HK1169160A - Transcritical thermally activated cooling, heating and refrigerating system - Google Patents

Description

Transcritical thermally activated cooling, heating and refrigeration system

Cross Reference to Related Applications

The present disclosure is related to co-pending U.S. application 07/18958, which is assigned to the assignee of the present disclosure.

This application claims priority AND benefit to U.S. provisional application 61/173776, filed on 29.4.2009 AND entitled "TRANSCRITICAL THERMALLY ACTIVATED COOLING, filing AND regenerative SYSTEM," the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates generally to vapor compression systems and, more particularly, to combined vapor compression and vapor expansion systems.

Background

It is known to combine a vapor compression system with a vapor expansion (i.e., rankine cycle) system. See, for example, U.S. patent 6962056 (which is assigned to the assignee of the present invention) and U.S. patent 5761921.

Us patent 5761921 generates power in a rankine cycle that is then applied to drive the compressor of a vapor compression cycle, and the combined system operates on three pressure levels, namely the boiler, condenser and evaporator pressure levels. A common refrigerant R-134 is used in the vapor compression rankine cycle system. Such combined systems typically do not allow the use of transcritical refrigerants because transcritical systems typically do not have a condenser (but only a gas cooler), and thus no liquid refrigerant is available downstream of the gas cooler for pumping through the rankine circuit. The expander requires a high inlet pressure, but the high inlet pressure increases the boiling temperature and the exit temperature of the heating fluid carrying the thermal power. The increased leaving temperature results in a reduced degree of waste heat utilization. For these reasons, the systems do not fully utilize the available thermal energy, and thus have a low level of thermodynamic efficiency. In addition, they do not provide adequate performance below 180 ° f of the available heat source.

Us patent application 07/18958 provides a combined flow of refrigerant from two systems at the discharge of the compressor and expander, respectively. Further, a suction accumulator is provided so that liquid refrigerant is always available to the pump of the rankine cycle system so that transcritical operation can be performed. However, the use of such a suction accumulator may be undesirable because a larger pump is required and higher power is required. The pump power is determined by the product of the pressure difference across the pump and the specific volume of refrigerant flow at the pump inlet. Despite the low specific volume of the liquid in the suction accumulator, the pump may still need to operate at high pressure differentials. When the disadvantages of increased pressure differential outweigh the advantages of reduced liquid specific volume, it is considered advantageous to feed the pump with liquid refrigerant from the condenser rather than using a suction accumulator.

Disclosure of Invention

Briefly, in accordance with one aspect of the present disclosure, a combined vapor pressure and vapor expansion system uses a common refrigerant that enables a supercritical high pressure portion and a subcritical low pressure portion of a vapor expansion circuit, and combines refrigerant from an expander discharge and from a compressor discharge at an inlet of an outdoor heat exchanger. The outdoor heat exchanger is sized and designed so that the refrigerant discharged therefrom is always in liquid form so that it can flow directly to the pump of the vapor expansion circuit. The pump and expander are sized and designed so that the high pressure portion of the vapor expansion circuit is always supercritical.

According to another aspect of the present disclosure, the outdoor heat exchanger includes a cooling tower to ensure that the refrigerant is converted to liquid in the heat exchanger.

In accordance with another aspect of the disclosure, a liquid-to-suction heat exchanger is provided between the outdoor heat exchanger and the pump to increase subcooling and refrigerant density before the refrigerant liquid flows to the pump.

According to yet another aspect of the disclosure, a top heat exchanger is provided downstream of the expander outlet to regenerate the enthalpy of the hot stream.

According to yet another aspect of the present disclosure, the power generating vapor expansion circuit is used as a stand-alone system and generates electrical energy that can be used as a power source for different purposes, including driving a refrigeration system.

Drawings

These and objects of the invention will be further understood by reference to the following detailed description of the invention when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of a thermally activated refrigerant system used for cooling or heating only.

Fig. 2 is a schematic diagram of a temperature entropy (T-S) diagram of a process for thermally activating a refrigerant system for cooling or heating only.

Fig. 3A-3C are some schematic diagrams comparing slip (glide) in supercritical and subcritical applications, respectively.

FIG. 4 is a schematic view of a thermally activated vapor expansion system with multi-stage expansion.

FIG. 5 is a schematic of a temperature entropy (T-S) diagram of a process for a thermally activated vapor expansion system with multi-stage expansion.

Fig. 6 is a schematic diagram of a thermally activated refrigerant system providing air conditioning and refrigeration.

Fig. 7 is a schematic diagram of a thermally activated heat pump having two expansion devices.

Fig. 8 is a schematic diagram of a thermally activated heat pump having a bi-directional expansion device.

Fig. 9A and 9B are schematic views of a diverter valve and check valve arrangement, respectively.

Fig. 10 is a schematic diagram of a thermally activated heat pump having two different heat sources.

Fig. 11 is a schematic diagram of a thermally activated heat pump with multi-stage compression.

Fig. 12 is a schematic diagram of a thermally activated heat pump with vapor-to-vapor ejector.

Fig. 13 is a schematic diagram of a thermally activated heat pump with a two-phase ejector.

Fig. 14 is a schematic diagram of a thermally activated heat pump with an economizing cycle.

Fig. 15 is a schematic diagram of a thermally activated heat pump having a two-phase expander.

Detailed Description

While the present disclosure has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the disclosure as defined by the claims.

In accordance with fig. 1, a thermally activated refrigerant system includes a vapor compression circuit 21 shown as a solid line and a vapor expansion circuit 22 shown as a dashed line. The vapour compression circuit 21 comprises a compressor 23, a condenser 24, a liquid-to-suction heat exchanger 26, an expansion device 27 and an evaporator 28. The vapor expansion loop 22 is comprised of a pump 29, a topping heat exchanger 31, a heater 32, an expander 33, and a condenser 24. The refrigerant vapor stream at the outlet from the compressor and the vapor refrigerant stream at the outlet from the expander are connected at the condenser inlet to provide a combined stream through the condenser 24. As shown, the refrigerant liquid flow at the condenser outlet, or at the outlet of the liquid-to-suction heat exchanger 26, splits into two flows: one fed to the pump and the other circulating through the components of the vapor compression circuit.

Thermally activated refrigerant systems have three pressure levels: heating pressure, heat rejection pressure level, and evaporation pressure. The heating pressure is the pump discharge pressure, the heat rejection pressure is the compressor or expander discharge, and the evaporating pressure is the compressor suction pressure. The heating and heat rejection pressures are the high and low pressures of the vapor expansion circuit. The heat rejection and evaporation pressures are the high and low pressures of the vapor compression circuit.

A common working fluid is used for both the vapor compression and vapor expansion circuits. The working fluid has the following characteristics: which provides supercritical operation for the high pressure portion of the vapor expansion circuit and subcritical operation for the low pressure portion of the vapor expansion circuit. Thus, the working fluid in the vapor expansion circuit at high pressure remains gaseous, but the working fluid in the condenser appears in the region to the left of the vapor dome and is liquefied. An example of such a working fluid is CO₂Or based on CO₂Mixtures of, e.g. CO₂And propane, and the like.

The heater 32 provides thermal contact between the heating medium and the pumped refrigerant flow. Typically, the heat source is waste heat, such as may be derived from fuel cells, solar devices, micro turbines, reciprocating engines, and the like. The pressure in the heater is supercritical, that is, above the critical pressure of the refrigerant. This provides an advantageous temperature glide compatible with the temperature glide phase of the heating medium shown in fig. 2. The heater 32 should be designed to provide equal heat capacity ratios of the two streams and so that the highest temperature difference occurs on each stream. The slip and equivalent heat capacity ratio provide a higher degree of waste heat utilization and high inlet expander temperatures, resulting in improved expander performance. If the heat source is not waste heat, then the heat capacity ratio does not need to be equal and the temperature glide provides a higher refrigerant temperature at the expander inlet, which improves the performance characteristics of the expander.

The condenser 24 provides thermal contact between the cooling medium and the combined refrigerant streams exiting the compressor 23 and the expander 33. The temperature of the cooling medium in the condenser 24 is always maintained below the refrigerant critical point to enable refrigerant condensation at the heat rejection pressure, liquid refrigerant being supplied to the pump 29.

During operation at higher ambient temperatures, the condenser 24 may be fed by a cooling tower 34 to ensure condensation of the refrigerant vapor. Another alternative is to use CO₂And propane, etc., to raise the critical point of the fluid sufficiently above the ambient temperature level to enable the condensation process to be effected at the heat rejection pressure.

The heating pressure in the heater 32 is controlled by the expander-to-pump capacity ratio, which is determined by the expander-to-pump speed ratio, the liquid refrigerant temperature at the pump inlet, and the vapor refrigerant condition at the expander inlet.

The liquid-to-suction heat exchanger 26 is optional. Which slightly subcools the liquid stream exiting the condenser 24 and substantially superheats the vapor stream exiting the evaporator 28. Subcooling reduces pump power due to the reduced refrigerant density at the pump inlet. Moreover, it increases the enthalpy difference across the evaporator 28 and enhances the evaporator effect. Superheat reduces the refrigerant density at the compressor inlet and reduces the compressor mass flow rate and evaporator capacity. The overheating effect is generally stronger and the overall effect is generally less favorable. Thus, the liquid-to-suction heat exchanger 26 is only used when some superheat is required at the compressor inlet.

The topping heat exchanger 31 substantially improves the thermodynamic efficiency of the system when the heat source temperature is high. When the heat source temperature is low, no top heat exchanger is required.

The power generated in the expander 33 may drive the compressor 23 and the pump 29. All three machines may be placed on the same shaft. An alternative is to couple the shaft with a power generator 36 to provide not only cooling or heating energy efficiency, but also electrical power. The expander 33 may be coupled only to the power generator, in which case the power generator 36 powers the compressor 23 and the pump 29. Additionally, optionally, it can generate supplemental electrical energy.

The vapor expansion circuit may be implemented as a separate power generation system. The power generated in the power generation system may be used to power a heat pump, an air conditioner, a refrigerator, or any other electrical device.

All components located on the same shaft may be covered by a semi-airtight or airtight housing to reduce the risk of leakage.

The pump 29 may be a variable speed device or a multi-speed device, or a constant speed device. The change in speed helps to meet the changing demands of refrigeration, air conditioning or heating.

Referring now to fig. 2, a T-S diagram of the vapor compression circuit 21 and the vapor expansion circuit 22 of fig. 1 is shown, in which points of interest are indicated by numerals 1-12. As will be seen, lines 9-10 represent the temperature increase and enthalpy increase that occurs as the working fluid passes through the heater 32. Also, it should be appreciated that alternate long and short dash lines 37 represent a T-S plot of the cooled heating fluid passing through the heater 32. As such, it is desirable to not only use heat source fluids having temperatures of 180 ° f or higher (as used in conventional systems), but also to enable the use of heat source fluids having temperatures below this level. This is achieved by using CO₂A "slip" or slope of the line 37 obtained as the working fluid is possible. This will be more clearly understood by reference to fig. 3A-3C.

A vapor expansion circuit is shown in fig. 3A and includes, in serial flow relationship, a pump 38, a topping heat exchanger 39, a heater 41, an expander 42, and a condenser 43.

FIG. 3B shows the circuit of FIG. 3A when operating in a supercritical mode (e.g., with CO)₂Refrigerant). The numbers 1-8 in fig. 3B correspond to the positions 1-8 in the diagram of fig. 3A. As will be seen, line 3-4 in FIG. 3B represents when CO is present₂The temperature and enthalpy increase upon passing through the heater 41, and the alternate long and short dash line 44 represents the T-S plot of the heated fluid being cooled. It will be appreciated that the "slip" or slope of the line is considerable.

In contrast, FIG. 3C shows the circuit of FIG. 3A when operating in a subcritical mode (e.g., using a different CO than CO)₂Refrigerant) in the refrigerant flow. At this point, it will be appreciated that,the slip/slope of line 46 is significantly less than the slip/slope of line 44 in fig. 3B. The vertical components of the two lines 44 and 46 (as indicated by arrowed lines 47 and 48) show the degree of waste heat utilization of the two alternatives of fig. 3B and 3C, respectively. As will be seen, line 47 extends further down than line 48, which in turn indicates that a heat source at a lower temperature (state 7) may be employed as long as the temperature in state 8 is lower than the temperature in state 7. Thus, temperatures below 180 ° f, such as 150 ° f, may be suitable.

Referring now to fig. 4, another embodiment is shown in which, unlike the single stage expander 33 shown in fig. 1, a two stage expander 49 is provided, along with a second heater 51. The second heater 51 receives heated fluid along line 52 and returns it to the point of heater 32 through line 53. The temperature of the heating fluid in heater 51 should be equal to the temperature of the point in heater 32 to which line 53 is attached. In operation, refrigerant flows from the heater 32 to the first stage of the two-stage expander 49, then through the second heater 51, after which it passes through the second stage of the two-stage expander 49, and then to the topping heat exchanger 31. The rest of the circuit is as described above. The effect of using the two-stage expander 49 and the second heater 51 is illustrated in the T-S diagram of fig. 5, in fig. 5, the numbers (1-14) indicate the positions indicated in fig. 4. It is known that the method of multi-stage expansion with reheating improves the expander efficiency and reduces the required pump power, thereby enabling the use of smaller pumps and reducing the use of pump power, thereby improving the overall efficiency of the system.

Fig. 6 shows another embodiment, in which a second vapour compression circuit 54 is provided in parallel with the vapour compression circuit 21. This enables the system to provide both air conditioning (e.g., via the second vapor-compression circuit 54) and refrigeration (e.g., via the vapor-compression circuit 21).

The second vapor compression circuit 54 includes a second expansion device 56, a second evaporator or indoor unit 57, and a second compressor 58. The refrigerant flow for this circuit originates upstream of the expansion device 27, and the discharge flow from the second compressor 58 is combined with the refrigerant flow from the topping heat exchanger 31, which is then combined with the flow from the discharge of the compressor 23. Thus, each vapor compression circuit 21 and 54 has its own compressor and evaporator unit, and all other components are shared between the two circuits. As will be seen, both compressors are powered by the expander 33.

If the condenser 24 is an outdoor unit and the evaporator 28 is an indoor unit, then the thermally activated refrigerant system produces cooling. If the condenser is an indoor unit and the evaporator is an outdoor unit, the thermally activated refrigerant system produces heating. To switch between the two modes of operation, one or more diverter or check valves may be provided as shown in fig. 7-15.

To allow the system to operate as a heat pump, a pair of reversing valves 59 and 61 are provided as shown in FIG. 7. Further, in addition to the expansion device 27 operable for a cooling mode, a second expansion device 62 is provided for a heating mode. Each expansion device 27 and 62 includes a bypass valve, i.e., valves 63 and 64, respectively, to allow operation in the cooling and heating modes, respectively. The expansion devices 27 and 62 are one-way expansion devices. To switch between the cooling and heating modes, the reversing valves 59 and 61 and the bypass valves 63 and 64 are all operated simultaneously.

A suction accumulator 66 may be provided to meet refrigerant charge requirements for cooling and heating operations. Also, the suction accumulator 66 provides charge management and capacity control, accumulating redundant amounts of liquid refrigerant.

Further, liquid may be provided to the suction heat exchanger 67 as indicated.

A variation of the system of fig. 7 is shown in fig. 8, wherein the two expansion devices are replaced by a single expansion device 68, the single expansion device 68 being designed for bi-directional use. Thus, when switching between cooling and heating modes, the single expansion device and the reversing valves 59 and 61 are all switched simultaneously.

In fig. 9A, the respective positions of the diverter valves 59 providing cooling or heating operation are shown. Therefore, in cooling, the refrigerant passes from the direction change valve 59 through the heat exchanger 67, the expansion device 27, and then flows to the indoor unit. Upon heating, the refrigerant passes from the direction change valve 59 through the heat exchanger 67, the expansion device 27, and then flows to the outdoor unit.

As will be seen in fig. 9B, instead of using the reversing valve described above, a check valve may be used to achieve the same function. Thus, unlike the direction valve, four check valves 71, 72, 73, and 74 are provided. In the cooling mode, the refrigerant passes through the check valve 71, the heat exchanger 67, the expansion device 27, and the check valve 73 to arrive at the indoor unit, and the check valves 72 and 74 are closed. In the operation of the heating mode, the check valves 71 and 73 are closed, and the refrigerant passes through the check valve 74, the heat exchanger 67, the expansion device 27, and the check valve 72, and then flows to the outdoor unit.

Fig. 10 represents the case when two heat sources (high temperature and low temperature sources) are available. The second heater 74 employs a high temperature source. The heater 32 employs a low temperature source.

Fig. 11 shows a further embodiment in which a multi-stage compressor 76 is provided. After passing through the first stage, the refrigerant passes through a gas cooler 77 and then through the second stage of the two-stage compressor 76 before flowing to the reversing valve 61 and the condenser 24. In this way, the overall compressor power is reduced, thereby improving the thermodynamic efficiency of the compression circuit and, therefore, of the overall system.

The embodiment of fig. 12 provides an ejector 78 for propelling the refrigerant vapor stream to the suction accumulator 66, thereby improving the thermodynamic efficiency of the vapor compression circuit and, therefore, the overall system. The ejector 78 is driven by high pressure flow along line 79 or alternatively from lines 81 or 82. In this particular embodiment, the liquid-to-suction heat exchanger 67 is the primary component. The heat exchanger 67 effects evaporation of the liquid portion of the refrigerant stream exiting the ejector 78.

The embodiment of fig. 13 shows a heat pump with an ejector 83, ejector 83 being driven by high pressure refrigerant from line 84 or alternatively from line 86. The bi-directional expansion device 87 may be replaced by two unidirectional expansion devices, one for the indoor unit and the other for the outdoor unit, as shown in fig. 7 above.

Ejectors are known to improve the performance characteristics of the vapor compression cycle. The combined vapor compression and vapor expansion cycle is improved with a better vapor compression cycle.

Fig. 14 shows an alternative embodiment that includes an economizer cycle that includes an economizer heat exchanger 88, an economizer expansion device 89, and an economizer port 91 leading to an intermediate stage of the compressor 23. A further alternative may be a multi-stage compressor with intermediate vapour cooling. The economized cycle is known to improve the performance characteristics of the vapor compression cycle. The combined vapor compression and vapor expansion cycle is improved with a better vapor compression cycle.

The embodiment of fig. 15 provides a two-phase expander 92 fluidly interconnected between the inlet of the pump 29 and the reversing valve 59, as shown. Its use tends to increase the cooling effect while recovering additional power to drive the cycle. This in turn reduces the required pump size and pump power.

While the present disclosure has been particularly shown and described with reference to the preferred embodiments as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the disclosure as defined by the claims.

Claims (32)

1. A thermally activated cooling system comprising:

a vapor compression circuit comprising, in serial flow relationship, a compressor, a first heat exchanger, an expansion device, and a second heat exchanger;

a vapor expansion circuit comprising, in serial flow relationship, a liquid refrigerant pump, a heater, an expander, and the first heat exchanger;

the vapor compression circuit and the vapor expansion circuit each having a common refrigerant circulating therethrough as a working fluid, wherein the refrigerant provides supercritical operation for a high pressure portion of the vapor expansion circuit and subcritical operation for a low pressure portion of the vapor expansion circuit;

the compressor having a suction inlet and a discharge outlet and the expander having an inlet and an outlet, and further wherein the expander outlet is fluidly connected to the discharge outlet to provide a combined flow for circulating a portion of the working fluid through the first heat exchanger and toward the liquid refrigerant pump, wherein the first heat exchanger is sized and designed such that the working fluid discharged therefrom is always in liquid form; and is

The liquid refrigerant pump and the expander are sized and designed such that the high pressure portion of the vapor expansion circuit is always supercritical.

2. A thermally activated cooling system as set forth in claim 1 wherein said common refrigerant is CO₂。

3. A thermally activated cooling system as set forth in claim 1 wherein said common refrigerant is CO₂And propane.

4. A thermally activated cooling system as set forth in claim 1 and including a topping heat exchanger for causing heat to flow from the expander discharge stream to the stream flowing to the heater.

5. A thermally activated cooling system as set forth in claim 1 and including a liquid to suction heat exchanger for causing heat to flow from said first heat exchanger discharge stream to said second heat exchanger discharge stream.

6. A thermally activated cooling system as set forth in claim 1 wherein said expander is a two-stage expander and further wherein a second heater is disposed between two stages of said two-stage expander.

7. A thermally activated cooling system as set forth in claim 1 and including a second vapor compression circuit in parallel with said vapor compression circuit, said second vapor compression circuit having its own expansion device, evaporator, and compressor fluidly interconnected to function with said first heat exchanger.

8. A thermally activated cooling system as set forth in claim 1 and including a plurality of valves for selectively causing said vapor pressure retraction circuit to function as a heat pump.

9. A thermally activated cooling system as set forth in claim 8 wherein said plurality of valves includes two expansion devices, one for said first heat exchanger and another for said second heat exchanger.

10. A thermally activated cooling system as set forth in claim 8 wherein said plurality of valves comprises a single bi-directional expansion device selectively operative to conduct a flow of refrigerant to said first or second heat exchanger.

11. A thermally activated cooling system as set forth in claim 8 wherein said plurality of valves includes a plurality of check valves selectively operable to conduct a flow of refrigerant to said first or second heat exchanger.

12. A thermally activated cooling system as set forth in claim 1 and including a second heater connected in serial flow relationship with said heater.

13. A thermally activated cooling system as set forth in claim 1 wherein said compressor comprises a multi-stage compressor and further comprising a gas cooler operatively connected between stages of said multi-stage compressor.

14. A thermally activated cooling system as set forth in claim 1 wherein said vapor compression circuit includes an ejector for urging the flow of refrigerant to said compressor.

15. A thermally activated cooling system as set forth in claim 14 and including a liquid to suction heat exchanger for causing heat to flow from said first heat exchanger discharge stream to said second heat exchanger discharge stream,

wherein the refrigerant flow for cooling effect is split into two portions, the ejector being powered by one portion of the refrigerant flow and ejecting another portion of the refrigerant flow, which is processed in the second heat exchanger and then in the liquid-to-suction heat exchanger.

16. A thermally activated cooling system as set forth in claim 14 wherein said vapor compression circuit includes a suction accumulator, a flow of refrigerant for cooling duty powering said ejector, discharging a liquid portion of said flow of refrigerant that is collected in said suction accumulator and processed in said second heat exchanger.

17. A thermally activated cooling system as set forth in claim 1 wherein said vapor compression circuit includes an economizer operatively connected thereto.

18. A thermally activated cooling system as set forth in claim 1 and including a two-phase expander fluidly interconnected between said first heat exchanger and said second heat exchanger.

19. A thermally activated cooling system as set forth in claim 1 wherein said expander, said liquid refrigerant pump, and said compressor have a common shaft.

20. A thermally activated cooling system as set forth in claim 1 wherein a power generator and said expander have a common shaft and said power generator powers said liquid refrigerant pump and said compressor.

21. A thermally activated cooling system as set forth in claim 1 wherein a power generator, said expander and said liquid refrigerant pump have a common shaft and said power generator powers said compressor.

22. A thermally activated cooling system as set forth in claim 1 wherein a power generator, said expander and said compressor have a common shaft and said power generator supplies said liquid refrigerant pump.

23. A thermally activated cooling system as set forth in claim 18 wherein said expander, said liquid refrigerant pump, and said compressor have a common hermetic housing.

24. A power generation vapor expansion circuit comprising a power generator and, in serial flow relationship, a liquid refrigerant pump, a heater, an expander and a heat exchanger;

circulating a refrigerant therethrough as a working fluid, wherein the refrigerant provides supercritical operation for a high pressure portion of the vapor expansion circuit and subcritical operation for a low pressure portion of the vapor expansion circuit;

the heat exchanger being sized and designed such that the working fluid discharged therefrom is always in liquid form; and is

The liquid refrigerant pump and the expander are sized and designed such that the high pressure portion of the vapor expansion circuit is always supercritical.

25. A power generation vapor expansion circuit as set forth in claim 24 wherein said refrigerant is CO₂。

26. A power generation vapor expansion circuit as set forth in claim 24 wherein said refrigerant is CO₂And propane.

27. A power generation vapor expansion circuit as set forth in claim 24 and including an overhead heat exchanger for causing heat to flow from the expander discharge stream to the stream flowing to the heater.

28. A power generation vapor expansion circuit as set forth in claim 24 wherein said expander is a two-stage expander and further wherein a second heater is disposed between two stages of said two-stage expander.

29. A power generation vapor expansion circuit as set forth in claim 24 and including a second heater connected in serial flow relationship with said heater.

30. A power generation vapor expansion circuit as set forth in claim 24 wherein said power generator, said expander and said liquid refrigerant pump have a common shaft.

31. A power generation vapor expansion circuit as set forth in claim 24 wherein said power generator, said expander and said liquid refrigerant pump have a common hermetic housing.

32. A power generation vapor expansion circuit as set forth in claim 24 wherein said power generator powers a refrigeration system.