An air source heat pump air conditioning system

Abstract

The present application relates to an air source heat pump air conditioning system, through monitoring the supercooling degree and / or the back gas superheating degree of the system in the refrigeration and heating mode of the system, using a flow control valve module to draw a branch liquid refrigerant from the system condenser liquid pipe (air side heat exchanger in refrigeration, water side heat exchanger in heating) to enter the gas-liquid separator for heat exchange, adjusting the opening of the flow control valve on both sides of the gas-liquid separator to further adjust the flow of the heat exchange branch refrigerant flowing out of the gas-liquid separator, and the heat exchange branch refrigerant mixes with the main path refrigerant which does not exchange heat in the condensing liquid pipe to enter the electronic expansion valve for throttling. The system can ensure that the supercooling degree of the mixed refrigerant before flowing through the electronic expansion valve meets the requirements, thereby maintaining the refrigerating capacity of the evaporator. The system effectively solves the problems of poor compressor oil return and liquid refrigerant entering the compressor causing compressor liquid strike caused by the increase of the viscosity of the refrigeration oil and the low miscibility of the refrigeration oil in the low temperature and ultra-low ambient temperature working conditions.

Description

Technical Field

[0001] This invention relates to the field of heat pump air conditioning, and in particular to an air source heat pump air conditioning system. Background Technology

[0002] In cooling mode, air source heat pump air conditioning systems require a certain degree of subcooling to maintain a low dryness of the two-phase refrigerant reaching the evaporator in order to meet the evaporation capacity of the evaporator. Existing technologies improve the subcooling by increasing the effective heat exchange area of ​​the finned heat exchanger, designing a subcooling section for the finned heat exchanger, or reducing the opening of the electronic expansion valve in the refrigerant circuit. This, in turn, increases the liquid refrigerant percentage reaching the evaporator to some extent, thereby improving the cooling capacity. When the unit operates under harsh conditions such as low temperature or ultra-low ambient temperature, the evaporation capacity of the air-side heat exchanger (fins) decreases, causing more and more liquid refrigerant to accumulate in the gas-liquid separator. Excessive liquid refrigerant will directly enter the compressor and cause liquid slugging, resulting in irreversible damage to the compressor. At the same time, due to the increased kinematic viscosity of the refrigeration oil, it is easy to clog the oil return hole, causing oil blockage and poor oil return to the compressor. On the other hand, the refrigeration oil separates from the liquid refrigerant, with the refrigeration oil floating on the liquid refrigerant. Since the oil return hole is at the bottom of the gas-liquid separator, this further exacerbates the difficulty of oil return to the compressor, causing the compressor to operate with insufficient oil and affecting its service life. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to provide an air source heat pump air conditioning system.

[0004] The detailed technical solution of the air source heat pump air conditioning system of the present invention is as follows:

[0005] An air-source heat pump air conditioning system includes a compressor, a four-way valve, a water-side heat exchanger, a gas-liquid separator, an air-side heat exchanger, a control valve module, a connecting valve module, and a temperature detection module, all connected via refrigerant piping. A controller is electrically and / or communicatively connected to the control valve module and the temperature detection module. The control valve module includes a first flow control valve, a second flow control valve, a third flow control valve, a fourth flow control valve, a fifth flow control valve, and an electronic expansion valve. The connecting valve module includes several three-way valves. The controller, through the control valve module, ensures the refrigerant maintains the following flow path relationship:

[0006] In cooling mode, the refrigerant flowing out of the air-side heat exchanger is divided into refrigeration branch refrigerant and refrigeration main refrigerant by the first three-way valve after passing through the third flow control valve. The refrigeration branch refrigerant enters the gas-liquid separator through the first flow control valve. Based on the system subcooling and return gas superheat, the flow rate of the heat exchange refrigeration branch refrigerant flowing out of the gas-liquid separator is controlled by the opening and closing of the second flow control valve. The heat exchange refrigeration branch refrigerant mixes with the refrigeration main refrigerant and then enters the water-side heat exchanger through the electronic expansion valve. During this period, the fourth flow control valve is closed to prevent the heat exchange refrigeration branch refrigerant from directly entering the water-side heat exchanger, and the fifth flow control valve is closed to prevent the mixed refrigerant regulated by the electronic expansion valve from entering the air-side heat exchanger.

[0007] In heating mode, the refrigerant flowing out of the water-side heat exchanger is divided into heating branch refrigerant and heating main refrigerant by the second three-way valve. The heating branch refrigerant enters the gas-liquid separator via the fourth flow control valve. Based on the system subcooling or return gas superheat, the flow rate of the heat exchange heating branch refrigerant flowing out of the gas-liquid separator is controlled by the opening and closing of the first flow control valve. After passing through the first three-way valve, the heat exchange heating branch refrigerant mixes with the heating main refrigerant and is then regulated by the electronic expansion valve before entering the air-side heat exchanger via the fifth flow control valve. During this period, the second flow control valve is closed, allowing the heating branch refrigerant to enter only the gas-liquid separator, and the third flow control valve is closed, preventing the heat exchange heating branch refrigerant from directly entering the air-side heat exchanger.

[0008] Furthermore, in cooling mode, the controller controls the flow rate of refrigerant in the heat exchange cooling branch exiting the gas-liquid separator in the following manner:

[0009] S21 controls the opening degree of the first flow control valve and the third flow control valve to the maximum opening degree;

[0010] S22 obtains the coil temperature T p Supercooling temperature T e and return gas temperature T hq According to the coil temperature T p With supercooling temperature T e The difference is used to obtain the system subcooling ΔT, based on the return gas temperature T. hq With coil temperature T p The difference is used to obtain the return gas superheat ΔT hg And compare the system subcooling ΔT with the set refrigeration subcooling threshold ΔT. C TV ΔT return gas superheat hg With the set return gas superheat threshold Relationship:

[0011] If the system subcooling ΔT is less than or equal to the refrigeration subcooling threshold ΔT C TV And the return gas superheat ΔThg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set first duration threshold t1 TV Then control the second flow control valve to its minimum opening degree K. 2-MIN Start and proceed to step S23;

[0012] In other cases, the second flow control valve should be closed.

[0013] S23 continuously acquires the coil temperature T′ after the second flow control valve opens. p Supercooling temperature T′ e and return gas temperature T′ hq According to the coil temperature T′ p With supercooling temperature T′ e The difference is used to obtain the system subcooling Δ′T, based on the return gas temperature T′. hq With coil temperature T′ p The difference is used to obtain the return gas superheat ΔT′ hg And compare the system subcooling Δ′T with the refrigeration subcooling threshold ΔT. C TV ΔT′ of return gas superheat hg With return gas superheat threshold Relationship:

[0014] If the system subcooling Δ′T is less than or equal to the refrigeration subcooling threshold ΔT C TV And the return gas superheat ΔT′ hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set second duration threshold t2 TV The opening degree of the second flow control valve is controlled at the minimum opening degree K. 2-MIN Based on this, the valve opening is increased by ΔK1, and the valve remains unadjusted for the first time period t′1, followed by PID control.

[0015] In other cases, the opening degree of the second flow control valve is controlled at the minimum opening degree K. 2-MIN .

[0016] Furthermore, the fine-tuning opening ΔK1 satisfies:

[0017] ΔK1=α*K 2-MAX

[0018] In the formula, K 2-MAX This indicates the maximum opening degree of the second flow control valve, and α represents the weighting coefficient, with a value range of 0.05 to 0.80.

[0019] Furthermore, the cooling subcooling threshold ΔT CTV The value range is -5℃ to 10℃, and the return gas superheat threshold is... The value range is -3℃ to 5℃.

[0020] Furthermore, the first duration threshold t1 TV The value range is 1 min to 5 min; the second duration threshold t2 TV The value range is 1 min to 5 min.

[0021] Furthermore, in heating mode, the controller controls the flow rate of refrigerant in the heat exchange heating branch exiting the gas-liquid separator in the following manner:

[0022] S31 controls the opening degree of the fourth and fifth flow control valves to the maximum opening degree;

[0023] S32 obtains the coil temperature T p Supercooling temperature T e According to the coil temperature T p With supercooling temperature T e The system subcooling ΔT is obtained by measuring the temperature difference; and the system subcooling ΔT is compared with the set heating subcooling threshold ΔT. H TV Relationship:

[0024] If the system subcooling ΔT is less than or equal to the heating subcooling threshold ΔT H TV And the duration t is greater than or equal to the set third duration threshold t3 TV Then control the first flow control valve to its minimum opening degree K. 1-MIN Start and proceed to step S33;

[0025] In other cases, the first flow control valve shall be closed.

[0026] S33 continuously acquires the coil temperature T′ after the first flow control valve opens. p Supercooling temperature T′ e According to the coil temperature T′ p With supercooling temperature T′ e The difference is used to obtain the system subcooling Δ′T, and the system subcooling Δ′T is compared with the heating subcooling threshold ΔT. H TV Relationship:

[0027] If the system subcooling Δ′T is less than or equal to the heating subcooling threshold ΔT H TV And the duration t is greater than or equal to the set fourth duration threshold t4. TV Further obtain the ambient temperature T h According to the ambient temperature Th The compensation opening degree corresponding to the temperature range is used to compensate for the minimum opening degree to obtain the corrected minimum opening degree K′ of the first flow control valve. 1-MIN Control the first flow control valve to correct the minimum opening degree K′ 1-MIN During the second time period t′2, the valve is not adjusted, and then PID control is applied.

[0028] In other cases, the opening degree of the first flow control valve is controlled at the minimum opening degree K. 1-MIN .

[0029] Furthermore, the minimum opening degree K′ of the first flow control valve is corrected. 1-MIN satisfy:

[0030] K′ 1-MIN =K 1-MIN +ΔK h

[0031] In the formula, K 1-MIN ΔK represents the minimum opening degree of the first flow control valve. h This represents the compensation opening degree related to ambient temperature, where ΔK h Depending on the ambient temperature range, its value satisfies:

[0032] When -10℃ < T h When the temperature is ≤2℃, the compensation opening ΔK h =5%*K 1-MAX ;

[0033] When -15℃ < T h When the temperature is ≤-10℃, the compensation opening ΔK h =8%*K 1-MAX ;

[0034] When -20℃ < T h When the temperature is ≤-15℃, the compensation opening ΔK h =10%*K 1-MAX ;

[0035] When -25℃ < T h When the temperature is ≤-20℃, the compensation opening ΔK h =15%*K 1-MAX ;

[0036] When T h At temperatures below -25℃, the compensation opening ΔK h =20%*K 1-MAX ;

[0037] Among them, K 1-MAX T represents the maximum opening degree of the first flow control valve. h Indicates ambient temperature.

[0038] Furthermore, in heating mode, the controller controls the flow rate of refrigerant in the heat exchange heating branch exiting the gas-liquid separator in the following manner:

[0039] S31 controls the opening degree of the fourth and fifth flow control valves to the maximum opening degree;

[0040] S`32 obtains the coil temperature T p Return gas temperature T hq According to the return gas temperature T hq With coil temperature T p The temperature difference is used to obtain the superheat of the return gas ΔT hg And compare the return gas superheat ΔT hg With the set return gas superheat threshold Relationship:

[0041] If the return gas superheat ΔT hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set third duration threshold t3 TV Then control the first flow control valve to its minimum opening degree K. 1-MIN Start and execute step S`33;

[0042] In other cases, the first flow control valve shall be closed.

[0043] S`33 continuously acquires the coil temperature T′ after the first flow control valve opens. p Return gas temperature T′ hq According to the return gas temperature T′ hq With coil temperature T′ p The difference is used to obtain the return gas superheat Δ′T hg And compare the return gas superheat ΔT′ hg With return gas superheat threshold Relationship:

[0044] If the return gas superheat ΔT′ hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set fourth duration threshold t4 TV Further obtain the ambient temperature T h According to the ambient temperature T h The compensation opening degree corresponding to the temperature range is used to compensate for the minimum opening degree to obtain the corrected minimum opening degree K′ of the first flow control valve. 1-MIN Control the first flow control valve to correct the minimum opening degree K′ 1-MIN During the second time period t′2, the valve is not adjusted, and then PID control is applied.

[0045] In other cases, the opening degree of the first flow control valve is controlled at the minimum opening degree K.1-MIN .

[0046] Furthermore, it also includes a defrost mode, in which the controller, through the control valve module, ensures that the refrigerant meets the following flow path relationship:

[0047] The refrigerant flowing out of the air-side heat exchanger is divided into a first branch refrigerant and a second branch refrigerant after passing through the third three-way valve. The first branch refrigerant passes through the third flow control valve, the first three-way valve, and the electronic expansion valve in sequence, and then mixes with the second branch refrigerant that has passed through the fifth flow control valve. After mixing, it enters the water-side heat exchanger after passing through the second three-way valve. During this process, the first flow control valve is closed to prevent the first branch refrigerant from entering the gas-liquid separator, the second flow control valve is closed to prevent the first branch refrigerant from entering the gas-liquid separator, and the fourth flow control valve is closed to prevent the mixed refrigerant from entering the gas-liquid separator.

[0048] Among them, the third and fifth flow control valves are fully open, and the opening of the electronic expansion valve is adjusted to a fixed defrost opening until defrosting is completed.

[0049] Compared to existing technologies, the air-source heat pump air conditioning system of this invention, in both cooling and heating modes, monitors the system's subcooling and / or return gas superheat. A flow control valve module draws liquid refrigerant from the system's condenser liquid line (air-side heat exchanger during cooling, water-side heat exchanger during heating) into a gas-liquid separator for heat exchange. The flow rate of the refrigerant exiting the gas-liquid separator is adjusted by regulating the opening of the flow control valves on both sides of the separator. This heat exchange refrigerant mixes with the main refrigerant in the condenser line that has not undergone heat exchange before entering the electronic expansion valve for throttling. This system ensures that the subcooling of the mixed refrigerant before passing through the electronic expansion valve meets requirements, thus maintaining the evaporator's cooling capacity. This system effectively solves the problems of increased system refrigerant oil viscosity and low refrigerant miscibility leading to poor compressor refrigerant oil return under low and ultra-low ambient temperature conditions; and the problem of insufficient evaporation in the evaporator causing liquid refrigerant to enter the compressor and cause liquid slugging.

[0050] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the air source heat pump air conditioning system of this application;

[0052] Figure 2 This is a schematic diagram showing the flow of refrigerant and the opening and closing of the control valve module in cooling mode.

[0053] Figure 3 This is a schematic diagram showing the flow of refrigerant and the opening and closing of the control valve module in heating mode.

[0054] Figure 4This is a schematic diagram showing the flow of refrigerant and the opening and closing of the control valve module in defrost mode.

[0055] Figure 5 This is a flowchart illustrating the method for controlling subcooling in a heat pump air conditioning system.

[0056] Labeling Explanation: 10-Compressor, 20-Four-way valve, 30-Water-side heat exchanger, 40-Gas-liquid separator, 50-Control valve module, 501-First flow control valve, 502-Second flow control valve, 503-Third flow control valve, 504-Fourth flow control valve, 505-Fifth flow control valve, 52-Electronic expansion valve, 60-Air-side heat exchanger, 70-Temperature detection module, 71-First temperature sensor, 72-Second temperature sensor Sensors, 73-Third temperature sensor, 74-Fourth temperature sensor, 80-Connecting valve module, 811-First three-way valve, 812-Second three-way valve, 813-Third three-way valve, 814-Fourth three-way valve, 815-Fifth three-way valve, 816-Sixth three-way valve, 817-Seventh three-way valve, 818-Eighth three-way valve, 821-First check valve, 822-Second check valve, 823-Third check valve, 824-Fourth check valve. Detailed Implementation

[0057] Existing air source heat pump air conditioning systems use a method of reducing the opening of the electronic expansion valve controlling the refrigerant circuit to increase the subcooling of the system in order to meet the evaporation capacity of the evaporator. However, in low and ultra-low temperature environments, even if the opening of the electronic expansion valve in the refrigerant circuit is adjusted to the minimum value of the preset opening adjustment range, the actual evaporation temperature of the refrigerant is still low, and the heat absorption and evaporation of the refrigerant decreases. This results in a much smaller amount of gaseous refrigerant returning to the compressor compared to non-low or non-ultra-low temperature conditions. A large amount of refrigerant accumulates in the gas-liquid separator and finned heat exchanger of the system in liquid form. At this time, the system cannot accurately control the subcooling of the system by adjusting the opening of the electronic expansion valve, which leads to more and more liquid refrigerant accumulating in the gas-liquid separator. Excessive liquid refrigerant will directly enter the compressor for compression, causing liquid slugging and irreversible damage to the compressor. At the same time, under low or ultra-low temperature conditions, on the one hand, the kinematic viscosity of the refrigeration oil increases, which easily clogs the oil return hole and causes oil blockage, resulting in poor oil return to the compressor. On the other hand, the refrigeration oil separates from the liquid refrigerant, with the refrigeration oil floating on the liquid refrigerant. Since the oil return hole is at the bottom of the gas-liquid separator, this further aggravates the difficulty of oil return to the compressor, causing the compressor to operate without oil and affecting its service life.

[0058] Therefore, this invention studies existing methods for improving subcooling in air conditioning systems and discovers that by leading the refrigerant out of the condenser liquid line and exchanging heat with the two-phase refrigerant-compressor oil mixture in the gas-liquid separator, the subcooling of the refrigerant before it flows through the electronic expansion valve can be guaranteed. Based on this, this invention redesigns an air-source heat pump air conditioning system. In cooling and heating modes, this system monitors the system's subcooling and / or return gas superheat. A flow control valve module leads a branch of liquid refrigerant from the system's condenser liquid line (air-side heat exchanger in cooling mode, water-side heat exchanger in heating mode) into the gas-liquid separator for heat exchange. By adjusting the opening of the flow control valves on both sides of the gas-liquid separator, the flow rate of the refrigerant flowing out of the heat exchange branch is regulated. This heat exchange branch refrigerant mixes with the main refrigerant and enters the electronic expansion valve for throttling, thereby ensuring that the system's subcooling is within a certain range. This effectively solves the problems of liquid slugging in the compressor and poor compressor refrigerant oil return caused by liquid refrigerant entering the compressor.

[0059] For specific implementation details, please refer to [link / reference]. Figure 1 The heat pump air conditioning system of this application includes a compressor 10, a four-way valve 20, a water-side heat exchanger 30, a gas-liquid separator 40, a control valve module 50, an air-side heat exchanger 60, a temperature detection module 70, a connecting valve module 80, a controller (not shown), and other auxiliary pipe fittings. The compressor 10, four-way valve 20, water-side heat exchanger 30, gas-liquid separator 40, control valve module 50, air-side heat exchanger 60, and connecting valve module 80 are connected via refrigerant piping to form a refrigerant circulation loop for cooling and heating. The controller is electrically and / or communicatively connected to the control valve module 50 and the temperature detection module 70.

[0060] The control valve module 50 includes a first flow control valve 501, a second flow control valve 502, a third flow control valve 503, a fourth flow control valve 504, a fifth flow control valve 505, and an electronic expansion valve 52. The flow control valves can be ball valves, electromagnetic flow valves, pressure reducing and load reducing valves, shut-off valves, or butterfly check valves; this application does not impose any restrictions, as long as they have the function of controlling fluid flow.

[0061] The connecting valve module 80 includes a first three-way valve 811, a second three-way valve 812, a third three-way valve 813, a fourth three-way valve 814, a fifth three-way valve 815, a sixth three-way valve 816, a seventh three-way valve 817, and an eighth three-way valve 818, as well as a first one-way valve 821, a second one-way valve 822, a third one-way valve 823, and a fourth one-way valve 824.

[0062] In cooling mode, the refrigerant flowing from the air-side heat exchanger 30 is divided into a cooling branch refrigerant and a main cooling branch refrigerant by the first three-way valve 811 after passing through the third flow control valve 503. The cooling branch refrigerant enters the gas-liquid separator 40 via the first flow control valve 501. Based on the system subcooling and return gas superheat, the flow rate of the heat exchange cooling branch refrigerant flowing from the gas-liquid separator 40 is controlled by the opening and closing of the second flow control valve 502. After mixing with the main cooling branch refrigerant, the mixture enters the water-side heat exchanger 30 via the electronic expansion valve 52. During this process, the fourth flow control valve 504 closes to prevent the heat exchange cooling branch refrigerant from directly entering the water-side heat exchanger 30, and the fifth flow control valve 505 closes to prevent the mixed refrigerant regulated by the electronic expansion valve 52 from entering the air-side heat exchanger. 60; In heating mode, the refrigerant flowing out of the water-side heat exchanger 30 is divided into heating branch refrigerant and heating main refrigerant by the second three-way valve 812; the heating branch refrigerant enters the gas-liquid separator 40 via the fourth flow control valve 504. Based on the system subcooling or return gas superheat, the flow rate of the heat exchange heating branch refrigerant flowing out of the gas-liquid separator 40 is controlled by the opening and closing and opening degree adjustment of the first flow control valve 501. After passing through the first three-way valve 811, the heat exchange heating branch refrigerant mixes with the heating main refrigerant and is then regulated by the electronic expansion valve 52 before entering the air-side heat exchanger 60 via the fifth flow control valve 505; during this period, the second flow control valve 502 is closed so that the heating branch refrigerant can only enter the gas-liquid separator 40, and the third flow control valve 503 is closed so that the heat exchange heating branch refrigerant cannot directly enter the air-side heat exchanger 60.

[0063] Specifically, the connection relationships between the control valve module 50, the connecting valve module 80, the compressor 10, the four-way valve 20, the water-side heat exchanger 30, the gas-liquid separator 40, and the air-side heat exchanger 60 are as follows.

[0064] Please see Figure 2In cooling mode, the connection and opening / closing of the valves cause the refrigerant to flow as follows: It exits from the compressor 10's exhaust port A and enters the four-way valve 20's inlet port D, then through the four-way valve 20's first working port E into the air-side heat exchanger 60. It then passes through the third three-way valve 813, the third flow control valve 503, and finally the first three-way valve 811, splitting into two refrigeration branches. The first refrigeration branch enters the gas-liquid separator 40 via the first flow control valve 501, where it exchanges heat with the low-temperature refrigerant and compressor refrigeration oil mixture. After releasing heat to the low-temperature refrigerant and compressor refrigeration oil and gaining more cooling capacity, it condenses and then flows through the third three-way valve 811. After the flow rate is regulated by the second flow control valve 502 after passing through the four-way three-way valve 814, the refrigerant mixes with the refrigerant in the second refrigeration branch of the first three-way valve 811 through the fifth three-way valve 815, and then enters the electronic expansion valve 52 for throttling through the first one-way valve 821 and the sixth three-way valve 816. After passing through the seventh three-way valve 817, the eighth three-way valve 818, the fourth one-way valve 824, and the second three-way valve 812, it enters the water-side heat exchanger 30. Then, it enters the gas-liquid separator 40 after absorbing heat and evaporating completely, carrying the refrigeration oil back to the return port B of the compressor 10. In this mode, the fifth flow control valve 505, which connects the third three-way valve 813 and the seventh three-way valve 817, is closed; the fourth flow control valve 504, which connects the second three-way valve 812 and the fourth three-way valve 814, is closed; the second check valve 822, which connects the fifth three-way valve 815 and the eighth three-way valve 818, is closed; and the third check valve 823, which connects the second three-way valve 812 and the sixth three-way valve 816, is closed.

[0065] Please see Figure 3In heating mode, the connection and opening / closing of the valves ensure the refrigerant flows as follows: It exits from the compressor 10's exhaust port A and enters the four-way valve 20's inlet D, then through the four-way valve 20's second working port C into the water-side heat exchanger 30. From there, it is divided into two heating branches by the second three-way valve 812. The first heating branch passes through the fourth flow control valve 504 and the fourth three-way valve 814 before entering the gas-liquid separator 40. There, it exchanges heat with the low-temperature refrigerant and compressor refrigeration oil mixture, releasing heat to the low-temperature refrigerant and compressor refrigeration oil, gaining more cooling capacity, and then further condensing before passing through the first flow control valve 504 again. The flow rate is regulated by valve 501, and then the refrigerant passes through the first three-way valve 811, the fifth three-way valve 815, and the first one-way valve 821 in sequence to enter the sixth three-way valve 816. After mixing with the refrigerant in the second heating branch via the third one-way valve 823, the refrigerant enters the electronic expansion valve 52 for throttling. Then, it passes through the seventh three-way valve 817, the fifth flow control valve 505, and the third three-way valve 813 in sequence to enter the air-side heat exchanger 60 for heat exchange. Finally, it passes through the first working port E of the four-way valve 20 and the exhaust port S of the four-way valve 20 to enter the gas-liquid separator 40 to absorb heat and completely evaporate. After evaporation, it carries the refrigeration oil back to the return port B of the compressor 10. In this mode, the second flow control valve 502, which connects the fourth three-way valve 814 and the fifth three-way valve 815, is closed; the third flow control valve 503, which connects the first three-way valve 811 and the third three-way valve 813, is closed; the fourth check valve 824, which connects the second three-way valve 812 and the eighth three-way valve 818, is shut off; and the second check valve 822, which connects the fifth three-way valve 815 and the eighth three-way valve 818, is shut off.

[0066] Please see Figure 4In defrost mode, the connection and opening / closing of each valve ensures the refrigerant flow path is as follows: the refrigerant is discharged from the exhaust port A of the compressor 10 and enters the inlet D of the four-way valve 20. It then enters the air-side heat exchanger 60 through the first working port E of the four-way valve 20. After passing through the third three-way valve 813, it is divided into the first branch and the second branch. The first branch passes through the third flow control valve 503, the first three-way valve 811, the fifth three-way valve 815, the first check valve 821, and the sixth three-way valve 816 in sequence. After being throttled by the electronic expansion valve 52, it enters the seventh three-way valve 817 and mixes with the second branch that passes through the fifth flow control valve 505. Then, it enters the eighth three-way valve 815, passes through the fourth check valve 824 and the second three-way valve 812, and enters the water-side heat exchanger. Finally, it passes through the second working port C and the exhaust port S of the four-way valve 20 and enters the gas-liquid separator 40. After absorbing heat and evaporating completely, it carries the refrigerant oil back to the return port B of the compressor 10. In this mode, the first flow control valve 501 connecting the first three-way valve 811 and the gas-liquid separator 40 is closed; the fourth flow control valve 504 connecting the second three-way valve 812 and the fourth three-way valve 814 is closed; the second flow control valve 502 connecting the fourth three-way valve 813 and the fifth three-way valve 815 is closed; the second check valve 822 connecting the fifth three-way valve 815 and the eighth three-way valve 818 is closed; and the third check valve 823 connecting the second three-way valve 812 and the sixth three-way valve 816 is closed.

[0067] The temperature detection module 70 includes a first temperature sensor 71, a second temperature sensor 72, a third temperature sensor 73, and a fourth temperature sensor 74. The first temperature sensor 71 is installed on the coil of the air-side heat exchanger 60 and is used to measure the coil temperature T. p The temperature signal is then transmitted to the controller. The second temperature sensor 72 is located at the inlet of the electronic expansion valve 52 and is used to measure the subcooling temperature T. e The temperature signal is transmitted to the controller. The third temperature sensor 73 is located between the exhaust end of the gas-liquid separator 40 and the return gas port of the compressor 10, and is used to measure the return gas temperature T of the refrigerant. hq The temperature sensor 74 is used to measure the ambient temperature T. h The temperature signal is transmitted to the controller, and the location of the fourth temperature sensor 74 is not limited in this application.

[0068] The controller further includes a storage unit and a processing unit. The storage unit is used to store the set subcooling threshold ΔT. C TV Heating subcooling threshold ΔT H TV Return gas superheat threshold First duration threshold t1 TV Second duration threshold t2TV The third duration threshold t3 TV Fourth duration threshold t4 TV The table includes the first time period t′1, the second time period t′2, the fine-tuning opening degree ΔK1, and the compensation opening degree-temperature comparison table, as well as the coil temperature T collected by the first temperature sensor 71 at each time point. p The second temperature sensor 72 collects the supercooling temperature T. e The return gas temperature T collected by the third temperature sensor 73 hq The fourth temperature sensor 74 collects the ambient temperature T. h The processing unit is used to calculate and execute various judgment and control programs, including the program for opening, closing, and adjusting the opening degree of each valve in the flow control valve module.

[0069] Furthermore, the heat pump air conditioning system is equipped with a first filter on the refrigerant pipeline connecting the third three-way valve 813 and the air-side heat exchanger 60, and a second filter on the refrigerant pipeline connecting the second three-way valve 8182 and the water-side heat exchanger 30.

[0070] Please see Figure 5 The method for controlling subcooling in a heat pump air conditioning system according to the present invention includes the following steps.

[0071] S10 obtains the system's operating mode:

[0072] If it is in cooling mode, proceed to step S20;

[0073] If it is in heating mode, proceed to step S30;

[0074] If it is in defrost mode, proceed to step S40.

[0075] S20 controls the first flow control valve 501 and the third flow control valve 503 to be fully open, and the fourth flow control valve 504 and the fifth flow control valve 505 to be closed; the coil temperature T is obtained. p Supercooling temperature T e and return gas temperature T hq Based on coil temperature T p and supercooling temperature T e Obtain the system subcooling degree ΔT and return gas temperature T. hq and coil temperature T p Obtain the return gas superheat ΔT hg Compare the system subcooling ΔT with the set refrigeration subcooling threshold ΔT. C TV ΔT return gas superheat hg With the set return gas superheat threshold Based on the comparison results, the opening and closing of the second flow control valve 502 and its opening degree are controlled; the opening degree of the electronic expansion valve 52 is adjusted according to the existing normal logic.

[0076] Specifically, it includes the following sub-steps:

[0077] S21 controls the opening of the first flow control valve 501 and the third flow control valve 503 to the maximum opening, and controls the fourth flow control valve 504 and the fifth flow control valve 505 to close.

[0078] S22 obtains the coil temperature T p Supercooling temperature T e and return gas temperature T hq According to the coil temperature T p With supercooling temperature T e The difference is used to obtain the system subcooling ΔT, based on the return gas temperature T. hq With coil temperature T p The difference is used to obtain the return gas superheat ΔT hg And compare the system subcooling ΔT with the set refrigeration subcooling threshold ΔT. C TV ΔT return gas superheat hg With the set return gas superheat threshold Relationship:

[0079] If the system subcooling ΔT is less than or equal to the refrigeration subcooling threshold ΔT C TV And the return gas superheat ΔT hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set first duration threshold t1 TV Then control the second flow control valve 502 to the minimum opening degree K. 2-MIN Start and proceed to step S23;

[0080] In other cases, the second flow control valve 502 is closed.

[0081] The subcooling ΔT of the system satisfies: ΔT = T p -T e .

[0082] The return gas superheat ΔT hg Satisfy: ΔT hg =T hg -T p .

[0083] The refrigeration subcooling threshold ΔT C TV The value range is -5℃ to 10℃.

[0084] The return gas superheat threshold The value range is -3℃ to 5℃.

[0085] The first duration threshold t1 TV The value range is 1 min to 5 min.

[0086] This step is used to determine whether it is necessary to separate a refrigeration branch refrigerant from the refrigerant flowing out of the air-side heat exchanger 60; by opening the second flow control valve 502, the refrigeration branch refrigerant enters the gas-liquid separator 40 for heat exchange, and the main refrigeration refrigerant does not pass through the gas-liquid separator 40.

[0087] S23 continuously acquires the coil temperature T′ after the second flow control valve opens. p Supercooling temperature T′ e and return gas temperature T′ hq According to the coil temperature T′ p With supercooling temperature T′ e The difference is used to obtain the system subcooling Δ′T, based on the return gas temperature T′. hq With coil temperature T′ p The difference is used to obtain the return gas superheat ΔT′ hg And compare the system subcooling Δ′T with the refrigeration subcooling threshold ΔT. C TV ΔT′ of return gas superheat hg With return gas superheat threshold Relationship:

[0088] If the system subcooling Δ′T is less than or equal to the refrigeration subcooling threshold ΔT C TV And the return gas superheat ΔT′ hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set second duration threshold t2 TV The opening degree of the second flow control valve 502 is controlled at the minimum opening degree K. 2-MIN Based on this, the valve opening is increased by ΔK1, and the valve remains unadjusted for the first time period t′1, followed by PID control.

[0089] In other cases, the opening degree of the second flow control valve 502 is controlled to be at the minimum opening degree K. 2-MIN .

[0090] The second duration threshold t2 TV The value range is 1 min to 5 min.

[0091] The fine-tuning opening ΔK1 satisfies:

[0092] ΔK1=α*K 2-MAX

[0093] In the formula, K 2-MAX This indicates the maximum opening degree of the second flow control valve, and α represents the weighting coefficient, ranging from 0.05 to 0.80. The specific value of α varies depending on the system configuration, such as compressors, heat exchangers, electronic expansion valves, etc., and is determined based on actual test results.

[0094] The range of the first time period t′1 varies depending on the system configuration, such as compressors, heat exchangers, electronic expansion valves, etc., and should be determined based on the actual test results. It is recommended to be 1 min to 5 min.

[0095] The PID control adjusts the system according to the difference between the target subcooling and the system subcooling, using existing adjustment methods.

[0096] This step is used to regulate the flow rate of refrigerant in the refrigeration branch that enters the gas-liquid separator 40 for heat exchange.

[0097] S24 adjusts the opening of the electronic expansion valve 52 according to the existing normal logic.

[0098] This step allows the refrigerant from the refrigeration branch that enters the gas-liquid separator 40 for heat exchange to be mixed with the refrigerant from the main refrigeration branch that has not passed through the gas-liquid separator 40, and the flow rate of the refrigerant entering the water-side heat exchanger 30 is controlled according to the existing normal logic.

[0099] S30 controls the fourth flow control valve 504 and the fifth flow control valve 505 to be fully open, and the second flow control valve 501 and the third flow control valve 503 to be closed; the coil temperature T is obtained. p Supercooling temperature T e Based on coil temperature T p and supercooling temperature T e Obtain the system subcooling ΔT; compare the system subcooling ΔT with the set heating subcooling threshold ΔT. H TV Based on the comparison results, the opening and closing of the first flow control valve 501 and its opening degree are controlled; the opening degree of the electronic expansion valve 52 is adjusted according to the existing normal logic.

[0100] Specifically, it includes the following sub-steps:

[0101] S31 controls the fourth flow control valve 504 and the fifth flow control valve 505 to their maximum opening, and controls the second flow control valve 501 and the third flow control valve 503 to be closed.

[0102] S32 obtains the coil temperature T p Supercooling temperature T e According to the coil temperature T p With supercooling temperature T e The system subcooling ΔT is obtained by measuring the temperature difference; and the system subcooling ΔT is compared with the set heating subcooling threshold ΔT.H TV Relationship:

[0103] If the system subcooling ΔT is less than or equal to the heating subcooling threshold ΔT H TV And the duration t is greater than or equal to the set third duration threshold t3 TV Then control the first flow control valve 501 to the minimum opening degree K. 1-MIN Start and proceed to step S33;

[0104] In other cases, the first flow control valve 501 is closed.

[0105] The heating subcooling threshold ΔT H TV The value range is -5℃ to 10℃.

[0106] The third duration threshold t3 TV The value range is 1 min to 5 min.

[0107] This step is used to determine whether a heating branch refrigerant needs to be separated from the refrigerant flowing out of the water-side heat exchanger 30; by opening the first flow control valve 501, the heating branch refrigerant enters the gas-liquid separator 40 for heat exchange, and the main heating refrigerant does not pass through the gas-liquid separator 40.

[0108] S33 continuously acquires the coil temperature T′ after the first flow control valve opens. p Supercooling temperature T′ e According to the coil temperature T′ p With supercooling temperature T′ e The difference is used to obtain the system subcooling Δ′T, and the system subcooling Δ′T is compared with the heating subcooling threshold ΔT. H TV Relationship:

[0109] If the system subcooling Δ′T is less than or equal to the heating subcooling threshold ΔT H TV And the duration t is greater than or equal to the set fourth duration threshold t4. TV Further obtain the ambient temperature T h According to the ambient temperature T h The compensation opening corresponding to the temperature range is used to compensate for the minimum opening to obtain the corrected minimum opening K′ of the first flow control valve 501. 1-MIN Control the first flow control valve 501 to correct the minimum opening degree K′ 1-MIN During the second time period t′2, the valve is not adjusted, and then PID control is applied.

[0110] In other cases, the opening degree of the first flow control valve 501 is controlled at the minimum opening degree K.1-MIN .

[0111] The modified minimum opening degree K′ 1-MIN =K 1-MIN +ΔK h , where ΔK h This indicates the compensation opening degree related to ambient temperature, specifically:

[0112] When -10℃ < T h When the temperature is ≤2℃, the compensation opening degree satisfies: ΔK h =5%*K 1-MAX ;

[0113] When -15℃ < T h When the temperature is ≤-10℃, the compensation opening degree satisfies: ΔK h =8%*K 1-MAX ;

[0114] When -20℃ < T h When the temperature is ≤-15℃, the compensation opening degree satisfies: ΔK h =10%*K 1-MAX ;

[0115] When -25℃ < T h When the temperature is ≤-20℃, the compensation opening degree satisfies: ΔK h =15%*K 1-MAX ;

[0116] When T h At temperatures below -25℃, the compensation opening degree satisfies: ΔK h =20%*K 1-MAX .

[0117] The fourth duration threshold t4 TV The value range is 1 min to 5 min.

[0118] The range of the second time period t′2 varies depending on the system configuration, such as compressors, heat exchangers, electronic expansion valves, etc., and should be determined based on the actual test results. It is recommended to be 1 min to 5 min.

[0119] This step is used to adjust the flow rate of the refrigerant in the heating branch that enters the gas-liquid separator 40 for heat exchange. By monitoring the system temperature parameters and correcting the minimum opening, the flow rate can be better controlled at different low temperatures, thus ensuring the subcooling of the mixed refrigerant before it flows through the electronic expansion valve.

[0120] Furthermore, step S32 can be performed by monitoring the return gas superheat to determine whether it is necessary to divide the refrigerant flowing out of the water-side heat exchanger 30 into two heating refrigerant branches, thereby controlling the opening and closing of the first flow control valve. Specifically:

[0121] S`32 obtains the coil temperature T p Return gas temperature T hq Calculate the return gas temperature T hq With coil temperature T p The temperature difference is used to obtain the return gas superheat ΔT hg And compare the return gas superheat ΔT hg With the set return gas superheat threshold Relationship:

[0122] If the return gas superheat ΔT hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set third duration threshold t3 TV Then control the first flow control valve 501 to the minimum opening degree K. 1-MIN Start and execute step S`33;

[0123] In other cases, the first flow control valve 501 is closed.

[0124] S`33 continuously acquires the coil temperature T′ after the first flow control valve opens. p Return gas temperature T′ hq According to the return gas temperature T′ hq With coil temperature T′ p The difference is used to obtain the return gas superheat Δ′T hg And compare the return gas superheat ΔT′ hg With return gas superheat threshold Relationship:

[0125] If the return gas superheat ΔT′ hg Less than or equal to the return gas superheat threshold And the duration t is greater than or equal to the set fourth duration threshold t4 TV Further obtain the ambient temperature T h According to the ambient temperature T h The compensation opening corresponding to the temperature range is used to compensate for the minimum opening to obtain the corrected minimum opening K′ of the first flow control valve 501. 1-MIN Control the first flow control valve 501 to correct the minimum opening degree K′ 1-MIN During the second time period t′2, the valve is not adjusted, and then PID control is applied.

[0126] In other cases, the opening degree of the first flow control valve 501 is controlled at the minimum opening degree K. 1-MIN .

[0127] The PID control adjusts the system according to the difference between the target subcooling and the system subcooling, using existing adjustment methods.

[0128] S34 adjusts the opening of the electronic expansion valve 52 according to the existing normal logic.

[0129] This step allows the refrigerant from the heating branch that enters the gas-liquid separator 40 for heat exchange to be mixed with the refrigerant from the main heating branch that has not been separated from the gas-liquid separator 40, and the flow rate of the refrigerant entering the air-side heat exchanger 30 is controlled according to the existing normal logic.

[0130] S40 controls the third flow control valve 503 and the fifth flow control valve 505 to be fully open, and the first flow control valve 501, the second flow control valve 502, and the fourth flow control valve 504 to be closed; adjust the opening of the electronic expansion valve 52 to a fixed defrosting opening until defrosting is completed.

[0131] Compared to existing technologies, the air-source heat pump air conditioning system of this invention, in both cooling and heating modes, monitors the system's subcooling and / or return gas superheat. A flow control valve module draws liquid refrigerant from the system's condenser liquid line (air-side heat exchanger during cooling, water-side heat exchanger during heating) into a gas-liquid separator for heat exchange. The flow rate of the refrigerant exiting the gas-liquid separator is adjusted by regulating the opening of the flow control valves on both sides of the separator. This heat exchange branch refrigerant mixes with the main refrigerant in the condenser line that has not undergone heat exchange before entering the electronic expansion valve for throttling. This system ensures that the subcooling of the mixed refrigerant before passing through the electronic expansion valve meets requirements, thus maintaining the evaporator's cooling capacity. This system effectively solves the problems of increased system refrigerant oil viscosity and low refrigerant miscibility leading to poor compressor refrigerant oil return under low and ultra-low ambient temperature conditions; and the problem of insufficient evaporation in the evaporator causing liquid refrigerant to enter the compressor and cause liquid slugging. Furthermore, by controlling the ambient temperature T... h The opening of the flow control valve that controls the flow of refrigerant into the gas-liquid separator is modified so that the system can better adapt to the precise control of the flow at different low temperatures, and can better ensure the subcooling of the mixed refrigerant before it flows through the electronic expansion valve, thus maintaining the cooling capacity of the evaporator.

[0132] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. An air-source heat pump air conditioning system, comprising a compressor, a four-way valve, a water-side heat exchanger, a gas-liquid separator, an air-side heat exchanger, a control valve module, a connecting valve module, and a temperature detection module, all connected via refrigerant piping, and a controller electrically and / or communicatively connected to the control valve module and the temperature detection module; the control valve module includes a first flow control valve, a second flow control valve, a third flow control valve, a fourth flow control valve, a fifth flow control valve, and an electronic expansion valve; the connecting valve module includes a first three-way valve, a second three-way valve, a third three-way valve, a fourth three-way valve, a fifth three-way valve, a sixth three-way valve, a seventh three-way valve, and an eighth three-way valve, and a first one-way valve, a second one-way valve, a third one-way valve, and a fourth one-way valve, wherein... The first end of the third three-way valve is connected to the air-side heat exchanger, the second end is connected to the third flow control valve, and the third end is connected to the fifth flow control valve. The other end of the third flow control valve is connected to the first end of the first three-way valve. The second end of the first three-way valve is connected to the first flow control valve, and the third end of the first three-way valve is connected to the first end of the fifth three-way valve. The other end of the first flow control valve is connected to the gas-liquid separator. The second end of the fifth three-way valve is connected to the second flow control valve, and the third end of the fifth three-way valve is connected to one end of the first check valve and the second check valve, respectively. The other end of the second flow control valve is connected to the first end of the fourth three-way valve, the other end of the first check valve is connected to the first end of the sixth three-way valve, and the other end of the second check valve is connected to the first end of the eighth three-way valve. The second end of the sixth three-way valve is connected to the third one-way valve, and the third end of the sixth three-way valve is connected to the electronic expansion valve. The second end of the eighth three-way valve is connected to the first end of the seventh three-way valve, and the third end of the eighth three-way valve is connected to the fourth one-way valve. The other ends of the third and fourth one-way valves are both connected to the first end of the second three-way valve. The second end of the second three-way valve is connected to the water-side heat exchanger, and the third end of the second three-way valve is connected to the fourth flow control valve. The other end of the fourth flow control valve is connected to the second end of the fourth three-way valve, and the third end of the fourth three-way valve is connected to the gas-liquid separator. The second end of the seventh three-way valve is connected to the electronic expansion valve, and the third end of the seventh three-way valve is connected to the other end of the fifth flow control valve. The controller, through the control valve module, ensures that the refrigerant meets the following flow path relationship: In cooling mode, the refrigerant flowing out of the air-side heat exchanger is divided into refrigeration branch refrigerant and refrigeration main refrigerant by the first three-way valve after passing through the third flow control valve. The refrigeration branch refrigerant enters the gas-liquid separator through the first flow control valve. Based on the system subcooling and return gas superheat, the flow rate of the heat exchange refrigeration branch refrigerant flowing out of the gas-liquid separator is controlled by the opening and closing of the second flow control valve. The heat exchange refrigeration branch refrigerant mixes with the refrigeration main refrigerant and then enters the water-side heat exchanger through the electronic expansion valve. During this period, the fourth flow control valve is closed to prevent the heat exchange refrigeration branch refrigerant from directly entering the water-side heat exchanger, and the fifth flow control valve is closed to prevent the mixed refrigerant regulated by the electronic expansion valve from entering the air-side heat exchanger. In heating mode, the refrigerant flowing out of the water-side heat exchanger is divided into heating branch refrigerant and heating main refrigerant by the second three-way valve. The heating branch refrigerant enters the gas-liquid separator via the fourth flow control valve. Based on the system subcooling or return gas superheat, the flow rate of the heat exchange heating branch refrigerant flowing out of the gas-liquid separator is controlled by the opening and closing of the first flow control valve. After passing through the first three-way valve, the heat exchange heating branch refrigerant mixes with the heating main refrigerant and is then regulated by the electronic expansion valve before entering the air-side heat exchanger via the fifth flow control valve. During this period, the second flow control valve is closed, allowing the heating branch refrigerant to enter only the gas-liquid separator, and the third flow control valve is closed, preventing the heat exchange heating branch refrigerant from directly entering the air-side heat exchanger.

2. The air source heat pump air conditioning system according to claim 1, characterized in that: In cooling mode, the controller controls the flow rate of refrigerant in the heat exchange cooling branch of the gas-liquid separator in the following manner: S21 controls the opening degree of the first flow control valve and the third flow control valve to the maximum opening degree; S22 Obtain coil temperature Supercooling temperature and return gas temperature According to the coil temperature With supercooled temperature The difference is used to obtain the system subcooling. According to the return gas temperature With coil temperature The difference is used to obtain the return gas superheat. And compare the system subcooling. With the set subcooling threshold superheat of return gas With the set return gas superheat threshold Relationship: If the system is subcooled Less than or equal to the refrigeration subcooling threshold And the return gas superheat Less than or equal to the return gas superheat threshold and duration Greater than or equal to the set first duration threshold Then control the second flow control valve to its minimum opening. Start and proceed to step S23; In other cases, the second flow control valve should be closed. S23 continuously acquires the coil temperature after the second flow control valve opens. Supercooling temperature and return gas temperature According to the coil temperature With supercooled temperature The difference is used to obtain the system subcooling. According to the return gas temperature With coil temperature The difference is used to obtain the return gas superheat. And compare the system subcooling. With the subcooling threshold superheat of return gas With return gas superheat threshold Relationship: If the system is subcooled Less than or equal to the refrigeration subcooling threshold And the return gas superheat Less than or equal to the return gas superheat threshold and duration Greater than or equal to the set second duration threshold Control the opening degree of the second flow control valve to the minimum opening degree. On the basis of this, increase the fine adjustment of the opening degree and continue in the first time period Without adjusting the valve, adjust according to PID control; In other cases, the opening degree of the second flow control valve is controlled at its minimum opening degree. .

3. The air source heat pump air conditioning system according to claim 2, characterized in that: The fine-tuning opening satisfy: In the formula, This indicates the maximum opening degree of the second flow control valve. This represents the weighting coefficient, with a value range of 0.05 to 0.

80.

4. The air source heat pump air conditioning system according to claim 2, characterized in that: The refrigeration subcooling threshold The value range is -5℃ to 10℃, and the return gas superheat threshold is... The value range is -3℃ to 5℃.

5. The air source heat pump air conditioning system according to claim 2, characterized in that: First duration threshold The value range is 1 min to 5 min; the second duration threshold The value range is 1 min to 5 min.

6. The air source heat pump air conditioning system according to any one of claims 1 to 5, characterized in that: In heating mode, the controller controls the flow rate of refrigerant in the heat exchange heating branch exiting the gas-liquid separator in the following manner: S31 controls the opening degree of the fourth and fifth flow control valves to the maximum opening degree; S32 Get coil temperature Supercooling temperature According to the coil temperature With supercooled temperature The temperature difference is used to obtain the system subcooling. And compare the system subcooling. With the set heating subcooling threshold Relationship: If the system is subcooled Less than or equal to the heating subcooling threshold and duration Greater than or equal to the set third duration threshold Then control the first flow control valve to its minimum opening. Start and proceed to step S33; In other cases, the first flow control valve shall be closed. S33 continuously acquires the coil temperature after the first flow control valve opens. Supercooling temperature According to the coil temperature With supercooled temperature The difference is used to obtain the system subcooling. And compare the system subcooling. With heating subcooling threshold Relationship: If the system is subcooled Less than or equal to the heating subcooling threshold and duration Greater than or equal to the set fourth duration threshold To further obtain the ambient temperature According to ambient temperature The compensation opening corresponding to the temperature range is used to compensate for the minimum opening to obtain the corrected minimum opening of the first flow control valve. Control the first flow control valve to correct the minimum opening. Run the second time period Without adjusting the valve, adjust according to PID control; In other cases, the opening degree of the first flow control valve is controlled at its minimum opening degree. .

7. The air source heat pump air conditioning system according to claim 6, characterized in that: Corrected minimum opening of the first flow control valve satisfy: In the formula, This indicates the minimum opening degree of the first flow control valve. This indicates the compensation opening degree related to ambient temperature, where Depending on the ambient temperature range, its value satisfies: When -10℃ < When ≤2℃, compensation opening degree ; When -15℃ < Compensation opening at ≤-10℃ ; When -20℃ < When the temperature is ≤-15℃, the compensation opening degree ; When -25℃ < Compensation opening at ≤-20℃ ; when At temperatures below -25℃, compensation opening degree ; in, This indicates the maximum opening degree of the first flow control valve. Indicates ambient temperature.

8. The air source heat pump air conditioning system according to claim 6, characterized in that: The heating subcooling threshold The value range is -5℃ to 10℃.

9. The air source heat pump air conditioning system according to any one of claims 1 to 5, characterized in that: In heating mode, the controller controls the flow rate of refrigerant in the heat exchange heating branch exiting the gas-liquid separator in the following manner: S31 controls the opening degree of the fourth and fifth flow control valves to the maximum opening degree; S`32 Obtain coil temperature Return gas temperature According to the return gas temperature With coil temperature The temperature difference obtains the return gas superheat. And compare the return gas superheat. With the set return gas superheat threshold Relationship: If the return air is overheated Less than or equal to the return gas superheat threshold and duration Greater than or equal to the set third duration threshold Then control the first flow control valve to its minimum opening. Start and execute step S`33; In other cases, the first flow control valve shall be closed. S`33 continuously acquires the coil temperature after the first flow control valve opens. Return gas temperature According to the return gas temperature With coil temperature The difference is used to obtain the return gas superheat. And compare the return gas superheat. With return gas superheat threshold Relationship: If the return air is overheated Less than or equal to the return gas superheat threshold and duration Greater than or equal to the set fourth duration threshold To further obtain the ambient temperature According to ambient temperature The compensation opening corresponding to the temperature range is used to compensate for the minimum opening to obtain the corrected minimum opening of the first flow control valve. Control the first flow control valve to correct the minimum opening. Run the second time period Without adjusting the valve, adjust according to PID control; In other cases, the opening degree of the first flow control valve is controlled at its minimum opening degree. .

10. The air source heat pump air conditioning system according to any one of claims 1, 2, 3, 4, 5, 7, and 8, characterized in that: It also includes a defrost mode, in which the controller, through the control valve module, ensures that the refrigerant follows the following flow path relationship: The refrigerant flowing out of the air-side heat exchanger is divided into a first branch refrigerant and a second branch refrigerant after passing through the third three-way valve. The first branch refrigerant passes through the third flow control valve, the first three-way valve, and the electronic expansion valve in sequence, and then mixes with the second branch refrigerant that has passed through the fifth flow control valve. After mixing, it enters the water-side heat exchanger after passing through the second three-way valve. During this process, the first flow control valve is closed to prevent the first branch refrigerant from entering the gas-liquid separator, the second flow control valve is closed to prevent the first branch refrigerant from entering the gas-liquid separator, and the fourth flow control valve is closed to prevent the mixed refrigerant from entering the gas-liquid separator. Among them, the third and fifth flow control valves are fully open, and the opening of the electronic expansion valve is adjusted to a fixed defrost opening until defrosting is completed.

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