Heat pump device and control method thereof

Abstract

The invention provides a heat pump device and a control method thereof, and relates to the technical field of heat pumps. The heat energy device comprises a compressor, a four-way valve, a first heat exchanger, a second heat exchanger, a throttling element and a liquid storage device. An inlet and an outlet of the compressor are connected to a first connector and a second connector of the four-way valve respectively, the first heat exchanger, the throttling element and the second heat exchanger are sequentially connected through pipelines, the first heat exchanger further communicates with a third connector of the four-way valve, and the second heat exchanger further communicates with a fourth connector of the four-way valve to form a refrigerant circulation flow path. An inlet of the liquid storage device is connected to a pipeline between the second heat exchanger and the throttling element through a first pipeline, and the first pipeline is provided with a first control valve. An inlet of the liquid storage device is connected to a pipeline between the first heat exchanger and the throttling element through a second pipeline, and the second pipeline is provided with a second control valve. The heat exchange efficiency can be improved.

Description

Technical Field

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

[0002] In a heat pump device in which the heat source fluid is external air and the load fluid is water, the refrigerant flow path volume of the heat source heat exchanger is generally larger than the refrigerant flow path volume of the load heat exchanger. In addition, the volume ratio of the high-pressure refrigerant liquid in the refrigerant flow path of the condenser is generally larger than the volume ratio of the low-pressure refrigerant liquid in the refrigerant flow path of the evaporator.

[0003] The optimal refrigerant amount in the cooling mode when the heat source heat exchanger is used as a condenser is greater than the optimal refrigerant amount in the heating mode when the load heat exchanger is used as a condenser. If the optimal refrigerant amount in the cooling mode is set to the injection refrigerant amount, the problem of excess circulating refrigerant will occur in the heating mode. In addition, the excess refrigerant is stored in the load heat exchanger in the state of high-pressure liquid, which hinders heat transfer and reduces the circulation efficiency.

[0004] Therefore, in the heat pump device, the necessary refrigerant amount under the cooling rated condition is used as the injection refrigerant amount. At the same time, the liquid storage device that can convert the difference between the injection refrigerant amount and the optimal refrigerant amount under the heating rated condition into the volume of the high-pressure liquid under the heating rated condition is connected to the refrigerant pipe connecting the expansion valve and the load heat exchanger through a connecting pipe. All the excess refrigerant generated under the heating rated condition is stored in the liquid storage device as high-pressure liquid, which can prevent the excess refrigerant from being stored in the load heat exchanger in the state of high-pressure liquid, hindering heat transfer and reducing cycle efficiency.

[0005] However, in actual use, the optimal amount of refrigerant will change according to various operating conditions, but the volume of the liquid storage tank is fixed. There is a problem that the circulating refrigerant amount is insufficient depending on the operating conditions, which reduces the circulation efficiency. Summary of the invention

[0006] The problem to be solved by the present invention is that when the volume of the liquid storage tank is constant, there is a problem that the amount of circulating refrigerant is insufficient depending on the operating conditions, which reduces the circulation efficiency.

[0007] In order to solve the above problems, the present application provides a heat pump device and a control method thereof, which can improve the heat exchange efficiency of the heat pump.

[0008] In a first aspect, the present invention provides a heat pump device including a compressor, a four-way valve, a first heat exchanger, a second heat exchanger, a throttling element and a liquid reservoir;

[0009] The compressor inlet and outlet are connected to the first interface and the second interface of the four-way valve respectively, the first heat exchanger, the throttling element and the second heat exchanger are connected in sequence through pipelines, and the first heat exchanger is also connected to the third interface of the four-way valve, and the second heat exchanger is also connected to the fourth interface of the four-way valve to form a refrigerant circulation flow path;

[0010] The second heat exchanger is used for exchanging heat with the heat source fluid;

[0011] The inlet of the liquid reservoir is connected to the pipeline between the second heat exchanger and the throttling element through a first pipeline, and the first pipeline is provided with a first control valve;

[0012] The inlet of the liquid reservoir is connected to the pipeline between the first heat exchanger and the throttling element through a second pipeline, and the second pipeline is provided with a second control valve.

[0013] Under cooling or heating conditions, one side of the throttling element is the high-pressure side and the other side is the low-pressure side, and the first pipe and the second pipe are connected to the inlet of the liquid reservoir, and are respectively connected to the two sides of the throttling element, and the first control valve and the second control valve are correspondingly arranged, so that when the amount of refrigerant is insufficient, the control valve on the high-pressure side of the throttling element can be closed, and the control valve on the low-pressure side can be opened, so that the refrigerant in the liquid reservoir can flow into the circulation pipeline. When the amount of refrigerant is excessive, the control valve on the high-pressure side of the throttling element can be opened, and the control valve on the low-pressure side can be closed, so that the refrigerant can flow into the liquid reservoir. This can prevent the insufficient or excessive amount of circulating refrigerant from affecting the circulation heat exchange efficiency of the heat pump.

[0014] In an optional embodiment, the outlet of the liquid reservoir is connected to the pipeline connecting the second heat exchanger and the four-way valve through a third pipeline.

[0015] The present application provides a third pipeline so as to release the pressure when the liquid reservoir exceeds the allowable pressure, thereby avoiding damage to the liquid reservoir.

[0016] In an optional embodiment, the third pipeline is provided with a pressure relief valve.

[0017] A pressure relief valve is provided so that pressure can be directly relieved according to the pressure of the reservoir.

[0018] In an optional embodiment, both the first control valve and the second control valve are solenoid valves.

[0019] The first control valve and the second control valve are both configured as solenoid valves for easy control.

[0020] In an optional embodiment, the exhaust pipe of the compressor is provided with a pressure sensor, the first heat exchanger is provided with a first temperature sensor, and the second heat exchanger is provided with a second temperature sensor.

[0021] The pressure sensor, the first temperature sensor and the second temperature sensor are provided to facilitate calculation of the corresponding degree of supercooling.

[0022] In an optional embodiment, the heat pump device further includes a controller, which is used to receive information sent by the pressure sensor, the first temperature sensor and the second temperature sensor, and control the opening and closing of the first control valve and the second control valve according to the information.

[0023] Setting the controller to achieve automatic control according to preset adjustments makes it more convenient to use.

[0024] In a second aspect, the present invention provides a control method for a heat pump device to control the heat pump device according to any one of the aforementioned embodiments, the method comprising:

[0025] Obtaining an operating mode of a heat pump device;

[0026] When the heat pump device is in a heating operation mode, obtaining the subcooling degree of the first heat exchanger, and controlling the first control valve and the second control valve to open or close according to the subcooling degree of the first heat exchanger;

[0027] When the heat pump device is in a cooling operation mode, the subcooling degree of the second heat exchanger is obtained, and the first control valve and the second control valve are controlled to be opened or closed according to the subcooling degree of the second heat exchanger.

[0028] Since the subcooling degree can reflect whether the refrigerant in the circulation pipeline is in a state of shortage or surplus, the refrigerant circulation amount can be accurately determined by controlling the opening or closing of the first control valve and the second control valve using the subcooling degree.

[0029] In an optional embodiment, the step of obtaining the subcooling degree of the first heat exchanger includes:

[0030] Obtaining the pressure at the compressor outlet and the refrigerant temperature of the first heat exchanger, and calculating the subcooling degree of the first heat exchanger according to the pressure at the compressor outlet and the refrigerant temperature of the first heat exchanger;

[0031] The step of obtaining the subcooling degree of the second heat exchanger comprises:

[0032] The pressure at the compressor outlet and the refrigerant temperature of the second heat exchanger are obtained, and the subcooling degree of the second heat exchanger is calculated according to the pressure at the compressor outlet and the refrigerant temperature of the second heat exchanger.

[0033] In an optional embodiment, the step of controlling the first control valve and the second control valve to open or close according to the subcooling degree of the first heat exchanger includes:

[0034] Determining whether the degree of subcooling of the first heat exchanger is greater than a first threshold;

[0035] If the degree of subcooling of the first heat exchanger is less than a first threshold, the first control valve is controlled to be opened and the second control valve is controlled to be closed;

[0036] If the degree of subcooling of the first heat exchanger is greater than a first threshold, the second control valve is controlled to be opened and the first control valve is controlled to be closed;

[0037] If the subcooling degree of the first heat exchanger is equal to a first threshold, the second control valve and the first control valve are both controlled to be closed.

[0038] Therefore, in the heating state, the states of the first control valve and the second control valve can be adjusted in real time according to the change of the supercooling degree, so that the refrigerant circulation amount is maintained in the optimal range.

[0039] In an optional embodiment, the step of controlling the first control valve and the second control valve to open or close according to the subcooling degree of the second heat exchanger includes:

[0040] determining whether the degree of subcooling of the second heat exchanger is greater than a second threshold;

[0041] If the subcooling degree of the second heat exchanger is less than a first threshold value, the first control valve is controlled to be closed and the second control valve is controlled to be opened;

[0042] If the subcooling degree of the second heat exchanger is greater than a first threshold value, the second control valve is controlled to be closed and the first control valve is controlled to be opened;

[0043] If the subcooling degree of the second heat exchanger is equal to a first threshold value, the second control valve and the first control valve are both controlled to be closed.

[0044] Therefore, in the heating state, the states of the first control valve and the second control valve can be adjusted in real time according to the change of the supercooling degree, so that the refrigerant circulation amount is maintained in the optimal range. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of an existing structure with a liquid reservoir;

[0046] Figure 2 A schematic structural diagram of a liquid storage device provided in an embodiment of the present invention.

[0047] Icon: 100-heat pump device; 1-compressor; 2-four-way valve; 3-first heat exchanger; 4-second heat exchanger; 5-throttling element; 6-liquid reservoir; 7-first pipeline; 8-first control valve; 9-second pipeline; 10-second control valve; 11-first pipeline; 13-second pipeline; 14-third pipeline; 15-fourth pipeline; 16-fifth pipeline; 17-sixth pipeline; 18-third pipeline; 19-pressure relief valve; 20-pressure sensor; 21-first temperature sensor; 22-second temperature sensor. DETAILED DESCRIPTION

[0048] In a heat pump where the heat source fluid is external air and the load fluid is water, the refrigerant flow path volume of the heat source heat exchanger is generally larger than the refrigerant flow path volume of the load heat exchanger. In addition, the volume ratio of the high-pressure refrigerant liquid in the refrigerant flow path of the condenser is generally larger than the volume ratio of the low-pressure refrigerant liquid in the refrigerant flow path of the evaporator. The optimal refrigerant amount in the cooling mode where the heat source heat exchanger is used as a condenser is larger than the optimal refrigerant amount in the heating mode where the load heat exchanger is used as a condenser. If the optimal refrigerant amount in the cooling mode is set to the perfusion refrigerant amount, the problem of excess circulating refrigerant will occur in the heating mode. In addition, the excess refrigerant is stored in the load heat exchanger in the form of high-pressure liquid, which hinders heat transfer and reduces the circulation efficiency. Figure 1 In the existing heat pump, the necessary refrigerant amount under the cooling rated condition is used as the injection refrigerant amount. At the same time, the difference between the injection refrigerant amount and the optimal refrigerant amount under the heating rated condition can be converted into the volume of the high-pressure liquid under the heating rated condition. The liquid storage device is connected to the refrigerant pipe connecting the expansion valve and the load heat exchanger through a connecting pipe. All the excess refrigerant generated under the heating rated condition is stored in the liquid storage device as high-pressure liquid, which can prevent the excess refrigerant from being stored in the load heat exchanger in the state of high-pressure liquid, hindering heat transfer and reducing cycle efficiency.

[0049] For example, the refrigerant flow path volume of the heat source heat exchanger in the existing heat pump is V A =.0L, the refrigerant flow volume of the load heat exchanger is V B = 1.5L. In addition, the volume ratio of the high-pressure refrigerant liquid in the refrigerant flow path of the condenser is generally greater than the volume ratio of the low-pressure refrigerant liquid in the refrigerant flow path of the evaporator. Here, the volume ratio of the high-pressure refrigerant liquid in the refrigerant flow path volume of the condenser is n cnd =0.25, the volume ratio of low-pressure refrigerant liquid in the refrigerant flow path volume of the evaporator is n evp =0.15.

[0050] The heat source fluid temperature under the rated heating condition is 7.0℃, the load fluid outlet temperature is 45.0℃, the condensation temperature is 50.0℃, the evaporation temperature is 0.0℃, and the high pressure liquid density is ρ cnd,heat =0.908kg / L, low pressure liquid density is ρevp,heat =1.17kg / L, the optimal refrigerant quantity is G according to formula 1 opt,heat =1.18kg.

[0051] G opt,heat =η evp ·V A ·ρ evp,heat +η cnd ·V B ·ρ cnd,heat (1)

[0052] The heat source fluid temperature of the refrigeration rated condition is 35.0℃, the load fluid outlet temperature is 7.0℃, the condensing temperature is 45.0℃, the evaporating temperature is 3.0℃, and the high pressure liquid density is ρ cnd,cool =0.944kg / L, low pressure liquid density is ρ evp,cool =1.1kg / L, the optimal refrigerant quantity is G according to formula 2 opt,cool =1.78kg.

[0053] G opt,cool =η cnd ·V A ·ρ cnd,cool +η evp ·V B ·ρ evp,cool (2)

[0054] Here, it is assumed that the refrigerant amount of the heat pump is equal to the optimal refrigerant amount under the rated cooling condition, G chg =1.78kg, then the volume of the liquid storage tank is: Convert the difference between the amount of refrigerant injected and the optimal amount of refrigerant under the rated heating condition into the volume of high-pressure refrigerant liquid. From formula 3, we know that V rcv =0.2L.

[0055] V rcv =(G chg -G opt,heat ) / ρ cnd,heat (3)

[0056] Under the rated heating condition, the liquid receiver is filled with high-pressure refrigerant liquid. The amount of refrigerant stored in the liquid receiver is obtained according to formula 4. rcv = 0.01kg, the mass of the refrigerant circulation is G = 1.18kg according to formula 5. Therefore, the circulating refrigerant amount G (1.18) = the optimal refrigerant amount G opt,heat (1.18) holds true, and the cycle efficiency does not decrease.

[0057] G rcv =V rcv ·ρ cnd (4)

[0058] G=G chg -Grcv (5)

[0059] Under the refrigeration rated conditions, the liquid receiver is filled with low-pressure refrigerant gas, and the amount of refrigerant in the liquid receiver is G rcv = 0kg, the circulating refrigerant quantity is G = 1.78kg according to formula 5. Therefore, the circulating refrigerant quantity G (1.78) = the optimal refrigerant quantity G opt,cool (1.78) holds true, and the cycle efficiency does not decrease.

[0060] However, in actual use, the optimal amount of refrigerant changes according to various operating conditions, while the volume of the liquid storage tank is fixed. Due to different operating conditions, there will be problems such as excessive or insufficient circulating refrigerant, and reduced circulation efficiency. The following is an example:

[0061] In the heating mode with high temperature of heat source fluid, the temperature of heat source fluid is 20.0℃, the outlet temperature of load fluid is 45.0℃, the condensation temperature is 50.0℃, the evaporation temperature is 13.0℃, and the high pressure liquid density is ρ cnd,heat =0.908kg / L, low pressure liquid density is ρ evp,heat =1.12kg / L, the optimal refrigerant quantity is obtained according to formula 1: G opt,heat = 1.22kg. At this time, the liquid reservoir is filled with high-pressure refrigerant liquid, and the amount of refrigerant stored in the liquid reservoir is G according to formula 4. rcv = 0.01kg, the refrigerant circulation mass is G = 1.18kg according to formula 5. Therefore, the circulating refrigerant amount G (1.18) < the optimal refrigerant amount G opt,heat (1.22), resulting in a problem of reduced circulation efficiency due to insufficient circulating refrigerant.

[0062] In the refrigeration mode with low temperature of heat source fluid, the temperature of heat source fluid is 25.0℃, the temperature of load fluid is 7.0℃, the condensation temperature is 35.0℃, the evaporation temperature is 3.0℃, and the high pressure liquid density is ρ cnd,cool =1.01kg / L, low pressure liquid density is ρ evp,cool =1.1kg / L, the optimal refrigerant quantity is G according to formula 2 opt,cool = 1.9kg. At this time, the liquid storage tank is filled with low-pressure refrigerant gas, and the amount of refrigerant stored in the liquid storage tank is G rcv = 0kg, and the refrigerant circulation mass is G = 1.78kg according to formula 5. Therefore, the circulating refrigerant volume G (1.78) > the optimal refrigerant volume G opt,cool (1.9), resulting in the problem of reduced circulation efficiency due to excessive circulating refrigerant.

[0063] Please refer to Figure 2The present invention provides a heat pump device 100 including a compressor 1, a compressor 1, a first heat exchanger 3, a second heat exchanger 4, a throttling element 5 and a liquid storage tank 6; the inlet and outlet of the compressor 1 are respectively connected to the first interface and the second interface of the four-way valve 2, the first heat exchanger 3, the throttling element 5 and the second heat exchanger 4 are connected in sequence through pipelines, and the first heat exchanger 3 is also connected to the third interface of the four-way valve 2, and the second heat exchanger 4 is also connected to the fourth interface of the four-way valve 2 to form a refrigerant circulation flow path. The second heat exchanger 4 is used to exchange heat with the heat source fluid. When the heat pump device 100 is in the cooling mode, the refrigerant is compressed by the compressor 1 and then flows into the first heat exchanger 3 through the four-way valve 2, flows into the second heat exchanger 4 after throttling by the throttling element 5, and then flows back to the suction port of the compressor 1 through the four-way valve 2. When the heat pump device 100 is in heating mode, the refrigerant is compressed by the compressor 1 and then flows into the second heat exchanger 4 through the four-way valve 2, and then flows into the first heat exchanger 3 after being throttled by the throttling element 5, and then flows back to the suction port of the compressor 1 through the four-way valve 2. The inlet of the accumulator 6 is connected to the pipeline between the second heat exchanger 4 and the throttling element 5 through the first pipeline 7, and the first pipeline 7 is provided with a first control valve 8. The inlet of the accumulator 6 is connected to the pipeline between the first heat exchanger 3 and the throttling element 5 through the second pipeline 9, and the second pipeline 9 is provided with a second control valve 10.

[0064] The heat pump device 100 provided in this embodiment, under cooling or heating conditions, because one side of the throttling element 5 is the high-pressure side and the other side is the low-pressure side, and the first pipe 7 and the second pipe 9 are both connected to the inlet of the liquid reservoir 6, and are respectively connected to the two sides of the throttling element 5, and the first control valve 8 and the second control valve 10 are correspondingly arranged, so that when the amount of refrigerant is insufficient, the control valve on the high-pressure side of the throttling element 5 can be closed, and the control valve on the low-pressure side can be opened, so that the refrigerant in the liquid reservoir 6 can flow into the circulation pipeline. When the amount of refrigerant is excessive, the control valve on the high-pressure side of the throttling element 5 can be opened, and the control valve on the low-pressure side can be closed, so that the refrigerant can flow into the liquid reservoir 6. Thereby, insufficient or excessive circulating refrigerant can be avoided to affect the circulation heat exchange efficiency of the heat pump.

[0065] Please refer to Figure 2 In this embodiment, the air inlet of the compressor 1 is connected to the first interface of the four-way valve 2 through the first pipeline 11, the exhaust port of the compressor 1 is connected to the second interface of the four-way valve 2 through the second pipeline 13, the third interface of the four-way valve 2 is connected to the one side inlet of the first heat exchanger 3 through the third pipeline 14, the other side inlet of the first heat exchanger 3 is connected to the one side inlet of the throttling element 5 through the fourth pipeline 15, the other side of the throttling element 5 is connected to the one side inlet of the second heat exchanger 4 through the fifth pipeline 16, and the other side inlet of the second heat exchanger 4 is connected to the fourth interface of the four-way valve 2 through the sixth pipeline 17. One end of the first pipeline 7 is connected to the fifth pipeline 16, and one end of the second pipeline 9 is connected to the fourth pipeline 15.

[0066] In this embodiment, the throttling element 5 is an electronic expansion valve. Of course, in other embodiments of the present application, the throttling element 5 may also be a capillary tube or the like.

[0067] In this embodiment, the outlet of the liquid storage tank 6 is connected to the pipeline connecting the second heat exchanger 4 and the four-way valve 2 through the third pipeline 18 .

[0068] In this embodiment, the third pipeline 18 is provided so as to release the pressure when the liquid reservoir 6 exceeds the allowable pressure, thereby avoiding damage to the liquid reservoir 6 .

[0069] In this embodiment, the third pipeline 18 is provided with a pressure relief valve 19 .

[0070] It should be noted that the pressure relief valve 19 is a one-way valve, which has an opening pressure. When the pressure in the liquid reservoir 6 is greater than the opening pressure, it will automatically open to achieve pressure relief.

[0071] In this embodiment, a pressure relief valve 19 is provided so that the pressure can be directly relieved according to the pressure of the liquid reservoir 6 .

[0072] Please refer to Figure 2 In this embodiment, the first control valve 8 and the second control valve 10 are both solenoid valves.

[0073] In this embodiment, the first control valve 8 and the second control valve 10 are both configured as solenoid valves for easy control.

[0074] In this embodiment, the exhaust pipe of the compressor 1 is provided with a pressure sensor 20 , the first heat exchanger 3 is provided with a first temperature sensor 21 , and the second heat exchanger 4 is provided with a second temperature sensor 22 .

[0075] In this embodiment, the pressure sensor 20, the first temperature sensor 21 and the second temperature sensor 22 are provided to facilitate calculation of the corresponding degree of supercooling.

[0076] In this embodiment, the heat pump device 100 further includes a controller for receiving information sent by the pressure sensor 20, the first temperature sensor 21 and the second temperature sensor 22, and controlling the opening and closing of the first control valve 8 and the second control valve 10 according to the information.

[0077] Generally, the controller is electrically connected to the pressure sensor 20 , the first temperature sensor 21 , the second temperature sensor 22 , the first control valve 8 , and the second control valve 10 .

[0078] This embodiment can realize automatic control according to preset adjustment components by setting the controller, which is more convenient to use. Of course, the controller is also used to execute the following control method.

[0079] Please refer to Figure 2The present invention provides an embodiment of a control method of a heat pump device 100 to control the heat pump device 100 implemented above, the method comprising:

[0080] S1, obtaining the operation mode of the heat pump device 100;

[0081] S2. When the heat pump device 100 is in a heating operation mode, the subcooling degree of the first heat exchanger 3 is obtained, and the first control valve 8 and the second control valve 10 are controlled to be opened or closed according to the subcooling degree of the first heat exchanger 3;

[0082] S3. When the heat pump device 100 is in a cooling operation mode, the subcooling degree of the second heat exchanger 4 is obtained, and the first control valve 8 and the second control valve 10 are controlled to be opened or closed according to the subcooling degree of the second heat exchanger 4.

[0083] Since the degree of subcooling can reflect whether the refrigerant in the circulation pipeline is in a state of shortage or surplus, the opening or closing of the first control valve 8 and the second control valve 10 can be controlled by the degree of subcooling to accurately determine the refrigerant circulation amount.

[0084] In this embodiment, the step of obtaining the subcooling degree of the first heat exchanger 3 includes:

[0085] The pressure at the outlet of the compressor 1 and the refrigerant temperature of the first heat exchanger 3 are obtained, and the subcooling degree of the first heat exchanger 3 is calculated according to the pressure at the outlet of the compressor 1 and the refrigerant temperature of the first heat exchanger 3 .

[0086] The step of obtaining the subcooling degree of the second heat exchanger 4 comprises:

[0087] The pressure at the outlet of the compressor 1 and the refrigerant temperature of the second heat exchanger 4 are obtained, and the subcooling degree of the second heat exchanger 4 is calculated according to the pressure at the outlet of the compressor 1 and the refrigerant temperature of the second heat exchanger 4 .

[0088] In an optional embodiment, the step of controlling the first control valve 8 and the second control valve 10 to open or close according to the subcooling degree of the first heat exchanger 3 includes:

[0089] S21, determining whether the degree of subcooling of the first heat exchanger 3 is greater than a first threshold;

[0090] S22, if the degree of subcooling of the first heat exchanger 3 is less than the first threshold, the first control valve 8 is controlled to be opened and the second control valve 10 is controlled to be closed;

[0091] S23, if the degree of subcooling of the first heat exchanger 3 is greater than the first threshold, the second control valve 10 is controlled to be opened and the first control valve 8 is controlled to be closed;

[0092] S24, if the degree of subcooling of the first heat exchanger 3 is equal to the first threshold, the second control valve 10 and the first control valve 8 are both closed.

[0093] Therefore, in the heating state, the states of the first control valve 8 and the second control valve 10 can be adjusted in real time according to the change of the supercooling degree, so that the refrigerant circulation amount is maintained in the optimal range.

[0094] In this embodiment, the step of controlling the first control valve 8 and the second control valve 10 to open or close according to the subcooling degree of the second heat exchanger 4 includes:

[0095] S31, determining whether the degree of subcooling of the second heat exchanger 4 is greater than a second threshold;

[0096] S32, if the degree of subcooling of the second heat exchanger 4 is less than the first threshold, the first control valve 8 is controlled to be closed and the second control valve 10 is controlled to be opened;

[0097] S33, if the degree of subcooling of the second heat exchanger 4 is greater than the first threshold, the second control valve 10 is controlled to be closed and the first control valve 8 is controlled to be opened;

[0098] S234: If the degree of subcooling of the second heat exchanger 4 is equal to the first threshold, the second control valve 10 and the first control valve 8 are both closed.

[0099] Therefore, in the heating state, the states of the first control valve 8 and the second control valve 10 can be adjusted in real time according to the change of the supercooling degree, so that the refrigerant circulation amount is maintained in the optimal range.

[0100] It should be noted that the first threshold value and the second threshold value can be determined according to the parameters of the compressor 1 , the degree of subcooling, the amount of refrigerant, and the like.

[0101] After test analysis:

[0102] In the embodiment of the present invention, when the parameters of the existing heat pump device 100 are the same, the refrigerant flow path volume V1 of the first heat exchanger 3 is 6.0L, the refrigerant flow path volume V2 of the second heat exchanger 4 is 1.5L, and the volume ratio η of the high-pressure refrigerant liquid in the refrigerant flow path of the condenser is cnd =0.25, the volume ratio of the low-pressure refrigerant liquid in the refrigerant flow path of the evaporator η evp =0.15, the optimal refrigerant quantity for heating rated conditions is G opt,cool =1.18kg, the optimal refrigerant quantity under refrigeration rated conditions is G opt,cool =1.78kg.

[0103] The storage volume multiplied by the margin 1.06 is V rcv =0.869L, the amount of refrigerant filled multiplied by the margin 1.08, G chg =1.93kg.

[0104] Under the rated heating condition, the first control valve 8 is first closed, the second control valve 10 is opened, and the liquid reservoir 6 is filled with high-pressure refrigerant liquid. The amount of refrigerant stored in the liquid reservoir 6 is G according to formula 4. rcv =0.788kg, the refrigerant circulation mass is G = 1.14kg according to formula 5. Therefore, the circulating refrigerant volume G (1.14) < the optimal refrigerant volume G opt,heat(1.18) , the amount of circulating refrigerant is insufficient.

[0105] Here, the degree of subcooling calculated based on the measured values ​​of the pressure sensor 20 and the first temperature sensor 21 increases when the amount of circulating refrigerant increases. When the amount of circulating refrigerant is too little, the refrigerant in the condenser will be discharged from the condenser in a saturated state before supercooling. When the amount of circulating refrigerant is too much, excess liquid refrigerant is retained in the condenser, the degree of subcooling increases abnormally, and condensation heat transfer is hindered. Therefore, the degree of subcooling is lower than the optimal value at this time. Then, when the first control valve 8 is opened and the second control valve 10 is closed, the high-pressure liquid refrigerant in the liquid reservoir 6 is supplied to the fifth pipeline 16 through the first connecting pipe, the mass of the circulating refrigerant increases, and due to the above reasons, the degree of subcooling begins to rise. If the first control valve 8 is closed when the degree of subcooling reaches the optimal value, the amount of refrigerant stored in the liquid reservoir 6 is reduced to G. rcv = 0.744kg, the refrigerant circulation mass increases to G = 1.18kg according to formula 5, and the circulating refrigerant volume G (1.18) = the optimal refrigerant volume G opt,heat (1.18) holds true, and the cycle efficiency does not decrease.

[0106] Under the refrigeration rated condition, when the first control valve 8 is opened and the second control valve 10 is closed, the liquid reservoir 6 is filled with high-pressure refrigerant. The amount of refrigerant stored in the liquid reservoir 6 is G according to formula 4. rcv = 0.820kg, the refrigerant circulation mass is G = 1.11kg according to formula 5. Therefore, the circulating refrigerant amount G (1.11) < the optimal refrigerant amount G opt,cool (1.78), the amount of circulating refrigerant is insufficient. Here, the degree of subcooling of the second heat exchanger 4, calculated based on the measured values ​​of the pressure sensor 20 and the second temperature sensor 22, increases when the amount of circulating refrigerant increases. When the amount of circulating refrigerant is too small, the refrigerant in the condenser will be discharged from the condenser in a saturated state before supercooling. The characteristic of decreasing when the amount of circulating refrigerant decreases. Therefore, the degree of subcooling is lower than the optimal value at this time. Then close the first control valve 8, open the second control valve 10, and the high-pressure liquid refrigerant in the liquid reservoir 6 is supplied to the fourth pipeline 15 through the second connecting pipe. The amount of circulating refrigerant increases, and due to the above reasons, the degree of subcooling begins to rise. If the second control valve 10 is closed when the degree of subcooling reaches the optimal value, the amount of refrigerant stored in the liquid reservoir 6 is reduced to G rcv = 0.143kg, the refrigerant circulation mass increases to G = 1.78kg according to formula 5, and the circulating refrigerant amount G (1.78) = the optimal refrigerant amount G opt,heat(1.78) holds true, and the cycle efficiency does not decrease.

[0107] In the heating mode with high temperature of heat source fluid under the same conditions as the existing heat pump, the optimal refrigerant amount is G opt,heat =1.22kg. First, close the first control valve 8, open the second control valve 10, and fill the liquid reservoir 6 with high-pressure refrigerant liquid. The amount of refrigerant stored in the liquid reservoir 6 is G according to formula 4. rcv = 0.788kg, the mass of circulating refrigerant is = 1.14kg according to formula 5. Therefore, the circulating refrigerant amount G(1.14) < the optimal refrigerant amount G opt,heat (1.22), the amount of circulating refrigerant is insufficient. Due to the above reasons, the degree of subcooling is lower than the optimal value at this time. Then, when the first control valve 8 is opened and the second control valve 10 is closed, the high-pressure liquid refrigerant in the liquid storage tank 6 is supplied to the refrigerant pipe through the connecting pipe A, the amount of circulating refrigerant increases, and due to the above reasons, the degree of subcooling begins to rise. If the electromagnetic A is closed when the degree of subcooling reaches the optimal value, the amount of refrigerant stored in the liquid storage tank 6 is reduced to G rcv = 0.706kg, the refrigerant circulation mass increases to G = 1.22kg according to formula 5, and the circulating refrigerant volume G (1.22) = the optimal refrigerant volume G opt,heat (1.22) holds true, and the cycle efficiency does not decrease.

[0108] In the refrigeration mode with low temperature heat source fluid under the same conditions as the existing heat pump, the optimal refrigerant amount is G opt,heat =1.69kg. First, open the first control valve 8 and close the second control valve 10. The liquid reservoir 6 is filled with high-pressure refrigerant liquid. The amount of refrigerant stored in the liquid reservoir 6 is G according to formula 4. rcv = 0.874kg, the refrigerant circulation mass is G = 1.05kg according to formula 5. Therefore, the circulating refrigerant amount G (0.874) < the optimal refrigerant amount G opt,heat (1.69), the amount of circulating refrigerant is insufficient. Due to the above reasons, the degree of subcooling is lower than the optimal value at this time. Then close the first control valve 8, open the second control valve 10, and the high-pressure liquid refrigerant in the liquid storage tank 6 is supplied to the refrigerant pipe through the connecting pipe B, the amount of circulating refrigerant increases, and due to the above reasons, the degree of subcooling begins to rise. If the electromagnetic B is closed when the degree of subcooling reaches the optimal value, the amount of refrigerant stored in the liquid storage tank 6 is reduced to G rcv = 0.241kg, the refrigerant circulation mass increases to G = 1.69kg according to formula 5, and the circulating refrigerant volume G (1.69) = the optimal refrigerant volume G opt,heat (1.69) holds true, and the cycle efficiency does not decrease.

[0109] In summary, the working principle and beneficial effects of the heat pump device 100 and the control method thereof provided in this embodiment include:

[0110] In the heat pump device 100 of this embodiment, under cooling or heating conditions, one side of the throttling element 5 is the high-pressure side and the other side is the low-pressure side, and the first pipe 7 and the second pipe 9 are both connected to the inlet of the liquid reservoir 6, and are respectively connected to the two sides of the throttling element 5, and the first control valve 8 and the second control valve 10 are correspondingly arranged, so that when the amount of refrigerant is insufficient, the control valve on the high-pressure side of the throttling element 5 can be closed, and the control valve on the low-pressure side can be opened, so that the refrigerant in the liquid reservoir 6 can flow into the circulation pipeline. When the amount of refrigerant is excessive, the control valve on the high-pressure side of the throttling element 5 can be opened, and the control valve on the low-pressure side can be closed, so that the refrigerant can flow into the liquid reservoir 6. Thereby, insufficient or excessive circulating refrigerant can be avoided to affect the circulation heat exchange efficiency of the heat pump.

[0111] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A heat pump device, characterized in that: It comprises a compressor (1), a four-way valve (2), a first heat exchanger (3), a second heat exchanger (4), a throttling element (5) and a liquid storage device (6); The inlet and outlet of the compressor (1) are respectively connected to the first interface and the second interface of the four-way valve (2); the first heat exchanger (3), the throttling element (5) and the second heat exchanger (4) are connected in sequence through pipelines; the first heat exchanger (3) is also connected to the third interface of the four-way valve (2); the second heat exchanger (4) is also connected to the fourth interface of the four-way valve (2), so as to form a refrigerant circulation flow path; The inlet of the liquid reservoir (6) is connected to the pipeline between the second heat exchanger (4) and the throttling element (5) through a first pipeline (7), and the first pipeline (7) is provided with a first control valve (8); the inlet of the liquid reservoir (6) is connected to the pipeline between the first heat exchanger (3) and the throttling element (5) through a second pipeline (9), and the second pipeline (9) is provided with a second control valve (10).

2. The heat pump device according to claim 1, characterized in that: The outlet of the liquid storage device (6) is connected to the pipeline connecting the second heat exchanger (4) and the four-way valve (2) through a third pipeline (18).

3. The heat pump device according to claim 2, characterized in that: The third pipeline (18) is provided with a pressure relief valve (19).

4. The heat pump device according to claim 1, characterized in that: The first control valve (8) and the second control valve (10) are both solenoid valves.

5. The heat pump device according to claim 1, characterized in that: The exhaust pipe of the compressor (1) is provided with a pressure sensor (20), the first heat exchanger (3) is provided with a first temperature sensor (21), and the second heat exchanger (4) is provided with a second temperature sensor (22).

6. The heat pump device according to claim 5, characterized in that: The heat pump device also includes a controller, which is used to receive information sent by the pressure sensor (20), the first temperature sensor (21) and the second temperature sensor (22), and control the opening and closing of the first control valve (8) and the second control valve (10) according to the information.

7. A method for controlling a heat pump device, for controlling the heat pump device according to any one of claims 1 to 6, characterized in that: The method comprises: Obtaining an operating mode of a heat pump device; When the heat pump device is in a heating operation mode, the subcooling degree of the first heat exchanger (3) is obtained, and the first control valve (8) and the second control valve (10) are controlled to be opened or closed according to the subcooling degree of the first heat exchanger (3); When the heat pump device is in a cooling operation mode, the degree of subcooling of the second heat exchanger (4) is obtained, and the first control valve (8) and the second control valve (10) are controlled to be opened or closed according to the degree of subcooling of the second heat exchanger (4).

8. The control method of the heat pump device according to claim 7, characterized in that: The step of obtaining the subcooling degree of the first heat exchanger (3) comprises: Obtaining the pressure at the outlet of the compressor (1) and the refrigerant temperature of the first heat exchanger (3), and calculating the degree of subcooling of the first heat exchanger (3) based on the pressure at the outlet of the compressor (1) and the refrigerant temperature of the first heat exchanger (3); The step of obtaining the subcooling degree of the second heat exchanger (4) comprises: The pressure at the outlet of the compressor (1) and the refrigerant temperature of the second heat exchanger (4) are obtained, and the degree of subcooling of the second heat exchanger (4) is calculated based on the pressure at the outlet of the compressor (1) and the refrigerant temperature of the second heat exchanger (4).

9. The control method of the heat pump device according to claim 7, characterized in that: The step of controlling the first control valve (8) and the second control valve (10) to open or close according to the subcooling degree of the first heat exchanger (3) comprises: Determining whether the degree of subcooling of the first heat exchanger (3) is greater than a first threshold; If the degree of subcooling of the first heat exchanger (3) is less than a first threshold value, the first control valve (8) is controlled to be opened and the second control valve (10) is controlled to be closed; If the degree of subcooling of the first heat exchanger (3) is greater than a first threshold value, the second control valve (10) is controlled to open and the first control valve (8) is controlled to close; If the degree of subcooling of the first heat exchanger (3) is equal to a first threshold value, the second control valve (10) and the first control valve (8) are both controlled to be closed.

10. The control method of the heat pump device according to claim 7, characterized in that: The step of controlling the first control valve (8) and the second control valve (10) to open or close according to the subcooling degree of the second heat exchanger (4) comprises: determining whether the degree of subcooling of the second heat exchanger (4) is greater than a second threshold; If the degree of subcooling of the second heat exchanger (4) is less than a first threshold value, the first control valve (8) is controlled to be closed and the second control valve (10) is controlled to be opened; If the degree of subcooling of the second heat exchanger (4) is greater than a first threshold value, the second control valve (10) is controlled to be closed and the first control valve (8) is controlled to be opened; If the degree of subcooling of the second heat exchanger (4) is equal to a first threshold value, the second control valve (10) and the first control valve (8) are both controlled to be closed.

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