Jet and compression coupling refrigeration heat pump device driven by low-grade energy

Abstract

The utility model discloses an injection and compression coupling refrigeration heat pump device driven by low-grade energy, which relates to the technical field of cooling and heating equipment, and comprises a low-grade energy system and an injection and compression coupling refrigeration heat pump system, the low-grade energy system comprises a heater, a heat storage water tank and a generator; the injection and compression coupling refrigeration heat pump system comprises a generator, a condenser, an evaporator, a compressor, a gas-liquid separator, an ejector, a gas-gas ejector, a liquid-gas ejector, an enthalpy reducer, an expansion valve I, an expansion valve II, an expansion valve III and a working medium pump. Through the cooperation of the low-grade energy system and the injection and compression coupling refrigeration heat pump system, low-grade energy such as solar energy and the like can be fully utilized to improve the refrigeration performance of the system, so that the system can operate well when the system has solar energy or not, the application range of injection circulation is widened, and the remarkable energy-saving effect is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of cooling and heating equipment, and in particular to an injection and compression coupled refrigeration heat pump device driven by low-grade energy. Background Art

[0002] Air conditioning and refrigeration energy consumption is the main part of building energy consumption and building carbon emissions. Existing air conditioning and refrigeration technology is driven by electricity. However, my country's electricity energy mainly comes from coal combustion for power generation, but coal combustion will produce a large amount of carbon emissions. Therefore, in order to help achieve the goals of "carbon neutrality" and "carbon peak", the use of renewable energy and industrial waste heat to assist in driving air conditioning and refrigeration systems has become a trend in technological development.

[0003] The jet refrigeration system driven by low-grade energy such as solar energy has the advantages of less equipment, low system investment and maintenance cost. At the same time, the jet and compression coupled refrigeration heat pump system is more stable and reliable than the independent jet refrigeration system, and is also a major development direction of renewable energy refrigeration system.

[0004] Therefore, how to reasonably combine low-grade energy such as solar energy with the injection and compression coupled refrigeration heat pump system has become one of the urgent problems to be solved in the field of air conditioning and refrigeration. Utility Model Content

[0005] In order to reasonably combine low-grade energy such as solar energy with the injection and compression coupled refrigeration heat pump system, the utility model provides the following technical solutions:

[0006] The utility model provides an injection and compression coupled refrigeration heat pump device driven by low-grade energy, comprising a low-grade energy system and an injection and compression coupled refrigeration heat pump system;

[0007] The low-grade energy system comprises a heater, a hot water storage tank and a generator, wherein the heater and the hot water storage tank are connected to form a heating loop; the generator and the hot water storage tank are connected to form a generating loop;

[0008] The injection and compression coupled refrigeration heat pump system includes a gas-liquid separator, and the gas outlet pipeline of the gas-liquid separator is connected to the compressor and the condenser in sequence; the outlet pipeline of the condenser is divided into four routes, the first route is connected to the working fluid pump, the generator and the primary fluid inlet of the gas-to-gas injector in sequence, the second route is connected to the expansion valve III, the enthalpy reducer and the secondary fluid inlet of the gas-to-gas injector in sequence, and the outlet of the gas-to-gas injector is connected to the inlet of the condenser; the third route is connected to the primary fluid inlet of the liquid-to-gas injector, the fourth route is connected to the enthalpy reducer, the expansion valve I, the evaporator and the secondary fluid inlet of the liquid-to-gas injector in sequence, and the outlet of the liquid-to-gas injector is connected to the inlet of the gas-liquid separator; the liquid outlet pipeline of the gas-liquid separator is connected to the expansion valve II, the evaporator and the secondary fluid inlet of the liquid-to-gas injector in sequence.

[0009] By adopting the above technical scheme, the low-grade energy system and the injection and compression coupled refrigeration heat pump system cooperate with each other, which can effectively realize the switching between solar energy and waste heat energy, so that the system can operate well with or without solar energy, and the hot water storage tank can further improve the utilization rate of solar energy; at the same time, the injection and compression coupled refrigeration heat pump system can reduce the inlet enthalpy of the evaporator, increase the cooling capacity per unit mass of the refrigerant, and use the gas at the compressor outlet through the ejector to reduce the outlet pressure of the gas-to-gas ejector, improve the injection performance, avoid the over-compression loss of the compressor, effectively improve the refrigeration performance, broaden the applicable area of ​​the injection cycle, and achieve significant energy-saving effects.

[0010] Furthermore, the heater is a solar thermal collector.

[0011] Furthermore, the heater is a waste heat source.

[0012] Furthermore, the heater includes a solar collector and a waste heat source, the solar collector and the waste heat source are connected in parallel, a first valve is provided between the solar collector and the hot water storage tank, and a second valve is provided between the waste heat source and the hot water storage tank.

[0013] Through the above technical scheme, when solar energy is sufficient, the first valve is opened and the second valve is closed. At this time, the solar collector is used to heat the water in the hot water storage tank; when solar energy is insufficient, the second valve is opened and the first valve is closed. At this time, the waste heat source is used to heat the water in the hot water storage tank, and the two valves are switched alternately, so that the upper layer temperature of the water in the hot water storage tank reaches the temperature required for the generator to start the cycle, so that the system can operate with or without solar energy.

[0014] Furthermore, a circulating water pump is provided between the heater and the hot water storage tank, and a generating circulating water pump is provided between the hot water storage tank and the generator.

[0015] Through the above technical solution, the heating circuit and the generating circuit can provide power for the water circulation to ensure that the water can circulate stably in the system according to the set flow rate.

[0016] Furthermore, the input end of the circulating water pump is connected to the lower outlet of the hot water storage tank, and the output end is connected to the heater; the input end of the generating circulating water pump is connected to the upper outlet of the hot water storage tank, and the output end is connected to the upper inlet of the generator.

[0017] Furthermore, a drying filter is provided at the inlet of the compressor, and an oil separator is provided at the outlet of the compressor.

[0018] Through the above technical solution, the drying filter can prevent moisture or impurities from entering the compressor, and the oil separator can prevent the lubricating oil carried in the refrigerant gas at the compressor outlet from entering the system, ensuring the oil return of the compressor and realizing the normal operation of the system.

[0019] Furthermore, a liquid reservoir is provided at the outlet of the condenser.

[0020] Through the above technical solution, the accumulator can be used to store and balance the refrigerant to ensure the performance and stability of the refrigeration system, and can also help reduce the fluctuation and pressure change of the refrigerant, thereby improving the working efficiency of the system and extending the service life of the equipment.

[0021] Furthermore, the injection and compression coupled refrigeration heat pump system selects pure refrigerant or mixed refrigerant as the working fluid.

[0022] Through the above technical solution, the power consumption of the working fluid pump can be reduced and the thermodynamic performance and operational reliability of the system can be improved.

[0023] The beneficial effects of the utility model compared with the prior art are:

[0024] The utility model can effectively realize the switching between solar energy and waste heat energy through the cooperation of the low-grade energy system and the injection and compression coupled refrigeration heat pump system, so that the system can operate well with or without solar energy, and the hot water storage tank can further improve the utilization rate of solar energy; at the same time, the injection and compression coupled refrigeration heat pump system can reduce the inlet enthalpy of the evaporator, increase the refrigeration capacity per unit mass of the refrigerant, effectively improve the refrigeration performance, broaden the applicable area of ​​the injection cycle, and achieve a significant energy-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a working principle diagram of the low-grade energy-driven injection and compression coupled refrigeration heat pump device described in Example 1 of the utility model;

[0027] Figure 2 This is a working principle diagram of the low-grade energy driven injection and compression coupled refrigeration heat pump device described in Example 2 of the utility model;

[0028] Figure 3 This is a working principle diagram of the low-grade energy driven injection and compression coupled refrigeration heat pump device described in Example 3 of the utility model;

[0029] Among them: 1-generator, 2-condenser, 3-evaporator, 4-compressor, 5-gas-liquid separator, 6-ejector, 7-solar collector, 8-heat storage tank, 9-heat collection circulation water pump, 10-generation circulation water pump, 11-gas-gas ejector, 12-liquid-gas ejector, 13-enthalpy reducer, 14-expansion valve I, 15-expansion valve II, 16-expansion valve III, 17-working fluid pump, 18-waste heat source, 19-waste heat circulation water pump, 20-first valve, 21-second valve. DETAILED DESCRIPTION

[0030] In the description of the present utility model, it should be noted that the terminology nouns in the various embodiments, such as words indicating directions such as "upper", "lower", "front", "back", "left", "right", etc., are only for simplifying the description of the positional relationship based on the drawings in the specification, and do not mean that the referred elements and devices must be operated according to the specific directions and specified operations and methods and structures in the specification. Such directional nouns do not constitute limitations on the present utility model.

[0031] In the description of the present invention, it should be noted that the terms "first", "second", "third" and "fourth" mentioned in the embodiments of the present invention are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", "third" and "fourth" may explicitly or implicitly include one or more of the features.

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Therefore, the following detailed description of the embodiments of the utility model provided in the drawings is not intended to limit the scope of the utility model for which protection is sought, but merely represents the selected embodiments of the utility model. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0033] The embodiment of the present application discloses an injection and compression coupled refrigeration heat pump device driven by low-grade energy, including a low-grade energy system and an injection and compression coupled refrigeration heat pump system.

[0034] Example 1

[0035] like Figure 1 As shown, in the embodiment of the present application, the heater is a solar thermal collector 7, the circulating water pump is a heat collecting circulating water pump 9, and the heating circuit is a solar thermal collecting circuit.

[0036] The low-grade energy system includes a solar collector 7, a heat storage tank 8, a heat collection circulating water pump 9, a generating circulating water pump 10 and a generator 1. The solar collector 7, the heat storage tank 8 and the heat collection circulating water pump 9 are connected in sequence to form a heating circuit; the generator 1, the heat storage tank 8 and the generating circulating water pump 10 are connected in sequence to form a generating circuit; wherein, the input end of the heat collection circulating water pump 9 is connected to the lower outlet of the heat storage tank 8, and the output end is connected to the solar collector 7; the input end of the generating circulating water pump 10 is connected to the upper outlet of the heat storage tank 8, and the output end is connected to the upper inlet of the generator 1.

[0037] When the water in the hot water tank 8 needs to be heated, the water in the hot water tank 8 enters the solar collector 7 for heating through the heat collection circulation water pump 9. When the solar energy is sufficient, the solar energy absorbed by the solar collector 7 can make the water temperature in the hot water tank 8 reach the temperature required by the generator 1. When the upper layer temperature of the water in the hot water tank 8 reaches the temperature required for the generator 1 to start the circulation, the circulation water pump 10 is turned on.

[0038] The injection and compression coupling refrigeration heat pump system comprises a gas-liquid separator 5, the gas outlet pipeline of the gas-liquid separator 5 is sequentially connected to the compressor 4, the ejector 6 and the condenser 2, a gas-gas ejector 11 is arranged between the generator 1 and the ejector 6, the outlet of the compressor 4 is connected to the first inlet of the ejector 6, the outlet of the gas-gas ejector 11 is connected to the second inlet of the ejector 6, the outlet of the ejector 6 is connected to the inlet of the condenser 2, and the outlet pipeline of the condenser 2 is divided into four routes, the first route is sequentially connected to the working fluid pump 17, the generator 1 and the primary fluid inlet of the gas-gas ejector 11, and the second route is sequentially connected to the expansion valve III 16, the secondary fluid inlet of the enthalpy reducer 13 and the gas-to-gas ejector 11, and the outlet of the gas-to-gas ejector 11 is connected to the inlet of the condenser 2; the third route is connected to the primary fluid inlet of the liquid-to-gas ejector 12, and the fourth route is sequentially connected to the enthalpy reducer 13, the expansion valve I14, the evaporator 3 and the secondary fluid inlet of the liquid-to-gas ejector 12, and the outlet of the liquid-to-gas ejector 12 is connected to the inlet of the gas-liquid separator 5; the liquid outlet pipeline of the gas-liquid separator 5 is sequentially connected to the secondary fluid inlet of the expansion valve II 15, the evaporator 3 and the liquid-to-gas ejector 12.

[0039] In this embodiment, a drying filter is provided at the inlet of the compressor 4 , and an oil separator is provided at the outlet of the compressor 4 .

[0040] The drying filter can prevent moisture or impurities from entering the compressor 4, and the oil separator can prevent the lubricating oil discharged from the compressor 4 together with the refrigerant from entering the system and affecting the normal operation of the system.

[0041] In this embodiment, a liquid reservoir is provided at the outlet of the condenser 2 .

[0042] The receiver can be used to store and balance the refrigerant to ensure the stability and performance of the refrigeration system, and can also help reduce the fluctuation and pressure changes of the refrigerant, thereby improving the working efficiency of the system and extending the service life of the equipment.

[0043] In this embodiment, a pure refrigerant or a mixed refrigerant can be selected as the working fluid in the injection and compression coupled refrigeration heat pump system.

[0044] Specifically, pure refrigerants can be R134a, R1234yf, R1234ze(E), etc., and mixed refrigerants can be R134a / R245fa, etc. According to different working conditions, efficient and stable refrigerants under corresponding working conditions can be used to improve the thermodynamic performance and operational reliability of the system.

[0045] In this embodiment, the expansion valve I 14, the expansion valve II 15, and the expansion valve III 16 are electronic expansion valves with adjustable opening or other valves capable of throttling and reducing pressure.

[0046] The opening of the electronic expansion valve is affected by the voltage and can be flexibly adjusted. The higher the voltage, the smaller the opening and the smaller the refrigerant flow through the expansion valve. Conversely, the larger the opening, the system can maintain a stable cooling effect and reduce energy consumption.

[0047] In this embodiment, the working fluid pump 17 is a plunger pump with continuously adjustable flow or other pumps with pressure-boosting capability.

[0048] The plunger pump has the advantages of high rated pressure, compact structure, high efficiency and convenient flow regulation, and can adjust the working fluid flow in real time according to system requirements.

[0049] The specific workflow of this embodiment is as follows:

[0050] When the temperature of the upper layer of the hot water storage tank 8 reaches the temperature required by the generator 1, the refrigerant in the generator 1 absorbs the heat of the hot water and becomes high-temperature and high-pressure saturated steam, and then enters the gas-gas ejector 11 to expand and reduce the pressure, thereby inhaling the low-pressure steam generated by the enthalpy reducer 13. The two fluids are mixed and pressurized, then leave the gas-gas ejector 11, enter the ejector 6, and after being ejected by the high-temperature and high-pressure steam from the compressor 4, the two are mixed and enter the condenser 2 together. The condensed liquid refrigerant flows out from the outlet pipeline of the condenser 2 and is divided into four paths. The first path is pressurized by the working fluid pump 17 and returns to the generator 1 for evaporation; the second path passes through the expansion valve III 16 and enters the enthalpy reducer 13 to evaporate and absorb heat, and then is inhaled by the gas-gas ejector 11; the third path returns to the gas-liquid separator 5 through the liquid-gas ejector 12; the fourth path reduces the enthalpy through the enthalpy reducer 13, is throttled by the expansion valve I 14, and then enters the evaporator 3 to evaporate and absorb heat.

[0051] The gas-liquid separator 5 is connected with two outlet pipelines, wherein the gaseous refrigerant in the gaseous outlet pipeline is sucked into the compressor 4, compressed, and then heated and pressurized to become high-temperature and high-pressure steam, and enters the ejector 6, ejecting the steam from the outlet of the gas-to-gas ejector 11, and the two are mixed and enter the condenser 2; the fluid in the liquid outlet pipeline of the gas-liquid separator 5 passes through the expansion valve II 15, and then is mixed with the fluid passing through the expansion valve I14 and enters the evaporator 3, and the gaseous refrigerant after evaporation and heat absorption in the evaporator 3 enters the secondary fluid inlet of the liquid-to-gas ejector 12, and then is mixed with the primary fluid entering from the primary fluid inlet and pressurized and enters the gas-liquid separator 5, completing the cycle.

[0052] Example 2

[0053] The difference between this embodiment and embodiment 1 is that: Figure 2 As shown, the heater is the waste heat source 18, the circulating water pump is the waste heat circulating water pump 19, and the heating circuit is the waste heat circuit.

[0054] The injection and compression coupled refrigeration heat pump system can be driven not only by solar energy, but also by waste heat; when using waste heat source 18 for heating, the water in the hot water storage tank 8 enters the waste heat source 18 for heating through the waste heat circulation water pump 19, and the hot water heated by the waste heat source 18 enters the hot water storage tank 8. The hot water on the upper layer of the hot water storage tank 8 is sent to the generator 1 by the generator pump 10 to heat the refrigerant therein, and the water after heat release and cooling enters the bottom of the hot water storage tank 8. After that, the hot water with low temperature at the bottom of the hot water storage tank 8 returns to the waste heat source 18 through the waste heat circulation water pump 19, is heated, and then enters the upper part of the evaporation water tank 8. When the water temperature in the hot water storage tank 8 reaches the required temperature of the generator 1, the injection and compression coupled refrigeration heat pump system is started.

[0055] The connection relationship between the components in the low-grade energy system and the injection and compression coupled refrigeration heat pump system is the same as that in Example 1, so the above connection relationship will not be repeated; for the injection and compression coupled refrigeration heat pump system, its cycle process is the same as that in Example 1, so the above implementation method will not be repeated.

[0056] Example 3

[0057] The difference between this embodiment and embodiment 1 is that: Figure 3 As shown, the heater also includes a waste heat source 18, wherein the waste heat source 18 is connected in parallel with the solar collector 7, a first valve 20 is arranged between the solar collector 7 and the hot water storage tank 8, and a second valve 21 is arranged between the waste heat source 18 and the hot water storage tank 8.

[0058] When there is sufficient solar energy, the first valve 20 is opened and the second valve 21 is closed. At this time, the solar collector 7 is used to heat the water in the hot water tank 8; when there is insufficient solar energy, the second valve 21 is opened and the first valve 20 is closed. At this time, the waste heat source 18 is used to heat the water in the hot water tank 8, and the switching is alternated so that the upper layer temperature of the water in the hot water tank 8 reaches the temperature required for the generator 1 to start the cycle, so that the system can operate well with or without solar energy.

[0059] In the embodiment of the present application, the opening and closing of the first valve 20 and the second valve 21 are manually controlled or automatically controlled.

[0060] Manual control allows the operator to directly control the opening and closing of the valve without being restricted by external conditions or equipment, and the operation is relatively simple and intuitive; automatic control can automatically adjust the state of the valve according to preset conditions or parameters, reducing manual intervention and improving the convenience and efficiency of operation.

[0061] The connection relationship between the components in the low-grade energy system and the injection and compression coupled refrigeration heat pump system is the same as that in Examples 1 and 2, so the above connection relationship will not be repeated; for the low-grade energy system and the injection and compression coupled refrigeration heat pump system, the cycle process is the same as that in Examples 1 and 2, so the above implementation methods will not be repeated.

[0062] It can be seen that the utility model can effectively realize the switching between solar energy and waste heat energy through the cooperation of the low-grade energy system and the injection and compression coupled refrigeration heat pump system, so that the system can operate well with or without solar energy, and the hot water storage tank 8 can further improve the utilization rate of solar energy; at the same time, the injection and compression coupled refrigeration heat pump system can reduce the inlet enthalpy of the evaporator 3, increase the refrigeration capacity per unit mass of the refrigerant, effectively improve the refrigeration performance, broaden the applicable area of ​​the injection cycle, and achieve a significant energy-saving effect.

[0063] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is limited by the attached claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

[0064] The utility model uses specific examples to illustrate the principle and implementation of the utility model. The above is only the preferred implementation of the utility model and is not used to limit the utility model. For those skilled in the art, the utility model can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made to it without departing from the principle and spirit of the utility model shall be included in the protection scope of the utility model.

Claims

1. A low-grade energy-driven injection and compression coupled refrigeration heat pump device, characterized in that: Includes low-grade energy system and injection and compression coupled refrigeration heat pump system; The low-grade energy system comprises a heater, a hot water storage tank (8) and a generator (1), wherein the heater and the hot water storage tank (8) are connected to form a heating circuit; the generator (1) and the hot water storage tank (8) are connected to form a generating circuit; The injection and compression coupled refrigeration heat pump system comprises a gas-liquid separator (5), wherein the gas outlet pipeline of the gas-liquid separator (5) is sequentially connected to the compressor (4), the first inlet of the ejector (6), the outlet of the ejector (6) and the condenser (2); the outlet pipeline of the condenser (2) is divided into four routes, wherein the first route is sequentially connected to the working fluid pump (17), the generator (1) and the primary fluid inlet of the gas-to-gas ejector (11); the second route is sequentially connected to the expansion valve III (16), the enthalpy reducer (13) and the secondary fluid inlet of the gas-to-gas ejector (11); and the outlet of the gas-to-gas ejector (11) is sequentially connected to the secondary fluid inlet of the gas-to-gas ejector (11). The second inlet of the ejector (6), the outlet of the ejector (6) and the inlet of the condenser (2) are connected in sequence; the third line is connected to the primary fluid inlet of the liquid-gas ejector (12); the fourth line is connected in sequence to the enthalpy reducer (13), the expansion valve I (14), the evaporator (3) and the secondary fluid inlet of the liquid-gas ejector (12); the outlet of the liquid-gas ejector (12) is connected to the inlet of the gas-liquid separator (5); the liquid outlet pipeline of the gas-liquid separator (5) is connected in sequence to the expansion valve II (15), the evaporator (3) and the secondary fluid inlet of the liquid-gas ejector (12).

2. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to claim 1, characterized in that: The heater is a solar thermal collector (7).

3. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to claim 1, characterized in that: The heater is a waste heat source (18).

4. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to claim 1, characterized in that: The heater comprises a solar thermal collector (7) and a waste heat source (18), wherein the solar thermal collector (7) and the waste heat source (18) are connected in parallel, a first valve (20) is provided between the solar thermal collector (7) and the hot water storage tank (8), and a second valve (21) is provided between the waste heat source (18) and the hot water storage tank (8).

5. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to any one of claims 2 to 4, characterized in that: A circulating water pump is provided between the heater and the hot water storage tank (8), and a generating circulating water pump (10) is provided between the hot water storage tank (8) and the generator (1).

6. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to claim 5, characterized in that: The input end of the circulating water pump is connected to the lower outlet of the hot water storage tank (8), and the output end is connected to the heater; the input end of the generating circulating water pump (10) is connected to the upper outlet of the hot water storage tank (8), and the output end is connected to the upper inlet of the generator (1).

7. The low-grade energy driven injection and compression coupled refrigeration heat pump device according to claim 1, characterized in that: The inlet of the compressor (4) is provided with a drying filter, and the outlet of the compressor (4) is provided with an oil separator.

8. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to claim 1, characterized in that: The outlet of the condenser (2) is provided with a liquid storage tank.

9. The low-grade energy-driven injection and compression coupled refrigeration heat pump device according to claim 1, characterized in that: The injection and compression coupled refrigeration heat pump system selects pure refrigerant or mixed refrigerant as the working fluid.

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