Air conditioning system and control method thereof

Abstract

The application provides an air conditioning system and a control method thereof. The air conditioning system comprises a compressor, an outdoor first heat exchanger, an outdoor second heat exchanger, an outdoor third heat exchanger and an indoor heat exchanger. The air conditioning system comprises a first boiling point refrigerant and a second boiling point refrigerant. The boiling point of the first boiling point refrigerant is lower than that of the second boiling point refrigerant. One end of the outdoor first heat exchanger is capable of being communicated to the exhaust end or the suction end of the compressor, and the other end is capable of being communicated to one end of the outdoor second heat exchanger and / or one end of the outdoor third heat exchanger. The other end of the outdoor second heat exchanger and the other end of the outdoor third heat exchanger are mixed and communicated to one end of the indoor heat exchanger. The other end of the indoor heat exchanger is capable of being communicated to the suction end or the exhaust end of the compressor. According to the application, the main condenser is not frosted or the frosting speed is reduced. Through the alternate operation of the two auxiliary heat exchangers, the system can realize defrosting and frost melting while stably heating, and the comfort of the indoor environment is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the air conditioning technical field, specifically relates to an air conditioning system and a control method thereof. BACKGROUND

[0002] From the perspective of system cycle, when the non-azeotropic working medium is applied to the air conditioning system, the non-azeotropic mixed working medium can approach the Lorenz cycle in the heat exchange process due to the temperature glide and the nonlinear relationship between temperature and enthalpy, so as to improve the cycle efficiency.

[0003] The conventional air conditioning system in the prior art has the problem that the outdoor unit stops when frosting and defrosting, which affects the indoor environmental comfort; the non-azeotropic working medium is applied to the heating and cooling system, but cannot simultaneously operate efficiently in the refrigeration and heating conditions, and other technical problems, therefore, the present application researches and designs an air conditioning system and a control method thereof. SUMMARY

[0004] Therefore, the present application aims to overcome the defects of the conventional air conditioning system in the prior art, which has the problem that the outdoor unit stops when frosting and defrosting, which affects the indoor environmental comfort, thereby providing an air conditioning system and a control method thereof.

[0005] In order to solve the above problems, the present application provides an air conditioning system, which comprises:

[0006] A compressor, an outdoor first heat exchanger, an outdoor second heat exchanger, an outdoor third heat exchanger, an indoor heat exchanger and a first throttling device, and the air conditioning system comprises a first boiling point refrigerant and a second boiling point refrigerant, the boiling point of the first boiling point refrigerant is lower than the boiling point of the second boiling point refrigerant, one end of the outdoor first heat exchanger can be connected to the discharge end or the suction end of the compressor, and the other end can be connected to one end of the outdoor second heat exchanger and / or one end of the outdoor third heat exchanger.

[0007] The other end of the outdoor second heat exchanger is connected to the other end of the outdoor third heat exchanger, and then connected to one end of the first throttling device, the other end of the first throttling device is connected to one end of the indoor heat exchanger, and the other end of the indoor heat exchanger can be selectively connected to the suction end or the discharge end of the compressor.

[0008] In some embodiments, one end of the outdoor first heat exchanger can be selectively connected to the discharge end or the suction end of the compressor through a first pipeline, and the other end can be connected to one end of the outdoor second heat exchanger and / or one end of the outdoor third heat exchanger through a second pipeline, and the outdoor second heat exchanger is connected in parallel with the outdoor third heat exchanger.

[0009] In some embodiments, the outdoor second heat exchanger is located on a third pipeline, the outdoor third heat exchanger is located on a fourth pipeline, the third pipeline and the fourth pipeline are in parallel, one end of the third pipeline and one end of the fourth pipeline are communicated and then communicated with the second pipeline, and the other end of the third pipeline and the other end of the fourth pipeline are communicated and then capable of being communicated with one end of the indoor heat exchanger.

[0010] In some embodiments, a first control valve is arranged on the third pipeline, and a second control valve is arranged on the fourth pipeline.

[0011] In some embodiments, a fifth pipeline, a sixth pipeline and a seventh pipeline are further included, the third pipeline and the fourth pipeline are communicated to one end of the throttling device through the fifth pipeline after being merged, the other end of the throttling device is communicated to one end of the indoor heat exchanger through the sixth pipeline, and the other end of the indoor heat exchanger is communicated to the suction end or the exhaust end of the compressor through the seventh pipeline.

[0012] In some embodiments, a four-way valve is further included, the four-way valve includes an E end, an S end, a C end and a D end, the E end is communicated with the seventh pipeline, the S end is communicated with the suction end of the compressor, the C end is communicated with the first pipeline, the D end is communicated with the exhaust end of the compressor, a first communication state of the four-way valve is that the E end is communicated with the S end, and at the same time, the C end is communicated with the D end, at this time, the indoor operation is in a refrigeration state, a second communication state of the four-way valve is that the E end is communicated with the D end, and at the same time, the S end is communicated with the C end, at this time, the indoor operation is in a heating state, and the four-way valve is capable of being switched between the first communication state and the second communication state.

[0013] In some embodiments, a first fan is further included, the first fan is capable of driving part of air flow outside to flow through the outdoor first heat exchanger, part of air flow to flow through the outdoor second heat exchanger, and part of air flow to flow through the outdoor third heat exchanger.

[0014] A second fan is further included, the second fan is capable of driving air flow inside to flow through the indoor heat exchanger.

[0015] In some embodiments, the sixth pipeline is provided with a third control valve, and the seventh pipeline is provided with a sixth control valve, the air conditioning system further comprises an eighth pipeline and a ninth pipeline, one end of the eighth pipeline is communicated to the sixth pipeline and located between the third control valve and the throttling device, the other end is connected to the seventh pipeline and located between the sixth control valve and the indoor heat exchanger, one end of the ninth pipeline is communicated to the sixth pipeline and located between the indoor heat exchanger and the third control valve, the other end is connected to the seventh pipeline and located between the sixth control valve and the four-way valve, the eighth pipeline is provided with a fourth control valve, and the ninth pipeline is provided with a fifth control valve; the seventh pipeline is arranged close to the second fan relative to the sixth pipeline, and the ninth pipeline is arranged away from the second fan relative to the eighth pipeline.

[0016] The application also provides a control method of the air conditioning system as described in any one of the preceding embodiments, which comprises:

[0017] a detection step of detecting the operation mode of the air conditioning system, and the temperature Tout of the outdoor environment, and the refrigerant inlet temperature Tin of the outdoor second heat exchanger or the outdoor third heat exchanger in the heating mode;

[0018] a judgment step of judging the relationship between Tout and a first preset value T1, and the relationship between Tin and a second preset value T2 and a third preset value T3; wherein T2>T3;

[0019] a control step, when the first control valve and the second control valve are further included:

[0020] when the air conditioner operates in the cooling mode: controlling the first control valve and the second control valve to be both opened; when the air conditioner operates in the heating mode: and when Tout≥T1 and Tin≥T2, controlling the first control valve and the second control valve to be both opened; and when Tout≥T1 and Tin<T3 within t1 time, or when Tout<T1 and Tin<T2 within t1 time, controlling one of the first control valve and the second control valve to be opened and the other to be closed, wherein t1 is a first preset time.

[0021] In some embodiments, in the control step, when the air conditioner operates in the heating mode, and when Tout≥T1 and Tin<T3 within t1 time, or when Tout<T1 and Tin<T2 within t1 time, the first control valve is controlled to be opened and the second control valve is controlled to be closed, and after t2 time, t2 is a second preset time;

[0022] The detection step can further detect the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger.

[0023] The judging step can further judge whether a first pressure difference between the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger is greater than or equal to a first preset pressure difference value.

[0024] The controlling step can further control the first control valve to be closed and the second control valve to be opened when the first pressure difference is greater than or equal to the first preset pressure difference value, and maintain the first control valve to be opened and the second control valve to be closed when the first pressure difference is less than the first preset pressure difference value.

[0025] In some embodiments, the controlling step can further control the outdoor second heat exchanger to be heated defrosted when the first pressure difference is greater than or equal to the first preset pressure difference value, and the first control valve is controlled to be closed and the second control valve is controlled to be opened.

[0026] In some embodiments, in the controlling step, when the air conditioner operates in the heating mode, and when Tout≥T1 and Tin

[0027] The detecting step can further detect the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger.

[0028] The judging step can further judge whether a second pressure difference between the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger is greater than or equal to a second preset pressure difference value.

[0029] The controlling step can further control the first control valve to be opened and the second control valve to be closed when the second pressure difference is greater than or equal to the second preset pressure difference value, and maintain the first control valve to be closed and the second control valve to be opened when the second pressure difference is less than the second preset pressure difference value.

[0030] In some embodiments, the controlling step can further control the outdoor third heat exchanger to be heated defrosted when the second pressure difference is greater than or equal to the second preset pressure difference value, and the first control valve is controlled to be opened and the second control valve is controlled to be closed.

[0031] In some embodiments, T3

[0032] The control step can also control the first control valve and the second control valve to be opened, and control the four-way valve to reverse and switch to the refrigeration mode to heat at least one of the outdoor first heat exchanger, the outdoor second heat exchanger and the outdoor second heat exchanger when the air conditioner operates in the heating mode when Tout < T4, and T4 < T3.

[0033] In some embodiments, when the air conditioning system further comprises a four-way valve, a third control valve, a fourth control valve, a fifth control valve and a sixth control valve: the control step can also control the third control valve to be opened and the sixth control valve to be opened, and control the fourth control valve and the fifth control valve to be closed when the air conditioner operates in the refrigeration mode; control the third control valve and the sixth control valve to be closed, and control the fourth control valve and the fifth control valve to be opened when the air conditioner operates in the heating mode.

[0034] The air conditioning system and the control method thereof provided by the application have the following beneficial effects:

[0035] 1. The system of the application uses non-azeotropic working medium, fully utilizes the temperature glide characteristics of non-azeotropic working medium, and divides the outdoor heat exchanger into three parts (one main heat exchanger and two auxiliary heat exchangers, the main heat exchanger and the auxiliary heat exchanger are arranged in series in the windward area, and the two auxiliary heat exchangers are arranged in parallel in the flow direction), sacrifices a small part of the heat exchange area, so that the main heat exchange area does not frost. When heating, the refrigerant enters from one end of one auxiliary heat exchanger, the low-boiling-point refrigerant evaporates in the auxiliary heat exchanger first, the surface temperature is low and frost is easy to form, but due to the temperature glide effect, the temperature of the refrigerant gradually rises during the heat exchange in the auxiliary heat exchanger, so that the main condenser does not frost or the frost formation speed is reduced. When one auxiliary heat exchanger defrosts, the other auxiliary heat exchanger works, and through the rotation of the two auxiliary heat exchangers, the system can realize defrosting and defrosting while stably heating, and improve the comfort of the indoor environment.

[0036] 2. The application also sets four two-way valves and corresponding switching pipelines at the inlet and outlet of the indoor heat exchanger, so that the system can realize counter-flow heat exchange in the refrigeration and heating conditions, has good heat exchange efficiency, and reduces the irreversible loss in the heat exchange process. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a non-azeotropic working medium system cycle schematic diagram (refrigeration mode) of the main embodiment of the application.

[0038] Figure 2 It is a non-azeotropic working medium system cycle schematic diagram (general heating mode) of the main embodiment of the application.

[0039] Figure 3This is a schematic diagram of the circulation of the non-azeotropic working fluid system in the main embodiment of the present invention (low-temperature heating mode);

[0040] Figure 4 This is a schematic diagram of the circulation of the non-azeotropic working fluid system in the main embodiment of the present invention (low temperature heating mode and simultaneous defrosting in the wind 21a);

[0041] Figure 5 This is a schematic diagram of the cooling mode cycle (cooling mode) of the alternative embodiment of the present invention;

[0042] Figure 6 This is a schematic diagram of the heating mode cycle (general heating mode) of the alternative embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram of the cooling mode cycle (low-temperature heating mode) of the alternative embodiment of the present invention;

[0044] Figure 8 This is a schematic diagram of the heating mode cycle of the alternative embodiment of the present invention (low temperature heating mode and simultaneous defrosting in the wind 21a).

[0045] The reference numerals in the attached figures are as follows:

[0046] 10. Compressor; 21. Outdoor first heat exchanger; 21a. Outdoor second heat exchanger; 21b. Outdoor third heat exchanger; 31. Throttling device; 41. Indoor heat exchanger; 51. Four-way valve; E, E end; S, S end; C, C end; D, D end; 61. First fan; 62. Second fan; 71. First control valve; 72. Second control valve; 73. Third control valve; 74. Fourth control valve; 75. Fifth control valve; 76. Sixth control valve;

[0047] 101. First pipeline; 102. Second pipeline; 103. Third pipeline; 104. Fourth pipeline; 105. Fifth pipeline; 106. Sixth pipeline; 107. Seventh pipeline; 108. Eighth pipeline; 109. Ninth pipeline. Detailed Implementation

[0048] Main embodiment, such as Figures 1-8 As shown, the present invention provides an air conditioning system, which includes:

[0049] The system includes a compressor 10, an outdoor first heat exchanger 21, an outdoor second heat exchanger 21a, an outdoor third heat exchanger 21b, an indoor heat exchanger 41, and a first throttling device 31. The air conditioning system includes a first boiling point refrigerant and a second boiling point refrigerant, wherein the boiling point of the first boiling point refrigerant is less than the boiling point of the second boiling point refrigerant. One end of the outdoor first heat exchanger 21 can be connected to the exhaust end or the suction end of the compressor 10, and the other end can be connected to one end of the outdoor second heat exchanger 21a and / or one end of the outdoor third heat exchanger 21b.

[0050] The other end of the outdoor second heat exchanger 21a is connected to the other end of the outdoor third heat exchanger 21b, and can then be connected to one end of the first throttling device 31. The other end of the first throttling device 31 is connected to one end of the indoor heat exchanger 41, and the other end of the indoor heat exchanger 41 can be selectively connected to the suction end or the exhaust end of the compressor 10.

[0051] This invention employs a non-azeotropic refrigerant, fully utilizing its temperature glide characteristics. The outdoor heat exchanger is divided into three parts (one main heat exchanger and two auxiliary heat exchangers, arranged in series on the windward side and in parallel on the flow direction), sacrificing a small portion of the heat exchange area to prevent frost formation on the main heat exchange surface. During heating operation, the refrigerant enters from one end of an auxiliary heat exchanger. The low-boiling-point refrigerant evaporates first in the auxiliary heat exchanger, where its low surface temperature makes it prone to frost formation. However, due to the temperature glide effect, the refrigerant temperature gradually increases during heat exchange within the auxiliary heat exchanger, preventing or slowing down frost formation on the main condenser. While one auxiliary heat exchanger defrosts, the other operates. This alternating operation of the two auxiliary heat exchangers allows the system to achieve stable heating while simultaneously performing defrosting and frost removal functions, improving indoor comfort.

[0052] 1. This invention differs from conventional refrigeration systems. This proposal uses a non-azeotropic refrigerant with a large glide temperature, which is greater than 5°C and less than the temperature difference between the inlet and outlet air. This solves the problem of conventional air conditioning systems shutting down during heating operation due to outdoor unit frosting and defrosting, thus affecting indoor environmental comfort.

[0053] 2. This invention improves the problem of air conditioning systems experiencing performance degradation and reduced indoor comfort due to frosting during heating operation, and solves the problem that non-azeotropic refrigerants cannot achieve efficient operation in both cooling and heating modes when used in heating and cooling systems.

[0054] 3. This invention improves the heat exchange performance of non-azeotropic working fluids in heat exchangers, makes full use of the temperature glide characteristics of non-azeotropic working fluids, makes the heat exchange process approximate the Lorenz cycle, reduces the heat exchange temperature difference, reduces irreversible losses in the heat exchange process, and improves heat exchange efficiency.

[0055] like Figure 1 The air conditioning system shown includes a compressor 10, an outdoor first heat exchanger 21, an outdoor second heat exchanger 21a, an outdoor third heat exchanger 21b, a throttling device 31, an indoor heat exchanger 41, a four-way valve 51, a first fan 61, a second fan 62, a first control valve 71, and a second control valve 72, all preferably two-way valves.

[0056] The non-azeotropic refrigerant is used in the system, and the standard boiling points of the non-azeotropic refrigerant have certain differences, so that the heat exchange characteristics in the heat exchange process are different from those of pure working medium (or near-azeotropic working medium). In the evaporation process, the evaporation temperature of the non-azeotropic refrigerant gradually increases, while the temperature of the external heat exchange fluid (air or water) gradually decreases; similarly, in the condensation process, the temperature of the non-azeotropic refrigerant gradually decreases, while the temperature of the heat exchange fluid (air or water) gradually increases. Therefore, in order to fully utilize the above-mentioned glide characteristics of the non-azeotropic working medium, the heat exchange process of the non-azeotropic working medium is preferably counter-flow heat exchange, and the non-azeotropic working medium is applied to the scene of heating and defrosting, which has a significant effect on inhibiting the performance degradation of the system caused by the frosting of the heat exchanger.

[0057] In some embodiments, one end of the outdoor first heat exchanger 21 is selectively connected to the discharge end or the suction end of the compressor 10 through a first pipeline 101, the other end is connected to one end of the outdoor second heat exchanger 21a and / or one end of the outdoor third heat exchanger 21b through a second pipeline 102, and the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b are connected in parallel. This is the preferred arrangement form of the outdoor first heat exchanger, the outdoor second heat exchanger and the outdoor third heat exchanger of the present application, which forms a connection mode in which the outdoor first heat exchanger is connected in series with the outdoor second and / or third heat exchangers, and the outdoor second heat exchanger and the outdoor third heat exchanger are connected in parallel. Defrosting and defrosting can be realized by sacrificing a small part of the heat exchange area. When heating, there are three heat exchangers outside, and all of them act as evaporators. Due to the temperature glide characteristics of the non-azeotropic working medium, the temperature gradually increases during heat exchange in the evaporator, so that the evaporation temperature of the refrigerant in the small heat exchanger is lower than the dew point temperature of the outdoor working condition, and the outdoor small heat exchanger is frosted. Due to the temperature glide characteristics, the temperature of the refrigerant out of the outdoor second heat exchanger 21a is higher than the dew point temperature, and then the refrigerant enters the outdoor first heat exchanger 21 for heat exchange. Since the temperature of the refrigerant in the heat exchange is higher than the dew point temperature and lower than the outdoor dry-bulb temperature, the outdoor first heat exchanger will not be frosted. When the frost layer of the outdoor second heat exchanger 21a is accumulated to a certain extent, the outdoor third heat exchanger 21b replaces the outdoor second heat exchanger 21a to work. Thus, the rotation of frosting and defrosting is realized without stopping.

[0058] In some embodiments, the outdoor second heat exchanger 21a is located on a third pipeline 103, the outdoor third heat exchanger 21b is located on a fourth pipeline 104, the third pipeline 103 and the fourth pipeline 104 are connected in parallel, one end of the third pipeline 103 and one end of the fourth pipeline 104 are connected and then connected to the second pipeline 102, and the other end of the third pipeline 103 and the other end of the fourth pipeline 104 are connected and then connected to one end of the indoor heat exchanger 41.

[0059] The application can guide the compressor exhaust to the outdoor first heat exchanger 21 to condense and release heat in the refrigeration mode, and the first pipeline can also guide the refrigerant from the outdoor first heat exchanger to the compressor suction end in the heating mode, the second pipeline can be used to guide the mixed refrigerant from the third pipeline and the fourth pipeline to the outdoor first heat exchanger in the heating mode, and the third pipeline and the fourth pipeline are used to connect the outdoor second heat exchanger and the outdoor third heat exchanger in parallel, so that the two heat exchangers or only one heat exchanger is selected to be opened according to different working conditions, and the defrosting effect is realized.

[0060] In some embodiments, the third pipeline 103 is provided with a first control valve 71, and the fourth pipeline 104 is provided with a second control valve 72. The first control valve provided on the third pipeline in communication with the outdoor second heat exchanger and the second control valve provided on the fourth pipeline in communication with the outdoor third heat exchanger can control whether the outdoor second heat exchanger and the outdoor third heat exchanger are connected or not; two heat exchangers or only one heat exchanger can be selected to be opened according to different working conditions, and the defrosting effect is realized.

[0061] In some embodiments, the third pipeline 103 and the fourth pipeline 104 are combined and communicated to one end of the throttling device 31 through the fifth pipeline 105, the other end of the throttling device 31 is communicated to one end of the indoor heat exchanger 41 through the sixth pipeline 106, and the other end of the indoor heat exchanger 41 is communicated to the suction end or the exhaust end of the compressor 10 through the seventh pipeline 107. This is a further preferred structure of the application, the fifth pipeline and the sixth pipeline can effectively connect the outdoor second heat exchanger and the outdoor third heat exchanger with the indoor heat exchanger, the throttling device can throttle and depressurize the refrigerant in the indoor and outdoor, and the seventh pipeline can connect the indoor heat exchanger with the compressor, the indoor heat exchanger is connected with the suction end of the compressor in the refrigeration mode, and the indoor heat exchanger is connected with the exhaust end of the compressor in the heating mode.

[0062] In some embodiments, a four-way valve 51 is further included, which comprises an E end E, an S end S, a C end C and a D end D, the E end E is communicated with the seventh pipeline 107, the S end S is communicated with the suction end of the compressor 10, the C end C is communicated with the first pipeline 101, the D end D is communicated with the discharge end of the compressor 10, the first communication state of the four-way valve is that the E end E is communicated with the S end S, while the C end C is communicated with the D end D, at this time, the indoor operation is in the refrigeration state, the second communication state of the four-way valve is that the E end E is communicated with the D end D, while the S end S is communicated with the C end C, at this time, the indoor operation is in the heating state; the four-way valve 51 can be switched between the first communication state and the second communication state. It is a further preferred structure form of the present application, through the four-way valve, the indoor heat exchanger, the outdoor first heat exchanger and the compressor can be connected into an integral system, and switching can be performed to realize the switching control between the refrigeration mode and the heating mode.

[0063] In some embodiments, a first fan 61 is further included, which can drive part of the outdoor airflow to flow through the outdoor first heat exchanger 21, part of the airflow to flow through the outdoor second heat exchanger 21a, and part of the airflow to flow through the outdoor third heat exchanger 21b.

[0064] A second fan 62 is further included, which can drive the indoor airflow to flow through the indoor heat exchanger 41.

[0065] Through the setting of the first fan, the outdoor airflow can be driven to enter the outdoor first heat exchanger, the outdoor second heat exchanger and the outdoor third heat exchanger for heat exchange, and through the setting of the second fan, the indoor airflow can be driven to enter the indoor heat exchanger for heat exchange.

[0066] In some embodiments, the sixth pipeline 106 is provided with a third control valve 73, the seventh pipeline 107 is provided with a sixth control valve 76, the air conditioning system further comprises an eighth pipeline 108 and a ninth pipeline 109, one end of the eighth pipeline 108 is communicated to the sixth pipeline 106 and located between the third control valve 73 and the throttling device 31, the other end is connected to the seventh pipeline 107 and located between the sixth control valve 76 and the indoor heat exchanger 41, one end of the ninth pipeline 109 is communicated to the sixth pipeline 106 and located between the indoor heat exchanger 41 and the third control valve 73, the other end is connected to the seventh pipeline 107 and located between the sixth control valve 76 and the four-way valve 51, the eighth pipeline 108 is provided with a fourth control valve 74, and the ninth pipeline 109 is provided with a fifth control valve 75; the seventh pipeline 107 is arranged relative to the sixth pipeline 106 close to the second fan 62, and the ninth pipeline 109 is arranged relative to the eighth pipeline 108 away from the second fan 62.

[0067] The present disclosure can realize reverse flow heat exchange of the indoor heat exchanger under the refrigeration and heating conditions by controlling the eighth pipeline and the ninth pipeline arranged at the inlet and outlet of the indoor heat exchanger, thereby reducing the heat exchange temperature difference and irreversible loss in the heat exchange process.

[0068] The present disclosure can realize reverse flow heat exchange of the indoor heat exchanger under the refrigeration and heating conditions by controlling the third control valve 73, the fourth control valve 74, the fifth control valve 75 and the sixth control valve 76 arranged at the inlet and outlet of the indoor heat exchanger, thereby reducing the heat exchange temperature difference and irreversible loss in the heat exchange process.

[0069] The present disclosure further provides a control method of the air conditioning system as described in any one of the preceding embodiments, which comprises:

[0070] a detection step of detecting the operation mode of the air conditioning system and the temperature Tout of the outdoor environment and the inlet temperature Tin of the second and third outdoor heat exchangers, wherein Tin specifically refers to the inlet temperature of the second and third outdoor heat exchangers under the heating condition;

[0071] a judgment step of judging the relationship between Tout and a first preset value T1 and the relationship between Tin and a second preset value T2 and a third preset value T3; wherein T2>T3;

[0072] a control step, when the first control valve 71 and the second control valve 72 are further included:

[0073] When the air conditioner operates in the cooling mode: control the first control valve 71 and the second control valve 72 to be opened; when the air conditioner operates in the heating mode: and when Tout is greater than or equal to T1 and Tin is greater than or equal to T2, control the first control valve 71 and the second control valve 72 to be opened; and when Tout is greater than or equal to T1 and Tin is less than T3 within t1 time, or when Tout is less than T1 and Tin is less than T2 within t1 time, control one of the first control valve 71 and the second control valve 72 to be opened and the other to be closed, wherein t1 is a first preset time.

[0074] The system adopts non-azeotropic working medium, fully utilizes the temperature glide characteristics of the non-azeotropic working medium, and simultaneously divides the outdoor heat exchanger into three parts (one main heat exchanger and two auxiliary heat exchangers, the main heat exchanger and the auxiliary heat exchanger are arranged in series in the windward area, and the two auxiliary heat exchangers are arranged in parallel in the flow direction), sacrifices a small part of the heat exchange area, so that the main heat exchange area does not frost. When heating, the refrigerant enters from one end of one auxiliary heat exchanger, the low-boiling-point refrigerant evaporates in the auxiliary heat exchanger first, the surface temperature is low and frost is easy to form, but due to the temperature glide effect, the temperature of the refrigerant gradually rises during the heat exchange in the auxiliary heat exchanger, so that the main condenser does not frost or the frost formation speed is slowed down. When one auxiliary heat exchanger defrosts, the other auxiliary heat exchanger works, and through the rotation of the two auxiliary heat exchangers, the system can realize defrosting and defrosting function while stably heating, and improve the comfort of the indoor environment.

[0075] Generally, for pure working medium refrigerant, when the evaporation temperature is lower than 0℃, the outdoor heat exchanger is easy to frost, and the frost layer on the surface of the outdoor unit evaporator is thicker and thicker, and the heat exchange is worse and worse, so that the heating effect is not good, and even the machine stops. However, for non-azeotropic working medium, it has temperature glide characteristics, and the evaporation temperature gradually rises during heat exchange, so at the inlet of the evaporator, the evaporation temperature is low and frost is easy to form, but as the evaporation process proceeds, in the latter half of the heat exchanger, the temperature of the refrigerant slides to above the dew point temperature of the outdoor environment, but is still lower than the dry-bulb temperature of the outdoor environment, at this time, frost is not easy to form in the latter half of the evaporator.

[0076] The present application utilizes the above-mentioned characteristics of non-azeotropic working medium, and divides the outdoor heat exchanger into three parts, so that during heating, frost only occurs on the two auxiliary heat exchangers, and the main heat exchanger is ensured not to frost or the frost formation of the main heat exchanger is delayed, so that the heating process can still proceed normally. The two auxiliary heat exchangers frost and defrost alternately, and the main heat exchanger always operates normally.

[0077] 1. This invention differs from conventional refrigeration systems. This proposal uses a non-azeotropic refrigerant with a large glide temperature, which is greater than 5°C and less than the temperature difference between the inlet and outlet air. This solves the problem of conventional air conditioning systems shutting down during heating operation due to outdoor unit frosting and defrosting, thus affecting indoor environmental comfort.

[0078] 2. This invention improves the problem of air conditioning systems experiencing performance degradation and reduced indoor comfort due to frosting during heating operation, and solves the problem that non-azeotropic refrigerants cannot achieve efficient operation in both cooling and heating modes when used in heating and cooling systems.

[0079] 3. This invention improves the heat exchange performance of non-azeotropic working fluids in heat exchangers, makes full use of the temperature glide characteristics of non-azeotropic working fluids, makes the heat exchange process approximate the Lorenz cycle, reduces the heat exchange temperature difference, reduces irreversible losses in the heat exchange process, and improves heat exchange efficiency.

[0080] like Figure 1 The air conditioning system shown includes a compressor 10, an outdoor first heat exchanger 21, an outdoor second heat exchanger 21a, an outdoor third heat exchanger 21b, a throttling device 31, an indoor heat exchanger 41, a four-way valve 51, a first fan 61, a second fan 62, a first control valve 71, and a second control valve 72, all preferably two-way valves.

[0081] This system uses a non-azeotropic refrigerant, which has a slightly different standard boiling point. Therefore, it exhibits different heat exchange characteristics compared to pure (or near-azeotropic) refrigerants. During evaporation, the evaporation temperature of the non-azeotropic refrigerant gradually increases, while the temperature of the external heat exchange fluid (air or water) gradually decreases. Similarly, during condensation, the temperature of the non-azeotropic refrigerant gradually decreases, while the temperature of the heat exchange fluid (air or water) gradually increases. Therefore, to fully utilize the aforementioned glide characteristics of the non-azeotropic refrigerant, the heat exchange process is best performed in counter-current flow. Applying this to defrosting scenarios significantly reduces system performance degradation caused by frost buildup on the heat exchanger. The specific implementation method is as follows:

[0082] 1. Cooling mode, such as Figure 1 Both the first control valve 71 and the second control valve 72 are turned on.

[0083] The high-temperature, high-pressure refrigerant discharged from the compressor 10 enters the outdoor first heat exchanger 21. After heat exchange in the outdoor first heat exchanger 21, it is divided into two paths, which enter the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b respectively. Then the two refrigerants are mixed. The mixed refrigerant is throttled and depressurized by the throttling device 31, and then enters the indoor heat exchanger 41. After heat exchange, it enters the suction port of the compressor 10 through the four-way valve 51, where it is compressed into a high-temperature, high-pressure state, thus completing the entire refrigeration cycle.

[0084] 2. Heating mode, divided into three cases, divided into general heating condition, low temperature heating condition and adverse condition heating, low temperature and adverse heating condition need to defrost defrosting. The control system of air conditioner detects the temperature Tout of outdoor environment, the inlet temperature Tin of outdoor heat exchanger, if it is detected that Tout > 5℃, Tin > 0℃, the outdoor heat exchanger will not frost, the system runs general heating mode; If it is detected that Tout < 5℃, and continuously for one minute Tin < 0℃ or Tout > 5℃ and Tin < -2℃, it is indicated that the outdoor heat exchanger inlet will frost. The specific operation mode is as follows:

[0085] 2.1 Detection device detects that Tout > 5℃ and Tin > 0℃, runs general heating mode, at this time the first control valve 71, the second control valve 72 are all on, as shown in Figure 2 .

[0086] The high temperature and high pressure refrigerant discharged by the compressor 10 enters the indoor heat exchanger 41 through the D, E pipes of the four-way valve, and after heat exchange, is throttled and reduced in pressure by the throttling device 31, and is divided into two paths, which respectively enter the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b to exchange heat, and after heat exchange, the two paths of refrigerant are mixed, and the mixed refrigerant enters the outdoor first heat exchanger 21 to exchange heat, and finally enters the suction port of the compressor 10 through the C, S pipes of the four-way valve 51, and is compressed into a high temperature and high pressure state in the compressor, thereby completing the entire heating cycle.

[0087] 2.2 Detection device detects that Tout > 5℃ and continuously for one minute Tin < -2℃, or Tout < 5℃ and continuously for one minute Tin < 0℃, it is indicated that the outdoor preferred heat exchanger inlet is prone to frost, and the low temperature heating mode needs to be run, first the first control valve 71 is on, and the second control valve 72 is closed, when the differential pressure meter detects that the inlet and outlet air pressure difference of the outdoor second heat exchanger 21a increases to a certain value, it is indicated that the outdoor second heat exchanger 21a surface is frosted, and defrosting treatment is needed, then the outdoor third heat exchanger 21b replaces the outdoor second heat exchanger 21a to work, at this time the first control valve 71 is closed, and the second control valve 72 is on, the specific real-time mode is as follows:

[0088] a) First, the first control valve 71 is on, and the second control valve 72 is closed as shown in Figure 3 .

[0089] The high temperature and high pressure refrigerant discharged by the compressor 10 enters the indoor heat exchanger 41 through the D, E pipes of the four-way valve, and after heat exchange, is throttled and reduced in pressure by the throttling device 31, and is divided into two paths, which respectively enter the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b to exchange heat, and after heat exchange, the two paths of refrigerant are mixed, and the mixed refrigerant enters the outdoor first heat exchanger 21 to exchange heat, and finally enters the suction port of the compressor 10 through the C, S pipes of the four-way valve 51, and is compressed into a high temperature and high pressure state in the compressor, thereby completing the entire heating cycle.

[0090] In this mode, due to the low temperature of the outdoor environment, the inlet temperature Tin of the outdoor second heat exchanger 21a is lower than the dew point temperature of the outdoor environment, so that the outdoor second heat exchanger 21a evaporator is easy to frost, but due to the temperature glide characteristics of the non-azeotropic working fluid, the temperature of the refrigerant gradually increases in the direction of the outdoor second heat exchanger 21a, and through the early heat exchanger matching, it is ensured that the temperature of the refrigerant at the outlet of the outdoor second heat exchanger 21a is greater than the dew point temperature of the outdoor environment and less than the dry-bulb temperature of the outdoor environment, so that when the refrigerant enters the outdoor first heat exchanger 21 for heat exchange, the outdoor first heat exchanger 21 will not frost, thereby ensuring the smooth operation of the heating process. At the same time, with the continuous heat exchange, the frost layer on the surface of the outdoor second heat exchanger 21a becomes thicker and thicker, and when the differential pressure between the inlet and outlet air of the outdoor second heat exchanger 21a detected by the differential pressure gauge increases to a certain value, it indicates that the frost layer is relatively thick at this time, which affects the heat exchange performance of the heat exchanger, and the outdoor second heat exchanger 21a needs to be defrosted. Therefore, the valve needs to be switched, so that the first control valve 71 is closed and the second control valve 72 is turned on, and the outdoor third heat exchanger 21b works. The idle outdoor second heat exchanger 21a can be defrosted by electric heating (which can be provided).

[0091] In some embodiments, in the control step, when the air conditioner operates in the heating mode, and when Tout≥T1 and Tin<T3 for t1 consecutive time, or when Tout<T1 and Tin<T2 for t1 consecutive time, the first control valve 71 is opened and the second control valve 72 is closed, and after t2 time, t2 is the second preset time; T3 is preferably -2℃, T2 is preferably 0℃, and T1 is preferably 5℃.

[0092] The detection step can also detect the inlet air pressure and outlet air pressure of the outdoor second heat exchanger 21a.

[0093] The judgment step can also judge whether the first pressure difference between the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger 21a is greater than or equal to the first preset pressure difference value.

[0094] The control step can also control the first control valve 71 to be closed and the second control valve 72 to be opened when the first pressure difference is greater than or equal to the first preset pressure difference value, and control the first control valve 71 to be opened and the second control valve 72 to be closed when the first pressure difference is less than the first preset pressure difference value.

[0095] In some embodiments, the control step can also control the heating defrosting of the outdoor second heat exchanger 21a when the first pressure difference is greater than or equal to the preset pressure difference value and the first control valve 71 is controlled to be closed and the second control valve 72 is controlled to be opened.

[0096] b) the first control valve 71 is closed and the second control valve 72 is open, as shown in Figure 4

[0097] When the frost layer of the outdoor second heat exchanger 21a reaches a certain thickness and defrosting is performed, the system needs to be switched to this state, and the specific operation mode is the same as described above. That is, the high-temperature and high-pressure refrigerant discharged by the compressor 10 enters the indoor heat exchanger 41 through the D and E pipes of the four-way valve for heat exchange, and then passes through the throttling device 31 for pressure reduction, and then passes through the outdoor third heat exchanger 21b and the outdoor first heat exchanger 21 in turn, and then enters the suction port of the compressor 10 through the C and S pipes of the four-way valve 51 after heat exchange is completed, and the cycle is completed after being compressed.

[0098] When it is detected that the tube wall temperature Twa of the outdoor second heat exchanger 21a is ≥10℃, defrosting is ended. Since the outdoor second heat exchanger 21a on the windward side is defrosted (electric heating), if the differential pressure meter detects that the pressure difference of the outdoor third heat exchanger 21b between the inlet and outlet air reaches a certain value, it indicates that the surface of the outdoor third heat exchanger 21b has frost and has reached a certain thickness, and defrosting needs to be performed. At this time, the first control valve 71 needs to be opened and the second control valve 72 needs to be closed, and the outdoor third heat exchanger 21b needs to be defrosted. In this way, the outdoor second and third heat exchangers are defrosted and defrosted in turn. In summary, the system fully utilizes the temperature glide characteristics of the non-azeotropic working fluid, sacrifices a small part of the area of the outdoor heat exchanger, and ensures that the main part of the heat exchanger does not frost. Through the switching of the valve, the outdoor heat exchanger is defrosted and defrosted in turn without stopping, thereby ensuring normal heating in the room. At the same time, the temperature glide characteristics of the non-azeotropic working fluid are fully utilized. Because the non-azeotropic working fluid gradually glides from the bubble point temperature to the dew point temperature during the heat exchange process in the evaporator, the temperature gradually increases, and the greater the glide temperature of the non-azeotropic working fluid, the more obvious this phenomenon. Therefore, in the cold and dry season in the north, the difference between the dry-bulb temperature and the dew point temperature of the outdoor air is relatively large at this time, and the system can fully play an advantage. Thus, in low-temperature working conditions, the outdoor first heat exchanger 21 will not frost, and frost will only occur on the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b. Then, through the switching of the valve, the heating operation, defrosting, and defrosting are performed at the same time, thereby improving the continuity, stability, and comfort of the heating environment of the system.

[0099] In some embodiments, in the control step, when the air conditioner operates in the heating mode, and when Tout≥T1 and Tin<T3 for a continuous t1 time, or when Tout<T1 and Tin<T2 for a continuous t1 time, the first control valve 71 is closed and the second control valve 72 is opened, and the first control valve 71 is closed and the second control valve 72 is opened for a duration of t2, where t2 is a second preset time.

[0100] ​The detecting step can also detect the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger 21b.

[0101] The judging step can also judge whether a second pressure difference between the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger 21b is greater than or equal to a second preset pressure difference value.

[0102] The controlling step can also control the first control valve 71 to open and the second control valve 72 to close when the second pressure difference is greater than or equal to the second preset pressure difference value, and maintain the first control valve 71 to close and the second control valve 72 to open when the second pressure difference is less than the second preset pressure difference value.

[0103] In some embodiments, the controlling step can also control the outdoor third heat exchanger 21b to defrost when the pressure difference is greater than or equal to the preset pressure difference value and the first control valve 71 is controlled to open and the second control valve 72 is controlled to close.

[0104] 2.3 Severe working condition heating

[0105] When the outdoor environment is very severe, the heating load demand is large, and the evaporation temperature is very low, the outdoor first heat exchanger 21 cannot be defrosted by the temperature glide of the two auxiliary heat exchangers (the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b), and the surface of the outdoor first heat exchanger 21 starts to frost, which seriously affects the heating performance. At this time, the four-way valve 31 is reversed (switched to the refrigeration mode), the indoor and outdoor fans are stopped, the first control valve 71 and the second control valve 72 are turned on, and the system circulation diagram is as shown in FIG. 8. Figure 1 When the defrosting and defrosting mode is operated for 8 minutes and the outdoor heat exchanger fin tube wall temperature Tw is greater than or equal to 10°C, the defrosting is ended. Then the system is operated in the heating mode again, as shown in FIG. 9. Figure 2

[0106] In some embodiments, T3 < T2 < T1; when the air conditioning system further comprises a four-way valve 51:

[0107] ​The control step can also control the first control valve 71 and the second control valve 72 to be opened, and control the four-way valve 51 to be reversed and switched to the refrigeration mode to defrost at least one of the outdoor first heat exchanger 21, the outdoor second heat exchanger 21a and the outdoor third heat exchanger 21b when the air conditioner is operated in the heating mode and Tout < T4 (indicating that the environment is very poor at this time, the heating load demand is large, the evaporation temperature is very low, the outdoor first heat exchanger 21 cannot be defrosted by the temperature glide of the two auxiliary heat exchangers, and the surface of the outdoor first heat exchanger 21 also starts to frost, which seriously affects the heating performance; T4 is preferably -15 to -20℃ below zero).

[0108] In some embodiments, when the air conditioning system further comprises a four-way valve, a third control valve, a fourth control valve, a fifth control valve and a sixth control valve:

[0109] The control step can also control the third control valve 73 and the sixth control valve 76 to be opened, and control the fourth control valve 74 and the fifth control valve 75 to be closed when the air conditioner is operated in the refrigeration mode, and control the third control valve 73 and the sixth control valve 76 to be closed, and control the fourth control valve 74 and the fifth control valve 75 to be opened when the air conditioner is operated in the heating mode.

[0110] Figure 5 Figure 6 Figure 7 Figure 8 The first alternative embodiment of the present application is different from the main embodiment in that two two-way valves are arranged at the inlet and outlet of the indoor heat exchanger 41, the third control valve 73 and the sixth control valve 76 are turned on, and the fourth control valve 74 and the fifth control valve 75 are closed during refrigeration operation; the fourth control valve 74 and the fifth control valve 75 are turned on, and the third control valve 73 and the sixth control valve 76 are closed during heating operation. By switching the valves, the temperature glide characteristics of the non-azeotropic working fluid can be fully utilized in refrigeration and heating conditions, so that the indoor heat exchanger 41 is always counter-flow heat exchange, the heat exchange temperature difference is reduced, the irreversible loss of the heat exchange process is reduced, and the heat exchange efficiency is improved. The other operation modes are the same as those of the main embodiment.

[0111] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. The above only describes the preferred embodiments of the present application, and it should be pointed out that, for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be regarded as the protection scope of the present application.​​​

Claims

1. An air conditioning system, characterized by: The air conditioning system comprises a compressor (10), an outdoor first heat exchanger (21), an outdoor second heat exchanger (21a), an outdoor third heat exchanger (21b), an indoor heat exchanger (41) and a throttling device (31), and the air conditioning system comprises a first boiling point refrigerant and a second boiling point refrigerant, the boiling point of the first boiling point refrigerant is lower than the boiling point of the second boiling point refrigerant, one end of the outdoor first heat exchanger (21) is capable of being communicated to the exhaust end or the suction end of the compressor (10), the other end is capable of being communicated to one end of the outdoor second heat exchanger (21a) and / or one end of the outdoor third heat exchanger (21b); the other end of the outdoor second heat exchanger (21a) is communicated to the other end of the outdoor third heat exchanger (21b), and then is capable of being communicated to one end of the throttling device (31), the other end of the throttling device (31) is communicated to one end of the indoor heat exchanger (41), and the other end of the indoor heat exchanger (41) is capable of being selectively communicated to the suction end or the exhaust end of the compressor (10); the outdoor second heat exchanger (21a) is located on a third pipeline (103), the outdoor third heat exchanger (21b) is located on a fourth pipeline (104), the third pipeline (103) is connected in parallel with the fourth pipeline (104), the other end of the third pipeline (103) is communicated to the other end of the fourth pipeline (104), and then is capable of being communicated to one end of the indoor heat exchanger (41), a first control valve (71) is arranged on the third pipeline (103), and a second control valve (72) is arranged on the fourth pipeline (104); a detection step of detecting the operation mode of the air conditioning system, the temperature Tout of the outdoor environment and the inlet temperature Tin of the outdoor second heat exchanger or the outdoor third heat exchanger in the heating mode; a judgment step of judging the relationship between Tout and a first preset value T1 and the relationship between Tin and a second preset value T2 and a third preset value T3; wherein T2>T3; a control step, when the air conditioner operates in the cooling mode: control the first control valve (71) and the second control valve (72) to be opened; when the air conditioner operates in the heating mode: and when Tout≥T1 and Tin≥T2, control the first control valve (71) and the second control valve (72) to be opened; and when Tout≥T1 and Tin is less than T3 within a continuous t1 time, or when Tout is less than T1 and Tin is less than T2 within a continuous t1 time, control one of the first control valve (71) and the second control valve (72) to be opened and the other to be closed, wherein t1 is a first preset time. ​ The control step controls the first control valve (71) to open and the second control valve (72) to close when the air conditioner operates in the heating mode and when Tout is greater than or equal to T1 and Tin is less than T3 for a continuous time t1 or when Tout is less than T1 and Tin is less than T2 for a continuous time t1, and the control lasts for a time t2, wherein t2 is a second preset time; and the detection step further detects the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger (21a). The judgment step further judges whether a first pressure difference between the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger (21a) is greater than or equal to a first preset pressure difference value. The control step further controls the first control valve (71) to close and the second control valve (72) to open when the first pressure difference is greater than or equal to the first preset pressure difference value, and controls the first control valve (71) to open and the second control valve (72) to close when the first pressure difference is less than the first preset pressure difference value; and the control step further controls the outdoor second heat exchanger (21a) to defrost when the first pressure difference is greater than or equal to the first preset pressure difference value and the first control valve (71) is controlled to close and the second control valve (72) is controlled to open; or the control step controls the first control valve (71) to close and the second control valve (72) to open when the air conditioner operates in the heating mode and when Tout is greater than or equal to T1 and Tin is less than T3 for a continuous time t1 or when Tout is less than T1 and Tin is less than T2 for a continuous time t1, and the control lasts for a time t2, wherein t2 is a second preset time; and the detection step further detects the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger (21b). The judgment step further judges whether a second pressure difference between the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger (21b) is greater than or equal to a second preset pressure difference value. The control step further controls the first control valve (71) to open and the second control valve (72) to close when the second pressure difference is greater than or equal to the second preset pressure difference value, and controls the first control valve (71) to close and the second control valve (72) to open when the second pressure difference is less than the second preset pressure difference value. The control step further controls the outdoor third heat exchanger (21b) to defrost when the second pressure difference is greater than or equal to the second preset pressure difference value and the first control valve (71) is controlled to open and the second control valve (72) is controlled to close.

2. The air conditioning system of claim 1, wherein: One end of the outdoor first heat exchanger (21) is selectively communicated to the exhaust end or the suction end of the compressor (10) through the first pipeline (101), and the other end is communicated to one end of the outdoor second heat exchanger (21a) and / or one end of the outdoor third heat exchanger (21b) through the second pipeline (102), and the outdoor second heat exchanger (21a) and the outdoor third heat exchanger (21b) are connected in parallel.

3. The air conditioning system of claim 2, wherein: One end of the third pipeline (103) is communicated to one end of the fourth pipeline (104) and then communicated to the second pipeline (102).

4. The air conditioning system of claim 3, wherein: Further comprising a fifth pipeline (105), a sixth pipeline (106) and a seventh pipeline (107), the third pipeline (103) and the fourth pipeline (104) are communicated to one end of the throttling device (31) through the fifth pipeline (105) after merging, the other end of the throttling device (31) is communicated to one end of the indoor heat exchanger (41) through the sixth pipeline (106), and the other end of the indoor heat exchanger (41) is communicated to the suction end or the exhaust end of the compressor (10) through the seventh pipeline (107).

5. The air conditioning system of claim 4, wherein: Further comprising a four-way valve (51), the four-way valve (51) comprises an E end (E), an S end (S), a C end (C) and a D end (D), the E end (E) is communicated to the seventh pipeline (107), the S end (S) is communicated to the suction end of the compressor (10), the C end (C) is communicated to the first pipeline (101), and the D end (D) is communicated to the exhaust end of the compressor (10), the first communication state of the four-way valve is that the E end (E) is communicated to the S end (S), and at the same time, the C end (C) is communicated to the D end (D), at this time, the indoor operation is in the refrigeration state, the second communication state of the four-way valve is that the E end (E) is communicated to the D end (D), and at the same time, the S end (S) is communicated to the C end (C), at this time, the indoor operation is in the heating state, and the four-way valve (51) can be switched between the first communication state and the second communication state.

6. The air conditioning system of claim 5, wherein: Further comprising a first fan (61), the first fan (61) can drive part of the outdoor airflow to flow through the outdoor first heat exchanger (21), part of the airflow to flow through the outdoor second heat exchanger (21a), and part of the airflow to flow through the outdoor third heat exchanger (21b); Further comprising a second fan (62), the second fan (62) can drive the indoor airflow to flow through the indoor heat exchanger (41).

7. The air conditioning system of claim 6, wherein: The sixth pipeline (106) is provided with a third control valve (73), the seventh pipeline (107) is provided with a sixth control valve (76), the air conditioning system further comprises an eighth pipeline (108) and a ninth pipeline (109), one end of the eighth pipeline (108) is communicated to the sixth pipeline (106) and located between the third control valve (73) and the throttling device (31), the other end is connected to the seventh pipeline (107) and located between the sixth control valve (76) and the indoor heat exchanger (41), one end of the ninth pipeline (109) is communicated to the sixth pipeline (106) and located between the indoor heat exchanger (41) and the third control valve (73), the other end is connected to the seventh pipeline (107) and located between the sixth control valve (76) and the four-way valve (51), the eighth pipeline (108) is provided with a fourth control valve (74), and the ninth pipeline (109) is provided with a fifth control valve (75); The seventh pipeline (107) is arranged relative to the sixth pipeline (106) close to the second fan (62), and the ninth pipeline (109) is arranged relative to the eighth pipeline (108) away from the second fan (62).

8. A control method of an air conditioning system according to any one of claims 1 to 7, characterized by: Comprise: The detection step detects the operation mode of the air conditioning system and the temperature Tout of the outdoor environment, and the inlet temperature Tin of the outdoor second heat exchanger or the outdoor third heat exchanger in the heating mode; The judgment step judges the relationship between Tout and the first preset value T1, and judges the relationship between Tin and the second preset value T2 and the third preset value T3; Wherein T2>T3; The control step, When the air conditioner operates in the cooling mode: control the first control valve (71) and the second control valve (72) to be opened; When the air conditioner operates in the heating mode: and when Tout≥T1 and Tin≥T2, control the first control valve (71) and the second control valve (72) to be opened; and when Tout≥T1 and Tin is less than T3 within t1 time, or when Tout is less than T1 and Tin is less than T2 within t1 time, control one of the first control valve (71) and the second control valve (72) to be opened, and the other to be closed, wherein t1 is a first preset time; In the control step, when the air conditioner operates in the heating mode, and when Tout≥T1 and Tin is less than T3 within t1 time, or when Tout is less than T1 and Tin is less than T2 within t1 time, control the first control valve (71) to be opened and the second control valve (72) to be closed, and after t2 time, t2 is a second preset time; The detection step can also detect the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger (21a); The judgment step can also judge whether the first pressure difference between the inlet air pressure and the outlet air pressure of the outdoor second heat exchanger (21a) is greater than or equal to a first preset pressure difference value; The control step can further control the first control valve (71) to close and the second control valve (72) to open when the first pressure difference is greater than or equal to the first preset pressure difference value; maintain the first control valve (71) to open and the second control valve (72) to close when the first pressure difference is less than the first preset pressure difference value; and control the outdoor second heat exchanger (21a) to defrost when the first pressure difference is greater than or equal to the first preset pressure difference value and the first control valve (71) is controlled to close and the second control valve (72) is controlled to open. The detection step can further detect the second pressure difference between the inlet air pressure and the outlet air pressure of the outdoor third heat exchanger (21b). The control step can further control the first control valve (71) to open and the second control valve (72) to close when the second pressure difference is greater than or equal to the second preset pressure difference value; and maintain the first control valve (71) to close and the second control valve (72) to open when the second pressure difference is less than the second preset pressure difference value. The control step can further control the outdoor third heat exchanger (21b) to defrost when the second pressure difference is greater than or equal to the second preset pressure difference value and the first control valve (71) is controlled to open and the second control valve (72) is controlled to close.

9. The control method according to claim 8, wherein: T3 < T2 < T1; and when the air conditioning system further comprises the four-way valve (51), the control step can further control the first control valve (71) and the second control valve (72) to open and the four-way valve (51) to reverse and switch to the cooling mode to defrost at least one of the outdoor first heat exchanger (21), the outdoor second heat exchanger (21a) and the outdoor third heat exchanger (21b) when the air conditioner operates in the heating mode and when Tout < T4, wherein T4 < T3.

10. The control method according to any one of claims 8-9, wherein: when the air conditioning system further comprises the four-way valve, the third control valve, the fourth control valve, the fifth control valve and the sixth control valve, the control step can further control the first control valve (71) and the second control valve (72) to open and the four-way valve (51) to reverse and switch to the cooling mode to defrost at least one of the outdoor first heat exchanger (21), the outdoor second heat exchanger (21a) and the outdoor third heat exchanger (21b) when the air conditioner operates in the heating mode and when Tout < T4, wherein T4 < T3. ​ ​ ​ The control step can further comprise: when the air conditioner operates in a cooling mode, controlling the third control valve (73) to open and the sixth control valve (76) to open, and controlling the fourth control valve (74) and the fifth control valve (75) to close; when the air conditioner operates in a heating mode, controlling the third control valve (73) and the sixth control valve (76) to close, and controlling the fourth control valve (74) and the fifth control valve (75) to open.

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