A large-scale air source heat pump heat exchange system and defrosting control method

Abstract

A large-scale air-source heat pump heat exchange system and defrost control method belong to the technical field of heat pump systems. The air heat exchanger is connected to the heat exchange branch; the heat exchange branch is connected to the heating circuit through the evaporator, and the heating circuit is connected to the heat supply branch through the condenser; the air heat exchanger is connected to the defrost branch, and the defrost branch is connected to the cold and hot water tanks; the hot water tank is connected to both ends of the heating branch; the heating branch is connected to the heat storage branch through an intermediate heat exchanger; both ends of the heat storage branch are connected to the heating branch; a compressor and a throttle valve are installed on the heating circuit; and the heating branch is connected to the end. During defrosting, the low-temperature refrigerant in the air heat exchanger enters the cold water tank through the defrost branch, and the high-temperature refrigerant in the hot water tank enters the air heat exchanger through the defrost branch for defrosting. The high-temperature refrigerant after defrosting flows back to the hot water tank through the defrost branch, and the low-temperature refrigerant in the cold water tank flows back to the air heat exchanger through the defrost branch, completing the defrost process. The present invention is used for defrosting large-scale air-source heat pump heat exchange systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat pump systems, and in particular relates to a large-scale air source heat pump heat exchange system and a defrosting control method. Background Art

[0002] Nowadays, clean energy heating technologies have replaced traditional coal-fired and gas-fired heating as the mainstream heating technology. Air-source heat pumps, with their energy-saving, environmentally friendly, and wide adaptability, are one of the most widely used clean energy heating methods. Traditional scroll compressor units have limited heat capacity per unit, hindering the further development of air-source heat pumps. Consequently, numerous companies and research institutions are developing high-capacity units powered by large screw compressors. Currently, the development of screw air-source heat pumps faces two limitations: excessive noise levels and the risk of refrigerant leakage during long-distance transmission. Screw compressors are extremely noisy when installed in open spaces. When installed in a soundproof room far from the evaporator, long-distance two-phase refrigerant transmission requires significant investment and system shutdown in the event of a refrigerant leak. Furthermore, for the compressor, the effective area for refrigerant phase change heat transfer within the evaporator is not proportional to the total heat exchange area of the evaporator. Therefore, the evaporator and compressor must be designed in a one-to-one relationship. When a single compressor is shut down, the corresponding evaporator is idle. Because the evaporator area associated with a single screw compressor is very large, the overall energy efficiency of the unit is significantly reduced when operating at less than full power. Based on the principle of an air heat exchanger, a two-stage heat exchange method using antifreeze as a refrigerant to exchange heat with the air and refrigerant respectively can fully utilize the evaporator and improve the overall energy efficiency of the system. Patent application number 201910956359.9, filed on October 10, 2019, discloses a "large-scale air source heat pump low-energy operation system and control method." Based on this principle, one air heat exchanger corresponds to the heating form of multiple heat pump units. At the same time, because the refrigerant flows in a single phase in the pipeline, there is no problem of heat loss during long-distance transmission, and a small amount of leakage will not have a significant impact on the system. Therefore, the use of a two-stage heat transfer method to independently connect multiple groups of air heat exchangers and multiple compressors in parallel can effectively solve the noise and leakage problems of the screw unit. However, the technical solution of this patent is too simple and cannot meet the requirements of low temperature and high humidity operating conditions. When operating in cold areas, problems such as severe frost on the heat exchanger surface, deterioration of the operating conditions of the compressor unit, and reduced heating capacity will occur.

[0003] When the outdoor air reaches frosting conditions, the air heat exchanger extracts heat from the air through low-temperature refrigerant, causing frost formation similar to that of an evaporator. Frosted heat exchangers reduce heat transfer capacity and increase windage, leading to reduced heating efficiency for the entire system. Air heat exchangers are generally defrosted using external spraying or internal heating. External spraying involves spraying a high-concentration antifreeze solution onto the heat exchanger surface to melt frost and lower the freezing point. This defrosting method results in uneven defrosting and a short frost formation interval. While it can alleviate frost formation, it struggles to completely defrost the frost, and the refrigerant is prone to drifting, causing environmental pollution. Heating defrost is similar to the traditional air source heat pump hot gas bypass defrosting method. This method heats all or part of the refrigerant in the heat exchange system to a higher temperature, raising the overall temperature of the heat exchanger and thereby achieving the desired defrost. The defrosting effect of this defrosting method depends on the temperature of the defrosting refrigerant and the heating time. The higher the refrigerant temperature and the longer the heating time, the better the defrosting effect and the longer the frost formation interval. Unlike the hot gas bypass method, which only requires heating a small amount of refrigerant in the evaporator, the antifreeze can only rely on sensible heat exchange. Taking R134a and a 45w% ethylene glycol water solution with a heat exchange temperature difference of 4K as an example, the flow rate of the ethylene glycol water solution is more than 15 times that of R134a at the same temperature and heating capacity. In addition, the heat transfer coefficient of the evaporator is more than 10 times that of the air heat exchanger. Therefore, it is unrealistic to heat the entire refrigerant in the air heat exchanger from an operating temperature of around -15°C to a defrost temperature of over 20°C in a short period of time. At the same time, due to the hysteresis of heat conduction, when frost still condenses on some fin surfaces, the temperature of most of the antifreeze is already significantly higher than the ambient temperature. Only a small part of the heat lost by the antifreeze is used for defrosting. Most of it is carried away by the fan during the cooling process after defrosting, resulting in heat loss in the system. When the ambient humidity is high and the heat exchanger frequently frosts, the heating efficiency of the unit will be seriously affected.

[0004] Therefore, there is an urgent need for a new large-scale air source heat pump heat exchange system and its defrost control method to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a large air source heat pump low energy consumption rapid defrosting heat exchange system to solve the problems of long defrosting time and high energy consumption of existing large air source heat pump systems.

[0006] In addition, the existing thermal defrosting method is time-consuming, the defrosting is uneven, the energy consumption is high, and the defrosting affects the stability of the terminal heating supply.

[0007] The present invention shortens the preheating time by adding a hot water tank, reduces heat loss during the defrosting process by exchanging hot and cold fluids, and reduces the impact of defrosting on the heating stability of the system by group defrosting (the outdoor air heat exchanger is divided into multiple groups. When one group of heat exchangers is severely frosted and needs to be defrosted, the defrost branch is used to defrost the heat exchanger in accordance with the defrost process, while the other groups of heat exchangers normally take heat from the outdoor air for heat exchange, and the unit always maintains the heating working mode).

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A large air source heat pump heat exchange system includes a heat exchange branch, an evaporator, a compressor, a condenser, a throttle valve, a regulating valve, a heating circuit, a heating branch, a defrosting branch, a heating branch, a heat storage branch, an intermediate heat exchanger, a cold water tank, a hot water tank and multiple air heat exchangers;

[0010] The inlet and outlet of each air heat exchanger are respectively provided with two branch inlets and two branch outlets. The two branch inlets are respectively the first branch inlet and the second branch inlet, and the two branch outlets are respectively the first branch outlet and the second branch outlet. The first branch inlet and the first branch outlet of each air heat exchanger are connected with the two ends of the heat exchange branch to form a heat exchange circuit; the heat exchange branch is connected with the heating circuit through the evaporator, and the heating circuit is connected with the heating branch through the condenser; the second branch inlet and the second branch outlet of the air heat exchanger are connected with the two ends of one side of the defrost branch, and one end of the other side of the defrost branch is divided into two branches and connected to the cold water tank at the same time. The inlet is connected with the first inlet of the hot water tank, and the other end on the other side of the defrost branch is also divided into two branches and is connected with the cold water tank outlet and the first outlet of the hot water tank at the same time, thereby forming a defrost circuit; the side wall of the hot water tank is connected with both ends of the heating branch to form a heating circuit; the heating branch and the heat storage branch are connected through an intermediate heat exchanger; both ends of the heat storage branch are connected to the return water pipe of the heating branch, and a regulating valve is installed on the heating branch between the two connection points at both ends of the heat storage branch; a compressor is installed on the outbound pipe of the heating circuit, and a throttle valve is installed on the return pipe of the heating circuit; both ends of the heating branch are connected with the end to form a heating circuit.

[0011] Furthermore, the air source heat pump heat exchange system further includes a fifth solenoid valve, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, a plurality of first solenoid valves, a plurality of second solenoid valves, a plurality of third solenoid valves and a plurality of fourth solenoid valves;

[0012] A first solenoid valve is installed at the connection position between the first branch inlet of each air heat exchanger and the heat exchange branch, and a second solenoid valve is installed at the connection position between the first branch outlet of each air heat exchanger and the heat exchange branch; a third solenoid valve is installed at the connection position between the second branch inlet of each air heat exchanger and the defrost branch, and a fourth solenoid valve is installed at the connection position between the second branch outlet of each air heat exchanger and the defrost branch; a fifth solenoid valve is installed at the connection position between the cold water tank inlet and the defrost branch, a sixth solenoid valve is installed at the connection position between the first outlet of the hot water tank and the defrost branch, a seventh solenoid valve is installed at the connection position between the first inlet of the hot water tank and the defrost branch, and an eighth solenoid valve is installed at the connection position between the cold water tank outlet and the defrost branch.

[0013] Furthermore, the air source heat pump heat exchange system also includes four circulation pumps, namely an intermediate pump, a terminal pump, a defrost pump and a heat storage pump; a defrost pump is installed on the defrost branch located on the refrigerant inlet branch; an intermediate pump is installed on the heat exchange branch, and the intermediate pump is located between the first branch inlet of the air heat exchanger and the evaporator; a terminal pump is installed on the heating pipeline of the heating branch; a heat storage pump is installed on the heating branch, and the heat storage pump is arranged between the second outlet of the hot water tank and the intermediate heat exchanger.

[0014] A control method for heat exchange defrosting of a large air source heat pump, the method comprising the following steps:

[0015] S101: Obtaining frost conditions of an air heat exchanger;

[0016] S102: Determine whether the frost condition of the air heat exchanger meets the defrosting standard; if yes, execute step S103; if not, execute step S101 again;

[0017] S103: The heat exchange branch is disconnected and the defrost branch is connected, controlling the heat exchange fan of the air heat exchanger to stop rotating. The high-temperature refrigerant in the hot water tank flows into the air heat exchanger through the defrost branch for heat exchange. The refrigerant after heat exchange flows out of the air heat exchanger and flows into the cold water tank through the defrost branch.

[0018] S104: When the refrigerant level in the cold water tank reaches a first preset liquid level, disconnecting the defrost branch from the cold water tank inlet and connecting the first inlet of the hot water tank. The refrigerant flowing out of the air heat exchanger flows into the hot water tank through the defrost branch.

[0019] S105: When the surface temperature of the air heat exchanger fin reaches a preset temperature, the heat exchange fan of the air heat exchanger is controlled to rotate;

[0020] S106: After the preset time has elapsed, the connection between the defrost branch and the first outlet of the hot water tank is disconnected, and the outlet of the cold water tank is connected. The low-temperature refrigerant in the cold water tank flows out from the outlet of the cold water tank and flows into the air heat exchanger through the defrost branch. The high-temperature refrigerant in the air heat exchanger flows out from the second branch outlet of the air heat exchanger and flows into the hot water tank through the defrost branch and the first inlet of the hot water tank.

[0021] S107: When the refrigerant level in the cold water tank reaches a second preset liquid level, the heat exchange branch is connected and the defrost branch is disconnected, ending the defrost cycle of the air heat exchanger.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: on the basis of the traditional method of heating refrigerant for defrosting, the present invention adds cold and hot water tanks and corresponding heat storage and heating branches. When the air source heat pump heat exchange system is normally supplying heat, the refrigerant in the hot water tank is heated to the temperature required for defrosting through the heat storage process; when the defrost mode is running, the low-temperature refrigerant in the air heat exchanger is introduced into the cold water tank, and the high-temperature refrigerant in the hot water tank is introduced into the air heat exchanger. It is no longer necessary to spend a lot of time heating the original low-temperature refrigerant in the air heat exchanger, which greatly shortens the heating and defrosting time. At the same time, since the high-temperature refrigerant introduced from the hot water tank has a consistent temperature and a high flow rate, the refrigerant will not form a significant temperature gradient in the air heat exchanger, and the frost layer on the fin surface can be melted at a similar rate, effectively avoiding uneven defrosting caused by uneven refrigerant temperature during the heating process. To ensure defrosting efficiency and effect, the refrigerant temperature before and after defrosting is much higher than the ambient temperature. This part of the high-temperature refrigerant after defrosting is retained in the air heat exchanger. After the heat exchange fan is started, all the heat is dissipated into the surrounding environment, causing serious heat loss. The heat exchange system proposed in the present invention will re-introduce the low-temperature refrigerant in the cold water tank into the air heat exchanger through the defrost branch after the defrosting is completed, and the original high-temperature refrigerant in the air heat exchanger is introduced into the hot water tank, and is heated through the heat storage process for the next defrosting, thereby realizing the reuse of defrosting waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of a large-scale air source heat pump heat exchange system of the present invention, wherein the area indicated by A in the figure represents the indoor space;

[0024] Figure 2 It is a flow chart of a control method for heat exchange and defrosting of a large air source heat pump according to the present invention.

[0025] The names and reference numerals of the components in the above drawings are as follows:

[0026] 1 air heat exchanger, 1-1 first air heat exchanger, 1-2 second air heat exchanger, 2 heat exchange branch, 3 heating circuit, 4 defrost branch, 5 heating branch, 6 heating branch, 7 heat storage branch, 8-1 evaporator, 8-2 compressor, 8-3 condenser, 8-4 throttle valve, 9 regulating valve, 10-1 first solenoid valve, 10-2 second solenoid valve, 10-3 third solenoid valve, 10-4 fourth solenoid valve, 10-5 fifth solenoid valve, 10-6 sixth solenoid valve, 10-7 seventh solenoid valve, 10-8 eighth solenoid valve, 11 intermediate heat exchanger, 12-1 intermediate pump, 12-2 terminal pump, 12-3 defrost pump, 12-4 heat storage pump, 13 cold water tank, 14 hot water tank. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] It should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, terms such as "upper," "lower," "left," and "right" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the system or component described must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for ease of description and should not be construed as indicating or implying relative importance.

[0029] Specific implementation method 1: Figure 1 As shown, this embodiment discloses a large-scale air source heat pump heat exchange system, including a heat exchange branch 2, an evaporator 8-1, a compressor 8-2, a condenser 8-3, a throttle valve 8-4, a regulating valve 9, a heating circuit 3, a heating branch 5, a defrost branch 4, a heating branch 6, a heat storage branch 7, an intermediate heat exchanger 11, a cold water tank 13, a hot water tank 14 and a plurality of air heat exchangers 1;

[0030] Each air heat exchanger 1 is provided with a heat exchange fan, and the inlet and outlet of each air heat exchanger 1 are respectively provided with two branch inlets and two branch outlets, the two branch inlets are respectively the first branch inlet and the second branch inlet, and the two branch outlets are respectively the first branch outlet and the second branch outlet. The first branch inlet and the first branch outlet of each air heat exchanger 1 are connected with the two ends of the heat exchange branch 2 to form a heat exchange circuit; the heat exchange branch 2 is connected with the heating circuit 3 through the evaporator 8-1 (the heat exchange branch 2 can exchange heat with the heating circuit 3 through the evaporator 8-1, so that multiple air heat exchangers 1 can exchange heat with the heating circuit 3 through the heat exchange branch 2), and the heating circuit 3 is connected with the heating branch 5 through the condenser 8-3 (the heating branch 5 exchanges heat with the heating circuit 3 through the condenser 8-3, so as to transfer the heat generated by the heating circuit 3 to the end); the second branch inlet and the second branch outlet of each air heat exchanger 1 are connected with the two ends of one side of the defrost branch 4, and one end of the other side of the defrost branch 4 is divided into two branches and is simultaneously connected to the cold water tank 13 and the hot water tank 13. The inlet of the tank 14 is connected, and the other end of the other side of the defrost branch 4 is also divided into two branches and is connected to the outlets of the cold water tank 13 and the hot water tank 14 at the same time, thereby forming a defrost circuit; the side wall of the hot water tank 14 is connected to the two ends of the heating branch 6 to form a heating circuit; the heating branch 6 is connected to the heat storage branch 7 through the intermediate heat exchanger 11 (the heating branch 6 and the heat storage branch 7 exchange heat through the intermediate heat exchanger 11); the two ends of the heat storage branch 7 are connected to the return water pipe of the heating branch 5, and the two connecting pipes at the two ends of the heat storage branch 7 on the heating branch 5 are connected. A regulating valve 9 is installed between the points (to divert part of the hot water in the heating branch 5 to the heat storage branch 7, so that the hot water tank 14 can exchange heat with the heating branch 5 through the heating branch 6, the intermediate heat exchanger 11, the heat storage branch 7 in sequence); a compressor 8-2 is provided on the heating circuit 3 between the outlet of the evaporator 8-1 and the inlet of the condenser 8-3, and a throttle valve 8-4 is provided on the heating circuit 3 between the outlet of the condenser 8-3 and the inlet of the evaporator 8-1; both ends of the heating branch 5 are connected to the end to form a heating circuit.

[0031] When the heat exchange system operates in heating mode, the refrigerant transfers the low-grade heat source absorbed from the outdoor air by the air heat exchanger 1 to the heating circuit 3 through the heat exchange branch 2. The heating circuit 3 upgrades these low-grade heat sources to a higher grade and then transfers them to the end through the heating branch 5.

[0032] When the heat exchange system stores heat, the hot water tank 14 can take heat from the heating branch 5 through the heating branch 6, the intermediate heat exchanger 11, and the heat storage branch 7 in sequence to heat the refrigerant in the hot water tank 14 and store heat for the defrosting process.

[0033] When the heat exchange system operates in defrost mode, the low-temperature refrigerant in the air heat exchanger 1 enters the cold water tank 13 for storage through the defrost branch 4, and the high-temperature refrigerant in the hot water tank 14 enters the air heat exchanger 1 through the defrost branch 4 for defrosting. The high-temperature refrigerant after defrosting flows back to the hot water tank 14 through the defrost branch 4, and the low-temperature refrigerant in the cold water tank 13 flows back to the air heat exchanger 1 through the defrost branch 4, completing the defrost process.

[0034] Specific implementation method 2: Figure 1 As shown, this embodiment is a further description of the specific embodiment 1, and the air source heat pump heat exchange system further includes a fifth solenoid valve 10-5, a sixth solenoid valve 10-6, a seventh solenoid valve 10-7, an eighth solenoid valve 10-8, multiple first solenoid valves 10-1, multiple second solenoid valves 10-2, multiple third solenoid valves 10-3 and multiple fourth solenoid valves 10-4;

[0035] A first solenoid valve 10-1 is installed at the connection position between the first branch inlet of each air heat exchanger 1 and the heat exchange branch 2, and a second solenoid valve 10-2 is installed at the connection position between the first branch outlet of each air heat exchanger 1 and the heat exchange branch 2; a third solenoid valve 10-3 is installed at the connection position between the second branch inlet of each air heat exchanger 1 and the defrost branch 4, and a fourth solenoid valve 10-4 is installed at the connection position between the second branch outlet of each air heat exchanger 1 and the defrost branch 4;

[0036] The fifth solenoid valve 10-5 is installed at the connection position between the inlet of the cold water tank 13 and the defrost branch 4, the sixth solenoid valve 10-6 is installed at the connection position between the first outlet of the hot water tank 14 and the defrost branch 4, the seventh solenoid valve 10-7 is installed at the connection position between the first inlet of the hot water tank 14 and the defrost branch 4, and the eighth solenoid valve 10-8 is installed at the connection position between the outlet of the cold water tank 13 and the defrost branch 4.

[0037] Specific implementation method three: Figure 1 As shown, this embodiment is a further explanation of specific embodiment one or two, and the air source heat pump heat exchange system also includes four circulation pumps (for promoting fluid flow), which are an intermediate pump 12-1, a terminal pump 12-2, a defrost pump 12-3 and a heat storage pump 12-4; a defrost pump 12-3 is installed on the defrost branch 4 on the refrigerant inlet branch; an intermediate pump 12-1 is installed on the heat exchange branch 2, and the intermediate pump 12-1 is located between the first branch inlet of the air heat exchanger 1 and the evaporator 8-1; a terminal pump 12-2 is installed on the heating pipeline of the heating branch 5; a heat storage pump 12-4 is installed on the heating branch 6, and the heat storage pump 12-4 is arranged between the second outlet of the hot water tank 14 and the intermediate heat exchanger 11.

[0038] Specific implementation method four: Figure 1 and Figure 2As shown, this embodiment discloses a control method for achieving heat exchange and defrosting of a large air source heat pump using the heat exchange system described in any one of the specific embodiments 1 to 3. The method includes the following steps:

[0039] S101: Obtaining the frost condition of the air heat exchanger 1;

[0040] S102: Determine whether the frost condition of the air heat exchanger 1 meets the defrosting standard; if yes, execute step S103; if not, execute step S101 again;

[0041] S103: Disconnect heat exchange branch 2 and connect defrost branch 4, controlling the heat exchange fan of air heat exchanger 1 to stop rotating. The high-temperature refrigerant in hot water tank 14 flows into air heat exchanger 1 through defrost branch 4 for heat exchange. After heat exchange, the refrigerant flows out of air heat exchanger 1 and flows into cold water tank 13 through defrost branch 4.

[0042] S104: When the refrigerant level in the cold water tank 13 reaches a first preset level, the defrost branch 4 is disconnected from the inlet of the cold water tank 13 and the first inlet of the hot water tank 14 is connected. The refrigerant flowing out of the air heat exchanger 1 flows into the hot water tank 14 through the defrost branch 4.

[0043] S105: When the surface temperature of the fins of the air heat exchanger 1 reaches a preset temperature, the heat exchange fan of the air heat exchanger 1 is controlled to rotate;

[0044] S106: After the preset time has elapsed, the connection between the defrost branch 4 and the first outlet of the hot water tank 14 is disconnected, and the outlet of the cold water tank 13 is connected. The low-temperature refrigerant in the cold water tank 13 flows out from the outlet of the cold water tank 13 and flows into the air heat exchanger 1 through the defrost branch 4. The high-temperature refrigerant in the air heat exchanger 1 flows out from the second branch outlet of the air heat exchanger 1 and flows into the hot water tank 14 through the defrost branch 4 and the first inlet of the hot water tank 14.

[0045] S107: When the refrigerant level in the cold water tank 13 reaches a second preset liquid level, the heat exchange branch 2 is connected and the defrost branch 4 is disconnected, ending the defrost cycle of the air heat exchanger 1.

[0046] The defrost mode is: monitoring the liquid level of the cold water tank 13; after the air heat exchanger 1 is connected with the defrost branch 4, the two ends of the other side of the defrost branch 4 are respectively connected to the inlet of the cold water tank 13 and the outlet of the hot water tank 14, so that the low-temperature refrigerant in the air heat exchanger 1 flows into the cold water tank 13, and the high-temperature refrigerant in the hot water tank 14 flows into the air heat exchanger 1; after the refrigerant level in the cold water tank 13 reaches a first preset liquid level, the defrost branch 4 is controlled to disconnect from the inlet of the cold water tank 13 and connect to the inlet of the hot water tank 14, so that the high-temperature refrigerant after defrosting flows back to the hot water tank 14.

[0047] When the fins of the air heat exchanger 1 reach the preset temperature, the heat exchange fan is started; after a preset time, the defrost branch 4 is controlled to disconnect from the outlet of the hot water tank 14 and instead connect to the outlet of the cold water tank, so that the low-temperature refrigerant in the cold water tank 13 flows into the air heat exchanger 1, and the high-temperature refrigerant in the air heat exchanger 1 flows back to the hot water tank 14; after the refrigerant height in the cold water tank 13 reaches the second preset liquid level, the heat exchange branch 2 is connected and the defrost branch 4 is disconnected.

[0048] Example 1:

[0049] This embodiment discloses a large-scale air source heat pump heat exchange system, including a heat exchange branch 2, an evaporator 8-1, a condenser 8-3, a compressor 8-2, a throttle valve 8-4, a regulating valve 9, a heating circuit 3, a heating branch 5, a defrost branch 4, a heating branch 6, a heat storage branch 7, an intermediate heat exchanger 11, a cold water tank 13, a hot water tank 14 and two air heat exchangers 1; the two air heat exchangers 1 are a first air heat exchanger 1-1 and a second air heat exchanger 1-2, and the first air heat exchanger 1-1 and the second air heat exchanger 1-2 are arranged side by side on the left and right; two interfaces are provided below the first air heat exchanger 1-1 and below the second air heat exchanger 1-2, of which the one on the left is an inlet and the one on the right is an outlet, each inlet has two branches, the two branch inlets are a first branch inlet and a second branch inlet, each outlet also has two branches, the two branch outlets are a first branch outlet and a second branch outlet. It should be noted that although the air source heat pump heat exchange system described in this preferred embodiment includes two air heat exchangers 1, technicians can set the specific number of air heat exchangers 1 according to actual use requirements, as long as the number of solenoid valves and the connection relationship between pipelines are adjusted accordingly according to the specific number of air heat exchangers 1 in the application. The present invention does not impose any restrictions on the specific type of air heat exchanger 1. Technicians can set the specific type and structural parameters of the air heat exchanger 1 according to actual use requirements; in addition, the cold water tank 13 and the hot water tank 14 in this embodiment are both open water tanks. Technicians can use all closed water tanks or use one open water tank and one closed water tank according to actual needs. The present invention does not limit the capacity and structure of the water tank. This specific type of change does not deviate from the basic principle of the present invention and falls within the scope of protection of the present invention.

[0050] Furthermore, the two ends of the heat exchange branch 2 are divided into two refrigerants, so that the first air heat exchanger 1-1 and the second air heat exchanger 1-2 can be connected to the heat exchange branch 2 to form a circulation loop; the refrigerant flowing out of the first air heat exchanger 1-1 flows into the heat exchange branch 2 through the second solenoid valve 10-2 at the connection position between the first branch outlet of the first air heat exchanger 1-1 and the heat exchange branch 2, and the refrigerant completes heat exchange with the heating circuit 3 through the evaporator 8-1, and then passes through the heat exchange branch 2, the first branch inlet of the first air heat exchanger 1-1 and the connection position of the heat exchange branch 2. The refrigerant flows into the first air heat exchanger 1-1 through the first solenoid valve 10-1 at the connection position between the first branch outlet of the second air heat exchanger 1-2 and the heat exchange branch 2, and flows into the heat exchange branch 2 through the second solenoid valve 10-2 at the connection position between the first branch outlet of the second air heat exchanger 1-2 and the heat exchange branch 2. The refrigerant completes heat exchange with the heating circuit 3 through the evaporator 8-1, and then flows into the second air heat exchanger 1-2 through the heat exchange branch 2, the first branch inlet of the second air heat exchanger 1-2 and the first solenoid valve 10-1 at the connection position between the heat exchange branch 2, to complete the heat exchange cycle.

[0051] Furthermore, four branches are divided into two ends of the defrost branch 4, so that the first air heat exchanger 1-1, the second air heat exchanger 1-2, the cold water tank 13 and the hot water tank 14 can be connected through the defrost branch 4; the upper right side of the cold water tank 13 is the inlet, and the lower side is the outlet, the upper left side of the hot water tank 14 is the first inlet, and the lower side is the first outlet, and the upper right side of the hot water tank 14 is the second inlet, and the lower side is the second outlet; after the first air heat exchanger 1-1 reaches the defrost condition, the second solenoid valve 10-2 installed at the connecting position of the first branch outlet of the first air heat exchanger 1-1 and the heat exchange branch 2 and the first solenoid valve 10-1 installed at the connecting position of the first branch inlet of the first air heat exchanger 1-1 and the heat exchange branch 2 are closed, and the defrost is turned on. Pump 12-3, open the third solenoid valve 10-3 installed at the connection position between the second branch inlet of the first air heat exchanger 1-1 and the defrost branch 4 and the fourth solenoid valve 10-4 installed at the connection position between the second branch outlet of the first air heat exchanger 1-1 and the defrost branch 4; adjust the sixth solenoid valve 10-6 installed at the connection position between the first outlet of the hot water tank 14 and the defrost branch 4, control the high-temperature refrigerant in the hot water tank 14 to flow into the defrost branch 4 through the first outlet of the hot water tank 14 and the sixth solenoid valve 10-6, and then flow into the first air heat exchanger 1-1 through the third solenoid valve 10-3 installed at the connection position between the second branch inlet of the first air heat exchanger 1-1 and the defrost branch 4, and the refrigerant in the first air heat exchanger 1-1 After internal heat exchange, the refrigerant flows into the defrost branch 4 through the second branch outlet of the first air heat exchanger 1-1 and the fourth solenoid valve 10-4 installed at the connecting position between the second branch outlet of the first air heat exchanger 1-1 and the defrost branch 4, and then flows into the cold water tank 13 through the fifth solenoid valve 10-5; when the liquid level in the cold water tank 13 reaches the first preset liquid level, the fifth solenoid valve 10-5 is cut off, and the seventh solenoid valve 10-7 is opened. The refrigerant flowing out of the second branch outlet of the first air heat exchanger 1-1 flows into the hot water tank 14 through the fourth solenoid valve 10-4 installed at the connecting position between the second branch outlet of the first air heat exchanger 1-1 and the defrost branch 4, the defrost branch 4, the seventh solenoid valve 10-7 and the first inlet of the hot water tank 14, completing the defrost cycle. ring; after the preset time is reached, the sixth solenoid valve 10-6 is closed and the eighth solenoid valve 10-8 is opened, and the low-temperature refrigerant in the cold water tank 13 flows out from the outlet of the cold water tank 13, passes through the eighth solenoid valve 10-8, the defrost branch 4, and the third solenoid valve 10-3 installed at the connecting position of the second branch inlet of the first air heat exchanger 1-1 and the defrost branch 4, and flows into the first air heat exchanger 1-1; the high-temperature refrigerant in the first air heat exchanger 1-1 flows out from the second branch outlet of the first air heat exchanger 1-1, passes through the fourth solenoid valve 10-4 installed at the connecting position of the second branch outlet of the first air heat exchanger 1-1 and the defrost branch 4, the defrost branch 4, the seventh solenoid valve 10-7 and the first inlet of the hot water tank 14, and flows into the hot water tank 14;When the liquid level in the cold water tank 13 reaches the second preset level, the defrost pump 12-3, the third solenoid valve 10-3 installed at the connection point between the second branch inlet of the first air heat exchanger 1-1 and the defrost branch 4, and the fourth solenoid valve 10-4 installed at the connection point between the second branch outlet of the first air heat exchanger 1-1 and the defrost branch 4 are closed, ending the defrost cycle of the first air heat exchanger 1-1.

[0052] After the second air heat exchanger 1-2 reaches the defrost condition, the second solenoid valve 10-2 installed at the connection position between the first branch outlet of the second air heat exchanger 1-2 and the heat exchange branch 2 and the first solenoid valve 10-1 installed at the connection position between the first branch inlet of the second air heat exchanger 1-2 and the heat exchange branch 2 are closed, the defrost pump 12-3, the third solenoid valve 10-3 installed at the connection position between the second branch inlet of the second air heat exchanger 1-2 and the defrost branch 4 and the fourth solenoid valve 10-4 installed at the connection position between the second branch outlet of the second air heat exchanger 1-2 and the defrost branch 4 are opened, the sixth solenoid valve 10-6 and the fifth solenoid valve 10-5 are opened, and the high-temperature refrigerant in the hot water tank 14 passes through the hot water tank 14. The refrigerant flows into the defrost branch 4 through the first outlet and the sixth solenoid valve 10-6, and then flows into the second air heat exchanger 1-2 through the third solenoid valve 10-3 installed at the connecting position between the second branch inlet of the second air heat exchanger 1-2 and the defrost branch 4. After heat exchange in the second air heat exchanger 1-2, the refrigerant flows into the defrost branch 4 through the second branch outlet of the second air heat exchanger 1-2 and the fourth solenoid valve 10-4 installed at the connecting position between the second branch outlet of the second air heat exchanger 1-2 and the defrost branch 4, and then flows into the cold water tank 13 through the fifth solenoid valve 10-5. When the liquid level in the cold water tank 13 reaches the first preset liquid level, the fifth solenoid valve 10-5 is cut off, the seventh solenoid valve 10-7 is opened, and the refrigerant flows into the second branch outlet of the second air heat exchanger 1-2 from the second branch outlet of the second air heat exchanger 1-2. The refrigerant flowing out of the branch outlet flows into the hot water tank 14 through the fourth solenoid valve 10-4, the defrost branch 4, the seventh solenoid valve 10-7 and the first inlet of the hot water tank 14 installed at the connecting position of the second branch outlet of the second air heat exchanger 1-2 and the defrost branch 4, completing the defrost cycle; after the preset time, the sixth solenoid valve 10-6 is closed and the eighth solenoid valve 10-8 is opened, and the low-temperature refrigerant in the cold water tank 13 flows out from the outlet of the cold water tank 13, flows into the second air heat exchanger 1-2 through the eighth solenoid valve 10-8, the defrost branch 4, the third solenoid valve 10-3 installed at the connecting position of the second branch inlet of the second air heat exchanger 1-2 and the defrost branch 4, and the second branch inlet of the second air heat exchanger 1-2, and the second air heat exchanger 1-2 is turned on. The high-temperature refrigerant in the heat exchanger 1-2 flows out from the second branch outlet of the second air heat exchanger 1-2, passes through the fourth solenoid valve 10-4 installed at the connecting position between the second branch outlet of the second air heat exchanger 1-2 and the defrost branch 4, the defrost branch 4 and the seventh solenoid valve 10-7, and then flows into the hot water tank 14 from the first inlet of the hot water tank 14. When the liquid level in the cold water tank 13 reaches the second preset liquid level, the defrost pump 12-3, the third solenoid valve 10-3 installed at the connecting position between the second branch inlet of the second air heat exchanger 1-2 and the defrost branch 4, and the fourth solenoid valve 10-4 installed at the connecting position between the second branch outlet of the second air heat exchanger 1-2 and the defrost branch 4 are closed to end the defrost cycle of the second air heat exchanger 1-2.

[0053] Those skilled in the art will understand that although the air source heat pump system in this preferred embodiment controls the connection between the two air heat exchangers 1 and the heating branch 2 and the defrost branch 4 through multiple solenoid valves, this setting is not restrictive, and technicians can set the specific connection method according to actual usage requirements; for example, the air heat exchanger 1 can also be connected to the cold water tank 13 and the hot water tank 14 through independent pipes respectively, and a circulating water pump and a check valve are provided on the water outlet pipe of each water tank, and a solenoid valve is provided on the water inlet pipe. The refrigerant exchange is achieved by controlling the start and stop of the circulating water pump and the opening and closing of the solenoid valve. These specific structural changes do not deviate from the basic principles of the present invention and fall within the scope of protection of the present invention.

[0054] Furthermore, the second inlet and second outlet of the hot water tank 14 are connected to the two ends of the heating branch 6, and the two ends of the heat storage branch 7 are simultaneously connected to the return pipe of the heating branch 5. A regulating valve 9 is installed between the two connection points to play a diversion role; the refrigerant flows into the heating branch 6 from the second outlet at the lower right of the hot water tank 14, and flows into the intermediate heat exchanger 11 through the heating branch 6 for heat exchange, and then flows back to the hot water tank 14 through the second inlet at the upper right of the hot water tank 14; the terminal return water flows back to the condenser 8-3 through the heating branch 5 for heat exchange with the heating circuit 3. Due to the obstruction of the throttle valve 8-4, part of the return water is diverted to the heat storage branch 7. This part of the return water flows into the intermediate heat exchanger 11 through the heat storage branch 7 to heat the refrigerant, and the return water after heat exchange flows back to the heating branch 5 through the heat storage branch 7.

[0055] In addition, an intermediate pump 12-1 is installed on the heating branch 2 of the air source heat pump heat exchange system, a terminal pump 12-2 is installed on the heating branch 5, a heat storage pump 12-4 is installed on the heating branch 6, and a defrost pump 12-3 is installed on the defrost branch 4. The air source heat pump heat exchange system can control the flow of liquid with the help of these circulation pumps. Of course, technicians can set the power source of the fluid flow according to actual use requirements. As a preferred embodiment, the first air heat exchanger 1-1 and the second air heat exchanger 1-2 are provided with heat exchange fans. The first air heat exchanger 1-1 and the second air heat exchanger 1-2 can accelerate the air circulation speed on the surface of the air heat exchanger through their respective heat exchange fans. This embodiment does not limit the type and specifications of the fans. Technicians can select the specific type of heat exchange fans according to actual use requirements.

[0056] Furthermore, the air source heat pump heat exchange system also includes a controller, which can obtain the frost conditions of the first air heat exchanger 1-1 and the second air heat exchanger 1-2 and the liquid level height in the cold water tank 13. The specific acquisition method is not restrictive and can be achieved with the help of various sensors; and the controller can also control the operation of the air source heat pump heat exchange system, for example, controlling the action of the solenoid valve, controlling the operation of the heat exchange fan, controlling the start and stop of the water pump, etc. In addition, it can be understood by those skilled in the art that the present invention does not impose any restrictions on the specific structure and model of the controller, and the controller can be the original controller of the air source heat pump heat exchange system, or it can be a controller separately set for executing the defrost control method of the present invention. The technicians can set the structure and model of the controller according to actual use requirements.

[0057] In order to obtain the frost condition and the liquid level, a temperature sensor is provided in the air heat exchanger, and a liquid level sensor is provided in the cold water tank 13. The controller is connected to the temperature sensor and the liquid level sensor respectively.

[0058] Example 2:

[0059] This embodiment discloses a defrost control method for a large air source heat pump heat exchange system. The method is implemented using the large air source heat pump heat exchange system and includes the following steps:

[0060] S101: Obtaining the frost condition of the air heat exchanger 1;

[0061] S102: Determine whether the frost condition of the air heat exchanger 1 meets the defrosting standard; if yes, execute step S103; if not, execute step S101 again;

[0062] S103: disconnect the heat exchange branch 2 and connect the defrost branch 4, and control the heat exchange fan of the air heat exchanger 1 to stop rotating;

[0063] S104: When the cold water tank 13 reaches a first preset liquid level, the defrost branch 4 is disconnected from the inlet of the cold water tank 13 and the first inlet of the hot water tank 14 is connected;

[0064] S105: When the surface temperature of the fins of the air heat exchanger 1 reaches a preset temperature, the heat exchange fan is controlled to rotate;

[0065] S106: After a preset time, disconnect the defrost branch 4 from the first outlet of the hot water tank 14 and connect the outlet of the cold water tank 13;

[0066] S107: When the cold water tank 13 reaches the second preset liquid level, the heat exchange branch 2 is connected and the defrost branch 4 is disconnected.

[0067] Furthermore, in step S101, the controller can obtain the frost conditions of the first air heat exchanger 1-1 and the second air heat exchanger 1-2; it should be noted that the present invention does not impose any restrictions on this specific acquisition method, and technicians can set their own acquisition methods according to actual use requirements. For example, the frost conditions can be determined by monitoring the changes in the internal and external pressure difference of the air heat exchanger 1 or the ring fin temperature difference. Then, in step S102, the controller can determine whether the frost conditions of the first air heat exchanger 1-1 and the second air heat exchanger 1-2 meet the defrost standard; it should be noted that the defrost standard needs to be set according to actual use requirements. Such changes in specific standards do not deviate from the basic principles of the present invention and fall within the scope of protection of the present invention. Based on the judgment result of step S102, if the frost condition of the air heat exchanger 1 does not meet the defrost standard, step S101 is executed again for real-time monitoring; if the frost condition of the air heat exchanger 1 meets the defrost standard, step S103 is started.

[0068] Specifically, the steps of executing step S103 include: disconnecting the heat exchange branch 2 and connecting the defrost branch 4, and controlling the heat exchange fan to stop rotating. When the frost condition of the air heat exchanger reaches the defrost standard, the controller controls the corresponding solenoid valve to operate so that the corresponding air heat exchanger is disconnected from the heat exchange branch 2 and connected to the defrost branch 4. At this time, the controller controls the defrost pump 12-3 to turn on, and at the same time controls the heat exchange fan of the corresponding air heat exchanger to stop rotating. The high-temperature refrigerant in the hot water tank 14 flows into the corresponding air heat exchanger through the defrost branch 4 to melt the frost layer on the surface of the air heat exchanger. The low-temperature refrigerant in the corresponding air heat exchanger flows into the cold water tank 13 through the defrost branch 4 for storage. It should be noted that the present invention does not impose any restrictions on the specific execution order of disconnecting the heat exchange branch 2, connecting the defrost branch 4, and controlling the heat exchange fan to stop rotating. The technicians can set the specific execution order of each step according to actual use requirements. When the liquid level in the cold water tank 13 reaches the first preset level, step S104 is executed, and the controller controls the corresponding solenoid valve to disconnect the defrost branch 4 from the inlet of the cold water tank 13 and connect the first inlet of the hot water tank 14. The refrigerant in the corresponding air heat exchanger, which still has a relatively high temperature after defrosting, flows back into the hot water tank 14. The present invention does not impose any numerical restrictions on the height of the first liquid level in the cold water tank 13, and technicians can set it according to actual usage requirements. Preferably, the first liquid level is the liquid level corresponding to when the cold water tank 13 stores all the low-temperature refrigerant in the corresponding air heat exchanger and the corresponding connecting pipelines.

[0069] Furthermore, in step S105, when the surface temperature of the fins of the corresponding air heat exchanger 1 reaches the preset temperature, the controller controls the heat exchange fan to rotate. It should be noted that the present invention does not impose any restrictions on the specific value of the preset temperature. The technician can set it according to actual use requirements. Preferably, the preset temperature is 10°C. Then, in step S106, after the preset time, the controller controls the sixth solenoid valve 10-6 to operate to disconnect the defrost branch 4 from the first outlet of the hot water tank 14, and connect the outlet of the cold water tank 13 (the outlet of the cold water tank 13 and the inlet of the hot water tank 14 are connected at the same time at this time). The low-temperature refrigerant in the cold water tank 13 flows into the corresponding air heat exchanger 1, and the refrigerant in the corresponding air heat exchanger 1 that still has a higher temperature is pushed back to the hot water tank 14. Next, when the liquid level in the cold water tank 13 reaches a second preset level, the controller controls the first solenoid valve 10-1, the second solenoid valve 10-2, the third solenoid valve 10-3, and the fourth solenoid valve 10-4 to operate, thereby connecting the heat exchange branch 2 and disconnecting the defrost branch 4. At this time, the controller controls the defrost pump 12-3 to shut down, and the air heat exchanger 1 continues to exchange heat with the heating circuit 3 through the heat exchange branch 2, thereby promptly ensuring the user's heat exchange needs after the defrost is completed. It should be noted that the present invention does not impose any restrictions on the specific value of the preset time, and technicians can set it according to actual usage requirements. Preferably, the preset time is 3 minutes. The present invention also does not impose any restrictions on the specific value of the second preset liquid level. Preferably, the second preset liquid level is the lowest point of the refrigerant liquid level allowed by the cold water tank 13. In addition, those skilled in the art will understand that although time and temperature are used as the basis for determining when to switch to and exit the defrost mode in this preferred embodiment, technicians can obviously also use other parameters to determine the timing of switching to and exiting the defrost mode, such as the internal and external pressure difference of the air heat exchanger.

[0070] Finally, it should be noted that the above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art may, when actually using the present invention, appropriately add or delete some steps, or change the order of different steps as needed. Such changes do not exceed the basic principles of the present invention and are within the scope of protection of the present invention.

[0071] Thus far, the technical solutions of the present invention have been described in conjunction with the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A large air source heat pump heat exchange system, characterized by: It includes a heat exchange branch (2), an evaporator (8-1), a compressor (8-2), a condenser (8-3), a throttle valve (8-4), a regulating valve (9), a heating circuit (3), a heating branch (5), a defrosting branch (4), a heating branch (6), a heat storage branch (7), an intermediate heat exchanger (11), a cold water tank (13), a hot water tank (14) and a plurality of air heat exchangers (1); The inlet and outlet of each air heat exchanger (1) are respectively provided with two branch inlets and two branch outlets, the two branch inlets are respectively a first branch inlet and a second branch inlet, and the two branch outlets are respectively a first branch outlet and a second branch outlet. The first branch inlet and the first branch outlet of each air heat exchanger (1) are connected with both ends of the heat exchange branch (2) to form a heat exchange circuit; the heat exchange branch (2) is connected with the heating circuit (3) through the evaporator (8-1), and the heating circuit (3) is connected with the heating branch (5) through the condenser (8-3); the second branch inlet and the second branch outlet of each air heat exchanger (1) are connected with both ends of one side of the defrost branch (4), and one end of the other side of the defrost branch (4) is divided into two branches and is simultaneously connected with the inlet of the cold water tank (13) and the inlet of the hot water tank (14 ), the other end of the defrost branch (4) on the other side is also divided into two branches and is simultaneously connected to the outlet of the cold water tank (13) and the first outlet of the hot water tank (14), thereby forming a defrost circuit; the side wall of the hot water tank (14) is connected to both ends of the heating branch (6), thereby forming a heating circuit; the heating branch (6) is connected to the heat storage branch (7) through the intermediate heat exchanger (11); both ends of the heat storage branch (7) are connected to the return water pipeline of the heating branch (5), and a regulating valve (9) is installed between the two connection points on the heating branch (5) at both ends of the heat storage branch (7); a compressor (8-2) is installed on the outgoing pipeline of the heating circuit (3), and a throttle valve (8-4) is installed on the return pipeline of the heating circuit (3); both ends of the heating branch (5) are connected to the end to form a heating circuit; The air source heat pump heat exchange system further comprises a fifth solenoid valve (10-5), a sixth solenoid valve (10-6), a seventh solenoid valve (10-7), an eighth solenoid valve (10-8), a plurality of first solenoid valves (10-1), a plurality of second solenoid valves (10-2), a plurality of third solenoid valves (10-3) and a plurality of fourth solenoid valves (10-4); A first solenoid valve (10-1) is installed at a position where the first branch inlet of each air heat exchanger (1) communicates with the heat exchange branch (2), and a second solenoid valve (10-2) is installed at a position where the first branch outlet of each air heat exchanger (1) communicates with the heat exchange branch (2); a third solenoid valve (10-3) is installed at a position where the second branch inlet of each air heat exchanger (1) communicates with the defrost branch (4), and a fourth solenoid valve (10-4) is installed at a position where the second branch outlet of each air heat exchanger (1) communicates with the defrost branch (4); A fifth solenoid valve (10-5) is installed at a connection position between the cold water tank (13) inlet and the defrost branch (4), a sixth solenoid valve (10-6) is installed at a connection position between the first outlet of the hot water tank (14) and the defrost branch (4), a seventh solenoid valve (10-7) is installed at a connection position between the first inlet of the hot water tank (14) and the defrost branch (4), and an eighth solenoid valve (10-8) is installed at a connection position between the cold water tank (13) outlet and the defrost branch (4).

2. A large-scale air source heat pump heat exchange system according to claim 1, characterized in that: The air source heat pump heat exchange system further includes four circulation pumps, which are an intermediate pump (12-1), a terminal pump (12-2), a defrost pump (12-3) and a heat storage pump (12-4); the defrost pump (12-3) is installed on the defrost branch (4) and is located on the refrigerant inlet branch; the intermediate pump (12-1) is installed on the heat exchange branch (2), and the intermediate pump (12-1) is located between the first branch inlet of the air heat exchanger (1) and the evaporator (8-1); the terminal pump (12-2) is installed on the heating pipe of the heating branch (5); and the heat storage pump (12-4) is installed on the heating branch (6), and the heat storage pump (12-4) is arranged between the second outlet of the hot water tank (14) and the intermediate heat exchanger (11).

3. A control method for achieving heat exchange defrosting of a large air source heat pump using the heat exchange system according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: S101: Obtaining the frost condition of the air heat exchanger (1); S102: Determine whether the frost condition of the air heat exchanger (1) meets the defrosting standard; if yes, execute step S103; if not, execute step S101 again; S103: disconnect the heat exchange branch (2) and connect the defrost branch (4), control the heat exchange fan of the air heat exchanger (1) to stop rotating, and the high-temperature refrigerant in the hot water tank (14) flows into the air heat exchanger (1) through the defrost branch (4) for heat exchange. The refrigerant after heat exchange flows out of the air heat exchanger (1) and flows into the cold water tank (13) through the defrost branch (4); S104: When the refrigerant level in the cold water tank (13) reaches a first preset liquid level, the connection between the defrost branch (4) and the inlet of the cold water tank (13) is disconnected, and the first inlet of the hot water tank (14) is connected, so that the refrigerant flowing out of the air heat exchanger (1) flows into the hot water tank (14) through the defrost branch (4); S105: When the surface temperature of the fins of the air heat exchanger (1) reaches a preset temperature, the heat exchange fan of the air heat exchanger (1) is controlled to rotate; S106: After the preset time is reached, the connection between the defrost branch (4) and the first outlet of the hot water tank (14) is disconnected, and the outlet of the cold water tank (13) is connected, and the low-temperature refrigerant in the cold water tank (13) flows out from the outlet of the cold water tank (13) and flows into the air heat exchanger (1) through the defrost branch (4); the high-temperature refrigerant in the air heat exchanger (1) flows out from the second branch outlet of the air heat exchanger (1) and flows into the hot water tank (14) through the defrost branch (4) and the first inlet of the hot water tank (14); S107: When the refrigerant level in the cold water tank (13) reaches a second preset liquid level, the heat exchange branch (2) is connected and the defrost branch (4) is disconnected, thereby ending the defrost cycle of the air heat exchanger (1).

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