An air source heat pump system and a defrosting control method thereof

Abstract

The application belongs to the technical field of heat pump systems, and discloses an air source heat pump system and a defrosting control method thereof. The system comprises a circulating loop formed by a compressor, a four-way valve, an indoor heat exchanger, an electronic expansion valve and an outdoor heat exchanger, and further comprises a first bypass, a second bypass, a bypass valve and a solenoid valve. The first end of the first bypass is connected between the four-way valve and the indoor heat exchanger, and the second end is connected between the electronic expansion valve and the outdoor heat exchanger. The first end of the second bypass is connected between the indoor heat exchanger and the electronic expansion valve, and the second end is connected between the outdoor heat exchanger and the four-way valve. The first bypass and the second bypass are respectively provided with a first bypass valve and a second bypass valve, and the solenoid valve is arranged between the first end of the first bypass and the indoor heat exchanger. In the defrosting mode, the first bypass valve and the second bypass valve are opened, the solenoid valve and the electronic expansion valve are closed, and the four-way valve is not reversed. In this way, heat is not taken from the indoor in the defrosting process, the refrigerant of the compressor is effectively supplemented, and the defrosting speed is accelerated.

Description

Technical Field

[0001] This invention belongs to the technical field of heat pump systems, and more specifically, relates to an air source heat pump system and its defrosting control method. Background Technology

[0002] When the surface temperature of the outdoor heat exchanger of an air source heat pump is below both the dew point of the moist air and 0°C, frost will form, leading to a decrease in the performance of the air source heat pump system. This is because the frost layer increases the thermal resistance on the outdoor heat exchanger and also increases the airflow resistance within the heat exchanger, reducing airflow and thus weakening heat exchange.

[0003] In existing technologies, the most commonly used solutions for defrosting outdoor heat exchangers are reverse cycle defrosting and hot gas bypass defrosting. Reverse cycle defrosting requires absorbing heat from the indoor unit, significantly impacting indoor comfort. Hot gas bypass defrosting involves diverting part or all of the compressor's exhaust to the outdoor heat exchanger for defrosting. When some of the compressor's exhaust is diverted to the outdoor heat exchanger during defrosting, some refrigerant flows into the indoor heat exchanger for indoor heating, reducing the heat supply for defrosting and resulting in poor defrosting performance. When all the compressor's exhaust is diverted to the outdoor heat exchanger during defrosting, but the refrigerant stored in the indoor heat exchanger and receiver-of-liquids (if any) is not used to replenish the refrigerant circulating in the system during defrosting, the amount of refrigerant circulating in the system decreases, leading to poor defrosting performance. Furthermore, as the defrosting process progresses, the refrigerant flow rate decreases, resulting in reduced compressor power, slower defrosting speed, and unsatisfactory defrosting effect. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides an air source heat pump system and its defrosting control method, which solves the problems of slow defrosting speed and unsatisfactory defrosting effect of existing defrosting solutions for outdoor heat exchangers.

[0005] To achieve the above objectives, according to one aspect of the present invention, an air source heat pump system is provided, comprising a heat pump circulation loop formed by connecting a compressor, a four-way valve, an indoor heat exchanger, an electronic expansion valve, and an outdoor heat exchanger, and further comprising a first bypass, a second bypass, a bypass valve, and a solenoid valve. The first bypass has a first end connected to a pipeline between the four-way valve and the indoor heat exchanger, and a second end connected to a pipeline between the electronic expansion valve and the outdoor heat exchanger. The second bypass has a first end connected to a pipeline between the indoor heat exchanger and the electronic expansion valve, and a second end connected to a pipeline between the outdoor heat exchanger and the four-way valve. The first bypass is provided with a first bypass valve, and the second bypass is provided with a second bypass valve. The solenoid valve is located between the first end of the first bypass and the indoor heat exchanger. During defrosting, the first and second bypass valves on the first and second bypasses are open, the solenoid valve and the electronic expansion valve are closed, and the four-way valve does not reverse.

[0006] According to the air source heat pump system provided by the present invention, the first port of the four-way valve is connected to the exhaust port of the compressor, the second port of the four-way valve is connected to the first end of the indoor heat exchanger, the third port of the four-way valve is connected to the intake port of the compressor, the second end of the indoor heat exchanger is connected to the electronic expansion valve, the electronic expansion valve is connected to the first end of the outdoor heat exchanger, and the second end of the outdoor heat exchanger is connected to the fourth port of the four-way valve.

[0007] According to the air source heat pump system provided by the present invention, the air intake of the compressor is further connected to a gas-liquid separator; a liquid storage tank is further provided between the indoor heat exchanger and the electronic expansion valve, and correspondingly, the first end of the second bypass is connected to the pipeline between the liquid storage tank and the electronic expansion valve.

[0008] According to the air source heat pump system provided by the present invention, the indoor heat exchanger is further provided with an electric heating device and an indoor fan, and the outdoor heat exchanger is further provided with an outdoor fan.

[0009] According to the air source heat pump system provided by the present invention, the first bypass valve and the second bypass valve are solenoid valves.

[0010] According to another aspect of the present invention, a defrosting control method for an air source heat pump system is provided, the defrosting control method comprising:

[0011] When the air source heat pump system operates in defrost mode, the first bypass valve and the second bypass valve on the first bypass and the second bypass are opened, while the solenoid valve and the electronic expansion valve are closed for defrosting. The four-way valve does not switch directions, the compressor exhaust does not pass through the indoor heat exchanger, and the compressor exhaust does not release heat into the room.

[0012] According to the defrosting control method for an air source heat pump system provided by the present invention, an indoor fan is further provided at the indoor heat exchanger, and an outdoor fan is further provided at the outdoor heat exchanger. The defrosting control method further includes:

[0013] During defrosting, control the indoor fan to reduce its speed and control the outdoor fan to shut down.

[0014] According to the defrosting control method for an air source heat pump system provided by the present invention, an electric heating device is further provided at the indoor heat exchanger, and the defrosting control method further includes:

[0015] Turn on the electric heating device during defrosting to maintain the indoor temperature.

[0016] The defrosting control method for an air source heat pump system provided by the present invention further includes:

[0017] When defrosting is complete, the solenoid valve and the electronic expansion valve are opened, and the first bypass valve and the second bypass valve on the first bypass and the second bypass are closed, so that the air source heat pump system resumes heating mode.

[0018] In summary, compared with the prior art, the air source heat pump system and its defrosting control method provided by this invention offer the following advantages:

[0019] 1. The air source heat pump system achieves defrosting by setting a first bypass. During defrosting, the first bypass valve on the first bypass is opened, while the solenoid valve and electronic expansion valve are closed. During defrosting, the four-way valve does not switch, the compressor exhaust does not pass through the indoor heat exchanger, and the compressor exhaust does not release heat into the room. The system has small pressure fluctuations, which can reduce the time for the system to re-achieve pressure balance, improve efficiency, and eliminate noise caused by the four-way valve switching. Furthermore, it does not extract heat from the room during defrosting, which helps maintain indoor comfort. At the same time, this system is equipped with a second bypass. During defrosting, the second bypass valve on the second bypass is opened, which can effectively replenish the refrigerant in the compressor. Compared with hot gas bypass defrosting, this increases the refrigerant flow, improves the compressor power, and results in faster and better defrosting.

[0020] 2. During defrosting, the electric heater is turned on to ensure indoor heating;

[0021] 3. This invention only adds a small number of pipelines and valves, has a simple structure, low modification cost, and has little impact on the unit size. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the air source heat pump system provided by the present invention;

[0023] Figure 2This is a schematic diagram of the refrigerant flow direction in the heating mode of the air source heat pump system provided by the present invention;

[0024] Figure 3 This is a schematic diagram of the refrigerant flow direction in the defrosting mode of the air source heat pump system provided by the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Please see Figure 1 The present invention provides an air source heat pump system, which includes a heat pump circulation loop formed by connecting a compressor, a four-way valve, an indoor heat exchanger, an electronic expansion valve and an outdoor heat exchanger. The heat pump circulation loop can be switched between cooling mode and heating mode by switching the four-way valve.

[0027] The air source heat pump system also includes a first bypass, a second bypass, and a solenoid valve. The first bypass has a first end connected to the pipe between the four-way valve and the indoor heat exchanger, and a second end connected to the pipe between the electronic expansion valve and the outdoor heat exchanger. The second bypass has a first end connected to the pipe between the indoor heat exchanger and the electronic expansion valve, and a second end connected to the pipe between the outdoor heat exchanger and the four-way valve. Both the first and second bypasses are equipped with bypass valves. The solenoid valve is located between the first end of the first bypass and the indoor heat exchanger. The first and second bypass valves on the first and second bypasses open during defrosting, while the solenoid valve and the electronic expansion valve close during defrosting. The four-way valve does not reverse direction, and the compressor exhaust does not pass through the indoor heat exchanger; therefore, the compressor exhaust does not release heat into the room.

[0028] In this embodiment, the first bypass valve on the first bypass is opened during defrosting, while the solenoid valve and electronic expansion valve are closed. This allows all the high-temperature refrigerant discharged from the compressor outlet to flow into the outdoor heat exchanger through the first bypass, thus defrosting the outdoor heat exchanger and improving the defrosting speed. At the same time, the high-temperature refrigerant stored in the indoor heat exchanger helps maintain the indoor temperature and comfort.

[0029] Furthermore, this embodiment considers that in existing hot gas bypass defrosting systems, when part of the compressor's exhaust is bypassed to the outdoor heat exchanger during defrosting, some refrigerant flows into the indoor heat exchanger for indoor heating, reducing the heat supply for defrosting and worsening the defrosting effect. Conversely, when all the compressor's exhaust is bypassed to the outdoor heat exchanger during defrosting, but the refrigerant stored in the indoor heat exchanger and receiver-of-liquids (if any) is not used to replenish the refrigerant circulating in the system during defrosting, the amount of refrigerant circulating in the system decreases, resulting in a poor defrosting effect. Moreover, as the defrosting process progresses, the refrigerant flow rate for outdoor defrosting decreases due to condensation in the outdoor heat exchanger, leading to very limited defrosting effect and a slow defrosting speed in the later stages of defrosting. Based on this, this embodiment further proposes to set up a second bypass on the basis of closing the solenoid valve and the electronic expansion valve. During defrosting, the second bypass valve on the second bypass is opened, so that the high-temperature and high-pressure refrigerant flowing out of the indoor heat exchanger flows through the second bypass and mixes with the refrigerant flowing out of the outdoor heat exchanger. This replenishes the refrigerant in the circuit, increases the compressor power, and thus helps to speed up the defrosting speed and improve the defrosting efficiency.

[0030] Specifically, the first port of the four-way valve is connected to the exhaust port of the compressor, the second port of the four-way valve is connected to the first end of the indoor heat exchanger, the third port of the four-way valve is connected to the intake port of the compressor, the second end of the indoor heat exchanger is connected to the electronic expansion valve, the electronic expansion valve is connected to the first end of the outdoor heat exchanger, and the second end of the outdoor heat exchanger is connected to the fourth port of the four-way valve.

[0031] Furthermore, a gas-liquid separator is also connected to the compressor's suction port. A liquid storage tank is also provided between the indoor heat exchanger and the electronic expansion valve. This constitutes a defrosting system formed by the first bypass, the second bypass, and the solenoid valve, as provided in this embodiment. This system is suitable for both heat pump circulation loops without and with a liquid storage tank. Correspondingly, when a liquid storage tank is provided, the first end of the second bypass is connected to the pipeline between the liquid storage tank and the electronic expansion valve.

[0032] Furthermore, the indoor heat exchanger is also equipped with an electric heating device and an indoor fan, and the outdoor heat exchanger is also equipped with an outdoor fan.

[0033] Specifically, the bypass valve is a solenoid valve.

[0034] This embodiment also provides a defrosting control method for an air source heat pump system. This defrosting control method is based on the air source heat pump system described in any of the above embodiments, and includes:

[0035] When the air source heat pump system operates in defrost mode, the first and second bypass valves on the first and second bypasses are opened, while the solenoid valve and the electronic expansion valve are closed for defrosting. The four-way valve is kept in a fixed position, preventing the compressor exhaust from passing through the indoor heat exchanger and preventing the compressor exhaust from releasing heat into the room.

[0036] Furthermore, an indoor fan is also provided at the indoor heat exchanger, and an outdoor fan is also provided at the outdoor heat exchanger. The defrosting control method further includes:

[0037] During defrosting, reduce the indoor fan speed appropriately and turn off the outdoor fan. Reducing the indoor fan speed helps maintain the indoor temperature for comfort, while turning off the outdoor fan reduces heat exchange between the refrigerant and the outdoor air, thus allowing for fuller utilization of the refrigerant's temperature during defrosting.

[0038] Furthermore, the indoor heat exchanger is also equipped with an electric heating device, and the defrosting control method further includes:

[0039] Turn on the electric heating device during defrosting to maintain the indoor temperature.

[0040] Furthermore, defrosting control methods also include:

[0041] When defrosting is complete, the solenoid valve and the electronic expansion valve are opened, and the first bypass valve on the first bypass and the second bypass valve on the second bypass are closed, so that the air source heat pump system resumes heating mode.

[0042] like Figure 1 As shown, this system consists of a compressor, a four-way valve, an indoor heat exchanger, a liquid receiver (optional), an electronic expansion valve, a solenoid valve, two bypass valves, an outdoor heat exchanger, a gas-liquid separator, and an electric heating device. Compared to traditional refrigeration systems, this system adds two bypasses with bypass valves. Both bypasses operate in defrost mode: the first bypass connects the indoor heat exchanger and the four-way valve at one end, and the outdoor heat exchanger and the electronic expansion valve at the other end; the second bypass connects the liquid receiver (or the indoor heat exchanger if there is no liquid receiver) and the electronic expansion valve at one end, and the outdoor heat exchanger and the four-way valve at the other end. This system also adds a solenoid valve to the main circuit, located between the indoor heat exchanger and the first end of the first bypass, to prevent refrigerant from passing through the indoor heat exchanger during defrost. Additionally, an electric heating device is installed at the indoor heat exchanger for heating during defrost.

[0043] like Figure 2As shown, in heating mode, the solenoid valve and electronic expansion valve are open, while the first bypass valve and the second bypass valve are closed. After being compressed by the compressor, the refrigerant flows into the indoor heat exchanger through the four-way valve to release heat and provide heating. After being throttled by the electronic expansion valve, it is cooled and depressurized, then flows into the outdoor heat exchanger to absorb heat and condense. Finally, it flows back to the compressor through the four-way valve and the gas-liquid separator.

[0044] like Figure 3 As shown, in defrost mode, the first and second bypass valves are open, the solenoid valve and electronic expansion valve are closed, the outdoor fan is off, the indoor fan speed is reduced, and the four-way valve does not switch directions. During defrost, the refrigerant is compressed by the compressor and flows into the first bypass through the four-way valve. After passing through the first bypass valve, it reaches the outdoor heat exchanger to release heat and defrost, and then flows back to the compressor through the four-way valve and the gas-liquid separator. At the same time, the high-temperature and high-pressure refrigerant stored in the indoor heat exchanger and the liquid receiver (if any) flows to the outdoor heat exchanger outlet through the second bypass valve on the second bypass, effectively replenishing the refrigerant and accelerating the defrosting speed.

[0045] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A defrosting control method of an air source heat pump system, characterized by, The system includes a heat pump circulation loop formed by connecting a compressor, a four-way valve, an indoor heat exchanger, an electronic expansion valve, and an outdoor heat exchanger. It also includes a first bypass, a second bypass, a bypass valve, and a solenoid valve. The first end of the first bypass is connected to the pipeline between the four-way valve and the indoor heat exchanger, and the second end is connected to the pipeline between the electronic expansion valve and the outdoor heat exchanger. The first end of the second bypass is connected to the pipeline between the indoor heat exchanger and the electronic expansion valve, and the second end is connected to the pipeline between the outdoor heat exchanger and the four-way valve. The first bypass is provided with a first bypass valve, and the second bypass is provided with a second bypass valve. The solenoid valve is located between the first end of the first bypass and the indoor heat exchanger. The defrosting control method includes: When the air source heat pump system is operating in defrost mode, the first bypass valve and the second bypass valve on the first bypass and the second bypass are opened, and the solenoid valve and the electronic expansion valve are closed for defrosting. The four-way valve does not switch directions, allowing the high-temperature and high-pressure refrigerant flowing out of the indoor heat exchanger to flow through the second bypass and mix with the refrigerant flowing out of the outdoor heat exchanger. This replenishes the refrigerant in the circuit, increases the compressor power, and thus helps to speed up the defrosting speed and improve the defrosting efficiency.

2. The defrost control method of an air source heat pump system according to claim 1, characterized by, The first port of the four-way valve is connected to the exhaust port of the compressor, the second port of the four-way valve is connected to the first end of the indoor heat exchanger, the third port of the four-way valve is connected to the intake port of the compressor, the second end of the indoor heat exchanger is connected to the electronic expansion valve, the electronic expansion valve is connected to the first end of the outdoor heat exchanger, and the second end of the outdoor heat exchanger is connected to the fourth port of the four-way valve.

3. The defrost control method of an air source heat pump system according to claim 1, characterized by, The compressor's suction port is also connected to a gas-liquid separator; a liquid storage tank is also provided between the indoor heat exchanger and the electronic expansion valve, and correspondingly, the first end of the second bypass is connected to the pipeline between the liquid storage tank and the electronic expansion valve.

4. The defrost control method of an air source heat pump system according to any one of claims 1 to 3, characterized in that, The indoor heat exchanger is also equipped with an electric heating device and an indoor fan, and the outdoor heat exchanger is also equipped with an outdoor fan.

5. The defrost control method of an air source heat pump system according to any one of claims 1-3, wherein, The first bypass valve and the second bypass valve are solenoid valves.

6. The defrost control method of an air source heat pump system according to claim 1, characterized by, An indoor fan is also provided at the indoor heat exchanger, and an outdoor fan is also provided at the outdoor heat exchanger. The defrosting control method further includes: During defrosting, control the indoor fan to reduce its speed and control the outdoor fan to shut down.

7. The defrost control method of an air source heat pump system according to claim 1, characterized by, The indoor heat exchanger is also equipped with an electric heating device, and the defrosting control method further includes: Turn on the electric heating device during defrosting to maintain the indoor temperature.

8. The defrost control method of an air source heat pump system according to claim 1, characterized by, Also includes: When defrosting is complete, the solenoid valve and the electronic expansion valve are opened, and the first bypass valve and the second bypass valve on the first bypass and the second bypass are closed, so that the air source heat pump system resumes heating mode.

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