Operating method of an air source heat pump with low ambient temperature and high water temperature

Abstract

An operating method for an air-source heat pump with low ambient temperature and high water temperature includes the following steps: Step 1, the heat pump is powered on and started, proceeding to Step 2; Step 2, the heat pump's central controller determines whether the current ambient temperature Ta > the first set temperature t3 or the current outlet water temperature Tb > the second set temperature t4. If so, proceed to Step 12; otherwise, proceed to Step 3; wherein the first set temperature t3 ranges from -5℃ to -15℃, and the second set temperature t4 ranges from 30℃ to 40℃; Step 3, the heat pump starts in cooling mode, proceeding to Step 4; Step 4, the compressor operates at a first frequency F1, wherein F1 ranges from 30Hz to 38Hz; Step 5, the opening degree of the first electronic expansion valve is set to 78% to 98% of its full opening, proceeding to Step 6; Step 6, after a first operating time T1. This invention features safe and reliable operation.

Description

Technical Field

[0001] This invention relates to an air source heat pump, and more particularly to an operating method for an air source heat pump with low ambient temperature and high water temperature. Background Technology

[0002] Under environmental policies promoting carbon neutrality and energy conservation and emission reduction, air source heat pump products are seeing increasing sales in the northern market and are gradually replacing wall-mounted boilers in extremely cold regions. In these frigid areas, due to prolonged shutdown times after reaching the set temperature, as well as issues like shutdowns for outings or sudden power outages, the water temperature of the heat pump compressor often remains relatively high even after it has stopped running for a period. When starting the heat pump under these conditions, the compressor is highly susceptible to oil shortage, increasing the risk of compressor damage.

[0003] In response to this situation, some manufacturers have made improvements. For example, Chinese Patent Document No. CN 212806136 U, published on March 26, 2021, discloses a high-efficiency air-source heat pump unit for ultra-low temperature environments with high water temperature. This unit includes a compressor, a four-way valve, a condenser, an evaporator, an economizer, and a first regenerator. The inlet of the four-way valve is connected to the outlet of the compressor. The first port of the four-way valve is connected to the condenser. The condenser is connected to the first port of the economizer. The second port of the economizer is connected to the first regenerator. The second port of the four-way valve is connected to the evaporator. The outlet of the evaporator is connected to the superheat inlet of the first regenerator. The superheat outlet of the first regenerator is connected to the evaporator through a throttling device. The outlet of the evaporator is connected to the subcooling inlet of the first regenerator through the four-way valve. The subcooling outlet of the first regenerator is connected to the compressor pump. However, the actual performance of this high-efficiency air-source heat pump unit for ultra-low temperature environments is not ideal and needs further improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a stable and reliable operating method for an air-source heat pump with low ambient temperature and high water temperature, in order to overcome the shortcomings of the prior art.

[0005] An operating method for an air-source heat pump with low ambient temperature and high water temperature, designed for this purpose, is characterized in that the heat pump includes a compressor, an evaporator, a condenser, a four-way reversing valve, and an economizer. The high-pressure outlet of the compressor is connected to the first port of the four-way reversing valve, the second port of the four-way reversing valve is connected to the refrigerant inlet of the evaporator, the refrigerant outlet of the evaporator is connected to the refrigerant inlet of the condenser through the first branch of the economizer, a first electronic expansion valve is connected in series between the refrigerant outlet of the evaporator and the first branch of the economizer, the refrigerant outlet of the condenser is connected to the fourth port of the four-way reversing valve, and the third port of the four-way reversing valve is connected to the... The compressor's low-pressure inlet is connected. One end of the second electronic expansion valve is connected in series between the first electronic expansion valve and the first branch of the economizer. The other end of the second electronic expansion valve is connected to the compressor's medium-pressure inlet through the second branch of the economizer. A water outlet temperature sensor for detecting the current water outlet temperature Tb is installed on the condenser's water outlet pipe. A water inlet temperature sensor is installed on the condenser's water inlet pipe. A discharge temperature sensor is installed at the compressor's high-pressure outlet. A return gas temperature sensor is installed at the compressor's low-pressure inlet. An ambient temperature sensor for detecting the current ambient temperature Ta is installed on the evaporator. The operation includes the following steps:

[0006] Step 1: Power on the heat pump and proceed to Step 2;

[0007] Step 2: If the heat pump's central controller determines that the current ambient temperature Ta > the first set temperature t3 or the current outlet water temperature Tb > the second set temperature t4, proceed to step 12; otherwise, proceed to step 3.

[0008] The first set temperature t3 ranges from -5℃ to -15℃, and the second set temperature t4 ranges from 30℃ to 40℃.

[0009] Step 3: The heat pump starts in cooling mode, proceed to step 4;

[0010] Step four: The compressor operates at a first frequency F1, where the value of F1 ranges from 30Hz to 38Hz.

[0011] Step 5: Set the opening of the first electronic expansion valve to 78% to 98% of its full opening, then proceed to Step 6;

[0012] Step six: After the first running time T1, where T1 ranges from 3 minutes to 5 minutes, proceed to step seven;

[0013] Step 7: The central controller determines whether the return gas temperature Tm of the compressor is true or false. If it is true, proceed to step 8; otherwise, proceed to step 6.

[0014] Step 8: The heat pump operates in heating mode; proceed to step 9.

[0015] Step 9: Set the opening of the second electronic expansion valve to 48% to 80% of its full opening, then proceed to Step 10;

[0016] Step 10: The central controller determines whether the current exhaust superheat Tc is greater than or equal to the third set temperature t5. If it is, proceed to step 12; otherwise, proceed to step 11.

[0017] The value of t5 ranges from 10℃ to 25℃.

[0018] Step 11: After a second running time T2, where T2 ranges from 8 minutes to 20 minutes; proceed to Step 12;

[0019] Step 12: The opening degree of the second electronic expansion valve is controlled in the normal mode;

[0020] Step 13: The heat pump operates in heating mode.

[0021] The present invention adopts the above-mentioned technical solution, which can shorten the start-up time of heat pump with low ambient temperature and high water temperature, reduce oil return loss, improve the stability of heat pump operation, and solve the problem of insufficient exhaust superheat during heat pump heating start-up, and the problem of lubricating oil being carried out of the compressor by the refrigerant, thus ensuring the safe and reliable operation of heat pump. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention.

[0023] Figure 2 This is the control flowchart of the present invention.

[0024] In the diagram: 1 is the evaporator, 2 is the ambient temperature sensor, 3 is the gas-liquid separator, 4 is the first electronic expansion valve, 5 is the second electronic expansion valve, 6 is the economizer, 7 is the outlet water temperature sensor, 8 is the inlet water temperature sensor, 9 is the condenser, 10 is the compressor, 11 is the exhaust temperature sensor, 12 is the four-way reversing valve, and 13 is the return gas temperature sensor. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] See Figures 1-2An operating method for an air-source heat pump with low ambient temperature and high water temperature is disclosed. The heat pump comprises a compressor 10, an evaporator 1, a condenser 9, a four-way reversing valve 12, and an economizer 6. The high-pressure outlet of the compressor 10 is connected to the first port of the four-way reversing valve 12, the second port of the four-way reversing valve 12 is connected to the refrigerant inlet of the evaporator 1, the refrigerant outlet of the evaporator 1 is connected to the refrigerant inlet of the condenser 9 through the first branch of the economizer 6, a first electronic expansion valve 4 is connected in series between the refrigerant outlet of the evaporator 1 and the first branch of the economizer 6, the refrigerant outlet of the condenser 9 is connected to the fourth port of the four-way reversing valve 12, and the third port of the four-way reversing valve 12 is connected to the fourth port of the evaporator 12. The compressor 10 is connected to the low-pressure inlet. One end of the second electronic expansion valve 5 is connected in series between the first electronic expansion valve 4 and the first branch of the economizer 6. The other end of the second electronic expansion valve 5 is connected to the medium-pressure inlet of the compressor 10 through the second branch of the economizer 6. The condenser 9 is equipped with an outlet water temperature sensor 7 for detecting the current outlet water temperature Tb on the outlet water pipe. The condenser 9 is equipped with an inlet water temperature sensor 8 on the inlet water pipe. The compressor 10 is equipped with an exhaust gas temperature sensor 11 at the high-pressure outlet. The compressor 10 is equipped with a return gas temperature sensor 11 at the low-pressure inlet. The evaporator 1 is equipped with an ambient temperature sensor 2 for detecting the current ambient temperature Ta.

[0027] The operation includes the following steps:

[0028] Step 1: Power on the heat pump and proceed to Step 2;

[0029] Step 2: If the heat pump's central controller determines that the current ambient temperature Ta > the first set temperature t3 or the current outlet water temperature Tb > the second set temperature t4, proceed to step 12; otherwise, proceed to step 3.

[0030] The first set temperature t3 ranges from -5℃ to -15℃, and the second set temperature t4 ranges from 30℃ to 40℃.

[0031] Step 3: The heat pump starts in cooling mode, proceed to step 4;

[0032] Step four, the compressor 10 operates at a first frequency F1, wherein the value of F1 is in the range of 30Hz to 38Hz;

[0033] Step 5: Set the opening of the first electronic expansion valve 4 to 78% to 98% of its full opening, and proceed to Step 6.

[0034] Example: When the full opening degree of the first electronic expansion valve 4 is 500, the positive opening degree of the first electronic expansion valve 4 can be set to 390~490.

[0035] Step six: After the first running time T1, where T1 ranges from 3 minutes to 5 minutes, proceed to step seven;

[0036] Step 7: The central controller determines whether the return gas temperature Tm of compressor 10 is true or false. If it is true, proceed to step 8; otherwise, proceed to step 6.

[0037] Step 8: The heat pump operates in heating mode; proceed to step 9.

[0038] Step nine: Set the opening of the second electronic expansion valve 5 to 48% to 80% of its full opening, then proceed to step ten;

[0039] Example: When the full opening degree of the second electronic expansion valve 5 is 500, the positive opening degree of the second electronic expansion valve 5 can be set to 240~400.

[0040] Step 10: The central controller determines whether the current exhaust superheat Tc is greater than or equal to the third set temperature t5. If it is, proceed to step 12; otherwise, proceed to step 11.

[0041] The value of t5 ranges from 10℃ to 25℃.

[0042] Step 11: After a second running time T2, where T2 ranges from 8 minutes to 20 minutes; proceed to Step 12;

[0043] Step 12: The opening degree of the second electronic expansion valve 5 is controlled in the normal mode;

[0044] Step 13: The heat pump operates in heating mode.

[0045] In this embodiment, when entering normal control mode, after the heat pump system has been running for 3 minutes, the superheat of the first electronic expansion valve 4 is controlled according to the exhaust superheat Tc of the heat pump system.

[0046] When Tc ≤ 18℃, the opening of the first electronic expansion valve 4 is reduced every 30 seconds, in 6 steps each time. When 18℃ < Tc < 32℃, the opening of the first electronic expansion valve 4 is adjusted according to the return gas superheat of the heat pump system.

[0047] Return gas superheat Td = Return gas temperature - Condensation temperature.

[0048] The control of return gas superheat is as follows: when Td≤1℃, the opening of the first electronic expansion valve 4 is reduced every 30 seconds, in 6 steps each time; when 1℃<Td<3℃, the opening of the first electronic expansion valve 4 remains unchanged; when Td≥3℃, the opening of the first electronic expansion valve 4 is increased every 30 seconds, in 8 steps each time.

[0049] When Tc≥32℃, the opening of the first electronic expansion valve 4 is increased every 30 seconds, in 8 steps each time.

[0050] In this embodiment, when entering normal control mode, after the heat pump system has been running for 3 minutes, the superheat of the second electronic expansion valve 5 is controlled according to the superheat of the economizer Tk.

[0051] The superheat of the economizer, Tk, is equal to the economizer outlet temperature minus the economizer inlet temperature.

[0052] When Tk≤0, the opening of the second electronic expansion valve is reduced every 10 seconds, in 6 steps each time.

[0053] When 0 < Tk ≤ 2, the opening of the second electronic expansion valve remains at the current opening.

[0054] When Tk > 2, the opening of the second electronic expansion valve is increased every 10 seconds, in 8 steps each time.

[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. An operating method for an air-source heat pump with low ambient temperature and high water temperature, characterized in that: The heat pump includes a compressor (10), an evaporator (1), a condenser (9), a four-way reversing valve (12), and an economizer (6). The high-pressure outlet of the compressor (10) is connected to the first port of the four-way reversing valve (12), and the second port of the four-way reversing valve (12) is connected to the refrigerant inlet of the evaporator (1). The refrigerant outlet of the evaporator (1) is connected to the refrigerant inlet of the condenser (9) through the first branch of the economizer (6). A first electronic expansion valve (4) is connected in series between the refrigerant outlet of the evaporator (1) and the first branch of the economizer (6). The refrigerant outlet of the condenser (9) is connected to the fourth port of the four-way reversing valve (12), and the third port of the four-way reversing valve (12) is connected to the low-pressure inlet of the compressor (10). The second electronic expansion valve (5) is connected in series between the first electronic expansion valve (4) and the first branch of the economizer (6). The other end of the second electronic expansion valve (5) is connected to the medium-pressure inlet of the compressor (10) through the second branch of the economizer (6). The outlet water pipe of the condenser (9) is equipped with an outlet water temperature sensor (7) for detecting the current outlet water temperature Tb. The inlet water pipe of the condenser (9) is equipped with an inlet water temperature sensor (8). The high-pressure outlet of the compressor (10) is equipped with an exhaust temperature sensor (11). The low-pressure inlet of the compressor (10) is equipped with a return gas temperature sensor (11). The evaporator (1) is equipped with an ambient temperature sensor (2) for detecting the current ambient temperature Ta. The operation includes the following steps: Step 1: Power on the heat pump and proceed to Step 2; Step 2: If the heat pump's central controller determines that the current ambient temperature Ta > the first set temperature t3 or the current outlet water temperature Tb > the second set temperature t4, proceed to step 12; otherwise, proceed to step 3. The first set temperature t3 ranges from -5℃ to -15℃, and the second set temperature t4 ranges from 30℃ to 40℃. Step 3: The heat pump starts in cooling mode, proceed to step 4; Step four, the compressor (10) operates at a first frequency F1, wherein the value of F1 is in the range of 30Hz to 38Hz; Step 5: Set the opening of the first electronic expansion valve (4) to 78% to 98% of its full opening, and proceed to step 6; Step six: After the first running time T1, where T1 ranges from 3 minutes to 5 minutes, proceed to step seven; Step 7: The central controller determines whether the return gas temperature Tm of the compressor (10) is true or false. If it is true, proceed to step 8; otherwise, proceed to step 6. Step 8: The heat pump operates in heating mode; proceed to step 9. Step nine, set the opening degree of the second electronic expansion valve (5) to 48% to 80% of its full opening degree, and proceed to step ten; Step 10: The central controller determines whether the current exhaust superheat Tc is greater than or equal to the third set temperature t5. If it is, proceed to step 12; otherwise, proceed to step 11. The value of t5 ranges from 10℃ to 25℃. Step 11: After a second running time T2, where T2 ranges from 8 minutes to 20 minutes; proceed to Step 12; Step 12: The opening degree of the second electronic expansion valve (5) is controlled in the normal mode; Step 13: The heat pump operates in heating mode.

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