Heat pump system and control method thereof

Abstract

The invention relates to the technical field of heat pumps, in particular to a heat pump system and a control method thereof.The system comprises a compressor, a double-pipe heat exchanger, a plate heat exchanger, a first electronic expansion valve, a finned heat exchanger and a gas-liquid separator which are sequentially communicated to form a circulation loop; the plate heat exchanger is provided with a first inlet and a first outlet which are communicated with each other and a second inlet and a second outlet which are communicated with each other, the double-pipe heat exchanger is connected with the first inlet, the first outlet is connected with the first electronic expansion valve, and the second outlet is connected with an air supply port of the compressor; 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 a second inlet of the plate heat exchanger through a second electronic expansion valve. In the ultralow temperature environment, the liquid-phase refrigerant accumulated in the gas-liquid separator exchanges heat with part of the liquid-phase refrigerant led out of the double-pipe heat exchanger to be converted into the gas-phase refrigerant, the liquid return risk of the system is reduced, and the compressor is prevented from being damaged by liquid impact.

Description

Technical Field

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

[0002] In common air source heat pump air conditioning systems, the evaporation capacity of the finned heat exchanger decays to a relatively low level under ultra-low ambient temperatures, which makes the refrigerant not evaporate completely. A part of the refrigerant is still in liquid form and accumulates in the gas-liquid separator, resulting in insufficient refrigerant circulation in the system, poor heat pump unit capacity, and even liquid backflow, causing liquid hammer in the compressor and damaging 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 reservoir, a first expansion valve, a fin heat exchanger and a first gas-liquid separator that are sequentially connected to form a circulation loop. The high-temperature heat pump system includes a high-temperature compressor, a user-side heat exchanger, a second liquid reservoir, a second expansion valve, a heat source-side heat exchanger and a second gas-liquid separator that are sequentially connected 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 fluid enters the second gas-liquid separator after heat exchange with the low-temperature heat pump system through the heat source-side heat exchanger; and in the low-temperature heat pump system, although the first working fluid flowing out of the intermediate heat exchanger can increase the enthalpy and replenish the air of the low-pressure compressor through heat exchange with the economizer; however, in a low-temperature environment, the accumulation of liquid phase refrigerant in the first gas-liquid separator still leads to insufficient refrigerant circulation in the system, and there is a risk of liquid return. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiency of the prior art that the liquid refrigerant accumulates in the gas-liquid separator, resulting in the risk of liquid backflow in the system, and to provide a heat pump system and a control method thereof, so as to convert the liquid refrigerant in the gas-liquid separator into gas-phase refrigerant, reduce the risk of liquid backflow in the system, and prevent liquid hammer damage to the compressor.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A heat pump system is provided, comprising a compressor, a shell and tube heat exchanger, a plate heat exchanger, a first electronic expansion valve, a fin heat exchanger and a gas-liquid separator, wherein the compressor is provided with a high-pressure interface, a low-pressure interface and an air supply port, the plate heat exchanger is provided with a first inlet and a first outlet that are connected, and a second inlet and a second outlet that are connected, the high-pressure interface is connected to the refrigerant inlet of the shell and tube heat exchanger, the refrigerant outlet of the shell and tube heat exchanger is connected to the first inlet, the first outlet is connected to the refrigerant inlet and the second inlet of the fin heat exchanger respectively through the first electronic expansion valve and the second electronic expansion valve, the second outlet is connected to the air supply port, the refrigerant outlet of the fin heat exchanger is connected to the refrigerant inlet of the gas-liquid separator, and the refrigerant outlet of the gas-liquid separator is connected to the low-pressure interface; the gas-liquid separator is also provided with a connected heat exchange inlet and a heat exchange outlet, the refrigerant outlet of the shell and tube heat exchanger is also connected to the heat exchange inlet, and the heat exchange outlet is connected to the second inlet through the second electronic expansion valve.

[0007] In the heat pump system of the present invention, the refrigerant circulates between the compressor, the shell and tube heat exchanger, the plate heat exchanger, the first electronic expansion valve, the fin heat exchanger and the gas-liquid separator to generate heat, wherein the refrigerant enters the plate heat exchanger from the first inlet, and part of the refrigerant flowing out from the first outlet enters the plate heat exchanger from the second inlet through the second electronic expansion valve for heat exchange, and then replenishes air to the compressor through the air replenishment port; at the same time, in an ultra-low temperature environment, part of the liquid refrigerant drawn out from the refrigerant outlet of the shell and tube heat exchanger can be introduced into the gas-liquid separator The heat exchange inlet exchanges heat with the accumulated liquid refrigerant, converting the liquid refrigerant in the gas-liquid separator into gas refrigerant, reducing the risk of liquid return in the system and preventing liquid hammer damage to the compressor. The drawn-out refrigerant enters the plate heat exchanger from the second inlet after being throttled by the second electronic expansion valve, exchanges heat with part of the refrigerant directly drawn out from the shell-and-tube heat exchanger, absorbs heat and vaporizes, and is sprayed into the compressor as enthalpy-increasing supplementary air, thereby increasing the system refrigerant circulation volume, improving the unit capacity, and effectively widening the ambient temperature operating range of the heat pump system.

[0008] Furthermore, it also includes 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 that are connected, the second three-way valve is provided with a fourth interface, a fifth interface and a sixth interface that are connected, the third three-way valve is provided with a seventh interface, an eighth interface and a ninth interface that are connected, the refrigerant outlet of the shell and tube heat exchanger is connected to the first interface, the first inlet is connected to the second interface, the heat exchange inlet is connected to the third interface, the heat exchange outlet is connected to the fourth interface, the fifth interface is connected to the second inlet through the second electronic expansion valve, the sixth interface is connected to the eighth interface, the first outlet is connected to the seventh interface, and the eighth interface is connected to the fin heat exchanger through the first electronic expansion valve.

[0009] Furthermore, it also includes a first ball valve, a second ball valve and a third ball valve, the second interface is connected to the heat exchange inlet through the first ball valve, the heat exchange outlet is connected to the fourth interface through the second ball valve, and the eighth interface is connected to the sixth interface through the third ball valve.

[0010] Furthermore, it also includes a control system and a temperature monitoring system, the temperature monitoring system is communicatively connected to the input end of the control system, and the first ball valve, the second ball valve and the third ball valve are respectively connected to the output end of the control system.

[0011] Furthermore, the temperature monitoring system includes a first temperature sensor for monitoring the temperature of accumulated liquid in the gas-liquid separator, a second temperature sensor for monitoring the return air temperature between the gas-liquid separator and the compressor, a third temperature sensor for monitoring the coil temperature of the finned heat exchanger, a fourth temperature sensor for monitoring the ambient temperature, a fifth temperature sensor for monitoring the supplementary heat inlet temperature between the first ball valve and the gas-liquid separator, and a sixth temperature sensor for monitoring the supplementary heat outlet temperature between the gas-liquid separator and the second ball valve. 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 connected to the control system for communication.

[0012] Furthermore, it also includes a four-way valve, which includes a main body, a first port, a second port, a third port and a fourth port, the high-pressure interface is connected to the first port, the second port is connected to the refrigerant inlet of the shell and tube heat exchanger, the refrigerant outlet of the fin heat exchanger is connected to the third port, and the fourth port is connected to the refrigerant inlet of the gas-liquid separator.

[0013] Furthermore, it also includes a first one-way valve, a second one-way valve, a third one-way valve and a fourth one-way valve, the inlet end of the first one-way valve and the outlet end of the second one-way valve are respectively connected to 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 to 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 to 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 to the refrigerant inlet of the fin-type heat exchanger.

[0014] Furthermore, it also includes a frequency conversion board fluorine cooling radiator, and the frequency conversion board fluorine cooling radiator is arranged between the ninth interface and the first electronic expansion valve.

[0015] The present invention also provides a control method for a heat pump system, which is applied to the above-mentioned heat pump system. The method includes a heating mode:

[0016] Preset target system heat compensation subcooling degree T 目 ;

[0017] Monitor the accumulated liquid temperature T in the gas-liquid separator 积 , the return air temperature between the gas-liquid separator and the compressor T 回 , finned heat exchanger coil temperature T 盘 、Ambient temperature T 环 , the heat inlet temperature between the first ball valve and the gas-liquid separator T 进 , the heat supply outlet temperature between the gas-liquid separator and the second ball valve T 出 ;

[0018] Calculate the actual system return air superheat T H , T H =T 回 -T 盘 ;

[0019] Calculate the actual system heat supplement subcooling T C , T C =T 进 -T 出 ;

[0020] According to the ambient temperature T 环 , the accumulated liquid temperature in the gas-liquid separator T 积 , Actual system return air superheat T H 、Actual system heat supplement subcooling degree T C 、Target system heat supplement subcooling degree T 目 , adjust the opening of the first ball valve, the second ball valve and the third ball valve to P respectively A , P B , P C .

[0021] The control method of the heat pump system of the present invention monitors the temperature and ambient temperature of various parts of the heat pump system, controls the opening of the first ball valve, the second ball valve and the third ball valve, and adjusts the refrigerant circulation path and circulation volume. In an ultra-low temperature environment, a portion of the liquid refrigerant drawn out from the refrigerant outlet of the shell and tube heat exchanger is used to perform heat exchange on the liquid refrigerant accumulated in the gas-liquid separator, and the liquid refrigerant in the gas-liquid separator is converted into a gas-phase refrigerant, thereby increasing the refrigerant return gas circulation volume, reducing the risk of system liquid return, and preventing compressor liquid hammer damage. Part of the refrigerant drawn out from the shell and tube heat exchanger is used as the enthalpy increase air supply of the compressor after heat exchange, thereby increasing the refrigerant circulation volume of the system in an ultra-low temperature environment, improving the unit capacity, and effectively widening the ambient temperature operating range of the heat pump system.

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

[0023] Preset the minimum opening degree P0, 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 of the first ball valve;

[0024] When -12℃ <T 环 ≤2℃, opening of the first ball valve P A is 0%, the second ball valve opening P B is 0%, the third ball valve opening P C is 100%;

[0025] When T 环 ≤-12℃, second ball valve opening P B The opening of the first ball valve and the third ball valve is 100%, and the opening of the first ball valve and the third ball valve is controlled by logic; wherein the logic control method is:

[0026] When T H ≤T1, T 积 When t≤T2 and t≥t1, the first ball valve opens and maintains at the preset minimum opening P0;

[0027] After the first ball valve is opened at the minimum opening P0, when T H ≤T2, T 积 ≤T2 and t≥t2, the opening of the first ball valve P A =P0+P1, then according to the target system heat supplement subcooling degree T 目 Compared with the actual system heat compensation subcooling T C The difference adjustment; the opening of the third ball valve P C =1-P A ;

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

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

[0030] 1. Part of the liquid refrigerant drawn out from the refrigerant outlet of the shell-and-tube heat exchanger can be introduced into the heat exchange inlet of the gas-liquid separator to exchange heat with the accumulated liquid refrigerant, so as to convert the liquid refrigerant in the gas-liquid separator into gas refrigerant, increase the refrigerant return gas circulation volume, reduce the risk of liquid return in the system, and prevent liquid shock damage to the compressor;

[0031] 2. The refrigerant is throttled by the second electronic expansion valve and then enters the plate heat exchanger from the second inlet to exchange heat with part of the refrigerant directly drawn from the shell-and-tube heat exchanger. After absorbing heat and vaporizing, it is sprayed into the compressor as enthalpy-increasing supplementary air, thereby increasing the system refrigerant circulation volume, improving the unit capacity, and effectively widening the ambient temperature operating range of the heat pump system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of a heat pump system in an embodiment of the present invention;

[0033] Figure 2 Schematic diagram of refrigerant circulation in heating mode in an embodiment of the present invention, in which arrows indicate the flow direction of the refrigerant;

[0034] Figure 3 Schematic diagram of refrigerant circulation in cooling mode in an embodiment of the present invention, in which arrows indicate the flow direction of the refrigerant;

[0035] Figure 4 Schematic diagram of refrigerant circulation in defrost mode in an embodiment of the present invention, in which arrows indicate the flow direction of the refrigerant.

[0036] In the attached figure: 1- compressor; 2- four-way valve; 3- shell and tube heat exchanger; 4- plate heat exchanger; 5- finned 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- frequency conversion board fluorine cooling radiator; 16- first one-way valve; 17- second one-way valve; 18- third one-way valve; 19- fourth one-way valve; 20- first filter; 21- second filter. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0038] Embodiment 1

[0039] This embodiment is the first embodiment of the heat pump system. Figures 1 to 4As shown, it includes a compressor 1, a shell and tube heat exchanger 3, a plate heat exchanger 4, a first electronic expansion valve 7, a finned heat exchanger 5 and a gas-liquid separator 6. The compressor 1 is provided with a high-pressure interface, a low-pressure interface and an air supply port. The plate heat exchanger 4 is provided with a first inlet and a first outlet that are connected and a second inlet and a second outlet that are connected. The high-pressure interface is connected to the refrigerant inlet of the shell and tube heat exchanger 3, and the refrigerant outlet of the shell and tube heat exchanger 3 is connected to the first inlet. The first outlet is connected to the refrigerant inlet and the second inlet of the finned heat exchanger 5 through the first electronic expansion valve 7 and the second electronic expansion valve 8 respectively, and the second outlet is connected to the air supply port. The refrigerant outlet of the finned heat exchanger 5 is connected to the refrigerant inlet of the gas-liquid separator 6, and the refrigerant outlet of the gas-liquid separator 6 is connected to the low-pressure interface; the gas-liquid separator 6 is also provided with a connected heat exchange inlet and a heat exchange outlet, the refrigerant outlet of the shell and tube heat exchanger 3 is also connected to the heat exchange inlet, and the heat exchange outlet is connected to the second inlet through the second electronic expansion valve 8.

[0040] In the above-mentioned heat pump system, the refrigerant circulates between the compressor 1, the shell and tube heat exchanger 3, the plate heat exchanger 4, the first electronic expansion valve 7, the finned heat exchanger 5 and the gas-liquid separator 6 for heating, wherein the refrigerant enters the plate heat exchanger 4 from the first inlet, and part of the refrigerant flowing out from the first outlet enters the plate heat exchanger 4 from the second inlet through the second electronic expansion valve 8 for heat exchange, and then replenishes air to the compressor 1 through the air replenishment port; at the same time, in an ultra-low temperature environment, part of the liquid refrigerant drawn out from the refrigerant outlet of the shell and tube heat exchanger 3 can be introduced into the exchange port of the gas-liquid separator 6. The hot inlet exchanges heat with the accumulated liquid refrigerant, converting the liquid refrigerant in the gas-liquid separator 6 into gas refrigerant, increasing the refrigerant return gas circulation volume, reducing the risk of system liquid return, and preventing liquid hammer damage to the compressor 1; and the drawn-out refrigerant enters the plate heat exchanger 4 from the second inlet after throttling by the second electronic expansion valve 8, exchanges heat with part of the refrigerant directly drawn out from the shell and tube heat exchanger 3, absorbs heat and vaporizes, and is sprayed into the compressor 1 as enthalpy-increasing supplementary air, thereby increasing the system refrigerant circulation volume, improving the unit capacity, and effectively widening the ambient temperature operating range of the heat pump system.

[0041] like 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 that are connected. The second three-way valve 10 is provided with a fourth interface, a fifth interface and a sixth interface that are connected. The third three-way valve 11 is provided with a seventh interface, an eighth interface and a ninth interface that are connected. The refrigerant outlet of the shell-and-tube heat exchanger 3 is connected to the first interface, the first inlet is connected to the second interface, the heat exchange inlet is connected to the third interface, the heat exchange outlet is connected to the fourth interface, the fifth interface is connected to the second inlet through the second electronic expansion valve 8, the sixth interface is connected to the eighth interface, the first outlet is connected to the seventh interface, and the eighth interface is connected to the finned heat exchanger 5 through the first electronic expansion valve 7. Through the first three-way valve 9, the refrigerant flowing out of the shell and tube heat exchanger 3 can be divided into two paths, which are respectively led to the heat exchange inlet of the gas-liquid separator 6 and the first inlet of the plate heat exchanger 4 for heat exchange; through the third three-way valve 11, the refrigerant led out from the first outlet can be divided into two paths, one refrigerant is introduced into the second inlet through the second three-way valve 10 together with the refrigerant after heat exchange from the gas-liquid separator 6 for heat exchange for compressor 1 to increase enthalpy and replenish air, and the other refrigerant enters the finned heat exchanger 5 through the first electronic expansion valve 7 for circulation.

[0042] like Figures 1 to 4 As shown, it also includes a first ball valve 12, a second ball valve 13 and a third ball valve 14. The second interface is connected to the heat exchange inlet through the first ball valve 12, the heat exchange outlet is connected to the fourth interface through the second ball valve 13, and the eighth interface is connected to the sixth interface through the third ball valve 14. When the first ball valve 12 and the second ball valve 13 are closed and the third ball valve 14 is opened, part of the refrigerant flowing out of the first outlet can be led out to enter the second inlet for heat exchange as enthalpy-increasing air replenishment for the compressor 1, thereby increasing the refrigerant circulation volume of the system; when the system is operated in an ultra-low temperature environment, the first ball valve 12 and the second ball valve 13 are opened, and part of the refrigerant is led out from the shell-and-tube heat exchanger 3 through the first ball valve 12 to perform heat exchange with the liquid-phase refrigerant accumulated in the gas-liquid separator 6, thereby converting the liquid-phase refrigerant in the gas-liquid separator 6 into a refrigerant. It is converted into gas-phase refrigerant, which increases the refrigerant return air circulation volume, reduces the risk of system liquid return, and prevents liquid hammer damage to the compressor 1. At the same time, by controlling the opening of the first ball valve 12 and the third ball valve 14, the amount of refrigerant used for heat exchange with the liquid-phase refrigerant accumulated in the gas-liquid separator 6 can be controlled to meet the heat exchange requirements under different ultra-low temperature environments; the refrigerant after heat exchange enters the second inlet through the second ball valve 13 and the second electronic expansion valve 8, and after heat exchange, it can be used as enthalpy-increasing air supply for the compressor 1 to supplement the system refrigerant circulation volume.

[0043] It also includes a control system and a temperature monitoring system. The temperature monitoring system is communicatively connected to the input end of the control system. The first ball valve 12, the second ball valve 13 and the third ball valve 14 are respectively connected to the output end of the control system. Specifically, the temperature monitoring system includes a first temperature sensor for monitoring the temperature of the accumulated liquid in the gas-liquid separator 6, a second temperature sensor for monitoring the return air temperature between the gas-liquid separator 6 and the compressor 1, a third temperature sensor for monitoring the coil temperature of the finned heat exchanger 5, a fourth temperature sensor for monitoring the ambient temperature, a fifth temperature sensor for monitoring the supplementary heat inlet temperature between the first ball valve 12 and the gas-liquid separator 6, and a sixth temperature sensor for monitoring the supplementary heat outlet temperature 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 are respectively communicatively connected to the control system. During implementation, the corresponding temperature is monitored by each temperature sensor and fed back to the control system. The opening 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 refrigerant accumulated in the gas-liquid separator 6 under different low-temperature environments and the enthalpy increase and air supply of the compressor 1, thereby ensuring sufficient refrigerant circulation in the system and improving the capacity of the heat pump unit under ultra-low temperature environments.

[0044] like Figures 1 to 4 As shown, the inverter board fluorine cooling radiator 15 is also included, and the inverter board fluorine cooling radiator 15 is arranged between the ninth interface and the first electronic expansion valve 7. During implementation, the refrigerant is led out from the ninth interface to the inverter board fluorine cooling radiator 15 for heat exchange after heat exchange through the plate heat exchanger 4, thereby improving the utilization rate of the refrigerant and supplementing the system heat.

[0045] Embodiment 2

[0046] This embodiment is a second embodiment of the heat pump system. This embodiment is similar to the first embodiment, except that: Figures 1 to 4 As shown, it also includes a four-way valve 2, which includes a main body, a first port, a second port, a third port and a fourth port. The high-pressure interface is connected to the first port, the second port is connected to the refrigerant inlet of the shell-and-tube heat exchanger 3, the refrigerant outlet of the fin heat exchanger 5 is connected to the third port, and the fourth port is connected to the refrigerant inlet of the gas-liquid separator 6, so as to control the flow direction of the refrigerant circulation loop.

[0047] like Figures 1 to 4As shown, 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 are also included. 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 end of the first one-way valve 16 and the outlet end of the third one-way valve 18 are respectively connected to 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 connected to the refrigerant inlet of the finned heat exchanger 5. Through 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, the flow direction of the refrigerant can be restricted. When the system working mode changes, the refrigerant direction can be switched and the refrigerant backflow can be prevented.

[0048] like Figure 2 As shown, in the heating mode, the third ball valve 14 is opened, and the main circulation flow path of the refrigerant is: fin heat exchanger 5-four-way valve 2-gas-liquid separator 6-compressor 1-four-way valve 2-tube heat exchanger 3-first non-return valve 16-plate heat exchanger 4-frequency conversion plate fluorine cooling radiator 15-first electronic expansion valve 7-fourth non-return valve 19; at the same time, part of the refrigerant flowing out of the first outlet enters the second inlet through the third ball valve 14 and the second electronic expansion valve 8, and is used as the enthalpy increase air supply of the compressor 1 after heat exchange in the plate heat exchanger 4; in the 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 tube heat exchanger 3 exchanges heat with the liquid phase refrigerant accumulated in the gas-liquid separator 6, and enters the second inlet together with part of the refrigerant flowing out from the first outlet through the second electronic expansion valve 8, and is used as the enthalpy increase air supply of the compressor 1 after heat exchange in the plate heat exchanger 4;

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

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

[0051] like Figures 1 to 4As shown, it also includes a first filter 20 and a second filter 21, one end of the filter is connected to 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 to the other end of the first filter 20, one end of the second filter 21 is connected to 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 to the other end of the second filter 21. In this embodiment, impurities in the circulating refrigerant are removed by the first filter 20 and the second filter 21.

[0052] Embodiment 3

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

[0054] Preset target system heat compensation subcooling degree T 目 ;

[0055] Monitor the accumulated liquid temperature T in the gas-liquid separator 6 积 , the return air temperature T between the gas-liquid separator 6 and the compressor 1 回 、Fin heat exchanger 5 coil temperature T 盘 、Ambient temperature T 环 , the heat supply temperature T between the first ball valve (12) and the gas-liquid separator (6) 进 , the heat supply outlet temperature T between the gas-liquid separator (6) and the second ball valve (13) 出 ;

[0056] Calculate the actual system return air superheat T H , T H =T 回 -T 盘 ;

[0057] Calculate the actual system heat supplement subcooling T C , T C =T 进 -T 出 ;

[0058] According to the ambient temperature T 环 , the accumulated liquid temperature T in the gas-liquid separator 6 积 , Actual system return air superheat T H , Actual system heat supplement subcooling degree T C 、Target system heat supplement subcooling degree T 目 , adjust the openings of the first ball valve 12, the second ball valve 13 and the third ball valve 14 to P respectively A , P B , P C .

[0059] The control method of the above-mentioned heat pump system monitors the temperature and ambient temperature of various parts of the heat pump system, controls the opening of the first ball valve 12, the second ball valve 13 and the third ball valve 14, and adjusts the refrigerant circulation path and circulation volume. In an ultra-low temperature environment, part of the liquid refrigerant drawn out from the refrigerant outlet of the shell and tube heat exchanger 3 is used to perform heat exchange on the liquid refrigerant accumulated in the gas-liquid separator 6, and the liquid refrigerant in the gas-liquid separator 6 is converted into a gas-phase refrigerant, thereby increasing the refrigerant return air circulation volume, reducing the risk of system liquid return, and preventing liquid hammer damage to the compressor 1. Part of the refrigerant drawn out from the shell and tube heat exchanger 3 is used as the enthalpy increase air supply of the compressor 1 after heat exchange, thereby increasing the refrigerant circulation volume of the system in an ultra-low temperature environment, improving the unit capacity, and effectively widening the ambient temperature operating range of the heat pump system.

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

[0061] Preset the minimum opening degree P0, 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 of the first ball valve 12;

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

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

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

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

[0066] Where, t represents the holding time; t1 and t2 are 1 min to 7 min; T1, T目 It is 0℃~5℃; T2 is -20℃~0℃; P1 is 5%~100%.

[0067] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A heat pump system, comprising a compressor (1), a shell and tube heat exchanger (3), a plate heat exchanger (4), a first electronic expansion valve (7), a finned heat exchanger (5) and a gas-liquid separator (6), wherein the compressor (1) is provided with a high-pressure interface, a low-pressure interface and a gas supply port, the plate heat exchanger (4) is provided with a first inlet and a first outlet that are connected, and a second inlet and a second outlet that are connected, the high-pressure interface is connected to the refrigerant inlet of the shell and tube heat exchanger (3), the refrigerant outlet of the shell and tube heat exchanger (3) is connected to the first inlet, the first outlet is connected to the refrigerant inlet and the second inlet of the finned heat exchanger (5) through the first electronic expansion valve (7) and the second electronic expansion valve (8), respectively, the second outlet is connected to the gas supply port, the refrigerant outlet of the finned heat exchanger (5) is connected to the refrigerant inlet of the gas-liquid separator (6), and the refrigerant outlet of the gas-liquid separator (6) is connected to the low-pressure interface; characterized in that The gas-liquid separator (6) is also provided with a heat exchange inlet and a heat exchange outlet which are connected to each other. The refrigerant outlet of the shell-and-tube heat exchanger (3) is also connected to the heat exchange inlet. The heat exchange outlet is connected to the second inlet via the second electronic expansion valve (8).

2. The heat pump system according to claim 1, characterized in that: It also includes a first three-way valve (9), a second three-way valve (10) and a third three-way valve (11), wherein the first three-way valve (9) is provided with a first interface, a second interface and a third interface that are connected, the second three-way valve (10) is provided with a fourth interface, a fifth interface and a sixth interface that are connected, and the third three-way valve (11) is provided with a seventh interface, an eighth interface and a ninth interface that are connected, the refrigerant outlet of the shell-and-tube heat exchanger (3) is connected to the first interface, the first inlet is connected to the second interface, the heat exchange inlet is connected to the third interface, the heat exchange outlet is connected to the fourth interface, the fifth interface is connected to the second inlet through the second electronic expansion valve (8), the sixth interface is connected to the eighth interface, the first outlet is connected to the seventh interface, and the eighth interface is connected to the finned heat exchanger (5) through the first electronic expansion valve (7).

3. The heat pump system according to claim 2, characterized in that: The heat exchanger further comprises a first ball valve (12), a second ball valve (13) and a third ball valve (14); the second interface is connected to the heat exchange inlet through the first ball valve (12); the heat exchange outlet is connected to the fourth interface through the second ball valve (13); and the eighth interface is connected to the sixth interface through the third ball valve (14).

4. The heat pump system according to claim 3, characterized in that: It also includes a control system and a temperature monitoring system, wherein the temperature monitoring system is communicatively connected to 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 to the output end of the control system.

5. The heat pump system according to claim 4, characterized in that: The temperature monitoring system comprises a first temperature sensor for monitoring the temperature of accumulated liquid in the gas-liquid separator (6), a second temperature sensor for monitoring the return air temperature between the gas-liquid separator (6) and the compressor (1), a third temperature sensor for monitoring the coil temperature of the finned heat exchanger (5), a fourth temperature sensor for monitoring the ambient temperature, a fifth temperature sensor for monitoring the supplementary heat inlet temperature between the first ball valve (12) and the gas-liquid separator (6), and a sixth temperature sensor for monitoring the supplementary heat outlet temperature 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 are respectively connected to the control system for communication.

6. The heat pump system according to claim 5, characterized in that: It also includes a four-way valve (2), which includes a main body, a first port, a second port, a third port and a fourth port, the high-pressure interface is connected to the first port, the second port is connected to the refrigerant inlet of the shell-and-tube heat exchanger (3), the refrigerant outlet of the fin-type heat exchanger (5) is connected to the third port, and the fourth port is connected to the refrigerant inlet of the gas-liquid separator (6).

7. The heat pump system according to claim 6, characterized in that: It 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), wherein 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 end of the first one-way valve (16) and the outlet end of the third one-way valve (18) are respectively connected to 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 connected to 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 to 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: It also includes a frequency conversion board fluorine cooling radiator (15), and the frequency conversion board fluorine cooling radiator (15) is arranged between the ninth interface and the first electronic expansion valve (7).

9. A control method for a heat pump system, characterized in that: Applicable to the heat pump system according to any one of claims 3 to 7, the method comprising a heating mode: Preset target system heat compensation subcooling degree T 目 ; Monitor the accumulated liquid temperature T in the gas-liquid separator (6) 积 , the return air temperature T between the gas-liquid separator (6) and the compressor (1) 回 、Fin heat exchanger (5) coil temperature T 盘 、Ambient temperature T 环 , the heat supply temperature T between the first ball valve (12) and the gas-liquid separator (6) 进 , the heat supply outlet temperature T between the gas-liquid separator (6) and the second ball valve (13) 出 ; Calculate the actual system return air superheat T H , T H =T 回 -T 盘 ; Calculate the actual system heat supplement subcooling T C , T C =T 进 -T 出 ; According to the ambient temperature T 环 , the accumulated liquid temperature T in the gas-liquid separator (6) 积 , Actual system return air superheat T H , Actual system heat supplement subcooling degree T C 、Target system heat supplement subcooling degree T 目 , adjust the openings of the first ball valve (12), the second ball valve (13) and the third ball valve (14) to P respectively A , P B , P C .

10. The control method of the heat pump system according to claim 9, characterized in that: The process of adjusting the opening of the first ball valve (12), the second ball valve (13) and the third ball valve (14) is as follows: Presetting the minimum opening degree P0, 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 of the first ball valve (12); When -12℃ <T 环 ≤2℃, opening degree of the first ball valve (12) P A is 0%, the opening degree of the second ball valve (13) is P B is 0%, the opening degree of the third ball valve (14) is P C is 100%; When T 环 ≤-12℃, opening degree of the second ball valve (13) P B The opening of the first ball valve (12) and the third ball valve (14) is 100%, and the opening of the first ball valve (12) and the third ball valve (14) is controlled by logic; wherein the logic control method is: When T H ≤T1, T 积 When t≤T2 and t≥t1, the first ball valve (12) is opened and maintained at a preset minimum opening degree P0; After the first ball valve (12) is opened at the minimum opening P0, when T H ≤T2, T 积 ≤T2 and t≥t2, the opening degree P of the first ball valve (12) A =P0+P1, then according to the target system heat supplement subcooling degree T 目 Compared with the actual system heat compensation subcooling T C The difference adjustment; the opening degree P of the third ball valve (14) C =1-P A ; Where, t represents the holding time; t1 and t2 are 1 min to 7 min; T1, T 目 It is 0℃~5℃; T2 is -20℃~0℃; P1 is 5%~100%.

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