Heat pump system with air side heat exchanger defrosting control function

Abstract

The invention relates to a heat pump system with air side heat exchanger defrosting control, which is characterized in that when the heat pump system is defrosted for the first time, when the environment temperature is lower than an environment temperature threshold value, a dynamic coil pipe temperature threshold value is set according to an interval where the environment temperature is located, and when the coil pipe temperature is lower than the coil pipe temperature threshold value, the maximum fin pressure detected at the current moment is collected; collecting the average pressure of fins in a specific coil pipe temperature interval to obtain a thick frost pressure threshold P2 and a thin frost pressure threshold P3; and when the heat pump system is not defrosted for the first time and the environment temperature or the environment humidity meets specific conditions, secondary judgment is carried out in combination with the fin pressure P and the actual temperature Tr of the user, and it is ensured that the defrosting requirement and the comfort level of the user are balanced. According to the heat pump system, the pressure characteristics are automatically learned after first defrosting, the triggering conditions are dynamically adjusted in combination with the environment temperature and humidity and the user requirements, and accurate on-demand defrosting is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pumps, and particularly to a heat pump system with defrost control for an air-side heat exchanger. Background Art

[0002] When a traditional heat pump unit determines defrosting of the air-side heat exchanger, it usually indirectly judges whether the fins of the air-side heat exchanger are frosted by means such as coil temperature, fan speed, and changes in the internal pressure of the system. This indirect judgment method often leads to situations where the heat pump unit defrosts without frost or operates at a high load with frost, causing problems such as large fluctuations in the domestic hot water temperature at the user's home and increased electricity costs. The user experience is poor, and it will also reduce the service life of the unit and increase the maintenance risk. At the same time, it is impossible to dynamically adjust the defrost strategy according to the frost layer thickness, relying on indirect parameters for judgment, which is prone to misjudgment, resulting in unnecessary defrost operations or delayed defrosting, and increasing system energy consumption.

[0003] Therefore, there is an urgent need to provide a more accurate and intelligent defrost control method, by directly monitoring the frost layer thickness on the fins, reducing the situations of defrosting without frost and operating at a high load with frost, and improving the user experience and the service life of the unit. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the defects or deficiencies of the prior art, and provide a heat pump system with defrost control for an air-side heat exchanger 15.

[0005] A heat pump system with defrost control for an air-side heat exchanger includes a compressor, a four-way valve, a water-side heat exchanger, a throttling component, and an air-side heat exchanger connected in sequence by a refrigerant circulation pipeline; a first temperature and humidity sensor for obtaining the environmental temperature and humidity, and a first temperature sensor for obtaining the water temperature inside the water-side heat exchanger; the air-side heat exchanger includes a coil and fins, a second temperature sensor arranged on the coil, a third temperature sensor and a pressure sensor arranged on the fins; it further includes a controller, the controller is electrically connected or communicatively connected to the temperature and humidity sensor, each temperature sensor, and the pressure sensor, and the controller controls the defrosting of the air-side heat exchanger in the following manner:

[0006] Obtain the defrosting history of the current heat pump system during heating startup, and judge whether the number of defrosting times is greater than or equal to 1:

[0007] If not, obtain the environmental temperature Ta and the coil temperature Tp, and judge whether the environmental temperature Ta and the coil temperature Tp simultaneously meet the first defrost startup condition: if so, control the four-way valve to change direction for defrosting, collect the defrosting time t and collect the fin pressure P within a specific coil temperature range until the first defrost exit condition is met to exit defrosting, and obtain the thick frost pressure threshold P2 and the defrost completion pressure threshold P4 based on the average pressure;

[0008] If it is yes, obtain the ambient temperature Ta and the ambient humidity RH, and determine whether any parameter of the ambient temperature Ta and the ambient humidity RH meets the non-first defrost start condition: If it is met, obtain the fin pressure P. When the fin pressure P is greater than the thick frost pressure threshold P2, control the four-way valve to reverse for defrosting, collect the defrosting time t, and exit the defrosting until the second defrost exit condition is met.

[0009] In one embodiment, the first defrost start condition set by the ambient temperature Ta and the coil temperature Tp is as follows:

[0010] The first defrost start condition is: 3°C < Ta < 10°C and Tp < -5°C;

[0011] The second defrost start condition is: -3°C < Ta ≤ 3°C and Tp < -3°C;

[0012] The third defrost start condition is: -10°C < Ta ≤ -3°C and Tp < -5°C;

[0013] The fourth defrost start condition is: Ta ≤ -10°C and Tp < -12°C.

[0014] In one embodiment, the thick frost pressure threshold P2 based on the average pressure is obtained in the following manner:

[0015] If the first defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -5°C ≤ TP < -3°C is stored as the thick frost pressure threshold P2;

[0016] If the second defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -3°C ≤ TP < 0°C is stored as the thick frost pressure threshold P2;

[0017] If the third defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -5°C ≤ TP < -3°C is stored as the thick frost pressure threshold P2;

[0018] If the fourth defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -12°C ≤ TP < -10°C is stored as the thick frost pressure threshold P2.

[0019] In one embodiment, the non-first defrost start condition set by any parameter of the ambient temperature Ta and the ambient humidity RH is as follows: Ta ≤ 2°C, or RH ≥ 70%.

[0020] In one embodiment, the thin frost pressure threshold P3 based on the average pressure is obtained in the following manner:

[0021] If the first defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -3°C ≤ Tp < 0°C is stored as the light frost pressure threshold P3;

[0022] If the second defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when 0°C ≤ TP < 3°C is stored as the light frost pressure threshold P3;

[0023] If the third defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -3°C ≤ Tp < 0°C is stored as the light frost pressure threshold P3;

[0024] If the fourth defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -10°C ≤ TP < -8°C is stored as the light frost pressure threshold P3.

[0025] In one embodiment, it further includes that when any one of the ambient temperature Ta and the ambient humidity RH satisfies the defrost start condition and the fin pressure P is less than the heavy frost pressure threshold P2, it is further determined whether the fin pressure P is greater than or equal to the light frost pressure threshold P3:

[0026] If so, the actual water temperature Tr is obtained, and the relationship between the actual water temperature Tr and the preset water temperature Tset is analyzed:

[0027] When the actual water temperature Tr is less than or equal to the difference between the preset water temperature Tset and the set water temperature hysteresis ΔTr, the fin pressure P is continuously monitored;

[0028] When the actual water temperature Tr is greater than the difference between the preset water temperature Tset and the set water temperature hysteresis ΔTr, the four-way valve is controlled to change direction for defrosting until the fin pressure P meets the defrost exit condition and exits the defrosting.

[0029] In one embodiment, the first defrost exit condition is as follows: the defrost time t is greater than or equal to 6 min, or the coil temperature Tp ≥ 15°C.

[0030] In one embodiment, the second defrost exit condition is as follows: the defrost time t is greater than or equal to 6 min, or the fin pressure P is less than the defrost completion pressure threshold P4.

[0031] In one embodiment, it further includes the update of the heavy frost pressure threshold P2, the light frost pressure threshold P3, and the defrost completion pressure threshold P4:

[0032] SA1 obtains the maximum fin pressure P1, calculates and obtains the heavy frost pressure difference ΔP1 between the heavy frost pressure threshold P2 and the maximum fin pressure P1, the light frost pressure difference ΔP2 between the light frost pressure threshold P3 and the maximum fin pressure P1, and the pressure difference ΔP3 between the defrost completion pressure threshold P4 and the maximum fin pressure P1;

[0033] SA2 obtains the fin pressure P and continuously calculates the pressure change rate △P of the fin within the set period M, and determines whether it exceeds the set pressure change threshold △P. set :

[0034] If it is, the average fin pressure P obtained in the corresponding set period M M replaces the maximum fin pressure P1 to obtain the corrected maximum fin pressure and calculates the corrected heavy frost pressure threshold according to the corrected maximum fin pressure and △P1. Replace the heavy frost pressure threshold with the corrected heavy frost pressure threshold P2; and calculate the corrected light frost pressure threshold according to the corrected maximum fin pressure and △P2. Replace the light frost pressure threshold with the corrected light frost pressure threshold P3; and calculate the corrected defrost completion pressure threshold according to the corrected maximum fin pressure and △P3. Replace the defrost completion pressure threshold with the corrected defrost completion pressure threshold P4.

[0035] In an embodiment, the set water temperature difference △Tr is 3°C.

[0036] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0037] Figure 1 is a schematic structural diagram of the heat pump system of the present invention;

[0038] Figure 2 is a flowchart of the defrost control method for the air-side heat exchanger in the present invention. Detailed Embodiment

[0039] The solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] As Figure 1 shown, a heat pump system 10 with defrost control of an air-side heat exchanger according to the present invention includes a compressor 11, a reversing four-way valve 12, a water-side heat exchanger 13, a throttling assembly 14, and an air-side heat exchanger 15 that are sequentially connected by a refrigerant circulation pipeline.

[0041] The water-side heat exchanger 13 is a heat exchanger that exchanges heat with the user side, and can exchange heat with the water of the user side to realize hot water supply.

[0042] The air-side heat exchanger 15 is a finned heat exchanger, which includes a coil pipe (not shown in the figure) and fins (not shown in the figure) provided on the outer wall of the coil pipe.

[0043] The heat pump system 10 further includes an ambient temperature and humidity sensor 16 for detecting the ambient temperature and humidity, a first temperature sensor 17 for detecting the actual water temperature in the water-side heat exchanger, a second temperature sensor 18 for detecting the temperature of the coil pipe of the air-side heat exchanger 15, and a pressure sensor 19 for detecting the pressure change of the fins.

[0044] Specifically, the position of the ambient temperature and humidity sensor 16 is not specifically limited in the present invention, and it is only used to collect the external ambient temperature and humidity where the air-side heat exchanger 15 is located, so as to obtain the ambient temperature Ta and the ambient humidity RH.

[0045] Specifically, the position of the first temperature sensor 17 is not specifically limited in the present invention, and it is only used to collect the water temperature after being heated at the user end under the action of the heat pump system, so as to obtain the actual water temperature Tr.

[0046] Specifically, the second temperature sensor 18 is provided on the coil pipe of the air-side heat exchanger 15 to obtain the coil pipe temperature Tp.

[0047] Specifically, the pressure sensor 19 is provided on the fins of the air-side heat exchanger 15 and is used to obtain the surface pressure P of the fins; specifically, the pressure sensor 19 can collect the maximum pressure P1 of the fins of the air-side heat exchanger 15 when the compressor 11 in the heat pump system starts and runs to the set highest frequency, the thick frost pressure threshold P2 detected when the heat pump system first starts the defrosting mode, the thin frost pressure threshold P3 detected when the heat pump system first starts the defrosting mode, and the pressure threshold P4 detected after defrosting is completed when the heat pump system first starts the defrosting mode.

[0048] Specifically, it further includes a controller, and the ambient temperature and humidity sensor 16, the pressure sensor 19, and the temperature sensors are electrically connected or communicatively connected to the controller.

[0049] Specifically, as shown in Table 1 below, the parameter meanings and symbols used in the present invention are as follows:

[0050]

[0051]

[0052] As Figure 2 shown, the controller of the present invention controls the defrosting function of the air-side heat exchanger 15 in the following manner:

[0053] Obtain the defrosting history of the heat pump system during the current heating startup, and determine whether the number of defrosts is greater than or equal to 1:

[0054] If the answer is no, obtain the ambient temperature Ta and the coil temperature Tp, and determine whether the ambient temperature Ta and the coil temperature Tp simultaneously meet the first defrost startup condition: If they are met, control the four-way valve to reverse for defrosting, collect the defrost time t, and collect the fin pressure P within a specific coil temperature range until the first defrost exit condition is met to exit defrosting, and obtain the thick frost pressure threshold P2 and the defrost completion pressure threshold P4 based on the average pressure;

[0055] If the answer is yes, obtain the ambient temperature Ta and the ambient humidity RH, and determine whether any one of the ambient temperature Ta and the ambient humidity RH meets the non-first defrost startup condition: If it is met, obtain the fin pressure P. When the fin pressure P is greater than the thick frost pressure threshold P2, control the four-way valve to reverse for defrosting, collect the defrost time t, until the second defrost exit condition is met to exit defrosting.

[0056] Specifically, when implemented, the defrost startup conditions set by the ambient temperature Ta and the coil temperature Tp are as follows:

[0057] The first defrost startup condition is: 3°C < Ta < 10°C and Tp < -5°C;

[0058] The second defrost startup condition is: -3°C < Ta ≤ 3°C and Tp < -3°C;

[0059] The third defrost startup condition is: -10°C < Ta ≤ -3°C and Tp < -5°C;

[0060] The fourth defrost startup condition is: Ta ≤ -10°C and Tp < -12°C.

[0061] Specifically, when implemented, the thick frost pressure threshold P2 and the thin frost pressure threshold P3 based on the average pressure are obtained through the following methods:

[0062] If the first defrost startup condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -5°C ≤ TP < -3°C is stored as the thick frost pressure threshold P2, and the average value of the fin pressure P collected when -3°C ≤ Tp < 0°C is stored as the thin frost pressure threshold P3;

[0063] If the second defrost startup condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -3°C ≤ TP < 0°C is stored as the thick frost pressure threshold P2, and the average value of the fin pressure P collected when 0°C ≤ TP < 3°C is stored as the thin frost pressure threshold P3;

[0064] If the third defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -5°C ≤ TP < -3°C is stored as the thick frost pressure threshold P2, and the average value of the fin pressure P collected when -3°C ≤ Tp < 0°C is stored as the thin frost pressure threshold P3;

[0065] If the fourth defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -12°C ≤ TP < -10°C is stored as the thick frost pressure threshold P2, and the average value of the fin pressure P collected when -10°C ≤ TP < -8°C is stored as the thin frost pressure threshold P3.

[0066] In specific implementation, the first defrost exit condition is as follows: the defrost time t is greater than or equal to 6 min, or the coil temperature Tp ≥ 15°C. S30 obtains the ambient temperature Ta and the ambient humidity RH, and determines whether any one of the ambient temperature Ta and the ambient humidity RH satisfies the defrost start condition:

[0067] If it is satisfied, the fin pressure P is obtained, and it is determined whether the fin pressure P is greater than or equal to the thick frost pressure threshold P2:

[0068] If it is yes, the four-way valve is controlled to reverse for defrosting until the fin pressure P satisfies the second defrost exit condition and exits defrosting;

[0069] If it is no, the fin pressure P is continuously obtained;

[0070] If it is not satisfied, the ambient temperature Ta and the ambient humidity RH are continuously obtained.

[0071] In specific implementation, the defrost start condition set by the ambient temperature Ta and the ambient humidity RH is as follows:

[0072] The ambient temperature Ta ≤ 2°C, or the ambient humidity RH ≥ 70%.

[0073] In specific implementation, the second defrost exit condition is as follows: the defrost time t is greater than or equal to 6 min, or the fin pressure P is less than the defrost completion pressure threshold P4.

[0074] In order to more accurately control the heat pump system 10 to perform defrosting under thin frost conditions, further, when any one of the ambient temperature Ta and the ambient humidity RH satisfies the defrost start condition, it is determined whether the fin pressure P is greater than or equal to the thick frost pressure threshold P2:

[0075] If it is yes, the four-way valve is controlled to reverse for defrosting until the fin pressure P satisfies the defrost exit condition and exits defrosting;

[0076] If it is no, it is further determined whether the fin pressure P is greater than or equal to the thin frost pressure threshold P3:

[0077] If so, obtain the actual water temperature Tr and analyze the relationship between the actual water temperature Tr and the preset water temperature Tset:

[0078] When Tr ≤ Tset - 3°C, continuously monitor the fin pressure P;

[0079] When Tr ≥ Tset - 3°C, control the four-way valve to reverse defrost until the fin pressure P meets the defrost exit condition and exits defrost.

[0080] To avoid the problem that the defrost control does not match the actual working conditions due to sudden pressure changes and drastic pressure changes caused by the heat pump system being affected by the external environment, and to enable the defrost control to be adaptively adjusted according to the environment and working conditions, it also includes the update of the thick frost pressure threshold P2, the thin frost pressure threshold P3, and the defrost completion pressure threshold P4:

[0081] SA1 obtains the maximum fin pressure P1, calculates and obtains the thick frost pressure difference △P1 between the thick frost pressure threshold P2 and the maximum fin pressure P1, the thin frost pressure difference △P2 between the thin frost pressure threshold P3 and the maximum fin pressure P1, and the pressure difference △P3 between the defrost completion pressure threshold P4 and the maximum fin pressure P1;

[0082] SA2 obtains the fin pressure P and continuously calculates the pressure change rate △P of the fin within the set period M, and judges whether it exceeds the set pressure change threshold △P set :

[0083] If so, the average fin pressure P obtained in the corresponding set period M M replaces the maximum fin pressure P1 to obtain the corrected maximum fin pressure and calculates the corrected thick frost pressure threshold according to the corrected maximum fin pressure and △P1 Replace the thick frost pressure threshold P2 with the corrected thick frost pressure threshold ; and calculate the corrected thin frost pressure threshold according to the corrected maximum fin pressure and △P2 Replace the thin frost pressure threshold P3 with the corrected thin frost pressure threshold ; and calculate the corrected defrost completion pressure threshold according to the corrected maximum fin pressure and △P3 Replace the defrost completion pressure threshold P4 with the corrected defrost completion pressure threshold ;

[0084] Compared with the prior art, the heat pump system of the present invention realizes precise defrosting on demand by automatically learning the pressure characteristics after the first defrost and dynamically adjusting the trigger conditions in combination with the environmental temperature and humidity and user needs.

[0085] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that unless otherwise stated, "a plurality" means two or more; the terms "first", "second", "third", etc. are only used for distinction and not for describing a specific order or sequence, nor can they be understood as indicating or implying relative importance. The term "and / or" used herein means any or all possible combinations of one or more of the associated listed items. When the above description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of the present application, for those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0086] The above-described embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A heat pump system with defrost control, comprising a compressor, a four-way valve, a water-side heat exchanger, a throttling component and an air-side heat exchanger connected in sequence by a refrigerant circulation pipeline; a temperature and humidity sensor for obtaining the ambient temperature and humidity, and a first temperature sensor for obtaining the water temperature in the water-side heat exchanger; characterized in that, The air-side heat exchanger includes a coil, fins, a second temperature sensor disposed on the coil, a third temperature sensor and a pressure sensor disposed on the fins; it further includes a controller, the controller is electrically connected or communicatively connected to the temperature and humidity sensor, each temperature sensor and the pressure sensor, and the controller controls the defrosting of the air-side heat exchanger in the following manner: Obtain the defrosting history of the current heating startup of the heat pump system, and determine whether the number of defrosts is greater than or equal to 1: If the answer is no, obtain the ambient temperature Ta and the coil temperature Tp, and determine whether the ambient temperature Ta and the coil temperature Tp simultaneously satisfy the first defrost startup condition: If satisfied, control the four-way valve to reverse for defrosting, collect the fin pressure P within a specific coil temperature range during the defrosting time t until the first defrost exit condition is met to exit defrosting, and obtain the thick frost pressure threshold P2 and the defrost completion pressure threshold P4 based on the average pressure; If the answer is yes, obtain the ambient temperature Ta and the ambient humidity RH, and determine whether any one of the ambient temperature Ta and the ambient humidity RH satisfies the non-first defrost startup condition: If satisfied, obtain the fin pressure P, and when the fin pressure P is greater than the thick frost pressure threshold P2, control the four-way valve to reverse for defrosting, collect the defrosting time t until the second defrost exit condition is met to exit defrosting.

2. The heat pump system with air-side heat exchanger defrost control according to claim 1, wherein The first defrost startup conditions set by the ambient temperature Ta and the coil temperature Tp are as follows: The first defrost startup condition is: 3°C < Ta < 10°C and Tp < -5°C; The second defrost startup condition is: -3°C < Ta ≤ 3°C and Tp < -3°C; The third defrost startup condition is: -10°C < Ta ≤ -3°C and Tp < -5°C; The fourth defrost startup condition is: Ta ≤ -10°C and Tp < -12°C.

3. The heat pump system with air-side heat exchanger defrosting control according to claim 1, wherein The thick frost pressure threshold P2 based on the average pressure is obtained in the following manner: If the first defrost startup condition is triggered and the defrosting mode is entered, the average value of the fin pressure P collected when -5°C ≤ TP < -3°C is stored as the thick frost pressure threshold P2; If the second defrost startup condition is triggered and the defrosting mode is entered, the average value of the fin pressure P collected when -3°C ≤ TP < 0°C is stored as the thick frost pressure threshold P2; If the third defrost startup condition is triggered and the defrosting mode is entered, the average value of the fin pressure P collected when -5°C ≤ TP < -3°C is stored as the thick frost pressure threshold P2; If the fourth defrost startup condition is triggered and the defrosting mode is entered, the average value of the fin pressure P collected when -12°C ≤ TP < -10°C is stored as the thick frost pressure threshold P2.

4. The heat pump system with air-side heat exchanger defrost control according to claim 1, characterized in that, The non-first defrost startup condition set by any one of the ambient temperature Ta and the ambient humidity RH is as follows: Ta ≤ 2°C, or RH ≥ 70%.

5. The heat pump system with air-side heat exchanger defrost control according to claim 3, characterized in that, When the heat pump system enters the first defrost mode and collects the fin pressure P within a specific coil temperature range during the defrosting time t, it also includes obtaining the thin frost pressure threshold P3 based on the average pressure, and the thin frost pressure threshold P3 is obtained in the following manner: If the first defrost startup condition is triggered and the defrosting mode is entered, the average value of the fin pressure P collected when -3°C ≤ Tp < 0°C is stored as the thin frost pressure threshold P3; If the second defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when 0°C ≤ TP < 3°C is stored as the light frost pressure threshold P3; If the third defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -3°C ≤ Tp < 0°C is stored as the light frost pressure threshold P3; If the fourth defrost start condition is triggered and the defrost mode is entered, the average value of the fin pressure P collected when -10°C ≤ TP < -8°C is stored as the light frost pressure threshold P3.

6. The heat pump system with air-side heat exchanger defrosting control according to claim 5, characterized in that, It also includes that when any one of the ambient temperature Ta and the ambient humidity RH satisfies the defrost start condition and the fin pressure P is less than the heavy frost pressure threshold P2, further determine whether the fin pressure P is greater than or equal to the light frost pressure threshold P3: If it is yes, obtain the actual water temperature Tr and analyze the relationship between the actual water temperature Tr and the preset water temperature Tset: When the actual water temperature Tr is less than or equal to the difference between the preset water temperature Tset and the set water temperature hysteresis ΔTr, continuously monitor the fin pressure P; When the actual water temperature Tr is greater than the difference between the preset water temperature Tset and the set water temperature hysteresis ΔTr, control the four-way valve to reverse for defrosting until the second defrost exit condition is satisfied and the defrosting is exited.

7. The heat pump system with air-side heat exchanger defrost control according to claim 1, characterized in that: The first defrost exit condition is as follows: the defrost time t is greater than or equal to 6 min, or the coil temperature Tp ≥ 15°C.

8. The heat pump system with air-side heat exchanger defrost control according to claim 1, characterized in that: The second defrost exit condition is as follows: the defrost time t is greater than or equal to 6 min, or the fin pressure P is less than the defrost completion pressure threshold P4.

9. The heat pump system with air-side heat exchanger defrost control according to claim 5 or 6, characterized in that, It also includes the update of the heavy frost pressure threshold P2, the light frost pressure threshold P3, and the defrost completion pressure threshold P4: SA1 obtains the maximum fin pressure P1, calculates and obtains the heavy frost pressure difference ΔP1 between the heavy frost pressure threshold P2 and the maximum fin pressure P1, the light frost pressure difference ΔP2 between the light frost pressure threshold P3 and the maximum fin pressure P1, and the pressure difference ΔP3 between the defrost completion pressure threshold P4 and the maximum fin pressure P1; SA2 obtains the fin pressure P and continuously calculates the pressure change rate △P of the fin within the set period M, and determines whether it exceeds the set pressure change threshold △P set : If it is yes, the average fin pressure P obtained in the corresponding set period M M will replace the maximum fin pressure P1 to obtain the corrected maximum fin pressure and calculate the corrected thick frost pressure threshold based on the corrected maximum fin pressure and △P1 Replace the thick frost pressure threshold with the corrected thick frost pressure threshold P2; and calculate the corrected light frost pressure threshold based on the corrected maximum fin pressure and △P2 Replace the light frost pressure threshold with the corrected light frost pressure threshold P3; and calculate the corrected defrost completion pressure threshold based on the corrected maximum fin pressure and △P3 Replace the defrost completion pressure threshold with the corrected defrost completion pressure threshold P4.

10. The heat pump system with air-side heat exchanger defrosting control according to claim 9, characterized in that: The set water temperature hysteresis ΔTr is set to 3°C.

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