Oil return device for evaporator, evaporator, air conditioning system and control method of air conditioning system

Abstract

The invention relates to the technical field of evaporator oil return devices, and particularly provides an oil return device for an evaporator, the evaporator, an air conditioning system and a control method of the air conditioning system. The oil return device for the evaporator comprises a barrel and a buoy column, a containing cavity and an oil inlet communicated with the containing cavity are formed in the barrel, the evaporator is communicated with the oil inlet so that the liquid level in the evaporator can be flush with the liquid level in the containing cavity, the buoy column is arranged in the containing cavity in an up-down floating mode, and a first oil guide groove is formed in the buoy column; the cylinder is further provided with an oil suction port, the oil inlet and the oil suction port are communicated through a first oil guide groove, and the first oil guide groove is located below the liquid level by a certain distance so that liquid in an oil-rich area in the evaporator can be guided out. By arranging the buoy column capable of automatically adjusting the oil return height along with the height of the liquid level, no matter the liquid level in the evaporator is at any height, it is guaranteed that the liquid taking point injected by the oil suction port is within the depth range of a lubricating oil enrichment area, the oil return effect is improved, the injected liquid return amount can be properly reduced, and the efficiency of a unit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of evaporator oil return devices, and specifically provides an oil return device for an evaporator, an evaporator, an air conditioning system, and a control method thereof. Background Art

[0002] When a centrifugal chiller operates, the low-temperature and low-pressure gaseous refrigerant is compressed by a centrifugal compressor and then becomes a high-temperature and high-pressure gaseous refrigerant. The refrigerant absorbs heat in the evaporator and releases heat in the condenser 3, which externally manifests as the transfer of heat to achieve the purpose of refrigeration. In a traditional centrifugal compressor, since the bearings need to be lubricated, there is a need for an oil tank to store lubricating oil. The lubricating oil in the oil tank is pumped to the bearings of the compressor through an oil pump to achieve lubrication. During normal operation of the unit, the oil-containing liquid refrigerant in the evaporator is returned to the oil separator or the compressor suction port by means of entrainment. The liquid refrigerant in the mixture flashes into a gas and enters the system refrigeration cycle, leaving the liquid lubricating oil to return to the oil tank again under the action of entrainment or a pump to ensure that the oil level in the oil tank is within a safe range. If the oil return is difficult and a large amount of lubricating oil exists in the evaporator, the oil level in the oil tank is too low, and the oil supply pressure will be too low to trigger shutdown protection, resulting in the inability to start the machine.

[0003] The factors causing difficult oil return are usually that the height position of the oil return port is set inappropriately. The density of the lubricating oil and the flashing of the liquid refrigerant determine that the lubricating oil enrichment area is mainly within a certain depth close to the liquid level. However, the liquid level height of the evaporator is different under different working conditions, which causes that if the oil return port is set lower to ensure that it is below the liquid level at any liquid level, when the liquid level is higher, the oil content rate of the mixture at the oil return port is very low, and the oil return effect is very poor; if the oil return port is set higher, when the liquid level height is lower, the oil return port is above the liquid level, resulting in the inability to entrain and return the liquid mixture.

[0004] Therefore, based on such an actual situation, the oil return port is generally set at the middle position of the evaporator. The advantage is that it can ensure that the oil return port is below the liquid level most of the time. The disadvantage is that when the liquid level is higher, the oil return effect is poor, and the unit needs to operate for a long time to ensure the oil return amount. And when the start-stop frequency of the unit is relatively high, due to the small oil return amount, the oil level in the oil tank drops, resulting in the inability to start the machine normally. During the operation of the unit, to ensure the oil return amount at various liquid level heights, the amount of refrigerant for entrainment and return is generally large, so a certain amount of refrigeration capacity and unit efficiency will be lost.

[0005] Correspondingly, there is a need in the art for a new evaporator with an oil return device to solve the problems of poor oil return effect of the existing evaporator oil return device and the decrease in refrigeration capacity and unit efficiency. Summary of the Invention

[0006] The present invention aims to solve the above technical problems, that is, to solve the problems of poor oil return effect of the existing evaporator oil return device and the decrease of refrigerating capacity and unit efficiency.

[0007] In a first aspect, the present invention provides an oil return device for an evaporator. The oil return device includes a cylinder body and a buoy column. An accommodation cavity and an oil inlet communicating with the accommodation cavity are provided on the cylinder body. The evaporator is communicated with the oil inlet so that the liquid level height in the evaporator is flush with that in the accommodation cavity. The buoy column is arranged in the accommodation cavity so as to be able to float up and down. A first oil guiding groove is provided on the buoy column, and the first oil guiding groove is communicated with the oil inlet. An oil suction port is further provided on the cylinder body, and the oil inlet and the oil suction port are communicated through the first oil guiding groove. The first oil guiding groove is located at a certain distance below the liquid level to lead out the liquid in the rich oil area at a certain distance below the liquid level in the evaporator through the first oil guiding groove.

[0008] In the case of adopting the above technical solution, the present invention improves the oil return effect and can appropriately reduce the amount of induced return liquid to a certain extent and improve the efficiency of the unit by providing a buoy column that can automatically adjust the oil return height according to the liquid level height in the evaporator, so that at any height of the liquid level in the evaporator, the liquid extraction point induced by the oil suction port is within the depth range of the lubricating oil enrichment area in the evaporator.

[0009] In an optional technical solution of the above oil return device for an evaporator, the first oil guiding groove is arranged in a ring shape along the circumferential direction of the buoy column.

[0010] In the case of adopting the above technical solution, after the liquid enters the first oil guiding groove, it is shunted along both sides of the central column body and then converges to improve the flow velocity.

[0011] In an optional technical solution of the above oil return device for an evaporator, a second oil guiding groove is provided on the inner wall of the cylinder body, and the oil suction port is communicated with the first oil guiding groove through the second oil guiding groove.

[0012] In the case of adopting the above technical solution, the second oil guiding groove plays a role in guiding the flow direction of the liquid.

[0013] In an optional technical solution of the above oil return device for an evaporator, the height of the oil inlet is greater than that of the oil suction port.

[0014] In the case of adopting the above technical solution, the height of the oil inlet is greater than that of the oil suction port, which is convenient for liquid discharge.

[0015] In an optional technical solution of the above oil return device for an evaporator, a cleaning port is provided at the bottom of the cylinder body.

[0016] In the case of adopting the above technical solution, since the refrigeration system usually contains impurities, the impurities will gradually deposit in the cylinder body along with the flow of the refrigerant. When it is serious, it will cause the buoy column to fail to float normally. Therefore, a cleaning port is opened at the bottom of the cylinder body and connected to the condenser through a pipeline. A normally closed solenoid valve is added to the pipeline. When the unit is running, the condenser is a high-pressure area. The solenoid valve is periodically controlled to open for several seconds so that the high-pressure refrigerant rushes from the condenser into the low-pressure cylinder body to achieve the cleaning effect of washing away the deposits.

[0017] In an alternative technical solution of the above oil return device for the evaporator, a flow blocking groove is provided on the outer surface of the buoy column.

[0018] In the case of adopting the above technical solution, a flow blocking groove is provided on the outer surface of the buoy column. The flow blocking groove can reduce the flow velocity and flow rate of the liquid in the gap between the cylinder body and the buoy column, which not only ensures that the liquid can flow into the cylinder body to make the liquid levels of the evaporator and the cylinder body equal, but also tries to ensure that most of the liquid flows into the first oil guiding groove, and then is ejected into the oil tank or other positions through the oil suction port for the separation of oil and refrigerant to complete the oil return.

[0019] In an alternative technical solution of the above oil return device for the evaporator, the flow blocking groove is in a thread shape or a honeycomb shape.

[0020] In the case of adopting the above technical solution, the thread-shaped or honeycomb-shaped flow blocking groove can effectively reduce the flow velocity of the liquid.

[0021] In an alternative technical solution of the above oil return device for the evaporator, one end of the accommodating cavity is open, and the oil return device further includes a cylinder cover, and the cylinder cover is detachably provided on the opening of the accommodating cavity.

[0022] In the case of adopting the above technical solution, the cover body closes the cylinder body to prevent the liquid from overflowing.

[0023] In an alternative technical solution of the above oil return device for the evaporator, a hollow structure is provided inside the buoy column.

[0024] In the case of adopting the above technical solution, the hollow structure can effectively reduce the weight of the buoy column.

[0025] The present invention also provides an evaporator, and the evaporator includes the oil return device for the evaporator according to any one of the above technical solutions.

[0026] The present invention also provides an air conditioning system, and the air conditioning system includes the oil return device for the evaporator according to any one of the above technical solutions.

[0027] In the alternative technical solution of the above air conditioning system, the air conditioning system includes the oil return device for the evaporator described in the above technical solution; the air conditioning system further includes a refrigerant circulation loop, and a centrifugal compressor, a condenser, and an evaporator are arranged on the refrigerant circulation loop.

[0028] The air conditioning device further includes an oil storage tank and an ejector. The oil storage tank is connected to the oil suction port through an ejector inlet and outlet liquid pipe. The oil storage tank is connected to the centrifugal compressor through a bearing oil supply pipe and a bearing oil return pipe so that lubricating oil enters the centrifugal compressor through the bearing oil supply pipe and returns to the oil storage tank through the bearing oil return pipe; the oil storage tank is connected to the evaporator through a balance pipe to return the refrigerant separated in the oil storage tank to the evaporator through the balance pipe. The ejector is arranged on the ejector inlet and outlet liquid pipe, and the bearing oil supply pipe is connected to the ejector through an ejector pipe, so that a part of the lubricating oil in the oil storage tank and the liquid in the evaporator are sucked into the ejector together.

[0029] In the case of adopting the above technical solution, the air conditioning system injects the liquid in the evaporator into the oil storage tank through the ejector, separates the refrigerant and the lubricating oil through the oil storage tank, the lubricating oil enters the centrifugal compressor bearing for lubrication, and the refrigerant returns to the evaporator.

[0030] In the alternative technical solution of the above air conditioning system, the oil storage tank includes an oil tank and an oil heater. The oil heater is arranged in the oil tank to heat and separate the lubricating oil and the refrigerant in the oil tank; alternatively, the oil storage tank includes an oil separator.

[0031] In the case of adopting the above technical solution, the lubricating oil is separated through the structure combining the oil tank and the oil heater, or the lubricating oil is separated through the oil separator.

[0032] In the alternative technical solution of the above air conditioning system, a cleaning port is arranged at the bottom of the cylinder body. The condenser and the cleaning port are connected through an oil return device cleaning pipe, and a valve body is arranged on the oil return device cleaning pipe.

[0033] In the case of adopting the above technical solution, the high-pressure refrigerant in the condenser enters the cylinder body through the pipeline to clean the impurities in the cylinder body, thereby improving the service life of the oil return device and reducing the occurrence of failures.

[0034] In the alternative technical solution of the above air conditioning system, the air conditioning device further includes a heat exchanger. The heat exchanger is arranged on the bearing oil supply pipe and is located between the centrifugal compressor and the oil storage tank to cool the lubricating oil before it enters the centrifugal compressor bearing.

[0035] In the case of adopting the above technical solution, before the refrigerant enters the compressor bearing for lubrication, the lubricating oil is first cooled by the heat exchanger, so that the bearing can be lubricated and cooled at the same time.

[0036] In an alternative technical solution of the above air-conditioning system, the air-conditioning device further includes an economizer, which is arranged on the refrigerant circulation loop and located between the evaporator and the condenser, so that the liquid refrigerant enters the evaporator. The economizer is also connected to the centrifugal compressor through a make-up gas pipe to send the flashed gaseous refrigerant into the centrifugal compressor for gas replenishment.

[0037] In the case of adopting the above technical solution, the economizer flashes the liquid refrigerant to separate the gaseous refrigerant and the liquid refrigerant. The gaseous refrigerant can replenish the centrifugal compressor with gas to improve the energy efficiency.

[0038] In an alternative technical solution of the above air-conditioning system, the condenser and the centrifugal compressor are connected by a motor cooling pipe, and the evaporator and the centrifugal compressor are connected by a return air pipe, so as to cool the motor of the centrifugal compressor with the refrigerant through the motor cooling pipe. The refrigerant after cooling the motor returns to the evaporator through the return air pipe.

[0039] In the case of adopting the above technical solution, the low-temperature refrigerant enters the compressor motor to cool the compressor motor, and then returns to the evaporator through the return air pipe after cooling.

[0040] A control method for an air-conditioning system, the air-conditioning system includes an oil return device for the evaporator described in the above technical solution; the air-conditioning system further includes a refrigerant circulation loop, and a centrifugal compressor, a condenser, and an evaporator are arranged on the refrigerant circulation loop;

[0041] The air-conditioning device further includes an oil storage tank and an ejector. The oil storage tank is connected to the oil suction port through an ejector inlet and outlet pipe. The oil storage tank is connected to the centrifugal compressor through a bearing oil supply pipe and a bearing oil return pipe, so that the lubricating oil enters the centrifugal compressor through the bearing oil supply pipe and returns to the oil storage tank through the bearing oil return pipe. The oil storage tank is connected to the evaporator through a balance pipe to return the refrigerant separated in the oil storage tank to the evaporator through the balance pipe. The ejector is arranged on the ejector inlet and outlet pipe, and the bearing oil supply pipe is connected to the ejector through an ejector pipe, so that a part of the lubricating oil in the oil storage tank and the liquid in the evaporator are sucked into the ejector together. A cleaning port is arranged at the bottom of the cylinder body, and the condenser and the cleaning port are connected by an oil return device cleaning pipe, and a valve body is arranged on the oil return device cleaning pipe;

[0042] The control method includes:

[0043] Receive an instruction to clean the oil return device;

[0044] Control the valve body to open for a preset duration.

[0045] In the case of adopting the above technical solution, when the unit is running, the condenser is a high-pressure area. Regularly control the solenoid valve to open for several seconds, and the high-pressure refrigerant rushes from the condenser into the low-pressure cylinder body and evaporator, achieving the effect of flushing away the deposits for cleaning.

[0046] Solution 1. An oil return device for an evaporator, characterized in that the oil return device includes a cylinder body and a buoy column. An accommodation cavity and an oil inlet communicating with the accommodation cavity are provided on the cylinder body. The evaporator is communicated with the oil inlet so that the liquid level height in the evaporator is flush with that in the accommodation cavity. The buoy column is arranged in the accommodation cavity so as to be able to float up and down. A first oil guiding groove is provided on the buoy column, and the first oil guiding groove is communicated with the oil inlet. An oil suction port is further provided on the cylinder body, and the oil inlet and the oil suction port are communicated through the first oil guiding groove. The first oil guiding groove is located at a certain distance below the liquid level to guide the liquid in the rich oil area at a certain distance below the liquid level in the evaporator out through the first oil guiding groove.

[0047] Solution 2. The oil return device for an evaporator according to Solution 1, characterized in that the first oil guiding groove is arranged in a ring shape along the circumferential direction of the buoy column.

[0048] Solution 3. The oil return device for an evaporator according to Solution 1, characterized in that a second oil guiding groove is provided on the inner wall of the cylinder body, and the oil suction port is communicated with the first oil guiding groove through the second oil guiding groove.

[0049] Solution 4. The oil return device for an evaporator according to Solution 3, characterized in that the height of the oil inlet is greater than that of the oil suction port.

[0050] Solution 5. The oil return device for an evaporator according to Solution 1, characterized in that a cleaning port is provided at the bottom of the cylinder body.

[0051] Solution 6. The oil return device for an evaporator according to any one of Solutions 1-5, characterized in that a flow blocking groove is provided on the outer surface of the buoy column.

[0052] Solution 7. The oil return device for an evaporator according to Solution 6, characterized in that the flow blocking groove is in a threaded shape or a honeycomb shape.

[0053] Solution 8. The oil return device for an evaporator according to Solution 1, characterized in that one end of the accommodation cavity is open, and the oil return device further includes a cylinder cover, and the cylinder cover is provided on the opening of the accommodation cavity in a manner that can be opened and closed.

[0054] Solution 9. The oil return device for an evaporator according to any one of Solutions 1-8, characterized in that a hollow structure is provided inside the buoy column.

[0055] Solution 10. An evaporator, characterized in that the evaporator includes the oil return device for an evaporator according to any one of Solutions 1-9 above.

[0056] Solution 11. An air conditioning system, characterized in that the air conditioning device includes the oil return device for an evaporator according to any one of Solutions 1-9 above.

[0057] Solution 12. The air conditioning system according to Solution 11, characterized in that the air conditioning system includes the oil return device for an evaporator according to Solution 1; the air conditioning system further includes a refrigerant circulation circuit, and a centrifugal compressor, a condenser, and an evaporator are provided on the refrigerant circulation circuit;

[0058] The air conditioning device further includes an oil storage tank and an ejector. The oil storage tank is connected to the oil suction port through an ejector inlet and outlet liquid pipe. The oil storage tank is connected to the centrifugal compressor through a bearing oil supply pipe and a bearing oil return pipe so that lubricating oil enters the centrifugal compressor through the bearing oil supply pipe and returns to the oil storage tank through the bearing oil return pipe. The oil storage tank is connected to the evaporator through a balance pipe to return the refrigerant separated in the oil storage tank to the evaporator through the balance pipe. The ejector is provided on the ejector inlet and outlet liquid pipe, and the bearing oil supply pipe is connected to the ejector through an ejector pipe, so that a part of the lubricating oil in the oil storage tank and the liquid in the evaporator are sucked into the ejector together.

[0059] Solution 13. The air conditioning system according to Solution 12, characterized in that the oil storage tank includes an oil tank and an oil heater, and the oil heater is provided in the oil tank to heat and separate the lubricating oil and refrigerant in the oil tank; or, the oil storage tank includes an oil separator.

[0060] Solution 14. The air conditioning system according to Solution 12, characterized in that a cleaning port is provided at the bottom of the cylinder body, and the condenser and the cleaning port are connected through an oil return device cleaning pipe, and a valve body is provided on the oil return device cleaning pipe.

[0061] Solution 15. The air conditioning system according to Solution 12, characterized in that the air conditioning device further includes a heat exchanger, and the heat exchanger is provided on the bearing oil supply pipe and is located between the centrifugal compressor and the oil storage tank to cool the lubricating oil before it enters the bearings of the centrifugal compressor.

[0062] Solution 16. The air-conditioning system according to Solution 12, characterized in that the air-conditioning device further comprises an economizer, which is arranged on the refrigerant circulation loop and located between the evaporator and the condenser, so that the liquid refrigerant enters the evaporator. The economizer is also connected to the centrifugal compressor through a make-up gas pipe to send the flashed gaseous refrigerant into the centrifugal compressor for gas replenishment.

[0063] Solution 17. The air-conditioning system according to Solution 12, characterized in that the condenser and the centrifugal compressor are connected through a motor cooling pipe, and the evaporator and the centrifugal compressor are connected through a return air pipe, so as to cool the motor of the centrifugal compressor with refrigerant through the motor cooling pipe, and the refrigerant after cooling the motor returns to the evaporator through the return air pipe.

[0064] Solution 18. A control method for an air-conditioning system, characterized in that the air-conditioning system comprises the oil return device for the evaporator according to Solution 1; the air-conditioning system further comprises a refrigerant circulation loop, on which a centrifugal compressor, a condenser and an evaporator are arranged;

[0065] the air-conditioning device further comprises an oil storage tank and an ejector. The oil storage tank is connected to the oil suction port through an ejector inlet and outlet pipe. The oil storage tank is connected to the centrifugal compressor through a bearing oil supply pipe and a bearing oil return pipe, so that the lubricating oil enters the centrifugal compressor through the bearing oil supply pipe and returns to the oil storage tank through the bearing oil return pipe. The oil storage tank is connected to the evaporator through a balance pipe to return the refrigerant separated in the oil storage tank to the evaporator through the balance pipe. The ejector is arranged on the ejector inlet and outlet pipe, and the bearing oil supply pipe is connected to the ejector through an ejector pipe, so that a part of the lubricating oil in the oil storage tank and the liquid in the evaporator are sucked into the ejector together. A cleaning port is arranged at the bottom of the cylinder body, and the condenser and the cleaning port are connected through an oil return device cleaning pipe, and a valve body is arranged on the oil return device cleaning pipe;

[0066] The control method includes:

[0067] Receiving an instruction to clean the oil return device;

[0068] Controlling the valve body to open for a preset duration.

[0069] Those skilled in the art can understand that for the oil return device of the evaporator of the present invention, the evaporator is filled with a refrigerant mixed with lubricating oil. The oil return device includes a cylinder body and a buoy column. The cylinder body is provided with a receiving cavity and an oil inlet communicating with the receiving cavity. The evaporator is communicated with the oil inlet so that the liquid in the evaporator can flow into the receiving cavity and the liquid level height in the evaporator is flush with the receiving cavity. The buoy column is arranged in the receiving cavity so as to be able to float up and down. The buoy column is provided with a first oil guiding groove. The cylinder body is also provided with an oil suction port. The oil inlet and the oil suction port are communicated through the first oil guiding groove. The first oil guiding groove is located at a certain distance below the liquid surface to lead out the liquid in the rich oil area at a certain distance below the liquid surface in the evaporator through the first oil guiding groove.

[0070] In the case of adopting the above technical solution, the oil return device is connected to the evaporator. Through a number of openings, the interior of the cylinder body of the oil return device is connected to the interior of the evaporator. The buoy column is placed into the receiving cavity of the cylinder body. There is a certain gap between the buoy column and the wall of the receiving cavity, and they can freely slide relative to each other. A part of the liquid at the oil inlet enters the receiving cavity. According to the principle of communicating vessels, the liquid level heights in the receiving cavity of the cylinder body and in the evaporator are always the same. The buoy column always floats on the liquid surface in the receiving cavity under the action of liquid buoyancy and floats up and down with the liquid level height in the evaporator. By designing the mass and size of the buoy column, the first oil guiding groove of the buoy column is set to always be at a certain depth below the liquid surface, so that the liquid in the lubricating oil enrichment area in the evaporator is directly led out of the evaporator from the oil inlet through the first oil guiding groove and the oil suction port. Then, after separating the lubricating oil and the refrigerant, the lubricating oil is collected into the oil tank.

[0071] The present invention improves the oil return effect and can appropriately reduce the amount of induced return liquid to a certain extent, thereby improving the efficiency of the unit to a certain extent by setting a buoy column that can automatically adjust the oil return height according to the liquid level height in the evaporator, ensuring that the liquid extraction point induced by the oil suction port is within the depth range of the lubricating oil enrichment area of the evaporator at any liquid level height in the evaporator. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0073] Figure 1 is a schematic diagram of the air conditioning system of the present invention;

[0074] Figure 2 is a front view schematic diagram of the evaporator of the present invention;

[0075] Figure 3 is Figure 2 a cross-sectional view taken along line A-A in

[0076] Figure 4 is Figure 3 a cross-sectional view taken along line B-B in

[0077] Figure 5 is Figure 2 A cross-sectional view taken along line A-A in it, which is another embodiment;

[0078] Figure 6 is a cross-sectional view of the oil return device of the present invention;

[0079] Figure 7 is a step flow chart of the control method of the air conditioning system of the present invention.

[0080] List of reference numerals:

[0081] 1. Centrifugal compressor; 2. Compressor bearing; 3. Condenser; 4. Economizer; 5. Evaporator;

[0082] 6. Ejector; 7. Oil pump; 8. Oil tank; 9. Oil heater; 10. Plate heat exchanger; 11. Electric valve; 12. Oil return device; 121. Cylinder body; 1211. Oil inlet; 122. Buoy column; 123. First oil guiding groove; 124. Oil suction port; 125. Second oil guiding groove; 126. Cleaning port; 127. Cylinder cover; 13. Solenoid valve;

[0083] 101. Exhaust pipe; 102. Liquid pipeline; 103. Liquid inlet pipe; 104. Suction pipe; 105. Supplementary gas pipe; 106. Oil supply pipe; 107. Ejector pipe; 108. Ejector liquid inlet pipe; 109. Ejector liquid outlet pipe; 110. Bearing oil supply pipe; 111. Oil return pipe; 112. Gas return pipe; 113. Motor cooling pipe; 114. Balance pipe; 115. Oil return device flushing pipe;

[0084] 201. Condenser pressure sensor; 202. Evaporator pressure sensor; 203. Oil supply pressure sensor; 204. Oil return pressure sensor; 205. Oil tank temperature sensor. Detailed embodiments

[0085] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and are not intended to limit the protection scope of the present invention. Those skilled in the art can make adjustments according to needs to adapt to specific application scenarios. For example, although the evaporator of the present application is described in combination with a centrifugal chiller for air conditioning, this is not restrictive. The evaporator of the present invention can also be applied to other types of air conditioning systems or other devices that require an evaporator other than air conditioners.

[0086] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "center", "upper", "lower", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0087] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0088] Referring to Figures 2 to 6 , to solve the problems of poor oil return effect of the existing evaporator oil return device and the decrease of refrigerating capacity and unit efficiency, the present invention provides an oil return device 12 for an evaporator. The oil return device is arranged on the evaporator. The evaporator 5 contains a refrigerant mixed with lubricating oil. The oil return device 12 includes a cylinder body 121 and a buoy column 122. An accommodation cavity and an oil inlet 1211 communicating with the accommodation cavity are arranged on the cylinder body 121. The evaporator 5 is communicated with the oil inlet 1211 so that the liquid in the evaporator 5 can flow into the accommodation cavity and the liquid level height in the evaporator 5 is flush with the accommodation cavity. The buoy column 122 is arranged in the accommodation cavity so as to be able to float up and down. A first oil guiding groove 123 is arranged on the buoy column 122. An oil suction port 124 is also arranged on the cylinder body 121. The oil inlet 1211 and the oil suction port 124 are communicated through the first oil guiding groove 123. The first oil guiding groove 123 is arranged to always be at a certain distance below the liquid level, so as to lead out the liquid in the rich oil area at a certain distance below the liquid level in the evaporator 5 through the first oil guiding groove 123.

[0089] The advantages of the above setting method are as follows: The oil return device 12 is connected to the evaporator 5. Through a number of openings, the inside of the cylinder body 121 of the oil return device 12 is connected to the inside of the evaporator 5. The buoy column 122 is placed into the accommodation cavity of the cylinder body. There is a certain gap between the buoy column 122 and the wall of the accommodation cavity, and relative sliding can be freely performed. A part of the liquid at the oil inlet 1211 enters the accommodation cavity. According to the principle of communicating vessels, the liquid level heights in the cylinder body accommodation cavity and the evaporator 5 are always the same. The buoy column 122 always floats on the liquid surface of the accommodation cavity under the action of liquid buoyancy and floats up and down with the liquid level height in the evaporator 5. By designing the mass and size of the buoy column 122, the first oil guiding groove 123 of the buoy column 122 is set to be always at a certain depth below the liquid surface, so that the liquid in the lubricating oil enrichment area in the evaporator 5 is led out of the evaporator 5 from the oil inlet 1211 through the first oil guiding groove 123 and the oil suction port 124 (refer to Figure 3 and Figure 4 for the liquid flow direction in the evaporator 5 indicated by the arrow in

[0090] ). Then, after separating the lubricating oil and the refrigerant, the lubricating oil is collected into the oil tank.

[0091] Continue to refer to Figures 2 to 6 , in a possible implementation manner, the evaporator 5 contains a refrigerant mixed with lubricating oil. An oil outlet for discharging the coolant is provided on the wall of the evaporator 5. The oil return device 12 includes a cylinder body 121 and a buoy column 122. The cylinder body 121 is provided with an accommodation cavity with one end open. A cylinder cover 127 for opening and closing the opening is provided on the opening. Four oil inlets 1211 communicating with the accommodation cavity are provided on the side wall of the cylinder body 121 at intervals of a certain distance from top to bottom. The cylinder body 121 is arranged on the evaporator 5, and the oil inlet 1211 is connected to the oil outlet of the evaporator 5 so that the inside of the evaporator 5 is communicated with the accommodation cavity of the cylinder body. No matter how the liquid level height in the evaporator 5 changes, the liquid level heights in the evaporator 5 and the accommodation cavity of the cylinder body always remain the same.

[0092] The buoy column 122 is arranged in the accommodation cavity. The buoy column 122 can slide up and down freely. There is a certain gap between the buoy column 122 and the inner wall of the accommodation cavity for accommodating liquid. The buoy column 122 floats in the cylinder 121 under the buoyancy of the bottom liquid. A first oil guide groove 123 is arranged on the buoy column 122. The first oil guide groove 123 is arranged in a ring shape along the circumferential direction of the buoy column 122. One end of the first oil guide groove 123 is aligned with the oil inlet 1211. The first oil guide groove 123 is arranged such that its position is always at a certain distance below the liquid level. After the liquid in the rich oil area enters the first oil guide groove 123, it flows along both sides of the central column and then converges after diversion to increase the flow velocity. Since the gap between the buoy column 122 and the cavity wall is very small, most of the liquid at the oil inlet 1211 enters the first oil guide groove 123. To ensure that the first oil guide groove 123 can communicate with the oil inlet 1211 no matter where the buoy column 122 moves up and down, the height ( Figure 6 D1 in) of the first oil guide groove 123 is greater than the height of the interval between the two oil inlets 1211 ( Figure 6 D2 in).

[0093] Furthermore, a second oil guide groove 125 and an oil suction port 124 connected to the second oil guide groove 125 are arranged on the inner wall of the cylinder 121. The oil suction port 124 is communicated with the first oil guide groove 123 through the second oil guide groove 125. The second oil guide groove 125 plays a role in guiding the flow direction of the liquid and introducing the liquid to the oil suction port 124. The height of the oil inlet 1211 is greater than that of the oil suction port 124, which is convenient for liquid discharge.

[0094] Optionally, the height of the first oil guide groove 123 is greater than the height of the oil inlet 1211, which can increase the speed of the liquid entering the first oil guide groove 123. The cross-section of the first oil guide groove 123 is set to be gradually inclined along the flow direction of the liquid, so that the liquid flowing into the oil suction port 124 flows faster.

[0095] Referring to Figure 5 , in another embodiment, the number of the oil outlet and the oil inlet 1211 can also be set to one. The height of the oil inlet 1211 is greater than the height of the first oil guide groove 123. The oil inlet 1211 is set at a relatively high height, so as to cover a larger oil discharge range. The buoy column 122 slides within the height range of the oil inlet 1211. No matter how the liquid level in the cylinder 121 changes with the evaporator 5, the liquid in the rich oil area of the evaporator 5 always enters the first oil guide groove 123. However, it should be noted that those skilled in the art can set the number of the oil inlet 1211 and the oil outlet according to needs. The number can be one or more. The present invention does not make any restrictions on this and all fall within the protection scope of the present invention.

[0096] Further, since a part of the liquid in the evaporator 5 is to enter the gap between the cylinder body 121 and the buoy column 122, in order to ensure that most of the liquid can enter the first oil guiding groove 123, a flow blocking groove is provided on the outer surface of the buoy column 122. The flow blocking groove is in a thread shape or a honeycomb shape. The flow blocking groove can reduce the flow velocity and the flow rate of the liquid in the gap between the cylinder body 121 and the buoy column 122, ensuring that the liquid can flow into the cylinder body 121 to make the liquid levels of the evaporator 5 and the cylinder body 121 equal, and also ensuring that most of the liquid flows into the first oil guiding groove 123 as much as possible, and then is ejected into the fuel tank or other positions through the oil suction port 124 for separating the oil and the refrigerant, completing the oil return.

[0097] Those skilled in the art can design the weight and size of the buoy column 122 to ensure that the first oil guiding groove 123 on the buoy column 122 is always at a certain depth below the refrigerant liquid level. To achieve this purpose, the material of the buoy column 122 can be metal or non-metal, for example, aluminum, aluminum alloy, titanium, titanium alloy, plastic, etc., or it can also be a combination of metal and non-metal. Further, a hollow structure is provided inside the buoy column 122 to further reduce the weight of the buoy column 122.

[0098] Further, since the refrigeration system usually contains impurities, the impurities will gradually deposit in the cylinder body 121 along with the flow of the refrigerant, and in severe cases, it will cause the buoy column 122 to fail to float normally. Therefore, a cleaning port 126 is opened at the bottom of the cylinder body 121 and connected to the condenser 3 through a pipeline, and a normally closed solenoid valve is added to the pipeline. When the unit is running, the condenser 3 is a high-pressure area. The solenoid valve is periodically controlled to open for several seconds to enable the high-pressure refrigerant to rush into the low-pressure cylinder body 121 from the condenser 3, achieving the cleaning effect of flushing away the deposits.

[0099] Refer to Figure 1 , the present invention also provides an air conditioning system. In a possible implementation manner, the air conditioning system includes a centrifugal compressor 1, a condenser 3, an economizer 4, an evaporator 5, an ejector 6, a fuel tank 8, an oil heater 9, and a plate heat exchanger 10; a compressor bearing 2 and a motor are provided inside the centrifugal compressor 1.

[0100] The outlet of the centrifugal compressor 1 is connected to the condenser 3 through the exhaust pipe 101. The condenser 3 and the economizer 4 are connected through the liquid pipe 102. The economizer 4 and the evaporator 5 are connected through the liquid inlet pipe 103. The evaporator 5 is connected to the suction port of the centrifugal compressor 1. The gaseous refrigerant enters the condenser 3 through the exhaust pipe 101 to release heat. The economizer 4 flash-separates the refrigerant into gas and liquid. After the liquid refrigerant enters the evaporator 5 through the liquid inlet pipe 103 to absorb heat, it returns to the compressor through the suction pipe 104, thus forming a refrigerant circulation loop. The economizer 4 is connected to the gas supply port of the centrifugal compressor 1 through the gas supply pipe 105. An electric valve 11 is provided on the gas supply pipe 105 to control the connection between the gas supply pipe 105 and the gas supply port. The flashed gaseous refrigerant enters the compressor through the gas supply pipe 105 for gas supply.

[0101] Furthermore, the oil suction port 124 of the evaporator 5 is connected to the ejector 6 through the ejector liquid inlet pipe 108. The ejector 6 and the oil tank 8 are connected through the ejector liquid outlet pipe 109. The oil supply pipe 106 and the ejector 6 are connected through the ejector pipe 107. An oil pump 7 and an oil heater 9 are provided on the oil tank 8. The oil tank 8 is connected to the evaporator 5 through the balance pipe 114. The oil tank 8 and the centrifugal compressor 1 are connected through the oil supply pipe 106, the bearing oil supply pipe 110, and the oil return pipeline 111. Alternatively, the bearing oil supply pipe 106 and the oil supply pipe 110 can be combined into one pipe, which can be set by those skilled in the art according to needs. The oil heater 9 separates the lubricating oil and the refrigerant in the oil tank 8 by heating. The refrigerant returns to the evaporator 5 through the balance pipe 114, and the lubricating oil remains in the oil tank 8. After the oil pump 7 is started, the lubricating oil is discharged. One way is to be sucked into the ejector 6 together with the liquid led out from the ejector liquid inlet pipe 108 through the ejector pipe 107 and return to the oil tank 8 through the ejector liquid outlet pipe 109. The other way is to enter the compressor bearing 2 for lubrication after being cooled in the plate heat exchanger 11 through the bearing oil supply pipe 110, and the lubricated lubricating oil returns to the oil tank 8 through the oil return pipeline 111.

[0102] Furthermore, the plate heat exchanger 10 is provided on the bearing oil supply pipe 110. The centrifugal compressor 1 and the oil tank 8 are connected through the oil return pipe 111. The plate heat exchanger 10 cools the lubricating oil and then lubricates the centrifugal compressor bearing 2, and can also play a role in heat dissipation in addition to the lubrication effect.

[0103] Furthermore, the condenser 3 and the centrifugal compressor 1 are connected through the motor cooling pipe 113. The evaporator 5 and the centrifugal compressor 1 are connected through the return gas pipe 112. The low-temperature refrigerant after releasing heat at the condenser 3 cools the compressor motor, and the refrigerant after absorbing heat enters the evaporator 5 through the return gas pipe 112. The cleaning port 126 is connected to the condenser 3 through the oil return device cleaning pipe 115. A normally closed solenoid valve 13 is provided on the oil return device cleaning pipe 115.

[0104] Further, a condenser pressure sensor 201 is provided on the condenser 3 for detecting the refrigerant pressure inside the condenser 3, an evaporator pressure sensor 202 is provided on the evaporator 5 for detecting the pressure inside the evaporator 5, an oil supply pressure sensor 203 is provided on the bearing oil supply pipe 110 for detecting the lubricating oil pressure supplied to the bearing, an oil return pressure sensor 204 is provided on the oil return pipe 11 for detecting the oil return pressure, and a tank temperature sensor 205 is provided on the oil tank 8 for detecting the temperature of the lubricating oil inside the oil tank 8.

[0105] The detailed working process of the air-conditioning system is as follows:

[0106] Refrigeration system: The high-temperature and high-pressure gaseous refrigerant compressed by the compressor 1 enters the condenser 3 through the exhaust pipe 101, undergoes heat exchange and becomes a liquid refrigerant, enters the economizer 4 through the liquid pipeline 102 for flash separation, the liquid at the bottom enters the evaporator 5 through the liquid inlet pipe 103, the gaseous refrigerant at the upper part enters the compressor air inlet through the supplementary air pipe 05, the liquid refrigerant entering the evaporator 5 undergoes heat exchange inside the evaporator 5, becomes a gaseous refrigerant and enters the centrifugal compressor 1 through the suction pipe 104, completing the refrigeration cycle.

[0107] Lubrication system: The liquid refrigerant in the oil tank 8 is heated to the specified temperature by the electric heater 9 and then undergoes flash evaporation. The refrigerant returns to the evaporator 5 through the balance pipe 114, and the lubricating oil remains in the oil tank 8. The lubricating oil in the oil tank 8 is pumped by the oil pump 7 and divided into two paths through the oil supply pipe 106. One path is sucked into the ejector 6 together with the liquid in the ejector inlet pipe 108 through the ejector pipe 107 and returns to the oil tank 8 through the ejector outlet pipe 109. The other path enters the compressor bearing 2 for lubrication after being cooled in the plate heat exchanger 10 through the bearing oil supply pipe 110, and the lubricated lubricating oil returns to the oil tank 8 through the oil return pipeline 111, completing the lubricating oil circuit cycle.

[0108] Motor cooling system: The liquid refrigerant in the condenser 3 enters the motor through the motor cooling pipe 113, and the liquid and gaseous two-phase refrigerant after cooling the motor returns to the evaporator 5 through the return air pipe 112, completing the motor cooling cycle.

[0109] Cleaning of the oil return device: Since impurities are usually contained in the refrigeration system, the impurities will gradually deposit in the cylinder body 121 along with the flow of the refrigerant. When it is serious, the buoy column 122 cannot float normally. Therefore, a cleaning port 126 is opened at the bottom of the cylinder body 121, connected to the condenser 3 with the oil return device cleaning pipe 115, and a normally closed solenoid valve 13 is added. When the unit is operating, the condenser 3 is a high-pressure area. The solenoid valve 13 is periodically controlled to open for several seconds, and the high-pressure refrigerant rushes from the condenser 3 into the low-pressure cylinder body 121 and the evaporator 5, achieving the effect of flushing and cleaning the deposits in the cylinder body 121.

[0110] It should also be noted that the structure of the fuel tank 8 and the oil heater 9 combined for lubricating oil separation can also be replaced by an oil separator, or it can also be other oil storage devices capable of oil-gas separation. The plate heat exchanger 10 can also be replaced by a heat exchanger of other structures, such as a tubular heat exchanger, a honeycomb heat exchanger, etc. The present invention does not impose any restrictions on the structures of the oil storage device and the plate heat exchanger 10, and they all fall within the protection scope of the present invention. In addition, the valve body structures of the electric valve 11 and the solenoid valve 13 can be set according to needs. They can be electric control valve bodies or manual control valve bodies, and they all fall within the protection scope of the present invention. In addition, the pipelines in the air-conditioning system of the present invention can be merged or split according to needs. For example, the oil supply pipe 106 and the bearing oil supply pipe 110 can be merged into one pipeline, etc. Those skilled in the art can set according to needs as long as the two components can be connected through pipelines and the corresponding functions can be achieved, and they all fall within the protection scope of the present invention.

[0111] The present invention also provides a control method for an air-conditioning system. The control method includes:

[0112] Step S10: Receive an instruction to clean the running oil return device;

[0113] Step S20: Control the solenoid valve to open for a preset duration.

[0114] During the operation of the unit, the condenser 3 is a high-pressure area. Periodically control the solenoid valve 13 to open for several seconds, and the high-pressure refrigerant rushes from the condenser 3 into the low-pressure cylinder body 121 and the evaporator 5, achieving the effect of flushing away the deposits for cleaning.

[0115] As described in the first paragraph of this section, the above-mentioned embodiments are only used to illustrate the principle of the present invention and are not intended to limit the protection scope of the present invention. Without departing from the principle of the present invention, those skilled in the art can adjust the above-mentioned structure so that the present invention can be applied to more specific application scenarios.

[0116] So far, the technical solutions of the present invention have been described in combination with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or replacements to the relevant technical features, and the technical solutions after these changes or replacements will all fall within the protection scope of the present invention.

Claims

1. An oil return device for an evaporator, characterized in that, The oil return device includes a cylinder body and a buoy column. The cylinder body is provided with a receiving cavity and an oil inlet communicating with the receiving cavity. The evaporator is communicated with the oil inlet so that the liquid level in the evaporator is flush with the liquid level in the receiving cavity. The buoy column is arranged in the receiving cavity so as to be able to float up and down. A first oil guiding groove is arranged on the buoy column, and the first oil guiding groove is communicated with the oil inlet. An oil suction port is also arranged on the cylinder body, and the oil inlet and the oil suction port are communicated through the first oil guiding groove. The first oil guiding groove is located at a certain distance below the liquid surface to lead out the liquid in the rich oil area at a certain distance below the liquid surface in the evaporator through the first oil guiding groove.

2. The oil return device for an evaporator according to claim 1, characterized in that, The first oil guiding groove is arranged in a ring shape along the circumferential direction of the buoy column.

3. The oil return device for an evaporator according to claim 1, characterized in that, A second oil guiding groove is arranged on the inner wall of the cylinder body, and the oil suction port is communicated with the first oil guiding groove through the second oil guiding groove.

4. The oil return device for an evaporator according to claim 3, characterized in that, The height of the oil inlet is greater than that of the oil suction port.

5. The oil return device for an evaporator according to claim 1, characterized in that, A cleaning port is arranged at the bottom of the cylinder body.

6. The oil return device for an evaporator according to any one of claims 1-5, characterized in that, A flow blocking groove is arranged on the outer surface of the buoy column.

7. The oil return device for an evaporator according to claim 6, characterized in that, The flow blocking groove is in a thread shape or a honeycomb shape.

8. The oil return device for an evaporator according to claim 1, characterized in that, One end of the receiving cavity is open, and the oil return device further includes a cylinder cover, and the cylinder cover is arranged on the opening of the receiving cavity in an openable and closable manner.

9. The oil return device for an evaporator according to any one of claims 1-8, characterized in that, A hollow structure is arranged inside the buoy column.

10. An evaporator, characterized in that, The evaporator includes the oil return device for the evaporator according to any one of claims 1-9.

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