Air-source heat pump defrosting system with liquid-gas-liquid separator and its control method

Abstract

This invention relates to the field of vehicle heat pump system technology, and discloses an air-source heat pump defrosting system with a liquid-liquid separator. The system includes a compressor, an internal condenser, and an external heat exchanger. The compressor is connected to a four-way valve, which is connected to the gaseous refrigerant inlet of the liquid-liquid separator. The outlet of the four-way valve is connected to the compressor. The internal condenser is connected to the liquid refrigerant inlet of the liquid-liquid separator. The outlet of the liquid refrigerant inlet is connected to the external heat exchanger via a first full-flow electronic expansion valve, which is also connected to a four-way valve. A second full-flow electronic expansion valve is connected to the liquid refrigerant inlet and communicates with the external heat exchanger. A PTC heater is installed on the internal condenser, and a liquid level sensor is installed in the liquid storage chamber of the liquid-liquid separator. This invention also discloses a control method. The air-source heat pump defrosting system with a liquid-liquid separator and its control method can save defrosting time, allowing for faster restoration of heating mode and continued provision of heat to the passenger compartment.

Description

Technical Field

[0001] This invention relates to the field of vehicle heat pump systems and passenger compartment comfort control technology, specifically to an air source heat pump defrosting system with a liquid storage gas-liquid separator and its control method. Background Technology

[0002] In the defrost mode of new energy vehicles, an unreasonable defrost control method can affect the comfort of the passenger compartment. The traditional reverse cycle defrost control method directly uses a four-way valve to switch the direction and use the high-temperature refrigerant at the outlet of the condenser or high-pressure receiver to defrost the outdoor heat exchanger. However, the amount of refrigerant circulating during defrost is mainly controlled by the superheat at the outlet of the indoor heat exchanger, and cannot be adjusted according to the state of the frost layer and the real-time changes in the system status. Therefore, the defrost time may be too long. During defrost, the compressor can no longer provide heat to the passenger compartment, and may even provide unnecessary cooling. To ensure the comfort of the passenger compartment, the PTC needs to be turned on to consume electricity to compensate for this heat. Since the amount of refrigerant circulating during defrost is closely related to this electricity consumption, the control of the refrigerant circulation is very important for controlling the defrost time and electricity consumption. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the above-mentioned technologies by providing an air-source heat pump defrosting system with a liquid-gas-liquid separator and its control method. By adjusting the amount of refrigerant circulating in the defrosting cycle based on the real-time defrosting status and system operation, the defrosting time can be saved, allowing for a faster restoration of the heating mode and continued provision of heat to the passenger compartment.

[0004] To achieve the above objectives, the air-source heat pump defrosting system with a liquid-storage gas-liquid separator designed in this invention includes a compressor, an internal condenser, and an external heat exchanger. The compressor outlet is connected to the first port of a four-way valve, the second port of the four-way valve is connected to the inlet of the gaseous refrigerant in the gas-liquid separation chamber of the gas-liquid separator, the outlet of the gaseous refrigerant in the gas-liquid separation chamber of the gas-liquid separator is connected to the inlet of the compressor, the third port of the four-way valve is connected to the inlet of the internal condenser, and the outlet of the internal condenser is connected to the liquid-storage gas-liquid separator. The liquid refrigerant inlet of the liquid chamber, the liquid refrigerant outlet of the liquid storage chamber in the gas-liquid separator is connected to the inlet of the external heat exchanger through a first full-flow electronic expansion valve, the outlet of the external heat exchanger is connected to the fourth port of the four-way valve, the liquid refrigerant inlet of the liquid storage chamber in the gas-liquid separator is connected to a second full-flow electronic expansion valve, the other end of the second full-flow electronic expansion valve is connected to the inlet of the external heat exchanger, the internal condenser is equipped with a PTC heater, and the liquid storage chamber in the gas-liquid separator is equipped with a liquid level collector.

[0005] Preferably, a first fan is provided on the internal condenser, and a second fan is provided on the external heat exchanger.

[0006] Preferably, the compressor, four-way valve, first full-flow electronic expansion valve, second full-flow electronic expansion valve, PTC heater, and level sensor are connected to a controller with memory function.

[0007] A control method for the air-source heat pump defrosting system with a liquid-gas separator, wherein the operating mode is divided into a heating mode and a defrosting mode according to the heating request and defrosting request of the passenger compartment, and when in heating mode:

[0008] The first and third ports of the four-way valve are connected, and the second and fourth ports are connected. The high-temperature and high-pressure refrigerant fluid, after being compressed by the compressor, enters the internal condenser through the channel formed by the first and third ports of the four-way valve, dissipating heat into the passenger compartment and heating the passenger compartment. Then it enters the liquid storage chamber of the gas-liquid separator, where it is further cooled to obtain subcooling. After entering the first full-flow electronic expansion valve for throttling and pressure reduction, it enters the external heat exchanger, where it absorbs heat from the environment and becomes a low-temperature and low-pressure gas. It then enters the gas-liquid separation chamber of the gas-liquid separator through the channel formed by the second and fourth ports of the four-way valve, absorbs heat from the refrigerant in the liquid storage chamber, and returns to the inlet of the compressor to complete the cycle.

[0009] When in defrost mode:

[0010] The first and fourth ports of the four-way valve are connected, as are the second and third ports. The high-temperature, high-pressure refrigerant fluid, compressed by the compressor, enters the external heat exchanger through the channel formed by the first and fourth ports of the four-way valve. After releasing heat and defrosting, it enters the liquid refrigerant outlet of the liquid storage chamber in the gas-liquid separator through the first full-flow electronic expansion valve, and then enters the liquid refrigerant inlet of the liquid storage chamber in the gas-liquid separator through the second full-flow electronic expansion valve. At this time, a high-low pressure difference is formed between the liquid refrigerant inlet and outlet of the liquid storage chamber in the gas-liquid separator. The liquid in the storage chamber is drawn into the internal condenser to participate in the defrosting cycle. It then enters the gas-liquid separation chamber of the gas-liquid separator through the channel formed by the second and third ports of the four-way valve, absorbs the heat of the liquid refrigerant in the storage chamber, and returns to the compressor inlet to complete the cycle. At this time, the PTC heater is turned on to heat the refrigerant in the internal condenser and the air in the passenger compartment.

[0011] Preferably, the external heat exchanger is equipped with a second fan, which is turned off when in defrost mode.

[0012] Preferably, in defrost mode, the liquid level in the storage chamber of the gas-liquid separator is changed by adjusting the second full-flow electronic expansion valve under different ambient temperatures until the optimal initial liquid level Lopt is reached. The calculation method for the optimal initial liquid level Lopt includes the following steps:

[0013] A) The initial liquid level Lset and the liquid level rise rate Vset of the start of the defrosting cycle are obtained through the liquid level acquisition device;

[0014] B) Record the defrosting time Δt of this defrosting cycle. The defrosting time Δt is the time interval from entering the defrosting mode to exiting the defrosting mode in this cycle. Record the curve P1-t of the compressor power change over time and the curve P2-t of the PTC heater power change over time in this defrosting cycle.

[0015] C) Integrate the two curves to obtain the system's energy consumption W1 and W2 within the defrosting time Δt of this defrosting cycle, and obtain the total energy consumption W = W1 + W2;

[0016] D) If the defrosting time Δt is shorter in the next defrosting cycle compared to the previous defrosting cycle, then increase the liquid level rise rate Vset; otherwise, determine the current liquid level rise rate Vset as the optimal liquid level rise rate Vopt.

[0017] E) Control according to the optimal liquid level rise rate Vopt. If the total energy consumption increases in the next defrost cycle compared to the previous defrost cycle, then raise the initial liquid level Lset; otherwise, determine the current initial liquid level Lset as the optimal initial liquid level Lopt.

[0018] The principle of this invention is as follows:

[0019] In heating mode, the refrigerant in the gas-liquid separation chamber and the liquid storage chamber of the gas-liquid separator exchanges heat, increasing the evaporation temperature and delaying frosting. In defrosting mode, the refrigerant in the liquid storage chamber is drawn into the defrosting cycle due to the pressure difference, increasing the refrigerant circulation volume during the defrosting process. This can simultaneously increase both the evaporation and condensation temperatures. On the one hand, the increase in condensation temperature can improve the defrosting speed; on the other hand, the increase in evaporation temperature reduces the heat exchange temperature difference between the air temperature inside the passenger compartment and the evaporation temperature.

[0020] However, at this point, the refrigerant flow rate participating in the cycle increases, and the variation in the amount of cooling absorbed by the internal condenser from the passenger compartment is uncertain. To maintain the same supply air temperature, the cooling input for defrosting is compensated for by heating with a PTC heater to meet comfort requirements. Therefore, the PTC heater power is a significant portion of defrosting energy consumption. The refrigerant flow rate in the receiver participating in the defrost cycle also determines the defrost rate and system operating characteristics. A larger flow rate results in a faster defrost rate. As the frost layer gradually decreases, heat exchange with the external heat exchanger weakens, leading to excessively high system pressure, which is detrimental to stable system operation. Therefore, as defrosting progresses, the frost layer is in a dynamic process, and the amount of receiver participating in the defrost cycle should also change in real time to simultaneously meet defrosting requirements and system operational stability requirements.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. By introducing a gas-liquid separator with liquid storage function and using a liquid level gauge to feed back the liquid level signal, the amount of refrigerant circulating in the defrost cycle can be adjusted according to the real-time defrost status and system operation. This can save defrost time and allow for faster restoration of heating mode to continue providing heat to the passenger compartment.

[0023] 2. By using a controller with memory function, the initial liquid level of the gas-liquid separator in each defrost cycle is recorded, and the total power consumption of the compressor and PTC in each defrost cycle is calculated, which helps to improve the system energy consumption during defrosting. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the air source heat pump defrosting system with a liquid storage gas-liquid separator according to the present invention.

[0025] Figure 2 for Figure 1 Schematic diagram of a gas-liquid separator;

[0026] Figure 3 This is a flowchart illustrating the calculation of the optimal initial liquid level and the optimal initial liquid level Lopt in the control method of the air source heat pump defrosting system with a liquid storage gas-liquid separator of the present invention.

[0027] The components in the diagram are labeled as follows:

[0028] 1. Compressor; 2. Internal condenser; 3. External heat exchanger; 4. Four-way valve; 4. First port 41; 4. Second port 42; 4. Third port 43; 4. Fourth port 44; 5. Gas-liquid separator; 5. Gas-liquid separation chamber; 5. Gaseous refrigerant inlet; 5. Gaseous refrigerant outlet; 5. Liquid storage chamber; 5. Liquid refrigerant inlet; 5. Liquid refrigerant outlet; 5. Liquid level sensor; 5. First full-flow electronic expansion valve; 6. Second full-flow electronic expansion valve; 7. PTC heater; 8. First fan; 9. Second fan; 10. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 and Figure 2 As shown, an air source heat pump defrosting system with a liquid-liquid separator includes a compressor 1, an internal condenser 2, and an external heat exchanger 3. The outlet of the compressor 1 is connected to the first port 41 of a four-way valve 4. The second port 42 of the four-way valve 4 is connected to the gaseous refrigerant inlet 511 of the gas-liquid separation chamber 51 in the gas-liquid separator 5. The gaseous refrigerant outlet 512 of the gas-liquid separation chamber 51 in the gas-liquid separator 5 is connected to the inlet of the compressor 1. The third port 43 of the four-way valve 4 is connected to the inlet of the internal condenser 2. The outlet of the internal condenser 2 is connected to the liquid-liquid separator 5. The liquid refrigerant inlet 521 in the gas-liquid separator 5 has a liquid refrigerant outlet 522 in the liquid storage chamber 52 connected to the inlet of the external heat exchanger 3 via a first full-flow electronic expansion valve 6. The outlet of the external heat exchanger 3 is connected to the fourth port 44 of a four-way valve 4. The liquid refrigerant inlet 521 in the liquid storage chamber 52 of the gas-liquid separator 5 is connected to a second full-flow electronic expansion valve 7. The other end of the second full-flow electronic expansion valve 7 is connected to the inlet of the external heat exchanger 3. A PTC heater 8 is provided on the internal condenser 2. A liquid level collector 53 is provided in the liquid storage chamber 52 of the gas-liquid separator 5.

[0031] In other embodiments, a first fan 9 is provided on the internal condenser 2, and a second fan 10 is provided on the external heat exchanger 3.

[0032] In addition, the compressor 1, four-way valve 4, first full-flow electronic expansion valve 6, second full-flow electronic expansion valve 7, PTC heater 8 and liquid level acquisition device 53 are connected to a controller with memory function, which records the initial liquid level of gas-liquid separator 5 in each defrost cycle, and according to the total power consumption of compressor and PTC in each defrost cycle, it is beneficial to improve the system energy consumption during defrosting.

[0033] In this embodiment, the air-source heat pump defrosting system with a liquid storage gas-liquid separator operates in two modes: heating mode and defrosting mode, based on the passenger compartment's heating and defrosting requests. When in heating mode:

[0034] The first port 41 and the third port 43 of the four-way valve 4 are connected, and the second port 42 and the fourth port 44 are connected. The high-temperature and high-pressure refrigerant fluid after being compressed by the compressor 1 enters the internal condenser 2 through the channel formed by the first port 41 and the third port 43 of the four-way valve 4, dissipating heat into the crew compartment and heating the crew compartment. Then it enters the liquid storage chamber 52 of the gas-liquid separator 5, is further cooled to obtain subcooling, and enters the first full-flow electronic expansion valve 6 for throttling and pressure reduction before entering the external heat exchanger 3. It absorbs heat from the environment and becomes a low-temperature and low-pressure gas. It enters the gas-liquid separation chamber 51 of the gas-liquid separator 5 through the channel formed by the second port 42 and the fourth port 44 of the four-way valve 4, absorbs heat from the refrigerant in the liquid storage chamber 52, and returns to the inlet of the compressor 1 to complete the cycle.

[0035] When in defrost mode:

[0036] The first port 41 and the fourth port 44 of the four-way valve 4 are connected, and the second port 42 and the third port 43 are connected. The high-temperature and high-pressure refrigerant fluid compressed by the compressor 1 enters the external heat exchanger 3 through the channel formed by the first port 41 and the fourth port 44 of the four-way valve 4. After releasing heat and defrosting, it enters the liquid refrigerant outlet 522 of the liquid storage chamber 52 in the gas-liquid separator 5 through the first full-flow electronic expansion valve 6, and enters the liquid refrigerant inlet 521 of the liquid storage chamber 52 in the gas-liquid separator 5 through the second full-flow electronic expansion valve 7. At this time, the gas and liquid... In the separator 5, the liquid refrigerant inlet 521 and liquid refrigerant outlet 522 of the liquid storage chamber 52 form a high-low pressure difference. The liquid in the liquid storage chamber 52 is drawn into the internal condenser 2 to participate in the defrosting cycle. It enters the gas-liquid separation chamber 51 of the gas-liquid separator 5 through the channel formed by the second port 42 and the third port 43 of the four-way valve 4. After absorbing the heat of the liquid refrigerant in the liquid storage chamber 52, it returns to the inlet of the compressor 1 to complete the cycle. At this time, the PTC heater 8 is turned on to heat the refrigerant in the internal condenser 2 and the air in the crew compartment.

[0037] When the external heat exchanger 3 is equipped with a second fan 10, the second fan 10 is turned off when in defrost mode.

[0038] Furthermore, the refrigerant flow rate participating in the defrost cycle in the liquid storage chamber 52 simultaneously determines the defrost rate and system operating characteristics. A larger flow rate results in a faster defrost rate. However, as the frost layer gradually decreases, heat exchange in the external heat exchanger 3 weakens, leading to excessively high system pressure, which is detrimental to stable system operation. Therefore, as defrosting progresses, the frost layer is in a dynamic process, and the amount of liquid participating in the defrost cycle should also change in real time. Figure 3 As shown, the liquid level in the storage chamber 52 of the gas-liquid separator 5 is changed by adjusting the second full-flow electronic expansion valve 7 under different ambient temperatures until the optimal initial liquid level Lopt is reached. The calculation method for the optimal initial liquid level Lopt includes the following steps:

[0039] A) The initial liquid level Lset and the liquid level rise rate Vset of the start of the defrosting cycle are obtained by the liquid level acquisition device 53;

[0040] B) Record the defrosting time Δt of this defrosting cycle. The defrosting time Δt is the time interval from entering the defrosting mode to exiting the defrosting mode in this cycle. Record the curve P1-t of the compressor power change over time and the curve P2-t of the PTC heater power change over time in this defrosting cycle.

[0041] C) Integrate the two curves to obtain the system's energy consumption W1 and W2 within the defrosting time Δt of this defrosting cycle, and obtain the total energy consumption W = W1 + W2;

[0042] D) If the defrosting time Δt is shorter in the next defrosting cycle compared to the previous defrosting cycle, then increase the liquid level rise rate Vset; otherwise, determine the current liquid level rise rate Vset as the optimal liquid level rise rate Vopt.

[0043] E) Control according to the optimal liquid level rise rate Vopt. If the total energy consumption increases in the next defrost cycle compared to the previous defrost cycle, then raise the initial liquid level Lset; otherwise, determine the current initial liquid level Lset as the optimal initial liquid level Lopt.

[0044] This invention relates to an air-source heat pump defrosting system with a liquid storage gas-liquid separator and its control method. It introduces a gas-liquid separator 5 with a liquid storage function, utilizes a level gauge to provide feedback on the liquid level signal, and adjusts the refrigerant circulation volume participating in the defrosting cycle based on the real-time defrosting status and system operation. This saves defrosting time, allowing for faster restoration of heating mode and continued provision of heat to the passenger compartment. Furthermore, a controller with memory function records the initial liquid level of the gas-liquid separator for each defrosting cycle, and based on the total power consumption of the compressor and PTC for each defrosting cycle, it helps improve system energy consumption during defrosting.

Claims

1. A control method for an air source heat pump defrost system with a liquid accumulator gas-liquid separator, the method comprising: An air-source heat pump defrosting system includes a compressor (1), an internal condenser (2), and an external heat exchanger (3). The outlet of the compressor (1) is connected to the first port (41) of a four-way valve (4). The second port (42) of the four-way valve (4) is connected to the gaseous refrigerant inlet (511) of the gas-liquid separation chamber (51) in a gas-liquid separator (5). The gaseous refrigerant outlet (512) of the gas-liquid separation chamber (51) in the gas-liquid separator (5) is connected to the inlet of the compressor (1). The third port (43) of the four-way valve (4) is connected to the inlet of the internal condenser (2). The outlet of the internal condenser (2) is connected to the liquid refrigerant inlet (521) of the liquid storage chamber (52) in the gas-liquid separator (5). The liquid refrigerant outlet (522) of the gas-liquid separator (5) is connected to the inlet of the external heat exchanger (3) through the first full-flow electronic expansion valve (6). The outlet of the external heat exchanger (3) is connected to the fourth port (44) of the four-way valve (4). The liquid refrigerant inlet (521) of the liquid storage chamber (52) in the gas-liquid separator (5) is connected to the second full-flow electronic expansion valve (7). The other end of the second full-flow electronic expansion valve (7) is connected to the inlet of the external heat exchanger (3). The internal condenser (2) is equipped with a PTC heater (8). The liquid storage chamber (52) in the gas-liquid separator (5) is equipped with a liquid level collector (53). The control method divides the operating mode into heating mode and defrosting mode according to the heating request and defrosting request of the crew cabin. When in heating mode: ​ The first port (41) and the third port (43) of the four-way valve (4) are connected, and the second port (42) and the fourth port (44) are connected. The high-temperature and high-pressure refrigerant fluid compressed by the compressor (1) enters the internal condenser (2) through the channel formed by the first port (41) and the third port (43) of the four-way valve (4), dissipates heat into the crew compartment, and heats the crew compartment. Then it enters the liquid storage chamber (52) of the gas-liquid separator (5), is further cooled to obtain subcooling, enters the first full-flow electronic expansion valve (6) for throttling and pressure reduction, and enters the external heat exchanger (3). It absorbs heat from the environment and becomes a low-temperature and low-pressure gas. It enters the gas-liquid separation chamber (51) of the gas-liquid separator (5) through the channel formed by the second port (42) and the fourth port (44) of the four-way valve (4), absorbs the heat of the refrigerant in the liquid storage chamber (52), and returns to the inlet of the compressor (1) to complete the cycle. When in defrost mode: The first port (41) and the fourth port (44) of the four-way valve (4) are connected, and the second port (42) and the third port (43) are connected. The high-temperature and high-pressure refrigerant fluid compressed by the compressor (1) enters the external heat exchanger (3) through the channel formed by the first port (41) and the fourth port (44) of the four-way valve (4). After releasing heat and defrosting, it enters the liquid refrigerant outlet (522) of the liquid storage chamber (52) in the gas-liquid separator (5) through the first full-flow electronic expansion valve (6), and enters the liquid refrigerant inlet (521) of the liquid storage chamber (52) in the gas-liquid separator (5) through the second full-flow electronic expansion valve (7). When the liquid refrigerant inlet (521) and liquid refrigerant outlet (522) of the liquid storage chamber (52) in the gas-liquid separator (5) form a high-low pressure difference, the liquid in the liquid storage chamber (52) is drawn into the internal condenser (2) to participate in the defrosting cycle. It enters the gas-liquid separation chamber (51) of the gas-liquid separator (5) through the channel formed by the second port (42) and the third port (43) of the four-way valve (4). After absorbing the heat of the liquid refrigerant in the liquid storage chamber (52), it returns to the inlet of the compressor (1) to complete the cycle. At this time, the PTC heater (8) is turned on to heat the refrigerant in the internal condenser (2) and the air in the crew compartment. When in defrost mode, the liquid level in the storage chamber (52) of the gas-liquid separator (5) is changed by adjusting the second full-flow electronic expansion valve (7) under different ambient temperatures until the optimal initial liquid level Lopt is reached. The calculation method for the optimal initial liquid level Lopt includes the following steps: A) The initial liquid level Lset and the liquid level rise rate Vset of the start of the defrosting cycle are obtained by the liquid level acquisition device (53); B) Record the defrosting time Δt of this defrosting cycle. The defrosting time Δt is the time interval from entering the defrosting mode to exiting the defrosting mode in this cycle. Record the curve P1-t of the compressor power change over time and the curve P2-t of the PTC heater power change over time in this defrosting cycle. C) Integrate the two curves to obtain the system's energy consumption W1 and W2 within the defrosting time Δt of this defrosting cycle, and obtain the total energy consumption W = W1 + W2; D) If the defrosting time Δt is shorter in the next defrosting cycle compared to the previous defrosting cycle, then increase the liquid level rise rate Vset; otherwise, determine the current liquid level rise rate Vset as the optimal liquid level rise rate Vopt. E) Control according to the optimal liquid level rise rate Vopt. If the total energy consumption increases in the next defrost cycle compared to the previous defrost cycle, then raise the initial liquid level Lset; otherwise, determine the current initial liquid level Lset as the optimal initial liquid level Lopt.

2. The control method of the air source heat pump defrosting system with liquid accumulator gas-liquid separator according to claim 1, characterized in that: The internal condenser (2) is equipped with a first fan (9), and the external heat exchanger (3) is equipped with a second fan (10).

3. The control method for the air source heat pump defrosting system with a liquid-gas-liquid separator according to claim 1, characterized in that: The compressor (1), four-way valve (4), first full-flow electronic expansion valve (6), second full-flow electronic expansion valve (7), PTC heater (8) and level collector (53) are connected to a controller with memory function.

4. The control method for the air source heat pump defrosting system with a liquid-gas-liquid separator according to claim 1, characterized in that: The external heat exchanger (3) is equipped with a second fan (10), which is turned off when in defrost mode.

Images