Air conditioner, condensing unit and defrosting method thereof

Abstract

The present application relates to an air conditioner, a condensing unit, and a defrosting method thereof. The condensing unit includes a first heat exchanger located in a closed space and connected in series to a circulation pipeline. The defrosting method includes: starting a cooling mode; if the first heat exchanger satisfies a first preset condition, controlling entry into a defrosting mode; in the defrosting mode, if a second preset condition is satisfied, obtaining a ratio of the current air volume to the initial air volume for starting the cooling mode; if a preset threshold is reached, directly controlling exit from the defrosting mode to enter the next cooling mode and defrosting mode cycle; otherwise, correcting at least one of the first preset condition and the second preset condition before entering the next cooling mode and defrosting mode switching cycle. The air conditioner, the condensing unit, and the defrosting method thereof can adaptively adjust themselves according to the defrosting situation to solve the problem of incomplete defrosting, have high control accuracy, and save energy.

Description

Technical Field

[0001] The present application relates to the technical field of air conditioning, and in particular to an air conditioner, a condensing unit and a defrosting method thereof. Background Art

[0002] Refrigeration applications generally operate at lower temperatures than normal air conditioning, requiring long periods of continuous operation. Frost formation has long been a challenge in this industry. Prior art methods typically determine the timing of defrosting by timing entry, exiting the defrost function, or reaching a certain temperature, which is a simple operation. However, if the defrost time is inaccurate, such as exiting the defrost function too early, defrosting may be incomplete, and even lead to increasing evaporator frosting after several cycles. Setting the defrost time too long wastes energy and can easily increase the ambient temperature of the cold storage, affecting the preservation of food inside. Summary of the Invention

[0003] The purpose of the present application is to provide an air conditioner, a condensing unit and a defrosting method thereof, which can adaptively adjust according to the defrosting situation to solve the problem of incomplete defrosting, have high control accuracy and save energy.

[0004] To this end, in a first aspect, an embodiment of the present application provides a defrosting method for a condensing unit, the condensing unit including a first heat exchanger located in a closed space and connected in series to a circulation pipeline, the defrosting method comprising:

[0005] Starting the cooling mode, if the first heat exchanger meets the first preset condition, controlling the system to enter the defrost mode;

[0006] In the defrost mode, if the second preset condition is met, the ratio of the current air volume at this time to the initial air volume for starting the refrigeration mode is obtained. If the preset threshold is reached, the defrost mode is directly controlled to exit to enter the next refrigeration mode and defrost mode cycle. Otherwise, at least one of the first preset condition and the second preset condition is corrected before entering the next refrigeration mode and defrost mode conversion cycle.

[0007] In a possible implementation, the first preset condition includes a first entry condition, a second entry condition, a third entry condition, and a fourth entry condition. In the refrigeration mode, if any entry condition is met, the control enters the defrost mode according to the entry condition.

[0008] The second preset condition includes a first exit condition, a second exit condition and a third exit condition. In the defrost mode, when any exit condition is met and the ratio of the current air volume to the initial air volume does not reach the preset threshold, at least one entry condition is corrected, or at least one exit condition is corrected.

[0009] In a possible implementation, the first heat exchanger has an initial set air volume Fh in the cooling mode, the initial cooling attenuation ratio of the first heat exchanger is set to A, and the initial cooling capacity Z1 and initial air volume F1 in the frost-free state when the cooling mode is started are obtained.

[0010] The first entry condition includes: during the operation of the cooling mode, detecting the current cooling capacity Z and the current air volume F of the first heat exchanger; if F < Fh, the detection time is greater than the first time length, and Z < Z1 * A is satisfied within the second time length, the unit is first controlled to enter forced cooling, and after the third preset condition is met, the unit is controlled to enter the defrost mode and the cooling time t is recorded, wherein the first time length is greater than the second time length;

[0011] The second entry condition includes: if F<0.5*F1, control enters defrost mode, wherein Fh>0.5*F1;

[0012] The third entry condition includes: if Z<0.5*Z1 is satisfied within the second time period, the control enters the defrost mode;

[0013] The fourth entry condition includes: if the storage temperature does not decrease within the second time period, the control enters the defrost mode.

[0014] In a possible implementation, the condensing unit includes a storage temperature sensing package and a defrost temperature sensing package. The defrost temperature sensing package is used to detect the defrost temperature T1, and the storage temperature sensing package is used to detect the storage temperature T2 of the enclosed space, set the initial frost exit temperature Tt and set the initial storage temperature Ts.

[0015] The first exit condition includes: if T1 ≥ Tt;

[0016] The second exit condition includes: if T1 ≥ 2°C, and T2 ≥ Ts + 3°C;

[0017] The third exit condition includes: if T1 is less than 2°C, and T2 is greater than or equal to Ts+5°C.

[0018] In a possible implementation, the third preset condition includes: T2 = Ts-3° C., or running for 5 minutes.

[0019] In a possible implementation, in the defrost mode, when the first heat exchanger satisfies the first exit condition or the second exit condition, the defrost mode is controlled to be exited, and before executing the cooling mode of the next cycle, the current air volume F at the time of exit is compared with the initial air volume F1. If the preset threshold value F / F1 is between 0.95 and 1, no correction is performed and the cooling mode of the next cycle is directly entered;

[0020] If the preset threshold value F / F1 is less than 0.95, and when entering the defrost mode with the first entry condition in the cycle, if F / F1 = 0.8-0.95, the initial refrigeration attenuation ratio A is increased by 5% as the new initial refrigeration attenuation ratio for the next cycle, and the set air volume Fh is multiplied by 1.05 as the new set air volume for the next cycle; if F / F1 is less than 0.8, the initial refrigeration attenuation ratio A is increased by 10% as the new initial refrigeration attenuation ratio for the next cycle, and the set air volume Fh is multiplied by 1.1 as the new set air volume; and when the refrigeration operation is t / 2 or Z is less than Z1*A during the process of exiting the defrost mode, the defrost mode of the cycle is re-entered;

[0021] If the preset threshold F / F1 is less than 0.95, and when the defrost mode is entered under one of the second entry condition, the third entry condition, and the fourth entry condition in the cycle, the initialization frost exit temperature Tt is increased by 1° C. as the new initialization frost exit temperature.

[0022] In one possible implementation, in the defrost mode, when the first heat exchanger meets the third exit condition, the defrost mode is controlled to exit, and before executing the refrigeration mode of the next cycle, if the defrost mode is entered with the first entry condition in the cycle, the initial refrigeration attenuation ratio A is increased by 10% and used as the new initial refrigeration attenuation ratio for the next cycle; if the defrost mode is entered with one of the second entry condition, the third entry condition and the fourth entry condition in the cycle, the initial frost exit temperature Tt is increased by 2°C as the new initial frost exit temperature, and the defrost mode in the cycle is re-entered after continuing to run for 10 minutes.

[0023] In a possible implementation, the defrost method further includes: if no correction is performed in three consecutive cycles of switching between the refrigeration mode and the defrost mode, reducing the initial refrigeration attenuation ratio A by 5% and setting it as a new initial refrigeration attenuation ratio for the next cycle;

[0024] If the defrost exit condition is the second exit condition in three consecutive cycles of switching between the refrigeration mode and the defrost mode, the initialization frost exit temperature Tt is reduced by 1°C as the new initialization frost exit temperature, and in the three consecutive cycles of subsequent operation, the preset threshold F / F1 is between 0.95-1, otherwise the initialization frost exit temperature Tt is reset to the previous temperature.

[0025] In a possible implementation, the first duration is 5 minutes, and the second duration is 3 minutes.

[0026] In a second aspect, an embodiment of the present application further provides a condensing unit, the condensing unit comprising a first heat exchanger located in a closed space and connected in series to a circulation pipeline, wherein when a cooling mode is started, if the first heat exchanger satisfies a first preset condition, the unit is controlled to enter a defrost mode;

[0027] When in the defrost mode, if the second preset condition is met, the ratio of the current air volume at this time to the initial air volume for starting the refrigeration mode is obtained. If the preset threshold is reached, the defrost mode is directly controlled to exit to enter the next refrigeration mode and defrost mode cycle. Otherwise, at least one of the first preset condition and the second preset condition is corrected before entering the next refrigeration mode and defrost mode conversion cycle.

[0028] In a second aspect, an embodiment of the present application further provides an air conditioner, comprising a condensing unit as described above.

[0029] According to the air conditioner, condensing unit, and defrost method provided by the embodiment of the present application, it is possible to automatically determine whether the conditions for the unit to enter and exit defrost are appropriate during the switching cycle between the refrigeration mode and the defrost mode through pre-set entry and exit conditions, thereby automatically achieving the switching between the refrigeration mode and the defrost mode. Moreover, during the cycle, based on the actual change in air volume, a step is added to determine whether to revise the first preset condition and the second preset condition each time the defrost mode is exited, so as to reasonably judge the defrost entry and exit conditions and adjust them to appropriate values. This avoids the situation where the defrost mode remains in the defrost mode after complete defrosting, causing the storage temperature to rise, thereby affecting the freshness of the items in the storage. It can also avoid the problem of increasingly serious evaporator frosting after multiple cycles due to incomplete defrosting, resulting in high control accuracy and energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without inventive work. In addition, in the drawings, the same reference numerals are used for the same components, and the drawings are not drawn according to the actual scale.

[0031] Figure 1 A simple structural diagram of a condensing unit provided in an embodiment of the present application is shown;

[0032] Figure 2 A flow chart of a defrosting method provided in an embodiment of the present application is shown;

[0033] Figure 3A flow chart showing the transition from a refrigeration mode to a defrost mode in a defrost method provided in an embodiment of the present application is shown;

[0034] Figure 4 A flowchart showing exiting a defrost mode in a defrost method provided in an embodiment of the present application is shown;

[0035] Figure 5 A flow chart showing a correction process in a defrosting method provided in an embodiment of the present application is shown.

[0036] Reference numerals:

[0037] 100-condensing unit; 1-first heat exchanger; 2-second heat exchanger; 3-compressor; 4-circulation pipeline; 5-anemometer; 6-temperature sensor; 7-humidity sensor; 200-enclosed space. DETAILED DESCRIPTION

[0038] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0039] Figure 1 A simple structural diagram of a condensing unit provided in an embodiment of the present application is shown.

[0040] See also Figure 1 , an embodiment of the present application provides a condensing unit for an air conditioner, which is a split-type air conditioner, including an indoor unit and an outdoor unit, and can be used in a closed space 200 such as indoors, which will not be described in detail here. The indoor unit of the air conditioner is provided with a first heat exchanger 1, and the outdoor unit of the air conditioner is provided with a second heat exchanger 2 and a compressor 3, which are connected in series through a circulation pipeline 4 to form a closed loop of the compressor 3, the first heat exchanger 1 and the second heat exchanger 2. In the condensing unit 100, the compressor 3 is used to discharge high-temperature and high-pressure refrigerant and to recover the refrigerant returned by the circulation. The first heat exchanger 1 and the second heat exchanger 2 are used as an evaporator and a condenser according to the change of the circulation direction, which will not be specifically limited here.

[0041] It is understood that the condensing unit 100 further includes an anemometer 5, a velocity sensor, a temperature sensor 6, a humidity sensor 7, a storage temperature sensor, and a defrost temperature sensor, etc., located at the inlet and outlet of the first heat exchanger 1, on the periphery, or near the connected circulation pipeline 4. These sensors are used to detect the inlet and outlet air volume, inlet and outlet dry-bulb temperature, relative humidity, and air volume of the first heat exchanger 1 in real time, thereby calculating the current air volume F and the current operating cooling capacity of the first heat exchanger 1 as the air volume and cooling capacity under this operating condition. The specific calculation steps and methods are not described in detail here.

[0042] It should be emphasized that the air conditioner equipped with the condensing unit 100 described above can be used in common applications such as homes and shopping malls, as well as in enclosed spaces 200 such as cold storage where items need to be kept fresh, without any specific limitation. The following describes the condensing unit 100 and its defrosting method in the embodiments of the present application in detail, assuming that the unit is used in a cold storage environment for long periods of time.

[0043] See also Figure 2 The condensing unit 100 operates in at least a cooling mode and a defrost mode. When the cooling mode is initially activated, the first heat exchanger 1 has an initial air volume F1 and an initial cooling capacity Z1, both of which meet the no-frost standard. When the cooling mode is activated, if the first heat exchanger 1 satisfies a first preset condition, control is initiated into the defrost mode. While in the defrost mode, if a second preset condition is satisfied, the ratio of the current air volume F to the initial air volume F1 for activating the cooling mode is obtained. If this ratio reaches a preset threshold, control is directly initiated into the defrost mode to enter the next cooling mode and defrost mode cycle. Otherwise, at least one of the first and second preset conditions is modified before entering the next cooling mode and defrost mode cycle. According to the pre-set conditions, the automatic switching between the refrigeration mode and the defrost mode is realized to ensure that the defrost can be complete. In the process of switching cycles, the actual change of the air volume is used to add a step of whether to correct the first preset condition and the second preset condition during each exit of the defrost mode, so as to make a reasonable judgment on the defrost entry and exit conditions and adjust them to appropriate values ​​to solve the problem of incomplete defrost. The control accuracy is high, energy consumption is saved, and the warehouse temperature is avoided from rising due to the defrost mode after complete defrost, which affects the freshness of the items in the warehouse. It can also avoid the problem of increasingly serious frosting of the evaporator after multiple cycles due to incomplete defrost.

[0044] It is understandable that the condensing unit 100 also includes a storage temperature sensing package and a defrost temperature sensing package. The defrost temperature sensing package is used to detect the defrost temperature T1, and the storage temperature sensing package is used to detect the storage temperature T2 of the enclosed space 200, set the initial frost exit temperature Tt and set the initial storage temperature Ts.

[0045] When the condensing unit 100 leaves the factory, the first heat exchanger 1 has an initially set air volume Fh and a set initial cooling attenuation ratio A. Taking the initial operation of the condensing unit 100 as an example, when the cooling mode is started, the initial cooling capacity Z1, initial air volume F1, initial frost exit temperature Tt, and initial storage temperature Ts in the frost-free state at startup are obtained. As described above for the condensing unit 100, the cooling capacity and air volume can be detected and calculated based on the corresponding configured structures, and are not further described here.

[0046] An embodiment of the present application provides an air conditioner, which includes the condensing unit 100 described above, which will not be described in detail here.

[0047] Based on the condensing unit 100 described above, see Figures 2 to 5 The embodiment of the present application further provides a defrosting method for a condensing unit 100, comprising the following steps:

[0048] S101, start the cooling mode, if the first heat exchanger 1 meets the first preset condition, then control to enter the defrost mode.

[0049] See also Figure 3 , the first preset condition may include a first entry condition, a second entry condition, a third entry condition and a fourth entry condition. When the refrigeration mode is running, if any entry condition is met, the control enters the defrost mode with the entry condition. That is, during the operation of the refrigeration mode, when it is detected that any entry condition is met, the control enters the defrost mode with the entry condition. Optionally, the first preset condition may also be one or more of the above-mentioned entry conditions, or may also include a fifth entry condition, a sixth entry condition, etc. The entry conditions can be divided into different forms according to different specific needs, and no specific limitation is made here. In the embodiment of the present application, based on the consideration of being able to automatically adjust the defrost parameters more accurately under different working conditions, the above four different entry conditions are set as defrost entry conditions.

[0050] Among them, the first entry condition includes: during the operation of the cooling mode, detecting the current cooling capacity Z and the current air volume F of the first heat exchanger 1, if F<Fh, the detection time is greater than the first time length, and Z<Z1*A is satisfied within the second time length, the unit is first put into forced cooling, and after the third preset condition is met, the unit is controlled to enter the defrost mode and the cooling time t is recorded.

[0051] Optionally, the first duration is greater than the second duration, the first duration is 5 minutes, and the second duration is 3 minutes.

[0052] Optionally, the third preset condition includes: the warehouse temperature detected by the warehouse temperature sensing package T2 = Ts-3°C, or running for 5 minutes.

[0053] The second entry condition includes: if F<0.5*F1, the control enters the defrost mode, wherein Fh>0.5*F1. That is, when the detected current air volume F is less than 50% of the initial air volume F1, the control enters the defrost mode.

[0054] The third entry condition includes: if Z<0.5*Z1 is satisfied within the second time period, the control enters the defrost mode, that is, the defrost mode is entered when the refrigeration decay ratio decreases by 50%.

[0055] The fourth entry condition includes: if the storage temperature does not drop within the second time period, the control enters the defrost mode. It can be understood that the so-called storage temperature does not drop can be understood as that the storage temperature T2 is always maintained at or above Ts+3°C within the second time period.

[0056] S102. In the defrost mode, if the second preset condition is met, obtain the ratio of the current air volume F at this time to the initial air volume F1 for starting the refrigeration mode. If the preset threshold is reached, directly control the exit from the defrost mode to enter the next refrigeration mode and defrost mode cycle. Otherwise, correct at least one of the first preset condition and the second preset condition before entering the next refrigeration mode and defrost mode conversion cycle.

[0057] See also Figure 4 The second preset condition includes the first exit condition, the second exit condition and the third exit condition. In the defrost mode, when any exit condition is met and the ratio of the current air volume F to the initial air volume F1 does not reach the preset threshold, at least one entry condition is corrected, or at least one exit condition is corrected.

[0058] Among them, the first exit condition includes: if T1≥Tt; the second exit condition includes: if T1≥2℃, and T2≥Ts+3℃; the third exit condition includes: if T1<2℃, and T2≥Ts+5℃.

[0059] The defrosting method described in the above steps can automatically determine whether the conditions for the unit to enter and exit defrost are appropriate during the switching cycle between refrigeration mode and defrost mode, based on pre-set entry and exit conditions, thereby automatically switching between refrigeration mode and defrost mode. Furthermore, during the cycle, based on the actual change in air volume, a step is added to determine whether to revise the first and second preset conditions each time the defrost mode is exited, so as to rationally determine and adjust the defrost entry and exit conditions to appropriate values, thereby resolving the problem of incomplete defrosting. This method has high control accuracy, saves energy, avoids the situation where the unit remains in defrost mode after complete defrosting, causing the storage temperature to rise and affecting the freshness of the items in the storage, and avoids the problem of increasingly severe evaporator frosting after multiple cycles due to incomplete defrosting.

[0060] In an alternative embodiment, see Figure 4 In defrost mode, if the first heat exchanger 1 meets the first exit condition or the second exit condition, the defrost mode is exited. Before executing the cooling mode of the next cycle, the current air volume F at the time of exit is compared with the initial air volume F1. If the preset threshold F / F1 is between 0.95 and 1, no correction is made and the cooling mode of the next cycle is directly entered. If the preset threshold F / F1 is less than 0.95, and the defrost mode is entered with the first entry condition in this cycle, if F / F1 = 0.8-0.95, the initial cooling decay ratio A is increased by 5% to set the new initial cooling decay ratio A for the next cycle, and the set air volume Fh is multiplied by 1.05 to set the new set air volume for the next cycle. If F / F1 is less than 0.8, the initial cooling decay ratio A is increased by 10% to set the new initial cooling decay ratio A for the next cycle, and the set air volume Fh is multiplied by 1.1 to set the new set air volume. If the cooling operation time t / 2 or Z < Z1*A during the process of exiting the defrost mode is reached, the defrost mode of the cycle is re-entered. If the preset threshold F / F1 is less than 0.95, and the defrost mode is entered under one of the second entry condition, the third entry condition, and the fourth entry condition in the cycle, the initialization frost exit temperature Tt is increased by 1° C. as the new initialization frost exit temperature.

[0061] In the defrost mode, when the first heat exchanger 1 meets the third exit condition, the control exits the defrost mode, and before executing the refrigeration mode of the next cycle, if the defrost mode is entered with the first entry condition in the cycle, the initial refrigeration attenuation ratio A is increased by 10% and used as the new initial refrigeration attenuation ratio A for the next cycle; if the defrost mode is entered with one of the second entry condition, the third entry condition and the fourth entry condition in the cycle, the initial frost exit temperature Tt is increased by 2°C as the new initial frost exit temperature, and the defrost mode in the cycle is re-entered after continuing to run for 10 minutes.

[0062] It's important to note that during a transition between cooling and defrosting modes, if any of the defrost exit conditions are met and defrosting is exited, there will be an exit process, meaning that cooling is performed during this process but it does not mark the beginning of the next cooling mode. This process automatically adjusts the relevant parameters for the next cycle, either by correcting them or not, based on factors such as air volume and cooling attenuation ratio. This ensures complete defrosting when the new entry and exit conditions are met in the next cycle, with high control accuracy and energy avoidance.

[0063] In an optional embodiment, the defrost method further includes: if no parameter correction is performed during three consecutive cycles of switching between cooling mode and defrost mode, reducing the initial refrigeration decay ratio A by 5% and setting it as the new initial refrigeration decay ratio A for the next cycle. If the defrost exit condition during three consecutive cycles of switching between cooling mode and defrost mode is the second exit condition, reducing the initial frost exit temperature Tt by 1°C and setting it as the new initial frost exit temperature; otherwise, the temperature remains unchanged. If, during three subsequent consecutive cycles, the preset threshold F / F1 is between 0.95 and 1 at the end of defrost, the adjustment is terminated and the next cycle is entered; otherwise, the initial frost exit temperature Tt is reset to the previous temperature to enable the unit to adjust the refrigeration decay ratio.

[0064] It should be emphasized that the above-mentioned defrosting method can be applied to split-type air conditioners with refrigeration requirements, and can also be applied to other condensing units with refrigeration requirements, and is not specifically limited here.

[0065] It should be noted that references in this specification to "one embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes that particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not.

[0066] It should be readily understood that “on,” “above,” and “over” in this disclosure should be interpreted in the broadest manner, such that “on” means not only “directly on something,” but also includes “on something” with intervening features or layers therebetween, and “above” or “over” includes not only the meaning of “above” or “over,” but also includes “above” or “over” with no intervening features or layers therebetween (i.e., directly on something).

[0067] Additionally, spatially relative terms, such as "below," "beneath," "beneath," "above," and the like, may be used herein for ease of description to describe the relationship of one element or feature to other elements or features as depicted in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A defrosting method for a condensing unit, characterized in that: The condensing unit includes a first heat exchanger located in a closed space and connected in series to a circulation pipeline. The defrosting method includes: Starting the cooling mode, if the first heat exchanger meets the first preset condition, controlling the system to enter the defrost mode; In the defrost mode, if a second preset condition is met, a ratio of the current air volume at that time to the initial air volume for starting the cooling mode is obtained; if a preset threshold is reached, the defrost mode is directly controlled to exit and enter the next cooling mode and defrost mode cycle; otherwise, at least one of the first preset condition and the second preset condition is corrected before entering the next cooling mode and defrost mode switching cycle; The first preset condition includes a first entry condition, a second entry condition, a third entry condition, and a fourth entry condition. In the refrigeration mode, if any entry condition is met, the control enters the defrost mode according to the entry condition; The second preset condition includes a first exit condition, a second exit condition, and a third exit condition. In the defrost mode, when any exit condition is met and the ratio of the current air volume to the initial air volume does not reach a preset threshold, at least one entry condition is modified, or at least one exit condition is modified; The first heat exchanger has an initial set air volume Fh in the cooling mode, the initial cooling attenuation ratio of the first heat exchanger is set to A, and the initial cooling capacity Z1 and initial air volume F1 in the frost-free state when the cooling mode is started are obtained. The first entry condition includes: during the operation of the cooling mode, detecting the current cooling capacity Z and the current air volume F of the first heat exchanger; if F < Fh, the detection time is greater than the first time length, and Z < Z1 * A is satisfied within the second time length, the unit is first controlled to enter forced cooling, and after the third preset condition is met, the unit is controlled to enter the defrost mode and the cooling time t is recorded, wherein the first time length is greater than the second time length; The second entry condition includes: if F<0.5*F1, control enters defrost mode, wherein Fh>0.5*F1; The third entry condition includes: if Z<0.5*Z1 is satisfied within the second time period, the control enters the defrost mode; The fourth entry condition includes: if the storage temperature does not drop within the second time period, then the control enters the defrost mode; The condensing unit includes a storage temperature sensing package and a defrosting temperature sensing package. The defrosting temperature sensing package is used to detect the defrosting temperature T1, and the storage temperature sensing package is used to detect the storage temperature T2 of the closed space, set the initial frost exit temperature Tt and set the initial storage temperature Ts. The first exit condition includes: if T1 ≥ Tt; The second exit condition includes: if T1 ≥ 2°C, and T2 ≥ Ts + 3°C; The third exit condition includes: if T1 < 2°C, and T2 ≥ Ts + 5°C; In the defrost mode, when the first heat exchanger meets the first exit condition or the second exit condition, the defrost mode is exited, and before the next cycle of cooling mode is executed, the current air volume F at the time of exit is compared with the initial air volume F1. If the preset threshold value F / F1 is between 0.95 and 1, no correction is performed and the cooling mode of the next cycle is directly entered; If the preset threshold value F / F1 is less than 0.95, and when entering the defrost mode with the first entry condition in the cycle, if F / F1 = 0.8-0.95, the initial refrigeration attenuation ratio A is increased by 5% as the new initial refrigeration attenuation ratio for the next cycle, and the set air volume Fh is multiplied by 1.05 as the new set air volume for the next cycle; if F / F1 is less than 0.8, the initial refrigeration attenuation ratio A is increased by 10% as the new initial refrigeration attenuation ratio for the next cycle, and the set air volume Fh is multiplied by 1.1 as the new set air volume; and when the refrigeration operation is t / 2 or Z is less than Z1*A during the process of exiting the defrost mode, the defrost mode of the cycle is re-entered; If the preset threshold F / F1 is less than 0.95, and when the defrost mode is entered under one of the second entry condition, the third entry condition, and the fourth entry condition in the cycle, the initialization frost exit temperature Tt is increased by 1° C. as the new initialization frost exit temperature.

2. The defrosting method according to claim 1, characterized in that: The third preset condition includes: T2=Ts-3°C, or running for 5 minutes.

3. The defrosting method according to claim 1, characterized in that: In the defrost mode, when the first heat exchanger meets the third exit condition, the defrost mode is controlled to exit, and before executing the refrigeration mode of the next cycle, if the defrost mode is entered with the first entry condition in the cycle, the initial refrigeration attenuation ratio A is increased by 10% and used as the new initial refrigeration attenuation ratio for the next cycle; if the defrost mode is entered with one of the second entry condition, the third entry condition and the fourth entry condition in the cycle, the initial frost exit temperature Tt is increased by 2°C as the new initial frost exit temperature, and the defrost mode in the cycle is re-entered after continuing to run for 10 minutes.

4. The defrosting method according to claim 1, characterized in that: The defrosting method further includes: if no correction is performed in three consecutive cycles of switching between the refrigeration mode and the defrost mode, reducing the initial refrigeration attenuation ratio A by 5% and using it as a new initial refrigeration attenuation ratio for the next cycle; If the defrost exit condition is the second exit condition in three consecutive cycles of switching between the refrigeration mode and the defrost mode, the initialization frost exit temperature Tt is reduced by 1°C as the new initialization frost exit temperature, and in the three consecutive cycles of subsequent operation, the preset threshold F / F1 is between 0.95-1, otherwise the initialization frost exit temperature Tt is reset to the previous temperature.

5. The defrosting method according to claim 1, characterized in that: The first duration is 5 minutes, and the second duration is 3 minutes.

6. A condensing unit, characterized in that: The condensing unit is used to implement the defrosting method according to any one of claims 1 to 5, the condensing unit comprising a first heat exchanger located in a closed space and connected in series to a circulation pipeline, and when a cooling mode is started, if the first heat exchanger meets a first preset condition, the condensing unit is controlled to enter a defrosting mode; When in the defrost mode, if the second preset condition is met, the ratio of the current air volume at this time to the initial air volume for starting the refrigeration mode is obtained. If the preset threshold is reached, the defrost mode is directly controlled to exit to enter the next refrigeration mode and defrost mode cycle. Otherwise, at least one of the first preset condition and the second preset condition is corrected before entering the next refrigeration mode and defrost mode conversion cycle.

7. An air conditioner, characterized in that: Comprising the condensing unit as claimed in claim 6.

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