Heat pump system and refrigerating unit for refrigerated vehicle

Abstract

The utility model discloses a heat pump system for refrigeration car, and the system includes compressor, reversing mechanism, outdoor heat exchanger, indoor heat exchanger and expansion valve group, and the expansion valve group is configured as: when refrigeration / heating / defrosting, the refrigerant output of outdoor heat exchanger or indoor heat exchanger is throttled into gas-liquid mixture, and when refrigeration / outdoor defrosting, the enthalpy increasing gas is provided to the enthalpy increasing suction port of compressor, the indoor fan starts when heating, and the outdoor fan of outdoor heat exchanger starts, the indoor fan does not start and the outdoor fan starts when indoor defrosting, the integrated enthalpy increasing refrigeration system and heat pump system reduce temperature fluctuation while effectively reducing energy consumption and improving reliability, greatly reduce cost, realize the need of enthalpy increasing refrigeration function, heating function and quick defrosting, satisfy various practical use demand. The utility model discloses still a refrigerating unit for refrigeration car including above-mentioned heat pump system.

Description

Technical Field

[0001] This utility model relates to the field of cold chain technology, and in particular to a heat pump system. Furthermore, this utility model also relates to a refrigeration unit for refrigerated trucks that includes the aforementioned heat pump system. Background Technology

[0002] In existing refrigeration units used in refrigerated trucks, a single enthalpy-increasing refrigeration system is used. The throttling element is mostly a thermostatic expansion valve. A parallel line is connected to the indoor evaporator through the compressor exhaust pipe, and the compressor exhaust is directly led to the indoor evaporator for defrosting.

[0003] In the process of realizing this invention, the inventors discovered that the prior art has at least the following problems: this method cannot meet the indoor heating demand, the indoor evaporator has poor defrosting effect, and the refrigerant pressure and superheat are difficult to control, which can easily lead to a reduction in compressor life or failure.

[0004] Therefore, how to provide a heat pump system with good indoor defrosting effect and indoor heating function is a technical problem that needs to be solved by those skilled in the art. Utility Model Content

[0005] The purpose of this invention is to provide a heat pump system with good indoor defrosting effect and indoor heating function. Another purpose of this invention is to provide a refrigeration unit for refrigerated trucks that includes the above-mentioned heat pump system.

[0006] To effectively solve the above-mentioned technical problems, this utility model provides a heat pump system for refrigerated trucks. The heat pump system includes a compressor, a reversing mechanism, an outdoor heat exchanger, an indoor heat exchanger, and an expansion valve assembly. The compressor's exhaust port and main suction port are respectively connected to the reversing mechanism, and the compressor's enthalpy-increasing suction port is connected to the expansion valve assembly. The outdoor heat exchanger is connected to both the reversing mechanism and the expansion valve assembly, and the indoor heat exchanger is connected to both the reversing mechanism and the expansion valve assembly. The expansion valve assembly is configured to: [functions related to cooling / heating / outdoor defrosting / indoor defrosting]. During operation, the refrigerant output from the outdoor heat exchanger or the indoor heat exchanger is throttled into a gas-liquid mixture, and during cooling / outdoor defrosting, enthalpy-increasing gas is provided to the enthalpy-increasing suction port; during heating or indoor defrosting, the refrigerant output from the exhaust port flows sequentially through the reversing mechanism, the indoor heat exchanger, the expansion valve assembly, the outdoor heat exchanger, and the reversing mechanism before flowing back to the main suction port; during heating, the indoor fan of the indoor heat exchanger starts and the outdoor fan of the outdoor heat exchanger starts; during indoor defrosting, the indoor fan does not start and the outdoor fan starts.

[0007] Optionally, the reversing mechanism includes a four-way reversing valve, which includes a first connection port, a second connection port, a third connection port, and a fourth connection port. The first connection port is connected to the exhaust port, the second connection port is connected to the main intake port, the third connection port is connected to the outdoor heat exchanger, and the fourth connection port is connected to the indoor heat exchanger.

[0008] Optionally, electric heaters are provided on the sides of both the outdoor heat exchanger and the indoor heat exchanger.

[0009] Optionally, a water collection tank is provided directly below both the outdoor heat exchanger and the indoor heat exchanger.

[0010] Optionally, both the outdoor heat exchanger and the indoor heat exchanger are equipped with frost detectors. The heat pump system also includes a controller that is communicatively connected to the electric heater and the frost detector. Based on the detection results of the frost detector, the controller controls the start and stop of the electric heater, the outdoor fan, and the indoor fan, respectively.

[0011] Optionally, the expansion valve assembly includes a first expansion valve and a second expansion valve. The outdoor heat exchanger is connected to the indoor heat exchanger through the first expansion valve. The enthalpy-increasing suction port is connected to the pipeline between the outdoor heat exchanger and the first expansion valve through the second expansion valve. During cooling or outdoor defrosting, the refrigerant output from the exhaust port flows sequentially through the reversing mechanism, the outdoor heat exchanger, the first expansion valve, the indoor heat exchanger, and the reversing mechanism before flowing back to the main suction port. A portion of the refrigerant flowing out of the outdoor heat exchanger flows back to the enthalpy-increasing suction port through the second expansion valve. During cooling, both the indoor and outdoor fans are started. During outdoor defrosting, neither the indoor nor outdoor fans are started.

[0012] Optionally, the expansion valve assembly further includes an economizer, which includes a first interface, a second interface, an enthalpy-increasing inlet, and an enthalpy-increasing outlet. The first interface is connected to the second interface, and the enthalpy-increasing inlet is connected to the enthalpy-increasing outlet. The first interface is connected to the outdoor heat exchanger, and the second interface is connected to the first expansion valve and the second expansion valve, respectively. The second expansion valve is connected to the enthalpy-increasing inlet, and the enthalpy-increasing outlet is connected to the enthalpy-increasing suction port.

[0013] Optionally, a shut-off valve is provided at the inlet of the second expansion valve.

[0014] Optionally, the economizer, the first expansion valve, and the second expansion valve are integrated into one unit.

[0015] This utility model also provides a refrigeration unit for refrigerated vehicles, including the heat pump system described in any of the above.

[0016] Compared with the prior art, the technical solution provided by this utility model has at least the following beneficial effects: It integrates an enthalpy-increasing refrigeration system and a heat pump system, and can achieve dynamic flow control through an expansion valve group, simplifying the system and reducing costs. Furthermore, it can achieve heat pump heating and heat pump defrosting through the working state of the expansion valve group and the corresponding fan, effectively ensuring the superheat of the compressor suction, preventing liquid from entering the cylinder during compression, improving the compressor's operational stability, reducing temperature fluctuations while effectively reducing energy consumption and improving reliability, and greatly reducing costs. It achieves the needs of enthalpy-increasing refrigeration, heating, and rapid defrosting, with good indoor defrosting effect and indoor heating function, meeting a variety of practical usage requirements.

[0017] This utility model also provides a refrigeration unit including the above-mentioned heat pump system. Since the above-mentioned heat pump system has the above-mentioned technical effects, the above-mentioned refrigeration unit should also have the same technical effects, and will not be described in detail here. Attached Figure Description

[0018] Figure 1 A schematic diagram of a specific embodiment of the heat pump system provided by this utility model;

[0019] Figure 2 A schematic diagram of another specific embodiment of the heat pump system provided by this utility model;

[0020] Figure 3 A flow diagram illustrating the refrigeration mode of a specific embodiment of the heat pump system provided by this utility model;

[0021] Figure 4 A flow diagram of the heating mode of a specific embodiment of the heat pump system provided by this utility model;

[0022] Figure 5 An indoor defrosting mode flow diagram of a specific embodiment of the heat pump system provided by this utility model;

[0023] Figure 6 The flow path diagram for the outdoor defrosting mode of a specific embodiment of the heat pump system provided by this utility model.

[0024] Among them, 1-compressor, 2-four-way reversing valve, 3-outdoor heat exchanger, 4-outdoor fan, 5-economizer, 6-first expansion valve, 7-second expansion valve, 8-indoor heat exchanger, 9-indoor fan, 10-expansion valve assembly. Detailed Implementation

[0025] The core of this invention is to provide a heat pump system with good indoor defrosting effect and indoor heating function. Specifically, it provides enthalpy-increasing cooling function through the operation of the expansion valve group and the corresponding fan, while also having heating and rapid defrosting functions. Another core aspect of this invention is to provide a refrigeration unit for refrigerated trucks that includes the above-mentioned heat pump system.

[0026] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Please refer to Figures 1 to 6 , Figure 1 A schematic diagram of a specific embodiment of the heat pump system provided by this utility model; Figure 2 A schematic diagram of another specific embodiment of the heat pump system provided by this utility model; Figure 3 A flow diagram illustrating the refrigeration mode of a specific embodiment of the heat pump system provided by this utility model; Figure 4 A flow diagram of the heating mode of a specific embodiment of the heat pump system provided by this utility model; Figure 5 An indoor defrosting mode flow diagram of a specific embodiment of the heat pump system provided by this utility model; Figure 6 The flow path diagram for the outdoor defrosting mode of a specific embodiment of the heat pump system provided by this utility model.

[0028] This utility model provides a heat pump system for refrigerated trucks, capable of meeting the cooling and heating needs of the truck's interior (or cargo compartment), and also possessing indoor and outdoor defrosting capabilities. The heat pump system includes a compressor 1, a reversing mechanism, an outdoor heat exchanger 3, an indoor heat exchanger 8, and an expansion valve assembly 10. The compressor 1 compresses the refrigerant and provides the refrigerant circulation power. The compressor 1 is equipped with an exhaust port, a main suction port, and an enthalpy-increasing suction port. The exhaust port and main suction port of the compressor 1 are respectively connected to the reversing mechanism, which is also respectively connected to the first interface of the outdoor heat exchanger 3 and the first interface of the indoor heat exchanger 8. The reversing mechanism can change the flow direction of the refrigerant, allowing the refrigerant to flow from the indoor heat exchanger 8 to the outdoor heat exchanger 3, or vice versa. The refrigerant flows to the indoor heat exchanger 8, thereby enabling mode switching. Furthermore, the enthalpy-increasing suction port of the compressor 1 is connected to the expansion valve assembly 10, the second port of the outdoor heat exchanger 3 is connected to the expansion valve assembly 10, and the second port of the indoor heat exchanger 8 is connected to the expansion valve assembly 10. The expansion valve assembly 10 is configured to: throttle the refrigerant output from the outdoor heat exchanger 3 or the indoor heat exchanger 8 into a low-temperature, low-pressure gas-liquid mixture during cooling / heating / outdoor defrosting / indoor defrosting, and provide enthalpy-increasing gas to the enthalpy-increasing suction port of the compressor 1 during cooling / outdoor defrosting to achieve gas replenishment and enthalpy increase.

[0029] During cooling, the refrigerant output from the exhaust port of compressor 1 flows to the first port of outdoor heat exchanger 3 through the reversing mechanism. The refrigerant releases heat and condenses into a liquid state. The refrigerant flowing out from the second port of outdoor heat exchanger 3 flows into expansion valve group 10, and then splits into two paths. One path flows back to the enthalpy-increasing suction port of compressor 1 to provide enthalpy-increasing gas to compressor 1, realizing gas replenishment and enthalpy increase. The other path flows to the second port of indoor heat exchanger 8. The refrigerant absorbs heat and evaporates, and the indoor air releases heat and cools down. The refrigerant flowing out from the first port of indoor heat exchanger 8 flows back to the main suction port of compressor 1 through the reversing mechanism to complete the enthalpy-increasing cooling work. In this mode, the indoor fan 9 of indoor heat exchanger 8 is started and the outdoor fan 4 of outdoor heat exchanger 3 is started.

[0030] During heating, the refrigerant discharged from the exhaust port of compressor 1 flows to the first port of indoor heat exchanger 8 through the reversing mechanism. The refrigerant releases heat and condenses, while the indoor air absorbs heat and rises in temperature. The refrigerant flowing out from the second port of indoor heat exchanger 8 flows into the second port of outdoor heat exchanger 3 through expansion valve group 10. The refrigerant absorbs heat and evaporates. The refrigerant flowing out from the first port of outdoor heat exchanger 3 flows back to the main suction port of compressor 1 through the reversing mechanism to complete the heating operation. In this mode, the indoor fan 9 of indoor heat exchanger 8 is started and the outdoor fan 4 of outdoor heat exchanger 3 is started.

[0031] During indoor defrosting, the refrigerant output from the exhaust port of compressor 1 flows to the first port of indoor heat exchanger 8 through the reversing mechanism. The high-temperature and high-pressure refrigerant releases heat in indoor heat exchanger 8 to dissolve the frost on the surface of indoor heat exchanger 8. The refrigerant releases heat and condenses into a liquid state. The refrigerant flowing out from the second port of indoor heat exchanger 8 flows into the second port of outdoor heat exchanger 3 through expansion valve group 10. The refrigerant absorbs heat and evaporates. The refrigerant flowing out from the first port of outdoor heat exchanger 3 flows back to the main suction port of compressor 1 through the reversing mechanism to complete the indoor defrosting work. In this mode, the indoor fan 9 of indoor heat exchanger 8 does not start and the outdoor fan 4 of outdoor heat exchanger 3 starts.

[0032] During outdoor defrosting, the refrigerant output from the exhaust port of compressor 1 flows to the first port of outdoor heat exchanger 3 through the reversing mechanism. The high-temperature and high-pressure refrigerant releases heat in outdoor heat exchanger 3 to dissolve the frost on the surface of outdoor heat exchanger 3. The refrigerant releases heat and condenses into a liquid state. The refrigerant flowing out from the second port of outdoor heat exchanger 3 flows into expansion valve group 10, and then splits into two paths. One path flows back to the enthalpy-increasing suction port of compressor 1 to provide enthalpy-increasing gas to compressor 1, realizing gas replenishment and enthalpy increase. The other path flows to the second port of indoor heat exchanger 8. The refrigerant absorbs heat and evaporates. The refrigerant flowing out from the first port of indoor heat exchanger 8 flows back to the main suction port of compressor 1 through the reversing mechanism to complete the outdoor defrosting work. In this mode, the indoor fan 9 of indoor heat exchanger 8 does not start and the outdoor fan 4 of outdoor heat exchanger 3 does not start.

[0033] As can be seen from the above, enthalpy-increasing refrigeration function can be provided through the working state of the expansion valve assembly 10 and the corresponding fan, while also having heating and rapid defrosting functions. That is, this utility model integrates an enthalpy-increasing refrigeration system and a heat pump system. Dynamic flow control can be achieved through the expansion valve assembly 10, simplifying the system and reducing costs. Furthermore, heat pump heating and defrosting can be achieved through the working state of the expansion valve assembly 10 and the corresponding fan, effectively ensuring the superheat of the compressor 1's suction gas and preventing liquid carryover in the cylinder compression, thus improving the operational stability of the compressor 1. While effectively reducing energy consumption and improving reliability, it also reduces temperature fluctuations and significantly lowers costs, achieving the needs of enthalpy-increasing refrigeration, heating, and rapid defrosting. It provides good indoor defrosting performance and indoor heating function, meeting various practical usage requirements.

[0034] Specifically, the reversing mechanism includes a four-way reversing valve 2, which includes a first connection port, a second connection port, a third connection port, and a fourth connection port. The first connection port is connected to the exhaust port, the second connection port is connected to the main suction port, the third connection port is connected to the outdoor heat exchanger 3, and the fourth connection port is connected to the indoor heat exchanger 8. The connected interface is selected according to the working mode. During cooling or outdoor defrosting, the first connection port is connected to the third connection port, and the second connection port is connected to the fourth connection port. During heating or indoor defrosting, the first connection port is connected to the fourth connection port, and the second connection port is connected to the third connection port.

[0035] Based on the heat pump system provided in the above specific embodiments, the expansion valve assembly 10 includes a first expansion valve 6 and a second expansion valve 7, wherein both the first expansion valve 6 and the second expansion valve 7 can be electronic expansion valves. During cooling or outdoor defrosting, the first expansion valve 6 and the second expansion valve 7 work simultaneously; during heating or indoor defrosting, only the first expansion valve 6 works, and the second expansion valve 7 does not work. Specifically, the second port of the outdoor heat exchanger 3 is connected to the second port of the indoor heat exchanger 8 through the first expansion valve 6. The enthalpy-increasing suction port is connected to the pipeline between the outdoor heat exchanger 3 and the first expansion valve 6 through the second expansion valve 7. During cooling or outdoor defrosting, the refrigerant output from the exhaust port flows sequentially through the reversing mechanism, the outdoor heat exchanger 3, the first expansion valve 6, the indoor heat exchanger 8, and the reversing mechanism before flowing back to the main suction port of the compressor 1. A portion of the refrigerant flowing out of the outdoor heat exchanger 3 flows back to the enthalpy-increasing suction port of the compressor 1 through the second expansion valve 7. During cooling, the indoor fan 9 and the outdoor fan 4 are started. During outdoor defrosting, the indoor fan 9 and the outdoor fan 4 are not started.

[0036] Furthermore, the expansion valve assembly 10 also includes an economizer 5, which includes a first port, a second port, an enthalpy-increasing inlet, and an enthalpy-increasing outlet. The first port is connected to the second port to form a main flow path, and the enthalpy-increasing inlet is connected to the enthalpy-increasing outlet to form an enthalpy-increasing flow path. The first port of the economizer 5 is connected to the second port of the outdoor heat exchanger 3, and the second port of the economizer 5 is connected to the first expansion valve 6 and the second expansion valve 7 respectively. The second expansion valve 7 is connected to the enthalpy-increasing inlet, and the enthalpy-increasing outlet is connected to the enthalpy-increasing suction port.

[0037] In enthalpy-increasing cooling mode, the refrigerant compressed by compressor 1 is discharged from the exhaust port, passes through the four-way reversing valve 2, and enters the outdoor heat exchanger 3. The outdoor fan 4 performs work to exchange heat with the outdoor air, and the refrigerant releases heat and condenses into a liquid state. Then, it passes through the main flow path of the economizer 5 and exchanges heat with the low-pressure and low-temperature refrigerant in the enthalpy-increasing flow path for further subcooling. After that, it splits into two paths. The first branch passes through the second expansion valve 7 and then passes through the economizer 5 to absorb heat from the main path (i.e., the main flow path) and evaporates before flowing into the enthalpy-increasing suction port of compressor 1. The second branch passes through the first expansion valve 6 and then enters the indoor heat exchanger 8. The indoor fan 9 performs forced heat exchange with the indoor air, and the refrigerant absorbs heat and evaporates. The indoor air releases heat and cools down. After evaporation, the refrigerant flows out to the four-way reversing valve 2 and finally flows into the main suction port of compressor 1. Together with the refrigerant provided by the first branch, it is compressed in compressor 1 and discharged, continuing the cycle.

[0038] In heating mode, the refrigerant compressed by compressor 1 is discharged from the exhaust port, and after being reversed by four-way reversing valve 2, it enters indoor heat exchanger 8. Indoor fan 9 forces heat exchange with indoor air, the refrigerant releases heat and condenses, and the indoor air absorbs heat and rises in temperature. After passing through first expansion valve 6 for throttling, it enters economizer 5. In this mode, second expansion valve 7 does not start, and economizer 5 has no heat exchange function. After flowing through, the refrigerant directly enters outdoor heat exchanger 3, where outdoor fan 4 performs work to force heat exchange with outdoor air. The refrigerant absorbs heat and evaporates, and finally enters four-way reversing valve 2 again to enter compressor 1's suction port. After being compressed in compressor 1, it is discharged, and the cycle continues.

[0039] In indoor defrost mode, while the indoor cooling mode is running, the four-way reversing valve 2 opens when the indoor defrost signal is detected, and the system runs a heat pump cycle for defrosting. At this time, the refrigerant discharged from the compressor 1 exhaust port enters the indoor heat exchanger 8 after being diverted by the four-way reversing valve 2. The indoor fan 9 does not start at this time. The high-temperature and high-pressure refrigerant releases heat in the heat exchanger to dissolve the frost on the surface of the indoor heat exchanger 8. The refrigerant releases heat and condenses into a liquid state, and then flows into the economizer 5 through the first expansion valve 6. In this mode, the second expansion valve 7 does not start, and the economizer 5 has no heat exchange function. After flowing through, the refrigerant directly enters the outdoor heat exchanger 3, where the outdoor fan 4 performs work to exchange heat with the outdoor air. The refrigerant absorbs heat and evaporates, and finally enters the compressor 1 intake port again through the four-way reversing valve 2. After being compressed in the compressor 1, it is discharged and the cycle continues.

[0040] When the outdoor defrost mode is running and the indoor heating mode is active, the four-way reversing valve 2 closes when the outdoor defrost signal is detected. At this time, the refrigerant discharged from the compressor 1 outlet enters the outdoor heat exchanger 3 after being diverted by the four-way reversing valve 2. The outdoor fan 4 does not start. The high-temperature and high-pressure refrigerant releases heat in the heat exchanger to dissolve the frost on the surface of the outdoor heat exchanger 3. The refrigerant releases heat and condenses into a liquid state. Then, it passes through the economizer 5 and exchanges heat with the low-pressure and low-temperature refrigerant in the auxiliary circuit (i.e., the enthalpy-increasing flow path) for further subcooling. After that, it splits into two paths. The first branch, after being throttled by the second expansion valve 7, absorbs heat from the main circuit (i.e., the main flow circuit) through the economizer 5 and evaporates before flowing into the enthalpy-increasing suction port of the compressor 1. The second branch, after being throttled by the first expansion valve 6, enters the indoor heat exchanger 8. At this time, the indoor fan 9 is not started. The refrigerant absorbs heat and evaporates by exchanging heat with the indoor air through natural heat dissipation. After flowing out, it enters the four-way reversing valve 2 and finally flows into the first suction port of the compressor 1. Together with the refrigerant provided by the first branch, it is compressed in the compressor 1 and discharged, continuing the cycle.

[0041] To improve system reliability, a shut-off valve can be installed at the inlet of the second expansion valve 7. This shut-off valve operates when the second expansion valve 7 is not needed, preventing refrigerant from entering. To save installation space, the economizer 5, the first expansion valve 6, and the second expansion valve 7 can be integrated into a single unit.

[0042] Optionally, electric heaters are provided on the sides of both the outdoor heat exchanger 3 and the indoor heat exchanger 8. The electric heaters can be used to assist defrosting, and the electric heaters on the sides of the indoor heat exchanger 8 can also be used for indoor auxiliary heating. Water collection tanks are provided directly below both the outdoor heat exchanger 3 and the indoor heat exchanger 8. Frost detectors are provided on both the outdoor heat exchanger 3 and the indoor heat exchanger 8. The heat pump system also includes a controller that communicates with the electric heaters and the frost detectors. Based on the detection results of the frost detectors, the controller controls the start and stop of the electric heaters, the outdoor fan 4, and the indoor fan 9, respectively.

[0043] In addition to the heat pump system described above, this utility model also provides a refrigeration unit for refrigerated vehicles that includes the heat pump system described above. The structure of other parts of the refrigeration unit can be referred to the prior art, and will not be described in detail here.

[0044] The heat pump system and refrigeration unit for refrigerated trucks provided by this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this utility model. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principles of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A heat pump system, characterized in that, For use in refrigerated trucks; the heat pump system includes a compressor (1), a reversing mechanism, an outdoor heat exchanger (3), an indoor heat exchanger (8), and an expansion valve assembly (10). The exhaust port and main suction port of the compressor (1) are respectively connected to the reversing mechanism, and the enthalpy-increasing suction port of the compressor (1) is connected to the expansion valve assembly (10). The outdoor heat exchanger (3) is respectively connected to the reversing mechanism and the expansion valve assembly (10), and the indoor heat exchanger (8) is respectively connected to the reversing mechanism and the expansion valve assembly (10). The expansion valve assembly (10) is configured to: during cooling / heating / outdoor defrosting / indoor defrosting, transfer the outdoor heat exchanger... The refrigerant output from the heat exchanger (3) or the indoor heat exchanger (8) is throttled into a gas-liquid mixture, and during cooling / outdoor defrosting, enthalpy-increasing gas is provided to the enthalpy-increasing suction port; during heating or indoor defrosting, the refrigerant output from the exhaust port flows sequentially through the reversing mechanism, the indoor heat exchanger (8), the expansion valve group (10), the outdoor heat exchanger (3) and the reversing mechanism and then flows back to the main suction port. During heating, the indoor fan (9) of the indoor heat exchanger (8) is started and the outdoor fan (4) of the outdoor heat exchanger (3) is started. During indoor defrosting, the indoor fan (9) is not started and the outdoor fan (4) is started.

2. The heat pump system according to claim 1, characterized in that, The reversing mechanism includes a four-way reversing valve (2), which includes a first connection port, a second connection port, a third connection port and a fourth connection port. The first connection port is connected to the exhaust port, the second connection port is connected to the main intake port, the third connection port is connected to the outdoor heat exchanger (3), and the fourth connection port is connected to the indoor heat exchanger (8).

3. The heat pump system according to claim 1, characterized in that, Electric heaters are provided on the sides of both the outdoor heat exchanger (3) and the indoor heat exchanger (8).

4. The heat pump system according to claim 3, characterized in that, A water collection tank is provided directly below both the outdoor heat exchanger (3) and the indoor heat exchanger (8).

5. The heat pump system according to claim 4, characterized in that, Both the outdoor heat exchanger (3) and the indoor heat exchanger (8) are equipped with frost detectors. The heat pump system also includes a controller that communicates with the electric heater and the frost detector. Based on the detection results of the frost detector, the controller controls the start and stop of the electric heater, the outdoor fan (4) and the indoor fan (9) respectively.

6. The heat pump system according to any one of claims 1 to 5, characterized in that, The expansion valve assembly (10) includes a first expansion valve (6) and a second expansion valve (7). The outdoor heat exchanger (3) is connected to the indoor heat exchanger (8) through the first expansion valve (6). The enthalpy-increasing suction port is connected to the pipeline between the outdoor heat exchanger (3) and the first expansion valve (6) through the second expansion valve (7). During cooling or outdoor defrosting, the refrigerant output from the exhaust port flows sequentially through the reversing mechanism, the outdoor heat exchanger (3), the first expansion valve (6), the indoor heat exchanger (8), and the reversing mechanism before flowing back to the main suction port. A portion of the refrigerant flowing out of the outdoor heat exchanger (3) flows back to the enthalpy-increasing suction port through the second expansion valve (7). During cooling, the indoor fan (9) starts and the outdoor fan (4) starts. During outdoor defrosting, the indoor fan (9) does not start and the outdoor fan (4) does not start.

7. The heat pump system according to claim 6, characterized in that, The expansion valve assembly (10) also includes an economizer (5), which includes a first interface, a second interface, an enthalpy-increasing inlet, and an enthalpy-increasing outlet. The first interface is connected to the second interface, and the enthalpy-increasing inlet is connected to the enthalpy-increasing outlet. The first interface is connected to the outdoor heat exchanger (3), and the second interface is connected to the first expansion valve (6) and the second expansion valve (7) respectively. The second expansion valve (7) is connected to the enthalpy-increasing inlet, and the enthalpy-increasing outlet is connected to the enthalpy-increasing intake port.

8. The heat pump system according to claim 7, characterized in that, A shut-off valve is provided at the inlet of the second expansion valve (7).

9. The heat pump system according to claim 8, characterized in that, The economizer (5), the first expansion valve (6) and the second expansion valve (7) are integrated into one unit.

10. A refrigeration unit for refrigerated trucks, characterized in that, Including the heat pump system as described in any one of claims 1 to 9.

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