A variable-frequency defrosting method

Abstract

The present invention relates to the field of air source heat pumps, in particular to a variable frequency defrosting method. The variable frequency defrosting method is used for an air source heat pump, and the air source heat pump includes a compressor, an evaporator, a condenser, a temperature sensor, a controller, and a four-way reversing valve. The air source heat pump has a heating mode and multiple defrosting modes. The power of the compressor, the power of the evaporator, and the direction of the four-way reversing valve are adjusted according to the ambient temperature and the temperature of the evaporator, so as to adopt different defrosting modes according to different ambient temperatures and evaporator temperatures, which has the advantages of optimizing the defrosting mode and optimizing the operating state of the air source heat pump, and achieving the effects of energy saving and noise reduction.

Description

Technical Field

[0001] The present invention relates to the field of heat pumps, especially air source heat pumps, and particularly to a variable frequency defrosting method. Background Art

[0002] An air source heat pump includes a compressor, a heat exchanger, an evaporator, a condenser, a temperature sensor and a controller. Some heat pumps are provided with a four-way reversing valve. The air source heat pump is driven by an electric motor, and its specific working process is as follows: the compressor compresses the refrigerant. The refrigerant with an increased temperature after compression passes through the condenser in the water tank to produce hot water. The refrigerant after heat exchange absorbs heat from the air through the evaporator, and then the refrigerant returns to the compressor for the next cycle.

[0003] During use, if the temperature of the outdoor unit (evaporator) of the air source heat pump is too low, frosting of the outdoor unit will occur. After frosting of the outdoor unit, the heating efficiency of the air source heat pump will decrease.

[0004] Currently, the conventional defrosting control schemes of air source heat pumps adopted in the swimming pool heat pump industry include hot gas bypass defrosting and reversing defrosting.

[0005] Hot gas bypass defrosting means that a bypass circuit is led out from the compressor exhaust port to lead the compressor exhaust gas into the outdoor heat exchanger to achieve defrosting, which does not generate noise, but the defrosting is too slow and not clean enough; reversing defrosting means that the four-way reversing valve is reversed to absorb heat from the indoor unit and transfer the heat to the outdoor unit for defrosting. The defrosting speed is fast, but the noise is large and the heat loss is too large. Summary of the Invention

[0006] To solve the above technical problems, the purpose of the present invention is to provide a variable frequency defrosting method for an air source heat pump, which has the advantages of optimizing the defrosting mode and optimizing the operating state of the air source heat pump.

[0007] The technical solution adopted by the present invention to solve the problem is: a variable frequency defrosting method for an air source heat pump, the air source heat pump includes a compressor, a heat exchanger, an evaporator, a temperature sensor, a controller and a four-way reversing valve. The air source heat pump has a heating mode and multiple defrosting modes. When the controller detects that the heat pump is in the heating mode:

[0008] If the temperature sensor detects that the ambient temperature is 5°C to 10°C and the heat exchanger temperature is 0°C to 2°C, the heat pump enters the defrosting mode. At this time, the controller controls the operating frequency of the compressor to drop to the middle frequency band and the power of the evaporator to increase; in this mode, the machine reaches the optimal operating state, ensuring both a relatively high heating capacity COP (heating capacity per unit power) and low noise of the unit;

[0009] If the temperature sensor detects that the ambient temperature is between 5°C and 10°C and the heat exchanger temperature is between -2°C and 0°C, the heat pump enters the defrosting mode. The controller controls the operating frequency of the compressor to drop to the low frequency range and the power of the evaporator to increase. The defrosting efficiency of this defrosting mode is higher than that of the previous defrosting mode.

[0010] If the temperature sensor detects that the ambient temperature is between 3°C and 5°C and the heat exchanger temperature is between -7°C and -2°C, the heat pump enters the defrosting mode. The controller controls the compressor to stop and the power of the evaporator to increase. Defrosting is carried out only by the heat in the air. In this defrosting mode, there is no indoor heat loss.

[0011] If the temperature sensor detects that the ambient temperature is between -5°C and 7°C and the heat exchanger temperature is lower than -7°C, or the temperature sensor detects that the ambient temperature is between -15°C and -5°C and the heat exchanger temperature is more than 5°C lower than the ambient temperature, the heat pump enters the defrosting mode. The controller controls the four-way reversing valve and the compressor to operate at high frequency and the evaporator motor not to operate. Defrosting is carried out by the reverse operation of the refrigerant in the heat exchanger, consuming indoor heat to achieve rapid defrosting. This defrosting mode has both heat loss and noise, but it can defrost quickly and ensure clean defrosting.

[0012] When the heat pump does not enter the defrosting mode for two consecutive defrosting cycles when the temperature sensor detects that the ambient temperature is between -15°C and 0°C, or when the heat pump does not enter the defrosting mode for two consecutive defrosting cycles when the temperature sensor detects that the evaporator temperature is lower than -7°C; then the controller controls the heat pump to enter the defrosting mode. The controller controls the four-way reversing valve to start, the compressor to operate at high frequency and the evaporator motor not to operate. In this case, there is a measurement error or abnormality in the temperature sensor, so the forced timed defrosting mode is started.

[0013] As a further improvement of the above technical solution, the gas source heat pump exits the defrosting mode when any of the following conditions is met:

[0014] 1) The heat exchanger temperature does not drop below a°C for 20 seconds continuously;

[0015] 2) The heat exchanger temperature does not drop below (a - 2)°C for 40 seconds continuously;

[0016] 3) The heat exchanger temperature does not drop below (a - 5)°C for 50 seconds continuously;

[0017] 4) The actual defrosting time is not less than b minutes;

[0018] 5) The inlet water temperature of the heat pump is lower than 7°C or the outlet water temperature of the heat pump is lower than 4°C;

[0019] 6) The temperature sensor fails and the defrosting time is greater than 2 minutes;

[0020] Where a is a preset temperature value, and the range of a is 20±6, and b is a preset time value, and the range of b is 10±5. The range of a is set to 20±6 to ensure that the indoor constant temperature swimming pool is heated to a suitable temperature.

[0021] As a further improvement of the above technical solution, the defrosting cycle is 40±10 minutes.

[0022] The beneficial effects of the present invention are as follows: According to the current ambient temperature, it can intelligently judge which defrosting mode to adopt, strive for the optimal defrosting mode, so that the air source heat pump reaches the optimal operating state, ensuring both a relatively high heating COP and low noise of the unit, and can ensure the reliable and stable operation of the machine in the case of measurement errors or abnormalities of the temperature sensor. Description of the Drawings

[0023] The present invention will be further explained below in conjunction with the description of the drawings and the specific embodiments.

[0024] Figure 1 It is a schematic diagram of an air source heat pump;

[0025] Figure 2 It is a circuit diagram of a heat pump adopting the variable frequency defrosting method of the present invention. Specific Embodiments

[0026] This part will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the drawings. The role of the drawings is to supplement the description of the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the protection scope of the present invention.

[0027] In the description of the present invention, it should be understood that for the orientation description, such as the upper, lower, front, rear, left, right, etc., the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] In the description of the present invention, "several" means one or more, "multiple" means more than two, "greater than", "less than", "exceeding", etc. are understood not to include the present number, and "above", "below", "within", etc. are understood to include the present number. If the first and the second are described, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features. In the description of the present invention, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0029] A variable-frequency defrosting method for an air-source heat pump, referring to Figure 1 and Figure 2 is the air-source heat pump of the present invention. The air-source heat pump includes a compressor, an evaporator, a condenser, a temperature sensor, a controller, and a four-way reversing valve. The compressor is connected to the four-way reversing valve. One end of the four-way reversing valve is connected to the condenser, and the other end of the four-way reversing valve is connected to the evaporator. The connection between the evaporator and the condenser forms a closed loop for the origin heat pump. The temperature sensor is installed on the coil or fin of the evaporator to detect the temperature of the evaporator. The air-source heat pump has a heating mode and multiple defrosting modes:

[0030] When the controller detects that the heat pump is in the heating mode, the temperature sensor detects that the ambient temperature is 5°C to 10°C and the evaporator temperature is 0°C to 2°C, the heat pump enters the defrosting mode. At this time, the controller controls the operating frequency of the compressor to drop to the medium frequency band, and the operating power of the compressor with the medium frequency band is 50% to 70% of the rated power, and the power of the evaporator is increased; until the conditions for exiting the defrosting mode are met;

[0031] The controller detects that the heat pump is in the heating mode, the temperature sensor detects that the ambient temperature is 5°C to 10°C and the evaporator temperature is -2°C to 0°C, the heat pump enters the defrosting mode, and the controller controls the operating frequency of the compressor to drop to the low frequency band. The operating power of the compressor with the medium frequency band is 20% to 50% of the rated power, and the power of the evaporator is increased; until the conditions for exiting the defrosting mode are met;

[0032] The controller detects that the heat pump is in the heating mode, the temperature sensor detects that the ambient temperature is 3°C to 5°C and the evaporator temperature is -7°C to -2°C, the heat pump enters the defrosting mode, and the controller controls the compressor to stop and the power of the evaporator is increased; until the conditions for exiting the defrosting mode are met;

[0033] The controller detects that the heat pump is in the heating mode. When the temperature sensor detects that the ambient temperature is -5°C to 7°C and the evaporator temperature is lower than -7°C, the heat pump enters the defrosting mode. The controller controls the four-way reversing valve and the compressor to operate at high frequency. The operating power of the compressor in the high-frequency band is 70% to 100% of the rated power, and the evaporator motor does not operate; until the conditions for exiting the defrosting mode are met;

[0034] The controller detects that the heat pump is in the heating mode. When the temperature sensor detects that the ambient temperature is -15°C to -5°C and the evaporator temperature is more than 5°C lower than the ambient temperature, the heat pump enters the defrosting mode. The controller controls the four-way reversing valve and the compressor to operate at high frequency and the evaporator motor does not operate; until the conditions for exiting the defrosting mode are met;

[0035] The controller detects that the heat pump is in the heating mode; when the temperature sensor detects that the heat pump does not enter the defrosting mode for two consecutive defrosting cycles when the ambient temperature is -15°C to 0°C, or when the temperature sensor detects that the heat pump does not enter the defrosting mode for two consecutive defrosting cycles when the evaporator temperature is lower than -7°C; each defrosting cycle is 30 to 50 minutes, then the controller controls the heat pump to enter the defrosting mode. The controller controls the start of the four-way reversing valve and the compressor to operate at high frequency and the evaporator motor does not operate; until the conditions for exiting the defrosting mode are met.

[0036] The gas-source heat pump exits the defrosting mode as long as one of the following conditions is met: 1) The evaporator temperature remains not lower than a°C for 20 s; 2) The evaporator temperature remains not lower than (a - 2)°C for 40 s; 3) The evaporator temperature remains not lower than (a - 5)°C for 50 s; 4) The actual defrosting time is not less than b minutes; 5) The inlet water temperature of the heat pump is lower than 7°C or the outlet water temperature of the heat pump is lower than 4°C; 6) The temperature sensor fails and the defrosting time is greater than 2 minutes; where a is a preset temperature value, the range of a is 20 ± 6, and b is a preset time value, the range of b is 10 ± 5.

[0037] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A variable-frequency defrosting method for an air-source heat pump. The air-source heat pump includes a compressor, an evaporator, a condenser, a temperature sensor, a controller, and a four-way reversing valve. The air-source heat pump has a heating mode and multiple defrosting modes. It is characterized in that: When the controller detects that the heat pump is in the heating mode, and the temperature sensor detects that the ambient temperature is 5°C to 10°C and the evaporator temperature is 0°C to 2°C, the heat pump enters the defrosting mode. At this time, the controller controls the operating frequency of the compressor to drop to the medium frequency band and the power of the evaporator to increase; When the controller detects that the heat pump is in the heating mode, and the temperature sensor detects that the ambient temperature is 5°C to 10°C and the evaporator temperature is -2°C to 0°C, the heat pump enters the defrosting mode. The controller controls the operating frequency of the compressor to drop to the low frequency band and the power of the evaporator to increase; When the controller detects that the heat pump is in the heating mode, and the temperature sensor detects that the ambient temperature is 3°C to 5°C and the evaporator temperature is -7°C to -2°C, the heat pump enters the defrosting mode. The controller controls the compressor to stop and the power of the evaporator to increase; When the controller detects that the heat pump is in the heating mode, and the temperature sensor detects that the ambient temperature is -5°C to 7°C and the evaporator temperature is lower than -7°C, the heat pump enters the defrosting mode. The controller controls the four-way reversing valve and the compressor to operate at high frequency and the evaporator motor not to operate; When the controller detects that the heat pump is in the heating mode, and the temperature sensor detects that the ambient temperature is -15°C to -5°C and the evaporator temperature is more than 5°C lower than the ambient temperature, the heat pump enters the defrosting mode. The controller controls the four-way reversing valve and the compressor to operate at high frequency and the evaporator motor not to operate; When the controller detects that the heat pump is in the heating mode; when the heat pump does not enter the defrosting mode for two consecutive defrosting cycles when the temperature sensor detects that the ambient temperature is -15°C to 0°C, or when the heat pump does not enter the defrosting mode for two consecutive defrosting cycles when the temperature sensor detects that the evaporator temperature is lower than -7°C; then the controller controls the heat pump to enter the defrosting mode, and the controller controls to start the four-way reversing valve, the compressor to operate at high frequency and the evaporator motor not to operate.

2. The variable-frequency defrosting method according to claim 1, wherein If any of the following conditions is met, the air-source heat pump exits the defrosting mode: 1) The evaporator temperature does not drop below a°C for 20 s continuously; 2) The evaporator temperature does not drop below (a - 2)°C for 40 s continuously; 3) The evaporator temperature does not drop below (a - 5)°C for 50 s continuously; 4) The actual defrosting time is not less than b minutes; 5) The inlet water temperature of the heat pump is lower than 7°C or the outlet water temperature of the heat pump is lower than 4°C; 6) The temperature sensor fails and the defrosting time is greater than 2 minutes; Where a is a preset temperature value, the range of a is 20 ± 6, and b is a preset time value, the range of b is 10 ± 5.

3. The variable-frequency defrosting method according to claim 1, characterized in that: The defrosting cycle is 40 ± 10 minutes.

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