Defrosting control method and heat pump air conditioning unit

Abstract

This invention relates to the field of heat pump air conditioning technology, and discloses a defrosting control method and a heat pump air conditioning unit. The defrosting control method enters the defrosting monitoring stage by determining the outdoor heat exchanger temperature, simultaneously locking the initial air pressure and initial superheat as reference parameters, and then combining the basic trigger conditions of temperature and duration. A dual auxiliary verification mechanism of air-side pressure difference and refrigerant-side superheat difference is used to determine whether to start defrosting. Finally, different defrosting exit conditions are adopted according to different auxiliary trigger types. Compared with existing single-parameter control methods, this method comprehensively evaluates the frosting state from two independent dimensions: air flow resistance and refrigerant heat exchange capacity. It avoids misjudgment problems caused by factors such as heat exchanger blockage, insufficient refrigerant, and sensor installation deviation, significantly improving the accuracy and reliability of defrosting control. It can meet the high stability and high safety operation requirements of air source heat pump air conditioning units in special scenarios such as nuclear power plants.

Description

Technical Field

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

[0002] In winter heating conditions, air source heat pump air conditioners are prone to frost or even ice formation on the surface of the outdoor finned heat exchanger. If defrosting is not done in a timely and effective manner, it will directly lead to a sharp decline in the heat exchanger's heat exchange performance, resulting in a significant reduction in the unit's heating capacity and a significant increase in operating power consumption. This can then cause frequent start-ups and shutdowns or protective shutdowns of the unit. In severe cases, the frosting problem can also damage core components such as the compressor and four-way reversing valve, greatly reducing the reliability of the unit's operation. Ultimately, it may fail to meet the environmental conditions required for the normal operation of nuclear power plant process equipment and personnel operations, potentially leading to irreversible safety consequences.

[0003] Currently, the defrosting methods commonly used in commercial air source heat pump air conditioning units for winter heating have significant limitations and cannot be adapted to scenarios with high reliability requirements, such as nuclear power plants.

[0004] Among these methods, timed defrosting uses a fixed defrosting cycle and duration, which can easily lead to defrosting without frost or incomplete defrosting, directly resulting in a significant reduction in heating performance. Temperature difference time defrosting judges the frost status by monitoring the difference between ambient temperature and coil temperature, but it is easily affected by non-frost factors such as heat exchanger blockage and insufficient refrigerant, leading to misjudgments. Temperature time defrosting combines heat exchanger fin temperature and heating operation time for judgment, but due to uneven liquid distribution in the finned heat exchanger, there are temperature differences between different heat exchange tubes, and the temperature sensor installation position is highly sensitive, which can also lead to frost not being removed or incomplete defrosting. Although fuzzy intelligent control defrosting introduces multi-parameter fuzzy reasoning, the determination of fuzzification, defuzzification processes and membership functions is highly dependent on engineer experience and repeated trial and error, lacking a rigorous and universal theoretical guidance framework. Moreover, the controller rule set is fixed before the system runs and cannot be optimized and adjusted in real time according to actual operating conditions. In complex and ever-changing operating environments, there is still a risk of defrosting misjudgment and control failure due to program defects.

[0005] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a defrosting control method that comprehensively evaluates the frosting state from two independent dimensions: air flow resistance and refrigerant heat exchange capacity. This method can avoid misjudgment problems caused by factors such as heat exchanger blockage, insufficient refrigerant, and sensor installation deviation, and significantly improve the accuracy and reliability of defrosting control.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A defrosting control method is disclosed, the defrosting control method being implemented based on a heat pump air conditioning unit, the heat pump air conditioning unit comprising a compressor, an indoor heat exchanger, and an outdoor heat exchanger connected in sequence to achieve a cooling and heating cycle; the defrosting control method comprising: when the heat pump air conditioning unit is in heating mode, real-time detection of the temperature of the outdoor heat exchanger to determine whether to enter the defrosting monitoring stage; if it is determined that the defrosting monitoring stage has been entered, acquiring the initial air pressure and initial superheat of the outdoor heat exchanger, and starting a monitoring timer; based on the real-time detected temperature of the outdoor heat exchanger and the cumulative monitoring time, determining whether a preset defrosting basic trigger condition is met; if the preset defrosting basic trigger condition is met, then... By comparing the real-time air pressure and initial air pressure, and the real-time superheat and initial superheat of the outdoor heat exchanger, it is determined whether to execute the defrost mode, and the defrost assist trigger type is recorded. If it is determined to execute the defrost mode, the connection between the compressor, the indoor heat exchanger, and the outdoor heat exchanger is adjusted, and the high-temperature and high-pressure refrigerant discharged from the compressor flows through the outdoor heat exchanger for heating and defrosting, and the defrost operation timer is started. Based on the defrost assist trigger type and the cumulative defrost operation time, it is determined whether to exit the defrost mode. If it is determined to exit the defrost mode, the connection between the compressor, the indoor heat exchanger, and the outdoor heat exchanger is adjusted so that the heat pump air conditioning unit resumes the heating mode.

[0008] In the defrosting control method described above, the heat pump air conditioning unit further includes a first temperature sensor, which is located at the bend of the heat exchange tube on the coil end face of the outdoor heat exchanger, or at the middle fin on the non-windward side of the outdoor heat exchanger. The step of real-time detection of the outdoor heat exchanger temperature when the heat pump air conditioning unit is in heating mode to determine whether to enter the defrosting monitoring stage includes: acquiring the real-time temperature of the outdoor heat exchanger from the first temperature sensor when the heat pump air conditioning unit is in heating mode; and determining that the defrosting monitoring stage has been entered when the temperature of the outdoor heat exchanger is ≤ a preset start-up monitoring threshold.

[0009] In the defrosting control method described above, the heat pump air conditioning unit further includes a first pressure sensor located at the middle position of the non-windward side of the outdoor heat exchanger, a second temperature sensor located on the compressor suction port pipe, and a second pressure sensor located on the compressor suction port pipe; if it is determined that the defrosting monitoring stage has been entered, the initial air pressure and initial superheat of the outdoor heat exchanger are obtained, and the monitoring timer is started, including: when it is determined that the defrosting monitoring stage has been entered, obtaining the initial air pressure fed back by the first pressure sensor, the compressor suction temperature fed back by the second temperature sensor, and the compressor suction pressure fed back by the second pressure sensor; obtaining the refrigerant saturation temperature corresponding to the compressor suction pressure, calculating the initial superheat based on the compressor suction temperature and the refrigerant saturation temperature; resetting and starting the defrosting monitoring timer, and starting to accumulate the monitoring time.

[0010] In the defrosting control method, the step of determining whether the preset defrosting basic trigger conditions are met based on the real-time detected temperature of the outdoor heat exchanger and the cumulative monitoring time includes: obtaining the preset frosting risk critical temperature T and the preset cumulative monitoring time threshold X1; when the real-time detected temperature of the outdoor heat exchanger is ≤-T and the cumulative monitoring time is ≥X1, it is determined that the defrosting trigger conditions are met.

[0011] In the defrosting control method, if the preset defrosting basic trigger conditions are met, the method determines whether to execute the defrosting mode by comparing the real-time wind pressure and initial wind pressure, and the real-time superheat and initial superheat of the outdoor heat exchanger, and records the defrosting auxiliary trigger type. This includes: when the preset defrosting basic trigger conditions are met, obtaining the real-time wind pressure fed back by the first pressure sensor, and calculating the real-time superheat based on the real-time compressor suction temperature fed back by the second temperature sensor and the real-time compressor suction pressure fed back by the second pressure sensor; calculating the real-time wind pressure and initial superheat... The pressure difference between the wind pressure and the superheat difference between the real-time superheat and the initial superheat is calculated. When the pressure difference is greater than or equal to the preset pressure difference threshold, the defrosting mode is executed and the defrosting auxiliary trigger type is recorded as pressure difference trigger type. When the superheat difference is less than or equal to the preset superheat difference threshold, the defrosting mode is executed and the defrosting auxiliary trigger type is recorded as superheat trigger type. When the pressure difference is greater than or equal to the preset pressure difference threshold and the superheat difference is less than or equal to the preset superheat difference threshold, the defrosting mode is executed and the defrosting auxiliary trigger type is recorded as pressure difference priority trigger type.

[0012] In the defrosting control method, the heat pump air conditioning unit further includes a four-way valve. The compressor, indoor heat exchanger, and outdoor heat exchanger switch between defrosting mode and heating mode through the four-way valve. If it is determined that defrosting mode is to be executed, the connection between the compressor, indoor heat exchanger, and outdoor heat exchanger is adjusted. The high-temperature and high-pressure refrigerant discharged from the compressor flows through the outdoor heat exchanger for heating and defrosting, and the defrosting operation timer is started. This includes: when the defrosting mode is executed, controlling the fan of the outdoor heat exchanger to stop running, and controlling the four-way valve to de-energize and reverse, so that the high-temperature and high-pressure refrigerant discharged from the compressor enters the outdoor heat exchanger for heating and defrosting; disabling the low-pressure protection function of the compressor, resetting and starting the defrosting operation counter, and starting to accumulate the defrosting operation time.

[0013] In the defrosting control method, determining whether to exit the defrosting mode based on the defrosting auxiliary trigger type and the cumulative defrosting runtime includes: when the cumulative defrosting runtime is greater than or equal to a preset cumulative defrosting duration threshold, and the defrosting auxiliary trigger type is differential pressure trigger type or differential pressure priority trigger type, if the real-time detected outdoor heat exchanger temperature is greater than or equal to a preset defrosting end temperature threshold, or the real-time wind pressure is less than or equal to the initial wind pressure, then it is determined to exit the defrosting mode; when the cumulative defrosting runtime is greater than or equal to a preset cumulative defrosting duration threshold, and the defrosting auxiliary trigger type is superheat trigger type, if the real-time detected outdoor heat exchanger temperature is greater than or equal to a preset defrosting end temperature threshold, then it is determined to exit the defrosting mode.

[0014] In the defrosting control method, if it is determined that the defrosting mode has been exited, the connection between the compressor, the indoor heat exchanger, and the outdoor heat exchanger is adjusted to allow the heat pump air conditioning unit to resume the heating mode. This includes: when the defrosting mode has been exited, controlling the fan of the outdoor heat exchanger to start and controlling the four-way valve to be energized and reversed; and disabling the low-pressure protection function of the compressor to allow the heat pump air conditioning unit to resume the heating mode.

[0015] The present invention also provides a heat pump air conditioning unit, wherein the heat pump air conditioning unit adopts any of the defrosting control methods described above to achieve defrosting control, and the heat pump air conditioning unit includes a controller and a refrigeration cycle loop and sensor assembly respectively electrically connected to the controller.

[0016] In the heat pump air conditioning unit, the refrigeration cycle loop includes a compressor, a four-way valve, an indoor heat exchanger, a throttling device, and an outdoor heat exchanger connected in sequence and sealed. The four ports of the four-way valve are respectively connected to the exhaust port of the compressor, the suction port of the compressor, the refrigerant inlet of the indoor heat exchanger, and the refrigerant inlet of the outdoor heat exchanger. The compressor and the four-way valve are electrically connected to the controller. The sensor assembly includes a first temperature sensor, a first pressure sensor, a second temperature sensor, and a second pressure sensor, which are electrically connected to the controller. The first temperature sensor is located at the bend of any heat exchange tube on the coil end face of the outdoor heat exchanger, or at the middle fin of the non-wind-facing coil of the outdoor heat exchanger. The first pressure sensor is located at the middle position of the non-wind-facing coil of the outdoor heat exchanger. The second temperature sensor and the second pressure sensor are both located on the horizontal refrigerant pipe at the suction port of the compressor, and the second temperature sensor is located downstream of the second pressure sensor.

[0017] Beneficial effects: This invention provides a defrosting control method. The defrosting monitoring phase is initiated based on the outdoor heat exchanger temperature. Initial air pressure and initial superheat are simultaneously locked as baseline parameters. Combined with basic triggering conditions of temperature and duration, a dual-auxiliary verification mechanism using air-side pressure difference and refrigerant-side superheat difference determines whether defrosting should be initiated. Finally, differentiated defrosting exit conditions are applied based on different auxiliary triggering types. Compared to existing single-parameter control methods, this method comprehensively evaluates the frosting state from two independent dimensions: airflow resistance and refrigerant heat exchange capacity. This avoids misjudgments caused by factors such as heat exchanger blockage, insufficient refrigerant, and sensor installation deviations, significantly improving the accuracy and reliability of defrosting control. It can meet the high stability and high safety requirements of air-source heat pump air conditioning units in special scenarios such as nuclear power plants. Attached Figure Description

[0018] Figure 1 The logic flowchart of the defrosting control method provided by the present invention; Figure 2 The system structure diagram of the heat pump air conditioning unit provided by the present invention; Explanation of key component symbols: 1-Controller, 21-Compressor, 22-Four-way valve, 23-Indoor heat exchanger, 24-Throttling device, 25-Outdoor heat exchanger, 31-First temperature sensor, 32-First pressure sensor, 33-Second temperature sensor, 34-Second pressure sensor. Detailed Implementation

[0019] This invention provides a defrosting control method and a heat pump air conditioning unit. To make the objectives, technical solutions and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] In the description of this invention, it should be understood that the terms "installation" and "connection" should be interpreted broadly, and those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] like Figure 1 As shown, the present invention provides a defrosting control method, which is implemented based on a heat pump air conditioning unit. The heat pump air conditioning unit includes a compressor 21, an indoor heat exchanger 23, and an outdoor heat exchanger 25 connected in sequence to realize a cooling and heating cycle. The defrosting control method includes: 101. When the heat pump air conditioning unit is in heating mode, the temperature of the outdoor heat exchanger 25 is monitored in real time to determine whether the defrosting monitoring stage has been entered. 102. If it is determined that the defrosting monitoring stage has been entered, the initial wind pressure and initial superheat of the outdoor heat exchanger 25 are obtained, and the monitoring timer is started. 103. Based on the real-time temperature and cumulative monitoring duration of the outdoor heat exchanger 25, determine whether the preset defrosting basic trigger conditions are met. 104. If the preset defrosting basic trigger conditions are met, the real-time wind pressure and initial wind pressure, and the real-time superheat and initial superheat of the outdoor heat exchanger 25 are compared to determine whether to execute the defrosting mode and the defrosting auxiliary trigger type is recorded. 105. If it is determined that the defrosting mode is to be executed, the connection between the compressor 21, the indoor heat exchanger 23 and the outdoor heat exchanger 25 is adjusted, and the high-temperature and high-pressure refrigerant discharged from the compressor 21 is used to flow through the outdoor heat exchanger 25 for heating and defrosting, and the defrosting operation timer is started. 106. Based on the defrost assist trigger type and the cumulative defrost runtime, determine whether to exit the defrost mode; 107. If it is determined that the defrosting mode has been exited, adjust the connection between the compressor 21, the indoor heat exchanger 23 and the outdoor heat exchanger 25 to restore the heat pump air conditioning unit to the heating mode.

[0022] Existing defrosting control methods generally use a single parameter or a simple combination of parameters for judgment, which has inherent limitations: timed defrosting methods cannot adapt to changes in the actual frost rate, inevitably leading to ineffective defrosting or incomplete defrosting; temperature-based defrosting methods are easily affected by non-frost factors, resulting in misjudgments; fuzzy control methods rely on human experience and have fixed rules, making them unable to adapt to complex working conditions.

[0023] The defrosting control method disclosed in this invention, through phased control logic, first divides the operation process into a normal heating stage and a defrosting monitoring stage. During the non-monitoring stage, no complex calculations are required, reducing the operating load of the control system. The basic triggering condition, combining temperature and duration parameters, can filter out interference caused by short-term temperature fluctuations, preventing accidental entry into the defrosting program. A dual-auxiliary verification mechanism reflects the degree of frost from two independent dimensions: the air side and the refrigerant side. Defrosting is triggered when either dimension reaches a critical value, ensuring that frost is not left unremoved. Differentiated defrosting exit conditions can adjust the defrosting duration according to the actual frost thickness, ensuring thorough defrosting while avoiding excessive defrosting that could lead to a decrease in heating performance. In short, the method disclosed in this invention, through multi-level and multi-dimensional control logic, achieves precise control of the defrosting process, effectively improving the reliability and heating efficiency of the unit and extending the service life of core components.

[0024] Furthermore, in this embodiment of the invention, the heat pump air conditioning unit further includes a first temperature sensor 31, which is disposed at the bend of the heat exchange tube on the coil end face of the outdoor heat exchanger 25, or at the middle fin on the non-windward side of the outdoor heat exchanger 25; the step of real-time detection of the temperature of the outdoor heat exchanger 25 when the heat pump air conditioning unit is in heating mode to determine whether to enter the defrost monitoring stage includes: 201. When the heat pump air conditioning unit is in heating mode, the temperature of the outdoor heat exchanger 25 is obtained in real time from the first temperature sensor 31. 202. When the temperature of the outdoor heat exchanger 25 is less than or equal to the preset start-up monitoring threshold, the defrosting monitoring stage is determined to be entered. In this embodiment, the first temperature sensor 31 is located at the bend of the heat exchange tube on the coil end face of the outdoor heat exchanger 25, or at the middle fin on the non-windward side of the outdoor heat exchanger 25. This installation position can avoid temperature measurement deviation caused by direct impact of airflow on the windward side, and at the same time, it can reflect the overall average temperature of the outdoor heat exchanger 25, reducing the impact of temperature differences between different heat exchange tubes caused by uneven liquid distribution on the measurement results. The preset start-up monitoring threshold is typically 3°C. This value is set above the frosting critical temperature, which can enter the monitoring state in advance before the frosting process begins, ensuring accurate detection in the early stage of frosting. When the temperature of the outdoor heat exchanger 25 drops below the start-up monitoring threshold, it is determined that the defrosting monitoring stage has been entered, and the subsequent parameter acquisition and timing process is started.

[0025] Further, in this embodiment of the invention, the heat pump air conditioning unit also includes a first pressure sensor 32 disposed at the middle position of the non-windward side of the outdoor heat exchanger 25, a second temperature sensor 33 disposed on the suction port pipe of the compressor 21, and a second pressure sensor 34 disposed on the suction port pipe of the compressor 21; if it is determined that the defrosting monitoring stage has been entered, the initial air pressure and initial superheat of the outdoor heat exchanger 25 are obtained, and the monitoring timing is started, including: 301. When it is determined that the defrosting monitoring stage has been entered, the initial wind pressure fed back by the first pressure sensor 32, the suction temperature of the compressor 21 fed back by the second temperature sensor 33, and the suction pressure of the compressor 21 fed back by the second pressure sensor 34 are obtained. 302. Obtain the refrigerant saturation temperature corresponding to the suction pressure of the compressor 21, and calculate the initial superheat based on the suction temperature of the compressor 21 and the refrigerant saturation temperature; 303. Reset and start the defrost monitoring timer to begin accumulating monitoring time; In this embodiment, the initial superheat is calculated by subtracting the refrigerant saturation temperature corresponding to the compressor 21 suction pressure from the compressor 21 suction temperature. The refrigerant saturation temperature corresponding to the compressor 21 suction pressure can be obtained by consulting the physical property parameter table of the corresponding refrigerant. Since the air pressure and superheat of the outdoor heat exchanger 25 are not fixed values, they will change significantly with various non-frost factors such as ambient temperature, unit operating load, and fan speed. If a fixed preset value is used as the judgment benchmark, the calculated results of the pressure difference and superheat difference will not accurately reflect the actual changes caused by frost when the environmental conditions or operating conditions change, which is very easy to cause misjudgment. By locking the initial air pressure and initial superheat as the benchmark when entering the defrost monitoring stage, the difference in benchmark parameters under different ambient temperatures and different operating loads can be eliminated, ensuring that the pressure difference and superheat difference obtained in subsequent calculations are only caused by fin frost, thereby greatly improving the accuracy and reliability of frost degree judgment. By resetting and starting the defrost monitoring timer, the time from entering the monitoring stage to meeting the basic triggering conditions can be accurately recorded, providing a time dimension basis for judging the degree of frost.

[0026] Furthermore, in this embodiment of the invention, the determination of whether the preset defrosting basic triggering conditions are met based on the real-time detected temperature and cumulative monitoring duration of the outdoor heat exchanger 25 includes: 401. Obtain the preset critical temperature T for frost risk and the preset cumulative monitoring time threshold X1; 402. When the temperature of the outdoor heat exchanger 25 monitored in real time is ≤-T and the cumulative monitoring time is ≥X1, the defrosting trigger condition is determined to be met. In this embodiment, the preset critical temperature for frost risk is typically 1°C, which is set slightly higher than 0°C. When the temperature of the outdoor heat exchanger 25 drops to -1°C or below, the fin surface has obvious frost conditions. The preset cumulative monitoring time threshold is typically 30 minutes. This value setting can avoid false triggering caused by short-term low temperature fluctuations, ensure that the frost process has enough development time, and prevent frequent entry into the defrosting program. Only when the temperature of the outdoor heat exchanger 25 is below the critical temperature for the risk of frosting below zero, and the cumulative monitoring time reaches the cumulative monitoring time threshold, is it determined that the basic defrosting trigger condition is met, and the process proceeds to the subsequent auxiliary verification stage.

[0027] Furthermore, in this embodiment of the invention, if the preset defrosting basic triggering conditions are met, the system determines whether to execute the defrosting mode by comparing the real-time wind pressure and initial wind pressure, and the real-time superheat and initial superheat of the outdoor heat exchanger 25, and records the defrosting auxiliary triggering type, including: 501. When the preset defrosting basic trigger conditions are met, the real-time wind pressure fed back by the first pressure sensor 32 is obtained, and the real-time superheat is calculated based on the real-time compressor 21 suction temperature fed back by the second temperature sensor 33 and the real-time compressor 21 suction pressure fed back by the second pressure sensor 34. 502. Calculate the pressure difference between the real-time wind pressure and the initial wind pressure, and calculate the superheat difference between the real-time superheat and the initial superheat. 503. When the differential pressure is greater than or equal to the preset differential pressure threshold, the defrosting mode is determined to be executed, and the defrosting auxiliary trigger type is recorded as differential pressure trigger type. 504. When the overheating difference is less than or equal to the preset overheating difference threshold, the defrosting mode is executed, and the defrosting auxiliary trigger type is recorded as overheating trigger type. 505. When the differential pressure is greater than or equal to the preset differential pressure threshold and the superheat difference is less than or equal to the preset superheat difference threshold, the defrosting mode is determined to be executed, and the defrosting auxiliary trigger type is recorded as differential pressure priority trigger type. In this embodiment, the difference between real-time wind pressure and initial wind pressure can directly reflect the degree of increase in airflow resistance caused by fin frosting, and the difference between real-time superheat and initial superheat can reflect the degree of decrease in evaporator heat exchange capacity; the preset differential pressure threshold is typically 80 Pa, which corresponds to the critical value that the fin frosting thickness reaches, affecting heat exchange efficiency; the preset superheat difference threshold is typically 3 °C, which corresponds to the degree to which the evaporator heat exchange capacity decreases to the point where defrosting is required; Under normal operating conditions of a heat pump air conditioning unit, only one auxiliary condition will usually be met. This is because during the frosting process, the rate of increase in air-side resistance and the rate of decrease in refrigerant-side heat exchange capacity are usually different. For example, when the frost on the heat exchanger surface is thin but evenly distributed, it may first lead to a significant decrease in heat exchange capacity, triggering the superheat condition. When the frost is mainly concentrated in the fin gaps, causing a sharp increase in airflow resistance, it may first trigger the pressure difference condition. When the frost is thick and lasts for a long time, the frost layer not only severely hinders airflow but also significantly reduces heat exchange capacity, both auxiliary conditions will be met simultaneously.

[0028] Furthermore, in this embodiment of the invention, the heat pump air conditioning unit further includes a four-way valve 22, through which the compressor 21, the indoor heat exchanger 23, and the outdoor heat exchanger 25 switch between defrosting mode and heating mode; if it is determined that defrosting mode is to be executed, the connection between the compressor 21, the indoor heat exchanger 23, and the outdoor heat exchanger 25 is adjusted, and the high-temperature and high-pressure refrigerant discharged from the compressor 21 flows through the outdoor heat exchanger 25 for heating and defrosting, and the defrosting operation timer is started, including: 601. When the defrosting mode is executed, the fan of the outdoor heat exchanger 25 is stopped and the four-way valve 22 is de-energized and reversed, so that the high-temperature and high-pressure refrigerant discharged by the compressor 21 enters the outdoor heat exchanger 25 for heating and defrosting. 602. Disable the low-pressure protection function of compressor 21, reset and start the defrost operation counter, and begin accumulating the defrost operation time; In this embodiment, when the defrosting mode is executed, the fan of the outdoor heat exchanger 25 is stopped, which can prevent cold air from carrying away heat through the outdoor heat exchanger 25, improve defrosting efficiency, and shorten defrosting time; at the same time, the four-way valve 22 is de-energized and reversed, which can change the flow path of the refrigerant, so that the high-temperature and high-pressure refrigerant discharged by the compressor 21 directly enters the outdoor heat exchanger 25, and melts the frost layer on the fin surface through condensation and heat release. In defrost mode, the indoor heat exchanger 23 is used as an evaporator, and the indoor fan stops running. The refrigerant evaporation rate decreases sharply, and the suction pressure of the compressor 21 drops rapidly, which can easily trigger the low-pressure protection and cause defrosting to stop. The preset low-pressure protection shielding time of the compressor 21 is typically 5 minutes. This value is slightly longer than the maximum time required for system pressure stabilization, leaving sufficient safety margin. This ensures that the defrosting process starts smoothly and enters a stable operating state, while preventing damage to the compressor 21 due to prolonged shielding of the protection function. The time required for system pressure stabilization is affected by factors such as the unit's cooling capacity, refrigerant charge, and ambient temperature. For medium-sized safety-grade air source heat pump units commonly used in nuclear power plants, this time is usually 3-4 minutes. By resetting and starting the defrost operation counter, the duration of the defrost process can be accurately recorded, providing a basis for determining when to exit defrost.

[0029] Furthermore, in this embodiment of the invention, determining whether to exit the defrost mode based on the defrost assist trigger type and the cumulative defrost runtime includes: 701. When the cumulative defrosting runtime is greater than or equal to the preset cumulative defrosting runtime threshold, and the defrosting auxiliary triggering type is differential pressure triggering type or differential pressure priority triggering type, if the real-time detected temperature of the outdoor heat exchanger 25 is greater than or equal to the preset defrosting end temperature threshold, or the real-time wind pressure is less than or equal to the initial wind pressure, then it is determined to exit the defrosting mode. 702. When the cumulative defrosting runtime is greater than or equal to the preset cumulative defrosting runtime threshold, and the defrosting auxiliary trigger type is the overheat trigger type, if the real-time detected temperature of the outdoor heat exchanger 25 is greater than or equal to the preset defrosting end temperature threshold, then it is determined to exit the defrosting mode. In this embodiment, the preset defrosting cumulative duration threshold is typically 15 minutes. This value is the longest protection duration of the defrosting process, which can ensure that even if the sensor malfunctions, the defrosting program can be forcibly terminated to avoid excessive defrosting leading to a significant drop in indoor temperature and damage to the compressor 21. The preset defrosting end temperature threshold is typically 15°C. This value has been experimentally verified to ensure that the frost layer on the fin surface is completely melted and the heat exchanger surface temperature rises to a level that will not immediately re-frost. For differential pressure triggered or differential pressure priority triggered defrosting, a dual exit judgment logic is adopted. When the real-time detected outdoor heat exchanger 25 temperature reaches 15℃, it indicates that the temperature of the outdoor heat exchanger 25 is high enough to completely melt the attached frost layer. When the real-time wind pressure returns to below the initial wind pressure, it indicates that the frost layer between the fins has been completely removed and the airflow resistance has returned to the state before frosting. Defrosting is considered complete if either of the two conditions is met. This design can cover different defrosting states and avoid incomplete or excessive defrosting that may result from judging based on a single condition. For overheat-triggered defrosting, which is typically used when the frost is thin and evenly distributed, the defrosting can be completely ensured simply by judging the temperature, without the need for additional air pressure judgment. This simplifies the control logic and reduces the complexity of the control system.

[0030] Further, in this embodiment of the invention, the step of adjusting the connection between the compressor 21, the indoor heat exchanger 23, and the outdoor heat exchanger 25 to restore the heat pump air conditioning unit to the heating mode if it is determined that the defrosting mode has been exited includes: 801. When exiting the defrost mode, control the start of the fan of the outdoor heat exchanger 25 and control the four-way valve 22 to be energized and reversed; 802. Remove the shielding of the low-pressure protection function of compressor 21 to allow the heat pump air conditioning unit to resume the heating mode; In this embodiment, when exiting the defrost mode, the fan of the outdoor heat exchanger 25 is started, which can restore the air circulation of the outdoor heat exchanger 25 and provide conditions for evaporative heat exchange in the heating mode; at the same time, the four-way valve 22 is energized and reversed to switch the refrigerant flow path back to the heating mode, so that the high-temperature and high-pressure refrigerant enters the indoor heat exchanger 23 to release heat; and the shielding of the low-pressure protection function of the compressor 21 is released, restoring the normal protection mechanism of the compressor 21 and preventing the heat pump air conditioning unit from being damaged due to low-pressure abnormality during heating operation.

[0031] like Figure 2 As shown, the present invention also provides a heat pump air conditioning unit, wherein the heat pump air conditioning unit adopts any of the defrosting control methods described above to achieve defrosting control, and the heat pump air conditioning unit includes a controller 1 and a refrigeration cycle loop and sensor assembly respectively electrically connected to the controller 1.

[0032] In this embodiment, the controller 1 serves as the control core of the unit and adopts a programmable logic controller 1 that meets the safety requirements of nuclear power plants. The pre-stored control logic inside corresponds to the defrosting control method described above, including the defrosting monitoring phase start logic, initial parameter acquisition and locking logic, defrosting basic trigger condition judgment logic, dual auxiliary verification trigger logic, defrosting mode execution logic, differentiated defrosting exit logic, and system recovery logic. The controller 1 is electrically connected to each actuator in the refrigeration cycle loop and each detection component in the sensor assembly, and is used to receive detection signals fed back by the sensor assembly, execute preset control logic, and send control commands to the actuators in the refrigeration cycle loop. The refrigeration cycle loop is used to realize the circulation of refrigerant and complete the transfer and exchange of heat; The sensor assembly is used to collect parameters such as temperature and pressure during the unit's operation in real time and convert them into electrical signals for transmission to controller 1.

[0033] like Figure 2 As shown, in some embodiments, the refrigeration cycle circuit includes a compressor 21, a four-way valve 22, an indoor heat exchanger 23, a throttling device 24, and an outdoor heat exchanger 25, which are sequentially and sealed together. The four ports of the four-way valve 22 are respectively connected to the discharge port of the compressor 21, the suction port of the compressor 21, the refrigerant inlet of the indoor heat exchanger 23, and the refrigerant inlet of the outdoor heat exchanger 25. The compressor 21 and the four-way valve 22 are electrically connected to the controller 1. The sensor assembly includes a first temperature sensor 31 and a first pressure sensor 32, which are electrically connected to the controller 1. The compressor 21 includes a force sensor 32, a second temperature sensor 33, and a second pressure sensor 34. The first temperature sensor 31 is located at the bend of any heat exchange tube on the coil end face of the outdoor heat exchanger 25, or at the middle fin of the non-wind-facing coil of the outdoor heat exchanger 25. The first pressure sensor 32 is located at the middle position of the non-wind-facing coil of the outdoor heat exchanger 25. The second temperature sensor 33 and the second pressure sensor 34 are both located on the horizontal refrigerant pipe at the suction port of the compressor 21, and the second temperature sensor 33 is located downstream of the second pressure sensor 34.

[0034] In this embodiment, the refrigeration cycle loop includes a compressor 21, a four-way valve 22, an indoor heat exchanger 23, a throttling device 24, and an outdoor heat exchanger 25. All components are connected in a sealed manner via refrigerant pipes through welding, ensuring no leakage of refrigerant during circulation within the loop. The four ports of the four-way valve 22 are respectively connected to the exhaust port of the compressor 21, the suction port of the compressor 21, the refrigerant inlet of the indoor heat exchanger 23, and the refrigerant inlet of the outdoor heat exchanger 25. In heating mode, the refrigerant flow direction... The refrigerant flows from the compressor 21 discharge port to the indoor heat exchanger 23 via the four-way valve 22. After condensation and heat release, it is throttled and depressurized by the throttling device 24 before entering the outdoor heat exchanger 25 for evaporation and heat absorption. Then, it returns to the compressor 21 suction port via the four-way valve 22. In defrost mode, the four-way valve 22 is de-energized and reversed, and the refrigerant flows from the compressor 21 discharge port to the outdoor heat exchanger 25 via the four-way valve 22. After condensation and heat release for defrosting, it is throttled and depressurized by the throttling device 24 before entering the indoor heat exchanger 23 for evaporation and heat absorption. Then, it returns to the compressor 21 suction port via the four-way valve 22.

[0035] The sensor assembly includes a first temperature sensor 31, a first pressure sensor 32, a second temperature sensor 33, and a second pressure sensor 34. The first temperature sensor 31 is located at the bend of any heat exchange tube on the coil end face of the outdoor heat exchanger 25, or at the middle fin of the non-wind-facing coil of the outdoor heat exchanger 25. This avoids temperature measurement fluctuations caused by direct impact from high-speed airflow on the windward side, and reflects the overall average temperature of the heat exchanger, reducing the impact of local temperature differences caused by uneven liquid distribution on the measurement results. The first pressure sensor 32 is located in the middle of the non-wind-facing coil of the outdoor heat exchanger 25, accurately detecting the average air pressure after the air flows through the entire heat exchanger, avoiding pressure measurement errors caused by turbulent airflow at the edges. The second temperature sensor 33 and the second pressure sensor 34 are both located on the horizontal refrigerant pipe at the suction port of the compressor 21, with the second temperature sensor 33 located downstream of the second pressure sensor 34. This installation position avoids the disturbance caused by the pressure sensor to the refrigerant flow affecting the accuracy of temperature measurement, ensuring the accuracy of superheat calculation.

[0036] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A defrosting control method, characterized in that, The defrosting control method is implemented based on a heat pump air conditioning unit, which includes a compressor, an indoor heat exchanger, and an outdoor heat exchanger connected in sequence to achieve a cooling and heating cycle; the defrosting control method includes: When the heat pump air conditioning unit is in heating mode, the temperature of the outdoor heat exchanger is monitored in real time to determine whether the defrosting monitoring stage has been entered. If the defrosting monitoring phase is determined, the initial wind pressure and initial superheat of the outdoor heat exchanger are obtained, and the monitoring timer is started. Based on the real-time temperature of the outdoor heat exchanger and the cumulative monitoring time, it is determined whether the preset defrosting basic trigger conditions are met. If the preset defrost basic trigger conditions are met, the system will compare the real-time wind pressure and initial wind pressure, and the real-time superheat and initial superheat of the outdoor heat exchanger to determine whether to execute the defrost mode and record the defrost auxiliary trigger type. If the defrost mode is determined to be executed, the connection between the compressor, the indoor heat exchanger and the outdoor heat exchanger is adjusted, and the high-temperature and high-pressure refrigerant discharged from the compressor flows through the outdoor heat exchanger to heat and defrost, and the defrost operation timer is started. Based on the defrost assist trigger type and the cumulative defrost runtime, determine whether to exit defrost mode; If the defrosting mode is exited, the connection between the compressor, indoor heat exchanger and outdoor heat exchanger is adjusted to restore the heat pump air conditioning unit to the heating mode.

2. The defrosting control method according to claim 1, characterized in that, The heat pump air conditioning unit further includes a first temperature sensor, which is located at the bend of the heat exchange tube on the coil end face of the outdoor heat exchanger, or at the middle fin on the non-wind-facing side of the outdoor heat exchanger; when the heat pump air conditioning unit is in heating mode, the temperature of the outdoor heat exchanger is monitored in real time to determine whether the defrosting monitoring stage has been entered, including: When the heat pump air conditioning unit is in heating mode, it obtains the temperature of the outdoor heat exchanger in real time from the first temperature sensor. When the temperature of the outdoor heat exchanger is less than or equal to the preset start-up monitoring threshold, the defrosting monitoring phase is initiated.

3. The defrosting control method according to claim 1, characterized in that, The heat pump air conditioning unit also includes a first pressure sensor located at the center of the non-windward side of the outdoor heat exchanger, a second temperature sensor located on the compressor suction port pipe, and a second pressure sensor located on the compressor suction port pipe; if it is determined that the defrosting monitoring stage has been entered, the initial air pressure and initial superheat of the outdoor heat exchanger are obtained, and the monitoring timing is started, including: When the defrosting monitoring stage is determined, the initial air pressure fed back by the first pressure sensor, the compressor suction temperature fed back by the second temperature sensor, and the compressor suction pressure fed back by the second pressure sensor are obtained. Obtain the refrigerant saturation temperature corresponding to the compressor suction pressure, and calculate the initial superheat based on the compressor suction temperature and the refrigerant saturation temperature; Reset and start the defrost monitoring timer to begin accumulating monitoring time.

4. The defrosting control method according to claim 1, characterized in that, The determination of whether the preset defrosting basic trigger conditions are met is based on the real-time detected temperature and cumulative monitoring duration of the outdoor heat exchanger, including: Obtain the preset critical temperature T for frost risk and the preset cumulative monitoring time threshold X1; When the temperature of the outdoor heat exchanger monitored in real time is ≤-T and the cumulative monitoring time is ≥X1, the defrosting trigger condition is determined to be met.

5. The defrosting control method according to claim 3, characterized in that, If the preset defrosting basic trigger conditions are met, the system compares the real-time wind pressure and initial wind pressure, and the real-time superheat and initial superheat of the outdoor heat exchanger to determine whether to execute the defrosting mode and records the defrosting auxiliary trigger type, including: When the preset defrosting basic trigger conditions are met, the real-time wind pressure fed back by the first pressure sensor is obtained, and the real-time superheat is calculated based on the real-time compressor suction temperature fed back by the second temperature sensor and the real-time compressor suction pressure fed back by the second pressure sensor. Calculate the pressure difference between the real-time wind pressure and the initial wind pressure, and calculate the superheat difference between the real-time superheat and the initial superheat; When the differential pressure is greater than or equal to the preset differential pressure threshold, the defrosting mode is determined to be executed, and the defrosting auxiliary trigger type is recorded as differential pressure trigger type. When the overheating difference is less than or equal to the preset overheating difference threshold, the defrosting mode is executed, and the defrosting auxiliary trigger type is recorded as overheating trigger type. When the differential pressure is greater than or equal to the preset differential pressure threshold and the superheat difference is less than or equal to the preset superheat difference threshold, the defrosting mode is determined to be executed, and the defrosting auxiliary trigger type is recorded as differential pressure priority trigger type.

6. The defrosting control method according to claim 1, characterized in that, The heat pump air conditioning unit also includes a four-way valve, through which the compressor, indoor heat exchanger, and outdoor heat exchanger switch between defrosting mode and heating mode. If defrosting mode is selected, the connection between the compressor, indoor heat exchanger, and outdoor heat exchanger is adjusted, utilizing the high-temperature, high-pressure refrigerant discharged from the compressor to heat and defrost the outdoor heat exchanger, and the defrosting operation timer is started, including: When the defrost mode is executed, the fan of the outdoor heat exchanger is stopped and the four-way valve is de-energized and reversed, so that the high-temperature and high-pressure refrigerant discharged by the compressor enters the outdoor heat exchanger for heating and defrosting. Disable the compressor's low-pressure protection function, reset and start the defrost operation counter, and begin accumulating defrost operation time.

7. The defrosting control method according to claim 5, characterized in that, The step of determining whether to exit defrost mode based on the defrost assist trigger type and cumulative defrost runtime includes: When the cumulative defrosting runtime is greater than or equal to the preset cumulative defrosting runtime threshold, and the defrosting auxiliary trigger type is differential pressure trigger type or differential pressure priority trigger type, if the real-time detected outdoor heat exchanger temperature is greater than or equal to the preset defrosting end temperature threshold, or the real-time wind pressure is less than or equal to the initial wind pressure, then it is determined to exit the defrosting mode. When the cumulative defrosting runtime is greater than or equal to the preset cumulative defrosting runtime threshold, and the defrosting auxiliary trigger type is overheat trigger type, if the real-time detected temperature of the outdoor heat exchanger is greater than or equal to the preset defrosting end temperature threshold, then it is determined to exit the defrosting mode.

8. The defrosting control method according to claim 6, characterized in that, If it is determined that the defrosting mode has been exited, the connection between the compressor, the indoor heat exchanger, and the outdoor heat exchanger is adjusted to allow the heat pump air conditioning unit to resume operating in heating mode, including: When the defrosting mode is exited, the fan of the outdoor heat exchanger is started, and the four-way valve is energized and reversed. Remove the shielding of the compressor's low-pressure protection function to allow the heat pump air conditioning unit to resume operating in heating mode.

9. A heat pump air conditioning unit, characterized in that, The heat pump air conditioning unit adopts the defrosting control method as described in any one of claims 1-8 to achieve defrosting control. The heat pump air conditioning unit includes a controller and a refrigeration cycle loop and sensor assembly that are electrically connected to the controller.

10. The heat pump air conditioning unit according to claim 9, characterized in that, The refrigeration cycle circuit includes a compressor, a four-way valve, an indoor heat exchanger, a throttling device, and an outdoor heat exchanger, which are sequentially and sealed together. The four ports of the four-way valve are respectively connected to the discharge port of the compressor, the suction port of the compressor, the refrigerant inlet of the indoor heat exchanger, and the refrigerant inlet of the outdoor heat exchanger. The compressor and the four-way valve are electrically connected to the controller. The sensor assembly includes a first temperature sensor, a first pressure sensor, a second temperature sensor, and a second pressure sensor, which are electrically connected to the controller. The first temperature sensor is located at the bend of any heat exchange tube on the coil end face of the outdoor heat exchanger, or at the middle fin of the non-wind-facing coil of the outdoor heat exchanger. The first pressure sensor is located at the middle position of the non-wind-facing coil of the outdoor heat exchanger. The second temperature sensor and the second pressure sensor are both located on the horizontal refrigerant pipe at the suction port of the compressor, and the second temperature sensor is located downstream of the second pressure sensor.

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