A method for operating a heat pump

Abstract

A method for operating a heat pump includes the following steps: Step 1, powering on the heat pump and proceeding to Step 2; Step 2, normal heating operation with Y = 0, proceeding to Step 3, where Y represents the number of cycles; Step 3, the heat pump's central controller determines whether Th ≥ Tm is true. If true, proceed to Step 4; otherwise, proceed to Step 2, where Th is the continuous operating time at the same frequency, and Tm is a first set time, with a value ranging from 10 to 40 minutes; Step 4, detecting the current return gas temperature and evaporation temperature, calculating the return gas superheat Ts through the central controller, and proceeding to Step 5, where return gas superheat Ts = return gas temperature - evaporation temperature; Step 5, the central controller determines whether Ts ≥ 0 is true. If true, proceed to Step 15; otherwise, proceed to Step 6, where Ts is the return gas superheat; Step 6, detecting Pn. This invention features stable and reliable operation.

Description

Technical Field

[0001] This invention relates to a heat pump, and more particularly to a method for operating a heat pump. Background Technology

[0002] With the development of heat pump heating technology, more and more heat pumps are being used in cold and frigid regions. These areas have low ambient temperatures and require higher outlet water temperatures to ensure heating needs are met. However, some users still set their heat pumps to temperatures below 30℃ in these conditions. Due to uneven flow distribution in the evaporator flow path, problems arise in controlling the return gas superheat. Return gas superheat = return gas temperature - evaporation temperature. When a low-pressure sensor is present, the evaporation temperature equals the temperature corresponding to the low-pressure level. When no low-pressure sensor is present, the evaporation temperature is the temperature detected by the temperature sensor located on the outdoor heat exchanger.

[0003] Because the temperature of the outdoor heat exchanger is easily affected by the temperature of its pipes, it can cause a large difference between the temperature and the actual evaporation temperature. This results in a low opening degree of the main electronic expansion valve, also known as the first electronic expansion valve, and may even lead to a negative return gas superheat value.

[0004] When the evaporation temperature is the same as the temperature on the outdoor heat exchanger, and defrosting is difficult due to low water and ambient temperatures, frost buildup on the outdoor heat exchanger causes refrigerant condensation and liquid accumulation. This results in only a small amount of refrigerant entering the compressor, leading to a negative return gas superheat. At this point, the first electronic expansion valve is already closed to its minimum value. Since the conditions for initiating defrosting generally require a certain defrosting temperature difference (where defrosting temperature difference = ambient temperature - outdoor heat exchanger temperature), the defrosting temperature difference is typically small when the return gas superheat is negative. This causes the heat pump to have frost but not initiate defrosting, resulting in very low operating capacity and difficulty meeting customer needs. Therefore, improvements are needed. Summary of the Invention

[0005] The purpose of this invention is to provide a stable and reliable operating method for a heat pump, overcoming the shortcomings of the prior art.

[0006] A heat pump operation method designed for this purpose is characterized by the following steps: the high-pressure outlet of the compressor is connected to the first port of a solenoid four-way valve; the second port of the solenoid four-way valve is connected to one end of the evaporator; the other end of the evaporator is connected to the refrigerant side of the condenser via a first electronic expansion valve; the other side of the refrigerant in the condenser is connected to the third port of the solenoid four-way valve; the fourth port of the solenoid four-way valve is connected to the inlet pipe of a gas-liquid separator; and the outlet pipe of the gas-liquid separator is connected to the low-pressure inlet of the compressor. The operation includes the following steps:

[0007] Step 1: Power on the heat pump, then proceed to Step 2;

[0008] Step two: Run the heating system normally and assign Y=0, then proceed to step three, where Y represents the number of cycles.

[0009] Step 3: The heat pump's central controller determines whether Th≥Tm is true. If it is true, proceed to step 4; otherwise, proceed to step 2. Here, Th is the running time for continuous operation at the same operating frequency, and Tm is the first set time. The value of Tm ranges from 10 to 40 minutes.

[0010] Step 4: Detect the current return gas temperature and evaporation temperature, calculate the return gas superheat Ts through the central controller, and proceed to step 5: Return gas superheat Ts = return gas temperature - evaporation temperature;

[0011] Step 5: The central controller determines whether Ts≥0 is true. If it is true, proceed to step 15; otherwise, proceed to step 6. Here, Ts is the return gas superheat.

[0012] Step six, detect Pn and transmit it to the central controller, proceed to step seven, where Pn is the current opening value of the first electronic expansion valve (9);

[0013] Step 7: The central controller determines whether Pn > P0 is true. If it is true, proceed to step 4; otherwise, proceed to step 8. Here, P0 is the minimum opening value of the first electronic expansion valve.

[0014] Step 8: The central controller controls the first electronic expansion valve (9) to run continuously for K minutes with P1 as the current opening value. After the operation is completed, proceed to step 9. Here, P1 is the opening value of the first electronic expansion valve (9) from 30% to 60%, K is the second set time, and the value range of K is 0 to 15 minutes.

[0015] Step nine, run normally for Z minutes, then proceed to step ten, where Z is the third set time, and the value of Z ranges from 0 to 40 minutes;

[0016] Step 10: The central controller determines whether it is currently in defrost mode. If it is, proceed to step 11; otherwise, proceed to step 13.

[0017] Step 11: Perform defrosting, then proceed to Step 12;

[0018] Step 12: The central controller determines whether the defrosting process has been completed. If yes, proceed to step 2; otherwise, proceed to step 11.

[0019] Step thirteen, Y = Y + 1, proceed to step fourteen.

[0020] Step 14: The central controller determines whether Y≥3 is true. If it is true, proceed to step 11; otherwise, proceed to step 4.

[0021] Step 15: Continue running to step 3.

[0022] Furthermore, in step three, if the heat pump continuously operates at its maximum operating frequency Th under the current ambient temperature, then the heat pump's central controller determines whether 2Th≥Tm is true.

[0023] Under high humidity conditions, after a heat pump has been running for a period of time, the surface of the outdoor finned heat exchanger will quickly frost over, leading to a decrease in its heat exchange efficiency. At this time, the temperature sensor on the outdoor finned heat exchanger will typically receive a temperature 4°C to 5°C lower than the ambient temperature, rather than the actual evaporation temperature. This will result in a negative return gas superheat. However, at this point, the first electronic expansion valve is already at its minimum opening, causing a large amount of refrigerant to accumulate in the evaporator, rapidly reducing the heat pump's heating capacity. In this situation, the present invention increases the heating capacity by increasing the opening of the main electronic expansion valve, i.e., increasing the opening of the first electronic expansion valve, and the refrigerant can be circulated back to the compressor; thus, this method allows the heat pump to re-establish refrigerant circulation.

[0024] This invention monitors the operating status of the heat pump in real time through a central controller. When it detects that the heat pump is frosting and not defrosting or has poor working capacity, the central controller controls the opening of the main electronic expansion valve or forcibly resets the heat pump through defrosting to improve the operating capacity of the heat pump and ensure that the heat pump can operate stably and reliably for a long time.

[0025] This invention can effectively reduce the problems of frost buildup and failure to defrost or heat up caused by using the temperature collected by the temperature sensor on the outdoor heat exchanger as the evaporation temperature of the heat pump. It makes the operation of the heat pump more reasonable when the water output is low, and has high efficiency, stability and reliability, which makes users more satisfied.

[0026] After adopting the above-mentioned technical solution, the present invention can enable the heat pump to re-establish the refrigerant cycle: if the return gas superheat is still negative after three cycles, the central controller will restart the heat pump to the initial state of the evaporator through forced defrosting.

[0027] In summary, this invention features stable and reliable operation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention.

[0029] Figure 2 This is the control flowchart of the present invention.

[0030] In the diagram: 1 is the evaporator, 2 is the ambient temperature sensor, 3 is the evaporator temperature sensor, 4 is the electromagnetic four-way valve, 5 is the exhaust temperature sensor, 6 is the compressor, 7 is the return gas temperature sensor, 8 is the condenser, 9 is the first electronic expansion valve, and 10 is the gas-liquid separator. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] See Figures 1-2 A method for operating a heat pump, wherein the high-pressure outlet of compressor 6 is connected to the first port of electromagnetic four-way valve 4, the second port of electromagnetic four-way valve 4 is connected to one end of evaporator 1, the other end of evaporator 1 is connected to the refrigerant side of condenser 8 through a first electronic expansion valve 9, the other side of refrigerant in condenser 8 is connected to the third port of electromagnetic four-way valve 4, the fourth port of electromagnetic four-way valve 4 is connected to the inlet pipe of gas-liquid separator 10, and the outlet pipe of gas-liquid separator 10 is connected to the low-pressure inlet of compressor 6. The operation includes the following steps:

[0033] Step 1: Power on the heat pump, then proceed to Step 2;

[0034] Step two: Run the heating system normally and assign Y=0, then proceed to step three, where Y represents the number of cycles.

[0035] Step 3: The heat pump's central controller determines whether Th≥Tm is true. If it is true, proceed to step 4; otherwise, proceed to step 2. Here, Th is the running time for continuous operation at the same operating frequency, and Tm is the first set time. The value of Tm ranges from 10 to 40 minutes.

[0036] Step 4: Detect the current return gas temperature and evaporation temperature, calculate the return gas superheat Ts through the central controller, and proceed to step 5: Return gas superheat Ts = return gas temperature - evaporation temperature;

[0037] Step 5: The central controller determines whether Ts≥0 is true. If it is true, proceed to step 15; otherwise, proceed to step 6. Here, Ts is the return gas superheat.

[0038] Step six: Detect Pn and transmit it to the central controller, then proceed to step seven, where Pn is the current opening value of the first electronic expansion valve 9;

[0039] Step 7: The central controller determines whether Pn > P0 is true. If it is true, proceed to step 4; otherwise, proceed to step 8. Here, P0 is the minimum opening value of the first electronic expansion valve.

[0040] Step 8: The central controller controls the first electronic expansion valve 9 to run continuously for K minutes with P1 as the current opening value. After the operation is completed, proceed to step 9. Here, P1 is 30% to 60% of the full opening value of the first electronic expansion valve 9, and K is the second set time. The value range of K is 0 to 15 minutes.

[0041] Step nine, run normally for Z minutes, then proceed to step ten, where Z is the third set time, and the value of Z ranges from 0 to 40 minutes;

[0042] Step 10: The central controller determines whether it is currently in defrost mode. If it is, proceed to step 11; otherwise, proceed to step 13.

[0043] Step 11: Perform defrosting, then proceed to Step 12;

[0044] Step 12: The central controller determines whether the defrosting process has been completed. If yes, proceed to step 2; otherwise, proceed to step 11.

[0045] Step thirteen, Y = Y + 1, proceed to step fourteen.

[0046] Step 14: The central controller determines whether Y≥3 is true. If it is true, proceed to step 11; otherwise, proceed to step 4.

[0047] Step 15: Continue running to step 3.

[0048] In step three, if the heat pump continues to operate at its maximum operating frequency Th at the current ambient temperature, the heat pump's central controller will determine whether 2Th≥Tm is true.

[0049] Application examples

[0050] Set the first set time Tm to 10 minutes, the first electronic expansion valve P1 to 40% opening value, K = 2 minutes, and Z = 10 minutes.

[0051] Since the minimum opening value of different electronic expansion valves is not the same, in practice, the minimum opening value P0 of the first electronic expansion valve needs to be set according to the specific electronic expansion valve selected.

[0052] 1) When the heat pump is in heating mode, if it is detected that the heat pump has been running continuously at the same operating frequency for Th = 10 minutes, the central controller determines that Th ≥ Tm is true and proceeds to step four. The return gas superheat Ts is calculated, and different approaches are taken depending on whether Ts ≥ 0 is true: if it is true, the heat pump continues to run in normal mode; if it is not true, the current opening value Pn of the first electronic expansion valve 9 is detected and it is determined whether Pn > P0 is true. If it is not true, the first electronic expansion valve runs at an opening value of P1 = 40% for K = 2 minutes. After 2 minutes of operation, the heat pump continues to run in normal mode for Z = 10 minutes. If the heat pump does not enter defrost after Z = 10 minutes of operation, it proceeds to step thirteen. After calculating Y = Y + 1, if the central controller determines that Y ≥ 3 is not true, it proceeds to step four.

[0053] 2) When the heat pump is in heating mode, if Y=3, it means that after three cycles, the return gas superheat Ts is still negative. In this case, the central controller will restart the heat pump evaporator state by forcibly defrosting.

[0054] 3) When the heat pump is in heating mode, if it is detected that the heat pump has been running continuously at the maximum operating frequency for Th = 10 minutes at the current ambient temperature, the central controller of the heat pump will determine whether 2Th ≥ Tm is true; see 1 for the rest of the unmentioned parts.

[0055] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for operating a heat pump, characterized in that: The high-pressure outlet of the compressor (6) is connected to the first port of the electromagnetic four-way valve (4), the second port of the electromagnetic four-way valve (4) is connected to one end of the evaporator (1), the other end of the evaporator (1) is connected to the refrigerant side of the condenser (8) through the first electronic expansion valve (9), the other side of the refrigerant side of the condenser (8) is connected to the third port of the electromagnetic four-way valve (4), the fourth port of the electromagnetic four-way valve (4) is connected to the inlet pipe of the gas-liquid separator (10), and the outlet pipe of the gas-liquid separator (10) is connected to the low-pressure inlet of the compressor (6). During operation, the following steps are included: Step 1: Power on the heat pump, then proceed to Step 2; Step 2: Run the heating system normally and assign Y=0, then proceed to Step 3, where Y is the number of cycles; Step 3: The heat pump's central controller determines whether Th≥Tm is true. If it is true, proceed to step 4; otherwise, proceed to step 2. Here, Th is the running time for continuous operation at the same operating frequency, and Tm is the first set time. The value of Tm ranges from 10 to 40 minutes. Step 4: Detect the current return gas temperature and evaporation temperature, calculate the return gas superheat Ts through the central controller, and proceed to step 5: Return gas superheat Ts = return gas temperature - evaporation temperature; Step 5: The central controller determines whether Ts≥0 is true. If it is true, proceed to step 15; otherwise, proceed to step 6. Here, Ts is the return gas superheat. Step six, detect Pn and transmit it to the central controller, proceed to step seven, where Pn is the current opening value of the first electronic expansion valve (9); Step 7: The central controller determines whether Pn > P0 is true. If it is true, proceed to step 4; otherwise, proceed to step 8. Here, P0 is the minimum opening value of the first electronic expansion valve. Step 8: The central controller controls the first electronic expansion valve (9) to run continuously for K minutes with P1 as the current opening value. After the operation is completed, proceed to step 9. Here, P1 is the 30% to 60% opening value of the first electronic expansion valve (9), K is the second set time, and the value range of K is 0 to 15 minutes. Step 9: Continue running in normal mode for Z minutes, then proceed to Step 10, where Z is the third set time, and the value of Z ranges from 0 to 40 minutes. Step 10: The central controller determines whether it is currently in defrost mode. If it is, proceed to step 11; otherwise, proceed to step 13. Step 11: Perform defrosting, then proceed to Step 12; Step 12: The central controller determines whether the defrosting process has been completed. If yes, proceed to step 2; otherwise, proceed to step 11. Step thirteen: Increment the previously updated loop count Y by 1, and proceed to step fourteen; Step 14: The central controller determines whether Y≥3 is true. If it is true, proceed to step 11; otherwise, proceed to step 4. Step 15: Continue running to step 3.

2. The method for operating a heat pump according to claim 1, characterized in that: In step three, if the heat pump continuously operates at its maximum operating frequency Th under the current ambient temperature, then the judgment condition of the heat pump's central controller in step three is replaced with whether 2Th≥Tm is true.

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