Two-stage compression heat pump system

Abstract

The utility model discloses a two-stage compression heat pump system which comprises a low-pressure machine, a high-pressure machine, a condenser, a throttling element, an evaporator, an enthalpy increasing module and a first one-way valve. An exhaust port of the high-pressure machine is sequentially connected with the condenser, the enthalpy increasing module, the throttling element, the evaporator and an air suction port of the low-pressure machine through pipelines; the enthalpy increasing module is connected to an air suction port of the high-pressure machine through a first pipeline, and the first one-way valve is arranged on the first pipeline. Through the simple structural design, the enthalpy increasing gas can be recycled through two-stage compression, the working efficiency is improved, and meanwhile the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat pump equipment, and particularly relates to a two-stage compression heat pump system. BACKGROUND

[0002] In the technical development of heat pump systems, as the core component of the system, the performance and configuration of the compressor directly affect the efficiency and reliability of the entire system. Tradically, in order to improve the refrigeration or heating capacity of the system, many heat pump systems adopt a design of one compressor equipped with multiple cylinders. Although this design improves the performance of the system to a certain extent, it is often restricted by factors such as compressor performance, size, cost, and supply stability. In particular, for single-machine two-stage compressors, the adjustment capacity is relatively limited, and it is difficult to meet the high-efficiency operation demand under different working conditions, which to some extent limits the flexibility and adaptability of the heat pump system.

[0003] In order to overcome these limitations, the use of series and parallel compressors has been explored. In the series configuration, the enthalpy-increasing gas supplement technology can improve the refrigeration efficiency of the system to a certain extent, especially in low-temperature environments. This configuration can significantly improve the performance of the system. However, when both compressors are non-enthalpy-increasing compressors, if the enthalpy-increasing gas needs to be recovered when both compressors are running, a complex system structure needs to be designed, and a complex control logic needs to be equipped, resulting in high production cost. CONTENT OF THE UTILITY MODEL

[0004] The purpose of the embodiments of the present application is to provide a two-stage compression heat pump system, which can recover enthalpy-increasing gas through simple structural design for two-stage compression, improve work efficiency, and reduce production cost.

[0005] To achieve the above purpose, the following technical solutions are adopted in the present application:

[0006] On the one hand, a two-stage compression heat pump system is provided, which comprises a low-pressure machine, a high-pressure machine, a condenser, a throttling component, an evaporator, an enthalpy-increasing module, and a first one-way valve. The low-pressure machine and the high-pressure machine are arranged in series. The exhaust port of the high-pressure machine is connected to the condenser, the enthalpy-increasing module, the throttling component, the evaporator, and the suction port of the low-pressure machine in sequence through a pipeline. The enthalpy-increasing module is connected to the suction port of the high-pressure machine through a first pipeline, and the first one-way valve is arranged in the first pipeline.

[0007] Further, the low-pressure machine is provided with an enthalpy-increasing structure, and the enthalpy-increasing structure and the enthalpy-increasing module are connected through a second pipeline. A control valve is arranged on the second pipeline.

[0008] Further, the control valve is configured to be closed when both the low-pressure compressor and the high-pressure compressor are in operation, and to be opened when only the low-pressure compressor is in operation.

[0009] Further, a three-way valve is further included, the three-way valve having a first valve port, a second valve port and a third valve port, the exhaust port of the low-pressure compressor being connected to the first valve port, the second valve port being connected to the condenser through a third pipeline, and the third valve port being connected to the suction port of the high-pressure compressor, and a second one-way valve being arranged on the third pipeline.

[0010] Further, an exhaust port of the high-pressure compressor is connected to the condenser through a fourth pipeline, and a third one-way valve is arranged on the fourth pipeline.

[0011] Further, a four-way valve is further included, four valve ports of the four-way valve being connected to the exhaust port of the high-pressure compressor, the condenser, the evaporator and the suction port of the low-pressure compressor through pipelines respectively.

[0012] Further, the low-pressure compressor is a variable frequency compressor, and the high-pressure compressor is a variable frequency compressor or a fixed frequency compressor.

[0013] Further, the enthalpy increasing module is a plate heat exchanger or a flash evaporator.

[0014] Further, the condenser is a fin heat exchanger or a water-side heat exchanger.

[0015] Further, the low-pressure compressor is an enthalpy increasing compressor or a non-enthalpy increasing compressor, and the high-pressure compressor is a non-enthalpy increasing compressor.

[0016] The beneficial effects of the present application are as follows: in the heating mode, ambient air is absorbed by the evaporator as a low-temperature heat source, the refrigerant evaporates and absorbs heat in the evaporator, and then is preliminarily compressed by the low-pressure compressor to increase the pressure and temperature. Subsequently, the refrigerant enters the high-pressure compressor for further compression to form high-pressure and high-temperature gas. These high-temperature and high-pressure gases then enter the condenser to release a large amount of heat to water in the condensation process, thereby heating and producing hot water, while the refrigerant itself condenses into a liquid state. In order to further enhance the heating efficiency, especially in low-temperature environments, the system is equipped with an enthalpy increasing module. When it is necessary to improve the heating capacity, the enthalpy increasing module supplements the intermediate pressure refrigerant (i.e. enthalpy increasing gas) to the suction port of the high-pressure compressor through the first pipeline and the first one-way valve. This design not only increases the flow of refrigerant sucked by the high-pressure compressor, but also increases the enthalpy value, thereby improving the heating efficiency of the entire system. The one-way valve ensures the one-way flow of the enthalpy increasing gas, avoiding unnecessary backflow and ensuring the efficient and stable operation of the system.

[0017] The scheme realizes simple recovery and reuse of the enthalpy-increasing gas through the ingenious application of series configuration and one-way valve, without complex system structure and control logic, greatly reducing the production cost and maintenance difficulty. In addition, the flexible control of the enthalpy-increasing module enables the system to automatically adjust the working mode according to the external environment and heating demand, further improving the flexibility and adaptability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0018] The application will be further described in detail below according to the drawings and embodiments.

[0019] Figure 1 System diagram of the two-stage compression heat pump system described in the embodiments of the application Figure 1 (two non-enthalpy-increasing compressors double-stage compression);

[0020] Figure 2 System diagram of the two-stage compression heat pump system described in the embodiments of the application Figure 2 (two non-enthalpy-increasing compressors single-stage compression);

[0021] Figure 3 System diagram of the two-stage compression heat pump system described in the embodiments of the application Figure 3 (enthalpy-increasing compressor + non-enthalpy-increasing compressor double-stage compression);

[0022] Figure 4 System diagram of the two-stage compression heat pump system described in the embodiments of the application Figure 4 (enthalpy-increasing compressor + non-enthalpy-increasing compressor single-stage compression).

[0023] In the figure: 1, low-pressure compressor; 2, high-pressure compressor; 3, condenser; 4, throttling device; 5, evaporator; 6, enthalpy-increasing module; 7, first one-way valve; 8, first pipeline; 9, enthalpy-increasing structure; 10, control valve; 11, three-way valve; 12, third pipeline; 13, second one-way valve; 14, fourth pipeline; 15, third one-way valve; 16, four-way valve; 17, gas-liquid separator; 18, second pipeline. DETAILED DESCRIPTION

[0024] To make the technical problems solved by the application, the technical solutions adopted and the technical effects reached more clear, the technical solutions of the embodiments of the application are further described in detail below. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0025] In the description of the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] In the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "above" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is higher in horizontal height than the second feature. The first feature "below", "below" and "below" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the first feature is lower in horizontal height than the second feature.

[0027] As shown in Figure 1 , Figure 2 The dashed line in the figure represents different refrigerants. The present embodiment provides a two-stage compression heat pump system, which comprises a low-pressure machine 1, a high-pressure machine 2, a condenser 3, a throttling device 4, an evaporator 5, an enthalpy-increasing module 6 and a first one-way valve 7. The low-pressure machine 1 and the high-pressure machine 2 are connected in series, and the exhaust port of the high-pressure machine 2 is connected to the condenser 3, the enthalpy-increasing module 6, the throttling device 4, the evaporator 5 and the suction port of the low-pressure machine 1 in sequence through a pipeline. The enthalpy-increasing module 6 is connected to the suction port of the high-pressure machine 2 through a first pipeline 8, and the first one-way valve 7 is arranged in the first pipeline 8.

[0028] The core components of the system include a low-pressure machine 1, a high-pressure machine 2, a heat-generating water condenser 3 in heating mode, a throttling device (such as an electronic expansion valve), an evaporator 5, an enthalpy-increasing auxiliary module and a one-way control valve 10. The low-pressure machine 1 and the high-pressure machine 2 are connected in series to build a two-stage compression architecture, wherein the exhaust end of the high-pressure machine 2 is connected in sequence to the heat-generating water condenser 3 in heating mode, the enthalpy-increasing auxiliary module, the throttling device, the evaporator 5 through a pipeline, and finally fed back to the suction end of the low-pressure machine 1, forming a closed heating cycle.

[0029] In heating mode, the system operates as follows: first start low-pressure machine 1, the refrigerant is compressed by low-pressure machine 1, then start high-pressure machine 2, and then the refrigerant enters high-pressure machine 2 for deeper compression, and is converted into high-pressure and high-temperature gaseous refrigerant. These high-pressure and high-temperature refrigerants release a large amount of heat energy in the heat water condenser 3, heating the circulating water, thereby producing hot water. After that, the refrigerant flows through the throttling device to reduce the pressure, becomes a low-temperature and low-pressure liquid and gas mixture, and enters the evaporator 5 again to absorb heat, and circulates repeatedly.

[0030] To further improve the heating efficiency, especially in low ambient temperature conditions, an enthalpy increasing auxiliary module is ingeniously designed and integrated into the system. When the heating capacity needs to be enhanced, the enthalpy increasing module 6 supplements the intermediate pressure refrigerant (i.e. enthalpy increasing gas) to the suction side of the high-pressure machine 2 through the first one-way valve 7, which not only increases the enthalpy of the refrigerant entering the high-pressure machine 2, but also increases the heating capacity of the system, ensuring the efficient and stable production of hot water. At the same time, the first one-way valve 7 ensures the one-way flow of the enthalpy increasing gas, preventing unnecessary backflow and maintaining the high efficiency of the system.

[0031] It is worth noting that the system also performs well in terms of simplified design. Through the precise application of series configuration and one-way valve, the simple recycling and reuse of enthalpy increasing gas is achieved, avoiding the introduction of complex system structure and cumbersome control logic, thereby reducing production cost and system maintenance difficulty. In addition, the flexible operation of the enthalpy increasing module 6 enables the system to automatically adjust the working mode according to the external environment temperature and hot water demand, improving the adaptability and operating efficiency of the system.

[0032] Among them, the low-pressure machine 1 is a variable frequency compressor, and the high-pressure machine 2 can be selected as a variable frequency compressor or a fixed frequency compressor according to actual needs. When both compressors need to be started, the low-pressure machine 1 is started first, and the high-pressure machine 2 is started after n seconds, where n is generally greater than 2. The reason for this setting is that if both are started at the same time, the low-pressure machine 1 will produce an overcurrent protection due to the aggregation of instantaneous voltage, resulting in a failed start. Moreover, if the high-pressure machine 2 is started first, and the suction of the high-pressure machine 2 is connected to the enthalpy increasing module, the enthalpy increasing module cannot guarantee that it is full of gas, which may cause liquid suction, and a large amount of liquid suction may damage the compressor.

[0033] Further, in order to realize the free switching between double-stage compression and single-stage compression, at least one three-way valve 11 is provided, the three-way valve 11 has a first valve port, a second valve port and a third valve port, the exhaust port of the low-pressure machine 1 is connected with the first valve port, the second valve port is connected with the condenser 3 through a third pipeline 12, the third valve port is connected with the suction port of the high-pressure machine 2, a second one-way valve 13 is arranged on the third pipeline 12, and the exhaust port of the high-pressure machine 2 is connected with the condenser 3 through a fourth pipeline 14, and a third one-way valve 15 is arranged on the fourth pipeline 14.

[0034] When the low-pressure machine 1 and the high-pressure machine 2 are connected in series and run at the same time (i.e. double-stage compression), the exhaust gas of the high-pressure machine 2 enters the condenser 3 to participate in the circulation through the third one-way valve 15, at this time the second one-way valve 13 does not work because the side of the second one-way valve 13 close to the low-pressure machine 1 is under pressure and the side connected to the exhaust port of the high-pressure machine 2 is under high pressure, so the refrigerant cannot pass through the second one-way valve 13; and only when the low-pressure machine 1 and the high-pressure machine 2 run at the same time, the enthalpy-increasing module 6 works, and the enthalpy-increasing gas enters the high-pressure machine 2 from the suction port through the first one-way valve 7. However, when only the low-pressure machine 1 is running (i.e. single-stage compression), the high-pressure machine 2 is bypassed by the second one-way valve 13, and the refrigerant discharged by the low-pressure machine 1 enters the condenser 3 to participate in the circulation through the second one-way valve 13, while the first one-way valve 7 is in a closed state and the refrigerant cannot pass through, and at the same time, in the case of only the low-pressure machine 1 being turned on, the enthalpy-increasing module 6 does not work and only acts as a throttling device.

[0035] It should be noted that single-stage compression is only the case of single low-pressure machine 1 being turned on, and there is no case of single high-pressure machine 2 being turned on, because if only the high-pressure machine 2 is turned on, the suction of the high-pressure machine 2 comes from the enthalpy-increasing module 6 and does not pass through the evaporator 5, so the refrigerant circulation cannot be formed.

[0036] In addition, the low-pressure machine 1 can be an enthalpy-increasing compressor or a non-enthalpy-increasing compressor, and the high-pressure machine 2 is a non-enthalpy-increasing compressor. In the above scheme, both the low-pressure machine 1 and the high-pressure machine 2 are non-enthalpy-increasing compressors. The following describes the scheme in which the low-pressure machine 1 is an enthalpy-increasing compressor and the high-pressure machine 2 is a non-enthalpy-increasing compressor.

[0037] Specifically, as shown in Figure 3 Figure 4 The low-pressure machine 1 is provided with an enthalpy-increasing structure 9, the enthalpy-increasing structure 9 is connected to the enthalpy-increasing module 6 through a second pipeline 18, and a control valve 10 is arranged on the second pipeline 18. The control valve 10 is configured to be closed when both the low-pressure machine 1 and the high-pressure machine 2 are turned on, and to be opened when only the low-pressure machine 1 is turned on.

[0038] In this scheme, when the low-pressure machine 1 and the high-pressure machine 2 are connected in series and run together, the control valve 10 is closed, and the enthalpy-increasing gas of the enthalpy-increasing module 6 enters the suction port of the high-pressure machine 2. The control valve 10 is closed because when the two-stage compression, the enthalpy-increasing pressure (i.e. the intermediate pressure) is only one, and is equal to the suction pressure of the high-pressure machine 2, while the enthalpy-increasing pressure of the low-pressure machine 1 is much smaller than the suction pressure of the high-pressure machine 2. If the control valve 10 is opened, the refrigerant (such as refrigerant) from the exhaust port of the low-pressure machine 1 will enter the enthalpy-increasing structure 9, which will damage the low-pressure machine 1. When only the low-pressure machine 1 is turned on, the control valve 10 is opened, and the enthalpy-increasing gas in the enthalpy-increasing module 6 enters the enthalpy-increasing structure 9 of the low-pressure machine 1 for air supplement.

[0039] ​It is particularly pointed out that in the preferred scheme, only the low-pressure machine 1 can be provided with the enthalpy-increasing structure 9, and if both the high-pressure machine 2 and the low-pressure machine 1 are provided with the enthalpy-increasing structure 9, the system will become very complex and the production cost will be greatly increased. It can also be understood that when only the low-pressure machine 1 is provided with the enthalpy-increasing structure 9, the system structure is relatively simple and clear, and the cost is relatively low.

[0040] Further, a four-way valve 16 is also included, and four valve ports of the four-way valve 16 are connected to the exhaust port of the high-pressure machine 2, the condenser 3, the evaporator 5, and the suction port of the low-pressure machine 1 through pipelines respectively. In the heating mode, the configuration of the internal passage of the four-way valve 16 enables the high-temperature and high-pressure refrigerant discharged by the high-pressure machine 2 to directly flow to the condenser 3 to release heat, and then, after being reduced in pressure by the throttling device 4, enters the evaporator 5 to absorb external heat, and is finally sucked into the low-pressure machine 1, completing the heating cycle. At this time, the four-way valve 16 ensures the correct flow direction of the refrigerant between the condenser 3 and the evaporator 5, ensuring the heating efficiency.

[0041] In the heat pump system, the selection of the enthalpy-increasing module 6 and the condenser 3 is crucial to the overall performance of the system. For the enthalpy-increasing module 6, a plate heat exchanger or a flash evaporator can be selected as the implementation way. Similarly, the condenser 3 also has at least two optional types of fin heat exchanger and water-side heat exchanger.

[0042] The plate heat exchanger is favored for its high heat exchange capacity and compact structure design. In the heat pump system, the plate heat exchanger can effectively transfer the heat generated in the enthalpy-increasing process to the refrigerant, thereby improving the heating efficiency of the system. In addition, the maintenance of the plate heat exchanger is relatively simple, and it is easy to realize automatic control. The flash evaporator utilizes the phase change characteristics of the refrigerant under different pressures to achieve enthalpy-increasing. In a high-pressure environment, the refrigerant is compressed into a liquid state and stores energy. When the refrigerant enters the flash evaporator, due to the reduction in pressure, part of the liquid refrigerant will rapidly evaporate, thereby absorbing heat and increasing the enthalpy of the refrigerant. The flash evaporator is suitable for occasions that require higher enthalpy-increasing effect.

[0043] The fin heat exchanger is usually used in air source heat pump systems, and the fin structure increases the heat exchange area and improves the heat exchange efficiency. The fin heat exchanger has the advantages of simple structure, low cost, easy maintenance, etc., and is suitable for small and medium-sized heat pump systems. The water-side heat exchanger is mainly used in water source heat pump systems, and heat is transferred through water circulation. The water-side heat exchanger usually has a large heat exchange area and high heat exchange efficiency, and is suitable for occasions that require a large amount of hot water supply. In addition, the water-side heat exchanger can also realize seamless connection with the heating system, improving the overall energy efficiency of the system.

[0044] In general, the selection of the enthalpy increasing module 6 and the condenser 3 should be determined according to the specific needs and application scenarios of the heat pump system. By reasonably selecting different types of enthalpy increasing modules 6 and condensers 3, the performance of the heat pump system can be optimized, the heating efficiency can be improved, the operating cost can be reduced, and the different needs of users can be met.

[0045] It is worth mentioning that both the low-pressure machine 1 and the high-pressure machine 2 are equipped with gas-liquid separators 17, and an additional gas-liquid separator 17 is also provided on the side of the low-pressure machine 1, that is, the refrigerant passes through two gas-liquid separators 17 before returning to the suction port of the low-pressure machine 1, which is to cope with the case of large refrigerant injection volume.

[0046] At the same time, according to the actual design needs, a one-way valve bridge and a matching fluorine cold electronic control can be added to the above-mentioned heat pump system. The one-way valve bridge, as a device for controlling the flow direction of refrigerant, is cleverly arranged on the key path of refrigerant circulation to prevent backflow, optimize the circulation path and protect system components from damage. At the same time, the fluorine cold electronic control, as an electrical control system, realizes precise control, fault protection and energy optimization by monitoring and adjusting the temperature, pressure and other parameters of the system in real time. The combination of the two not only ensures that the heat pump system always operates in the best state, but also further improves the reliability, energy efficiency ratio and safety of the system.

[0047] In the description herein, it should be understood that the terms "up", "down", "left", "right", and the like orientation or position relationship are for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only used to distinguish in the description, and have no special meaning.

[0048] In the description of the present specification, the description referring to the terms "an embodiment", "an example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0049] In addition, it should be understood that although the present specification is described in terms of embodiments, each embodiment does not necessarily contain only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

[0050] The technical principles of the present application are described above in combination with specific embodiments. These descriptions are only for explaining the principles of the present application, and cannot be interpreted as limiting the protection scope of the present application in any way. Based on the explanations herein, other specific embodiments of the present application can be conceived by those skilled in the art without any creative effort, and these embodiments will all fall within the protection scope of the present application.

Claims

1. A two-stage compression heat pump system, characterized by, The application relates to a refrigeration system comprising a low-pressure compressor (1), a high-pressure compressor (2), a condenser (3), a throttling device (4), an evaporator (5), an enthalpy-increasing module (6) and a first one-way valve (7), wherein the low-pressure compressor (1) and the high-pressure compressor (2) are arranged in series, the exhaust port of the high-pressure compressor (2) is connected to the condenser (3), the enthalpy-increasing module (6), the throttling device (4), the evaporator (5) and the suction port of the low-pressure compressor (1) in sequence through pipelines, the enthalpy-increasing module (6) is connected to the suction port of the high-pressure compressor (2) through a first pipeline (8), and the first one-way valve (7) is arranged in the first pipeline (8). The low-pressure compressor (1) is provided with an enthalpy-increasing structure (9), the enthalpy-increasing structure (9) is connected to the enthalpy-increasing module (6) through a second pipeline (18), and a control valve (10) is arranged on the second pipeline (18).

2. The two-stage compression heat pump system of claim 1, wherein, The control valve (10) is configured to be closed when the low-pressure compressor (1) and the high-pressure compressor (2) are both in operation, and the control valve (10) is opened only when the low-pressure compressor (1) is in operation.

3. The two-stage compression heat pump system of claim 2, wherein, The application further comprises a three-way valve (11) having a first valve port, a second valve port and a third valve port, the exhaust port of the low-pressure compressor (1) is connected to the first valve port, the second valve port is connected to the condenser (3) through a third pipeline (12), the third valve port is connected to the suction port of the high-pressure compressor (2), and a second one-way valve (13) is arranged on the third pipeline (12).

4. A two-stage compression heat pump system according to any one of claims 1-3, characterized in that, The exhaust port of the high-pressure compressor (2) is connected to the condenser (3) through a fourth pipeline (14), and a third one-way valve (15) is arranged on the fourth pipeline (14).

5. The two-stage compression heat pump system of claim 4, wherein, The application further comprises a four-way valve (16), and four valve ports of the four-way valve (16) are respectively connected to the exhaust port of the high-pressure compressor (2), the condenser (3), the evaporator (5) and the suction port of the low-pressure compressor (1) through pipelines.

6. A two-stage compression heat pump system according to any one of claims 1-3, characterized in that, The low-pressure compressor (1) is a variable-frequency compressor, and the high-pressure compressor (2) is a variable-frequency compressor or a fixed-frequency compressor.

7. A two-stage compression heat pump system as set forth in any of claims 1-3, characterized in that, The enthalpy-increasing module (6) is a plate heat exchanger or a flash evaporator.

8. A two-stage compression heat pump system as set forth in any of claims 1-3, characterized in that, The condenser (3) is a fin heat exchanger or a water-side heat exchanger.

9. A two-stage compression heat pump system as set forth in any of claims 1-3, characterized in that, The low-pressure compressor (1) is an enthalpy-increasing compressor or a non-enthalpy-increasing compressor, and the high-pressure compressor (2) is a non-enthalpy-increasing compressor.

10. The two-stage compression heat pump system of claim 1, wherein, ​

Images