A control method for an electronic expansion valve of a heat pump

Abstract

A control method of an electronic expansion valve of a heat pump, when operating, comprises the following steps: step one, the heat pump is powered on, and enters step two; step two, normal operation, and enters step three; step three, a central controller of the heat pump judges whether Td-Tm<=K is established, when it is established, enters step four, otherwise enters step ten, wherein, Td is a current actual superheat, Tm is a target superheat, the value range of Tm is 0-10 DEG C, K is a set difference value, the value range of K is 0-20 DEG C; step four, the central controller calculates and obtains a current actual subcooling Tr. According to the relationship of the current actual superheat Td, the current actual subcooling Tr and the like, the target superheat is corrected, the control accuracy of the electronic expansion valve is improved, the function of the condenser is fully played, the heat pump can keep better heating performance or refrigeration performance, and the reliability of the heat pump operation is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a heat pump, in particular to a control method of an electronic expansion valve of a heat pump. BACKGROUND

[0002] The control of the electronic expansion valve is one of the more important cores in the whole heat pump, in the control method of the existing common electronic expansion valve, the control is mainly carried out according to the back gas superheat or the exhaust gas superheat, but due to the detection error of the temperature sensor or the pressure sensor of the heat pump, or the unreasonable setting of the superheat target value, the step number of the electronic expansion valve may be large or small, which leads to the phenomenon that the superheat of the heat pump is satisfied, but the condensing temperature in the machine system is high and the supercooling degree is large due to the sensor accuracy error, the power consumption of the machine is large, and the energy efficiency of the machine is reduced;Or, the current heat pump supercooling degree is small, and the heat pump does not fully play the role of the condenser, resulting in low working capacity and energy efficiency of the heat pump. And when the control of the electronic expansion valve is not accurate enough, the heating performance of the heat pump will be reduced, which leads to the decline of customer experience.

[0003] Chinese patent document No. CN 109059369 A disclosed a control method of an electronic expansion valve on October 01, 2008, the electronic expansion valve is arranged in the refrigerant circulation loop of the equipment, and the evaporator is also arranged in the circulation loop, characterized in that the control method comprises the following steps: S10: starting the electronic expansion valve and initializing, setting the opening degree of the electronic expansion valve at a predetermined initial value;S20: after starting for a predetermined time, the actual superheat / overcooling of the electronic expansion valve is determined according to the difference between the outlet temperature and the inlet temperature of the evaporator;S30: compare the actual superheat / overcooling with the target superheat / overcooling, and determine the optimal opening degree value range of the electronic expansion valve;S40: adjust the opening degree of the electronic expansion valve to the optimal opening degree value range. The control method of the electronic expansion valve is not ideal after practical test, and needs to be improved. SUMMARY

[0004] The purpose of the present application is to provide a control method of an electronic expansion valve of a heat pump with good performance, so as to overcome the shortcomings in the prior art.

[0005] A control method of an electronic expansion valve of a heat pump designed for the purpose, characterized in that the high-pressure outlet of the compressor of the heat pump is connected with the D interface of an electromagnetic four-way reversing valve, the C interface of the electromagnetic four-way reversing valve is connected with one end of an evaporator, the other end of the evaporator is connected with the refrigerant side of a plate heat exchanger through an electronic expansion valve, the other side of the refrigerant of the plate heat exchanger is connected with the E interface of the electromagnetic four-way reversing valve, the S interface of the electromagnetic four-way reversing valve is connected with the low-pressure inlet of the compressor, the other end of the evaporator is provided with an external coil temperature sensor, the pipeline between the S interface of the electromagnetic four-way reversing valve and the low-pressure inlet of the compressor is respectively provided with a return gas temperature sensor and a low-pressure pressure sensor, the pipeline between the D interface of the electromagnetic four-way reversing valve and the high-pressure outlet of the compressor is respectively provided with a high-pressure pressure sensor and an exhaust temperature sensor, and the pipeline between the electronic expansion valve and the refrigerant side of the plate heat exchanger is provided with an internal coil temperature sensor, and the operation includes the following steps:

[0006] Step one, the heat pump is powered on, and step two is entered;

[0007] Step two, normal operation, step three is entered;

[0008] Step three, the central controller of the heat pump judges whether Td-Tm≤K is established, when it is established, step four is entered, otherwise step ten is entered, wherein Td is the current actual return gas superheat degree, Tm is the target return gas superheat degree, the value range of Tm is 0-10℃, and K is a set difference value, the value range of K is 0-20℃;

[0009] Step four, the central controller calculates and obtains the current actual subcooling degree Tr, and step five is entered;

[0010] Wherein, when the heat pump is refrigerating, Tr=T2-T3; when the heat pump is heating, Tr=T2-T6;

[0011] T2 is the condensation temperature converted by high-pressure pressure, T3 is the internal coil temperature, and T6 is the external coil temperature;

[0012] Step five, the central controller judges whether Tr≤Y is established, when it is established, step two is entered, otherwise step six is entered, wherein Y is a set threshold value, and the value range of Y is 0-20℃;

[0013] Step six, the central controller judges whether Tr≥N1 is established, when it is established, step twelve is entered, otherwise step seven is entered, wherein N1 is a first set subcooling degree, and the value range of N1 is 16-19℃;

[0014] Step seven, the central controller judges whether N2≤Tr<N1 is established, when it is established, enters step thirteen, otherwise enters step eight, wherein, N2 is second set supercooling degree, the value range of N2 is 12℃-15℃;

[0015] Step eight, the central controller judges whether N3≤Tr<N2 is established, when it is established, enters step fourteen, otherwise enters step nine, wherein, N3 is third set supercooling degree, the value range of N3 is 5℃-11℃;

[0016] Step nine, the central controller judges whether N4≤Tr<N3 is established, when it is established, enters step fifteen, otherwise enters step ten, wherein, N4 is fourth set supercooling degree, the value range of N4 is 0℃-4℃;

[0017] Step ten, Tm=Tm+K5, enters step two, wherein, K5 is fifth correction value, the value range of K5 is 0.9℃-1.8℃;

[0018] Step eleven, continues to adjust, enters step three;

[0019] Step twelve, Tm=Tm+K1, enters step two, K1 is first correction value, the value range of K1 is -1.9℃--1.2℃;

[0020] Step thirteen, Tm=Tm+K2, enters step two, K2 is second correction value, the value range of K2 is -1.3℃--0.9℃;

[0021] Step fourteen, Tm=Tm+K3, enters step two, K3 is third correction value, the value range of K3 is -0.8℃--0.2℃;

[0022] Step fifteen, Tm=Tm+K4, enters step two, K4 is fourth correction value, the value range of K4 is -0.1℃-0.8℃.

[0023] The application corrects target return gas superheat degree according to the relationship of current actual return gas superheat degree Td, current actual supercooling degree Tr and the like, improves the control accuracy of electronic expansion valve, fully plays the role of condenser, makes the heat pump can keep better heating performance or refrigerating performance, and improves the reliability of heat pump operation.

[0024] In summary, the application has the characteristics of good performance and stable and reliable operation. BRIEF DESCRIPTION OF DRAWINGS

[0025] Fig. 1 It is structural schematic view of an embodiment of the application.

[0026] Fig. 2 It is control flow chart of the application.

[0027] Figure: 1 is an electromagnetic four-way reversing valve, 2 is a return gas temperature sensor, 3 is a high pressure sensor, 4 is a low pressure sensor, 5 is an exhaust gas temperature sensor, 6 is an evaporator, 7 is an external coil temperature sensor, 8 is an electronic expansion valve, 9 is a compressor, 10 is an internal coil temperature sensor, 11 is a plate heat exchanger, DETAILED DESCRIPTION

[0028] The application will be further described below in conjunction with the drawings and examples.

[0029] Reference Figs. 1-2 A control method of an electronic expansion valve of a heat pump, the high pressure outlet of the compressor 9 of the heat pump is connected with the D interface of the electromagnetic four-way reversing valve 1, the C interface of the electromagnetic four-way reversing valve 1 is connected with one end of the evaporator 6, the other end of the evaporator 6 is connected with the refrigerant side of the plate heat exchanger 11 through the electronic expansion valve 8, the other side of the refrigerant of the plate heat exchanger 11 is connected with the E interface of the electromagnetic four-way reversing valve 1, the S interface of the electromagnetic four-way reversing valve 1 is connected with the low pressure inlet of the compressor 9, the other end of the evaporator 6 is provided with the external coil temperature sensor 7, the return gas temperature sensor 2 and the low pressure sensor 4 are respectively arranged on the pipeline between the S interface of the electromagnetic four-way reversing valve 1 and the low pressure inlet of the compressor 9, the high pressure sensor 3 and the exhaust gas temperature sensor 5 are respectively arranged on the pipeline between the D interface of the electromagnetic four-way reversing valve 1 and the high pressure outlet of the compressor 9, and the internal coil temperature sensor 10 is arranged on the pipeline between the electronic expansion valve 8 and the refrigerant side of the plate heat exchanger 11.

[0030] In operation, the following steps are included:

[0031] Step one, the heat pump is powered on, and enters step two;

[0032] Step two, normal operation, and enters step three;

[0033] Step three, the central controller of the heat pump judges whether Td-Tm≤K is true, when it is true, enters step four, otherwise enters step ten, wherein Td is the current actual return gas superheat, Tm is the target return gas superheat, the value range of Tm is 0℃-10℃, and K is a set difference value, the value range of K is 0℃-20℃;

[0034] Step four, the central controller calculates and obtains the current actual subcooling degree Tr, and enters step five;

[0035] Wherein, when the heat pump is refrigerating, Tr=T2-T3; when the heat pump is heating, Tr=T2-T6;

[0036] T2 is the condensation temperature after high pressure pressure conversion, T3 is the internal coil temperature, and T6 is the external coil temperature;

[0037] Step five, the central controller judges whether Tr≤Y is true, when it is true, it enters step two, otherwise it enters step six, wherein Y is a set threshold, the value range of Y is 0℃-20℃;

[0038] Step six, the central controller judges whether Tr≥N1 is true, when it is true, it enters step twelve, otherwise it enters step seven, wherein N1 is a first set supercooling degree, the value range of N1 is 16℃-19℃;

[0039] Step seven, the central controller judges whether N2≤Tr<N1 is true, when it is true, it enters step thirteen, otherwise it enters step eight, wherein N2 is a second set supercooling degree, the value range of N2 is 12℃-15℃;

[0040] Step eight, the central controller judges whether N3≤Tr<N2 is true, when it is true, it enters step fourteen, otherwise it enters step nine, wherein N3 is a third set supercooling degree, the value range of N3 is 5℃-11℃;

[0041] Step nine, the central controller judges whether N4≤Tr<N3 is true, when it is true, it enters step fifteen, otherwise it enters step ten, wherein N4 is a fourth set supercooling degree, the value range of N4 is 0℃-4℃;

[0042] Step ten, Tm=Tm+K5, it enters step two, wherein K5 is a fifth correction value, the value range of K5 is 0.9℃-1.8℃;

[0043] Step eleven, it continues to adjust, and enters step three;

[0044] Step twelve, Tm=Tm+K1, it enters step two, K1 is a first correction value, the value range of K1 is -1.9℃--1.2℃;

[0045] Step thirteen, Tm=Tm+K2, it enters step two, K2 is a second correction value, the value range of K2 is -1.3℃--0.9℃;

[0046] Step fourteen, Tm=Tm+K3, it enters step two, K3 is a third correction value, the value range of K3 is -0.8℃--0.2℃;

[0047] Step fifteen, Tm=Tm+K4, it enters step two, K4 is a fourth correction value, the value range of K4 is -0.1℃-0.8℃.

[0048] Application example

[0049] Suppose the target superheat Tm of the heat pump is 3℃, the set difference K is 18℃, the set threshold Y is 2℃, the first set subcooling N1 is 18℃, the second set subcooling N2 is 13℃, the third set subcooling N3 is 8℃, the fourth set subcooling N4 is 3℃, the first correction value K1 is -1.5℃, the second correction value K2 is -1℃, the third correction value K3 is -0.5℃, the fourth correction value K4 is 0℃, and the fifth correction value K5 is 1℃.

[0050] At this time, the central controller obtains the current actual superheat Td = 20℃.

[0051] Since Td-Tm = 20℃-3℃ = 17℃≤K = 18℃, step four is entered.

[0052] Next, five cases are described in detail.

[0053] 1) The central controller calculates and obtains the current actual subcooling Tr = 19℃; since Tr = 19℃>Y = 2℃, step six is entered.

[0054] Since Tr = 19℃≥N1 = 18℃, the central controller determines that the current opening of the electronic expansion valve is too small, the current actual subcooling is too large, the condensing temperature of the heat pump is too high, and the coefficient of performance cop of the heat pump is too low.

[0055] Therefore, step twelve is entered to correct the target superheat Tm.

[0056] Tm = Tm+K1 = 3℃+(-1.5℃) = 1.5℃.

[0057] Next, the current opening of the electronic expansion valve is increased according to the corrected target superheat, and step two is entered to make the heat pump operate more in line with the design parameters.

[0058] 2) The central controller calculates and obtains the current actual subcooling Tr = 15℃; since Tr = 15℃>Y = 2℃, step six is entered.

[0059] Since step seven N2 = 13℃≤Tr = 15℃<N1 = 18℃, the central controller determines that the current opening of the electronic expansion valve is too small, the current actual subcooling is too large, the condensing temperature of the heat pump is too high, and the coefficient of performance cop of the heat pump is too low.

[0060] Therefore, step thirteen is entered to correct the target superheat Tm.

[0061] Tm = Tm+K2 = 3℃+(-1℃) = 2℃.

[0062] Next, according to the revised target superheat, the current opening of the electronic expansion valve is increased, and step two is entered, so that the heat pump is more in line with the design parameters to run.

[0063] 3) The central controller calculates and obtains the current actual subcooling Tr=9℃; Tr=9℃≤Y=2℃ is not true, so step six is entered.

[0064] Since step eight N3=8℃≤Tr=9℃<N2=13℃ is true, the central controller determines that the current opening of the electronic expansion valve is too small, the current actual subcooling is too large, and the condensing temperature of the heat pump is too high, resulting in a low heat pump performance coefficient cop.

[0065] Therefore, step fourteen is entered to revise the target superheat Tm;

[0066] Tm=Tm+K3=3℃+(-0.5℃)=2.5℃.

[0067] Next, according to the revised target superheat, the current opening of the electronic expansion valve is increased, and step two is entered, so that the heat pump is more in line with the design parameters to run.

[0068] 4) The central controller calculates and obtains the current actual subcooling Tr=5℃; Tr=5℃≤Y=2℃ is not true, so step six is entered.

[0069] Since step nine N4=3℃≤Tr=5℃<N3=8℃ is true, the central controller determines that the current opening of the electronic expansion valve is reasonable, and the heat pump runs in line with the design parameters.

[0070] Therefore, step fifteen is entered to revise the target superheat Tm;

[0071] Tm=Tm+K4=3℃+0℃=3℃.

[0072] Next, the electronic expansion valve maintains the current opening to continue running, i.e., step two is entered.

[0073] 5) The central controller calculates and obtains the current actual subcooling Tr=2.5℃; Tr=2.5℃≤Y=2℃ is not true, so step six is entered.

[0074] Since Tr=2.5℃<N4=3℃, the central controller determines that the current subcooling of the heat pump is too large, which may cause the throttled refrigerant to flash, resulting in a low heat pump performance.

[0075] Step ten is entered.

[0076] The target superheat Tm is revised;

[0077] Tm=Tm+K4=3℃+1℃=4℃.

[0078] Next, the heat pump continues to operate with the target return gas superheat Tm = 4°C, i.e. enters step two.

[0079] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0080] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A control method of an electronic expansion valve of a heat pump, characterized by The high-pressure outlet of the compressor (9) of the heat pump is communicated with the D interface of the electromagnetic four-way reversing valve (1), the C interface of the electromagnetic four-way reversing valve (1) is communicated with one end of the evaporator (6), the other end of the evaporator (6) is communicated with the refrigerant side of the plate heat exchanger (11) through the electronic expansion valve (8), the other refrigerant side of the plate heat exchanger (11) is communicated with the E interface of the electromagnetic four-way reversing valve (1), the S interface of the electromagnetic four-way reversing valve (1) is communicated with the low-pressure inlet of the compressor (9), the other end of the evaporator (6) is provided with an external coil temperature sensor (7), the pipeline between the S interface of the electromagnetic four-way reversing valve (1) and the low-pressure inlet of the compressor (9) is respectively provided with a return air temperature sensor (2) and a low-pressure pressure sensor (4), the pipeline between the D interface of the electromagnetic four-way reversing valve (1) and the high-pressure outlet of the compressor (9) is respectively provided with a high-pressure pressure sensor (3) and an exhaust temperature sensor (5), and the pipeline between the electronic expansion valve (8) and the refrigerant side of the plate heat exchanger (11) is provided with an internal coil temperature sensor (10), and the operation comprises the following steps: Step one, the heat pump is powered on, and step two is entered; Step two, normal operation, step three is entered; Step three, the central controller of the heat pump judges whether Td-Tm≤K is established, when it is established, step four is entered, otherwise step ten is entered, wherein Td is the current actual return air superheat degree, Tm is the target return air superheat degree, the value range of Tm is 0-10 DEG C, and K is a set difference value, the value range of K is 0-20 DEG C; Step four, the central controller calculates and obtains the current actual supercooling degree Tr, and step five is entered; Wherein, when the heat pump is refrigerating, Tr=T2-T3; when the heat pump is heating, Tr=T2-T6; T2 is the condensation temperature after high-pressure pressure conversion, T3 is the internal coil temperature, and T6 is the external coil temperature; Step five, the central controller judges whether Tr≤Y is established, when it is established, step two is entered, otherwise step six is entered, wherein Y is a set threshold value, and the value range of Y is 0-20 DEG C; Step six, the central controller judges whether Tr≥N1 is established, when it is established, step twelve is entered, otherwise step seven is entered, wherein N1 is a first set supercooling degree, and the value range of N1 is 16-19 DEG C; Step seven, the central controller judges whether N2≤Tr<N1 is established, when it is established, step thirteen is entered, otherwise step eight is entered, wherein N2 is a second set supercooling degree, and the value range of N2 is 12-15 DEG C; Step eight, the central controller judges whether N3≤Tr<N2 is established, when it is established, step fourteen is entered, otherwise step nine is entered, wherein N3 is a third set supercooling degree, and the value range of N3 is 5-11 DEG C; Step nine, the central controller judges whether N4≤Tr<N3 is established, when it is established, step fifteen is entered, otherwise step ten is entered, wherein N4 is a fourth set supercooling degree, and the value range of N4 is 0-4 DEG C; Step ten, Tm=Tm+K5, enter step two, wherein K5 is the fifth correction value, K5 is in the range of 0.9℃-1.8℃; Step eleven, continue to adjust, enter step three; Step twelve, Tm=Tm+K1, enter step two, K1 is the first correction value, K1 is in the range of -1.9℃--1.2℃; Step thirteen, Tm=Tm+K2, enter step two, K2 is the second correction value, K2 is in the range of -1.3℃--0.9℃; Step fourteen, Tm=Tm+K3, enter step two, K3 is the third correction value, K3 is in the range of -0.8℃--0.2℃; Step fifteen, Tm=Tm+K4, enter step two, K4 is the fourth correction value, K4 is in the range of -0.1℃-0.8℃.

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