Water circuit antifreeze control method for heat pump air conditioning units and heat pump air conditioning units

Abstract

This invention belongs to the field of air source heat pump technology, and discloses a water circuit antifreeze control method for heat pump air conditioning units and a heat pump air conditioning unit. The water circuit antifreeze control method for heat pump air conditioning units is used for control during the cooling process of heat pump air conditioning units, and includes the following steps: S10, parameter acquisition: acquiring the refrigerant coil temperature T1 at the inlet of the refrigerant channel of the heat exchanger and the outlet water temperature T2 at the outlet of the water channel of the heat exchanger; S20, cooling capacity adjustment: judging whether the refrigerant coil temperature T1 is greater than a first preset value T3 every first preset time interval: if T1>T3, then adjusting the cooling capacity according to a first control strategy; if T1≤T3, then reducing the cooling capacity; if T1≤T3 continues for a first preset time interval, then shutting down the unit; at the same time, judging whether the outlet water temperature T2 is less than a second preset value T4 every second preset time interval: if T2≥T4, then adjusting the cooling capacity according to a second control strategy; if T2<T4 continues for a second preset time interval, then shutting down the unit.

Description

Technical Field

[0001] This invention relates to the field of air source heat pump technology, and in particular to a water circuit antifreeze control method for a heat pump air conditioning unit and a heat pump air conditioning unit. Background Technology

[0002] A heat pump air conditioning unit is a circulating system consisting of a compressor, an outdoor unit, and an indoor unit. It includes two circulation loops: a refrigerant loop and a circulating water loop. The refrigerant circulates within the heat pump air conditioning unit under the action of the compressor, heating or cooling the corresponding circulating water, thus achieving the function of cooling in summer or heating in winter. Therefore, heat pump air conditioning units are widely used in residential, commercial buildings, and other places to improve the comfort of ambient temperature.

[0003] Currently, during the cooling operation of heat pump air conditioning units, when the flow rate of the circulating water in the circulation circuit is low, indicating a potential blockage or leak, the corresponding compressor, evaporator, and other components may freeze and damage due to the low temperature, thus harming the entire refrigerant circuit. Existing heat pump air conditioning units often have flow switches in the circulation circuit to monitor the flow rate. However, these flow switches frequently leak and break down, requiring maintenance. This maintenance is costly and frequent, resulting in high maintenance expenses and a poor user experience, negatively impacting the user experience of the heat pump air conditioning unit. Summary of the Invention

[0004] One objective of this invention is to provide a water circuit antifreeze control method for heat pump air conditioning units, which can replace the water flow switch by controlling the internal structure during use, thereby reducing development costs, unit maintenance costs, and maintenance risks.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A method for preventing freeze in the water circuit of a heat pump air conditioning unit is provided for controlling the cooling process of the heat pump air conditioning unit. The heat pump air conditioning unit includes a refrigerant circuit and a cooling water circuit. The refrigerant circuit includes a refrigerant passage that circulates between a compressor, evaporator, expansion valve, and heat exchanger. The cooling water circuit is connected to the water passage of the heat exchanger for heat exchange with the refrigerant passage. The method for preventing freeze in the water circuit of the heat pump air conditioning unit includes the following steps:

[0007] S10. Parameter acquisition: Acquire the refrigerant coil temperature T1 at the inlet of the refrigerant channel of the heat exchanger and the outlet water temperature T2 at the outlet of the water channel of the heat exchanger.

[0008] S20. Cooling capacity adjustment: Every first preset time interval, determine whether the temperature T1 of the above-mentioned cooling coil is greater than the first preset value T3: if T1>T3, adjust the cooling capacity according to the first control strategy; if T1≤T3, reduce the cooling capacity; if T1≤T3 continues for the first preset time, shut down the machine.

[0009] At the same time, every second preset time interval, it is determined whether the above-mentioned outlet water temperature T2 is less than the second preset value T4: if T2≥T4, the cooling capacity is adjusted according to the second control strategy; if T2<T4 continues for the second preset time, the machine is shut down.

[0010] Optionally, in step S20, the first control strategy mentioned above includes:

[0011] If T3 < T1 ≤ T5, then the frequency F of the compressor remains unchanged, and the opening degree of the expansion valve P = ΔP + P1, until P = Pmax.

[0012] If T5 < T1 ≤ T6, then the opening degree P of the expansion valve remains unchanged.

[0013] If T1 > T6, then the cooling capacity will be adjusted and controlled according to the preset cooling control strategy;

[0014] Wherein, T5 is the third preset value, ΔP is the current opening degree of the expansion valve, P1 is the preset opening degree change value of the expansion valve, Pmax is the maximum opening degree of the expansion valve, and T6 is the fourth preset value.

[0015] Optionally, in step S20, the method to reduce the cooling capacity when T1≤T3 includes: the opening degree of the expansion valve P=Pmax, the frequency of the compressor F=ΔF-F1, until F=Fmin;

[0016] Wherein, ΔF is the current frequency of the compressor, F1 is the preset frequency change value of the compressor, and Fmin is the minimum frequency of the compressor.

[0017] Optionally, in step S20, the second control strategy includes:

[0018] If T4≤T2<T7, then the frequency of the compressor mentioned above is F=ΔF-F1, until F=Fmin;

[0019] If T2 ≥ T7, then the frequency F of the compressor remains unchanged.

[0020] Wherein, T7 is the fifth preset value, ΔF is the current frequency of the compressor, F1 is the preset frequency change value of the compressor, and Fmin is the minimum frequency of the compressor.

[0021] Optionally, in step S20, if the above-mentioned outlet water temperature T2 detection fails, the inlet water temperature T8 of the water channel inlet of the heat exchanger is obtained, T2 = T8 - ΔT; where ΔT is a preset difference between the above-mentioned inlet water temperature T8 and the above-mentioned outlet water temperature T2.

[0022] Optionally, the first preset time is 5 seconds; and / or the second preset time is 10 seconds.

[0023] Optionally, in step S20, the heat pump air conditioning unit will automatically restart after a preset protection time after it stops, until the heat pump air conditioning unit stops automatically after a preset number of times within a third preset time.

[0024] One objective of this invention is to provide a heat pump air conditioning unit that can detect water flow status without a water flow switch, thereby reducing development costs, unit maintenance costs, and maintenance risks.

[0025] To achieve this objective, the present invention adopts the following technical solution:

[0026] The heat pump air conditioning unit is regulated using the above-mentioned heat pump air conditioning unit water circuit antifreeze control method. The heat pump air conditioning unit includes a refrigerant circuit and a cooling water circuit. The refrigerant circuit includes a refrigerant passage that is circulated and connected to a compressor, evaporator, expansion valve and heat exchanger. The cooling water circuit is connected to the water passage of the heat exchanger to exchange heat with the refrigerant passage.

[0027] Optionally, a first temperature sensing element is provided at the inlet of the refrigerant channel of the heat exchanger at the refrigeration coil for detecting the temperature of the refrigeration coil; and / or,

[0028] A second temperature sensor is provided at the outlet of the water passage of the aforementioned heat exchanger for detecting the outlet water temperature; and / or,

[0029] The heat exchanger is equipped with a third temperature detection element at the water inlet to detect the inlet water temperature.

[0030] Optionally, the refrigerant circuit further includes a four-way valve, wherein the first port of the four-way valve is connected to the outlet of the compressor, the second port of the four-way valve is connected to the inlet of the evaporator, and the first port can be connected to the second port; the third port of the four-way valve is connected to the outlet of the refrigerant passage of the heat exchanger, and the fourth port of the four-way valve is connected to the inlet of the compressor, and the third port can be connected to the fourth port.

[0031] The beneficial effects of this invention are:

[0032] This invention provides a water circuit antifreeze control method for heat pump air conditioning units and a heat pump air conditioning unit. By monitoring and controlling the temperature of the refrigerant coil and the outlet water temperature of the cooling water circuit, the amount of cooling capacity in the refrigerant circuit and the amount of water in the cooling water circuit can be determined and adjusted. When the temperature of the refrigerant coil is continuously lower than a first preset value and / or the outlet water temperature is continuously lower than a second preset value, it indicates that the amount of water in the cooling water circuit is small. This allows for the monitoring of the amount of water in the cooling water circuit, replacing the water flow switch, preventing the heat pump air conditioning unit from freezing and reducing development costs, unit maintenance costs, and maintenance risks. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the working principle of a heat pump air conditioning unit provided in a specific embodiment of the present invention.

[0034] In the picture:

[0035] 1. Refrigerant circuit; 2. Cooling water circuit; 10. Compressor; 20. Evaporator; 30. Expansion valve; 40. Heat exchanger; 50. Four-way valve; 60. First temperature sensor; 70. Second temperature sensor; 80. Third temperature sensor. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0037] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0039] In the description of this embodiment, the terms "upper," "lower," "left," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0040] This embodiment provides a heat pump air conditioning unit. The heat pump air conditioning unit is regulated by the water circuit antifreeze control method of this embodiment, which can realize the function of detecting water flow status without water flow switch, thereby reducing development cost, unit maintenance cost and maintenance risk.

[0041] Please refer to Figure 1 Specifically, the heat pump air conditioning unit includes a refrigerant circuit 1 and a cooling water circuit 2. The refrigerant circuit 1 includes a refrigerant passage that circulates between a compressor 10, an evaporator 20, an expansion valve 30, and a heat exchanger 40. The cooling water circuit 2 is connected to the water passage of the heat exchanger 40 to exchange heat with the refrigerant passage, thereby achieving the cooling effect of the heat pump air conditioning unit. Specifically, the outlet of the compressor 10 is connected to the inlet of the evaporator 20, the outlet of the evaporator 20 is connected to the inlet of the expansion valve 30, the outlet of the expansion valve 30 is connected to the inlet of the refrigerant passage of the heat exchanger 40, and the outlet of the refrigerant passage of the heat exchanger 40 is connected to the inlet of the compressor 10, so as to realize the circulation of refrigerant within the refrigerant circuit 1.

[0042] Optionally, the refrigerant circuit 1 also includes a four-way valve 50. The first port of the four-way valve 50 is connected to the outlet of the compressor 10, and the second port of the four-way valve 50 is connected to the inlet of the evaporator 20. The first port can be connected to the second port. The third port of the four-way valve 50 is connected to the outlet of the refrigerant passage of the heat exchanger 40, and the fourth port of the four-way valve 50 is connected to the inlet of the compressor 10. The third port can be connected to the fourth port. The four-way valve 50 enables the flow of two paths, thereby reducing the number of connecting pipes and improving the integration and space utilization of the heat pump air conditioning unit.

[0043] In some embodiments, a first temperature detection element 60 is provided at the refrigeration coil at the inlet of the refrigerant channel of the heat exchanger 40 to detect the temperature of the refrigeration coil; thereby facilitating the regulation of the heat pump air conditioning unit based on the temperature of the refrigeration coil.

[0044] In some embodiments, a second temperature sensor 70 is provided at the water channel outlet of the heat exchanger 40 to detect the outlet water temperature, thereby facilitating the regulation of the heat pump air conditioning unit based on the outlet water temperature.

[0045] In some embodiments, a third temperature sensor 80 is provided at the water channel inlet of the heat exchanger 40 to detect the inlet water temperature, thereby facilitating the regulation of the heat pump air conditioning unit based on the inlet water temperature.

[0046] In some embodiments, the heat pump air conditioning unit further includes a heating water circuit, which is connected to the heat dissipation section of the refrigerant circuit 1 for heat exchange, so as to realize the heating effect of the heating water circuit, thereby realizing the cooling of the heat pump air conditioning unit.

[0047] Please refer to Figure 1 This embodiment also provides a water circuit antifreeze control method for a heat pump air conditioning unit, which is used for control during the cooling process of the heat pump air conditioning unit. The heat pump air conditioning unit includes a refrigerant circuit 1 and a cooling water circuit 2. The refrigerant circuit 1 includes a refrigerant passage that circulates between a compressor 10, an evaporator 20, an expansion valve 30, and a heat exchanger 40. The cooling water circuit 2 is connected to the water passage of the heat exchanger 40 for heat exchange with the refrigerant passage. Specifically, the water circuit antifreeze control method for the heat pump air conditioning unit includes the following steps:

[0048] Step S10, Parameter Acquisition: Acquire the refrigerant coil temperature T1 at the inlet of the refrigerant channel of the heat exchanger 40 and the outlet water temperature T2 at the outlet of the water channel of the heat exchanger 40; that is, acquire the refrigerant coil temperature T1 through the first temperature detection element 60 and the outlet water temperature T2 through the second temperature detection element 70, so as to facilitate subsequent judgment and control.

[0049] Step S10 is followed by step S20, cooling capacity adjustment: Every first preset time interval, it is determined whether the cooling coil temperature T1 is greater than a first preset value T3. If T1 > T3, the cooling capacity is adjusted according to the first control strategy; if T1 ≤ T3, the cooling capacity is reduced; if T1 ≤ T3 for the first preset time, the system is shut down. That is, when the cooling coil temperature T1 is less than the first preset value T3, it indicates that the cooling capacity of the refrigeration circuit is too large, suggesting issues such as insufficient cooling capacity from refrigerant circuit 1, high compressor frequency, and / or high expansion valve opening. Therefore, the cooling capacity is reduced by adjusting the compressor frequency and expansion valve opening. If T1 ≤ T3 for the first preset time, it indicates insufficient cooling capacity from refrigerant circuit 1, i.e., insufficient cooling water in cooling water circuit 2, thus requiring shutdown.

[0050] Simultaneously, every second preset time interval, it is determined whether the outlet water temperature T2 is less than the second preset value T4: if T2 ≥ T4, the cooling capacity is adjusted according to the second control strategy; if T2 < T4 for the second preset time, the system is shut down. That is, when the outlet water temperature T2 is continuously less than the second preset value T4, it indicates that the cooling capacity of the cooling water circuit 2 is too large, and there is a problem of reduced water volume in the refrigerant circuit 1, so the system needs to be shut down.

[0051] The antifreeze control method for the water circuit of the heat pump air conditioning unit in this embodiment can determine and adjust the amount of cooling capacity in the refrigerant circuit 1 and the amount of water in the cooling water circuit 2 by monitoring and controlling the temperature of the cooling coil and the outlet water temperature of the cooling water circuit 2. When the temperature of the cooling coil is continuously lower than the first preset value and / or the outlet water temperature is continuously lower than the second preset value, it indicates that the amount of water in the cooling water circuit 2 is small. This allows for the monitoring of the amount of water in the cooling water circuit 2, replacing the water flow switch, preventing the heat pump air conditioning unit from freezing and reducing development costs, unit maintenance costs and maintenance risks.

[0052] It is understood that in the water circuit antifreeze control method of the heat pump air conditioning unit in this embodiment, the control of the cooling coil temperature and the control of the outlet water temperature do not interfere with each other under normal circumstances. That is, when the cooling coil temperature is low, the corresponding outlet water temperature will also be low. However, when either of them is lower than the normal range, the cooling capacity can be adjusted according to the corresponding control strategy.

[0053] Understandably, the heat pump air conditioning unit should be pre-run for at least 2 minutes before the cooling capacity is controlled, so that the entire heat pump air conditioning unit is in normal condition.

[0054] Optionally, the first preset time and the second preset time are detection intervals set according to requirements, and are not specifically limited here. For example, in this embodiment, the first preset time is 5s and / or the second preset time is 10s, which is sufficient to control the heat pump air conditioning unit.

[0055] Optionally, the first preset value T3 is the lower limit of the cooling temperature in the refrigerant circuit 1. If it remains below this value, the structure in the refrigerant circuit 1 will be damaged. For example, in this embodiment, the first preset value T3 is 0°C. Of course, in other embodiments, the first preset value T3 can also be 1°C, 2°C, -1°C, -2°C, etc., and is not specifically limited here.

[0056] Optionally, the second preset value T4 is the lower limit of the outlet water temperature in cooling water circuit 2. If it remains below this value, it indicates that the water volume in cooling water circuit 2 is low because the outlet water temperature after cooling and heat exchange is low. For example, in this embodiment, the second preset value T4 is 3°C. Of course, in other embodiments, the second preset value T4 can also be 0°C, 1°C, 2°C, 4°C, 5°C, etc., and is not specifically limited here.

[0057] In some embodiments, in step S20, the first control strategy includes: if T3 < T1 ≤ T5, the frequency F of the compressor 10 remains unchanged, and the opening degree P of the expansion valve 30 is P = ΔP + P1 until P = Pmax; if T5 < T1 ≤ T6, the opening degree P of the expansion valve 30 remains unchanged; if T1 > T6, the cooling capacity is adjusted and controlled according to the preset refrigeration control strategy; wherein, T5 is the third preset value, ΔP is the current opening degree of the expansion valve 30, P1 is the preset opening degree change value of the expansion valve 30, Pmax is the maximum opening degree of the expansion valve 30, and T6 is the fourth preset value.

[0058] The first control strategy involves controlling the cooling capacity of the heat pump air conditioning unit when the refrigerant coil temperature T1 > T6, placing it within the normal temperature range of the refrigerant cooling section. Within this range, a preset cooling control strategy can be used for cooling capacity regulation. When T5 < T1 ≤ T6, the temperature of the cooling section is slightly lower than the normal temperature range. In this case, the opening P of the expansion valve 30 is kept constant to reduce the rate of increase in cooling capacity. Within the range T3 < T1 ≤ T5, further adjustment of the cooling capacity is needed to quickly raise the temperature of the cooling section. Therefore, by stopping the adjustment of the compressor 10 frequency and gradually reducing the opening of the expansion valve 30, the cooling capacity is reduced, thereby promoting the temperature increase of the cooling section and gradually bringing it into the normal temperature range.

[0059] Optionally, the third preset value T5 is an intermediate value within the lower temperature range of the refrigerant circuit 1. If the temperature is lower than this value but higher than the first preset value T3, there is a risk of a decrease in the refrigerant temperature in the refrigerant circuit 1. For example, in this embodiment, the third preset value T5 is 3°C. Of course, in other embodiments, the first preset value T3 can also be 2°C, 4°C, 5°C, etc., and is not specifically limited here.

[0060] Optionally, the fourth preset value T6 is the lower limit of the normal temperature range of the refrigerant circuit 1. If the temperature is higher than this value, it is considered to be within the normal temperature range. For example, in this embodiment, the fourth preset value T6 is 5°C. Of course, in other embodiments, the fourth preset value T6 can also be 4°C, 6°C, 7°C, etc., and is not specifically limited here.

[0061] Optionally, the preset opening change value P1 of the expansion valve 30 is an opening change value set according to actual needs. For example, in this embodiment, the preset opening change value P1 of the expansion valve 30 is 40P. Of course, in other embodiments, the first preset value T3 can also be 30P, 50P, 60P, etc., and is not specifically limited here.

[0062] Optionally, Pmax is the maximum opening degree of the expansion valve 30, typically 480P.

[0063] In some embodiments, in step S20, the method for reducing cooling capacity when T1≤T3 includes: adjusting the opening degree of the expansion valve 30 to P=Pmax, and adjusting the frequency of the compressor 10 to F=ΔF-F1, until F=Fmin; where ΔF is the current frequency of the compressor 10, F1 is the preset frequency change value of the compressor 10, and Fmin is the minimum frequency of the compressor 10. That is, when T1≤T3, the cooling capacity is reduced by decreasing the frequency of the compressor 10 and increasing the opening degree of the expansion valve 30, i.e., by increasing the temperature of the refrigerant exiting the compressor 10 and rapidly entering the refrigeration section, the temperature of the refrigeration section is increased, so that the temperature of the refrigerant in the refrigerant circuit 1 gradually returns to the normal temperature range, avoiding damage to the heat pump air conditioning unit.

[0064] In some embodiments, in step S20, the second control strategy includes: if T4≤T2<T7, then the frequency F of the compressor 10 is ΔF-F1 until F=Fmin; if T2≥T7, then the frequency F of the compressor 10 remains unchanged; wherein, ΔF is the current frequency of the compressor 10, F1 is the preset frequency change value of the compressor 10, and Fmin is the minimum frequency of the compressor 10.

[0065] The second control strategy involves controlling the cooling water circuit 2. When the outlet water temperature T2 ≥ T7, the cooling water circuit 2 is in its normal outlet water temperature range under cooling conditions. Within this range, there is no need to significantly change the cooling capacity by altering the compressor 10 frequency F; only the opening of the expansion valve 30 needs to be adjusted for small-scale cooling capacity control. When T4 ≤ T2 < T7, it indicates that the temperature of the cooling water circuit 2 is below the normal temperature range but above the lower limit. In this case, it is only necessary to reduce the compressor 10 frequency F to quickly increase the cooling capacity of the heat pump air conditioning unit and raise the outlet water temperature, allowing it to gradually enter the normal temperature range.

[0066] Optionally, the fifth preset value T7 is the middle value of the lower range of outlet water temperature in cooling water circuit 2. If the temperature is below this value, it indicates a risk of insufficient water volume in cooling water circuit 2. For example, the fifth preset value T7 in this embodiment is 6°C. Of course, in other embodiments, the fifth preset value T7 can also be 4°C, 5°C, 7°C, 8°C, etc., and is not specifically limited here.

[0067] In some embodiments, in step S20, if the outlet water temperature T2 detection fails, the inlet water temperature T8 of the water channel inlet of the heat exchanger 40 is obtained, and T2 = T8 - ΔT; where ΔT is a preset difference between the inlet water temperature T8 and the outlet water temperature T2.

[0068] Optionally, ΔT in this embodiment is 4℃. Of course, in other embodiments, the fifth preset value T7 can also be 3℃, 5℃, 7℃, etc., and is not specifically limited here.

[0069] In some embodiments, in step S20, the heat pump air conditioning unit automatically restarts after a preset protection time following shutdown, until the heat pump air conditioning unit shuts down a preset number of times within a third preset time, at which point automatic restarting stops. This is to prevent misjudgment in the event that the heat pump air conditioning unit automatically restarts after shutdown, but after running for a period of time after restarting, it remains within the fault judgment range of the heat pump air conditioning unit's control method, and this situation persists even after a preset number of restarts within a third preset time. In this case, it is determined that the heat pump air conditioning unit has malfunctioned, and it stops operating and awaits maintenance.

[0070] Optionally, the third preset time includes the standby time of the heat pump air conditioning unit and the determination time after multiple restarts, which can be set according to actual needs. The preset number of times is also the preset number of times to determine whether a fault has occurred, which can also be set according to actual needs. For example, in this embodiment, the third preset time is 1 hour and the preset number of times is 3.

[0071] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. 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 claims of the present invention.

Claims

1. A method for preventing water circuit freeze in a heat pump air conditioning unit, characterized in that, For control during the cooling process of a heat pump air conditioning unit, the heat pump air conditioning unit includes a refrigerant circuit (1) and a cooling water circuit (2). The refrigerant circuit (1) includes a refrigerant passage that circulates between a compressor (10), an evaporator (20), an expansion valve (30), and a heat exchanger (40). The cooling water circuit (2) is connected to the water passage of the heat exchanger (40) for heat exchange with the refrigerant passage. The water circuit antifreeze control method for the heat pump air conditioning unit includes the following steps: S10, Parameter acquisition: Acquire the refrigerant coil temperature T1 at the inlet of the refrigerant channel of the heat exchanger (40) and the outlet water temperature T2 at the outlet of the water channel of the heat exchanger (40); S20. Cooling capacity adjustment: Every first preset time interval, determine whether the temperature T1 of the cooling coil is greater than the first preset value T3: if T1>T3, adjust the cooling capacity according to the first control strategy; if T1≤T3, reduce the cooling capacity; if T1≤T3 continues for the first preset time, shut down the machine. At the same time, every second preset time interval, it is determined whether the outlet water temperature T2 is less than the second preset value T4: if T2≥T4, the cooling capacity is adjusted according to the second control strategy; if T2<T4 continues for the second preset time, the machine is shut down.

2. The water circuit antifreeze control method for heat pump air conditioning units according to claim 1, characterized in that, In step S20, the first control strategy includes: If T3 < T1 ≤ T5, then the frequency F of the compressor (10) remains unchanged, and the opening degree P of the expansion valve (30) is P = ΔP + P1 until P = Pmax; If T5 < T1 ≤ T6, then the opening degree P of the expansion valve (30) remains unchanged; If T1 > T6, then the cooling capacity will be adjusted and controlled according to the preset cooling control strategy; Wherein, T5 is the third preset value, ΔP is the current opening degree of the expansion valve (30), P1 is the preset opening degree change value of the expansion valve (30), Pmax is the maximum opening degree of the expansion valve (30), and T6 is the fourth preset value.

3. The water circuit antifreeze control method for heat pump air conditioning units according to claim 1, characterized in that, In step S20, the method to reduce the cooling capacity when T1≤T3 includes: the opening degree of the expansion valve (30) P=Pmax, the frequency of the compressor (10) F=ΔF-F1, until F=Fmin; Wherein, ΔF is the current frequency of the compressor (10), F1 is the preset frequency change value of the compressor (10), and Fmin is the minimum frequency of the compressor (10).

4. The water circuit antifreeze control method for heat pump air conditioning units according to claim 1, characterized in that, In step S20, the second control strategy includes: If T4≤T2<T7, then the frequency of the compressor (10) is F=ΔF-F1, until F=Fmin; If T2 ≥ T7, then the frequency F of the compressor (10) remains unchanged; Wherein, T7 is the fifth preset value, ΔF is the current frequency of the compressor (10), F1 is the preset frequency change value of the compressor (10), and Fmin is the minimum frequency of the compressor (10).

5. The water circuit antifreeze control method for heat pump air conditioning units according to claim 1, characterized in that, In step S20, if the detection of the outlet water temperature T2 fails, the inlet water temperature T8 of the water channel inlet of the heat exchanger (40) is obtained, and T2 = T8 - ΔT; where ΔT is a preset difference between the inlet water temperature T8 and the outlet water temperature T2.

6. The water circuit antifreeze control method for heat pump air conditioning units according to claim 1, characterized in that, The first preset time is 5 seconds; and / or the second preset time is 10 seconds.

7. The water circuit antifreeze control method for heat pump air conditioning units according to any one of claims 1-6, characterized in that, In step S20, the heat pump air conditioning unit will automatically restart after a preset protection time after it stops, until the heat pump air conditioning unit stops automatically after a preset number of times within a third preset time.

8. A heat pump air conditioning unit, characterized in that, The heat pump air conditioning unit is regulated by the antifreeze control method of the water circuit of the heat pump air conditioning unit as described in any one of claims 1-7. The heat pump air conditioning unit includes a refrigerant circuit (1) and a cooling water circuit (2). The refrigerant circuit (1) includes a refrigerant passage of a compressor (10), an evaporator (20), an expansion valve (30), and a heat exchanger (40) that are circulated in a loop. The cooling water circuit (2) is connected to the water passage of the heat exchanger (40) to exchange heat with the refrigerant passage.

9. The heat pump air conditioning unit according to claim 8, characterized in that, The heat exchanger (40) has a first temperature sensor (60) at the inlet of the refrigerant channel at the refrigeration coil for detecting the temperature of the refrigeration coil; and / or, The heat exchanger (40) is equipped with a second temperature sensor (70) at the water channel outlet for detecting the outlet water temperature; and / or, The heat exchanger (40) is equipped with a third temperature detection element (80) at the water channel inlet for detecting the inlet water temperature.

10. The heat pump air conditioning unit according to claim 8, characterized in that, The refrigerant circuit (1) also includes a four-way valve (50), the first port of which is connected to the outlet of the compressor (10), the second port of which is connected to the inlet of the evaporator (20), and the first port can be connected to the second port; the third port of which is connected to the outlet of the refrigerant passage of the heat exchanger (40), and the fourth port of which is connected to the inlet of the compressor (10), and the third port can be connected to the fourth port.

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