Air-supplementing enthalpy-increasing heat pump system and operation method thereof

Abstract

The invention discloses an air-supplementing enthalpy-increasing heat pump system and an operation mode thereof. The system comprises a compressor, a first indoor heat exchanger, a flash tank with a subcooler, a second indoor heat exchanger, an outdoor heat exchanger, a gas-liquid separator, a plurality of throttling valves and a needle valve. According to the system, a flash tank with a subcooler is adopted, and a subcooler air supply system and a flash tank air supply system are coupled, so that the system can be switched among a subcooler air supply mode, a flash tank air supply mode and a parallel dehumidification heating mode, and air supply backflow is prevented under the condition that the heat exchange efficiency is guaranteed. And meanwhile, the indoor evaporator and the outdoor evaporator are connected in parallel, so that the evaporation pressure in the two evaporators can be independently controlled, and frosting of the indoor evaporator is effectively prevented while the dehumidification capacity of the indoor evaporator is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle heat pumps, and particularly to an air-injected enhanced enthalpy heat pump system and an operation method thereof. Background Art

[0002] According to the research of the Society of Automotive Engineers (SAE) in the United States, the energy consumption of air conditioning refrigeration and heating with PTC (Positive Temperature Coefficient) materials accounts for 33% of the total vehicle energy consumption. At the same time, when a pure electric vehicle operates at full load in winter with severe battery degradation and heating with PTC materials, its driving range will be reduced by nearly 50%. As an efficient, energy-saving and environmental protection heating technology, a heat pump can convert low-grade heat energy into high-grade heat energy while consuming a small amount of electric energy. Applying heat pump technology to the winter heating of electric vehicles can effectively reduce the energy consumption of electric vehicles and increase their driving range. However, under low-temperature conditions in winter, the decrease in outdoor temperature will also cause the evaporation temperature (pressure) to drop, resulting in a decrease in the refrigerant circulation flow rate and the heating capacity; the decrease in evaporation pressure will further cause an increase in the system compression ratio and an increase in the exhaust temperature, reducing the reliability and safety of the compressor operation, which seriously hinders the popularization and application of the heat pump system.

[0003] The air-injected enhanced enthalpy technology can improve the heating energy efficiency performance of the heat pump system under low ambient temperature conditions. The application of the air-injected enhanced enthalpy technology not only increases the subcooling degree and the circulation flow rate to achieve the purpose of improving the heating capacity, but also broadens the operating temperature range of the system for heating under low ambient temperature to a certain extent. Moreover, by constructing a quasi-two-stage compression system, it reduces the power consumption of the compressor and significantly improves the COP (Coefficient of Performance). A typical air-injected enhanced enthalpy heat pump system mainly consists of an intermediate air-injected compressor, an evaporator, a condenser, a flash tank or a subcooler, and multiple throttling components, which are divided into a subcooler air-injection system and a flash tank air-injection system. The subcooler air-injection system follows the principle of modular independent design, that is, the refrigerant flow rate in the evaporator and the intermediate air-injection flow rate are separately controlled by two throttle valves, which is convenient for adjustment, and the air-injection pressure will not be higher than the exhaust pressure, and refrigerant reflux will not occur. However, the COP of the system is affected by the heat transfer efficiency of the subcooler. Although the flash tank air-injection system can avoid the problem of low heat transfer efficiency, the system follows the principle of coupled control, that is, the adjustment of any throttle valve will affect the refrigerant flow rate in the evaporator and the intermediate air-injection volume, and joint control is required. When the pressure in the flash tank is lower than the air-injection pressure, reflux is likely to occur. Summary of the Invention

[0004] The purpose of the present invention is to provide an air-inflation enthalpy-increasing heat pump system and its operation mode. The system adopts a flash tank with a subcooler, and couples the subcooler air-inflation system with the flash tank air-inflation system, so that the system can switch between the subcooler air-inflation mode and the flash tank air-inflation mode, and prevent the air-inflation backflow while ensuring the heat exchange efficiency. At the same time, the system connects the indoor evaporator and the outdoor evaporator in parallel, so that the evaporation pressure in the two evaporators can be controlled separately, which effectively prevents the frost from forming while increasing the dehumidification capacity of the indoor evaporator.

[0005] The present invention is achieved through the following technical solutions:

[0006] The invention discloses an air-supplementing enthalpy-increasing heat pump system, which is composed of a compressor, a first indoor heat exchanger, a flash tank with a subcooler, a second indoor heat exchanger, an outdoor heat exchanger, a gas-liquid separator, a plurality of throttle valves and a plurality of needle valves.

[0007] The outlet of the compressor is connected to the inlet of the first indoor heat exchanger, and the outlet of the first indoor heat exchanger has two branches, wherein the first branch is provided with a first throttle valve, the first branch is connected to the inlet of the tank body with a subcooler flash tank, and the second branch is connected to the subcooler inlet of the subcooler flash tank; the tank body with the subcooler flash tank has a liquid phase outlet and a gas phase outlet, wherein the gas phase outlet is connected to the air supply inlet of the compressor, and the liquid phase outlet is connected to the inlet of the outdoor heat exchanger through the second throttle valve; the outlet of the outdoor heat exchanger is connected to the inlet of the gas-liquid separator;

[0008] The outlet of the subcooler with the flash tank of the subcooler is connected with a third throttle valve, the outlet of the third throttle valve is divided into two branches, one of which is connected with the inlet of the outdoor heat exchanger, and the other is connected with the inlet of the second indoor heat exchanger, and the outlet of the second indoor heat exchanger is connected with the inlet of the gas-liquid separator through the fourth throttle valve;

[0009] The outlet of the gas-liquid separator is connected to the inlet of the compressor.

[0010] Preferably, a first needle valve is provided on the second branch, a second needle valve is provided on the pipeline between the outlet of the third throttle valve and the inlet of the outdoor heat exchanger, and a third needle valve is provided on the pipeline between the gas phase outlet and the inlet of the compressor.

[0011] The operating modes of the air-increasing and enthalpy-boosting heat pump system include the flash tank air-increasing heating mode, the subcooler air-increasing heating mode, and the parallel dehumidification and heating mode. Among them, the flash tank air-increasing heating mode is used when the pressure in the flash tank is higher than the air-increasing pressure. At this time, the flash tank, as a key component, has excellent heat exchange efficiency, which helps to reduce the enthalpy value at the inlet of the evaporator and improve the heating COP of the system. When the outdoor temperature drops, the evaporation pressure of the system and the pressure in the flash tank decrease, and it is easy to occur that the air-increasing pressure is higher than the pressure in the flash tank, resulting in air-increasing backflow. The subcooler air-increasing heating mode is used in the case of air-increasing backflow. At this time, the refrigerant flow rate in the evaporator and the intermediate air-increasing flow rate are separately controlled by two throttle valves, which can ensure that the air-increasing pressure will not be higher than the exhaust pressure, avoiding the problem of air-increasing backflow. At the same time, the intermediate air-increasing reduces the exhaust temperature of the compressor, making the compression process closer to the isentropic process and reducing the power consumption of the compressor. The parallel dehumidification and heating mode is used when the indoor air humidity is relatively high. In the parallel dehumidification and heating mode, the indoor evaporator and the outdoor evaporator operate in parallel, and the evaporation pressures of the outdoor and indoor evaporators can be freely controlled, effectively avoiding the problem of evaporator frosting.

[0012] In the above flash tank air-increasing heating mode, the components through which the refrigerant flows include a compressor, a first indoor heat exchanger, a first throttle valve, a flash tank with a subcooler, a second throttle valve, an outdoor heat exchanger, and a gas-liquid separator. At this time, the third throttle valve, the fourth throttle valve, the first needle valve, and the second needle valve are closed, and the remaining throttle valves and needle valves remain open. The high-temperature refrigerant first enters the first indoor heat exchanger from the compressor outlet. At this time, the first indoor heat exchanger serves as a condenser to heat the air with the refrigerant. After that, the refrigerant enters the tank body of the flash tank with a subcooler after expanding and reducing pressure through the first throttle valve. The flashed gaseous refrigerant enters the compressor through the air-increasing branch, and the liquid refrigerant enters the outdoor heat exchanger after expanding again through the second throttle valve. At this time, the outdoor heat exchanger serves as an evaporator to absorb heat from the air to heat the refrigerant. The evaporated refrigerant is separated by the gas-liquid separator, and the gaseous refrigerant is input into the compressor to complete the cycle.

[0013] In the above-mentioned subcooler gas injection heating mode, the components through which the refrigerant flows include a compressor, a first indoor heat exchanger, a first throttle valve, a subcooler flash tank, a third throttle valve, an outdoor heat exchanger, and a gas-liquid separator. At this time, the second throttle valve and the fourth throttle valve are closed, and the remaining throttle valves and needle valves remain open. The high-temperature refrigerant first enters the first indoor heat exchanger from the compressor outlet to heat the air, and then the cooled refrigerant enters two branches respectively. One branch enters the tank body of the subcooler flash tank through the first throttle valve, and the other branch directly enters the inside of the subcooler of the subcooler flash tank. By controlling the opening degree of the first needle valve, the flow rate of the refrigerant in the subcooler is adjusted to ensure that all the refrigerant in the flash tank body is vaporized. At this time, the low-pressure refrigerant in the tank body absorbs heat from the high-pressure refrigerant in the subcooler and evaporates into a gas, and then enters the compressor through the gas injection branch. The refrigerant in the subcooler is cooled and then expands through the third throttle valve and enters the outdoor evaporator to absorb evaporation from the air. The evaporated refrigerant is separated by the gas-liquid separator, and the gaseous refrigerant is input into the compressor to complete the cycle.

[0014] In the above-mentioned parallel dehumidification and heating mode, the components through which the refrigerant flows include a compressor, a first indoor heat exchanger, a first throttle valve, a subcooler flash tank, a second throttle valve, a third throttle valve, a second indoor heat exchanger, a fourth throttle valve, an outdoor heat exchanger, and a gas-liquid separator. At this time, the second needle valve is closed, and the remaining throttle valves and needle valves remain open. The high-temperature refrigerant first enters the first indoor heat exchanger from the compressor outlet to heat the air, and then the cooled refrigerant enters two branches respectively. One branch enters the tank body of the subcooler flash tank through the first throttle valve, and the other branch directly enters the inside of the subcooler of the subcooler flash tank. By controlling the opening degree of the first needle valve, the flow rate of the refrigerant in the subcooler is adjusted so that the refrigerant in the flash tank body is divided into gaseous refrigerant and liquid refrigerant after absorbing heat. The gaseous refrigerant enters the compressor through the gas injection branch, and the liquid refrigerant enters the outdoor heat exchanger to evaporate after passing through the second throttle valve, and then enters the gas-liquid separator for separation. The refrigerant in the subcooler is cooled and then expands through the third throttle valve and enters the second indoor heat exchanger. At this time, the second indoor heat exchanger is used as an evaporator to cool the air and condense the water vapor in the air. The refrigerant coming out of the second indoor heat exchanger then enters the gas-liquid separator through the fourth throttle valve for separation, and the separated gas enters the compressor to complete the cycle.

[0015] The beneficial effects of the present invention are as follows: When the ambient temperature is relatively low, the flash tank air make-up heating mode takes the flash tank as the key component, has strong heat exchange efficiency, can reduce the enthalpy value of the refrigerant at the inlet of the evaporator, increase the heat absorption of the refrigerant in the evaporator, and at the same time add an air make-up branch to increase the refrigerant flow rate in the condenser. When the ambient temperature decreases, the flash tank and the air make-up branch are prone to air make-up reflux problems. At this time, switching the heating mode to the subcooler air make-up heating mode can ensure the heating performance of the system at a lower ambient temperature. In the above parallel dehumidification heating mode, the second indoor heat exchanger and the outdoor heat exchanger are in parallel, and the pressure therein can be independently controlled, avoiding the frosting problem caused by too low evaporation pressure of the refrigerant in the second indoor heat exchanger; in addition, the refrigerant entering the second indoor heat exchanger is subcooled by the subcooler before throttling, which increases the enthalpy difference of the refrigerant at the inlet and outlet of the second indoor heat exchanger and enhances the dehumidification effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of an air-entering and enthalpy-increasing heat pump system according to an embodiment of the present invention.

[0017] DESCRIPTION OF THE REFERENCE NUMERALS

[0018] 1 - compressor; 2 - first indoor heat exchanger; 3 - flash tank with subcooler; 4 - second indoor heat exchanger; 5 - outdoor heat exchanger; 6 - gas-liquid separator; V1 - first throttle valve; V2 - second throttle valve; V3 - third throttle valve; V4 - fourth throttle valve; V5 - first needle valve; V6 - second needle valve; V7 - third needle valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present invention will be further described below in conjunction with the detailed embodiments and the drawings.

[0020] As Figure 1 shown, an air-entering and enthalpy-increasing heat pump system is composed of a compressor 1, a first indoor heat exchanger 2, a flash tank 3 with a subcooler, a second indoor heat exchanger 4, an outdoor heat exchanger 5, a gas-liquid separator 6, throttle valves V1 to V4, and needle valves V5 to V7.

[0021] The outlet of the compressor 1 is connected to the inlet of the first indoor heat exchanger 2. The outlet of the first indoor heat exchanger 2 has two branches. Among them, a first throttle valve V1 is provided on the first branch, and the first branch is connected to the inlet of the tank body of the flash tank 3 with a subcooler. The second branch is connected to the inlet of the subcooler of the flash tank 3 with a subcooler, and a needle valve V5 is provided on the second branch; the tank body of the flash tank 3 with a subcooler has a liquid phase outlet and a gas phase outlet. Among them, the gas phase outlet is connected to the air make-up inlet of the compressor 1 through a needle valve V7, and the liquid phase outlet is connected to the inlet of the outdoor heat exchanger 5 through a second throttle valve V2; the outlet of the outdoor heat exchanger 5 is connected to the inlet of the gas-liquid separator 6;

[0022] The outlet of the subcooler of the subcooler flash tank 3 is connected to a third throttle valve V3. The outlet of the third throttle valve V3 is divided into two branches. One branch is connected to the inlet of the outdoor heat exchanger 5 through a needle valve V6, and the other branch is connected to the inlet of the second indoor heat exchanger 4. The outlet of the second indoor heat exchanger 4 is connected to the inlet of the gas-liquid separator 6 through a fourth throttle valve V4.

[0023] The outlet of the gas-liquid separator 6 is connected to the inlet of the compressor 1.

[0024] Furthermore, as Figure 1 shown, a first needle valve V5 is provided on the second branch, a second needle valve V6 is provided on the pipeline between the outlet of the third throttle valve and the inlet of the outdoor heat exchanger, and a third needle valve V7 is provided on the pipeline between the gas phase outlet and the inlet of the compressor.

[0025] The refrigerant working medium in the system can be common refrigerants such as CO2, R134a, etc., and the types of refrigerants are not limited to one kind.

[0026] The gas-injected enhanced enthalpy heat pump system of the present invention can be applied to scenarios such as the thermal management of pure electric vehicles and indoor heating in buildings. Taking the application to pure electric vehicles as an example, this system can enable the pure electric vehicle to maintain high heating performance in a low-temperature environment and prevent frosting on the indoor dehumidification heat exchanger. Among them, the first indoor heat exchanger 2 in the system is the in-vehicle air heater of the electric vehicle, the second indoor heat exchanger 4 is the in-vehicle air dehumidification heat exchanger of the electric vehicle, and the outdoor heat exchanger 5 is the outdoor evaporator of the electric vehicle.

[0027] This gas-injected enhanced enthalpy heat pump system can achieve three heating modes: the flash tank gas injection heating mode, the subcooler gas injection heating mode, and the parallel dehumidification heating mode.

[0028] Among them, the flash tank gas injection heating mode is used when the pressure in the flash tank is higher than the gas injection pressure (the pressure at the gas injection port of the compressor). At this time, the flash tank, as a key component, has excellent heat exchange efficiency, which helps to reduce the enthalpy value at the inlet of the evaporator (outdoor heat exchanger) and improve the heating COP of the system.

[0029] When the outdoor temperature decreases, the evaporation pressure of the system and the pressure in the flash tank decrease. It is easy to have a situation where the gas replenishment pressure is higher than the pressure in the flash tank, resulting in gas replenishment backflow. The subcooler gas replenishment heating mode is used in the case of gas replenishment backflow. At this time, the refrigerant flow rate in the evaporator and the intermediate gas replenishment flow rate are separately controlled by two throttle valves, the third throttle valve V3 and the first throttle valve V1, which can ensure that the gas replenishment pressure will not be higher than the exhaust pressure, avoid the problem of gas replenishment backflow. At the same time, the intermediate gas replenishment reduces the exhaust temperature of the compressor 1, making the compression process closer to the isentropic process and reducing the power consumption of the compressor 1. The parallel dehumidification and heating mode is used when the indoor air humidity is relatively high. In the parallel dehumidification and heating mode, the second indoor heat exchanger 4 and the outdoor heat exchanger 5 operate in parallel, and the evaporation pressures of the outdoor and indoor evaporators can be freely controlled, effectively avoiding the problem of evaporator frosting.

[0030] In the above-mentioned flash tank gas replenishment heating mode, the valves V3 - V6 are closed, and the rest of the valves remain open. The components through which the refrigerant flows include the compressor 1, the first indoor heat exchanger 2, the first throttle valve V1, the flash tank 3 with a subcooler, the second throttle valve V2, the outdoor heat exchanger 5, and the gas-liquid separator 6. The high-temperature refrigerant first enters the first indoor heat exchanger 2 from the outlet of the compressor 1. At this time, the first indoor heat exchanger 2 acts as a condenser to heat the air with the refrigerant. After that, the refrigerant enters the tank body of the flash tank 3 with a subcooler after expanding and reducing pressure through the first throttle valve V1. The flashed gaseous refrigerant enters the compressor 1 through the gas replenishment branch, and the liquid refrigerant enters the outdoor heat exchanger 5 after expanding again through the second throttle valve V2. At this time, the outdoor heat exchanger 5 acts as an evaporator to absorb heat from the air to heat the refrigerant. The evaporated refrigerant is separated by the gas-liquid separator 6, and the gaseous refrigerant is input into the compressor 1 to complete the cycle.

[0031] In the above-mentioned subcooler gas replenishment heating mode, the second throttle valve V2 and the fourth throttle valve V4 are closed, and the rest of the valves remain open. The components through which the refrigerant flows include the compressor 1, the first indoor heat exchanger 2, the first throttle valve V1, the flash tank 3 with a subcooler, the third throttle valve V3, the outdoor heat exchanger 5, and the gas-liquid separator 6. The high-temperature refrigerant first enters the first indoor heat exchanger 2 from the outlet of the compressor 1 to heat the air. After that, the cooled refrigerant enters two branches respectively. One branch enters the tank body of the flash tank 3 with a subcooler through the first throttle valve V1, and the other branch directly enters the subcooler inside the flash tank 3 with a subcooler. The flow rate of the refrigerant in the subcooler is adjusted by controlling the opening degree of the first needle valve V5 to ensure that all the refrigerant in the tank body of the flash tank is vaporized. At this time, the low-pressure refrigerant in the tank body absorbs heat from the high-pressure refrigerant in the subcooler and evaporates into gas and then enters the compressor 1 through the gas replenishment branch. The refrigerant in the subcooler is cooled and then expands through the third throttle valve V3 and enters the outdoor evaporator 5 to absorb evaporation from the air. The evaporated refrigerant is separated by the gas-liquid separator 6, and the gaseous refrigerant is input into the compressor 1 to complete the cycle.

[0032] In the above-mentioned parallel dehumidification and heating mode, the second needle valve V6 is closed, and the other valves remain open. The components through which the refrigerant flows include the compressor 1, the first indoor heat exchanger 2, the first throttle valve V1, the subcooler flash tank 3, the second throttle valve V2, the third throttle valve V3, the second indoor heat exchanger 4, the fourth throttle valve V4, the outdoor heat exchanger 5, and the gas-liquid separator 6. The high-temperature refrigerant first enters the first indoor heat exchanger 2 from the outlet of the compressor 1 to heat the air, and then the cooled refrigerant enters two branches respectively. One branch enters the tank body of the subcooler flash tank 3 through the first throttle valve V1, and the other branch directly enters the inside of the subcooler of the subcooler flash tank 3. At this time, the opening degree of the first needle valve V5 is smaller than that of V5 in the subcooler gas supplement heating mode, so the refrigerant flow rate in the subcooler is relatively low, and the refrigerant in the flash tank body will not be completely vaporized. The refrigerant in the flash tank body is divided into gaseous refrigerant and liquid refrigerant after absorbing heat. Among them, the gaseous refrigerant enters the compressor 1 through the gas supplement branch, and the liquid refrigerant enters the outdoor heat exchanger 5 to evaporate after passing through the second throttle valve V2, and then enters the gas-liquid separator 6 for separation. The refrigerant in the subcooler expands through the third throttle valve V3 after cooling and enters the second indoor heat exchanger 4. At this time, the second indoor heat exchanger 4 is used as an evaporator to cool the air and condense the water vapor in the air. The refrigerant coming out of the second indoor heat exchanger 4 then enters the gas-liquid separator 6 through the fourth throttle valve V4 for separation, and the separated gas enters the compressor 1 to complete the cycle.

[0033] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. An air-injection enthalpy-increasing heat pump system, characterized in that: It includes a compressor, a first indoor heat exchanger, a flash tank with a subcooler, a second indoor heat exchanger, an outdoor heat exchanger and a gas-liquid separator; The outlet of the compressor is connected to the inlet of the first indoor heat exchanger, and the outlet of the first indoor heat exchanger has two branches, wherein the first branch is provided with a first throttle valve, the first branch is connected to the inlet of the tank body with a subcooler flash tank, and the second branch is connected to the subcooler inlet of the subcooler flash tank; the tank body with the subcooler flash tank has a liquid phase outlet and a gas phase outlet, wherein the gas phase outlet is connected to the air supply inlet of the compressor, and the liquid phase outlet is connected to the inlet of the outdoor heat exchanger through the second throttle valve; the outlet of the outdoor heat exchanger is connected to the inlet of the gas-liquid separator; The outlet of the subcooler with the flash tank of the subcooler is connected with a third throttle valve, the outlet of the third throttle valve is divided into two branches, one of which is connected with the inlet of the outdoor heat exchanger, and the other is connected with the inlet of the second indoor heat exchanger, and the outlet of the second indoor heat exchanger is connected with the inlet of the gas-liquid separator through the fourth throttle valve; The outlet of the gas-liquid separator is connected to the inlet of the compressor.

2. The air-injection enthalpy-increasing heat pump system according to claim 1, characterized in that: A first needle valve is arranged on the second branch, a second needle valve is arranged on the pipeline between the outlet of the third throttle valve and the inlet of the outdoor heat exchanger, and a third needle valve is arranged on the pipeline between the gas phase outlet and the inlet of the compressor.

3. The air-injection enthalpy-increasing heat pump system according to claim 1, characterized in that: The working fluid used in the system is refrigerant, and the refrigerant is CO2 or R134a.

4. The air-injection enthalpy-increasing heat pump system according to claim 1, characterized in that: The second indoor heat exchanger and the outdoor heat exchanger are in parallel, and the working pressures of the two can be controlled independently, thereby avoiding the frosting problem caused by the low evaporation pressure of the refrigerant in the second indoor heat exchanger; in addition, the refrigerant entering the second indoor heat exchanger is supercooled by the subcooler before throttling, thereby increasing the enthalpy difference of the refrigerant at the inlet and outlet of the second indoor heat exchanger and enhancing the dehumidification effect.

5. An operating method of the air-injection enthalpy-increasing heat pump system according to claim 2, characterized in that: The system has a flash tank air supply heating mode, a subcooler air supply heating mode, and a parallel dehumidification heating mode. Through the control of the throttle valve in the system, the system can switch between different working modes to meet the needs of the scene; Among them, the flash tank air supply heating mode is used when the pressure in the flash tank is higher than the compressor air supply pressure. In this mode, the third throttle valve, the fourth throttle valve, the first needle valve, and the second needle valve are closed, and the remaining throttle valves and needle valves remain open; The subcooler air supply heating mode is used in the case of air supply reflux, ensuring that the air supply pressure will not be higher than the exhaust pressure, avoiding the air supply reflux problem, and making the compression process closer to the isentropic process, reducing the power consumption of the compressor; in this mode, the second throttle valve and the fourth throttle valve are closed, and the other throttle valves and needle valves remain open; The parallel dehumidification and heating mode is used when the indoor air humidity is high. In the parallel dehumidification and heating mode, the second needle valve is closed, and the other throttle valves and needle valves remain open. The second indoor heat exchanger and the outdoor heat exchanger operate in parallel, which can freely control the evaporation pressure of the outdoor and indoor evaporators and effectively avoid the problem of frost on the evaporator.

6. The operating method of the air-supplementing enthalpy-increasing heat pump system according to claim 5, characterized in that: When the flash tank is in air supply heating mode, The high-temperature refrigerant first enters the first indoor heat exchanger from the compressor outlet. At this time, the first indoor heat exchanger is used as a condenser for the refrigerant to heat the air. Then, the refrigerant is expanded and reduced in pressure through the first throttle valve and then enters the tank body of the flash tank with a subcooler; the gas refrigerant after flash evaporation enters the compressor through the air supply branch, and the liquid refrigerant expands again through the second throttle valve and enters the outdoor heat exchanger. At this time, the outdoor heat exchanger acts as an evaporator to absorb heat from the air and heat the refrigerant; the evaporated refrigerant is separated by a gas-liquid separator, and the gas refrigerant is input into the compressor to complete the cycle.

7. The operating method of the air-supplementing enthalpy-increasing heat pump system according to claim 5, characterized in that: When the flash tank is in air supply heating mode, The high-temperature refrigerant first enters the first indoor heat exchanger from the compressor outlet to heat the air, and then the cooled refrigerant enters two branches respectively, one enters the tank body of the flash tank with a subcooler through the first throttle valve, and the other directly enters the inside of the subcooler with the flash tank with a subcooler; the flow rate of the refrigerant in the subcooler is adjusted by controlling the opening of the first needle valve to ensure that the refrigerant in the flash tank body is completely vaporized. At this time, the low-pressure refrigerant in the tank body absorbs heat from the high-pressure refrigerant in the subcooler and evaporates into gas and then enters the compressor through the air supply branch. The refrigerant in the subcooler is cooled and expanded through the third throttle valve and then enters the outdoor evaporator to absorb and evaporate from the air; the evaporated refrigerant is separated by a gas-liquid separator, and the gas refrigerant is input into the compressor to complete the cycle.

8. The operating method of the air-supplementing enthalpy-increasing heat pump system according to claim 5, characterized in that: In the parallel dehumidification and heating mode, the high-temperature refrigerant first enters the first indoor heat exchanger from the compressor outlet to heat the air, and then the cooled refrigerant enters two branches respectively, one enters the tank body of the flash tank with a subcooler through the first throttle valve, and the other directly enters the inside of the subcooler with the flash tank with a subcooler; the flow rate of the refrigerant in the subcooler is adjusted by controlling the opening of the first needle valve, so that the refrigerant in the flash tank body is divided into gas refrigerant and liquid refrigerant after absorbing heat, wherein the gas refrigerant enters the compressor through the air replenishing branch, and the liquid refrigerant enters the outdoor heat exchanger after passing through the second throttle valve to evaporate, and then enters the gas-liquid separator for separation; the refrigerant in the subcooler expands after cooling through the third throttle valve and enters the second indoor heat exchanger, at which time the second indoor heat exchanger is used as an evaporator to cool the air and condense the water vapor in the air; the refrigerant coming out of the second indoor heat exchanger then enters the gas-liquid separator through the fourth throttle valve for separation, and the separated gas enters the compressor to complete the cycle.

9. The operating method of the air-supplementing enthalpy-increasing heat pump system according to claim 8, characterized in that: In the parallel dehumidification and heating mode, the opening degree of the first needle valve is smaller than that in the flash tank air supply heating mode.

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