Efficient oil separator and oil return system using same
By designing a high-efficiency oil separator and oil return system, timely supply and efficient filtration of lubricating oil are achieved, solving the problem of lubricating oil being difficult to return, reducing equipment size and cost, and ensuring the normal operation and efficiency of the unit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG SINOKING AIR CONDITIONING & REFRIGERATION CO LTD
- Filing Date
- 2025-05-09
- Publication Date
- 2026-04-21
AI Technical Summary
The built-in oil separation system of existing screw compressors is inefficient in flooded refrigeration equipment, making it difficult for lubricating oil to return, which affects the operation of the unit. In addition, the traditional external oil return system increases the size and cost of the equipment.
Design a high-efficiency oil separator that includes a quadruple filtration device and an oil storage tank. Combined with automatic heating and impurity adsorption functions, it achieves efficient separation and return of lubricating oil through multiple filtration and oil storage. It is equipped with a flow switch and a solenoid valve to monitor the return oil volume. The built-in oil chamber is eliminated, and the effect of the traditional system is achieved solely through the return oil system.
It achieves timely supply and efficient filtration of lubricating oil, avoids damage to the compressor due to lack of oil, reduces equipment size and production costs, and ensures normal operation and efficiency of the unit.
Smart Images
Figure CN224151218U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of refrigeration technology, specifically to a high-efficiency oil separator and an oil return system using the oil separator. Background Technology
[0002] In screw compressors, the main functions of lubricating oil are lubrication, cooling, and capacity regulation, making it an essential component for ensuring the normal operation of the compressor. When refrigeration equipment is running, the lubricating oil in the compressor is carried out of the compressor by the high-speed flowing gaseous refrigerant and enters the entire refrigerant circulation system. Conventional screw compressors on the market have a built-in oil chamber with an oil separation system, which provides preliminary gas-liquid separation. However, for flooded systems, because the refrigerant flows through the shell side, the liquid refrigerant evaporates in the evaporator, and the lubricating oil it carries accumulates at the bottom of the evaporator, making it difficult to return to the compressor. In this case, the compressor's built-in oil separation system is far from sufficient; to ensure the normal operation of flooded refrigeration equipment, an external oil return system is required.
[0003] If a high-efficiency oil separator and its return system are designed, the traditional compressor can eliminate its built-in oil chamber and oil separation system. This high-efficiency oil separator and return system can then serve as the compressor's oil storage and filtration components, achieving the same oil return effect as a traditional screw compressor with a built-in oil separator and an external return system. This not only reduces the compressor's size and saves installation space but also significantly lowers production costs without affecting unit efficiency. A well-designed high-efficiency oil separator and its return system are crucial to ensure efficient oil filtration and a timely supply of sufficient and clean lubricating oil to the compressor, guaranteeing the unit's normal operation. Utility Model Content
[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-efficiency oil separator and an oil return system using the oil separator, which can provide the compressor with sufficient and clean lubricating oil in a timely manner. It achieves efficient gas-oil separation; ensures a suitable oil temperature and viscosity during low ambient temperature startup of the unit, thus preventing excessively high oil viscosity from causing difficulties in oil return and lubrication; ensures that the refrigerant oil returning to the compressor is clean and free of metallic impurities, thereby preventing iron filings and other impurities from entering the compressor bearings along with the lubricating oil and causing damage to the compressor bearings; and responds promptly to abnormalities in the oil return system, preventing compressor damage due to oil shortage.
[0005] The purpose of this utility model is achieved through the following technical solution: a high-efficiency oil separator, comprising a shell and an oil storage tank, wherein a refrigerant inlet pipe is provided on one side of the shell for introducing refrigerant, and a gas distributor is connected to the rear of the refrigerant inlet pipe so that the refrigerant gas carrying lubricating oil is evenly distributed after passing through the gas distributor; a refrigerant exhaust pipe is provided on the other side of the shell for discharging refrigerant; a baffle filter plate is provided behind the gas distributor, and several filter screens are provided inside the shell between the baffle filter plate and the refrigerant exhaust pipe to achieve multiple filtration; the oil storage tank is located at the bottom of the shell and communicates with the inner cavity of the oil separator for storing the filtered and separated lubricating oil.
[0006] As a further technical solution, the side wall of the gas distributor has several elliptical holes arranged in a dot matrix.
[0007] As a further technical solution, the baffle filter plate is assembled from multiple pressed baffle blades, with oil collection grooves designed on the baffle blades. The baffle filter plate is installed above the air distribution cylinder as the first filtration device.
[0008] As a further technical solution, the filter screen includes a horizontal filter screen, a lower vertical filter screen, and an upper vertical filter screen arranged sequentially, and all three are connected to the outer casing by partitions. The horizontal filter screen is arranged along the horizontal direction of the outer casing and is located between the baffle filter plate and the lower vertical filter screen, serving as the second filtration device. The lower vertical filter screen is arranged along the vertical direction of the outer casing and is located between the horizontal filter screen and the upper vertical filter screen, serving as the third filtration device. The upper vertical filter screen is arranged along the vertical direction of the outer casing and is located between the lower vertical filter screen and the refrigerant exhaust pipe, serving as the fourth filtration device.
[0009] As a further technical solution, the horizontal filter screen, the lower vertical filter screen, and the upper vertical filter screen are all filled with stainless steel wire mesh, and the lower vertical filter screen and the upper vertical filter screen are installed in a staggered manner, one above the other.
[0010] As a further technical solution, the top of the oil storage tank is equipped with an anti-vortex baffle that communicates with the inner cavity of the oil separator. An oil heating rod is installed on one side of the oil storage tank to heat the lubricating oil, and a return oil valve is installed on the other side of the oil storage tank to discharge the lubricating oil. A strong magnetic block is installed at the bottom of the oil storage tank to adsorb impurities.
[0011] As a further technical solution, the anti-vortex baffle is made of cold-rolled steel plate, and the anti-vortex baffle is evenly distributed with dot matrix holes.
[0012] An oil return system using the above-mentioned oil separator includes an oil separator, a compressor, an evaporator, a condenser, and several pipelines. The compressor discharge port is connected to the refrigerant inlet pipeline of the oil separator through a pipeline. After gas-liquid separation, the refrigerant flows out from the refrigerant discharge pipeline of the oil separator and enters the condenser through a pipeline. The condenser outlet is connected to the evaporator through a pipeline, and the evaporator outlet is connected to the compressor suction port through a pipeline. The lubricating oil separated by the oil separator is discharged from the oil reservoir and connected to the compressor oil return port through the oil return pipeline.
[0013] As a further technical solution, a copper filter, a solenoid valve, a flow switch, and a sight glass are sequentially installed on the oil return line. The copper filter is detachably installed on the side near the oil reservoir. The flow switch is used to detect the amount of oil returned. When the compressor starts, the solenoid valve automatically opens, and when the compressor stops, the solenoid valve automatically closes.
[0014] As a further technical solution, an electronic expansion valve is installed on the connecting pipe between the condenser and the evaporator.
[0015] The beneficial effects of this utility model are as follows:
[0016] The positive and progressive effects of this utility model are as follows:
[0017] 1. This high-efficiency oil separator is designed with a quadruple oil filtration device and an oil storage tank with automatic heating and iron filings adsorption functions. It combines high-efficiency oil filtration, oil return and oil storage functions, and can provide the compressor with sufficient and clean lubricating oil in a timely manner.
[0018] 2. This oil return system is equipped with a flow switch, which can respond promptly when there is an abnormality in the oil return system, thus preventing the compressor from being damaged due to lack of oil.
[0019] 3. This high-efficiency oil separator and its oil return system make it possible to eliminate the need for a built-in oil storage chamber in traditional compressors. This oil return system alone can achieve the same oil return effect as a traditional compressor's built-in oil separator plus an external oil return system. This not only reduces the compressor's size and saves installation space, but also significantly reduces the unit's production costs without affecting its efficiency. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the structure of the oil separator of this utility model, which is connected to the compressor through the return oil pipeline.
[0021] Figure 2 This is a schematic diagram of the connection structure of the oil separator and the oil return system using the oil separator in the refrigeration equipment system.
[0022] Figure 3 This is a schematic diagram of the internal structure of the oil separator and oil storage tank in this utility model.
[0023] Figure 4 This is a schematic diagram of the baffle filter plate in this utility model.
[0024] Figure 5 This is a schematic diagram of the anti-vortex baffle in this utility model.
[0025] Explanation of reference numerals in the attached drawings: Oil separator 1, gas distributor 11, baffle filter plate 12, baffle blade 121, oil collection tank 122, horizontal filter screen 13, lower vertical filter screen 14, upper vertical filter screen 15, refrigerant inlet pipe 16, refrigerant exhaust pipe 17, outer shell 18, partition plate 19, oil reservoir 2, oil heating rod 21, anti-vortex baffle 22, dot matrix hole 221, strong magnetic block 23, oil return valve 24, oil return pipe 3, solenoid valve 31, flow switch 32, copper filter 33, sight glass 34, compressor 4, evaporator 5, condenser 6, electronic expansion valve 7. Detailed Implementation
[0026] The present invention will now be described in detail with reference to the accompanying drawings:
[0027] Example 1: As shown in the attached document Figures 3-5 As shown, a high-efficiency oil separator includes an oil separator 1, a gas distribution cylinder 11, a baffle filter plate 12, baffle blades 121, an oil collection tank 122, a horizontal filter screen 13, a lower vertical filter screen 14, an upper vertical filter screen 15, a refrigerant inlet pipe 16, a refrigerant exhaust pipe 17, a shell 18, a partition plate 19, an oil storage tank 2, an oil heating rod 21, an anti-vortex baffle 22, a dot matrix hole 221, a strong magnetic block 23, and an oil return valve 24.
[0028] Reference Appendix Figure 3 A refrigerant inlet pipe 16 is provided on the left side of the outer casing 18, through which refrigerant enters the outer casing 18. A gas distributor 11 is connected after the refrigerant inlet pipe 16. Preferably, the side wall of the gas distributor 11 has a plurality of 3*5mm elliptical holes arranged in a dot matrix, which disperses the refrigerant gas, allowing the refrigerant gas carrying lubricating oil to achieve uniform flow after passing through the gas distributor 11 (the elliptical holes on the wall). A refrigerant exhaust pipe 17 is provided on the right side of the outer casing 18 to discharge the refrigerant. A set of baffle filter plates 12 is provided after the gas distributor 11. Figure 4As shown, the baffle filter plate 12 is assembled from multiple pressed baffle blades 121 with a spacing of 10 mm. Each baffle blade 121 has an oil collection groove 122. The baffle filter plate 12 is installed above the gas distributor 11 as the first filtration device. Furthermore, the oil-gas mixture passing through the baffle filter plate 12 flows tortuously within the baffle blades 121 and continuously impacts the wall surface. The gaseous refrigerant flows upwards, while the liquid lubricating oil, affected by gravity and viscosity, is collected by the oil collection groove 122 and agglomerates into large droplets, which then slide down the baffle blades 121 to the bottom of the high-efficiency oil separator 1. The baffle filter plate 12 can filter out most of the lubricating oil particles with a size of 5-10 μm, and it is not easily clogged, hence it is used as the first filtration device.
[0029] like Figure 3 As shown, several filters are installed inside the housing 18 between the baffle filter plate 12 and the refrigerant exhaust pipe 17, enabling multiple filtration stages. Furthermore, the filters include a horizontal filter 13, a lower vertical filter 14, and an upper vertical filter 15 arranged sequentially, all connected to the housing 18 via partitions 19. The horizontal filter 13 is arranged horizontally along the housing 18 and located between the baffle filter plate 12 and the lower vertical filter 14, serving as the second filtration stage. The lower vertical filter 14 is arranged vertically along the housing 18 and located between the horizontal filter 13 and the upper vertical filter 15, serving as the third filtration stage. The upper vertical filter 15 is arranged vertically along the housing 18 and located between the lower vertical filter 14 and the refrigerant exhaust pipe 17, serving as the fourth filtration stage.
[0030] Preferably, the horizontal filter 13, the lower vertical filter 14, and the upper vertical filter 15 are all filled with stainless steel wire mesh, and the lower vertical filter 14 and the upper vertical filter 15 are installed in a staggered manner, one above the other. Utilizing the principle of wire mesh filtration, due to the difference in weight and viscosity between gaseous refrigerant and liquid lubricating oil, when the oil-gas mixture passes through the stainless steel packing, the gaseous refrigerant flows upwards, while the liquid lubricating oil is collected by the wire mesh. This three-stage filtration device can filter out lubricating oil with a particle size of 3-5μm, achieving a high filtration efficiency.
[0031] Furthermore, the oil storage tank 2 is located at the bottom of the outer casing 18 and communicates with the inner cavity of the oil separator 1, capable of storing the filtered and separated lubricating oil. An anti-vortex baffle 22 is provided at the top of the oil storage tank 2, thus communicating with the inner cavity of the oil separator 1. Preferably, the anti-vortex baffle 22 is made of cold-rolled steel plate, and has evenly distributed dot matrix holes 221 with a diameter of 8mm. An oil heating rod 21 is installed on one side of the oil storage tank 2 to heat the lubricating oil, and a return oil valve 24 is installed on the other side of the oil storage tank 2 to discharge the lubricating oil. A strong magnetic block 23 is provided at the bottom of the oil storage tank 2 to adsorb impurities.
[0032] Example 2: As Figure 1 , 2 As shown in Figure 3, an oil return system (refrigeration system) using the oil separator described in Embodiment 1 includes an oil separator 1, a gas distribution cylinder 11, a baffle filter plate 12, baffle blades 121, an oil collection tank 122, a horizontal filter screen 13, a lower vertical filter screen 14, an upper vertical filter screen 15, a refrigerant inlet pipe 16, a refrigerant exhaust pipe 17, a housing 18, a partition plate 19, an oil storage tank 2, an oil heating rod 21, an anti-vortex baffle 22, a dot matrix hole 221, a strong magnetic block 23, an oil return valve 24, an oil return pipe 3, a solenoid valve 31, a flow switch 32, a copper filter 33, a sight glass 34, a compressor 4, an evaporator 5, a condenser 6, an electronic expansion valve 7, and several pipelines.
[0033] Reference Appendix Figure 2 The exhaust port of compressor 4 is connected to the refrigerant inlet pipe 16 of oil separator 1 through a pipeline. After gas-liquid separation, the refrigerant flows out from the refrigerant exhaust pipe 17 of oil separator 1 and enters condenser 6 through a pipeline. The outlet of condenser 6 is connected to evaporator 5 through a pipeline. Preferably, an electronic expansion valve 7 is installed on the connecting pipeline between condenser 6 and evaporator 5. The outlet of evaporator 5 is connected to the suction port of compressor 4 through a pipeline.
[0034] The lubricating oil separated by the oil separator 1 is discharged from the oil reservoir 2 and connected to the oil return port of the compressor 4 through the oil return pipeline 3. Further, a copper filter 33, a solenoid valve 31, a flow switch 32, and a sight glass 34 are sequentially installed on the oil return pipeline 3. The copper filter 33 is detachably installed near the oil reservoir 2 to further filter out remaining impurities in the lubricating oil returning to the compressor. The flow switch 32 can detect the amount of oil returned. When the flow switch 32 detects that the amount of oil returned is too low, the unit generates an alarm, and the compressor 4 stops running. The solenoid valve 31 operates synchronously with the compressor 4; when the compressor 4 starts, the solenoid valve 31 automatically opens, and when the compressor 4 stops, the solenoid valve 31 automatically closes.
[0035] When the compressor unit restarts after a prolonged shutdown at low ambient temperatures, the oil viscosity will increase significantly if the oil temperature is too low, causing delayed oil return and ultimately damaging the compressor. The oil heating rod 21 automatically turns on after the unit is connected to power to raise the oil temperature. To ensure sufficient lubrication when the compressor starts, the program is set to preheat the oil heating rod 21 for at least 8 hours before the compressor can start normally. Because the compressor itself generates a large amount of heat during operation, the oil heating rod 21 is set to automatically de-energize after the compressor starts. Simultaneously, when the compressor is shut down, the lubricating oil filtered from the oil reservoir 2 continues to enter the compressor through the oil return line 3 system for a certain period. When the unit restarts after a prolonged shutdown at low ambient temperatures, this lubricating oil will be difficult to heat, affecting lubrication. To solve this problem, a solenoid valve 31 is designed on the oil return line 3. When the compressor stops, the solenoid valve 31 automatically closes to prevent lubricating oil from returning to the compressor; when the compressor starts, the solenoid valve 31 automatically opens for normal oil return.
[0036] The filtered lubricating oil may carry some solid impurities. If these impurities enter the compressor bearings along with the lubricating oil, they can damage the compressor bearings. The removable and replaceable copper filter 33 designed on the oil return line 3 can effectively filter impurities. However, to reduce costs and avoid frequent clogging and replacement of the copper filter 33, a strong magnetic block 23 is installed at the bottom of the oil reservoir 2. This can easily and effectively adsorb metallic impurities in the lubricating oil in a preliminary manner, with low cost and high efficiency. At the same time, if the high-speed flowing gaseous refrigerant impacts the lubricating oil in the oil reservoir, it will make it difficult for the metallic impurities in the lubricating oil to settle and be adsorbed by the strong magnetic block 23. This will also cause some gaseous refrigerant to enter the oil return line, affecting the oil return effect. Therefore, an anti-vortex baffle 22 is designed above the oil reservoir 2.
[0037] A flow switch 32 is designed on the oil return line 3. When the flow switch 32 detects that the oil return is too low, the unit will generate an alarm and the compressor will stop running to prevent the compressor from being damaged due to lack of oil.
[0038] The working process of this utility model:
[0039] When the compressor is powered on again after a long period of shutdown at low ambient temperature, the oil heating rod 21 in the oil reservoir 2 at the bottom of the oil separator 1 automatically turns on to preheat. After preheating for at least 8 hours, the lubricating oil accumulated in the oil reservoir 2 reaches a suitable oil temperature. After the compressor starts, the oil heating rod 21 automatically turns off, and the solenoid valve 31 automatically opens. The unit starts running, and the gaseous refrigerant, after being compressed by the compressor 4, carries the original lubricating oil from the compressor and enters the oil separator 1 at high speed through the refrigerant inlet pipe 16. The high-speed flowing gas-liquid mixture first passes through the gas distribution cylinder 11 and is evenly dispersed to the bottom inlet of the baffle filter plate 12 through the elliptical holes on the cylinder wall. Next, the dispersed oil-gas mixture passes through the second filtration device, the baffle filter plate 12. Inside the baffle blades 121, the mixture continuously deflects and impacts. The liquid lubricating oil, affected by gravity and viscosity, is blocked by the baffle blades 121 and the oil collection groove 122 and filtered downwards, while the gaseous refrigerant flows upwards and out from above the baffle filter plate 12. The baffle filter plate 12 can filter out most of the 5-10μm liquid lubricating oil. The gaseous refrigerant flowing out from above the baffle filter plate 12 then flows sequentially through the second horizontal filter screen 13, the third lower vertical filter screen 14, and the fourth upper vertical filter screen 15. These three filtration devices all utilize the principle of wire mesh filtration. Due to the difference in weight and viscosity between the gaseous refrigerant and the liquid lubricating oil, lubricating oil with a particle size of 3-5μm can be filtered out, resulting in high filtration efficiency. Finally, the refrigerant flows out from the refrigerant exhaust pipe 17 and enters the condenser 6 to complete the next cycle. Due to gravity, all the filtered lubricating oil collects and deposits at the bottom of the oil separator and merges into the oil reservoir 2. After the iron filings and impurities are adsorbed by the strong magnetic block 23 at the bottom of the oil reservoir 2, it flows into the return oil pipe 3 from the return oil valve 24 of the oil reservoir 2, and finally returns to the compressor 4 through the return oil pipe 3.
[0040] If a fault occurs during unit operation, causing oil circuit obstruction or copper filter 33 to become clogged and need replacement, flow switch 32 will detect that the oil return is too low, the unit will generate an alarm, and the compressor will stop running to avoid damage to the compressor due to lack of oil.
[0041] When the compressor stops, the solenoid valve 31 closes, and the lubricating oil is almost entirely stored in the oil reservoir 2, waiting for the unit to restart next time.
[0042] This high-efficiency oil separator and its oil return system combine high-efficiency oil filtration, oil return and oil storage functions. It can be directly applied to compressors without built-in oil chambers as their oil storage and filtration components, and can also be applied to various compressors and refrigeration equipment with oil return requirements.
[0043] It is understood that, for those skilled in the art, any equivalent substitutions or modifications to the technical solutions and inventive concepts of this utility model should fall within the protection scope of the appended claims.
Claims
1. A high efficiency oil separator characterized by: The device includes an outer shell (18) and an oil reservoir (2). A refrigerant inlet pipe (16) is provided on one side of the outer shell (18) for introducing refrigerant. The refrigerant inlet pipe (16) is connected to a gas distributor (11) so that the refrigerant gas carrying lubricating oil can be evenly distributed after passing through the gas distributor (11). A refrigerant exhaust pipe (17) is provided on the other side of the outer shell (18) for discharging refrigerant. A baffle filter plate (12) is provided behind the gas distributor (11). Several filter screens are provided inside the outer shell (18) between the baffle filter plate (12) and the refrigerant exhaust pipe (17) to achieve multiple filtration. The oil reservoir (2) is located at the bottom of the outer shell (18) and is connected to the inner cavity of the oil separator (1) for storing the lubricating oil after filtration and separation.
2. The high efficiency oil separator of claim 1, wherein: The side wall of the gas distributor (11) has several elliptical holes arranged in a dot matrix.
3. The high efficiency oil separator of claim 1 wherein: The baffle filter plate (12) is assembled from multiple pressed baffle blades (121). The baffle blades (121) are designed with oil collection grooves (122). The baffle filter plate (12) is installed above the gas distributor (11) as the first filtration device.
4. The high efficiency oil separator of claim 1 wherein: The filter screen includes a horizontal filter screen (13), a lower vertical filter screen (14), and an upper vertical filter screen (15) arranged sequentially, and all three are connected to the outer shell (18) by a partition (19). The horizontal filter screen (13) is arranged along the horizontal direction of the outer shell (18) and is located between the baffle filter plate (12) and the lower vertical filter screen (14), serving as the second filtration device. The lower vertical filter screen (14) is arranged along the vertical direction of the outer shell (18) and is located between the horizontal filter screen (13) and the upper vertical filter screen (15), serving as the third filtration device. The upper vertical filter screen (15) is arranged along the vertical direction of the outer shell (18) and is located between the lower vertical filter screen (14) and the refrigerant exhaust pipe (17), serving as the fourth filtration device.
5. The high efficiency oil separator of claim 4 wherein: The horizontal filter (13), the lower vertical filter (14), and the upper vertical filter (15) are all filled with stainless steel wire mesh, and the lower vertical filter (14) and the upper vertical filter (15) are installed in a staggered manner, one above the other.
6. The high efficiency oil separator of claim 1 wherein: The top of the oil storage tank (2) is provided with an anti-vortex baffle (22) which is connected to the inner cavity of the oil separator (1). An oil heating rod (21) is installed on one side of the oil storage tank (2) for heating the lubricating oil. An oil return valve (24) is installed on the other side of the oil storage tank (2) for discharging the lubricating oil. A strong magnetic block (23) is provided at the bottom of the oil storage tank (2) for adsorbing impurities.
7. The high efficiency oil separator of claim 6 wherein: The anti-vortex baffle (22) is made of cold-rolled steel plate, and the anti-vortex baffle (22) is evenly distributed with dot matrix holes (221).
8. A return oil system using the oil separator according to any one of claims 1 to 7, characterized by: It includes an oil separator (1), a compressor (4), an evaporator (5), a condenser (6), and several pipelines. The exhaust port of the compressor (4) is connected to the refrigerant inlet pipeline (16) of the oil separator (1) through a pipeline. After gas-liquid separation, the refrigerant flows out from the refrigerant exhaust pipeline (17) of the oil separator (1) and enters the condenser (6) through a pipeline. The outlet of the condenser (6) is connected to the evaporator (5) through a pipeline. The outlet of the evaporator (5) is connected to the suction port of the compressor (4) through a pipeline. The lubricating oil separated by the oil separator (1) is discharged from the oil reservoir (2) and connected to the oil return port of the compressor (4) through the oil return pipeline (3).
9. The oil separation system of claim 8, wherein: The return oil pipeline (3) is sequentially equipped with a copper filter (33), a solenoid valve (31), a flow switch (32) and a sight glass (34). The copper filter (33) is detachably installed on the side near the oil storage tank (2). The flow switch (32) is used to detect the amount of return oil. When the compressor (4) starts, the solenoid valve (31) automatically opens. When the compressor (4) stops, the solenoid valve (31) automatically closes.
10. The oil separation system of claim 8, wherein: An electronic expansion valve (7) is installed on the connecting pipe between the condenser (6) and the evaporator (5).