanger to cool the liquid used in an air conditioning system. For safety, the low pressure loops are the only loops that enter the residence or space where the occupants are located. The high pressure gas remains segregated from the first and second low pressure loops.

Description

UNITED STATES DEPARTMENT OF COMMERCE PATENT AND TRADEMARK OFFICE I. FIELD OF THE INVENTION This invention relates to heat exchangers and more particularly to heat exchangers that employ a two loop system. One loop is a hot liquid loop and the second loop is a cold liquid loop.

II. BACKGROUND OF THE INVENTION The use of compression and expansion of refrigerants in the refrigeration cycle is well known in the art. Heat exchangers using refrigerant compression cycles are often used for cooling or heating the air for comfort in residences, commercial buildings, and vehicles. Typically, a heat exchange system utilizing the refrigerant compression cycle includes a compressor, a condenser, an expansion device, an evaporator, and conductive fins for collecting and dispersing heat. The refrigerant flows in a cycle among the heat exchanger's components. The refrigerant is first compressed to a hot gas by the compressor as the temperature elevates due to the higher pressure, which aids its conversion from a hot gas to a warm state as it passes through the condenser. This portion of the cycle produces heat which is commonly transferred to air passing over the cooling fins of the condenser, thus dissipating this unused or wasted heat to the atmosphere in a typical air conditioner cooling system. The now warm, often liquid refrigerant, then flows through an expansion device rapidly expanding as a cold low pressure gaseous/liquid fluid. Finally, this cold fluid passes through an evaporator which is a heat exchanger that warms the cold fluid refrigerant to assure its return back to the compressor as a gas. The evaporator absorbs heat from an external heat source which is the primary cooling function of an air conditioning application for a building or other space. At this point, the warmed gaseous refrigerant returns to the compressor in order to repeat the cycle. A typical heat pump functions in much the same way, but includes in the equipment a reversing valve that reverses the refrigerant flow which makes the condenser the evaporator and the evaporator the condenser, thus removing heat from the air outside to perform a heating operation which in turn makes the ambient temperature outside infinitesimally cooler and of no consequence. In a conventional residential air conditioning unit, the compressor and condenser are both usually mounted in an enclosure outside of the home or structure. The refrigerant is compressed and condensed within the outside enclosure, allowing the resulting unused or waste heat to be dissipated to the atmosphere outside of the residence. The condensed refrigerant which is now warm liquid remains at a relatively high pressure until it is expanded causing it to rapidly lose pressure and become a cold lower pressure liquid. As this cold refrigerant, which is now in a liquid state, flows through coiled heat exchanger piping of the evaporator inside of the house, a fan blows inside filtered air through the exchanger coil. This cools the inside air, which is then fed into ductwork, dispersing it throughout the house. Any liquid refrigerant is thus evaporated to assure a return of warm refrigerant gas to the compressor to complete the cycle. Early heat exchange systems used natural refrigerant fluids like ammonia (NH₃₎ and sulfur dioxide (SO₂). While these options worked as refrigerants, they are both toxic and corrosive, making them undesirable in most applications. A host of, low pressure synthetic chemical refrigerant substitutes were developed over time, ^' such as R- 12 and R-22 (commonly called Freon) and are chlorofluorocarbon (CFC) gases. These were later followed by hydrofluorocarbon (HFC) gas refrigerants. CFCs and HFC's, i.e., FC refrigerants, have been widely used for more than 40 years for residential and vehicular air conditioning, refrigerators and freezers, and heat pump applieations to name only a few applications. FC refrigerants are somewhat less toxic and corrosive, making them less harmful and friendlier to both humans and equipment than ammonia or sulfur dioxide, and they also work at relatively low operating pressures. Low operating pressure makes a mechanical system simpler to build. CFCs have high atmospheric ozone depletion (ODP) designations and are now banned entirely due to the Montreal Protocol, but HFC's continue to have very high global warming potential (GWP), which is thousands of times more damaging to the atmosphere than natural carbon dioxide, which has a designated GWP of 1 which is the standard. The CFCs road to obsolescence as a refrigerant began when 150 countries signed the Montreal Protocol in 1987. The Montreal Protocol was a treaty designed to reduce the volume of ozone depleting materials in the earth's atmosphere. As a member of the treaty, the United States implemented a phase-out schedule for R- 22. Beginning in 2010, manufacturers will be forbidden from making R-22 to service new air conditioners and heat pumps. All new heat exchangers must be made using R-22 that has been recovered and recycled from existing equipment. Beginning in 2020, US manufacturers will be forbidden from making R-22 for use in existing air conditioners and heat pumps. The European community has already phased out R-22, and appears to be looking to phase out all FC refrigerants in the near future. The most common replacement for CFC are the large variety and blends of HFC refrigerants. A more recent introduction has been R-410A. Because these chemical compounds lack chlorine, they are not an ozone depleting threat like R-22. However, these chemicals have their own set of limitations. R-410A for example, has a global warming potential of 1725, which is roughly equivalent to that of R-22 but still 1,725 times that of CO₂. In current residential air conditioning systems, R-410A must also be compressed to roughly 500 psi when piped into the home. This creates a safety risk for residents should one of the connections be broken or should one of the pipes burst or become ruptured. Finally, because of their higher pressures and greater complexities, systems that use R-410A are typically much more expensive to install and maintain than those using R-22, particularly when an installer is attempting to

retrofit a structure that now contains an old R-22 or other HFC system.

III. SUMMARY OF THE INVENTION It is an object of the invention to use a heat exchanger that employs a new and unique design for heat transfer between a high pressure gas and a safe low pressure liquid. It is another object of the invention to heat or cool air, water, or other fluids using a two loop heat distribution system. Each loop requires one of the unique heat exchangers, one loop being a hot liquid delivery loop and one loop being a cold liquid delivery loop. The first loop uses a first heat exchanger using a working high pressure, high temperature fluid, usually a gas, to interface with a low pressure hot liquid loop for hydronic distribution and end uses such as a hot water heater or a hydronic room radiator or alternatively deliver heat for end use using a secondary hydronic-to-air heat transfer coil in an air handler for the purpose of distribution of heat to a specific room or location with warm forced air. The second loop uses a second heat exchanger to service a low pressure cold liquid loop that supplies a secondary heat exchanger with cold liquid which is used for cooling purposes such as in an air conditioning system. A high pressure, low temperature fluid, also preferably a gas, circulates through the second heat exchanger. Both the first and second heat exchangers may reside within an enclosure operable with a compressor and a pumping system which forms a unit for the purpose of pumping heat remotely from the unit in the form of low pressure liquid through the two hot and cold distribution loops. For increased safety, the low pressure loops may be the only loops that enter a residence or space where occupants are located. The high pressure gas does not enter the house or occupant's space and remains segregated from the first and second low pressure loops. In one embodiment, two heat exchangers are located adjacent to a high pressure compressor. The heat exchangers are contained within pressure vessels that have a central cylindrical body with substantially flat end plates at opposite ends. Hemispherical end cap domes are bolted to the opposite ends of the cylindrical body. The end cap domes are designed for the flow of high pressure fluid from one end through to the other, and each have passageways or flow holes in their ends for connection to fluid inlet and outlet lines. The high pressure fluid moves from one end cap to the other through a plurality of narrow tubes or "micro channels" formed in a strip or ribbon of aluminum that extend through the cylindrical body and are held in place by the end plates. The mounting of the strips or ribbons may be reinforced by a matrix of supporting members. The end plates have a plurality of holes to receive the strips or ribbons having the micro channels in them. The strips can be brazed to the end plates for sealing purposes. The end plates may also have a plurality of holes tapering inwards to receive the strips or ribbons having the micro channels in them. The strips can then be sealed in the hole using an elastomeric seal which is compressed into place by the high pressure fluid within the end caps. Low pressure liquid or fluid enters the cylindrical body at one end through an inlet and exits at an opposite end through an outlet. As the low pressure fluid flows through the cylindrical body, the low pressure fluid absorbs heat from or delivers heat to the strips. The low pressure liquid, with its temperature changed, then flows away from the heat exchanger to be used in the specified application. In a particular embodiment of the invention, the high pressure fluid is a gas, as exemplified by carbon dioxide, and the low pressure fluid is a liquid, as exemplified by a water/glycol mixture. One application for the invention is as a heating and air conditioning heat pump unit for a building, in which the compressor is powered by line alternating current. Another application is in a vehicle in which the compressor is powered by either direct current or a hydraulic motor. As an air conditioner, the low pressure cold liquid is cooled through the cylindrical body of the heat exchanger by means of expanding and cooling the high pressure fluid or gas. The low pressure liquid is pumped away from the heat exchanger into either a building or a different area of the vehicle, where it passes through a coiled section of tubing. A fan blows air over the cooled section of tubing to cool the air. In another application such as a heater, the low pressure liquid is heated through the cylindrical body of the heat exchanger with high pressure high temperature fluid or gas. The low pressure fluid is pumped away from the heat exchanger into either a building or a different area of the vehicle, where it passes through a coiled section of tubing. A fan blows air across this tubing, heating the air which is distributed throughout the building or vehicle. As a water heater, the apparatus operates the same except that water is passed over the coiled tubing to transfer heat from the low pressure liquid to the water. In another embodiment of the invention, the high pressure fluid is a gas, as exemplified by carbon dioxide, and the low pressure fluid is water for auxiliary heating or cooling. The water at low pressure passes through either the heating loop or the cooling loop, after which it undergoes some additional heating or cooling to be used as a water supply.

IV. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional side view of the heat exchanger in accordance with the invention. FIG. 2 is an end view of the micro channel matrix array with the high pressure end plate and high pressure end cap removed. FIG. 3 is an end view of the high pressure end plate with the high pressure end cap removed showing the ends of the heat exchange tube, strip or ribbon and the micro channel array passing through the end plate. FIG. 4 is an end view of the low pressure area plastic filler inserts. FIG. 5 is an end view of the supporting members located between adjacent strips. Fig. 6 is a perspective view of a single heat exchange tube, strip or ribbon with a plurality of micro channels. Fig. 7 is a schematic diagram showing fluid flow in a two loop air conditioning and heating system using a conventional compressor or pump and the heat exchangers of the present invention. Fig. 8 is a schematic diagram showing fluid flow in a two loop air conditioning and heating system using a compression/expansion engine and the heat exchangers of the present invention. Fig. 9 is a cross sectional view of the heat exchange tube sealed to the end plate using an elastomeric seal. IV. DETAILED DESCRIPTION QF THE INVENTION Turning first to Fig. 1, there is illustrated a cross sectional view of a heat exchanger 10 of the present invention. The heat exchanger has a cylindrical shell 12 and two opposite hemispherical high pressure end caps 14, 16. One of the end caps 14 has a high pressure inlet 18 and the other end cap 16 has a high pressure outlet 20. The cylindrical shell 12 has a low pressure fluid inlet 22 and a low pressure fluid outlet 24, directing the low pressure fluid flow in the opposite direction of the high pressure fluid flow. Despite the opposite flow directions, the two fluids do not come into contact with one another as they are contained in separate fluid flow channels as will be more fully described herein. High pressure end plates 26, 28 are located at either end of the cylindrical shell 12. The high pressure end plates 26, 28 and end caps 14, 16 are securely mounted to the cylindrical shell 12 by means of a series of bolts 30 screwed into threaded holes 31. A high pressure region 32 is formed in the dome area between the end cap 14 and the high pressure end plate 26. A second high pressure region 34 is formed in the dome area between the end cap 16 and the high pressure end plate 28. The high pressure regions 32, 34 are maintained by a face seal 36 located between the end plates 26, 28 and the high pressure end caps 14, 16. As seen in Fig. 2, which is an end view looking into the cylindrical shell 12, there are a plurality of heat exchange tubes also called extruded strips or ribbons 38 mounted lengthwise in the cylindrical shell 12. As seen in Fig. 6, each strip 38 contains a plurality of small holes or micro channels 40 that extend through the entire length of the strip 38. These micro channels 40 define fluid passageways through the length of the strips 38. The strips 38 are spaced in the cylindrical shell 12 of the heat exchanger 10, extending parallel to the long axis of the cylindrical shell 12. The strips 38 are mounted between the two high pressure end plates 26, 28. The ends of the strips 38 can be welded or brazed to the end plates so that a fluid tight seal is formed around the junction between the end plates 26, 28 and the strips 38. As seen in Fig. 9, the strip 38 can also be attached to the high pressure end plate 26, 28 by inserting the strip 38 through an opening 39 in the end plate 26. A swage tool (not illustrated) flares the end of the opening 39 and leaves a small triangular shaped gap 41 that is filled with an elastomer. The high pressure in the micro channels 40 seals and wedges the strip 38 to the opening 39 in the end plate 26. The strips can be further supported by and held in place by a matrix of thin ribbons or supports 42 located between the strips 38 as depicted in Fig. 2. The metal ribbons or supports by themselves are seen in Fig. 5 wherein the strips 38 are removed for clarity. The metal ribbons may also cause the agitation and improved heat transfer of a refrigerant passing through the metal ribbons and against the strips 38. Claims wherein the exterior of the strips configure a spacing and flow. The micro channel strips 38 are available in a variety of crossections from the simple shape of Fig.6 to more complex extrusions with v-fins. Depending upon the application and flow volume desired, two halves of a plastic filler 44 are fitted into the central portion of the cylindrical shell 12 which defines a low pressure region 46 in the cylindrical shell 12. The plastic filler 44 surrounds the strips 38. The plastic filler 44 is secured to the end plates 26, 28 so that it is securely positioned within the cylinder shell 12. The plastic filler 44 also helps secure in place the strips or ribbons 38. In the preferred embodiment, the high pressure end plates 26, 28, and matrix of strips 38 are all made of aluminum. Furthermore, the micro channels themselves will be between 1 and 5 millimeters in diameter, resulting in low hoop stresses despite the high pressure of fluid flowing through them. The opposing ends of the microchannel tube array may be counterrotated some degree, preferably less than 45 degrees imparting a twist in the tubes 38 which enhances scrubbing of the high pressure gas on the inside of the tube 38 and therefore the tube's ability to conduct heat from or to the gas passing through the microchannels 40. One preferred application of the heat exchanger 10 is seen in Fig. 7. Here the invention is used in a dual loop system, the first loop being a hot liquid loop used as a heating source for heating water and the second loop being a cool liquid loop used in an air conditioning system for supplying cool air for individual comfort. This application requires a first heat exchanger 48 and a second heat exchanger 50. A high pressure compressor 52 compresses and supplies to the first heat exchanger 48 a hot compressed fluid, which in this embodiment is carbon dioxide gas. The first heat exchanger 48 receives the CO₂ at a high temperature of approximately 150⁰F - 250⁰F and at a pressure of between 1300 and 2000 psi and preferably between 1500 and 1800 psi. The CO₂ travels through high pressure line 53 from the high pressure compressor 52 and enters the first heat exchanger 48 at the high pressure inlet 18. The CO₂ fills the high pressure region 32 at the inlet pressure. Due to the high pressure, the CO₂ then enters the micro channels 40 and passes out from the high pressure end 32. The CO₂ travels through the entire length of the strips 38 and exits into the opposite high pressure region 34 where it then exits the heat exchanger 48 through the high pressure outlet 20. At this point the CO₂ is still at substantially the same high pressure as when it entered the heat exchanger 48, but the temperature has dropped due to its transferring heat through the strips 38. The hot liquid loop provides the heat for a water heater or other similar application. The hot liquid loop is comprised of a hot water heat exchanger 54, first heat exchanger 48, pump 56, and piping to contain and circulate a heat transfer fluid. The hot water heat exchanger 54 has internal heat transfer means such as coils or fins as is commonly known in the art. A heat transfer fluid, which is preferably a liquid water/glycol solution, flows from the hot water heat exchanger 54 through pipe 55 to the heat exchanger 48. The liquid enters the first heat exchanger 48 at the low pressure fluid inlet 22. The liquid flows through the low pressure region 46 in the cylindrical shell 12 and exits the cylindrical shell 12 at the low pressure fluid outlet 24. The temperature of the liquid is raised as the liquid flows through the low pressure region in the shell 46 because it is in contact with the strips 38 that carry the high pressure high temperature CO₂. The heat from the strips is transferred to the fluid during the flow through the low pressure region 46. It should be noted that the flow of the CO₂ is in one direction and the flow of the liquid is in an opposite direction to enhance the transfer of heat. The hot liquid exiting the first heat exchanger 48 by means of the low pressure fluid outlet 24 enters a feed pipe 58 and is pumped into the inlet of the hot water heat exchanger 54. In the hot water heat exchanger the heat from the fluid is transferred to the domestic hot water supply line or storage tank in a conventional manner for domestic use. The second part of this embodiment is the cold liquid loop. The CO₂ exiting the first heat exchanger 48 at the high pressure outlet 20 enters a pipe 60 that carries the CO₂ to an expansion valve 62. This allows the CO₂ to expand and cool. The cooled CO₂ is still in a gaseous state and at a pressure of approximately 300 to 500 psi. This pressure is sufficient to bring the carbon dioxide into a super critical state where it is very compressed, but remains gaseous. The cooled CO₂ enters the second heat exchanger 50 or evaporator. The second heat exchanger 50 is substantially identical to the first heat exchanger 48. The CO₂ enters the high pressure region 32 and flows through the micro channels 40 in the plurality of strips 38. The CO₂ then exits the second heat exchanger 50 at the high pressure outlet 20 and returns via pipe 64 to the high pressure compressor 52. The cool liquid loop is comprised of an evaporator or cold fluid heat exchanger 66, a fan 67 that forces air over or through the evaporator 66, the second heat exchanger 50, a pump 68, and piping to contain and circulate a cool or cold heat transfer fluid. As in the hot liquid loop, the preferred heat transfer fluid is a water/glycol solution. The fluid enters the second heat exchanger 50 at the low pressure fluid inlet 22 by means of pipe 70. It circulates among the strips 38 and exits the heat exchanger 50 at the low pressure fluid outlet 24. During its flow through the low pressure region 46 in the cylindrical shell 12 the fluid gave up heat to the strips 38 and the cold CO₂ flowing through the micro channels 40. As previously stated, the flow of the fluid through the low pressure region 46 is opposite to the direction of the flow of the CO₂ through the strips. The cold fluid is transported to the pump 68 via pipe 72. The pump 68 provides sufficient force to pump the fluid through the closed loop system. The fluid is pumped to the heat exchanger or evaporator 66 where the fan blows air over coils or fins that remove heat from the air to provide the cool air to the environment to be cooled. The pump 68 provides low, but sufficient pressure to keep the fluid flowing through the cool liquid loop. The first and second heat exchanger 48, 50 may be located close to one another and close to the high pressure compressor 52, but will be located outside of the building for safety purposes in the event of a rupture of the high pressure system's components. Instead of a high pressure armored line going through a house, all that is required is a simple low pressure water line from the first and second heat exchangers 48, 50 to the hot water heat exchanger 54 and the evaporator or cold fluid heat exchanger 66. Inside of the building, the heated or cooled low pressure fluid flows into a heat conducting coil located within a second enclosure. One can readily appreciate that the heated or cooled liquid can be used for a multitude of purposes such as previously described or for other applications such as a heat pump. Another embodiment is illustrated in Fig. 8. This embodiment is similar to the embodiment illustrated in Fig. 7. However the high pressure compressor 52 is replaced with a compressor/expansion engine such as illustrated in PCT Patent Application No. PCT/US2006/030759 filed August 8, 2006 incorporated herein by reference. Another similar compressor/expansion engine that can serve as the compressor is an axial device in which the barrel is held stationary and the pistons are driven by a rotating wedge. This embodiment also does not use the expansion valve 62 due to the operation of the compression/expansion engine as described herein. Fig. 8 illustrates a hot liquid loop for a heat pump or hot water heater and a cool liquid loop for air conditioning using a compressor/engine 74. The compressor cylinders 76 and compressor pistons 77 compress the gas, which is preferably CO₂ to a high pressure, approximately 1200-1800 psi, with the compression raising the temperature of the gas to a high temperature. The high pressure high temperature gas is discharged from the compressor/expansion engine 74 through a compressor discharge port 80 into a pipe 82. The high pressure gas then enters and passes through the first heat exchanger 48 that cools the gas as it passes through micro channels 40. The cooled gas, still at a high pressure, is discharged through the high pressure fluid outlet 20 into a discharge pipe 84. The high pressure cooled gas is then directed back to the compressor/engine 74 where it is received through a high pressure gas expansion engine inlet 86. The cooled gas at high pressure is received in the expansion cylinder 78 where it is received in the form of positive fluid pressure which helps drive expansion piston 79 which imparts energy to the compressor/engine 74. The gas is cooled further as a result of its expansion in the expansion cylinder 78. It is then discharged from the expansion cylinder 78 through a gas outlet port 88 into a pipe 90. The gas then flows into the second heat exchanger 50 as cold gas at a low pressure of about 500 psi but can be as low as 200 psi. The cold gas passes through the second heat exchanger 50 where it removes heat from the cool liquid in the cold liquid loop as previously described in the description of the embodiment of Fig. 7. The cool low pressure gas exits the second heat exchanger 50 and enters pipe 92 which returns the gas to a compressor inlet port 94. From here, the gas enters the compressor cylinder 76 where the cycle is repeated. In another application, the invention is used as a heating or air conditioning system for a vehicle. The compressors are powered by direct current from the vehicle's power system. Similar to the embodiment used in a building, the preferred high pressure fluid is carbon dioxide gas. Additionally, the preferred low pressure fluid is a water/glycol mixture. In this configuration, the invention's high pressure cylinders may be located away from one another and from both the high and low pressure cycle pumps. Because these components do not have to be in close proximity, the high pressure tanks can be safely enclosed in the event of an accident. Furthermore, the spacing options of the system allow the vehicle's designers to have greater design flexibility and choice when determining the locations of other components in the overall vehicle. Once heated or cooled, the low pressure fluid flows through a coil. A fan forces air across the coil, causing the air to be heated or cooled. This air is then fed through a duct, allowing it to be distributed to different locations within the vehicle. In another embodiment, the invention is used to heat or cool a liquid to be used in an unrelated process. The preferred high pressure fluid in this embodiment is carbon dioxide gas. The preferred low pressure fluid is oil, molten plastic, some type of food product, or some other material that must be brought to a specific temperature for a given device's use. In this embodiment, the device performing the unrelated process is connected directly to the low pressure inlet 24 and the low pressure outlet 22. Because the low pressure loop has such a small pressure differential, additional material from the unrelated process can be added by a storage unit located within the auxiliary device. Additionally, the auxiliary device can be wired to the high and low pressure pumps and can adjust the speed of the refrigeration cycle in order to control the temperature of the low pressure fluid. Furthermore, allowing the auxiliary device to control the invention's pumps will enable it to regulate the feed rate of the low pressure fluid. It should be noted that both the number and spacing of the micro channel strips 38 will vary among different embodiments and configurations of the invention. The greater the heat exchange required for the particular application, the greater the number of micro channel strips 38 will be present within the appropriate tank. It should also be noted that the size and configuration of the plastic filler pieces 44 will be adjusted to regulate the flow of the low pressure fluid. If the plastic filler pieces 44 are larger in volume, more of the low pressure fluid will come into direct contact with the micro channel strips 38. This produces a fluid from the outlet that has a greater temperature differential relative to the inlet fluid than would the same device with a smaller volume of filler. It should be noted that in all embodiments the change from heating to cooling does not require reversing valves which switch the flow of the high pressure working gas through the compressor — a common focus of compressor failure in current heat pump systems. Rather, only the low pressure water/glycol transport fluid needs to be switched while the CO2 refrigeration cycle configuration remains untouched.

Claims

V. CLAIMS

What is claimed is: 1. A heat exchanger comprising: A vessel having opposite ends, a high pressure inlet at one end for receiving a first fluid refrigerant at a first high pressure, a high pressure outlet at an opposite end for discharging the first fluid refrigerant, a central low pressure chamber within the vessel between the high pressure inlet and the high pressure outlet, the central chamber having an inlet end and an outlet end, at least one heat exchange tube having an inlet end and an outlet end, the inlet end in fluid communication with the high pressure inlet and the outlet end in fluid communication with the high pressure outlet, the heat exchange tube defining a high pressure fluid passageway from the high pressure inlet to the high pressure outlet through the central low pressure chamber, a low pressure inlet at the inlet end of the central low pressure chamber for receiving a second fluid refrigerant at a second pressure that is lower than the first high pressure, a low pressure outlet at the outlet end of the central low pressure chamber for discharging the second fluid refrigerant after it flows through the central low pressure chamber, a low pressure fluid passageway formed in the central low pressure chamber between the low pressure inlet and the low pressure outlet, whereby the high pressure fluid passageway and the low pressure fluid passageway are maintained separate from each other so that the first fluid refrigerant in the high pressure fluid passageway does not mix with the low pressure fluid refrigerant in the low pressure fluid passageway but heat transfer between the fluid refrigerants occurs through heat conduction of the heat exchange tube.

2. The heat exchanger of claim 1 wherein the first fluid refrigerant flows through the heat exchange tube in a first direction from the high pressure inlet to the high pressure outlet, and the liquid refrigerant flows in the low pressure fluid passageway from the low pressμre inlet to the low pressure outlet in a second direction opposite the flow of the fluid in the heat exchange tube.

3. The heat exchanger of claim 1 wherein the heat exchange tube has a plurality of fluid flow channels therein.

4. The heat exchanger of claim 3 and further comprising a plurality of heat exchange tubes.

5. The heat exchanger of claim 4 and further comprising a first high pressure dividing plate mounted in the vessel at the high pressure inlet end and spaced apart from the high pressure inlet forming a first high pressure chamber, a second high pressure dividing plate mounted in the vessel at the high pressure outlet end and spaced apart from the high pressure outlet forming a second high pressure chamber, the two high pressure chambers separated by the central low pressure chamber.

6. The heat exchanger of claim 5 wherein each of the plurality of heat exchange tubes have their inlet end passing through the first high pressure dividing plate and their outlet end passing through the second high pressure dividing plate.

7. The heat exchanger of claim 1 wherein the first fluid refrigerant is carbon dioxide and the first high pressure is between 200 psi and 2500 psi.

8. The heat exchanger of claim 1 wherein the second fluid refrigerant is a solution of water and glycol.

9. The heat exchanger of claim 1 wherein the second pressure is between 1 and_.50 psi.

10. A heat exchanger comprising: a vessel having opposite ends, a high pressure inlet at one end of the vessel for receiving a first fluid refrigerant at a first high pressure, an inlet high pressure chamber at the one end of the vessel in fluid communication with the high pressure inlet, a high pressure outlet at the opposite end of the vessel for discharging the fluid, an outlet high pressure chamber at the opposite end of the vessel in fluid communication with the high pressure outlet, a low pressure chamber disposed between the inlet high pressure chamber and the outlet high pressure chamber, at least one heat exchange tube having a fluid refrigerant flow path therethrough with an opening inlet in fluid communication with the inlet high pressure chamber and an opening outlet in fluid communication with the outlet high pressure chamber, the heat exchange tube mounted in the low pressure chamber, a low pressure inlet in the low pressure chamber for receiving a second fluid refrigerant into the low pressure chamber, the refrigerant fluid contacting at least one heat exchange tube, a low pressure outlet in the low pressure chamber for discharging the second fluid refrigerant out from the low pressure chamber, the second fluid refrigerant transferring heat from the second fluid refrigerant to the heat exchange tube and to the first fluid refrigerant if the second fluid refrigerant is at a higher temperature than the first fluid refrigerant, or receiving heat from the first fluid refrigerant if the second fluid refrigerant is at a lower temperature than the first fluid refrigerant.

1 1. The heat exchanger of claim 10 wherein the first fluid refrigerant flows through the heat exchange tube in a first direction from the high pressure inlet to the high pressure outlet, and the second fluid refrigerant flows through the low pressure chamber from the low pressure inlet to the low pressure outlet in a second direction opposite the flow of the first fluid refrigernat in the heat exchange tube.

12. The heat exchanger of claim 10 wherein the heat exchange tube has a plurality of fluid flow channels therein.

13. The heat exchanger of claim 10 and further comprising a plurality of heat exchange tubes.

14. The heat exchanger of claim 10 wherein the fluid is carbon dioxide and the first high pressure is between 200 psi and 2500 psi.

15. The heat exchanger of claim 10 wherein the second fluid refrigerant is a solution of water and glycol.

16. The heat exchanger of claim 10 wherein the second pressure is between 1 and 50 psi.

17. A heat pump air conditioning system comprising: a compressor/expansion engine comprising a centrally mounted drive shaft, a cylinder barrel, at least one cylinder being a compressor cylinder with a compressor piston in driven relation to the drive shaft causing the piston to reciprocate when the drive shaft rotates, and having a first high pressure high temperature outlet for discharging a first fluid refrigerant at a first high pressure and temperature from the compressor/expansion engine and a first low pressure inlet, and at least one cylinder being an expansion cylinder with an expansion piston in driving relation to the drive shaft applying a force to assist rotation of the drive shaft and having a high pressure warm fluid temperature inlet for receiving a first fluid refrigerant at a second high pressure and warm temperature, means for controlling the flow of fluid at the second high pressure into the expansion cylinder and for controlling the output flow of the first fluid refrigerant at a second lower pressure from the expansion cylinder, a first heat exchanger/gas cooler means with a first high pressure hot fluid inlet and a second high pressure warm fluid outlet, a high pressure chamber for receiving the first fluid refrigerant at the high pressure hot fluid inlet, and a second high pressure chamber for discharging the first fluid refrigerant at the high pressure warm fluid outlet, a low pressure chamber disposed between the high pressure chambers, at least one heat exchange tube mounted in the low pressure chamber, the heat exchange tube having a refrigerant flow path therethrough with an open inlet in fluid communication with the high pressure chamber and an open outlet in fluid communication with the second high pressure chamber, a low pressure inlet for receiving a second fluid refrigerant into the low pressure chamber, a low pressure outlet for discharging the second fluid refrigerant out of the low pressure chamber, whereby the first fluid refrigerant is maintained in a separate flow passageway from the second fluid refrigerant, but allowing heat transfer between the first fluid refrigerant and the second fluid refrigerant, a second heat exchanger/heat absorber means with a second low pressure cold fluid inlet and a first low pressure cool fluid outlet, a first fluid passageway fluidly connecting the first high pressure high temperature outlet from the compressor cylinder to the high pressure hot fluid inlet of the first heat exchanger/gas cooler means, a second fluid passageway fluidly connecting the high pressure warm fluid outlet from the first heat exchanger/gas cooler means to the second high pressure warm temperature fluid inlet of the expansion cylinder, a third fluid passageway fluidly connecting the second low pressure outlet from the expansion cylinder to the second low pressure cold fluid inlet of the second heat exchanger/heat absorber means, and a fourth fluid passageway fluidly connecting the cool low pressure outlet from the second heat exchanger/heat absorber means to the first low pressure cold fluid inlet of the compressor cylinder.

18. The heat pump air conditioning system of claim 17 wherein the second heat exchanger/heat absorber means comprises a first high pressure cold fluid inlet and a second high pressure cool fluid outlet, a high pressure chamber for receiving the first fluid refrigerant at the high pressure cold fluid inlet, and a second high pressure chamber for receiving the first fluid refrigerant at the high pressure cool fluid outlet, a low pressure chamber disposed between the high pressure chambers, at least one heat exchange tube mounted in the low pressure chamber, the heat exchange tube having a refrigerant flow path therethrough with an open inlet in fluid communication with the high pressure chamber and an open outlet in fluid communication with the second high pressure chamber, a low pressure inlet for receiving the second fluid refrigerant into the low pressure chamber, a low pressure outlet for discharging the second fluid refrigerant out of the low pressure chamber, whereby the first fluid refrigerant is maintained in a separate flow passageway from the second fluid refrigerant, but allowing heat transfer between the first fluid refrigerant and the second fluid refrigerant.

19. A heat pump air conditioning system comprising: a compressor having a first high pressure high temperature outlet for discharging a first fluid refrigerant at a first high pressure and temperature from the compressor, a first low pressure inlet, a compressor fluid inlet for receiving the first fluid refrigerant at a lower pressure than the first high pressure, a first heat exchanger/gas cooler means with a first high pressure hot fluid inlet and a second high pressure warm fluid outlet, the first heat exchanger comprising a high pressure chamber for receiving the first fluid refrigerant at the first high pressure at a hot fluid inlet, and a second high pressure chamber for receiving the first fluid refrigerant at the first high pressure, a warm fluid outlet for discharging the first fluid refrigerant at a warm temperature, a low pressure chamber disposed between the high pressure chambers, at least one heat exchange tube mounted in the low pressure chamber, the heat exchange tube having a fluid flow path therethrough with an open inlet in fluid communication with the high pressure chamber and an open outlet in fluid communication with the second high pressure chamber for allowing the first fluid refrigerant at the first high pressure to flow from the high pressure chamber to the second high pressure chamber, a low pressure inlet for receiving a low pressure second fluid refrigerant into the low pressure chamber, a low pressure outlet for discharging the low pressure second fluid refrigerant out of the low pressure chamber, whereby the high pressure first fluid refrigerant is maintained in a separate flow passageway from the low pressure second fluid refrigerant, but allowing heat transfer between the high pressure first fluid refrigerant and the low pressure second fluid refrigerant, a first fluid passageway fluidly connecting the first high pressure high temperature outlet from the compressor to the first high pressure hot fluid inlet of the first heat exchanger/gas cooler means, a second fluid passageway fluidly connecting the warm fluid outlet from the first heat exchanger/gas cooler means to compressor fluid inlet, secondary heat exchanger means for utilization of the second refrigerant fluid in a heat exchange application, the secondary heat exchanger means having a second refrigerant fluid inlet and second refrigerant fluid outlet, the secondary heat exchanger means is located in a separate enclosure remote from the first heat exchanger/gas cooler means, a first low pressure second refrigerant fluid passageway fluidly connecting the low pressure outlet to the second refrigerant fluid inlet of the secondary heat exchanger means, a second low pressure second refrigerant fluid passageway fluidly connecting the second refrigerant fluid outlet to the low pressure inlet of the first heat exchanger/gas cooler means, a high pressure fluid pathway defined by the first fluid passageway, first high pressure hot fluid inlet, high pressure chamber, fluid flow path through the heat exchange tube, second high pressure chamber, warm fluid outlet and second fluid passageway, and a low pressure refrigerant fluid pathway defined by the low pressure inlet, low pressure chamber, a low pressure outlet, first low pressure refrigerant fluid passageway, second refrigerant fluid inlet, second heat exchanger means, second refrigerant fluid outlet, and second low pressure refrigerant fluid passageway, whereby the high pressure fluid passageway and the low pressure fluid passageway are maintained separate from each other so that the first fluid refrigerant in the high pressure fluid passageway does not mix with the low pressure fluid refrigerant in the low pressure fluid passageway but heat transfer between the fluid refrigerants occurs through heat conduction of the heat exchange tube.

20. The heat pump air conditioning system of claim 19 and further comprising: expansion valve means for receiving the warm fluid discharged from the warm fluid outlet from the first heat exchanger/gas cooler means and expanding and cooling the warn fluid, a third heat exchanger/heat absorber with a second high pressure warm fluid inlet to receive the first fluid refrigerant from the expansion valve means, and a second high pressure cool fluid outlet, the third heat exchanger comprising a third high pressure chamber for receiving the first fluid refrigerant at the second high pressure at a warm fluid inlet, and a fourth high pressure chamber for receiving the first fluid refrigerant at the second high pressure and a cool fluid outlet for discharging the first fluid refrigerant at a cool temperature, a second low pressure chamber disposed between the high pressure chambers, at least one second heat exchange tube mounted in the second low pressure chamber, the second heat exchange tube having a fluid flow path therethrough with an open inlet in fluid communication with the third high pressure chamber and an open outlet in fluid communication with the fourth high pressure chamber for allowing the first fluid refrigerant at the second high pressure to flow from the third high pressure chamber to the fourth high pressure chamber, a second low pressure inlet for receiving a second low pressure refrigerant fluid into the second low pressure chamber, a second low pressure outlet for discharging the second low pressure refrigerant fluid out of the second low pressure chamber, whereby the second high pressure fluid is maintained in a separate flow passageway from the second low pressure refrigerant, but allowing heat transfer between the second high pressure fluid and the second low pressure refrigerant, and fourth heat exchanger means for utilization of the second low pressure refrigerant fluid in a heat exchange application, the fourth heat exchanger means having a second refrigerant fluid inlet and outlet, the fourth heat exchanger means located in a separate enclosure than the third heat exchanger/gas cooler means.

21. The heat pump air conditioning system of claim 20 and further comprising a third low pressure refrigerant fluid passageway fluidly connecting the second low pressure outlet to the second refrigerant fluid inlet of the fourth heat exchanger means, a fourth low pressure refrigerant fluid passageway fluidly connecting the second refrigerant fluid outlet to the second low pressure inlet of the third heat exchanger/heat absorber.

22. The heat pump air conditioning system of claim 21 and further comprising a second high pressure fluid pathway defined by the first fluid passageway, first high pressure hot fluid inlet, high pressure chamber, fluid flow path through the heat exchange tube, second high pressure chamber, warm fluid outlet, expansion valve means, second high pressure warm fluid inlet, third high pressure chamber, second heat exchange tube, fourth high pressure chamber, cool fluid outlet and fourth low pressure refrigerant fluid passageway.

23. The heat pump air conditioning system of claim 22 and further comprising a second low pressure refrigerant fluid pathway defined by second the low pressure inlet, second low pressure chamber, a second low pressure outlet, second low pressure refrigerant fluid passageway, second refrigerant fluid inlet, fourth heat exchanger means, second refrigerant fluid outlet, and second low pressure refrigerant fluid passageway.

24. The heat pump air conditioning system of Claim 17 wherein the first fluid refrigerant is carbon dioxide.

25. The heat pump air conditioning system of Claim 24 wherein the second fluid refrigerant is a solution of water and glycol.