Fresh air dehumidification heat pump system based on compressor series-parallel transformation step suction and exhaust

Abstract

The application relates to a fresh air dehumidification heat pump system based on a new compressor series-parallel transformation step suction and exhaust, a refrigerant circulation flow path comprising a first air inlet coil, a first throttling device, a supply air coil, a first check valve, a return air coil, an exhaust air coil, a first four-way reversing valve and a first compressor which are sequentially connected; further comprising a second four-way reversing valve, a second compressor, a second air inlet coil and a second throttling device which are sequentially connected; further comprising a second check valve which is connected in parallel to the two ends of the supply air coil and the first check valve; the transformation of the series-parallel relationship of the compressors in the cold / heat mode is realized through the first four-way reversing valve and the second four-way reversing valve, so that the step suction / step exhaust forms correspondingly. Compared with the prior art, the two four-way reversing valves are switched skillfully, the switching of the two compressors in series and parallel is completed in the refrigeration and heating modes, and the switching of the step suction and the step exhaust is further realized, so that the unit performance is improved.

Description

Technical Field

[0001] This invention relates to a fresh air dehumidification heat pump system, and more particularly to a fresh air dehumidification heat pump system based on a series-parallel compressor-based cascade intake and exhaust system. Background Technology

[0002] The fresh air dehumidification heat pump system delivers heat- and humidity-treated air into the room to ensure user comfort and health, efficiently dehumidifying the air while providing fresh outdoor air. As a cooling heat pump cycle system, it employs a cooling dehumidification method, first cooling the air to below its dew point temperature, and then causing condensation to achieve dehumidification. The sensible heat generated by lowering the air to the dew point temperature does not directly contribute to dehumidification itself; instead, it constitutes a significant proportion of the total cooling capacity, thus affecting the system's dehumidification performance.

[0003] One improvement approach is to introduce cascaded air intake into the system, which involves generating two different evaporation temperatures in the heat pump system to handle the sensible and latent heat loads of the fresh air respectively. This can increase the average evaporation pressure of the system and help improve the unit's energy efficiency.

[0004] The basic method for achieving cascaded suction and discharge is to use two compressors connected in parallel (such as the technical solution disclosed in patent CN 106225116 A), forming two different gradient evaporation temperatures. The circulation pressure ratio corresponding to the higher evaporation temperature is smaller, resulting in higher performance; however, the circulation pressure ratio corresponding to the lower evaporation temperature is still larger, leading to significant heat regeneration losses during compression and inhibiting unit performance. In existing technologies, the parallel connection of the two compressors fails to further optimize the coupling of their refrigerant flow paths, leaving room for improvement. Furthermore, patent CN 106225116 A does not utilize cascaded discharge, i.e., generating two different gradient condensation temperatures to adapt to the fluid temperature rise. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the existing technology and provide a fresh air dehumidification heat pump system that uses a series-parallel connection of compressors to switch between cascaded intake and exhaust. By cleverly switching two four-way reversing valves, the system can switch between the series and parallel connection of two compressors in cooling and heating modes, thereby achieving the switching between cascaded intake and cascaded exhaust and improving the performance of the unit.

[0006] From the outset, the applicant believed that if a two-stage compression system could be formed by connecting compressors in series on top of the stepped intake stage, it would help reduce exhaust temperature and heat loss, thereby further improving performance.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] This invention provides a fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust, including a refrigerant circulation path and an air flow path. The air flow path includes a supply air flow path and an exhaust air flow path. The refrigerant circulation path includes a first intake coil, a first throttling device, a supply air coil, a first one-way valve, a return air coil, an exhaust air coil, a first four-way reversing valve, and a first compressor connected in sequence.

[0009] The refrigerant circulation path further includes a second four-way reversing valve, a second compressor, an air inlet second coil, and a second throttling device connected in sequence. The second four-way reversing valve is connected to the first four-way reversing valve, and the second throttling device is connected to the air supply coil.

[0010] The refrigerant circulation path also includes a second check valve connected in parallel to the air supply coil and both ends of the first check valve;

[0011] The series-parallel connection of the compressors is converted between cooling and heating modes by the first four-way reversing valve and the second four-way reversing valve, thereby forming a stepped intake / stepped exhaust configuration.

[0012] Furthermore, the air supply path introduces outdoor fresh air, which flows sequentially through the first air inlet coil, the second air inlet coil, and the air supply coil before finally being delivered indoors;

[0013] The exhaust air path draws in indoor return air, flows through the return air coil and the exhaust air coil in sequence, and is then discharged to the outside.

[0014] Both the supply air path and the exhaust air path are equipped with fans to provide power for airflow.

[0015] Furthermore, in each port of the second four-way directional valve:

[0016] Port E is connected to the second air inlet coil, port C is connected to port S of the first four-way reversing valve and the suction port of the first compressor, port S is connected to the suction port of the second compressor, and port D is connected to the discharge port of the second compressor.

[0017] Furthermore, in each port of the first four-way directional valve:

[0018] Port E connects to the first air inlet coil, port C connects to the exhaust coil, port S connects to port C of the second four-way reversing valve and the suction port of the first compressor, and port D connects to the exhaust port of the first compressor.

[0019] Furthermore, the first throttling device and the second throttling device are selected from one of the following: capillary tube, throttling tube, and electronic throttling device.

[0020] Furthermore, in order to facilitate automated control, this technical solution preferably uses an electronic throttling device.

[0021] Furthermore, the first one-way valve is open in the direction that allows refrigerant to flow from the return air coil to the supply air coil, and closes in the reverse direction.

[0022] The second one-way valve allows refrigerant to flow from the first throttling device and the second throttling device to the return air coil, and shuts off in the reverse direction.

[0023] Furthermore, in cooling mode, ports E and S of the second four-way reversing valve are connected, which connects the intake ports of the second air coil and the second compressor, and ports D and C are connected, which connects the exhaust port of the second compressor and the intake port of the first compressor.

[0024] The first four-way reversing valve connects ports E and S, allowing the first air inlet coil and the first compressor's suction port to be connected; ports D and C connect, allowing the first compressor's exhaust port and the exhaust coil to be connected.

[0025] The second compressor and the first compressor are connected in series.

[0026] Furthermore, in cooling mode, the refrigerant flowing out of the air supply coil is divided into two parts: one part flows through the second throttling device, the second air inlet coil, the second four-way reversing valve, and the second compressor.

[0027] The other part flows through the first throttling device, the first air inlet coil, and the first four-way reversing valve;

[0028] In cooling mode, the two refrigerant branches are connected in parallel. After flowing out of the air coil, they split and merge at port S of the first four-way reversing valve. The two streams of refrigerant then enter the first compressor.

[0029] Furthermore, in heating mode, ports C and S of the second four-way reversing valve are connected, which connects ports S of the first four-way reversing valve and the suction port of the second compressor; ports D and E are connected, which connects the exhaust port of the second compressor and the second intake coil; ports C and S of the first four-way reversing valve are connected, which connects the exhaust coil and the suction port of the first compressor; ports D and E are connected, which connects the exhaust port of the first compressor and the first intake coil.

[0030] The first compressor and the second compressor are connected in parallel.

[0031] Furthermore, in heating mode, the refrigerant flowing out of the exhaust coil is divided into two parts after passing through the first four-way reversing valve. One part flows through the second four-way reversing valve, the second compressor, the second air inlet coil, and the second throttling device.

[0032] The other part flows through the first compressor, the first air inlet coil, and the first throttling device;

[0033] The two refrigerant branches are connected in parallel. After flowing out of the exhaust coil, they are split by the first four-way reversing valve and then merge before the second one-way valve.

[0034] The operation in cooling mode is as follows: The medium-pressure refrigerant in the first intake coil absorbs heat from the flowing air, initially cooling and dehumidifying the intake air. The low-pressure refrigerant in the second intake coil further treats the fresh air, deeply dehumidifying it. After evaporating and absorbing heat, the refrigerant in the coil enters the second compressor through the second four-way reversing valve and is compressed into medium-pressure refrigerant. This medium-pressure refrigerant then mixes with the medium-pressure refrigerant flowing out of the first intake coil after evaporating and absorbing heat, and together they enter the first compressor to be compressed into high-temperature, high-pressure refrigerant gas. This high-temperature, high-pressure refrigerant gas then flows sequentially through the exhaust coil and return coil, where the refrigerant condenses and subcools, releasing heat to the flowing return air to recover its cooling energy. It further flows through the supply coil for subcooling, recovering the cooling energy of the deeply cooled and dehumidified fresh air after entering the second intake coil, reheating it, and then sending it into the room. The refrigerant flowing out of the air supply coil is divided into two parts, which are throttled to low pressure and medium pressure by the second throttling device and the first throttling device, respectively, and then flow back to the second air inlet coil and the first air inlet coil to continue the refrigerant circulation.

[0035] The operation in heating mode is as follows: the low-pressure refrigerant in the return air coil and exhaust air coil evaporates and absorbs heat, extracting heat from the returning air to complete the return air heat recovery. After passing through the first four-way reversing valve, it splits into two parallel branches. One branch flows through the first compressor and is compressed into a high-temperature, high-pressure refrigerant, entering the first intake air coil to preheat the outdoor fresh air. The other branch passes through the second four-way reversing valve and enters the second compressor, where it is compressed into an even higher-pressure, high-temperature, high-pressure refrigerant, entering the second intake air coil to further heat the fresh air before being sent indoors. The refrigerant flowing out of the first and second intake air coils is throttled by the first and second throttling devices to become a low-temperature, low-pressure refrigerant, then mixed and returned to the return air coil through the second one-way valve (the supply air coil is bypassed) to continue the refrigerant circulation.

[0036] In cooling mode, the refrigerant evaporator side achieves cascaded air intake, maintaining different refrigerant pressures / saturation temperatures in the first and second air intake coils. This differentiates the sensible and latent heat of the air to a certain extent, which helps improve the overall dehumidification capacity and energy efficiency of the unit. In heating mode, the refrigerant condenser side achieves cascaded exhaust, maintaining different refrigerant pressures / saturation temperatures in the first and second air intake coils. This provides two-stage heating of the air, which helps reduce the average condensing pressure and improve overall energy efficiency.

[0037] This invention has the following structural features and beneficial effects:

[0038] 1. This invention utilizes the ingenious connection and switching of the flow paths of two four-way reversing valves to realize the conversion of the series-parallel relationship of the compressor in both cooling and heating modes. The overall structure is simple and easy to achieve large-scale production.

[0039] 2. In both cooling and heating modes, the first and second air inlet coils of this invention are always connected in parallel along the refrigerant flow path, forming a cascaded intake and cascaded exhaust configuration, respectively. In cooling mode, the cascaded intake generates two levels of evaporation temperature, handling the sensible and latent heat of the fresh air respectively, thus increasing the average evaporation pressure. In heating mode, the cascaded exhaust generates two levels of condensation temperature, heating the fresh air in stages, thus reducing the average condensation pressure. The increase in evaporation pressure and the decrease in condensation pressure contribute to improving the overall energy efficiency of the heat pump system.

[0040] 3. In cooling mode, the cascaded suction system, compared to a typical cascaded suction and discharge system, features a compressor in series, resulting in not only cascaded suction but also inter-stage compression with supplemental air supply. This reduces the exhaust temperature after compression, minimizes heat loss during circulation, and improves cycle efficiency. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the principle of the fresh air dehumidification heat pump system of the present invention (cooling mode).

[0042] Figure 2 This is a schematic diagram of the principle (heating mode) of the fresh air dehumidification heat pump system of the present invention.

[0043] In the diagram: 1. First air inlet coil, 2. Second air inlet coil, 3. Supply air coil, 4. Return air coil, 5. Exhaust air coil, 6. First throttling device, 7. Second throttling device, 8. First compressor, 9. Second compressor, 10. First four-way reversing valve, 11. Second four-way reversing valve, 12. First check valve, 13. Second check valve, 20. Air inlet, 21. Supply air, 22. Return air, 23. Exhaust air. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0045] Example 1

[0046] This embodiment describes a fresh air dehumidification heat pump system that uses a series and parallel connection of compressors to change the intake and exhaust of air in stages, including a refrigerant circulation path and an air flow path.

[0047] The refrigerant circulation path in this embodiment includes an inlet first coil 1, an inlet second coil 2, a supply coil 3, a return coil 4, an exhaust coil 5, a first throttling device 6, a second throttling device 7, a first compressor 8, a second compressor 9, a first four-way reversing valve 10, a second four-way reversing valve 11, a first one-way valve 12, a second one-way valve 13, and refrigerant copper pipes for connection.

[0048] The airflow path in this embodiment includes a supply air path and an exhaust air path. The supply air path introduces outdoor fresh air 20, which flows sequentially through the first intake coil 1, the second intake coil 2, and the supply air coil 3, and is then delivered indoors. The exhaust air path draws indoor return air 22, which flows sequentially through the return air coil 4 and the exhaust air coil 5 before being discharged outdoors. The supply and exhaust air paths are equipped with corresponding fans to provide the power for airflow.

[0049] In this embodiment, the second four-way reversing valve 11 has its port E connected to the second air inlet coil 2, its port C connected to the port S of the first four-way reversing valve 10 and the suction port of the first compressor 8, its port S connected to the suction port of the second compressor 9, and its port D connected to the exhaust port of the second compressor 9.

[0050] In this embodiment, the first four-way reversing valve 10 has its port E connected to the first air inlet coil 1, its port C connected to the exhaust coil 5, its port S connected to the port C of the second four-way reversing valve 11 and the air intake of the first compressor 8, and its port D connected to the exhaust port of the first compressor 8.

[0051] This embodiment describes a fresh air dehumidification heat pump system that uses a series and parallel connection of compressors to change the intake and exhaust of air in stages. It has at least two operating modes: a cooling mode and a heating mode.

[0052] In cooling mode, ports E and S of the second four-way reversing valve 11 are connected, connecting the intake ports of the second air inlet coil 2 and the second compressor 9; ports D and C are connected, connecting the exhaust port of the second compressor 9 and the intake port of the first compressor 8. Ports E and S of the first four-way reversing valve 10 are connected, connecting the intake ports of the first air inlet coil 1 and the first compressor 8; ports D and C are connected, connecting the exhaust port of the first compressor 8 and the exhaust coil 5.

[0053] In heating mode, ports C and S of the second four-way reversing valve 11 are connected, which connects ports S of the first four-way reversing valve 10 and the suction port of the second compressor 9. Ports D and E are connected, which connects the exhaust port of the second compressor 9 and the second air inlet coil 2. Ports C and S of the first four-way reversing valve 10 are connected, which connects the exhaust coil 5 and the suction port of the first compressor 8. Ports D and E are connected, which connects the exhaust port of the first compressor 8 and the first air inlet coil 1.

[0054] In this embodiment, the fresh air dehumidification heat pump system operates in cooling mode. The refrigerant flowing out of the supply coil 3 is divided into two parts: one part flows through the second throttling device 7, the second inlet coil 2, the second four-way reversing valve 11, and the second compressor 9; the other part flows through the first throttling device 6, the first inlet coil 1, and the first four-way reversing valve 10. These two refrigerant branches are connected in parallel, and after flowing out of the supply coil 3, they split and merge at port S of the first four-way reversing valve 10. The merged refrigerant then enters the first compressor 8. In cooling mode, the second compressor 9 and the first compressor 8 are connected in series.

[0055] In this embodiment, the fresh air dehumidification heat pump system operates in heating mode. The refrigerant flowing from exhaust coil 5 is divided into two parts after passing through the first four-way reversing valve 10. One part flows through the second four-way reversing valve 11, the second compressor 9, the second inlet coil 2, and the second throttling device 7; the other part flows through the first compressor 8, the first inlet coil 1, and the first throttling device 6. These two refrigerant branches are connected in parallel, flowing out of exhaust coil 5 and then splitting through the first four-way reversing valve 10 before merging before the second one-way valve 13. In heating mode, the first compressor 8 and the second compressor 9 are connected in parallel.

[0056] In this embodiment, a fresh air dehumidification heat pump system using a series-parallel compressor for cascaded intake and exhaust operates as follows in cooling mode: The medium-pressure refrigerant in the first intake coil 1 absorbs heat from the flowing air, initially cooling and dehumidifying the intake air 20; the low-pressure refrigerant in the second intake coil 2 further processes the fresh air, deeply dehumidifying it. After evaporating and absorbing heat, the refrigerant in the coil enters the second compressor 9 via the second four-way reversing valve 11 and is compressed into medium-pressure refrigerant. This medium-pressure refrigerant then mixes with the medium-pressure refrigerant flowing out of the first intake coil 1 and enters the first compressor 8, where it is compressed into high-temperature, high-pressure refrigerant gas. This high-temperature, high-pressure refrigerant gas then flows sequentially through the exhaust coil 5 and the return coil 4, where the refrigerant condenses and subcools, releasing heat to the flowing return air 22 to recover its cooling energy. It further flows through the supply coil 3 for subcooling, recovering the cooling energy of the deeply cooled and dehumidified fresh air after entering the second intake coil 2, reheating it, and then sending it into the room. The refrigerant flowing out of the air supply coil 3 is divided into two parts, which are throttled to low pressure and medium pressure by the second throttling device 7 and the first throttling device 6 respectively, and then flow back to the second air inlet coil 2 and the first air inlet coil 1 to continue the refrigerant circulation.

[0057] In this embodiment, a fresh air dehumidification heat pump system with series and parallel compressors for cascaded intake and exhaust operates as follows in heating mode: Low-pressure refrigerant in return air coil 4 and exhaust air coil 5 evaporates and absorbs heat, recovering heat from the flowing return air. After passing through the first four-way reversing valve 10, it splits into two parallel branches. One branch flows through the first compressor 8 and is compressed into high-temperature, high-pressure refrigerant, entering the first intake air coil 1 to preheat the outdoor fresh air 20. The other branch passes through the second four-way reversing valve 11 and enters the second compressor 9, where it is compressed into even higher-pressure, high-temperature, high-pressure refrigerant, entering the second intake air coil 2 for further heating of the fresh air before being sent indoors. The refrigerant flowing out of the first intake air coil 1 and the second intake air coil 2 is throttled by the first throttling device 6 and the second throttling device 7 into low-temperature, low-pressure refrigerant, then mixed and returned to the return air coil 4 via the second one-way valve 13 (bypassing the supply air coil 3) to continue refrigerant circulation.

[0058] The use of terms such as "first" and "second" to define components in this document is merely for descriptive purposes to distinguish the components. Unless otherwise stated, these terms have no special meaning.

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust, comprising a refrigerant circulation path and an air flow path, wherein the air flow path includes a supply air flow path and an exhaust air flow path, characterized in that, The refrigerant circulation path includes an inlet first coil (1), a first throttling device (6), an air supply coil (3), a first one-way valve (12), a return air coil (4), an exhaust coil (5), a first four-way reversing valve (10), and a first compressor (8) connected in sequence. The refrigerant circulation path also includes a second four-way reversing valve (11), a second compressor (9), an air inlet second coil (2), and a second throttling device (7) connected in sequence. The second four-way reversing valve (11) is connected to the first four-way reversing valve (10), and the second throttling device (7) is connected to the air supply coil (3). The refrigerant circulation path also includes a second one-way valve (13) connected in parallel to the air supply coil (3) and the first one-way valve (12); The first four-way reversing valve (10) and the second four-way reversing valve (11) are used to convert the series-parallel relationship of the compressor in the two modes of cooling / heating, so as to form a step-by-step intake / step-by-step exhaust form.

2. The fresh air dehumidification heat pump system based on compressor series-parallel conversion cascade intake and exhaust as described in claim 1, characterized in that, The air supply path introduces outdoor fresh air (20), which flows through the first air inlet coil (1), the second air inlet coil (2) and the air supply coil (3) in sequence, and is finally delivered to the room; The exhaust air path draws in the indoor return air (22), flows through the return air coil (4) and the exhaust air coil (5) in sequence, and then discharges to the outside; Both the supply air path and the exhaust air path are equipped with fans to provide power for airflow.

3. The fresh air dehumidification heat pump system based on compressor series-parallel conversion staged intake and exhaust as described in claim 1, characterized in that, In each port of the second four-way directional valve (11): Port E is connected to the second air inlet coil (2), port C is connected to port S of the first four-way reversing valve (10) and the suction port of the first compressor (8), port S is connected to the suction port of the second compressor (9), and port D is connected to the exhaust port of the second compressor (9).

4. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 3, is characterized in that... In each port of the first four-way directional valve (10): Port E is connected to the first air inlet coil (1), port C is connected to the exhaust coil (5), port S is connected to port C of the second four-way reversing valve (11) and the suction port of the first compressor (8), and port D is connected to the exhaust port of the first compressor (8).

5. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 1, is characterized in that... The first throttling device (6) and the second throttling device (7) are selected from one of the following: capillary tube, throttling tube, and electronic throttling device.

6. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 1, is characterized in that... The first one-way valve (12) is open in the direction that allows refrigerant to flow from the return air coil (4) into the supply air coil (3), and closes in the reverse direction; The second one-way valve (13) is open in the direction that allows refrigerant to flow from the first throttling device (6) and the second throttling device (7) to the return air coil (4), and closes in the reverse direction.

7. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 4, is characterized in that... In cooling mode, ports E and S of the second four-way reversing valve (11) are connected, which connects the second air inlet coil (2) and the suction port of the second compressor (9). Ports D and C are connected, which connects the exhaust port of the second compressor (9) and the suction port of the first compressor (8). The first four-way reversing valve (10) connects port E and port S to connect the first air inlet coil (1) and the suction port of the first compressor (8), and connects port D and port C to connect the exhaust port of the first compressor (8) and the exhaust coil (5). The second compressor (9) and the first compressor (8) are connected in series.

8. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 7, is characterized in that... In cooling mode, the refrigerant flowing out of the air supply coil (3) is divided into two parts. One part flows through the second throttling device (7), the second air inlet coil (2), the second four-way reversing valve (11), and the second compressor (9). The other part flows through the first throttling device (6), the first air inlet coil (1), and the first four-way reversing valve (10); In the cooling mode, the two refrigerant branches are connected in parallel. After flowing out from the air coil (3), they are split and merge at port S of the first four-way reversing valve (10). The two refrigerants after merging then enter the first compressor (8).

9. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 4, is characterized in that... In heating mode, ports C and S of the second four-way reversing valve (11) are connected, which connects ports S of the first four-way reversing valve (10) and the suction port of the second compressor (9). Ports D and E are connected, which connects the exhaust port of the second compressor (9) and the second air inlet coil (2). Ports C and S of the first four-way reversing valve (10) are connected, which connects the exhaust coil (5) and the suction port of the first compressor (8). Ports D and E are connected, which connects the exhaust port of the first compressor (8) and the first air inlet coil (1). The first compressor (8) and the second compressor (9) are connected in parallel.

10. A fresh air dehumidification heat pump system based on a series-parallel compressor conversion stage for intake and exhaust air, as described in claim 9, is characterized in that... In heating mode, the refrigerant flowing out of the exhaust coil (5) is divided into two parts after passing through the first four-way reversing valve (10). One part flows through the second four-way reversing valve (11), the second compressor (9), the second air inlet coil (2), and the second throttling device (7). Another portion flows through the first compressor (8), the first air inlet coil (1), and the first throttling device (6); The two refrigerant branches are connected in parallel. After flowing out from the exhaust coil (5), they are split by the first four-way reversing valve (10) and merged before the second one-way valve (13).

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