A heat pump system and a control method thereof

Abstract

The present application relates to the technical field of heat pump, more particularly, to a heat pump system and a control method thereof, the system comprising a compressor, a double pipe heat exchanger, a plate heat exchanger, a first electronic expansion valve, a fin heat exchanger and a gas-liquid separator connected in sequence to form a circulation loop; the plate heat exchanger is provided with a first inlet and a first outlet connected in communication and a second inlet and a second outlet connected in communication, the double pipe heat exchanger is connected with the first inlet, the first outlet is connected with the first electronic expansion valve, the second outlet is connected with a gas supplementing port of the compressor, the gas-liquid separator is further provided with a heat exchange inlet and a heat exchange outlet connected in communication, the double pipe heat exchanger is further connected with the heat exchange inlet, and the first outlet and the heat exchange outlet are connected with the second inlet of the plate heat exchanger through a second electronic expansion valve. In an ultra-low temperature environment, the liquid-phase refrigerant accumulated in the gas-liquid separator exchanges heat with part of the liquid-phase refrigerant led out from the double pipe heat exchanger to change into gas-phase refrigerant, thereby reducing the risk of system liquid return and preventing damage to the compressor caused by liquid hammer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat pumps, and more particularly to a heat pump system and a control method thereof. BACKGROUND

[0002] The evaporative capacity of the finned heat exchanger of a common air source heat pump air conditioning system is attenuated to a relatively low level at an ultra-low ambient temperature, which causes incomplete evaporation of the refrigerant and a part of the refrigerant is still in a liquid phase and accumulated in the gas-liquid separator, resulting in insufficient refrigerant circulation in the system, poor heat pump unit capacity, and even the possibility of liquid return, which causes liquid strike of the compressor and damages the compressor.

[0003] The prior art discloses a heat pump device including a low-temperature heat pump system and a high-temperature heat pump system. The low-temperature heat pump system includes a low-temperature compressor, an intermediate heat exchanger, an economizer, a first liquid accumulator, a first expansion valve, a finned heat exchanger, and a first gas-liquid separator connected in sequence to form a circulation loop. The high-temperature heat pump system includes a high-temperature compressor, a use-side heat exchanger, a second liquid accumulator, a second expansion valve, a heat source-side heat exchanger, and a second gas-liquid separator connected in sequence to form a circulation loop. The intermediate heat exchanger of the low-temperature heat pump system is connected to the heat source-side heat exchanger of the high-temperature heat pump system to provide a heat source for the heat source-side heat exchanger. In this scheme, in the high-temperature heat pump system, the second working medium passes through the heat source-side heat exchanger and exchanges heat with the low-temperature heat pump system before entering the second gas-liquid separator. In the low-temperature heat pump system, although the first working medium flowing out of the intermediate heat exchanger can exchange heat with the economizer to increase the enthalpy of the low-pressure compressor and supplement the gas; however, in a low-temperature environment, the liquid-phase refrigerant accumulated in the first gas-liquid separator still causes insufficient refrigerant circulation in the system and the risk of liquid return. SUMMARY

[0004] The present application aims to overcome the deficiency of the prior art that the gas-liquid separator accumulates liquid-phase refrigerant, which causes the risk of liquid return in the system, and provides a heat pump system and a control method thereof, which convert the liquid-phase refrigerant in the gas-liquid separator into gas-phase refrigerant, reduce the risk of liquid return in the system, and prevent liquid strike of the compressor.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0006] The application provides a heat pump system, which comprises a compressor, a double-pipe heat exchanger, a plate heat exchanger, a first electronic expansion valve, a fin heat exchanger and a gas-liquid separator, the compressor is provided with a high-pressure interface, a low-pressure interface and a gas supplement port, the plate heat exchanger is provided with a first inlet and a first outlet in communication and a second inlet and a second outlet in communication, the high-pressure interface is connected with a refrigerant inlet of the double-pipe heat exchanger, a refrigerant outlet of the double-pipe heat exchanger is connected with the first inlet, the first outlet is connected with a refrigerant inlet of the fin heat exchanger and the second inlet through the first electronic expansion valve and a second electronic expansion valve respectively, the second outlet is connected with the gas supplement port, a refrigerant outlet of the fin heat exchanger is connected with a refrigerant inlet of the gas-liquid separator, and a refrigerant outlet of the gas-liquid separator is connected with the low-pressure interface; the gas-liquid separator is further provided with a heat exchange inlet and a heat exchange outlet in communication, the refrigerant outlet of the double-pipe heat exchanger is further connected with the heat exchange inlet, and the heat exchange outlet is connected with the second inlet through the second electronic expansion valve.

[0007] The heat pump system of the application circulates refrigerant between the compressor, the double-pipe heat exchanger, the plate heat exchanger, the first electronic expansion valve, the fin heat exchanger and the gas-liquid separator to perform heating, wherein the refrigerant enters the plate heat exchanger from the first inlet, part of the refrigerant flowing out of the first outlet enters the plate heat exchanger from the second inlet through the second electronic expansion valve to perform heat exchange and then supplements the compressor through the gas supplement port; meanwhile, in an ultralow-temperature environment, part of liquid refrigerant led out of the refrigerant outlet of the double-pipe heat exchanger can be introduced into the heat exchange inlet of the gas-liquid separator to exchange heat with the accumulated liquid-phase refrigerant, so that the liquid-phase refrigerant in the gas-liquid separator is converted into gas-phase refrigerant, the risk of system liquid return is reduced, and the compressor is prevented from being damaged by liquid hammering; the led-out refrigerant is throttled through the second electronic expansion valve, enters the plate heat exchanger from the second inlet, exchanges heat with part of the refrigerant directly led out of the double-pipe heat exchanger, is vaporized after absorbing heat, and is sprayed into the compressor as enthalpy-increasing gas supplement, so that the refrigerant circulation amount of the system is improved, the unit capacity is improved, and the environmental temperature operation range of the heat pump system is effectively widened.

[0008] Further, the application further comprises a first three-way valve, a second three-way valve and a third three-way valve, the first three-way valve is provided with a first interface, a second interface and a third interface in communication, the second three-way valve is provided with a fourth interface, a fifth interface and a sixth interface in communication, the third three-way valve is provided with a seventh interface, an eighth interface and a ninth interface in communication, the refrigerant outlet of the double-pipe heat exchanger is connected with the first interface, the first inlet is connected with the second interface, the heat exchange inlet is connected with the third interface, the heat exchange outlet is connected with the fourth interface, the fifth interface is connected with the second inlet through the second electronic expansion valve, the sixth interface is connected with the eighth interface, the first outlet is connected with the seventh interface, and the eighth interface is connected with the fin heat exchanger through the first electronic expansion valve.

[0009] Further, the first ball valve, the second ball valve and the third ball valve are further included, the second interface is connected with the heat exchange inlet through the first ball valve, the heat exchange outlet is connected with the fourth interface through the second ball valve, and the eighth interface is connected with the sixth interface through the third ball valve.

[0010] Further, the control system and the temperature monitoring system are further included, the temperature monitoring system is connected with the input end of the control system, and the first ball valve, the second ball valve and the third ball valve are connected with the output end of the control system.

[0011] Further, the temperature monitoring system includes a first temperature sensor for monitoring the temperature of the liquid in the gas-liquid separator, a second temperature sensor for monitoring the temperature of the gas between the gas-liquid separator and the compressor, a third temperature sensor for monitoring the temperature of the finned heat exchanger coil, a fourth temperature sensor for monitoring the ambient temperature, a fifth temperature sensor for monitoring the heat supplement inlet temperature between the first ball valve and the gas-liquid separator, and a sixth temperature sensor for monitoring the heat supplement outlet temperature between the gas-liquid separator and the second ball valve, and the first temperature sensor, the second temperature sensor, the third temperature sensor, the fourth temperature sensor, the fifth temperature sensor and the sixth temperature sensor are connected with the control system.

[0012] Further, the four-way valve is further included, the four-way valve includes a main body, a first port, a second port, a third port and a fourth port, the high-pressure interface is connected with the first port, the refrigerant inlet of the jacket heat exchanger is connected with the second port, the refrigerant outlet of the finned heat exchanger is connected with the third port, and the refrigerant inlet of the gas-liquid separator is connected with the fourth port.

[0013] Further, the first one-way valve, the second one-way valve, the third one-way valve and the fourth one-way valve are further included, the inlet end of the first one-way valve and the outlet end of the second one-way valve are respectively connected with the second interface, the outlet end of the first one-way valve and the outlet end of the third one-way valve are respectively connected with the first inlet, the inlet end of the second one-way valve and the inlet end of the fourth one-way valve are respectively connected with the first electronic expansion valve, and the inlet end of the third one-way valve and the outlet end of the fourth one-way valve are respectively connected with the refrigerant inlet of the finned heat exchanger.

[0014] Further, the frequency conversion board fluorine cold radiator is further included, and the frequency conversion board fluorine cold radiator is arranged between the ninth interface and the first electronic expansion valve.

[0015] The application further provides a control method of the heat pump system, which is applied to the heat pump system, and the method includes a heating mode:

[0016] preset target system heat supplement supercooling degree T 目 ;

[0017] monitoring the temperature T of the liquid in the gas-liquid separator 积 , the return gas temperature T between the gas-liquid separator and the compressor 回 , the finned heat exchanger coil temperature T 盘 , the ambient temperature T 环 , the heat supplement inlet temperature T between the first ball valve and the gas-liquid separator 进 , the heat supplement outlet temperature T between the gas-liquid separator and the second ball valve 出 ;

[0018] calculating the actual system return gas superheat degree T H , T H = T 回 -T 盘 ;

[0019] calculating the actual system heat supplement supercooling degree T C , T C = T 进 -T 出 ;

[0020] adjusting the opening degrees of the first ball valve, the second ball valve and the third ball valve to P A , P B , P C , respectively, according to the ambient temperature T 环 , the temperature T of the liquid in the gas-liquid separator 积 , the actual system return gas superheat degree T H , the actual system heat supplement supercooling degree T C , the target system heat supplement supercooling degree T 目 .

[0021] The control method of the heat pump system of the present application adjusts the opening degrees of the first ball valve, the second ball valve and the third ball valve, and adjusts the refrigerant circulation path and circulation amount by monitoring the temperatures at various positions of the heat pump system and the ambient temperature, in an ultra-low temperature environment, uses part of the liquid refrigerant drawn from the refrigerant outlet of the double-pipe heat exchanger to exchange heat with the liquid-phase refrigerant accumulated in the gas-liquid separator, converts the liquid-phase refrigerant in the gas-liquid separator into gas-phase refrigerant, increases the refrigerant return gas circulation amount, reduces the risk of system return liquid, prevents liquid hammer damage to the compressor, and uses the part of the refrigerant drawn from the double-pipe heat exchanger as the enthalpy-increasing gas supplement for the compressor after heat exchange, thereby increasing the refrigerant circulation amount of the system in an ultra-low temperature environment, improving the unit capacity, and effectively expanding the ambient temperature operating range of the heat pump system.

[0022] Preferably, the process of adjusting the opening degrees of the first ball valve, the second ball valve and the third ball valve is as follows:

[0023] preset minimum opening degree P0, opening degree increasing value P1, first threshold temperature T1, second threshold temperature T2, first threshold time t1, second threshold time t2 of the first ball valve;

[0024] when -12℃ 环 ≤2℃, the first ball valve opening degree P A is 0%, the second ball valve opening degree P B is 0%, and the third ball valve opening degree P C is 100%;

[0025] when T 环 ≤-12℃, the second ball valve opening degree P B is 100%, and the opening degrees of the first ball valve and the third ball valve are controlled by using a logic control; wherein the logic control mode is:

[0026] when T H ≤T1, T 积 ≤T2 and t≥t1, the first ball valve is opened at a preset minimum opening degree P0 and kept;

[0027] after the first ball valve is opened at the minimum opening degree P0, when T H ≤T2, T 积 ≤T2 and t≥t2, the opening degree P A of the first ball valve is P0+P1, and then adjusted according to the difference between the target system heat supplement supercooling degree T 目 and the actual system heat supplement supercooling degree T C ; the opening degree P C of the third ball valve is 1-P A .

[0028] In the formula, t represents the holding time; t1 and t2 are 1min~7min; T1 and T 目 are 0℃~5℃; T2 is -20℃~0℃; and P1 is 5%~100%.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] 1. The part of liquid refrigerant led out from the refrigerant outlet of the double-pipe heat exchanger can be introduced into the heat exchange inlet of the gas-liquid separator to exchange heat with the accumulated liquid-phase refrigerant, so that the liquid-phase refrigerant in the gas-liquid separator is converted into gas-phase refrigerant, the refrigerant circulation amount is increased, the system liquid return risk is reduced, and the compressor liquid strike damage is prevented.

[0031] 2. The led-out refrigerant is throttled by the second electronic expansion valve and then enters the plate heat exchanger from the second inlet to exchange heat with the part of refrigerant directly led out from the double-pipe heat exchanger, is vaporized by heat absorption and then sprayed into the compressor as the enthalpy-increasing supplement gas, so that the system refrigerant circulation amount is increased, the unit capacity is increased, and the environmental temperature operation range of the heat pump system is effectively widened. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Fig. 1 is a structural schematic diagram of a heat pump system in an embodiment of the present application;

[0033] Figure 2 Fig. 2 is a refrigerant circulation schematic diagram in a heating mode in an embodiment of the present application, in which arrows represent the flow direction of refrigerant;

[0034] Figure 3 Fig. 3 is a refrigerant circulation schematic diagram in a cooling mode in an embodiment of the present application, in which arrows represent the flow direction of refrigerant;

[0035] Figure 4 Fig. 4 is a refrigerant circulation schematic diagram in a defrosting mode in an embodiment of the present application, in which arrows represent the flow direction of refrigerant.

[0036] In the drawings: 1 - compressor; 2 - four-way valve; 3 - double-pipe heat exchanger; 4 - plate heat exchanger; 5 - fin heat exchanger; 6 - gas-liquid separator; 7 - first electronic expansion valve; 8 - second electronic expansion valve; 9 - first three-way valve; 10 - second three-way valve; 11 - third three-way valve; 12 - first ball valve; 13 - second ball valve; 14 - third ball valve; 15 - variable-frequency plate fluorine cooling radiator; 16 - first check valve; 17 - second check valve; 18 - third check valve; 19 - fourth check valve; 20 - first filter; 21 - second filter. DETAILED DESCRIPTION

[0037] The present application will be further described below in conjunction with specific embodiments. The drawings are merely used for exemplary illustration, and represent only schematic diagrams, not physical drawings, and should not be understood as limiting the present patent; in order to better illustrate the embodiments of the present application, some components in the drawings can be omitted, enlarged or reduced, and do not represent the actual product size; it is understandable for those skilled in the art that some well-known structures and their descriptions in the drawings can be omitted.

[0038] Embodiment One

[0039] This embodiment is the first embodiment of the heat pump system, as shown in Fig. 1. Figures 1 to 4As shown, the heat pump system comprises a compressor 1, a double-pipe heat exchanger 3, a plate heat exchanger 4, a first electronic expansion valve 7, a fin heat exchanger 5 and a gas-liquid separator 6. The compressor 1 is provided with a high-pressure interface, a low-pressure interface and a gas supplement port. The plate heat exchanger 4 is provided with a first inlet and a first outlet in communication and a second inlet and a second outlet in communication. The high-pressure interface is connected with a refrigerant inlet of the double-pipe heat exchanger 3. A refrigerant outlet of the double-pipe heat exchanger 3 is connected with the first inlet. The first outlet is connected with a refrigerant inlet and a second inlet of the fin heat exchanger 5 through the first electronic expansion valve 7 and a second electronic expansion valve 8 respectively. The second outlet is connected with the gas supplement port. A refrigerant outlet of the fin heat exchanger 5 is connected with a refrigerant inlet of the gas-liquid separator 6. A refrigerant outlet of the gas-liquid separator 6 is connected with the low-pressure interface. The gas-liquid separator 6 is further provided with a heat exchange inlet and a heat exchange outlet in communication. The refrigerant outlet of the double-pipe heat exchanger 3 is further connected with the heat exchange inlet. The heat exchange outlet is connected with the second inlet through the second electronic expansion valve 8.

[0040] The heat pump system described above circulates the refrigerant between the compressor 1, the double-pipe heat exchanger 3, the plate heat exchanger 4, the first electronic expansion valve 7, the fin heat exchanger 5 and the gas-liquid separator 6 to perform heating. The refrigerant enters the plate heat exchanger 4 from the first inlet. Part of the refrigerant flowing out of the first outlet enters the plate heat exchanger 4 from the second inlet through the second electronic expansion valve 8 to perform heat exchange and then supplements the compressor 1 through the gas supplement port. At the same time, in an ultra-low temperature environment, part of the liquid refrigerant led out of the refrigerant outlet of the double-pipe heat exchanger 3 can be introduced into the heat exchange inlet of the gas-liquid separator 6 to exchange heat with the accumulated liquid-phase refrigerant, so as to convert the liquid-phase refrigerant in the gas-liquid separator 6 into gas-phase refrigerant, increase the refrigerant gas circulation amount, reduce the system liquid return risk and prevent the compressor 1 from being damaged by liquid hammer. The refrigerant led out is throttled by the second electronic expansion valve 8 and then enters the plate heat exchanger 4 from the second inlet to exchange heat with part of the refrigerant directly led out of the double-pipe heat exchanger 3. After heat absorption and vaporization, the refrigerant is sprayed into the compressor 1 as enthalpy-increasing gas supplement, so as to increase the system refrigerant circulation amount, improve the unit capacity and effectively expand the environmental temperature operation range of the heat pump system.

[0041] As Figures 1 to 4As shown, it also includes a first three-way valve 9, a second three-way valve 10 and a third three-way valve 11, the first three-way valve 9 is provided with a first interface, a second interface and a third interface in communication, the second three-way valve 10 is provided with a fourth interface, a fifth interface and a sixth interface in communication, the third three-way valve 11 is provided with a seventh interface, an eighth interface and a ninth interface in communication, the refrigerant outlet of the double-pipe heat exchanger 3 is connected with the first interface, the first inlet is connected with the second interface, the heat exchange inlet is connected with the third interface, the heat exchange outlet is connected with the fourth interface, the fifth interface is connected with the second inlet through the second electronic expansion valve 8, the sixth interface is connected with the eighth interface, the first outlet is connected with the seventh interface, and the eighth interface is connected with the fin heat exchanger 5 through the first electronic expansion valve 7. Through the first three-way valve 9, the refrigerant flowing out of the double-pipe heat exchanger 3 can be divided into two paths and introduced into the heat exchange inlet of the gas-liquid separator 6 and the first inlet of the plate heat exchanger 4 respectively for heat exchange; through the third three-way valve 11, the refrigerant introduced from the first outlet can be divided into two paths, one path of the refrigerant is introduced into the second inlet together with the refrigerant after heat exchange from the gas-liquid separator 6 for heat exchange for the enthalpy-increasing gas supplement of the compressor 1, and the other path of the refrigerant enters the fin heat exchanger 5 through the first electronic expansion valve 7 for circulation.

[0042] As shown, Figures 1 to 4 As shown, it also includes a first three-way valve 9, a second three-way valve 10 and a third three-way valve 11, the first three-way valve 9 is provided with a first interface, a second interface and a third interface in communication, the second three-way valve 10 is provided with a fourth interface, a fifth interface and a sixth interface in communication, the third three-way valve 11 is provided with a seventh interface, an eighth interface and a ninth interface in communication, the refrigerant outlet of the double-pipe heat exchanger 3 is connected with the first interface, the first inlet is connected with the second interface, the heat exchange inlet is connected with the third interface, the heat exchange outlet is connected with the fourth interface, the fifth interface is connected with the second inlet through the second electronic expansion valve 8, the sixth interface is connected with the eighth interface, the first outlet is connected with the seventh interface, and the eighth interface is connected with the fin heat exchanger 5 through the first electronic expansion valve 7. Through the first three-way valve 9, the refrigerant flowing out of the double-pipe heat exchanger 3 can be divided into two paths and introduced into the heat exchange inlet of the gas-liquid separator 6 and the first inlet of the plate heat exchanger 4 respectively for heat exchange; through the third three-way valve 11, the refrigerant introduced from the first outlet can be divided into two paths, one path of the refrigerant is introduced into the second inlet together with the refrigerant after heat exchange from the gas-liquid separator 6 for heat exchange for the enthalpy-increasing gas supplement of the compressor 1, and the other path of the refrigerant enters the fin heat exchanger 5 through the first electronic expansion valve 7 for circulation.

[0043] Also included are a control system and a temperature monitoring system, the temperature monitoring system being in communication with an input of the control system, and the first ball valve 12, the second ball valve 13 and the third ball valve 14 being connected to outputs of the control system. Specifically, the temperature monitoring system includes a first temperature sensor for monitoring the temperature of the liquid accumulated in the gas-liquid separator 6, a second temperature sensor for monitoring the temperature of the gas returning between the gas-liquid separator 6 and the compressor 1, a third temperature sensor for monitoring the temperature of the coil of the finned heat exchanger 5, a fourth temperature sensor for monitoring the ambient temperature, a fifth temperature sensor for monitoring the temperature of the heat supplement inlet between the first ball valve 12 and the gas-liquid separator 6, and a sixth temperature sensor for monitoring the temperature of the heat supplement outlet between the gas-liquid separator 6 and the second ball valve 13, the first temperature sensor, the second temperature sensor, the third temperature sensor, the fourth temperature sensor, the fifth temperature sensor and the sixth temperature sensor being in communication with the control system. In implementation, the corresponding temperatures are monitored by the respective temperature sensors and fed back to the control system, and the opening degrees of the first ball valve 12, the second ball valve 13 and the third ball valve 14 are controlled by the control system to adapt to the heat exchange requirements of the liquid-phase refrigerant accumulated in the gas-liquid separator 6 and the enthalpy-increasing supplement gas amount of the compressor 1 in different low-temperature environments, so as to ensure sufficient refrigerant circulation amount in the system and improve the heat pump unit capacity in the ultra-low-temperature environment.

[0044] As shown in Figures 1 to 4 , a frequency conversion board fluorine cold heat sink 15 is further included, which is arranged between the ninth interface and the first electronic expansion valve 7. In implementation, the refrigerant is introduced from the ninth interface to the frequency conversion board fluorine cold heat sink 15 for heat exchange after heat exchange by the plate heat exchanger 4, so as to improve the refrigerant utilization rate and supplement the system heat.

[0045] Embodiment Two

[0046] This embodiment is a second embodiment of the heat pump system, which is similar to the first embodiment, except that, as shown in Figures 1 to 4 , a four-way valve 2 is further included, which includes a main body, a first port, a second port, a third port and a fourth port, the high-pressure interface being connected to the first port, the second port being connected to the refrigerant inlet of the double-pipe heat exchanger 3, the refrigerant outlet of the finned heat exchanger 5 being connected to the third port, and the fourth port being connected to the refrigerant inlet of the gas-liquid separator 6, so as to control the flow direction of the refrigerant circulating loop.

[0047] As shown in Figures 1 to 4As shown, the system also includes a first one-way valve 16, a second one-way valve 17, a third one-way valve 18, and a fourth one-way valve 19. The inlet end of the first one-way valve 16 and the outlet end of the second one-way valve 17 are respectively connected to the second interface. The outlet ends of the first one-way valve 16 and the third one-way valve 18 are respectively connected to the first inlet. The inlet ends of the second one-way valve 17 and the fourth one-way valve 19 are respectively connected to the first electronic expansion valve 7. The inlet ends of the third one-way valve 18 and the outlet ends of the fourth one-way valve 19 are respectively connected to the refrigerant inlet of the finned heat exchanger 5. The arrangement of the first one-way valve 16, the second one-way valve 17, the third one-way valve 18, and the fourth one-way valve 19 restricts the flow direction of the refrigerant, allowing for refrigerant direction switching when the system's operating mode changes, and preventing refrigerant backflow.

[0048] like Figure 2 As shown, in heating mode, the third ball valve 14 is open, and the main circulation path of the refrigerant is: finned heat exchanger 5 - four-way valve 2 - gas-liquid separator 6 - compressor 1 - four-way valve 2 - shell-and-tube heat exchanger 3 - first check valve 16 - plate heat exchanger 4 - variable frequency plate refrigerant radiator 15 - first electronic expansion valve 7 - fourth check valve 19; at the same time, part of the refrigerant flowing out from the first outlet enters the second inlet through the third ball valve 14 and the second electronic expansion valve 8, and after heat exchange in the plate heat exchanger 4, it serves as enthalpy booster gas for compressor 1; in ultra-low temperature environment, the first ball valve 12 and the second ball valve 13 are opened, and part of the refrigerant drawn out from the shell-and-tube heat exchanger 3 exchanges heat with the liquid phase refrigerant accumulated in the gas-liquid separator 6, and together with part of the refrigerant flowing out from the first outlet, enters the second inlet through the second electronic expansion valve 8, and after heat exchange in the plate heat exchanger 4, it serves as enthalpy booster gas for compressor 1;

[0049] like Figure 3 As shown, in cooling mode, the main circulation path of the refrigerant is: shell-and-tube heat exchanger - four-way valve 2 - gas-liquid separator 6 - compressor 1 - four-way valve 2 - finned heat exchanger 5 - third check valve 18 - plate heat exchanger 4 - variable frequency plate refrigerant radiator 15 - first electronic expansion valve 7 - second check valve 17; at the same time, part of the refrigerant flowing out from the first outlet enters the second inlet through the third ball valve 14 and the second electronic expansion valve 8, and after heat exchange in the plate heat exchanger 4, it serves as enthalpy-increasing gas for compressor 1;

[0050] like Figure 4 As shown, in defrost mode, the first ball valve 12, the second ball valve 13, and the third ball valve 14 are all closed, and the refrigerant circulation path is as follows: shell-and-tube heat exchanger - four-way valve 2 - gas-liquid separator 6 - compressor 1 - four-way valve 2 - finned heat exchanger 5 - third check valve 18 - plate heat exchanger 4 - variable frequency plate refrigerant radiator 15 - first electronic expansion valve 7 - second check valve 17.

[0051] like Figures 1 to 4As shown, it further comprises a first filter 20 and a second filter 21, one end of the filter is connected with the second interface of the first three-way valve 9, the inlet end of the first one-way valve 16 and the outlet end of the second one-way valve 17 are respectively connected with the other end of the first filter 20, one end of the second filter 21 is connected with the refrigerant inlet of the finned heat exchanger 5, the inlet end of the third one-way valve 18 and the outlet end of the fourth one-way valve 19 are respectively connected with the other end of the second filter 21, in this embodiment, the impurities in the circulating refrigerant are removed through the first filter 20 and the second filter 21.

[0052] Embodiment three

[0053] This embodiment is the first embodiment of the control method of the heat pump system, which comprises a heating mode:

[0054] The preset target system heat supplement supercooling degree T 目 ;

[0055] The liquid accumulation temperature T 积 in the gas-liquid separator 6, the back gas temperature T 回 between the gas-liquid separator 6 and the compressor 1, the finned heat exchanger 5 coil temperature T 盘 , the ambient temperature T 环 , the heat supplement inlet temperature T 进 between the first ball valve (12) and the gas-liquid separator (6), and the heat supplement outlet temperature T 出 between the gas-liquid separator (6) and the second ball valve (13) are monitored.

[0056] The actual system back gas superheat degree T H is calculated, T H = T 回 -T 盘 ;

[0057] The actual system heat supplement supercooling degree T C is calculated, T C = T 进 -T 出 ;

[0058] According to the ambient temperature T 环 , the liquid accumulation temperature T 积 in the gas-liquid separator 6, the actual system back gas superheat degree T H , the actual system heat supplement supercooling degree T C , and the target system heat supplement supercooling degree T 目 , the opening degrees of the first ball valve 12, the second ball valve 13 and the third ball valve 14 are adjusted to P A , P B , and P C respectively.

[0059] The control method of the heat pump system, by monitoring the temperature of each part of the heat pump system and the ambient temperature, controls the opening degree of the first ball valve 12, the second ball valve 13 and the third ball valve 14, adjusts the refrigerant circulation path and the circulation amount, in the ultra-low temperature environment, uses the part of the liquid refrigerant drawn from the refrigerant outlet of the double pipe heat exchanger 3 to exchange heat with the liquid phase refrigerant accumulated in the gas-liquid separator 6, changes the liquid phase refrigerant in the gas-liquid separator 6 into gas phase refrigerant, increases the refrigerant gas circulation amount, reduces the system liquid return risk, prevents the compressor 1 from being damaged by liquid strike, and after the heat exchange of the part of the refrigerant drawn from the double pipe heat exchanger 3, the part of the refrigerant is used as the enthalpy increase gas supplement of the compressor 1, improves the refrigerant circulation amount of the system in the ultra-low temperature environment, improves the unit capacity, and effectively expands the environmental temperature operation range of the heat pump system.

[0060] The process of adjusting the opening degree of the first ball valve 12, the second ball valve 13 and the third ball valve 14 is as follows:

[0061] The minimum opening degree P0 of the first ball valve 12, the opening degree increase value P1, the first threshold temperature T1, the second threshold temperature T2, the first threshold time t1, the second threshold time t2 are preset;

[0062] When -12℃ 环 ≤2℃, the opening degree P A of the first ball valve 12 is 0%, the opening degree P B of the second ball valve 13 is 0%, and the opening degree P C of the third ball valve 14 is 100%;

[0063] When T 环 ≤-12℃, the opening degree P B of the second ball valve 13 is 100%, and the opening degree of the first ball valve 12 and the third ball valve 14 is controlled by logic; wherein the logic control mode is as follows:

[0064] When T H ≤T1, T 积 ≤T2 and t≥t1, the first ball valve 12 is opened at the preset minimum opening degree P0 and kept;

[0065] After the first ball valve 12 is opened at the minimum opening degree P0, when T H ≤T2, T 积 ≤T2 and t≥t2, the opening degree P A of the first ball valve 12 is P0+P1, and then adjusted according to the difference between the target system heat supplement supercooling degree T 目 and the actual system heat supplement supercooling degree T C ; the opening degree P C of the third ball valve 14 is 1-P A ;

[0066] In the formula, t represents the holding time; t1 and t2 are 1min-7min; T1 and T2 are -12℃-2℃.目 T2 is -20°C to 0°C; and P1 is 5% to 100%.

[0067] In the specific contents of the foregoing specific embodiments, each technical feature can be combined arbitrarily without contradiction. In order to make the description brief, all possible combinations of the foregoing technical features are not described, but as long as the combinations of the technical features do not contradict, they shall be considered as falling within the scope of the present disclosure.

[0068] Obviously, the above-mentioned embodiments of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, it is not necessary and also impossible to exhaust all the implementation modes. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A heat pump system comprising a compressor (1), a double pipe heat exchanger (3), a plate heat exchanger (4), a first electronic expansion valve (7), a fin heat exchanger (5) and a gas-liquid separator (6), the compressor (1) is provided with a high pressure interface, a low pressure interface and a gas supplement port, the plate heat exchanger (4) is provided with a first inlet and a first outlet in communication and a second inlet and a second outlet in communication, the high pressure interface is connected with a refrigerant inlet of the double pipe heat exchanger (3), a refrigerant outlet of the double pipe heat exchanger (3) is connected with the first inlet, the first outlet is connected with a refrigerant inlet of the fin heat exchanger (5) and the second inlet through the first electronic expansion valve (7) and a second electronic expansion valve (8) respectively, the second outlet is connected with the gas supplement port, a refrigerant outlet of the fin heat exchanger (5) is connected with a refrigerant inlet of the gas-liquid separator (6), and a refrigerant outlet of the gas-liquid separator (6) is connected with the low pressure interface; characterized in that, The gas-liquid separator (6) is further provided with a communicating heat exchange inlet and a heat exchange outlet, the refrigerant outlet of the double-pipe heat exchanger (3) is further connected with the heat exchange inlet, and the heat exchange outlet is connected with the second inlet through the second electronic expansion valve (8).

2. The heat pump system of claim 1, wherein, Further comprising a first three-way valve (9), a second three-way valve (10) and a third three-way valve (11), the first three-way valve (9) is provided with a first interface, a second interface and a third interface in communication, the second three-way valve (10) is provided with a fourth interface, a fifth interface and a sixth interface in communication, the third three-way valve (11) is provided with a seventh interface, an eighth interface and a ninth interface in communication, the refrigerant outlet of the double-pipe heat exchanger (3) is connected with the first interface, the first inlet is connected with the second interface, the heat exchange inlet is connected with the third interface, the heat exchange outlet is connected with the fourth interface, the fifth interface is connected with the second inlet through the second electronic expansion valve (8), the sixth interface is connected with the eighth interface, the first outlet is connected with the seventh interface, and the eighth interface is connected with the finned heat exchanger (5) through the first electronic expansion valve (7).

3. The heat pump system of claim 2, wherein, Further comprising a first ball valve (12), a second ball valve (13) and a third ball valve (14), the second interface is connected with the heat exchange inlet through the first ball valve (12), the heat exchange outlet is connected with the fourth interface through the second ball valve (13), and the eighth interface is connected with the sixth interface through the third ball valve (14).

4. The heat pump system of claim 3, wherein, Further comprising a control system and a temperature monitoring system, the temperature monitoring system is communicatively connected with the input end of the control system, and the first ball valve (12), the second ball valve (13) and the third ball valve (14) are respectively connected with the output end of the control system.

5. The heat pump system of claim 4, wherein, The temperature monitoring system comprises a first temperature sensor for monitoring the temperature of liquid accumulation in the gas-liquid separator (6), a second temperature sensor for monitoring the temperature of return gas between the gas-liquid separator (6) and the compressor (1), a third temperature sensor for monitoring the temperature of the coil of the finned heat exchanger (5), a fourth temperature sensor for monitoring the ambient temperature, a fifth temperature sensor for monitoring the temperature of the heat supplement inlet between the first ball valve (12) and the gas-liquid separator (6), and a sixth temperature sensor for monitoring the temperature of the heat supplement outlet between the gas-liquid separator (6) and the second ball valve (13), and the first temperature sensor, the second temperature sensor, the third temperature sensor, the fourth temperature sensor, the fifth temperature sensor and the sixth temperature sensor are respectively communicatively connected with the control system.

6. The heat pump system of claim 5, wherein, Further comprising a four-way valve (2), the four-way valve (2) comprises a main body, a first through port, a second through port, a third through port and a fourth through port, the high-pressure interface is connected with the first through port, the second through port is connected with the refrigerant inlet of the double-pipe heat exchanger (3), the refrigerant outlet of the finned heat exchanger (5) is connected with the third through port, and the fourth through port is connected with the refrigerant inlet of the gas-liquid separator (6).

7. The heat pump system of claim 6, wherein, Further comprising a first one-way valve (16), a second one-way valve (17), a third one-way valve (18) and a fourth one-way valve (19), the inlet end of the first one-way valve (16) and the outlet end of the second one-way valve (17) are respectively communicated with the second interface, the outlet end of the first one-way valve (16) and the outlet end of the third one-way valve (18) are respectively communicated with the first inlet, the inlet end of the second one-way valve (17) and the inlet end of the fourth one-way valve (19) are respectively communicated with the first electronic expansion valve (7), and the inlet end of the third one-way valve (18) and the outlet end of the fourth one-way valve (19) are respectively connected with the refrigerant inlet of the finned heat exchanger (5).

8. The heat pump system according to any one of claims 2 to 7, characterized in that, Further comprising a variable frequency board fluorine cold radiator (15), which is arranged between the ninth interface and the first electronic expansion valve (7).

9. A control method of a heat pump system, characterized by, The method is applied to the heat pump system of any one of claims 3 to 7, and the method comprises a heating mode: Pre-set target system heat supplement supercooling degree T 目 ; Monitoring the temperature of the liquid in the gas-liquid separator (6) T 积 Monitoring the temperature of the return gas between the gas-liquid separator (6) and the compressor (1) T 回 Monitoring the temperature of the coil of the finned heat exchanger (5) T 盘 Monitoring the temperature of the environment T 环 Monitoring the temperature of the heat supply in between the first ball valve (12) and the gas-liquid separator (6) T 进 Monitoring the temperature of the heat supply out between the gas-liquid separator (6) and the second ball valve (13) T 出 ; Calculating actual system gas back heat T H , T H = T 回 - T 盘 ; calculating the actual system subcooling T C , C = T 进 - T 出 ; According to the environmental temperature T 环 , the liquid accumulation temperature T in the gas-liquid separator (6) 积 , the actual system gas return superheat T H , the actual system heat supplement supercooling T C , the target system heat supplement supercooling T 目 , the opening degrees of the first ball valve (12), the second ball valve (13) and the third ball valve (14) are adjusted to P A , P B , P C , respectively.

10. The control method of a heat pump system according to claim 9, characterized by, The process of adjusting the opening degree of the first ball valve (12), the second ball valve (13) and the third ball valve (14) is: The minimum opening degree P0 of the first ball valve (12), the opening degree increase value P1, the first threshold temperature T1, the second threshold temperature T2, the first threshold time t1 and the second threshold time t2 are preset. When -12°C < T 环 ≤ 2°C, first ball valve (12) opening P A = 0%, second ball valve (13) opening P B = 0%, third ball valve (14) opening P C = 100%; When T 环 ≤ -12℃, the second ball valve (13) opening P B = 100%, the opening of the first ball valve (12) and the third ball valve (14) is controlled using logic; wherein the logic control mode is: When T H ≤ T1, T 积 ≤ T2 and t ≥ t1, the first ball valve (12) is opened at a preset minimum opening degree P0 and remains; After the first ball valve (12) is opened to its minimum opening degree P0, when T H ≤T2、T 积 When t ≤ T2 and t ≥ t2, the opening degree P of the first ball valve (12) is... A =P0+P1, then compensate for the subcooling T of the target system. 目 Compared with the actual system heat compensation subcooling T C The differential adjustment; the opening degree P of the third ball valve (14) C =1-P A ; In the formula, t represents the holding time; t1, t2 are 1 min to 7 min; T1, T2 are 0 °C to 5 °C; P1 is 5% to 100%. 目 In the formula, t represents the holding time; t1, t2 are 1 min to 7 min; T1, T2 are 0 °C to 5 °C; P1 is 5% to 100%.

Images