Defrosting control method and air conditioning unit

Abstract

The present invention discloses a defrosting control method and an air conditioning unit. The defrosting control method comprises: during the operation of the air conditioning unit, detecting the working parameters of a heat exchanger that is prone to frost, calculating the heat exchange efficiency of the heat exchanger that is prone to frost as the working heat exchange efficiency N; judging whether #imgabs0#; if so, when the air inlet temperature of the heat exchanger that is prone to frost is #imgabs1#, the air conditioning unit enters the defrosting operation, and when #imgabs2#, adjusting the main throttle valve opening of the air conditioning unit; wherein N1 is the initial heat exchange efficiency of the heat exchanger that is prone to frost. The present invention detects the working parameters of the heat exchanger that is prone to frost and calculates the heat exchange efficiency, and analyzes the frosting condition of the unit in combination with the air inlet temperature and heat exchange efficiency of the heat exchanger that is prone to frost, thereby reducing the misjudgment of defrosting and effectively improving the accuracy of defrosting.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning units, and in particular to a defrosting control method and an air conditioning unit. Background Art

[0002] Air-conditioning units are widely used in different fields. Air-conditioning units realize heat exchange through evaporator and condenser. When the surface temperature of the evaporator is lower than the dew point temperature, water vapor in the air will condense on its surface and gradually form frost. The accumulation of frost will greatly increase the thermal resistance, resulting in a sharp drop in heat exchange efficiency, thereby affecting the cooling or heating effect of the air conditioner.

[0003] Take the cold storage refrigeration unit as an example. During the operation of the refrigeration unit, the evaporator supplies cold air to the room to maintain a low temperature environment to ensure the quality and safety of the goods. However, under long-term low temperature and high humidity operating conditions, frost is very easy to form on the surface of the evaporator. The formation of frost will significantly increase the thermal resistance of the evaporator surface, resulting in a decrease in heat exchange efficiency, and may also hinder air circulation. The air supply and return air volumes will be weakened, affecting the temperature uniformity in the warehouse, and even causing the unit's operating load to increase and energy consumption to increase, ultimately affecting the refrigeration effect and the unit's operating stability.

[0004] At present, the defrosting strategy combining timed defrosting and coil temperature control is generally adopted in cold storage refrigeration units. The basic principle of this method is to preset a fixed defrosting cycle (such as every few hours or according to the accumulated running time) and defrosting duration. When the set conditions are met, the unit enters the defrosting operation, and the frost is melted by heating the coil or introducing an external heat source (such as hot air bypass). After the defrosting is completed, the defrosting is judged to be completed based on the coil temperature returning to a certain set value, and the refrigeration mode is restored.

[0005] Existing defrosting methods have obvious limitations: 1. The frequency of use, type of items, external environment and other factors of different cold storages vary greatly, resulting in different frosting speeds. Fixed-cycle defrosting may start too early when there is less frost, wasting energy; or fail to defrost in time when the frost is severe, affecting the refrigeration effect; 2. Relying solely on coil temperature as the only criterion for defrosting exit may lead to inaccurate judgment due to factors such as the location and accuracy of the temperature sensor; for example, when the local temperature of the coil is too high and the whole is still not completely defrosted, the system may mistakenly judge that defrosting is complete, thereby resuming refrigeration, resulting in incomplete defrosting.

[0006] Therefore, how to design a defrost control method and air-conditioning unit to achieve precise defrosting is a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0007] In order to solve the defect of low control accuracy of existing air-conditioning units, the present invention proposes a defrost control method and an air-conditioning unit, which detects the working parameters of the heat exchanger prone to frost and calculates the heat exchange efficiency, analyzes the frosting situation of the unit in combination with conditions such as the inlet air temperature and heat exchange efficiency of the heat exchanger prone to frost, reduces defrosting misjudgment, and effectively improves defrosting accuracy.

[0008] The technical solution adopted by the present invention is to design a defrosting control method, comprising:

[0009] During the operation of the air conditioning unit, the working parameters of the heat exchanger prone to frost are detected, and the heat exchange efficiency of the heat exchanger prone to frost is calculated as the working heat exchange efficiency N;

[0010] Determine whether ;

[0011] If so, then the inlet air temperature of the frosting-prone heat exchanger When the air conditioner is turned on, it will enter the defrosting mode;

[0012] Wherein, N1 is the initial heat transfer efficiency of the frosting-prone heat exchanger.

[0013] Furthermore, the defrost control method further includes:

[0014] determination Afterwards, in When the main throttle valve opening of the air-conditioning unit is adjusted, the working heat exchange efficiency N of the frosting-prone heat exchanger is improved.

[0015] Further, adjusting the main throttle valve opening of the air conditioning unit includes:

[0016] Calculate the change , k is the set opening;

[0017] According to the change The opening of the main throttle valve is reduced.

[0018] Furthermore, the defrost control method further includes:

[0019] After the air conditioner enters defrosting operation, the fan of the frosting-prone heat exchanger is turned on, and the air conditioner switches the refrigerant flow direction;

[0020] Determine whether the inlet and outlet temperature difference of the heat exchanger is prone to frost ;

[0021] If yes, the air conditioning unit exits defrosting operation.

[0022] Furthermore, the defrost control method further includes:

[0023] Determine whether the inlet and outlet temperature difference of the heat exchanger is prone to frost ;

[0024] If not, then detect the working parameters of the heat exchanger that is prone to frost, calculate the heat exchange efficiency of the heat exchanger that is prone to frost as the defrosting heat exchange efficiency N2, and The air conditioner unit exits defrosting operation.

[0025] Furthermore, when the air conditioning unit starts to work and runs for a first set time, the working parameters of the heat exchanger prone to frost are detected, and the heat exchange efficiency of the heat exchanger prone to frost is calculated as the initial heat exchange efficiency N1.

[0026] Furthermore, when the air conditioning unit starts to work and runs for a second set time, the working parameters of the frosting-prone heat exchanger are detected, and the heat exchange efficiency of the frosting-prone heat exchanger is calculated as the working heat exchange efficiency N; wherein the first set time < the second set time.

[0027] Furthermore, adjusting the main throttle valve opening of the air conditioning unit also includes:

[0028] After adjusting the main throttle valve each time, wait for the third set time, detect the working parameters of the frosting-prone heat exchanger, and calculate the heat exchange efficiency of the frosting-prone heat exchanger as the corrected heat exchange efficiency N3;

[0029] Determine whether ;

[0030] If yes, return to the step of adjusting the main throttle valve opening;

[0031] If not, the process returns to the step of detecting the working parameters of the heat exchanger prone to frost formation, and calculating the heat exchange efficiency of the heat exchanger prone to frost formation as the working heat exchange efficiency N.

[0032] Furthermore, the working parameters of the frosting-prone heat exchanger include the outlet air temperature t1, the inlet air temperature t2, and the tube temperature t3. The heat exchange efficiency of the frosting-prone heat exchanger is .

[0033] Furthermore, when the air-conditioning unit is in a heating state, the heat exchanger prone to frost is an outdoor heat exchanger; and / or when the air-conditioning unit is in a cooling state, the heat exchanger prone to frost is an indoor heat exchanger.

[0034] The present invention also proposes an air conditioning unit, comprising: a compressor, an outdoor heat exchanger, a main throttle valve and an indoor heat exchanger which are sequentially connected to form a refrigerant circulation loop, and a controller of the air conditioning unit executes the above-mentioned defrost control method.

[0035] In some embodiments, the air conditioning unit is a cold storage refrigeration unit.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. By detecting the working parameters of the heat exchanger prone to frost and calculating the heat exchange efficiency, the frosting condition of the unit is analyzed in combination with the inlet air temperature and heat exchange efficiency of the heat exchanger prone to frost, effectively improving the accuracy of the defrosting entry timing;

[0038] 2. Analyze the operating conditions of the air-conditioning unit by the attenuation of the heat exchange efficiency of the frosting-prone heat exchanger, and adjust the main throttle valve opening to improve the heat exchange efficiency, optimize the unit's energy efficiency, and prevent the compressor from inhaling liquid due to excessive refrigerant;

[0039] 3. After entering the defrost mode, the defrost condition of the unit is analyzed based on the inlet and outlet temperature difference and heat exchange efficiency of the frosting-prone heat exchanger, effectively improving the accuracy of the defrost exit timing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0041] Figure 1 is a connection diagram of the air conditioning unit of the present invention;

[0042] Figure 2 It is a schematic diagram of the refrigerant flow direction of the air-conditioning unit of the present invention in a cooling state;

[0043] Figure 3 It is a schematic diagram of the refrigerant flow direction of the air-conditioning unit of the present invention in the defrosting operation;

[0044] Figure 4 It is a schematic diagram of the defrosting process of the defrosting control method of the present invention;

[0045] Figure 5 It is a schematic diagram of the defrosting exit process of the defrosting control method of the present invention;

[0046] Figure 6 It is a complete flow chart of the defrosting control method of the present invention;

[0047] Description of the drawings: 1. Compressor; 2. Outdoor heat exchanger; 3. Indoor heat exchanger; 4. Main throttle valve; 5. Four-way valve; 6. Gas-liquid separator. DETAILED DESCRIPTION

[0048] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] like Figure 1As shown, the defrost control method proposed in the present invention is applicable to an air conditioning unit, which includes a compressor 1, an outdoor heat exchanger 2, a main throttle valve 4, and an indoor heat exchanger 3, which are sequentially connected to form a refrigerant circulation loop. Since the defrost control principles of the outdoor heat exchanger 2 and the indoor heat exchanger 3 are similar, the defrost control method can be used for defrosting the indoor heat exchanger 3 when the air conditioning unit is in a cooling state, and can also be used for defrosting the outdoor heat exchanger 2 when the air conditioning unit is in a heating state.

[0050] like Figure 2 , 3 As shown, if the air conditioning unit is in the cooling state, the heat exchanger that is prone to frost is the indoor heat exchanger 3. The refrigerant flow direction in the cooling state is shown in FIG. Figure 2 , the refrigerant flow direction during defrosting operation refers to Figure 3 By analogy, if the air-conditioning unit is in the heating state, the heat exchanger that is prone to frost is the outdoor heat exchanger 2. It should be understood that in actual application, the corresponding heat exchanger that is prone to frost can be selected according to different usage scenarios. For example, for an air-conditioning unit dedicated to refrigeration, its heat exchanger that is prone to frost can only be the indoor heat exchanger 3.

[0051] like Figure 4 As shown, specifically, the defrost control method includes:

[0052] During the operation of the air conditioning unit, the working parameters of the heat exchanger prone to frost are detected, and the heat exchange efficiency of the heat exchanger prone to frost is calculated as the working heat exchange efficiency N;

[0053] Determine whether ;

[0054] If yes, it means that the current heat exchange efficiency of the frosting-prone heat exchanger is significantly lower than the initial heat exchange efficiency, and there is a risk of frosting. When the frosting-prone heat exchanger is determined to be frosted, the air conditioning unit enters defrosting operation;

[0055] Wherein, N1 is the initial heat transfer efficiency of the frosting-prone heat exchanger.

[0056] Taking refrigeration as an example, the heat exchanger that is prone to frost is the indoor heat exchanger 3. Generally speaking, the main factor affecting the heat exchange efficiency is the degree of frost on the indoor heat exchanger 3. Therefore, the heat exchange efficiency when the last defrosting is completed can be used as the highest value of the heat exchange efficiency in this working cycle - the initial heat exchange efficiency N1, that is, each time the refrigeration is turned on, the heat exchange efficiency at this time will be calculated and it is considered that the heat exchange efficiency at this moment is the highest, which is used to guide the unit to enter and exit the next defrosting. In actual application, the heat exchange efficiency when the air-conditioning unit is turned on and enters the stable operation stage can be selected as the initial heat exchange efficiency N1, or the value of the initial heat exchange efficiency N1 can be designed according to specific needs. The present invention does not impose any special restrictions on this.

[0057] It should be understood that the lower limit value p1 is set to <1, and a specific value is selected according to usage requirements. For example, the lower limit value p1 is set to 65%. When the working heat exchange efficiency N of the frosting-prone heat exchanger is reduced to 65% of the maximum heat exchange efficiency (initial heat exchange efficiency N1), it can be considered that defrosting is required. At this time, the defrosting efficiency and economy are better.

[0058] The design principle of the defrosting control method of the present invention is that as the air conditioner continues to work, the frosting-prone heat exchanger may frost. When the frosting-prone heat exchanger frosts, the corresponding heat exchange efficiency decreases, and the N value also decays. Therefore, by continuously detecting and calculating the N value during the operation of the air conditioner, the change in the heat exchange efficiency of the frosting-prone heat exchanger can be understood, and the N value can be detected. It indicates that the heat exchange efficiency is relatively low and it can be considered that this is the time to start defrosting.

[0059] However, it is not rigorous to judge whether a frost-prone heat exchanger is frosted simply based on the heat exchange effect. When the air-conditioning unit is operating in a non-frost condition, but due to abnormal conditions such as excessive refrigerant filling and main throttle valve imbalance, the excessive amount of refrigerant in the frost-prone heat exchanger may also lead to poor heat exchange effect. At this time, additional judgment is required to avoid the phenomenon of "frost-free defrosting".

[0060] The present invention detects the working parameters of the heat exchanger prone to frost and calculates the heat exchange efficiency, combines the inlet air temperature and heat exchange efficiency of the heat exchanger prone to frost and other conditions to analyze the frosting situation of the unit, and effectively improves the accuracy of the defrosting entry timing.

[0061] like Figure 4 As shown, in some embodiments of the present invention, the defrost control method further includes:

[0062] determination Afterwards, in It means that the temperature of the air flow passing through the heat exchanger prone to frost is relatively high. At this time, it can be considered that the heat exchanger prone to frost will basically not frost. The resulting decrease in N value can be considered as abnormal conditions such as excessive refrigerant filling and main throttle valve imbalance. The main throttle valve 4 refers to a valve component connected in series between the outdoor heat exchanger 2 and the indoor heat exchanger 3 and used to adjust the flow rate of the refrigerant circulation loop. An electronic expansion valve is commonly used. By adjusting the opening of the main throttle valve of the air-conditioning unit, the working heat exchange efficiency N of the heat exchanger prone to frost can be effectively improved, so that the air-conditioning unit can operate in normal conditions.

[0063] The present invention analyzes the operating conditions of the air-conditioning unit through the attenuation of the heat exchange efficiency of the frosting-prone heat exchanger, and adjusts the opening of the main throttle valve 4 to improve the heat exchange efficiency, optimize the energy efficiency of the unit, and prevent the compressor 1 from inhaling liquid due to excessive refrigerant. The main throttle valve 4 of the air-conditioning unit is usually adjusted to reduce the opening. The reason is that when the amount of refrigerant is too much, the frosting-prone heat exchanger cannot fully exchange heat, resulting in a decrease in the pipe temperature t3 and a decrease in the heat exchange efficiency. At this time, the opening of the main throttle valve 4 should be reduced to reduce the refrigerant entering the frosting-prone heat exchanger, so that the refrigerant in the frosting-prone heat exchanger can be fully vaporized through heat exchange, and liquid refrigerant is prevented from entering the compressor 1.

[0064] Based on adjusting the main throttle valve of the air-conditioning unit, in some feasible embodiments of the present invention, the main throttle valve opening adjustment logic is as follows:

[0065] Calculate the change , k is the set opening;

[0066] According to the change Reduce the opening of the main throttle valve.

[0067] The principle of this design is that due to the low current heat exchange efficiency, the refrigerant does not exchange heat sufficiently in the frosting heat exchanger. If the opening of the main throttle valve 4 is increased, more refrigerant will flow into the frosting heat exchanger, causing the frosting heat exchanger to send out a large amount of liquid refrigerant, affecting the stability and safety of the compressor 1. However, reducing the opening of the main throttle valve 4 will reduce the refrigerant flowing into the frosting heat exchanger, and the refrigerant will exchange heat relatively fully in the frosting heat exchanger, thereby improving the heat exchange efficiency and ensuring the stability and safety of the compressor 1.

[0068] In addition, the change in opening is calculated by multiplying the difference between the current heat exchange efficiency and the initial heat exchange efficiency by the set opening K. This design can more accurately adjust the opening of the main throttle valve 4 to achieve fine control of the amount of refrigerant inside the frosting heat exchanger. The real-time difference between them has strong adaptability, so that the main throttle valve 4 can follow the changes in the working heat exchange efficiency N, respond quickly and adjust to maintain an appropriate amount of refrigerant.

[0069] like Figure 5 As shown, in some feasible embodiments of the present invention, the defrost control method further includes:

[0070] After the air conditioner enters defrosting operation, the fan of the frosting-prone heat exchanger is turned on, and the air conditioner switches the refrigerant flow direction to send the high-temperature refrigerant discharged from the compressor into the frosting-prone heat exchanger for heating and defrosting;

[0071] Determine whether the inlet and outlet temperature difference of the heat exchanger is prone to frost ;

[0072] If yes, it means that after the high-temperature refrigerant flows through the frosting-prone heat exchanger, the temperature has not changed significantly and the refrigerant has not absorbed enough cold air. It is considered that the defrosting of the frosting-prone heat exchanger is completed and the air-conditioning unit exits the defrosting operation.

[0073] The advantage of this design is that by detecting the inlet and outlet temperature difference of the frosting-prone heat exchanger, the heat transfer effect during the defrosting process can be intuitively reflected. When the temperature difference decreases to a certain extent, it means that the frost layer on the surface of the heat exchanger has been mostly or completely melted, and the defrosting process is nearing the end. By exiting the defrosting operation in time, the air-conditioning unit can resume normal operation, reduce the interruption time caused by defrosting, and maintain the stability of the indoor temperature. Compared with the defrosting exit judgment method based on time or other indirect parameters, the judgment based on the inlet and outlet temperature difference is more accurate, because the time required for defrosting may vary under different environmental conditions and unit operating conditions, and the temperature difference is a relatively stable physical quantity that can more accurately reflect the actual situation of defrosting.

[0074] like Figure 5 As shown, in some feasible embodiments of the present invention, the defrost control method further includes:

[0075] Determine whether the inlet and outlet temperature difference of the heat exchanger is prone to frost ;

[0076] If not, it means that after the high-temperature refrigerant flows through the frosting-prone heat exchanger, the temperature changes significantly, and the refrigerant absorbs more cold air. It is necessary to further judge the defrosting situation based on the heat exchange efficiency, detect the working parameters of the frosting-prone heat exchanger, and calculate the heat exchange efficiency of the frosting-prone heat exchanger as the defrosting heat exchange efficiency N2. It indicates that the heat exchange efficiency of the frosting heat exchanger is high, and there is basically no frost layer on the surface. The inlet and outlet temperature difference t5 of the frosting heat exchanger is caused by the low-temperature ambient wind introduced by the fan, and the air-conditioning unit exits the defrosting operation.

[0077] It should be understood that the upper limit value p2 is set to <1, and a specific value is selected according to usage requirements. For example, the upper limit value p2 is set to 95%. When the working heat exchange efficiency N of the frost-prone heat exchanger increases to 95% of the maximum heat exchange efficiency (initial heat exchange efficiency N1), it can be considered that defrosting needs to be exited. At this time, exiting defrost can ensure more thorough defrosting and there is almost no frost layer on the surface of the frost-prone heat exchanger.

[0078] The present invention considers the heat exchange efficiency and the inlet and outlet temperature difference of the heat exchanger prone to frost at the same time, provides double verification for the judgment of the defrost exit timing, helps to reduce the error that may be caused by a single condition judgment, improves the accuracy and reliability of the judgment, ensures that the defrost is exited in time when the frost layer is completely melted and does not affect the normal operation of the unit, and avoids the occurrence of excessive defrosting. Moreover, due to different environmental conditions and unit operating conditions, the time and effect required for defrosting may be different. This design can better adapt to various working conditions by making judgments based on the two conditions, ensuring that the unit can accurately and timely exit the defrost mode under different conditions.

[0079] Based on the above embodiment, the preferred scheme for the initial heat exchange efficiency is to detect the working parameters of the frosting-prone heat exchanger when the air-conditioning unit starts working and runs for a first set time, and calculate the heat exchange efficiency of the frosting-prone heat exchanger as the initial heat exchange efficiency N1.

[0080] The benefit of this design is that when the air conditioner unit starts to work and runs for the first set time, it can be considered that the air conditioner unit has been running stably, and the frosting heat exchanger has not been frosted, and the heat exchange efficiency is the highest. Since the heat exchange efficiency of the air conditioner unit may vary under different working conditions, the heat exchange efficiency when the air conditioner unit is running stably and not frosted is used as the initial heat exchange efficiency N1, which can more accurately match the normal operating conditions of the air conditioner unit, thereby improving the control accuracy of subsequent entry and exit of defrosting.

[0081] On this basis, in some feasible embodiments of the present invention, when the air-conditioning unit starts working and runs for a second set time, the working parameters of the frosting-prone heat exchanger are detected, and the heat exchange efficiency of the frosting-prone heat exchanger is calculated as the working heat exchange efficiency N; wherein the first set time is less than the second set time.

[0082] The advantage of this design is that since the accumulation of frost layer requires a certain amount of time, waiting for the second set time and then detecting the working parameters of the frosted heat exchanger in real time can reduce the system data processing volume, avoid collecting useless data, and optimize the control logic.

[0083] In some feasible embodiments of the present invention, adjusting the main throttle valve opening of the air conditioning unit further includes:

[0084] After adjusting the main throttle valve 4 each time, wait for the third set time, detect the working parameters of the frosting-prone heat exchanger, and calculate the heat exchange efficiency of the frosting-prone heat exchanger as the corrected heat exchange efficiency N3;

[0085] Determine whether ;

[0086] If yes, it means that the heat exchange efficiency of the frosting-prone heat exchanger is still low, and the process returns to the step of adjusting the opening of the main throttle valve 4 and continues to adjust the opening of the main throttle valve 4;

[0087] If not, it means that the heat exchange efficiency of the frosting-prone heat exchanger has been improved to a normal state, and the process returns to the step of detecting the working parameters of the frosting-prone heat exchanger, calculating the heat exchange efficiency of the frosting-prone heat exchanger as the working heat exchange efficiency N, and continuing to analyze the frosting condition of the unit based on conditions such as the inlet air temperature and heat exchange efficiency of the frosting-prone heat exchanger.

[0088] The advantage of this design is that after each adjustment of the main throttle valve 4, the third set time is waited to ensure the stability of the unit, and then the working parameters of the frosting heat exchanger are re-detected and the corrected heat exchange efficiency N3 is calculated. This dynamic adjustment method can more accurately reflect the adjustment effect and avoid misjudgment caused by the instability of the unit. In addition, by continuously monitoring and adjusting the heat exchange efficiency, frosting problems caused by low heat exchange efficiency can be discovered and prevented in time, effectively avoiding the impact of excessive frost on the performance of the heat exchanger. In addition, by optimizing the heat exchange efficiency, the energy consumption of the air-conditioning unit can be reduced and the overall energy efficiency can be improved.

[0089] Based on the above embodiment, the heat exchange efficiency of the frosting-prone heat exchanger is preferably calculated based on the working parameters such as the outlet air temperature t1, the inlet air temperature t2, and the tube temperature t3. The specific calculation formula is: .

[0090] The principle of this design is that theoretically, when the heat exchange effect is good, the refrigerant in the frosting heat exchanger is fully heat exchanged and vaporized, the outlet air temperature t1 of the frosting heat exchanger is low, and the tube temperature t3 is high. At this time, the calculated heat exchange efficiency is the highest. When the heat exchange effect decreases, the refrigerant in the frosting heat exchanger is insufficiently heat exchanged, the outlet air temperature t1 of the frosting heat exchanger increases, and the tube temperature t3 decreases. At this time, the calculated heat exchange efficiency decreases. The heat exchange efficiency changes with the thickness of the frost layer on the surface of the frosting heat exchanger, which can accurately reflect the current working status of the frosting heat exchanger.

[0091] Relying solely on the inlet and outlet air temperature difference (t2-t1) or the pipe temperature t3 to judge the defrost entry timing may not fully reflect the actual situation of the unit. The reason is that the inlet and outlet air temperature difference (t2-t1) or the pipe temperature t3 will fluctuate due to factors such as ambient temperature and refrigerant flow, resulting in defrost misjudgment. The heat exchange efficiency calculation scheme proposed by the present invention considers the two temperature differences (t2-t1) and (t2-t3) at the same time. By taking the ratio of these two temperature differences, it can more comprehensively evaluate the current working state of the air conditioning unit, thereby more accurately judging whether it is necessary to enter the defrost mode, and has strong adaptability.

[0092] For ease of understanding, Figure 6 As shown, taking an application example of the present invention as an example, the process of the entire defrosting control method is described in detail.

[0093] Air conditioning unit cooling operation;

[0094] After the cooling operation reaches the first set time, the outlet air temperature t1, the inlet air temperature t2, the pipe temperature t3, and the inlet and outlet temperature difference t5 of the indoor heat exchanger 3 are detected;

[0095] calculate , recorded as the initial heat transfer efficiency N1;

[0096] After the cooling operation reaches the second set time, the outlet air temperature t1, inlet air temperature t2, pipe temperature t3, and inlet and outlet temperature difference t5 of the indoor heat exchanger 3 are detected in real time, and the calculation is performed. , denoted as the working heat transfer efficiency N;

[0097] Determine whether , if not, return to continue testing and calculate the work efficiency N;

[0098] If yes, the air conditioner unit enters defrosting operation;

[0099] After entering the defrosting operation, the fan of the indoor heat exchanger 3 is turned on, the four-way valve 5 is opened to switch the refrigerant flow direction, and the high-temperature refrigerant is introduced into the indoor heat exchanger 3 for defrosting;

[0100] Determine whether the inlet and outlet temperature difference of the indoor heat exchanger 3 , if yes, the air conditioning unit will exit the defrosting operation;

[0101] If not, then detect the outlet air temperature t1, inlet air temperature t2, pipe temperature t3, and inlet and outlet temperature difference t5 of the indoor heat exchanger 3, and calculate , recorded as the corrected heat transfer efficiency N3;

[0102] Determine whether If not, return to re-judgment whether the inlet and outlet temperature difference of indoor heat exchanger 3 , if yes, the air conditioning unit will exit the defrosting operation.

[0103] like Figure 1 As shown, the present invention also proposes an air-conditioning unit, comprising: a compressor 1, an outdoor heat exchanger 2, a main throttle valve 4 and an indoor heat exchanger 3 which are sequentially connected to form a refrigerant circulation loop. The controller of the air-conditioning unit executes the above-mentioned defrost control method, by detecting the working parameters of the heat exchanger prone to frost and calculating the heat exchange efficiency, combining the inlet air temperature and heat exchange efficiency of the heat exchanger prone to frost and other conditions to analyze the frosting condition of the unit, thereby effectively improving the accuracy of the defrost entry timing.

[0104] In some embodiments, the air conditioning unit is a cold storage refrigeration unit. Since the target air supply temperature of the cold storage refrigeration unit is low and the cooling load is large, the indoor humid air is very easy to frost on the surface of the indoor heat exchanger, which seriously affects the normal operation of the unit. In addition, cold storage refrigeration units are often used to store items, and have high requirements for indoor ambient temperature, requiring the unit to be able to provide stable cooling for a long time. Since the defrost control method proposed in the present invention can effectively improve the accuracy of the defrost entry timing and the defrost exit timing, it is particularly suitable for cold storage refrigeration units to optimize the user experience.

[0105] For ease of understanding, an application example of the present invention is taken as an example to explain in detail the refrigerant flow direction of the air-conditioning unit.

[0106] like Figure 2 As shown, in the cooling state, the four-way valve 5 is de-energized, the exhaust side of the compressor 1 is connected to the outdoor heat exchanger 2 (condenser), and the suction side of the compressor 1 is connected to the indoor heat exchanger 3 (evaporator) through the gas-liquid separator 6. The high-temperature refrigerant discharged from the compressor 1 passes through the outdoor heat exchanger 2, the main throttle valve 4, the indoor heat exchanger 3 and the gas-liquid separator 6 in sequence, and finally returns to the compressor 1.

[0107] like Figure 3 As shown, during the defrosting operation (heating state), the four-way valve 5 is energized, the exhaust side of the compressor 1 is connected to the indoor heat exchanger 3 (condenser), and the suction side of the compressor 1 is connected to the outdoor heat exchanger 2 (condenser) through the gas-liquid separator 6. The high-temperature refrigerant discharged from the compressor 1 passes through the indoor heat exchanger 3, the main throttle valve 4, the outdoor heat exchanger 2 and the gas-liquid separator 6 in sequence, and finally returns to the compressor 1.

[0108] In order to extend the service life of the air-conditioning unit, multiple filters are designed in the refrigerant circulation loop. The filters absorb impurities in the loop to prevent pipe blockage or impurities from entering the compressor and causing abnormal operation of the unit.

[0109] It should be noted that the terms used above are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. When the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof. The order of execution of actions, steps, etc. in the devices and methods shown in the specification and the accompanying drawings can be implemented in any order as long as there is no special explicit limitation on the order and the output of the previous processing is not used in the subsequent processing. Similar terms of order used for the convenience of description do not mean that they must be implemented in such an order.

[0110] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A defrost control method, characterized in that: include: During the operation of the air conditioning unit, the working parameters of the heat exchanger prone to frost are detected, and the heat exchange efficiency of the heat exchanger prone to frost is calculated as the working heat exchange efficiency N; Determine whether ≤ set lower limit value p1; If so, when the air inlet temperature t2 of the frosting-prone heat exchanger is less than the set defrosting entry temperature t4, the air conditioning unit enters the defrosting operation, and when the air inlet temperature t2 is greater than or equal to the set defrosting entry temperature t4, the main throttle valve opening of the air conditioning unit is adjusted, and the change ΔB=k×(N1-N) is calculated, where k is the set opening, and the opening of the main throttle valve is reduced according to the change ΔB to improve the working heat exchange efficiency N of the frosting-prone heat exchanger; Adjusting the main throttle valve opening of the air conditioning unit also includes: After adjusting the main throttle valve each time, wait for a third set time, detect the working parameters of the frosting-prone heat exchanger, and calculate the heat exchange efficiency of the frosting-prone heat exchanger as a corrected heat exchange efficiency N3; Determine whether ≤ set lower limit value p1; If yes, return to the step of adjusting the main throttle valve opening; If not, return to the step of detecting the working parameters of the frosting-prone heat exchanger and calculating the heat exchange efficiency of the frosting-prone heat exchanger as the working heat exchange efficiency N; Wherein, N1 is the initial heat exchange efficiency of the frosting-prone heat exchanger, and the set lower limit value p1 is <1.

2. The defrost control method according to claim 1, characterized in that: Also includes: After the air conditioning unit enters defrosting operation, the fan of the frosting-prone heat exchanger is turned on, and the air conditioning unit switches the refrigerant flow direction; Determine whether the inlet and outlet temperature difference t5 of the frosting-prone heat exchanger is less than the set defrosting exit temperature difference t6; If yes, the air conditioning unit exits the defrosting operation.

3. The defrost control method according to claim 2, characterized in that: Also includes: Determine whether the inlet and outlet temperature difference t5 of the frosting-prone heat exchanger is less than the set defrosting exit temperature difference t6; If not, the working parameters of the frosting-prone heat exchanger are detected, and the heat exchange efficiency of the frosting-prone heat exchanger is calculated as the defrosting heat exchange efficiency N2. >When the upper limit value p2 is set, the air conditioning unit exits the defrosting operation; The set upper limit value p2 is less than 1.

4. The defrost control method according to claim 1, characterized in that: When the air conditioning unit starts to work and runs for a first set time, the working parameters of the frosting-prone heat exchanger are detected, and the heat exchange efficiency of the frosting-prone heat exchanger is calculated as the initial heat exchange efficiency N1.

5. The defrost control method according to claim 4, characterized in that: When the air conditioning unit starts to work and runs for a second set time, the working parameters of the frosting-prone heat exchanger are detected, and the heat exchange efficiency of the frosting-prone heat exchanger is calculated as the working heat exchange efficiency N; wherein the first set time is less than the second set time.

6. The defrost control method according to claim 1, characterized in that: The working parameters of the frosting-prone heat exchanger include the outlet air temperature t1, the inlet air temperature t2, and the tube temperature t3. The heat exchange efficiency of the frosting-prone heat exchanger is 7. The defrost control method according to any one of claims 1 to 6, characterized in that: When the air-conditioning unit is in a heating state, the heat exchanger that is prone to frost is an outdoor heat exchanger; and / or when the air-conditioning unit is in a cooling state, the heat exchanger that is prone to frost is an indoor heat exchanger.

8. Air conditioning units, including: A compressor, an outdoor heat exchanger, a main throttle valve and an indoor heat exchanger are connected in sequence to form a refrigerant circulation loop, characterized in that the controller of the air-conditioning unit executes the defrost control method described in any one of claims 1 to 7.

9. The air conditioning unit according to claim 8, characterized in that: The air conditioning unit is a cold storage refrigeration unit.

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