Air conditioning system

Abstract

The present application provides an air conditioning system. The air conditioning system includes a compressor (1), a condenser (2), a throttling device (3), and an evaporator (4). The evaporator (4) includes a vertical gas collecting pipe (5). The top of the vertical gas collecting pipe (5) is connected to the suction port of the compressor (1) through a suction pipe (6). A liquid return pipe (7) is provided at the bottom of the vertical gas collecting pipe (5). The other end of the liquid return pipe (7) is connected to the suction pipe (6). A control valve (8) is provided on the liquid return pipe (7). The control valve (8) opens the liquid return pipe (7) when the air conditioning system reaches a preset condition. According to the air conditioning system of the present application, it can effectively solve the problem that the refrigerant liquid at the bottom of the evaporator easily returns directly to the compressor suction pipe through the oil return pipe and even reaches the compressor oil sump, which will cause the compressor to start with liquid and be prone to liquid hammer during the next startup process.

Description

Technical Field

[0001] This application relates to the field of refrigeration technology, and particularly to an air-conditioning system. Background Art

[0002] In the current vapor compression refrigeration cycle, the compressor is an important component, serving as the power source for the refrigerant flow in the system cycle. Most compressors in refrigeration cycles require sufficient lubrication to ensure the lubrication of moving parts such as the crankshaft, bearings, and connecting rods, and also to enhance the sealing of the moving surfaces in the compression chamber.

[0003] However, there are phenomena such as mutual solubility and separation between the lubricating oil and the refrigerant. It is easy to retain lubricating oil in the refrigeration system, and it is often impossible to achieve a sufficient lubricating oil return flow rate under some harsh operating conditions, resulting in oil-starved operation of the compressor, and further causing problems such as efficiency decline, overheating and jamming damage of the compressor.

[0004] There are many reasons for the unsmooth oil return. For example, there are oil return dead ends in the structural design, the refrigerant flow rate is low during low-frequency operation and cannot carry more oil back to the compressor, the gas collecting pipe is too high, resulting in insufficient flow rate and oil return at the bottom branch, and so on.

[0005] In the common design of air-conditioning refrigeration systems, an oil separator is used to separate the lubricating oil in the high-pressure exhaust in advance, and through structures such as an oil return capillary, the separated lubricating oil returns to the suction pipe of the compressor in advance under the action of the high-low pressure difference. Therefore, the amount of lubricating oil flowing in the refrigeration system is very small.

[0006] But in an air-conditioning refrigeration system without an oil separator, how to achieve safe oil return is a major issue that system and structural designers need to consider. In an air-conditioning refrigeration system without a gas-liquid separator, preventing liquid slugging of the compressor is also an important issue. The unevaporated refrigerant liquid in the evaporator enters the compressor along with the high-speed refrigerant gas, and the liquid impact on the compressor is likely to cause damage.

[0007] To prevent the liquid refrigerant in the evaporator from entering the compressor, usually the return air main pipe is connected above the possible highest liquid level in the gas collecting main pipe of the evaporator. However, this easily causes liquid refrigerant and lubricating oil to accumulate at the bottom of the gas collecting main pipe. Because the refrigerant flow rate at the bottom branch is small and the flow velocity is low, it cannot carry enough liquid refrigerant and / or lubricating oil upward. After a long operation time, liquid refrigerant accumulates at the bottom of the gas collecting main pipe and some lubricating oil is retained. When the height of these liquids gradually rises, a liquid seal is easily formed at the bottom branch, and the refrigerant flow rate that can pass through is even less, resulting in a "liquid storage" phenomenon at the bottom of the evaporator. Obviously, more lubricating oil will be retained in these liquid refrigerants, easily causing insufficient refrigerant circulation and insufficient oil return in the refrigeration system.

[0008] In the prior art, a gas collecting pipe assembly is proposed. A return oil pipe is connected from the bottom of the gas collecting pipe assembly of the evaporator to the return gas main pipe, and the liquid retained at the bottom of the gas collecting pipe is sucked back to the compressor by the pressure difference. However, after the system stops and stands still, the high and low pressures in the air-conditioning refrigeration system will gradually reach pressure balance. The high-pressure end will squeeze the liquid refrigerant to accumulate in the evaporator. Then, the refrigerant liquid at the bottom of the evaporator can easily return directly to the compressor suction pipe through the return oil pipe and even reach the compressor oil sump, which will cause the compressor to start with liquid and be prone to liquid hammer during the next startup process. Summary of the Invention

[0009] Therefore, the technical problem to be solved by this application is to provide an air-conditioning system that can effectively solve the problem that the refrigerant liquid at the bottom of the evaporator can easily return directly to the compressor suction pipe through the return oil pipe and even reach the compressor oil sump, which will cause the compressor to start with liquid and be prone to liquid hammer during the next startup process.

[0010] To solve the above problems, this application provides an air-conditioning system, including a compressor, a condenser, a throttling device, and an evaporator. The evaporator includes a vertical gas collecting pipe. The top of the vertical gas collecting pipe is connected to the suction port of the compressor through a suction pipe. A liquid return pipe is provided at the bottom of the vertical gas collecting pipe. The other end of the liquid return pipe is connected to the suction pipe. A control valve is provided on the liquid return pipe, and the control valve opens the liquid return pipe when the air-conditioning system reaches a preset condition.

[0011] Preferably, the liquid return pipe includes a reserved section located in the suction pipe, and the reserved section extends along the flow direction of the refrigerant.

[0012] Preferably, the reserved section is coaxially arranged with the suction pipe.

[0013] Preferably, for the part of the liquid return pipe located in the vertical gas collecting pipe, the distance between the inlet end and the bottom of the pipe of the vertical gas collecting pipe is h, and h > 0.

[0014] Preferably, the control valve is a solenoid valve.

[0015] Preferably, a check valve is provided on the pipeline between the control valve and the vertical gas collecting pipe.

[0016] Preferably, the air-conditioning system further includes an oil separator and a capillary tube section. One end of the capillary tube section is connected to the oil return port of the oil separator, and the other end of the capillary tube section is connected to the liquid return pipe between the solenoid valve and the check valve.

[0017] Preferably, the preset condition is that the pressure difference between the vertical gas collecting pipe and the suction pipe reaches a preset value.

[0018] Preferably, the preset condition is that the air-conditioning system reaches the oil return condition.

[0019] Preferably, the liquid return pipe is hermetically welded to the bottom of the vertical gas collecting pipe; and / or, the liquid return pipe is hermetically welded to the suction pipe.

[0020] Preferably, the evaporator further includes a liquid distributor and liquid distribution branches. The liquid distributor is connected to the throttling device, and the liquid distribution branches are respectively connected to the liquid distributor and the evaporator.

[0021] Preferably, the condenser includes a liquid collecting pipe and a gas distributing pipe. The gas distributing pipe is connected to the exhaust port of the compressor, and the liquid collecting pipe is connected to the throttling device.

[0022] The air conditioning system provided by this application includes a compressor, a condenser, a throttling device, and an evaporator. The evaporator includes a vertical gas collecting pipe. The top of the vertical gas collecting pipe is connected to the suction port of the compressor through a suction pipe. A liquid return pipe is provided at the bottom of the vertical gas collecting pipe. The other end of the liquid return pipe is connected to the suction pipe. A control valve is provided on the liquid return pipe. The control valve opens the liquid return pipe when the air conditioning system reaches a preset condition. This air conditioning system adds a liquid return pipe at the bottom of the vertical gas collecting pipe and adds a control valve on the liquid return pipe. During the operation of the air conditioning system, the control valve can be used to control the connection of the liquid return pipe, so that the refrigerant liquid retained at the bottom of the vertical gas collecting pipe is sucked and atomized and then returned to the suction port of the compressor. When the air conditioning system stops, the control valve is used to close the liquid return pipe to prevent the refrigerant liquid from returning to the compressor, thereby preventing the problems of liquid-carrying start-up of the compressor and easy liquid hammer when the compressor starts again, and ensuring the safe and reliable operation of the air conditioning system. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of the air conditioning system according to an embodiment of this application.

[0024] The reference numerals are shown as:

[0025] 1. Compressor; 2. Condenser; 3. Throttling device; 4. Evaporator; 5. Vertical gas collecting pipe; 6. Suction pipe; 7. Liquid return pipe; 8. Control valve; 9. Reserved section; 10. Capillary section; 11. Liquid distributor; 12. Liquid distribution branches; 13. Liquid collecting pipe; 14. Gas distributing pipe; 15. Check valve; 16. Oil separator. Detailed Embodiments

[0026] Referring to Figure 1 As shown, according to the embodiment of this application, the air conditioning system includes a compressor 1, a condenser 2, a throttling device 3, and an evaporator 4. The evaporator 4 includes a vertical gas collecting pipe 5. The top of the vertical gas collecting pipe 5 is connected to the suction port of the compressor 1 through a suction pipe 6. A liquid return pipe 7 is provided at the bottom of the vertical gas collecting pipe 5. The other end of the liquid return pipe 7 is connected to the suction pipe 6. A control valve 8 is provided on the liquid return pipe 7. The control valve 8 opens the liquid return pipe 7 when the air conditioning system reaches a preset condition.

[0027] A liquid return pipe 7 is added to the bottom of the vertical gas collecting pipe 5 in this air-conditioning system, and a control valve 8 is added to the liquid return pipe 7. During the operation of the air-conditioning system, the control valve 8 can be used to control the connection of the liquid return pipe 7, so that the refrigerant liquid retained at the bottom of the vertical gas collecting pipe 5 enters the suction pipe 6 through the liquid return pipe 7, and after being sucked and atomized by the suction pipe 6, it returns to the suction port of the compressor 1. When the air-conditioning system stops, the control valve 8 is used to close the liquid return pipe 7 to prevent the refrigerant liquid from returning to the compressor 1, thereby preventing the problem of liquid-carrying start-up and easy liquid hammer of the compressor 1 when the compressor 1 starts again, and ensuring the safe and reliable operation of the air-conditioning system.

[0028] In one embodiment, the liquid return pipe 7 includes a reserved section 9 located in the suction pipe 6, and the reserved section 9 extends along the flow direction of the refrigerant. The reserved section 9 extends along the flow direction of the refrigerant, and can be the same as the flow direction of the refrigerant in the suction pipe 6, which can be more conveniently sucked out from the reserved section 9 under the suction action of the suction pipe 6, with less resistance, more obvious suction effect, more convenient to realize the atomization of the refrigerant, and effectively avoid the phenomenon of liquid hammer caused by liquid refrigerant directly entering the compressor 1. In this embodiment, the length of the reserved section 9 is L, and L>0. As a preferred embodiment, L≥1 cm.

[0029] In one embodiment, the reserved section 9 is coaxially arranged with the suction pipe 6, which can make the suction of the refrigerant in the reserved section 9 by the suction pipe on the circumferential side of the reserved section 9 more balanced, make the refrigerant flow more stable, and at the same time can further strengthen the atomization effect of the suction pipe 6 on the refrigerant in the reserved section 9.

[0030] In one embodiment, the liquid return pipe 7 is inserted into the vertical gas collecting pipe 5 from the bottom, and the distance between the inlet end of the part of the liquid return pipe 7 located in the vertical gas collecting pipe 5 and the bottom of the pipe of the vertical gas collecting pipe 5 is h, and h>0, so that the inlet end of the liquid return pipe 7 can be higher than the bottom of the pipe of the vertical gas collecting pipe 5, preventing impurities remaining at the bottom of the vertical gas collecting pipe 5 from entering the control valve 8 and causing blockage.

[0031] In one embodiment, the control valve 8 is an electromagnetic valve, and the preset condition is that the pressure difference between the vertical gas collecting pipe 5 and the suction pipe 6 reaches a preset value. In this embodiment, an electromagnetic valve is used as the control valve for controlling the on-off of the liquid return pipe 7. At the same time, a pressure sensor can be used to detect the pressure difference between the inlet and outlet of the liquid return pipe 7, and the electromagnetic valve is controlled according to the detected pressure difference between the inlet and outlet of the liquid return pipe 7. When the pressure difference does not reach the preset value, the electromagnetic valve is controlled to close the liquid return pipe 7 to avoid the refrigerant from flowing back. When the pressure difference reaches the preset value, the electromagnetic valve is controlled to open the liquid return pipe 7, so that the refrigerant in the vertical gas collecting pipe 5 is sucked and atomized and then returns to the suction port of the compressor, effectively avoiding the problem of liquid retention at the bottom of the evaporator and the vertical gas collecting pipe 5.

[0032] In this embodiment, since the solenoid valve's on-off control of the liquid return pipe 7 is an active control, the control threshold of the solenoid valve can be adjusted by regulating the preset pressure difference value, so as to achieve the liquid return adjustment for different operating conditions of the air-conditioning system. It is more flexible in use and has a wider application range, and can better meet the liquid return requirements of the evaporator and the vertical gas collector 5 of different air-conditioning systems, further improving the reliability of the air-conditioning system during operation.

[0033] In one embodiment, a check valve 15 is provided on the pipeline between the control valve 8 and the vertical gas collector 5.

[0034] In one embodiment, the air-conditioning system further includes an oil separator 16 and a capillary tube section 10. One end of the capillary tube section 10 is connected to the oil return port of the oil separator 16, and the other end of the capillary tube section 10 is connected to the liquid return pipe 7 between the solenoid valve and the check valve 15.

[0035] In this embodiment, by connecting the capillary tube section 10 between the liquid return pipe 7 and the oil separator 16, the oil return of the oil separator 16 can be realized by using the capillary tube section 10.

[0036] For this embodiment, it can also be considered that the oil return pipeline composed of the control valve 8 and the capillary tube section 10 is used as a conventional oil return pipeline. Then, on the basis of the conventional oil return pipeline, the liquid return pipe 7 is connected between the control valve 8 and the capillary tube section 10, the other end of the liquid return pipe 7 is connected to the vertical gas collector 5, and a check valve 15 is added to the liquid return pipe 7. In this way, the air-conditioning system of the embodiment of the present application is equivalent to only adding a check valve 15 and a liquid return pipe 7 to add the liquid return function, making full use of the solenoid valve with the original oil return function, with low cost, good practicability and high reliability.

[0037] For this embodiment, the preset condition is that the air-conditioning system reaches the oil return condition. Therefore, the control of the control valve 8 in this embodiment is controlled by the oil return control of the air-conditioning system. There is no need to set up a separate control system additionally. The oil return control of the air-conditioning system itself can be used to realize the liquid return control of the vertical gas collector 5 while carrying out oil return through the liquid return pipe 7, with a simpler structure, a simpler control program and more convenient control.

[0038] In this embodiment, when the solenoid valve is closed, the function of the check valve 15 is to prevent the lubricating oil separated in the oil separator 16 from entering the bottom of the vertical gas collector 5 through the capillary tube section 10. At this time, the outlet of the check valve 15 is in a high-pressure state (the capillary tube does not throttle when there is no fluid flow, and the inlet and outlet of the capillary tube are in a pressure balance state), while the inlet of the check valve 15 is in a low-pressure state. Therefore, the check valve 15 is in reverse cut-off and closed, and there will be no refrigerant or lubricating oil flowing through.

[0039] In other embodiments, the preset conditions for the control valve 8 to open may also be the operating frequency of the compressor, the operating time of the air conditioning system, or other control conditions.

[0040] In one embodiment, the return pipe 7 is welded and sealed to the bottom of the vertical gas collector 5; and / or, the return pipe 7 is welded and sealed to the suction pipe 6, which on the one hand ensures the connection stability between the return pipe 7, the suction pipe 6, and the vertical gas collector 5, and on the other hand ensures the sealing reliability at the connection positions of the return pipe 7, the suction pipe 6, and the vertical gas collector 5.

[0041] In one embodiment, the evaporator 4 further includes a liquid distributor 11 and liquid distribution branches 12. The liquid distributor 11 is connected to the throttling device 3, and the liquid distribution branches 12 are respectively connected to the liquid distributor 11 and the evaporator 4.

[0042] In one embodiment, the condenser 2 includes a liquid collecting pipe 13 and a gas distributing pipe 14. The gas distributing pipe 14 is connected to the exhaust port of the compressor 1, and the liquid collecting pipe 13 is connected to the throttling device 3.

[0043] The above throttling device is, for example, an expansion valve.

[0044] In this embodiment, the exhaust port of the compressor 1 is connected to the gas distributing pipe 14 of the condenser 2 through an exhaust pipe. The gas distributing pipe 14 shunts the high-temperature and high-pressure refrigerant gas into each branch in the condenser 2 through a number of gas distribution branches, where phase change condensation and liquefaction are achieved in the condenser 2, and then it is collected into the liquid collecting pipe 13 through the liquid collecting branches. The total outlet of the liquid collecting pipe 13 is connected to the inlet of the throttling device 3, and the outlet of the throttling device 3 is connected to the liquid distributor 11 of the evaporator 4. The high-pressure refrigerant is throttled, cooled, and depressurized through the throttling device 3. A number of different liquid distribution branches 12 are connected to the liquid distributor 11, and each liquid distribution branch 12 distributes the low-temperature and low-pressure refrigerant liquid into each branch of the evaporator 4, where phase change evaporation and gasification are achieved in the evaporator 4, and then it is collected into the vertical gas collector 5 through the gas collecting branches. The total outlet of the vertical gas collector 5 is connected to the suction pipe 6, and the suction pipe 6 is connected to the suction port of the compressor 1.

[0045] The above air conditioning system is particularly suitable for precision computer room air conditioners. In such special precision air conditioners, the compressor 1, the evaporator 4, the throttling device 3, the indoor fan, etc. are usually placed in the indoor unit, while the condenser 2, the outdoor fan, etc. are placed in the outdoor unit. The indoor unit and the outdoor unit are connected and used through connecting pipes. Since the precision computer room air conditioner operates in the refrigeration mode throughout the year, the vertical gas collector 5 of the evaporator 4 is very suitable for using this design scheme of returning oil liquid at the bottom of the gas collector. The pipeline process that the return pipe assembly needs to connect is relatively short, and the pressure difference can be fully utilized to achieve the oil return control of the compressor.

[0046] When the air-conditioning system starts and runs, the solenoid valve is opened as needed. Then, the liquid at the bottom of the evaporator 4 and / or the vertical header 5 flows under the action of differential pressure suction, passes through the check valve 15 and the solenoid valve, and enters the suction pipe 6, and atomizes at the outlet and returns to the compressor 1. When the air-conditioning system stops or when liquid and oil return are not required, the solenoid valve is closed to prevent liquid from entering the suction pipe 6 of the compressor 1. Obviously, when the solenoid valve is opened, the normal oil return function can be achieved.

[0047] When the refrigeration load is small, the compressor 1 usually operates at a low frequency, the refrigerant circulation volume in the system is small, and there is surplus refrigerant. Therefore, the time interval between oil return and liquid return can be longer. However, when the low-frequency operation time is too long, the compressor 1 may have an oil shortage problem. Therefore, high-frequency operation is required to achieve oil return; the surplus refrigerant at low frequency can accumulate at the bottom of the evaporator 4 and / or the bottom of the vertical header 5. Since the solenoid valve is closed, it cannot flow to the compressor 1, thus ensuring an appropriate refrigerant circulation volume during low-frequency operation and preventing overage. Therefore, the embodiment of the present application can achieve both liquid return and oil return functions, and is a better simplified control scheme.

[0048] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed.

[0049] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and modifications can be made without departing from the technical principle of the present application, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. An air conditioning system, characterized in that, it includes a compressor (1), a condenser (2), a throttling device (3) and an evaporator (4). The evaporator (4) includes a vertical gas collector (5). The top of the vertical gas collector (5) is connected to the suction port of the compressor (1) through a suction pipe (6). A liquid return pipe (7) is provided at the bottom of the vertical gas collector (5). The other end of the liquid return pipe (7) is connected to the suction pipe (6). A control valve (8) is provided on the liquid return pipe (7). The control valve (8) opens the liquid return pipe (7) when the air conditioning system reaches a preset condition; the control valve (8) is a solenoid valve; a check valve (15) is provided on the pipeline between the control valve (8) and the vertical gas collector (5). The air conditioning system further includes an oil separator (16) and a capillary tube section (10). One end of the capillary tube section (10) is connected to the oil return port of the oil separator (16), and the other end of the capillary tube section (10) is connected to the liquid return pipe (7) between the solenoid valve and the check valve (15); the preset condition is that the air conditioning system reaches the oil return condition or the pressure difference between the vertical gas collector (5) and the suction pipe (6) reaches a preset value.

2. The air conditioning system according to claim 1, characterized in that, the liquid return pipe (7) includes a reserved section (9) located in the suction pipe (6), and the reserved section (9) extends along the flow direction of the refrigerant.

3. The air conditioning system according to claim 2, characterized in that, the reserved section (9) is coaxially arranged with the suction pipe (6).

4. The air conditioning system according to claim 1, characterized in that, for the part of the liquid return pipe (7) located in the vertical gas collector (5), the distance between the inlet end and the bottom of the pipe of the vertical gas collector (5) is h, and h > 0.

5. The air conditioning system according to claim 1, characterized in that, the liquid return pipe (7) is welded and sealed with the bottom of the vertical gas collector (5); and / or, the liquid return pipe (7) is welded and sealed with the suction pipe (6).

6. The air conditioning system according to claim 1, characterized in that, the evaporator (4) further includes a liquid distributor (11) and liquid distribution branches (12). The liquid distributor (11) is connected to the throttling device (3), and the liquid distribution branches (12) are respectively connected to the liquid distributor (11) and the evaporator (4).

7. The air conditioning system according to claim 1, characterized in that, the condenser (2) includes a liquid collecting pipe (13) and a gas distributing pipe (14). The gas distributing pipe (14) is connected to the exhaust port of the compressor (1), and the liquid collecting pipe (13) is connected to the throttling device (3).

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