Methods for controlling the liquid level in condensing units and gas-liquid separators

Abstract

This application relates to a condensing unit and a method for controlling the liquid level in a gas-liquid separator. The condensing unit includes a compressor, a condenser, a liquid receiver, a gas-liquid separator, a four-way valve, and a controller. The condenser, liquid receiver, gas-liquid separator, and compressor are connected sequentially. The four-way valve includes a first port, a second port, a third port, and a fourth port. The first port is connected to the compressor, the second port is connected to the condenser, the third port is connected to the gas-liquid separator, and the fourth port is used to connect to the evaporator. A pump body is connected between the liquid receiver and the gas-liquid separator. A liquid level sensing unit is provided inside the gas-liquid separator. The compressor, condenser, liquid receiver, gas-liquid separator, liquid level sensing unit, and pump body are all electrically connected to the controller. According to the condensing unit of the present invention, excess liquid can be drawn from the gas-liquid separator and transported to the liquid receiver by the pump body, thereby preventing liquid from being carried in by the compressor during suction and avoiding liquid slugging.

Description

Technical Field

[0001] This application relates to the field of condensing unit technology, and in particular to a condensing unit and a method for controlling the liquid level of a gas-liquid separator. Background Technology

[0002] In the refrigeration and freezing industry, refrigeration units are widely used. The principle of a refrigeration unit is that the compressor compresses low-pressure vapor into high-pressure vapor, reducing the vapor's volume and increasing its pressure. A condensing unit typically consists of one or more electric motors driving a positive displacement refrigeration compressor, a condenser, and other necessary auxiliary equipment. During operation, due to factors such as low superheat in the refrigeration system, the compressor may experience liquid carryover during startup, posing a risk of liquid slugging, which can shorten the compressor's lifespan and reduce the unit's operational reliability. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a condensing unit that can prevent liquid from being carried in by the compressor during suction, avoid liquid slugging, extend the compressor's lifespan, and improve the reliability of the condensing unit during operation.

[0004] The present invention also proposes a method for controlling the liquid level of a gas-liquid separator, for controlling the aforementioned condenser unit.

[0005] The condensing unit according to the present invention includes a compressor, a condenser, a liquid receiver, a gas-liquid separator, a four-way valve, and a controller. The condenser, liquid receiver, gas-liquid separator, and compressor are connected in sequence. The four-way valve includes a first port, a second port, a third port, and a fourth port. The first port is connected to the compressor, the second port is connected to the condenser, the third port is connected to the gas-liquid separator, and the fourth port is used to connect to the evaporator. A pump body is connected between the liquid receiver and the gas-liquid separator. A liquid level sensing unit is provided inside the gas-liquid separator. The compressor, condenser, liquid receiver, gas-liquid separator, liquid level sensing unit, and pump body are all electrically connected to the controller.

[0006] According to the condensing unit of the present invention, when the liquid level in the gas-liquid separator exceeds the allowable height, the excess liquid can be pumped out from the gas-liquid separator and transported to the liquid receiver by the pump body, thereby preventing the compressor from carrying liquid during suction, avoiding liquid slugging, extending the compressor's life, and improving the reliability of the condensing unit during operation.

[0007] According to the condenser unit of the present invention, the gas-liquid separator is provided with a first outlet and a second outlet spaced apart, the second outlet being located below the first outlet, the first outlet being connected to the compressor, and the second outlet being connected to the inlet of the liquid receiver.

[0008] Optionally, the distance L between the second outlet and the bottom of the gas-liquid separator and the height H of the gas-liquid separator satisfy the following condition: 1 / 8H≤L≤1 / 3H.

[0009] Optionally, the outlet of the liquid receiver is sequentially connected to a dryer filter, a throttle valve, and a liquid supply shut-off valve, and / or a first temperature sensor and a first pressure sensor are provided on the pipeline connecting the compressor and the four-way valve, and a second temperature sensor and a second pressure sensor are provided on the pipeline connecting the compressor and the gas-liquid separator. The first temperature sensor, the first pressure sensor, the second temperature sensor, and the second pressure sensor are all electrically connected to the controller.

[0010] The method for controlling the liquid level in a gas-liquid separator according to the present invention, used for controlling the aforementioned condensing unit, includes:

[0011] Real-time acquisition of the operating liquid level of the gas-liquid separator;

[0012] The pump body is turned on or off based on the operating liquid level.

[0013] According to the method for controlling the liquid level of a gas-liquid separator of the present invention, when the liquid level in the gas-liquid separator exceeds the allowable height, the excess liquid can be pumped out from the gas-liquid separator and transported to the liquid reservoir by the pump body, thereby preventing the compressor from carrying liquid during suction, avoiding liquid slugging, extending the life of the compressor, and improving the reliability of the condenser unit during operation. When the liquid level in the gas of the gas-liquid separator meets the requirements, the pump body is controlled to shut down and stop operation.

[0014] Optionally, the pump body can be turned on or off based on the operating liquid level, specifically including:

[0015] The real-time liquid level deviation of the gas-liquid separator is determined based on the difference between the operating liquid level and the initial liquid level of the gas-liquid separator.

[0016] When the real-time liquid level deviation is greater than or equal to the preset liquid level deviation, the compressor's suction temperature, discharge temperature, evaporation pressure, and condensation pressure are obtained.

[0017] The evaporation and condensation temperatures of the compressor are determined based on the evaporation and condensation pressures.

[0018] The real-time liquid level deviation of the gas-liquid separator is determined based on the difference between the operating liquid level and the initial liquid level of the gas-liquid separator, according to the intake temperature, evaporation temperature, exhaust temperature, and condensation temperature.

[0019] When the real-time liquid level deviation is greater than or equal to the preset liquid level deviation, the compressor's suction temperature, discharge temperature, evaporation pressure, and condensation pressure are obtained.

[0020] The evaporation and condensation temperatures of the compressor are determined based on the evaporation and condensation pressures.

[0021] The pump is turned on based on the intake temperature, evaporation temperature, exhaust temperature, and condensation temperature.

[0022] Optionally, the pump body can be controlled to start based on the suction temperature, evaporation temperature, exhaust temperature, and condensation temperature, specifically including:

[0023] The compressor's intake superheat and exhaust superheat are determined based on the intake temperature, evaporation temperature, exhaust temperature, and condensation temperature.

[0024] The difference between the intake superheat and the first preset superheat is taken as the intake superheat deviation, and the difference between the exhaust superheat and the second preset superheat is taken as the exhaust superheat deviation.

[0025] The pump body is activated based on the deviations in intake superheat and exhaust superheat.

[0026] Optionally, the pump body can be controlled to start based on the intake superheat deviation and the exhaust superheat deviation, specifically including:

[0027] When the intake superheat deviation is less than or equal to the preset deviation value and the exhaust superheat deviation is greater than the preset deviation value, the pump body is controlled to start and operate at the first power.

[0028] When the intake superheat deviation is less than or equal to the preset deviation value and the exhaust superheat deviation is less than or equal to the preset deviation value, the pump body is controlled to start and operate at the second power, which is greater than the first power.

[0029] When the intake superheat deviation is greater than the preset deviation value and the exhaust superheat deviation is less than or equal to the preset deviation value, the pump body is controlled to start and operate at the third power, which is less than the second power.

[0030] Optionally, the third power is equal to the first power, and the third power is greater than the rated power of the pump body.

[0031] Optionally, the method for controlling the liquid level in the gas-liquid separator further includes:

[0032] During pump operation, real-time liquid level deviation is acquired;

[0033] When the real-time liquid level deviation is less than the preset liquid level deviation within a preset time, the control pump body is shut down. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a condensing unit according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic flowchart of a method for controlling the liquid level in a gas-liquid separator according to some embodiments of the present invention.

[0038] Figure 3 This is a schematic flowchart of a method for controlling the liquid level in a gas-liquid separator according to some embodiments of the present invention.

[0039] Figure 4 This is a schematic flowchart of a method for controlling the liquid level of a gas-liquid separator according to some embodiments of the present invention.

[0040] Figure label:

[0041] Compressor 1, condenser 2, liquid receiver 3, dryer filter 4, throttle valve 5, liquid supply shut-off valve 6, suction shut-off valve 7, gas-liquid separator 8, first outlet 81, second outlet 82, second pressure sensor 9, second temperature sensor 10, first temperature sensor 11, first pressure sensor 12, four-way valve 13, first port D, second port C, third port S, fourth port E, pump body 14, suction filter 16. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] The condensing unit according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0044] like Figure 1As shown, the condensing unit according to an embodiment of the present invention includes a compressor 1, a condenser 2, a liquid receiver 3, a gas-liquid separator 8, a four-way valve 13, and a controller. The condenser 2, the liquid receiver 3, the gas-liquid separator 8, and the compressor 1 are connected in sequence. The four-way valve 13 includes a first port D, a second port C, a third port S, and a fourth port E. The first port D is connected to the compressor 1, the second port C is connected to the condenser 2, the third port S is connected to the gas-liquid separator 8, and the fourth port E is used to connect to the evaporator. A pump body 14 is connected between the liquid receiver 3 and the gas-liquid separator 8. A liquid level sensing unit is provided inside the gas-liquid separator 8. The compressor 1, the condenser 2, the liquid receiver 3, the gas-liquid separator 8, the four-way valve 13, the liquid level sensing unit, and the pump body 14 are all electrically connected to the controller.

[0045] In detail, the suction port of compressor 1 is connected to the outlet of gas-liquid separator 8, the discharge port of compressor 1 is connected to the first port D, and the inlet of gas-liquid separator 8 is connected to the third port S. During refrigeration, the refrigerant is discharged from the discharge port of compressor 1, enters the four-way valve 13 through the first port D, and then enters the condenser 2 through the second port C for condensation. After liquefaction, the refrigerant flows into the liquid receiver 3, where part is stored and the other part enters the evaporator after passing through the expansion valve 5. After that, it flows back to the fourth port E through the evaporator and enters the four-way valve 13, and then enters the gas-liquid separator 8 through the third port S. In the gas-liquid separator 8, the gas-liquid separator 8 separates the gaseous refrigerant and the liquid refrigerant. The liquid refrigerant accumulates at the bottom of the gas-liquid separator 8 and then enters the compressor 1 through the suction port of the compressor 1, thus starting the next cycle. A pump body 14 is provided between the liquid receiver 3 and the gas-liquid separator 8. When the liquid level in the gas-liquid separator 8 exceeds the allowable height, the excess liquid can be pumped out from the gas-liquid separator 8 and transported to the liquid receiver 3 through the pump body 14, thereby preventing the compressor 1 from carrying liquid during suction, avoiding liquid slugging, extending the life of the compressor 1, and improving the reliability of the condensing unit during operation.

[0046] According to the condensing unit of the present invention, when the liquid level sensing unit in the gas-liquid separator 8 senses that the liquid level exceeds the allowable height, it feeds back the relevant liquid level information to the controller. The controller can control the pump body 14 to draw the excess liquid from the gas-liquid separator 8 and transport it to the liquid storage tank 3, thereby preventing the compressor 1 from carrying liquid during suction, avoiding liquid slugging, extending the life of the compressor 1, and improving the reliability of the condensing unit during operation.

[0047] like Figure 1As shown, in the condensing unit according to an embodiment of the present invention, the gas-liquid separator 8 is provided with a first outlet 81 and a second outlet 82 spaced apart. The second outlet 82 is located below the first outlet 81. The first outlet 81 is connected to the compressor 1, and the second outlet 82 is connected to the inlet of the liquid receiver 3. The first outlet 81 is connected to the suction port of the compressor 1 to supply gas to the compressor 1, and the second outlet 82 is used to allow excess liquid in the gas-liquid separator 8 to flow out. Therefore, the second outlet 82 is located below the first outlet 81 to facilitate liquid outflow.

[0048] In some embodiments, the distance L between the second outlet 82 and the bottom end of the gas-liquid separator 8 satisfies the following relationship with the height H of the gas-liquid separator 8: 1 / 8H ≤ L ≤ 1 / 3H. It is understood that the second outlet 82 is located below the maximum permissible liquid level of the gas-liquid separator 8, thus facilitating the discharge of liquid from the second outlet 82 into the gas-liquid separator 8. Here, L can be 2 / 24H, 3 / 24H, 4 / 24H, 5 / 24H, 6 / 24H, and 7 / 24H, etc.

[0049] like Figure 1 As shown, in some embodiments, the outlet of the receiver 3 is sequentially connected to a dryer filter 4, a throttle valve 5, and a liquid supply shut-off valve 6. Refrigerant is discharged from the exhaust port of the compressor 1, enters the four-way valve 13 via the first port D, and then enters the condenser 2 via the second port C for condensation. After liquefaction, the refrigerant flows into the receiver 3, where a portion is stored, and the other portion is filtered by the dryer filter 4 and then throttled by the throttle valve 5. After passing through the liquid supply shut-off valve 6 and the suction filter 16, it enters the evaporator, then flows back through the suction shut-off valve 7 to the fourth port E and into the four-way valve 13, and finally enters the gas-liquid separator 8 via the third port S.

[0050] like Figure 1 As shown, a first temperature sensor 11 and a first pressure sensor 12 are provided on the pipeline connecting the compressor 1 and the four-way valve 13. A second temperature sensor 10 and a second pressure sensor 9 are provided on the pipeline connecting the compressor 1 and the gas-liquid separator 8. The first temperature sensor 11, the first pressure sensor 12, the second temperature sensor 10 and the second pressure sensor 9 are all electrically connected to the controller.

[0051] A first temperature sensor 11 and a first pressure sensor 12 are installed on the pipeline connecting compressor 1 and four-way valve 13. The first temperature sensor 11 is used to detect the discharge temperature of compressor 1, and the first pressure sensor 12 is used to detect the condensing pressure of compressor 1. It should be understood that the first temperature sensor 11 and the first pressure sensor 12 can be located near four-way valve 13 or near the discharge port of compressor 1. A second temperature sensor 10 and a second pressure sensor 9 are installed on the pipeline connecting compressor 1 and gas-liquid separator 8. The second temperature sensor 10 is used to detect the suction temperature of compressor 1, and the second pressure sensor 9 is used to detect the evaporation pressure of compressor 1. It should be understood that the second temperature sensor 10 and the second pressure sensor 9 can be located near gas-liquid separator 8 or near suction port of compressor 1.

[0052] In some embodiments, to improve the accuracy of detection, a plurality of first temperature sensors 11 and first pressure sensors 12 may be provided on the pipeline connecting compressor 1 and four-way valve 13; to improve the accuracy of detection, a plurality of second temperature sensors 10 and second pressure sensors 9 may be provided on the pipeline connecting compressor 1 and gas-liquid separator 8.

[0053] like Figure 2 As shown, a method for controlling the liquid level of a gas-liquid separator according to an embodiment of the present invention, used to control the above-mentioned condensing unit, includes:

[0054] Step S10: Real-time acquisition of the operating liquid level of gas-liquid separator 8;

[0055] Step S20: Control the pump body 14 to open or close according to the operating liquid level.

[0056] In step S10, the liquid level sensing unit acquires the operating liquid level of the gas-liquid separator 8 and sends it to the controller.

[0057] It should be noted that the operating liquid level I refers to the real-time liquid level in the gas-liquid separator 8 during the start-up and operation of the condensing unit.

[0058] In step S20, the controller controls the pump body 14 to turn on or off based on the acquired operating liquid level.

[0059] According to the method for controlling the liquid level of a gas-liquid separator according to an embodiment of the present invention, when the liquid level in the gas-liquid separator 8 exceeds the allowable height, the excess liquid can be pumped out from the gas-liquid separator 8 by the pump body 14 and transported to the liquid reservoir 3, thereby preventing the compressor 1 from carrying liquid during suction, avoiding liquid slugging, extending the life of the compressor 1, and improving the reliability of the condenser unit during operation. When the liquid level in the gas-liquid separator meets the requirements, the pump body 14 is controlled to shut down and stop operation.

[0060] like Figure 3 As shown, in some embodiments, step S20 specifically includes:

[0061] Step S21: Determine the real-time liquid level deviation of the gas-liquid separator 8 based on the difference between the operating liquid level and the initial liquid level of the gas-liquid separator 8.

[0062] Step S22: When the real-time liquid level deviation is greater than or equal to the preset liquid level deviation, obtain the compressor's suction temperature, discharge temperature, evaporation pressure, and condensation pressure;

[0063] Step S23: Determine the evaporation temperature and condensation temperature of the compressor based on the evaporation pressure and condensation pressure;

[0064] Step S24: Control the pump body 14 to start based on the suction temperature, evaporation temperature, exhaust temperature and condensation temperature.

[0065] In step S21, the initial liquid level lo of the gas-liquid separator 8 is the liquid level before the condenser unit starts operating. The real-time liquid level deviation of the gas-liquid separator 8 is measured by the liquid level sensing unit and fed back to the controller.

[0066] △L=I-lo, in cm. The preset liquid level deviation range is 5~10cm, that is, the preset liquid level deviation can be 5cm, 5.5cm, 6cm, 6.5cm, 7cm, 7.5cm, 8cm, 8.5cm, 9cm, 9.5cm and 10cm.

[0067] In step S22, the controller can measure the suction temperature Ti of the compressor 1 through the second temperature sensor 10, the evaporation pressure of the compressor 1 through the second pressure sensor 9, the discharge temperature Tj of the compressor 1 through the first temperature sensor 11, and the condensation pressure of the compressor 1 through the first pressure sensor 12.

[0068] In step S23, the controller determines the evaporation temperature Te and the condensation temperature Tc by referring to the stored refrigerant thermodynamic property table using the evaporation pressure and condensation pressure.

[0069] In step S24, the controller controls the pump body 14 to start based on the intake temperature Ti, evaporation temperature Te, exhaust temperature Tj, and condensation temperature.

[0070] According to the method for controlling the liquid level of a gas-liquid separator according to an embodiment of the present invention, the controller controls the pump body 14 to start based on the superheat of the suction gas and the superheat of the exhaust gas, so that when the liquid level in the gas-liquid separator 8 exceeds the allowable height, the liquid is quickly discharged, thereby effectively preventing the compressor 1 from carrying liquid during suction, avoiding liquid slugging, extending the life of the compressor 1, and improving the reliability of the condenser unit during operation. When the liquid level in the gas of the gas-liquid separator meets the requirements, the controller controls the pump body 14 to shut down and stop operation.

[0071] like Figure 4 As shown, in some embodiments, step S24 specifically includes:

[0072] Step S242: Determine the suction superheat Ts and discharge superheat Tu of compressor 1 based on the suction temperature, evaporation temperature, discharge temperature and condensation temperature;

[0073] Step S244: The difference between the intake superheat Ts and the first preset superheat To is taken as the intake superheat deviation △Tx, and the difference between the exhaust superheat Tu and the second preset superheat Tv is taken as the exhaust superheat deviation △Ty.

[0074] Step S246: Control the pump body 14 to start based on the intake superheat deviation and exhaust superheat deviation.

[0075] In step S242, the intake superheat Ts = Ti - Te and the exhaust superheat Tu = Tj - Tc are determined based on the intake temperature Ti, evaporation temperature Te, exhaust temperature Tj, and condensation temperature Tc.

[0076] In step S244, the first preset superheat To = m*(Ti-Tio)+n*(Te-Teo), and the second preset superheat Tv = m*(Tj-Tjv)+n*(Tc-Tcv), where Tio is the suction temperature setpoint, Teo is the evaporation temperature setpoint, Tjv is the exhaust temperature setpoint, Tcv is the condensation temperature setpoint, m is the suction temperature correction coefficient, n is the evaporation temperature correction coefficient, the suction superheat deviation ΔTx = Ts-To, and the exhaust superheat deviation ΔTy = Tu-Tv.

[0077] In step S246, the controller controls the pump body 14 to start based on the intake superheat deviation and the exhaust superheat deviation.

[0078] In some embodiments, step S246 specifically includes:

[0079] When the intake superheat deviation ΔTx is less than or equal to the preset deviation value Ti_OFF, and the exhaust superheat deviation ΔTy is greater than the preset deviation value Ti_OFF, the control pump 14 is turned on and runs at the first power P1.

[0080] When the intake superheat deviation ΔTx is less than or equal to the preset deviation value Ti_OFF, and the exhaust superheat deviation ΔTy is less than or equal to the preset deviation value Ti_OFF, the control pump 14 is turned on and runs at the second power P2, which is greater than the first power P1.

[0081] When the intake superheat deviation ΔTx is greater than the preset deviation value Ti_OFF, and the exhaust superheat deviation ΔTy is less than or equal to the preset deviation value Ti_OFF, the control pump 14 is turned on and runs at the third power P3, which is less than the second power P2.

[0082] In some embodiments, the third power is equal to the first power and the third power is greater than the rated power of the pump body 14. Setting the third power to be equal to the first power and greater than the rated power of the pump body 14 enables timely and rapid discharge of liquid when the liquid level of the gas-liquid separator 8 exceeds the allowable liquid level, while simplifying the program settings of the method for controlling the liquid level of the gas-liquid separator.

[0083] In one specific embodiment, the first power P1 = P3 = Po * 1.3, P2 = Po * 1.5, and Po is the rated power of the pump body 14.

[0084] In some embodiments, the method for controlling the liquid level in a gas-liquid separator further includes:

[0085] Step S26: While the pump body 14 is running, obtain the real-time liquid level deviation;

[0086] Step S27: When the real-time liquid level deviation is less than the preset liquid level deviation within the preset time, control the pump body 14 to shut down.

[0087] In step S26: When the pump body 14 is running, the controller obtains the real-time liquid level deviation through the liquid level sensing unit.

[0088] In step S27, when the real-time liquid level deviation is less than the preset liquid level deviation within a preset time, the pump body 14 is shut down by the controller. The preset time can be a time set as needed, such as 5 minutes, 10 minutes, or 15 minutes.

[0089] According to the embodiments of the present invention, this can ensure that the liquid level of the gas-liquid separator 8 is at the allowable height, thereby preventing the compressor 1 from carrying liquid during suction, avoiding liquid slugging, extending the life of the compressor 1, and improving the reliability of the condenser unit during operation.

[0090] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0091] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0092] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A method for controlling the liquid level in a gas-liquid separator, used to control a condensing unit, characterized in that, The condensing unit includes a compressor, a condenser, a liquid receiver, a gas-liquid separator, a four-way valve, and a controller. The condenser, the liquid receiver, the gas-liquid separator, and the compressor are connected in sequence. The four-way valve includes a first port, a second port, a third port, and a fourth port. The first port is connected to the compressor, the second port is connected to the condenser, the third port is connected to the gas-liquid separator, and the fourth port is used to connect to the evaporator. A pump body is connected between the liquid receiver and the gas-liquid separator. A liquid level sensing unit is provided inside the gas-liquid separator. The compressor, the condenser, the liquid receiver, the gas-liquid separator, the liquid level sensing unit, and the pump body are all electrically connected to the controller. A first temperature sensor and a first pressure sensor are provided on the pipeline connecting the compressor and the four-way valve. A second temperature sensor and a second pressure sensor are provided on the pipeline connecting the compressor and the gas-liquid separator. The first temperature sensor, the first pressure sensor, the second temperature sensor, and the second pressure sensor are all electrically connected to the controller. The method includes: Real-time acquisition of the operating liquid level of the gas-liquid separator; The pump body is turned on or off according to the operating liquid level; The step of controlling the pump body to open or close based on the operating liquid level specifically includes: The real-time liquid level deviation of the gas-liquid separator is determined based on the difference between the operating liquid level and the initial liquid level of the gas-liquid separator. When the real-time liquid level deviation is greater than or equal to the preset liquid level deviation, the compressor's suction temperature, discharge temperature, evaporation pressure, and condensation pressure are obtained. The evaporation temperature and condensation temperature of the compressor are determined based on the evaporation pressure and the condensation pressure. The pump body is controlled to start based on the intake temperature, the evaporation temperature, the exhaust temperature, and the condensation temperature. The step of controlling the pump body to start based on the intake temperature, the evaporation temperature, the exhaust temperature, and the condensation temperature specifically includes: The intake superheat and exhaust superheat of the compressor are determined based on the intake temperature, the evaporation temperature, the exhaust temperature, and the condensation temperature. The difference between the intake superheat and the first preset superheat is taken as the intake superheat deviation, and the difference between the exhaust superheat and the second preset superheat is taken as the exhaust superheat deviation. The pump body is controlled to start based on the intake superheat deviation and the exhaust superheat deviation; The step of controlling the pump body to start based on the intake superheat deviation and the exhaust superheat deviation specifically includes: When the intake superheat deviation is less than or equal to a preset deviation value, and the exhaust superheat deviation is greater than the preset deviation value, the pump body is controlled to start and operate at the first power. When the intake superheat deviation is less than or equal to the preset deviation value and the exhaust superheat deviation is less than or equal to the preset deviation value, the pump body is controlled to start and operate at a second power, which is greater than the first power; When the intake superheat deviation is greater than the preset deviation value and the exhaust superheat deviation is less than or equal to the preset deviation value, the pump body is controlled to start and operate at a third power, which is less than the second power.

2. The method for controlling the liquid level in a gas-liquid separator according to claim 1, characterized in that, The gas-liquid separator has a first outlet and a second outlet spaced apart. The second outlet is located below the first outlet. The first outlet is connected to the compressor, and the second outlet is connected to the inlet of the liquid reservoir.

3. The method for controlling the liquid level in a gas-liquid separator according to claim 2, characterized in that, The distance L between the second outlet and the bottom of the gas-liquid separator satisfies the following relationship with the height H of the gas-liquid separator: 1 / 8H≤L≤1 / 3H.

4. The method for controlling the liquid level in a gas-liquid separator according to claim 2, characterized in that, The outlet of the liquid reservoir is connected in sequence to a dryer filter, a throttle valve, and a liquid supply shut-off valve.

5. The method for controlling the liquid level in a gas-liquid separator according to claim 1, characterized in that, The third power is equal to the first power, and the third power is greater than the rated power of the pump body.

6. The method for controlling the liquid level in a gas-liquid separator according to claim 1, characterized in that, Also includes: The real-time liquid level deviation is acquired during the operation of the pump body; When the real-time liquid level deviation is less than the preset liquid level deviation within a preset time, the pump body is controlled to shut down.

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