Air conditioning system and control method thereof

Abstract

The invention provides an air conditioning system and a control method thereof.The air conditioning system comprises an evaporator, a condenser, a throttling element and a compressor and further comprises a first liquid storage tank, a first pipeline, a second pipeline and a cooling branch capable of being controllably cut off and communicated, and the first pipeline is controllably cut off and communicated with the top of the first liquid storage tank; the cooling branch is provided with a first liquid storage tank so that a high-temperature refrigerant in the air conditioning system can be led into the first liquid storage tank, the bottom of the first liquid storage tank communicates with an outlet of the condenser through a second pipeline, and the cooling branch is provided with a heat exchange structure. And the refrigerant with the lower temperature in the air conditioning system flowing in the cooling branch can cool the refrigerant in the first liquid storage tank at the heat exchange structure. The refrigerating capacity or heat generated by the air conditioning system is used for changing the refrigerant circulation amount, so that it can be guaranteed that the refrigerant circulation amount in the air conditioning system is matched with the specific operation working condition of the air conditioning system, and the phenomenon that system liquid accumulation is caused by the too large refrigerant circulation amount, and consequently the air conditioning performance is low is avoided.

Description

Technical Field

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

[0002] The circulation volume of refrigerant in the air-conditioning system has a great influence on the performance and energy efficiency of the air-conditioning system. If the circulation volume of refrigerant is too small, the performance of the air-conditioning system will be reduced and the optimal effect will not be achieved. If the circulation volume of refrigerant is too high, the performance of the air-conditioning system will be reduced, and the cost will also be increased, causing the risk of liquid running to the compressor. Therefore, matching the appropriate amount of refrigerant in the system is very important for the efficient operation of the air-conditioning system.

[0003] In daily air-conditioning system, the refrigerant quantity matching work is mostly done manually by adding or reducing the refrigerant through a fluorine injection nozzle, which is time-consuming and labor-intensive. Summary of the invention

[0004] Therefore, the present invention provides an air-conditioning system and a control method thereof, which can solve the technical problems in the prior art that the air-conditioning system cannot change the amount of refrigerant in the system in real time, and there is a risk of reduced system performance due to too little refrigerant circulation or increased costs, reduced system performance and the risk of the compressor running with liquid due to too much refrigerant circulation.

[0005] In order to solve the above problems, the present invention provides an air-conditioning system, including an evaporator, a condenser, a throttling element and a compressor, wherein the throttling element is connected between the outlet of the condenser and the inlet of the evaporator, and the compressor is connected between the inlet of the condenser and the outlet of the evaporator. The air-conditioning system also includes a first liquid storage tank, a first pipeline, a second pipeline and a cooling branch that can be controllably cut off. The first pipeline is controllably cut off from the top of the first liquid storage tank so that the higher temperature refrigerant in the air-conditioning system can be introduced into the first liquid storage tank. The bottom of the first liquid storage tank is connected to the outlet of the condenser through the second pipeline. The cooling branch has a heat exchange structure. The lower temperature refrigerant in the air-conditioning system flowing in the cooling branch can cool the refrigerant in the first liquid storage tank at the heat exchange structure.

[0006] In some embodiments, one end of the cooling branch is communicated with the inlet of the evaporator, and the other end is communicated with the outlet of the evaporator.

[0007] In some embodiments, a first electromagnetic on-off valve and / or a first capillary tube is connected in series to the cooling branch; and / or a second electromagnetic on-off valve and / or a second capillary tube is connected in series to the first pipeline.

[0008] In some embodiments, a second liquid storage tank and a fluorine pump are further provided between the throttling element and the outlet of the condenser, the liquid inlet of the fluorine pump is connected to the liquid outlet of the second liquid storage tank, the air-conditioning system further comprises a third pipeline and a fourth pipeline, wherein one end of the third pipeline is connected to the liquid inlet of the fluorine pump, and the other end is connected to the liquid outlet of the fluorine pump, and the liquid outlet of the fluorine pump is connected to the liquid inlet of the throttling element, a first one-way valve is connected in series to the third pipeline, and the one-way conduction direction of the first one-way valve is from the liquid inlet side of the fluorine pump to the liquid inlet side of the throttling element, the fourth pipeline is connected between the air intake and the exhaust port of the compressor, and a second one-way valve is connected in series to the fourth pipeline, and the one-way conduction direction of the second one-way valve is from the air intake side of the compressor to the exhaust port side of the compressor.

[0009] In some embodiments, the air-conditioning system also includes an oil separator, which is located between the exhaust port of the compressor and the inlet of the condenser, and the inlet of the first pipeline is connected between the air outlet of the oil separator and the inlet of the condenser, and the oil outlet pipe of the oil separator is connected to the outlet pipe section of the cooling branch via a second capillary tube.

[0010] In some embodiments, a liquid level sensor is provided in the first liquid storage tank for detecting the real-time liquid level height of the refrigerant in the first liquid storage tank; and / or, a temperature sensor is provided in the first liquid storage tank for detecting the real-time temperature of the refrigerant in the first liquid storage tank.

[0011] The present invention also provides a control method for the air conditioning system as described above, comprising the following steps:

[0012] Acquire the operating condition of the air conditioning system, and acquire the optimal refrigerant filling amount m1 in the system cycle corresponding to the operating condition according to the operating condition;

[0013] Calculate and obtain the target storage volume m2 of the refrigerant in the first liquid storage tank, where m2=m0-m1, and m0 is the total refrigerant filling volume in the air-conditioning system;

[0014] The first electromagnetic on-off valve or the second electromagnetic on-off valve is controlled to be on and off so that the real-time refrigerant storage amount m in the first liquid storage tank is m2, and when the real-time refrigerant storage amount m is m2, the first electromagnetic on-off valve and the second electromagnetic on-off valve are both controlled to be in the cut-off state.

[0015] In some embodiments, when m<m2, the first electromagnetic on-off valve is controlled to be in an on state and the second electromagnetic on-off valve is controlled to be in an off state.

[0016] In some embodiments, when m>m2, the second electromagnetic on-off valve is controlled to be in an on state and the first electromagnetic on-off valve is controlled to be in an off state.

[0017] In some embodiments, the real-time refrigerant storage amount m is obtained by:

[0018] Obtaining the real-time temperature and real-time liquid level h of the liquid refrigerant in the first liquid storage tank, and obtaining the liquid refrigerant density ρ corresponding to the saturated pressure and the real-time temperature according to the refrigerant parameters pre-stored in the controller;

[0019] The real-time refrigerant storage amount m is obtained according to the formula m=ρSh, where S is the cross-sectional area of ​​the storage space of the first liquid storage tank.

[0020] The air conditioning system and control method thereof provided by the present invention have the following beneficial effects:

[0021] The refrigerant with a higher temperature is introduced into the first liquid storage tank through the first pipeline, so that the refrigerant in the tank can be heated to increase the temperature of the refrigerant in the tank and the pressure in the tank. The refrigerant in the tank enters the air-conditioning system through the second pipeline to participate in the circulation, thereby achieving the purpose of increasing the refrigerant circulation volume. The refrigerant with a lower temperature is guided to the heat exchange structure through the cooling branch and the refrigerant in the first liquid storage tank is cooled at the heat exchange structure, so that the temperature of the refrigerant in the tank is reduced and the pressure in the tank is reduced. The refrigerant in the air-conditioning system enters the first liquid storage tank through the second pipeline, thereby achieving the purpose of reducing the refrigerant circulation volume. That is, the technical solution of the present invention uses the cold or heat generated by the air-conditioning system itself to change the refrigerant circulation volume, so as to ensure that the refrigerant circulation volume in the air-conditioning system matches the specific operating conditions of the air-conditioning system, prevents the phenomenon that the refrigerant circulation volume is too large, resulting in liquid accumulation in the system and then lowering the air-conditioning performance, and reduces the cost of using the air-conditioning, and also prevents the phenomenon that the refrigerant circulation volume is too small, resulting in lower air-conditioning performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. The drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0023] Figure 1 is a schematic diagram of the principle of an air conditioning system according to an embodiment of the present invention;

[0024] Figure 2 It is a schematic diagram of the principle of an air conditioning system according to another embodiment of the present invention.

[0025] The accompanying drawings are marked as follows:

[0026] 11. Evaporator; 111. Internal fan; 12. Condenser; 121. External fan; 13. Throttling element; 14. Compressor; 15. First liquid storage tank; 151. Liquid level sensor; 152. Temperature sensor; 16. Second liquid storage tank; 17. Fluorine pump; 18. Oil separator; 181. Second capillary tube;

[0027] 101, first pipeline; 1011, second electromagnetic on-off valve; 1012, second capillary tube; 102, second pipeline;

[0028] 103, cooling branch; 1031, heat exchange structure; 1032, first electromagnetic on-off valve; 1033, first capillary tube;

[0029] 104, third pipeline; 1041, first one-way valve;

[0030] 105. Fourth pipeline; 1051. Second one-way valve. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0033] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90° or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0034] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0035] The amount of refrigerant circulating in the air-conditioning system has a great influence on its performance and operation. Too much refrigerant circulating will cause the compressor to be overloaded, thus affecting its normal operation and even reaching an overload state. Overload will cause the motor current to be too large, and the air conditioner will have problems such as noise and vibration, and even burn the compressor in severe cases. At the same time, excessive refrigerant will cause the refrigerant to be unable to completely evaporate in the evaporator, thereby affecting the refrigeration effect, causing the refrigeration effect of the air conditioner to decrease. Too little refrigerant circulating will cause the suction gas of the compressor to overheat, thereby affecting the normal operation of the compressor, or even failure, and will also cause insufficient refrigeration capacity. The technical solution of the present invention can well overcome the deficiencies in the aforementioned prior art.

[0036] See also Figure 1 and Figure 2As shown, according to an embodiment of the present invention, an air conditioning system is provided, comprising an evaporator 11, a condenser 12, a throttling element 13 (e.g., an electronic expansion valve) and a compressor 14, wherein the throttling element 13 is connected between the outlet of the condenser 12 and the inlet of the evaporator 11, and the compressor 14 is connected between the inlet of the condenser 12 and the outlet of the evaporator 11, thereby forming a refrigeration cycle, the air conditioning system also comprises a first liquid storage tank 15, a first pipeline 101, a second pipeline 102 and a cooling branch 103 that can be controllably connected, the first pipeline 101 and the top of the first liquid storage tank 15 can be controllably disconnected to enable the higher temperature refrigerant in the air conditioning system to be introduced into the first liquid storage tank 15, and the bottom of the first liquid storage tank 15 is connected to the first liquid storage tank 15. The cooling branch 103 is connected to the outlet of the condenser 12 through the second pipeline 102 (generally speaking, during operation, the port of the second pipeline 102 should be below the liquid level of the liquid refrigerant in the first liquid storage tank 15), and the cooling branch 103 has a heat exchange structure 1031 (such as a heat exchange tube, etc.). The lower temperature refrigerant in the air-conditioning system flowing in the cooling branch 103 can cool the refrigerant in the first liquid storage tank 15 at the heat exchange structure 1031. It can be understood that the aforementioned higher temperature refers to the temperature of the refrigerant introduced into the first liquid storage tank 15 being higher than the temperature of the refrigerant in the first liquid storage tank 15, and the lower temperature refers to the temperature of the refrigerant introduced into the heat exchange structure 1031 being lower than the temperature of the refrigerant in the first liquid storage tank 15.

[0037] In this technical solution, a refrigerant with a higher temperature is introduced into the first liquid storage tank 15 through the first pipeline 101, so that the refrigerant in the tank can be heated to increase the temperature of the refrigerant in the tank and the pressure in the tank. The refrigerant in the tank enters the air-conditioning system through the second pipeline 102 to participate in the circulation, thereby achieving the purpose of increasing the refrigerant circulation amount. The refrigerant with a lower temperature is guided to the heat exchange structure 1031 through the cooling branch 103 and the refrigerant in the first liquid storage tank 15 is cooled at the heat exchange structure 1031, so that the temperature of the refrigerant in the tank is reduced and the pressure in the tank is reduced. The refrigerant in the air-conditioning system enters the first liquid storage tank 15 through the second pipeline 102, thereby achieving the purpose of reducing the refrigerant circulation amount. That is, the technical solution of the present invention uses the cold or heat generated by the air-conditioning system itself to change the refrigerant circulation amount, so as to ensure that the refrigerant circulation amount in the air-conditioning system matches the specific operating conditions of the air-conditioning system, prevent the phenomenon that the refrigerant circulation amount is too large, resulting in liquid accumulation in the system and thus causing lower air-conditioning performance, and reduce the cost of using the air-conditioning, and also prevent the phenomenon that the refrigerant circulation amount is too small, resulting in lower air-conditioning performance.

[0038] As mentioned above, due to the technical solution of the present invention, the refrigerant circulation volume can be at a reasonable level that matches the current working conditions, so that the refrigerant circulation volume of the air-conditioning system of the present invention will not be too much, thus avoiding the aforementioned problems caused by excessive compressor load and the problem of reduced refrigeration effect due to excessive refrigerant circulation volume; it also ensures that the refrigerant circulation volume of the air-conditioning system of the present invention will not be too little, thereby preventing the compressor suction overheating affecting the normal operation of the compressor and the problem of insufficient system refrigeration capacity.

[0039] In a specific embodiment, one end of the cooling branch 103 is connected to the inlet of the evaporator 11, and the other end is connected to the outlet of the evaporator 11. During the specific operation, when the cooling branch 103 is controlled to be turned on, the refrigerant with a lower temperature at the inlet of the evaporator 11 will be guided to the heat exchange structure 1031 to exchange heat with the refrigerant in the first liquid storage tank 15 and then flow back to the intake port of the compressor 14 after heating. The system design is reasonable and simple, and no corresponding cooling source needs to be configured externally, thereby reducing the use cost of the air-conditioning system.

[0040] In some embodiments, a first electromagnetic on-off valve 1032 and / or a first capillary 1033 are connected in series to the cooling branch 103, and the on-off control of the first electromagnetic on-off valve 1032 is used to realize the on-off of the cooling branch 103. Specifically, when it is necessary to migrate and store excess refrigerant in the system cycle in the first liquid storage tank 15, the first electromagnetic on-off valve 1032 is controlled to be turned on.

[0041] In some embodiments, a second electromagnetic on-off valve 1011 and / or a second capillary tube 1012 is connected in series to the first pipeline 101, and the on-off control of the second electromagnetic on-off valve 1011 is used to realize the on-off of the first pipeline 101. Specifically, when it is necessary to add refrigerant to the system circulation, the second electromagnetic on-off valve 1011 is controlled to be turned on.

[0042] In some embodiments, a second liquid storage tank 16 and a fluorine pump 17 are further provided between the throttling element 13 and the outlet of the condenser 12, and the liquid inlet of the fluorine pump 17 is connected to the liquid outlet of the second liquid storage tank 16, and the air conditioning system further includes a third pipeline 104 and a fourth pipeline 105, wherein one end of the third pipeline 104 is connected to the liquid inlet of the fluorine pump 17, and the other end is connected to the liquid outlet of the fluorine pump 17, and the liquid outlet of the fluorine pump 17 is connected to the liquid inlet of the throttling element 13, and a first one-way valve 1041 is connected in series to the third pipeline 104, and the one-way conduction direction of the first one-way valve 1041 is from the inlet of the fluorine pump 17 to the outlet of the fluorine pump 17. From the liquid port side to the liquid inlet side of the throttling element 13, it can be understood that when the fluorine pump 17 is running, the first one-way valve 1041 will cut off the circulation of the refrigerant through the third pipeline 104 under the action of the reverse pressure difference, and the fourth pipeline 105 is connected between the suction port and the exhaust port of the compressor 14, and a second one-way valve 1051 is connected in series to the fourth pipeline 105, and the one-way conduction direction of the second one-way valve 1051 is from the suction port side of the compressor 14 to the exhaust port side of the compressor 14. When the compressor 14 is running, the second one-way valve 1051 will cut off the circulation of the refrigerant through the fourth pipeline 105 under the action of the reverse pressure difference.

[0043] In this technical solution, the air-conditioning system is objectively a fluorine pump compression refrigeration system, which has a compression refrigeration mode and a fluorine pump refrigeration mode. In winter when the external environment is relatively low, the fluorine pump refrigeration mode can be used to cool and dissipate heat on the indoor side (such as the machine room), which is energy-saving and environmentally friendly, while the compression refrigeration mode can be operated in other situations.

[0044] In some embodiments, the air-conditioning system further includes an oil separator 18, wherein the oil separator 18 is located between the exhaust port of the compressor 14 and the inlet of the condenser 12, and the inlet of the first pipeline 101 is connected between the air outlet of the oil separator 18 and the inlet of the condenser 12, and the oil outlet pipe of the oil separator 18 is connected to the outlet pipe section of the cooling branch 103 via a second capillary 181. In this technical solution, by providing the oil separator 18, the lubricating oil in the exhaust airflow of the compressor 14 can be separated and then refluxed into the compressor 14, thereby ensuring sufficient lubrication of various components in the compressor 14, and at the same time preventing the lubricating oil from being retained in the heat exchanger in the system circulation, resulting in reduced heat exchange efficiency and reduced heat exchange effect.

[0045] In some embodiments, a liquid level sensor 151 is provided in the first liquid storage tank 15 for detecting the real-time liquid level height of the refrigerant in the first liquid storage tank 15 ; and / or, a temperature sensor 152 is provided in the first liquid storage tank 15 for detecting the real-time temperature of the refrigerant in the first liquid storage tank 15 .

[0046] According to an embodiment of the present invention, there is also provided a control method for the air conditioning system as described above, comprising the following steps:

[0047] Obtaining the operating condition of the air-conditioning system, and obtaining the optimal refrigerant filling amount m1 in the system cycle corresponding to the operating condition (that is, the refrigerant circulation amount in the system) according to the operating condition. Specifically, the optimal refrigerant filling amount corresponding to the aforementioned operating condition can be obtained by monitoring the operating parameters of the air-conditioning system, including the operating frequency of the compressor, the high pressure value, the low pressure value, the exhaust superheat, the suction superheat, the oil temperature, and the expansion valve opening, and pre-storing the optimal refrigerant filling amount corresponding to each operating condition in the corresponding controller;

[0048] Calculate and obtain the target storage volume m2 of the refrigerant in the first liquid storage tank 15, where m2=m0-m1, and m0 is the total refrigerant filling volume in the air conditioning system;

[0049] The first electromagnetic on-off valve 1032 or the second electromagnetic on-off valve 1011 is controlled to be on and off so that the real-time refrigerant storage amount m in the first liquid storage tank 15 is m2, and when the real-time refrigerant storage amount m is m2, the first electromagnetic on-off valve 1032 and the second electromagnetic on-off valve 1011 are controlled to be in the cut-off state.

[0050] Specifically, when m<m2, the first electromagnetic on-off valve 1032 is controlled to be in the on state and the second electromagnetic on-off valve 1011 is in the off state; when m>m2, the second electromagnetic on-off valve 1011 is controlled to be in the on state and the first electromagnetic on-off valve 1032 is in the off state. It can be understood that when m=m2, the first electromagnetic on-off valve 1032 and the second electromagnetic on-off valve 1011 are kept in the off state without increasing or decreasing the circulation amount of the refrigerant.

[0051] In some embodiments, the real-time refrigerant storage amount m is obtained by:

[0052] Obtain the real-time temperature and real-time liquid level h of the liquid refrigerant in the first liquid storage tank 15, and obtain the liquid refrigerant density ρ corresponding to the saturated pressure and the real-time temperature according to the refrigerant parameters pre-stored in the controller;

[0053] The real-time refrigerant storage volume m is obtained according to the formula m=ρSh, where S is the cross-sectional area of ​​the storage space of the first liquid storage tank 15, and the aforementioned physical parameters are all in international units. In a specific embodiment, the first liquid storage tank 15 is a cylinder with equal upper and lower diameters, that is, each cross-sectional area S is equal, which can further simplify the acquisition of m.

[0054] The following combination Figure 1The technical solution of the present invention is further described:

[0055] 1) When the air conditioning system needs to increase the refrigerant circulation volume

[0056] When the air-conditioning system needs to increase the refrigerant circulation volume, the refrigerant should flow from the first liquid storage tank 15 to the system (that is, the system circulation). At this time, the pressure in the first liquid storage tank 15 should be greater than the pressure after the system is throttled, that is, the second electromagnetic on-off valve 1011 should be opened to allow a part of the exhaust gas to enter the first liquid storage tank 15 through the first pipeline 101, thereby increasing the pressure in the first liquid storage tank 15. At this time, the refrigerant in the tank will enter the air-conditioning system circulation through the second pipeline 102 under the pressure of the exhaust gas. When the refrigerant mass (liquid refrigerant mass) in the first liquid storage tank 15 reaches m2, the second electromagnetic on-off valve 1011 is closed. During this process, the first electromagnetic on-off valve 1032 is in a cut-off state.

[0057] 2) When the air conditioning system needs to reduce the amount of refrigerant circulation

[0058] When the air-conditioning system needs to reduce the amount of refrigerant circulation, the refrigerant should flow from the system (that is, the system circulation) to the first liquid storage tank 15. At this time, the pressure in the first liquid storage tank 15 should be lower than the pressure after the system is throttled, that is, the first electromagnetic on-off valve 1032 should be opened to allow a portion of the throttled refrigerant to enter the first liquid storage tank 15 through the cooling branch 103, and heat exchange is performed using the heat exchange structure 1031. At this time, the density of the liquid refrigerant in the tank increases after cooling, the volume decreases, and the pressure decreases. The refrigerant in the air-conditioning system can enter the first liquid storage tank 15 through the second pipeline 102. When the refrigerant mass (liquid refrigerant mass) in the first liquid storage tank 15 reaches m2, the first electromagnetic on-off valve 1032 is closed. During this process, the second electromagnetic on-off valve 1011 is in a cut-off state.

[0059] It is easy for those skilled in the art to understand that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0060] 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 principle of the present invention shall be included in the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present invention. These improvements and variations should also be regarded as the protection scope of the present invention.

Claims

1. An air conditioning system, comprising an evaporator (11), a condenser (12), a throttling element (13) and a compressor (14), wherein the throttling element (13) is connected between the outlet of the condenser (12) and the inlet of the evaporator (11), and the compressor (14) is connected between the inlet of the condenser (12) and the outlet of the evaporator (11), characterized in that: The system further comprises a first liquid storage tank (15), a first pipeline (101), a second pipeline (102) and a cooling branch (103) which can be controllably disconnected from the connection. The first pipeline (101) can be controllably disconnected from the top of the first liquid storage tank (15) so as to be able to introduce a refrigerant with a higher temperature in the air-conditioning system into the first liquid storage tank (15). The bottom of the first liquid storage tank (15) is connected to the outlet of the condenser (12) through the second pipeline (102). The cooling branch (103) has a heat exchange structure (1031). The refrigerant with a lower temperature in the air-conditioning system flowing in the cooling branch (103) can cool the refrigerant in the first liquid storage tank (15) at the heat exchange structure (1031).

2. The air conditioning system according to claim 1, characterized in that: One end of the cooling branch (103) is in communication with the inlet of the evaporator (11), and the other end is in communication with the outlet of the evaporator (11).

3. The air conditioning system according to claim 2, characterized in that: The cooling branch (103) is connected in series with a first electromagnetic on-off valve (1032) and / or a first capillary tube (1033); and / or the first pipeline (101) is connected in series with a second electromagnetic on-off valve (1011) and / or a second capillary tube (1012).

4. The air conditioning system according to any one of claims 1 to 3, characterized in that: A second liquid storage tank (16) and a fluorine pump (17) are also provided between the throttling element (13) and the outlet of the condenser (12); the liquid inlet of the fluorine pump (17) is connected to the liquid outlet of the second liquid storage tank (16); the air conditioning system further comprises a third pipeline (104) and a fourth pipeline (105); one end of the third pipeline (104) is connected to the liquid inlet of the fluorine pump (17) and the other end is connected to the liquid outlet of the fluorine pump (17); the liquid outlet of the fluorine pump (17) is connected to the liquid inlet of the throttling element (13); A first one-way valve (1041) is connected in series to the pipeline (104), and the one-way conduction direction of the first one-way valve (1041) is from the liquid inlet side of the fluorine pump (17) to the liquid inlet side of the throttling element (13). The fourth pipeline (105) is connected between the air intake port and the air outlet port of the compressor (14), and a second one-way valve (1051) is connected in series to the fourth pipeline (105), and the one-way conduction direction of the second one-way valve (1051) is from the air intake port side of the compressor (14) to the air outlet side of the compressor (14).

5. The air conditioning system according to claim 4, characterized in that: It also includes an oil separator (18), which is located between the exhaust port of the compressor (14) and the inlet of the condenser (12), and the inlet of the first pipeline (101) is connected between the air outlet of the oil separator (18) and the inlet of the condenser (12), and the oil outlet pipe of the oil separator (18) is connected to the outlet pipe section of the cooling branch (103) via a second capillary tube (181).

6. The air conditioning system according to claim 1, characterized in that: The first liquid storage tank (15) is provided with a liquid level sensor (151) for detecting the real-time liquid level height of the refrigerant in the first liquid storage tank (15); and / or the first liquid storage tank (15) is provided with a temperature sensor (152) for detecting the real-time temperature of the refrigerant in the first liquid storage tank (15).

7. A control method for an air conditioning system as claimed in claim 5, characterized in that: The steps include: Acquire the operating condition of the air conditioning system, and acquire the optimal refrigerant filling amount m1 in the system cycle corresponding to the operating condition according to the operating condition; Calculate and obtain the target storage volume m2 of the refrigerant in the first liquid storage tank (15), where m2=m0-m1, and m0 is the total filling volume of the refrigerant in the air-conditioning system; The first electromagnetic on-off valve (1032) or the second electromagnetic on-off valve (1011) is controlled to be on and off so that the real-time refrigerant storage amount m in the first liquid storage tank (15) is m2, and when the real-time refrigerant storage amount m is m2, the first electromagnetic on-off valve (1032) and the second electromagnetic on-off valve (1011) are controlled to be in a cut-off state.

8. The control method of the air conditioning system according to claim 7, characterized in that: When m<m2, the first electromagnetic on-off valve (1032) is controlled to be in an on state and the second electromagnetic on-off valve (1011) is controlled to be in an off state.

9. The control method of the air conditioning system according to claim 7, characterized in that: When m>m2, the second electromagnetic on-off valve (1011) is controlled to be in an on state and the first electromagnetic on-off valve (1032) is controlled to be in an off state.

10. The control method of the air conditioning system according to claim 7, characterized in that: The real-time refrigerant storage amount m is obtained by: Acquiring the real-time temperature and the real-time liquid level h of the liquid refrigerant in the first liquid storage tank (15), and obtaining the liquid refrigerant density ρ corresponding to the saturated pressure and the real-time temperature according to the refrigerant parameters pre-stored in the controller; The real-time refrigerant storage amount m is obtained according to the formula m=ρSh, where S is the cross-sectional area of ​​the storage space of the first liquid storage tank (15).

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