A heat pump system and its defrosting control method

Abstract

A heat pump system and its defrosting control method. The heat pump system includes a compressor, a four-way reversing valve, an outdoor heat exchanger, a throttle valve, an indoor heat exchanger, a liquid receiver, a temperature sensor, a liquid level sensor, and a control module. During the reverse-cycle defrosting process of the heat pump system, there will be a liquid hammer phenomenon, which will increase the system noise and reduce the reliability of the compressor. The present invention proposes a defrosting control method that dynamically couples the operating frequency of the compressor and the opening of the throttle valve according to the defrosting condition on the surface of the outdoor heat exchanger and the liquid level height of the liquid receiver, improving the defrosting efficiency and preventing the occurrence of liquid hammer in the compressor, and enhancing the reliability of the compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and in particular to a heat pump system and a defrosting control method therefor. Background Art

[0002] When a heat pump system operates for heating in winter, frosting may occur on the surface of the heat exchanger. The frost blocks the air flow passage, increases the pressure drop on the air side, and increases the thermal resistance on the surface of the heat exchanger. Defrosting the heat pump system is a key method to ensure the stable and efficient operation of the heat pump. Currently, the defrosting methods for heat pumps generally include mechanical defrosting and thermal defrosting. Among current heat pump products, reverse cycle defrosting has been widely used due to its advantages such as high efficiency, safety, and convenience.

[0003] The reverse cycle defrosting process is realized by a four-way reversing valve. The system structure is relatively simple. The high-temperature exhaust gas of the compressor directly enters the outdoor heat exchanger for defrosting. And to prevent cold air from being blown, the indoor fan is generally turned off. Since the indoor fan is off, the indoor heat exchanger can only exchange heat through convection. The outlet of the indoor heat exchanger is generally two-phase refrigerant. Therefore, the liquid refrigerant entering the accumulator will gradually increase until liquid slugging of the compressor occurs. Liquid slugging of the compressor will generate a large noise and pose a greater challenge to the reliability of the compressor. Preventing liquid slugging during the defrosting process and ensuring efficient defrosting of the heat pump system are very important. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned heat pump system, the purpose of the present invention is to provide a heat pump system and a defrosting control method therefor. By real-time monitoring of the surface temperature of the outdoor heat exchanger 03, the defrosting situation on the surface of the outdoor heat exchanger 03 is obtained, and the liquid level height of the accumulator 07 is also real-time monitored to prevent liquid slugging of the compressor 01. By using the surface temperature of the outdoor heat exchanger 03 and the liquid level height of the accumulator 07 as logical control criteria, the operating frequency of the compressor 01 and the opening degree of the throttle valve 05 are dynamically coupled and adjusted, so as to improve the defrosting efficiency of the heat pump system and prevent liquid slugging during the defrosting process.

[0005] To achieve the above technical purpose, the present invention adopts the following technical solutions:

[0006] A heat pump system includes a compressor 01, a four-way reversing valve 02, an outdoor heat exchanger 03, a temperature sensor 04, a throttle valve 05, an indoor heat exchanger 06, a liquid receiver 07, a liquid level sensor 08, and a control module C1. The compressor discharge port 100 is connected to the first port 21 of the four-way reversing valve. The compressor suction port 101 is connected to the outlet 72 of the liquid receiver. The third port 23 of the four-way reversing valve is connected to the inlet 71 of the liquid receiver. The fourth port 24 of the four-way reversing valve is connected to the indoor heat exchanger 06. The second port 22 of the four-way reversing valve is connected to the outdoor heat exchanger 03. The outdoor heat exchanger 03 and the indoor heat exchanger (06) are connected through the throttle valve 05. The temperature sensor 04 is installed at the middle position of the outdoor heat exchanger 03. The liquid level sensor 08 is installed inside the liquid receiver 07 for measuring the liquid level height in the liquid receiver 07. The control module C1 is connected to the temperature sensor 04, the throttle valve 05, the liquid level sensor 08, and the compressor 01, and is used to collect the signals of the temperature sensor 04 and the liquid level sensor 08, and control the opening of the throttle valve 05 and the operating frequency of the compressor 01.

[0007] For the defrost control method of the described heat pump system, the temperature sensor 04 and the liquid level sensor 08 output signals to the control module C1. The control module C1 controls the opening of the throttle valve 05 and adjusts the frequency of the compressor 01 according to the pre-written control logic. During the defrosting process of the heat pump system, there will be a phenomenon of liquid slugging in the compressor 01 in the middle and late stages of defrosting. The liquid slugging phenomenon will seriously affect the reliability of the compressor 01. Therefore, during the defrosting process, it is necessary to monitor and control the liquid level of the liquid receiver 07 to prevent the occurrence of liquid slugging. By dynamically coupling and adjusting the throttle valve 05 and the compressor 01, the defrosting efficiency of the heat pump system can be improved, and the occurrence of liquid slugging during the defrosting process can be prevented. Let k1 represent the temperature value measured by the temperature sensor 04, and let l1 represent the liquid level height measured by the liquid level sensor 08. The specific control is as follows:

[0008] In the initial stage of defrosting, the compressor 01 operates at full load with a frequency of f1, and the opening of the throttle valve 05 is n1. The control module C1 monitors the changes in temperature and liquid level once every preset time. As defrosting progresses, when the temperature k1 < k n1 , and the liquid level l1 < l n1 , the opening of the throttle valve 05 and the operating frequency of the compressor 01 are maintained at f1. When the temperature k1 < k n1 , and the liquid level l n2 ≥ l1 ≥ l n1 , the operating frequency of the compressor 01 remains unchanged, and the opening of the throttle valve 05 is reduced to n2. When the temperature k1 ≥ k n1 , and the liquid level l1 ≤ l n2 , the operating frequency of the compressor 01 is reduced to f2, and the opening of the throttle valve 05 is maintained at n2. When the temperature k1 ≥ k n1 , and the liquid level l1 > ln2 When the temperature is k1, the operating frequency of the compressor 01 drops to f3, and the opening degree of the throttle valve 05 drops to n3; when the temperature k1 ≥ k n2 the heat pump system exits the defrosting mode;

[0009] The k n1 and k n2 and l n2 The value ranges of n1, n2, n3, f1, f2, and f3 are as shown in the following table:

[0010]

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1. The present invention provides a heat pump system and its defrosting control method, which can dynamically couple and control the compressor frequency and the throttle valve opening according to the defrosting condition on the surface of the outdoor heat exchanger and the liquid level height of the accumulator, thereby improving the defrosting efficiency.

[0013] 2. The present invention provides a heat pump system and its defrosting control method, which can dynamically couple and control the compressor frequency and the throttle valve opening according to the defrosting condition on the surface of the outdoor heat exchanger and the liquid level height of the accumulator, preventing the liquid hammer phenomenon of the compressor, reducing the system noise, and improving the reliability of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the refrigerant flow under the defrosting condition of the heat pump system described in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0016] As Figure 1As described above, a heat pump system includes a compressor 01, a four-way reversing valve 02, an outdoor heat exchanger 03, a temperature sensor 04, a throttle valve 05, an indoor heat exchanger 06, a liquid receiver 07, a liquid level sensor 08, and a control module C1. The exhaust port 100 of the compressor is connected to the first port 21 of the four-way reversing valve. The suction port 101 of the compressor is connected to the outlet 72 of the liquid receiver. The third port 23 of the four-way reversing valve is connected to the inlet 71 of the liquid receiver. The fourth port 24 of the four-way reversing valve is connected to the indoor heat exchanger 06. The second port 22 of the four-way reversing valve is connected to the outdoor heat exchanger 03. The outdoor heat exchanger 03 is further connected to the throttle valve 05, and the throttle valve 05 is further connected to the indoor heat exchanger 06. The temperature sensor 04 is installed at the middle position of the outdoor heat exchanger 03. The liquid level sensor 08 is installed inside the liquid receiver 07 for measuring the liquid level height in the liquid receiver 07. The control module C1 is connected to the temperature sensor 04, the throttle valve 05, the liquid level sensor 08, and the compressor 01, and is used to collect the signals of the temperature sensor 04 and the liquid level sensor 08, and control the opening degree of the throttle valve 05 and the operating frequency of the compressor 01.

[0017] The working process of the air conditioning system described in the present invention is as follows: As Figure 1 shown, the high-temperature and high-pressure gas coming out of the compressor 01 first enters the four-way reversing valve 02 and then enters the outdoor heat exchanger 03 for defrosting. The refrigerant coming out of the outdoor heat exchanger is throttled into a low-temperature and low-pressure refrigerant after passing through the throttle valve 05, and then enters the indoor heat exchanger 06 to evaporate and absorb heat. The refrigerant coming out of the indoor heat exchanger 06 enters the liquid receiver 07 after passing through the four-way reversing valve 02, and finally enters the compressor 01 for compression.

[0018] For the defrosting control method of the heat pump system described in the present invention, the temperature sensor 04 and the liquid level sensor 08 output signals to the control module C1. The control module C1 controls the opening degree of the throttle valve 05 and adjusts the frequency of the compressor 01 according to the pre-written control logic. During the defrosting process of the heat pump system, there will be a phenomenon of liquid slugging in the compressor 01 in the middle and late stages of defrosting. The liquid slugging phenomenon will seriously affect the reliability of the compressor 01. Therefore, during the defrosting process, it is necessary to monitor and control the liquid level of the liquid receiver 07 to prevent the occurrence of the liquid slugging phenomenon. By dynamically coupling and adjusting the throttle valve 05 and the compressor 01, the defrosting efficiency of the heat pump system can be improved, and the liquid slugging phenomenon during the defrosting process can be prevented. Let k1 represent the temperature value measured by the temperature sensor 04, and let l1 represent the liquid level height measured by the liquid level sensor 08. The specific control is as follows:

[0019] In the initial stage of defrosting, the compressor 01 operates at full load with a frequency of f1, and the opening degree of the throttle valve 05 is n1. The control module C1 monitors the changes in temperature and liquid level every 5 s. As the defrosting progresses, when the temperature k1 < k n1 , and the liquid level l1 < l n1When the temperature is k1 < k, keep the opening degree of the throttle valve 05 and the operating frequency of the compressor 01 at f1; when the temperature k1 < k n1 , and the liquid level l n2 ≥ l1 ≥ l n1 When this is the case, the operating frequency of the compressor 01 remains unchanged, and the opening degree of the throttle valve 05 is reduced to n2; when the temperature k1 ≥ k n1 , and the liquid level l1 ≤ l n2 When this is the case, the operating frequency of the compressor 01 is reduced to f2, and the opening degree of the throttle valve 05 remains at n2; when the temperature k1 ≥ k n1 , and the liquid level l1 > l n2 When this is the case, the operating frequency of the compressor 01 is reduced to f3, and the opening degree of the throttle valve 05 is reduced to n3; when the temperature k1 ≥ k n2 When this is the case, the heat pump system exits the defrosting mode;

[0020] The values of the said k n1 、k n2 、 l n2 、n1, n2, n3, f1, f2, f3 are as shown in the following table:

[0021]

[0022]

Claims

1. A defrosting control method for a heat pump system, characterized in that: The heat pump system includes a compressor (01), a four-way reversing valve (02), an outdoor heat exchanger (03), a temperature sensor (04), a throttle valve (05), an indoor heat exchanger (06), a liquid receiver (07), a liquid level sensor (08) and a control module (C1). The exhaust port (100) of the compressor is connected to the first port (21) of the four-way reversing valve. The suction port (101) of the compressor is connected to the outlet (72) of the liquid receiver. The third port (23) of the four-way reversing valve is connected to the inlet (71) of the liquid receiver. The fourth port (24) of the four-way reversing valve is connected to the indoor heat exchanger (06). The second port (22) of the four-way reversing valve is connected to the outdoor heat exchanger (03). The outdoor heat exchanger (03) and the indoor heat exchanger (06) are connected through the throttle valve (05). The temperature sensor (04) is installed at the middle position of the outdoor heat exchanger (03). The liquid level sensor (08) is installed inside the liquid receiver (07) for measuring the liquid level height in the liquid receiver (07). The control module (C1) is connected to the temperature sensor (04), the throttle valve (05), the liquid level sensor (08) and the compressor (01) for collecting the signals of the temperature sensor (04) and the liquid level sensor (08) and controlling the opening degree of the throttle valve (05) and the operating frequency of the compressor (01). The defrosting control method is as follows: The temperature sensor (04) and the liquid level sensor (08) output signals to the control module (C1), and the control module (C1) controls the opening degree of the throttle valve (05) and adjusts the frequency of the compressor (01). During the defrosting process of the heat pump system, there will be a phenomenon of liquid slugging in the compressor (01) in the middle and late stages of defrosting. The liquid slugging phenomenon will seriously affect the reliability of the compressor (01). Therefore, during the defrosting process, it is necessary to monitor and control the liquid level of the liquid receiver (07) to prevent the occurrence of liquid slugging. By dynamically coupling and adjusting the throttle valve (05) and the compressor (01), the defrosting efficiency of the heat pump system can be improved, and the liquid slugging phenomenon during defrosting can be prevented. Let k1 represent the temperature value measured by the temperature sensor (04), and let l1 represent the liquid level height measured by the liquid level sensor (08). The specific control is as follows: In the initial stage of defrosting, the compressor (01) operates at full load with a frequency of f1, the opening degree of the throttle valve (05) is n1, and the control module (C1) monitors the changes in temperature and liquid level once every preset time. As defrosting progresses, when the temperature k1 < k n1 , and the liquid level l1 < l n1 , the opening degree of the throttle valve (05) and the operating frequency of the compressor (01) are maintained at f1; when the temperature k1 < k n1 , and the liquid level l n2 ≥l1≥l n1 , the operating frequency of the compressor (01) remains unchanged, and the opening degree of the throttle valve (05) is reduced to n2; when the temperature k1≥k n1 , and the liquid level l1≤l n2 , the operating frequency of the compressor (01) is reduced to f2, and the opening degree of the throttle valve (05) is maintained at n2; when the temperature k1≥k n1 , and the liquid level l1 > l n2 , the operating frequency of the compressor (01) is reduced to f3, and the opening degree of the throttle valve (05) is reduced to n3; when the temperature k1≥k n2 , the heat pump system exits the defrosting mode; The said k n1 and k n2 , l n2 , n1, n2, n3, f1, f2, f3 have value ranges as shown in the following table:

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