Low-temperature heat pump unit with return air heating function

Abstract

The utility model relates to technical fields especially a low temperature heat pump unit with back gas heating function, which comprises a compressor, a four-way valve, an economizer, a gas-liquid separator, a second heat exchanger, a liquid storage tank and related valves. During the heating cycle, the high-temperature and high-pressure gaseous refrigerant discharged by the compressor is heated in the economizer to increase the supercooling degree and reduce the throttling flash gas; the liquid refrigerant further increases the supercooling degree in the gas-liquid separator and heats the gas-liquid mixed refrigerant in the gas-liquid separator; the liquid refrigerant returns to the liquid storage tank, expands and then enters the second heat exchanger to absorb heat, and the gas-liquid mixed refrigerant in the gas-liquid separator is heated to increase the superheat degree of the compressor inlet, thereby ensuring the low-temperature heating capacity and operation reliability. During the defrosting cycle, the high-temperature and high-pressure gaseous refrigerant enters the second heat exchanger to release heat and defrost, and then returns to the compressor through the economizer and the first heat exchanger, thereby avoiding the influence of frost on heating.

Description

Technical Field

[0001] This utility model relates to the technical field, and in particular to a low-temperature heat pump unit with a return gas heating function. Background Technology

[0002] Against the backdrop of current energy transition and energy conservation and emission reduction, heat pump units are increasingly widely used in the heating sector due to their advantages such as high efficiency and environmental friendliness. Especially in low-temperature environments, heat pump units have become an important equipment choice for achieving clean heating. However, low-temperature environments bring many challenges to the stable operation of heat pump units, among which insufficient system suction superheat is particularly prominent, seriously affecting the reliability and heating efficiency of the unit.

[0003] Suction superheat refers to the difference between the compressor's suction temperature and its saturation temperature at the corresponding evaporation pressure. Appropriate suction superheat ensures that the refrigerant entering the compressor is in a gaseous state, effectively preventing liquid slugging, guaranteeing normal compressor operation, and extending its service life.

[0004] However, in low-temperature environments, the existing heat pump system's loop design lacks an effective mechanism for coordinating regeneration and gas replenishment, resulting in higher compressor discharge temperatures and the return gas easily carrying liquid refrigerant. This reduces the system's suction superheat, which not only restricts the unit's heating capacity but also exacerbates the compressor's operational risks. Utility Model Content

[0005] In order to solve the technical problem of insufficient intake superheat due to the circuit design of heat pump units in low-temperature environments in the prior art, this utility model provides a low-temperature heat pump unit with return gas heating function.

[0006] Therefore, the present invention provides the following technical solution: A low-temperature heat pump unit with return gas heating function includes a compressor, a four-way valve, an economizer, a gas-liquid separator, and a second heat exchanger. The compressor's exhaust port is connected to the first port of the four-way valve via a pipeline. The second port of the four-way valve is connected to the inlet of the first heat exchanger via a pipeline. The outlet of the first heat exchanger is configured with two branches: one branch is connected to the main inlet of the economizer via a pipeline, and the other branch is connected to the auxiliary inlet of the economizer via a pipeline. The auxiliary outlet of the economizer is connected to the compressor's make-up gas inlet via a pipeline. The main outlet of the economizer is configured with two branches: one branch is connected to the liquid inlet of the gas-liquid separator via a pipeline, and the other branch is connected to a liquid storage tank via a pipeline. The main expansion valve is connected to the inlet of the second heat exchanger. A first check valve is installed on the pipeline between the economizer and the liquid storage tank, with the direction of flow into the economizer as the conduction direction. The outlet of the gas-liquid separator is connected to the inlet of the liquid storage tank through a pipeline. A second check valve is installed on the pipeline between the outlet of the gas-liquid separator and the liquid storage tank, with the direction of flow out of the outlet of the gas-liquid separator as the conduction direction. The outlet of the second heat exchanger is connected to the third port of the four-way valve through a pipeline. The fourth port of the four-way valve is connected to the gas inlet of the gas-liquid separator through a pipeline. The gas outlet of the gas-liquid separator is connected to the inlet of the compressor.

[0007] Furthermore, an auxiliary expansion valve is installed on the pipeline between the first heat exchanger and the auxiliary inlet of the economizer.

[0008] Furthermore, the gas-liquid separator includes a cavity, a gas pipe, and a coil. The two ends of the gas pipe are located outside the cavity, and the middle section of the gas pipe is located inside the cavity. The two ends of the coil are located outside the cavity, and the middle section of the coil is located inside the cavity and surrounds the middle section of the gas pipe. The two ends of the gas pipe are respectively provided with a gas pipe inlet and a gas pipe outlet. The two ends of the coil are respectively provided with a liquid inlet and a liquid outlet.

[0009] Furthermore, the air pipe is provided with pressure equalization holes.

[0010] Furthermore, the trachea has an oil return hole on the tube wall near the bottom of the cavity.

[0011] Advantages and positive effects of this utility model: During the heating cycle, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor is condensed in the first heat exchanger and then enters the economizer. After heat exchange in the economizer, the subcooling is increased, which reduces flash gas in the subsequent throttling process and ensures that the refrigerant in the second heat exchanger fully absorbs heat. The condensed liquid refrigerant flows through the economizer into the gas-liquid separator to heat the refrigerant gas entering the compressor before flowing back to the liquid receiver. After passing through the main expansion valve, it enters the second heat exchanger. The second heat exchanger absorbs heat from the external environment and allows the gaseous refrigerant to be heated by the gas-liquid separator before entering the compressor. In actual applications of low-temperature heat pumps, the low ambient temperature often leads to insufficient superheat, and the refrigerant exits the second heat exchanger in a gas-liquid mixed state. This design of heating in the gas-liquid separator ensures that the refrigerant returning to the compressor has sufficient superheat, improving the reliability of low-temperature operation.

[0012] During the defrost cycle, the high-temperature, high-pressure gaseous refrigerant discharged from the compressor enters the second heat exchanger. The second heat exchanger releases heat to remove condensation from its surface. Subsequently, the gaseous refrigerant flows out from the second heat exchanger, passing sequentially through the main expansion valve, the liquid receiver, the economizer, and the first heat exchanger before entering the compressor. This avoids the impact of condensation on the heating cycle.

[0013] By allowing the auxiliary refrigerant to be heat-exchanged by the economizer before being introduced into the compressor's gas inlet, the compressor's discharge temperature can be reduced, preventing damage to the compressor due to high temperatures and extending its service life. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This utility model provides a pipeline connection diagram for a low-temperature heat pump unit with return gas heating function.

[0016] Figure 2 This utility model provides an internal structural diagram of a gas-liquid separator for a low-temperature heat pump unit with a return gas heating function.

[0017] Figure 3 A top view of a gas-liquid separator for a low-temperature heat pump unit with a return gas heating function provided by this utility model.

[0018] 1. Compressor; 2. Four-way valve; 3. First heat exchanger; 4. Gas replenishment circuit pipeline; 5. Auxiliary expansion valve; 6. Economizer; 7. First check valve; 8. Liquid storage tank; 9. Main expansion valve; 10. Second check valve; 11. Second heat exchanger; 12. Gas-liquid separator; 13. Gas pipe; 14. Gas pipe inlet; 15. Gas pipe outlet; 16. Coil; 17. Liquid inlet; 18. Liquid outlet; 19. Pressure equalization hole; 20. Cavity; 21. Oil return hole. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0020] This utility model provides a low-temperature heat pump unit with return gas heating function, such as Figure 1 As shown, the system includes a compressor 1, a four-way valve 2, an economizer 6, a gas-liquid separator 12, and a second heat exchanger 11. The exhaust port of the compressor 1 is connected to the first port of the four-way valve 2 via a pipeline. The second port of the four-way valve 2 is connected to the inlet of the first heat exchanger 3 via a pipeline. The outlet of the first heat exchanger 3 is divided into two paths: one path is connected to the main inlet of the economizer 6 via a pipeline, and the other path is connected to the auxiliary inlet of the economizer 6 via a pipeline. An auxiliary expansion valve 5 is installed on the pipeline between the first heat exchanger 3 and the auxiliary inlet of the economizer 6. The auxiliary outlet of the economizer 6 is connected to the gas supply inlet of the compressor 1 via a gas supply loop pipeline 4.

[0021] The main outlet of the economizer 6 is divided into two routes: one route is connected to the inlet 17 of the gas-liquid separator 12 via a pipeline, and the other route is connected to the inlet of the second heat exchanger 11 via a pipeline through the storage tank 8 and the main expansion valve 9. A first check valve 7 is installed on the pipeline between the economizer 6 and the storage tank 8, and the first check valve 7 is open in the direction of flow into the economizer 6. The outlet 18 of the gas-liquid separator 12 is connected to the inlet of the storage tank 8 via a pipeline. A second check valve 10 is installed on the pipeline between the outlet 18 of the gas-liquid separator 12 and the storage tank 8, and the second check valve 10 is open in the direction of flow out of the outlet of the gas-liquid separator 12.

[0022] The outlet of the second heat exchanger is connected to the third port of the four-way valve 2 via a pipeline. The fourth port of the four-way valve 2 is connected to the gas inlet 14 of the gas-liquid separator 12 via a pipeline. The gas outlet 15 of the gas-liquid separator 12 is connected to the gas inlet of the compressor 1. A first check valve 7 is installed on the main pipeline of the economizer 6.

[0023] like Figures 2-3 As shown, the gas-liquid separator 12 includes a cavity 20, a gas pipe 13, and a coil 16. The two ends of the gas pipe 13 are located outside the cavity 20, and the middle section of the gas pipe 13 is located inside the cavity 20. The two ends of the coil 16 are located outside the cavity 20, and the middle section of the coil 16 is located inside the cavity 20 and surrounds the middle section of the gas pipe 13. The two ends of the gas pipe 13 are respectively provided with a gas pipe inlet 14 and a gas pipe outlet 15. The two ends of the coil 16 are respectively provided with a liquid inlet 17 and a liquid outlet 18. The gas pipe 13 is provided with a pressure equalization hole 19; the gas pipe 13 has an oil return hole 21 on its wall near the bottom of the cavity.

[0024] Working principle: During the heating cycle, compressor 1 draws in low-temperature, low-pressure gaseous refrigerant and compresses it into high-temperature, high-pressure gaseous refrigerant, which is discharged from the exhaust port and enters the first port of four-way valve 2 through the pipeline; the refrigerant switches to the heating flow direction through four-way valve 2 and is discharged from the second port to the inlet of the first heat exchanger 3; the high-temperature, high-pressure refrigerant releases heat and condenses in the first heat exchanger 3, transforming into medium-temperature, high-pressure liquid refrigerant, which flows out from the outlet of the first heat exchanger and splits into two paths.

[0025] A portion of the liquid refrigerant at the outlet of the first heat exchanger 3 flows through the auxiliary expansion valve 5, where it is throttled and depressurized into a low-temperature, low-pressure gas-liquid mixture, and enters the auxiliary inlet of the economizer 6. Inside the economizer 6, this portion of refrigerant absorbs heat from the main refrigerant and completely evaporates into a low-temperature, low-pressure gaseous refrigerant, which is then discharged from the economizer's auxiliary outlet and fed into the compressor 1's replenishment inlet via the replenishment gas circuit pipe 4, thereby reducing the compressor's exhaust temperature and increasing its heating capacity.

[0026] Another portion of the liquid refrigerant at the outlet of the first heat exchanger 3 directly enters the main inlet of the economizer 6. Inside the economizer, it is cooled by the auxiliary refrigerant, increasing the subcooling and becoming a low-temperature, high-pressure liquid refrigerant, which flows out from the main outlet of the economizer. Controlled by the shut-off of the first one-way valve 7, the refrigerant flows through the pipeline into the inlet 17 of the gas-liquid separator 12, and flows out from the outlet 18 through the internal coil 16 into the liquid storage tank 8. Although the first one-way valve 7 is open in the direction of flow into the economizer 6, the pressure on the outlet side of the first one-way valve 7 is greater than the pressure on the inlet side, so the refrigerant will not enter the economizer 6 through the first one-way valve 7.

[0027] The refrigerant enters the liquid storage tank 8, where it temporarily stores the liquid refrigerant and balances the refrigerant flow under different operating conditions of the system, avoiding flow instability caused by load fluctuations. Then it flows through the main expansion valve 9. The main expansion valve 9 reduces the pressure of the low-temperature, high-pressure liquid refrigerant to a low-temperature, low-pressure gas-liquid mixture through precise throttling, and finally delivers it to the second heat exchanger 11.

[0028] The low-temperature, low-pressure gas-liquid mixture of refrigerant entering the second heat exchanger 11 exchanges heat with the ambient air through the heat exchange tube bundle inside the second heat exchanger 11. Even in low-temperature environments, thanks to the main path subcooling increased by the economizer 6 in the early stage of the system, throttling flashover is reduced and heat exchange efficiency is ensured, so it can still efficiently absorb heat from the air. During this process, the refrigerant gradually evaporates into a gaseous state, eventually forming a low-temperature, low-pressure gas-liquid mixture containing a small amount of unevaporated liquid refrigerant. This small amount of liquid refrigerant will be separated in the subsequent gas-liquid separator to prevent it from entering the compressor.

[0029] After evaporation, the refrigerant becomes a low-temperature, low-pressure gaseous refrigerant, which flows out from the outlet of the second heat exchanger 3 and enters the third port of the four-way valve 2 through the pipeline. The refrigerant evaporated into a gaseous state in the second heat exchanger 11 is discharged through the fourth port of the four-way valve 2 and enters the gas pipe 13 from the gas pipe inlet 14 of the gas-liquid separator 12. In the cavity 20, the liquid refrigerant in the coil 16 continuously releases heat, heating the gas-liquid mixture in the cavity 20. The gas pipe 13 is provided with a pressure equalization hole 19 to balance the pressure inside and outside the gas pipe. Due to the low temperature and reduced flow rate, the oil in the gaseous refrigerant is deposited at the bottom of the cavity 20 and flows back into the gas pipe 13 through the oil return hole 21, moving together with the refrigerant in the gas pipe 13. After being heated to achieve gas-liquid separation, the gaseous refrigerant is discharged from the gas pipe 13 outlet 15 and finally enters the inlet of the compressor 1, preventing the liquid refrigerant from entering the compressor.

[0030] During the defrost cycle, the path direction of the four-way valve 2 is switched, allowing the high-temperature, high-pressure refrigerant discharged from the compressor 1 to enter the second heat exchanger 11 through the pipeline. The heat exchange tube bundle inside the second heat exchanger 11 releases heat to the external environment, defrosting the surface of the second heat exchanger 11. The gaseous refrigerant inside the second heat exchanger 11 sequentially passes through the first one-way valve 7, the economizer 6, and the first heat exchanger 3 before entering the compressor 1 to complete the defrost cycle. At this time, the first heat exchanger 3 absorbs heat from the outside air, increasing the superheat of the gaseous refrigerant entering the compressor 1. Since the second one-way valve 10 is oriented with the outflow direction of the liquid outlet of the gas-liquid separator 12 as the conduction direction, the refrigerant will not enter the gas-liquid separator 12 through the second one-way valve 10.

[0031] After a period of heating cycle, frost will form on the surface of the second heat exchanger 11, at which point a defrosting cycle is required. In actual operation, for example, after every 1 hour of heating cycle, a 5-minute defrosting cycle is performed, and so on. The defrosting time is not a fixed value and is generally adjusted according to the actual situation.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A low-temperature heat pump unit with return gas heating function, characterized in that, The system includes a compressor (1), a four-way valve (2), an economizer (6), a gas-liquid separator (12), and a second heat exchanger (11). The exhaust port of the compressor (1) is connected to the first port of the four-way valve (2) via a pipeline. The second port of the four-way valve (2) is connected to the inlet of the first heat exchanger (3) via a pipeline. The outlet of the first heat exchanger (3) is divided into two paths: one path is connected to the main inlet of the economizer (6) via a pipeline, and the other path is connected to the auxiliary inlet of the economizer (6) via a pipeline. The auxiliary outlet of the economizer (6) is connected to the gas supply inlet of the compressor (1) via a pipeline. The main outlet of the economizer (6) is divided into two paths: one path is connected to the liquid inlet (17) of the gas-liquid separator (12) via a pipeline, and the other path is connected to the inlet of the second heat exchanger (11) via a pipeline through the liquid storage tank (8) and the main expansion valve (9). Next, a first check valve (7) is installed on the pipeline between the economizer (6) and the storage tank (8). The first check valve (7) is directed in the direction of flow into the economizer (6). The outlet (18) of the gas-liquid separator (12) is connected to the inlet of the storage tank (8) through a pipeline. A second check valve (10) is installed on the pipeline between the outlet (18) of the gas-liquid separator (12) and the storage tank (8). The second check valve (10) is directed in the direction of flow out of the outlet of the gas-liquid separator (12). The outlet of the second heat exchanger (11) is connected to the third interface of the four-way valve (2) through a pipeline. The fourth interface of the four-way valve (2) is connected to the gas inlet (14) of the gas-liquid separator (12) through a pipeline. The gas outlet (15) of the gas-liquid separator (12) is connected to the inlet of the compressor (1).

2. A low-temperature heat pump unit with return gas heating function according to claim 1, characterized in that, An auxiliary expansion valve (5) is installed on the pipeline between the auxiliary inlet of the first heat exchanger (3) and the economizer (6).

3. A low-temperature heat pump unit with return gas heating function according to claim 1, characterized in that, The gas-liquid separator (12) includes a cavity (20), a duct (13), and a coil (16). The two ends of the duct (13) are located outside the cavity (20), and the middle section of the duct (13) is located inside the cavity (20). The two ends of the coil (16) are located outside the cavity (20), and the middle section of the coil (16) is located inside the cavity (20) and is arranged around the middle section of the duct (13). The two ends of the duct (13) are respectively provided with a duct inlet (14) and a duct outlet (15). The two ends of the coil (16) are respectively provided with a liquid inlet (17) and a liquid outlet (18).

4. A low-temperature heat pump unit with return gas heating function according to claim 3, characterized in that, The air pipe (13) is provided with a pressure equalization hole (19).

5. A low-temperature heat pump unit with return gas heating function according to claim 3, characterized in that, The trachea (13) has an oil return hole (21) on the tube wall near the bottom of the cavity (20).

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