Tail end oil return system of refrigerating system

Abstract

The air conditioner comprises a compressor unit, an oil collecting tank and at least one tail end evaporator, air outlet pipes of the tail end evaporators are connected with oil return branch pipes, the oil return branch pipes are connected to the bottoms of the air outlet pipes, and at least part of the side, close to the air outlet pipes, of each oil return branch pipe vertically extends downwards; the other side of the oil return branch pipe is connected with an oil return collecting pipe, the outlet end of the oil return collecting pipe is communicated with an inlet of an oil collecting tank, and an outlet of the oil collecting tank is directly or indirectly communicated with a lubricating oil inlet or a refrigerant inlet of the compressor unit. The tail end oil return system of the refrigerating system is simple in installation mode, refrigerant oil in the tail end evaporator can be efficiently recycled, and the heat exchange effect of the evaporator is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of refrigeration systems, and particularly relates to an oil return system at the end of a refrigeration system. Background Art

[0002] In the existing oil return methods of refrigeration systems, an oil-gas separation tank is designed at the outlet of the compressor, or liquid is taken from the bottom of the liquid receiver for oil return by means of gas-liquid separation and ejector oil return. For the end of the refrigeration system, few corresponding oil return measures are taken. When the refrigerant enters the evaporator at the end, the inner wall of the heat exchange tube of the evaporator will form an oil film, which will reduce the heat transfer coefficient of the evaporator in the long run and affect the heat transfer at the end. At the same time, the refrigerant accumulates and condenses gradually inside the evaporator, occupying the volume at the bottom of the evaporator, which not only reduces the effective heat transfer area and affects the heat transfer at the end, but also requires regular replenishment of refrigerant due to the continuous reduction of the total amount of refrigerant in the system compressor, consuming manpower and material resources. Summary of the Utility Model

[0003] In view of the above problems, the utility model provides an oil return system at the end of a refrigeration system.

[0004] To achieve the above object, the utility model adopts the following technical solutions:

[0005] An oil return system at the end of a refrigeration system includes a compressor unit, an oil collecting tank, and at least one end evaporator. The outlet pipes of the end evaporators are all connected with oil return branch pipes. The oil return branch pipes are connected to the bottoms of the outlet pipes, and at least part of the oil return branch pipes extends vertically downward near the outlet pipes. The other sides of the oil return branch pipes are connected to an oil return header. The outlet end of the oil return header is communicated with the inlet of the oil collecting tank, and the outlet of the oil collecting tank is directly or indirectly communicated with the lubricating oil inlet or refrigerant inlet of the compressor unit.

[0006] With such a setting, by arranging oil return branch pipes on the outlet pipes of each end evaporator, introducing the oil in each oil return branch pipe into the oil collecting tank through the oil return header, and connecting the outlet of the oil collecting tank with the compressor unit, the end oil return is realized.

[0007] Further, it further includes a return air branch pipe. The outlet pipes are all connected with the return air branch pipe. The return air branch pipes are arranged in parallel with the oil return branch pipes one by one. The connection port of the return air branch pipe and the outlet pipe is higher than the connection port of the oil return branch pipe and the same outlet pipe. The extending direction of the return air branch pipe near the outlet pipe is opposite or perpendicular to the extending direction of the oil return branch pipe. The other side of the return air branch pipe is connected to a refrigeration return air main pipe, and the outlet end of the refrigeration return air main pipe is communicated with the refrigerant inlet of the compressor unit.

[0008] With such a setting, the fluid flow direction inside the oil return branch pipe on the side close to the outlet gas pipe of the end evaporator is set to be vertically downward, and the fluid flow direction inside the gas return branch pipe on the side close to the outlet gas pipe of the end evaporator is opposite to or perpendicular to that of the oil return branch pipe, so that the oil can fall into the oil return branch pipe by its own gravity, realizing the gas-liquid separation of the fluid in the outlet gas pipe of the end evaporator, and the oil return of the refrigerant oil in the end evaporator is realized through the oil return header and the oil storage tank connected to the gas return branch pipe.

[0009] Further, the system further includes a heat exchanger and a condenser. The high-temperature gas outlet of the compressor unit is communicated with the condenser through an exhaust main pipe. The refrigerant inlet of the heat exchanger is connected to the outlet of the oil storage tank through a heat exchange inlet oil pipe. The refrigerant outlet of the heat exchanger is communicated with the lubricating oil inlet or the refrigerant inlet of the compressor unit through a suction return oil pipe. The heat medium inlet of the heat exchanger is connected to the exhaust main pipe through a heat supply inlet pipe. The heat medium outlet of the heat exchanger is connected to the exhaust main pipe through a heat supply outlet pipe. The connection points of the heat supply inlet pipe and the heat supply outlet pipe with the exhaust main pipe are arranged at intervals in sequence along the gas flow direction in the exhaust main pipe.

[0010] With such a setting, the refrigerant in the refrigerant and refrigerant oil mixture in the liquid collection tank is vaporized through the heat exchanger to realize the separation of the refrigerant and the refrigerant oil, avoiding the influence of liquid accumulation on the normal operation of the compressor unit.

[0011] Further, stop valves are provided at both ends of the heat exchange inlet oil pipe and the suction return oil pipe close to the heat exchanger. A differential pressure regulating valve is provided between the connection points of the heat supply inlet pipe and the heat supply outlet pipe with the exhaust main pipe. Stop valves and stop check valves are respectively provided on the heat supply inlet pipe and the heat supply outlet pipe.

[0012] With such a setting, by setting a pressure value on the differential pressure regulating valve, the differential pressure regulating valve is opened and closed according to the differential pressure situation, realizing the control that the high-temperature gas passes through the heat exchanger preferentially. By setting the stop valve, it is more convenient to control the on-off of the heat medium of the heat exchanger, and the stop check valve can prevent the fluid in the heat supply outlet pipe from flowing back.

[0013] Further, stop valves are provided on both sides before and after the differential pressure regulating valve between the connection points of the heat supply inlet pipe and the heat supply outlet pipe with the exhaust main pipe.

[0014] With such a setting, when the differential pressure regulating valve is damaged, the stop valves on its front and rear sides are closed, facilitating the maintenance of the differential pressure regulating valve.

[0015] Further, the top of the oil storage tank is communicated with the refrigeration gas return main pipe through a balance pipe. With such a setting, the balance pipe balances the pressure between the oil storage tank and the refrigeration system, facilitating the internal liquid of the oil return header to flow into the oil storage tank.

[0016] Further, there are multiple said end evaporators, including air coolers and pipe coils. The outlet ends of the air cooler outlet pipes are each connected to an oil return branch pipe and a gas return branch pipe through a tee. The relatively arranged ports in the tee are horizontally arranged and are respectively connected to the air cooler outlet pipe and the gas return branch pipe, and the other port in the tee is vertically downward and is connected to the oil return branch pipe; the outlet pipe of the pipe coil is a pipe coil exhaust manifold. Openings are made at the bottom side wall of the pipe coil exhaust manifold, and the oil return branch pipe is connected to the pipe coil exhaust manifold through the openings. The side of the oil return branch pipe close to the pipe coil exhaust manifold is perpendicular to the pipe coil exhaust manifold and extends vertically downward, and the side of the gas return branch pipe close to the pipe coil exhaust manifold extends vertically upward.

[0017] With such an arrangement, the gas and liquid in the gas-liquid mixture in the air cooler outlet pipe are separated under the action of gravity through the tee, and the gas and liquid in the gas-liquid mixture are separated under the action of gravity through the height difference between the gas return branch pipe and the pipe coil exhaust manifold connected by the oil return branch pipe.

[0018] Further, the system further includes a heat exchanger. The refrigerant inlet of the heat exchanger is connected to the outlet of the oil storage tank through a heat exchange inlet oil pipe, and the refrigerant outlet of the heat exchanger is connected to the lubricating oil inlet or refrigerant inlet of the compressor unit through a suction return oil pipe;

[0019] The heat medium inlet of the heat exchanger is connected to the high-pressure liquid storage tank of the pump liquid supply system or to the domestic waste heat or waste heat pipeline through a heat supply inlet pipe, and the heat medium outlet of the heat exchanger is connected to the high-pressure liquid storage tank of the pump liquid supply system or to the domestic waste heat or waste heat pipeline through a heat supply outlet pipe. With such an arrangement, various waste heat can be recovered and utilized.

[0020] The end oil return system of the refrigeration system of the present utility model has a simple installation method, and all the materials used are common materials in the refrigeration installation project. It can efficiently recover the refrigeration oil in the end evaporator, reduce the refrigeration oil filling amount of the refrigeration system, and improve the heat exchange effect of the evaporator. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the end oil return system of the refrigeration system according to an embodiment of the present utility model.

[0022] Wherein, 1 - compressor unit, 2 - condenser, 3 - air cooler, 4 - pipe coil, 5 - heat exchanger, 6 - oil storage tank, 7 - stop valve, 8 - stop check valve, 9 - differential pressure regulating valve, 11 - refrigeration gas return main pipe, 12 - suction return oil pipe, 13 - exhaust main pipe, 14 - heat supply inlet pipe, 15 - heat supply outlet pipe, 31 - air cooler oil return header, 32 - air cooler gas return branch pipe, 41 - pipe coil oil return header, 42 - pipe coil gas return branch pipe, 61 - oil return header, 62 - balance pipe, 63 - heat exchange inlet oil pipe. Detailed Embodiments

[0023] The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present utility model and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts belong to the scope of protection of the present utility model.

[0024] As Figure 1 shown, an end oil return system of a refrigeration system includes a compressor unit 1, an oil collection tank 6, and at least one end evaporator. The outlet pipes of the end evaporators are all connected with oil return branch pipes. The oil return branch pipes are connected to the bottom of the outlet pipes. At least a part of one side of the oil return branch pipe close to the outlet pipe extends vertically downward; the other side of the oil return branch pipe is connected to an oil return header 61. The outlet end of the oil return header 61 is communicated with the inlet of the oil collection tank 6. The outlet of the oil collection tank 6 is directly or indirectly communicated with the lubricating oil inlet or the refrigerant inlet of the compressor unit 1.

[0025] With such a setting, by arranging oil return branch pipes on the outlet pipes of each end evaporator and introducing the oil in each oil return branch pipe into the oil collection tank 6 through the oil return header, and connecting the outlet of the oil collection tank 6 to the compressor unit 1, end oil return is achieved.

[0026] In this embodiment, it further includes a suction branch pipe. The outlet pipes are all connected with the suction branch pipe. The suction branch pipes are arranged in parallel with the oil return branch pipes one by one. The connection port of the suction branch pipe and the outlet pipe is higher than the connection port of the oil return branch pipe and the same outlet pipe. The extending direction of one side of the suction branch pipe close to the outlet pipe is opposite to or perpendicular to the extending direction of the oil return branch pipe. The other side of the suction branch pipe is connected to a refrigeration suction main pipe 11. The outlet end of the refrigeration suction main pipe 11 is communicated with the refrigerant inlet of the compressor unit 1.

[0027] Specifically, in this embodiment, the terminal evaporator can be a cooling fan 3 and / or a pipe coil 4. Of course, as other embodiments, the terminal evaporator can also be other types known in the art, such as fan coil units, air handling units, etc. In this embodiment, the terminal evaporator includes a cooling fan 3 and a pipe coil 4. The oil return branch pipe and the gas return branch pipe connected to the outlet of the outlet pipe 33 of the cooling fan are respectively defined as the cooling fan oil return header 31 and the cooling fan gas return branch pipe 32. The oil return branch pipe and the gas return branch pipe connected to the outlet of the exhaust gas header 43 of the pipe coil are respectively defined as the pipe coil oil return header 41 and the pipe coil gas return branch pipe 42. The other ends of the cooling fan oil return header 31 and the pipe coil oil return header 41 are both connected to the oil return header 61. The other ends of the cooling fan gas return branch pipe 32 and the pipe coil gas return branch pipe 42 are both connected to the refrigeration gas return main pipe 11. The outlet end of the oil return header 61 is communicated with the inlet of the oil storage tank 6. The outlet of the oil storage tank 6 is communicated with the lubricating oil inlet of the compressor unit 1. The outlet end of the refrigeration gas return main pipe 11 is communicated with the refrigerant inlet of the compressor unit 1.

[0028] It can be understood that when the refrigeration system operates, the refrigerant (liquid) condensed by the condenser 2 throttles and expands through the valve assembly on the pipeline (gas-liquid two-phase) and then enters the cooling fan 3 and the pipe coil 4 for heat exchange (evaporation and heat absorption). By setting the oil return header 31 and the refrigeration gas return main pipe 11, as well as the oil return branch pipe and the gas return branch pipe at the outlet pipe of the terminal evaporator and communicated with the oil return header 31 and the refrigeration gas return main pipe 11, the gas-liquid mixture discharged after heat exchange from multiple terminal evaporators, the cooling fan 3 and the pipe coil 4, is separated and then enters their respective gas return branch pipes and oil return branch pipes respectively, and finally converges in the oil return header 61 and the refrigeration gas return main pipe 11. The gas part in the refrigeration gas return main pipe 11 enters the refrigeration system cycle, and the liquid part in the oil return header 61 finally flows into the oil storage tank 6 for aggregation, so as to realize the oil return of the refrigeration oil inside the terminal evaporator.

[0029] The liquid aggregated and flowing into the oil storage tank 6 is generally a mixture of refrigerant liquid and refrigeration oil and cannot directly enter the compressor unit 1, otherwise it will cause liquid accumulation and affect the normal operation of the compressor unit 1. Therefore, the two need to be separated. To achieve the separation of the refrigerant and the refrigeration oil, in this embodiment, there are a heat exchanger 5 and a condenser 2. The high-temperature gas outlet of the compressor unit 1 is communicated with the condenser 2 through the exhaust main pipe 13. The refrigerant inlet of the heat exchanger 5 is communicated with the outlet of the oil storage tank 6 through the heat exchange oil inlet pipe 63. The refrigerant outlet of the heat exchanger 5 is communicated with the lubricating oil inlet or the refrigerant inlet of the compressor unit 1 through the suction oil return pipe 12. The heat medium inlet and the heat medium outlet of the heat exchanger 5 are respectively connected to the exhaust main pipe 13 through the heat supply inlet pipe 14 and the heat supply outlet pipe 15. The connection points of the heat supply inlet pipe 14 and the heat supply outlet pipe 15 with the exhaust main pipe 13 are arranged at intervals in sequence along the gas flow direction in the exhaust main pipe 13.

[0030] Set in this way, the refrigerant in the refrigerant and refrigerant oil mixture in the liquid collection tank 6 is vaporized through the heat exchanger 5 to separate the refrigerant from the refrigerant oil, avoiding liquid accumulation and affecting the normal operation of the compressor unit.

[0031] In one embodiment, stop valves 7 are provided at one ends of the heat exchange inlet oil pipe 63 and the suction return oil pipe 12 close to the heat exchanger 5. A differential pressure regulating valve 9 is provided between the connection points of the heat supply inlet pipe 14 and the heat supply outlet pipe 15 with the exhaust main pipe 13. Stop valves 7 and stop check valves 8 are respectively provided on the heat supply inlet pipe 14 and the heat supply outlet pipe 15.

[0032] Set in this way, a pressure value is set on the differential pressure regulating valve 9. When the pressure difference between its front and back sides is less than the set pressure value, it is in a closed state, and the high-temperature gas in the exhaust main pipe 13 passes through the heat exchanger 5. When the pressure difference between its front and back sides is greater than the set pressure value, the differential pressure regulating valve 9 automatically opens to release the pressure difference between its front and back sides until it is less than the set pressure value and then automatically closes, controlling the high-temperature gas to preferentially pass through the heat exchanger 5.

[0033] In some embodiments, a high preset liquid level value and a low preset liquid level value are provided on the oil collection tank 6. The positions of the high preset liquid level value and the low preset liquid level value can be set according to needs. Generally, it is recommended that the positions on the upper and lower sides of the side wall of the oil collection tank 6, at a distance of ¼ to ⅓ of the total height of the tank from the top and bottom of the tank, be used as the high preset liquid level value and the low preset liquid level value respectively. Set in this way, it is convenient to observe the liquid level position in the oil collection tank. On the one hand, the liquid in the oil collection tank 6 can be timely passed through the heat exchanger for heat exchange and then returned to the oil. When the liquid level in the oil collection tank 6 is lower than the low preset liquid level value, the stop valves 7 on the heat exchange inlet oil pipe 63 and the suction return oil pipe 12 can be timely closed.

[0034] Stop valves 7 are provided on both the front and back sides of the differential pressure regulating valve 9 between the connection points of the heat supply inlet pipe 14 and the heat supply outlet pipe 15 with the exhaust main pipe 13. Set in this way, when the differential pressure regulating valve 9 is damaged, the stop valves 7 on its front and back sides are closed, facilitating the maintenance of the differential pressure regulating valve 9.

[0035] With such a setting, the two stop valves 7 on the exhaust main pipe 13, the stop valve 7 on the heat supply inlet pipe 14, and the stop check valve 8 on the heat supply outlet pipe 15 are in the normally open state. When the liquid in the oil collecting tank 6 accumulates to the high preset liquid level value, manually open the stop valves 7 on the hot oil inlet pipe 63 and the suction return oil pipe 12, so that the liquid-oil mixture in the oil collecting tank 6 enters the heat exchanger 5, realizing that the high-temperature gas at the compressor outlet heats the liquid-oil mixture, vaporizing the liquid refrigerant and then returning it to the compressor unit 1 together with the liquid refrigerant oil through the suction return oil pipe 12 and the refrigeration return gas main pipe 11, realizing the return of the refrigerant oil and the recycling of the refrigerant; when the liquid level of the liquid in the oil collecting tank reaches the low preset liquid level value, close the stop valves 7 on the hot oil inlet pipe 63 and the suction return oil pipe 12, and do not open the stop valves 7 on the hot oil inlet pipe 63 and the suction return oil pipe 12 again until the liquid level of the oil collecting tank 6 accumulates to the high preset liquid level value next time, and perform such cyclic operation. In some other embodiments, a high liquid level sensor and a low liquid level sensor can be respectively arranged at the high preset liquid level value and the low preset liquid level value of the oil collecting tank, and at the same time, the stop valves 7 on the hot oil inlet pipe 63 and the suction return oil pipe 12 are replaced with solenoid valves, and the high liquid level sensor and the low liquid level sensor are signal-controlledly connected to the solenoid valves to realize the automatic control of the heat exchange part.

[0036] In some embodiments, the oil collecting tank 6 is also communicated with the refrigeration return gas main pipe 11 through a balance pipe 62. With such a setting, by setting the balance pipe 62, the pressure between the oil collecting tank 6 and the refrigeration system can be balanced, facilitating the liquid inside the oil return header 61 to flow into the oil collecting tank 6; other interfaces on the oil collecting tank 6 only need to meet the pressure volume design specifications.

[0037] In some embodiments, to facilitate the gas-liquid separation of the gas-liquid mixture composed of gaseous condensate, liquid lubricating oil, and liquid refrigerant discharged from the air outlet pipe of the air cooler 3 under the action of gravity at the outlet of the air outlet pipe 33 of the air cooler, the outlet ends of the air outlet pipes of the air cooler are all connected to the air cooler oil return header 31 and the air cooler return gas branch pipe 32 through a tee. The ports arranged opposite to each other in the tee are horizontally arranged and are respectively communicated with the air outlet pipe of the air cooler and the air cooler return gas branch pipe 32, and the other port in the tee is vertically arranged and is communicated with the air cooler oil return header 31; openings are made on the side wall of the exhaust header of the exhaust pipe 4, and the exhaust pipe oil return header 41 is communicated with the exhaust header of the exhaust pipe through the openings, and the side of the exhaust pipe oil return header 41 close to the exhaust header of the exhaust pipe is perpendicular to the exhaust header of the exhaust pipe and extends vertically downward, and the side of the exhaust pipe return gas branch pipe 42 close to the exhaust header of the exhaust pipe extends vertically upward.. Based on this setting, the gas and liquid in the gas-liquid mixture in the air outlet pipe of the air cooler are separated under the action of gravity through the tee, and the gas and liquid in the gas-liquid mixture are separated under the action of gravity through the height difference between the exhaust pipe oil return header 41 and the exhaust pipe return gas branch pipe 42 connected to the exhaust pipe of the exhaust pipe.

[0038] In some other embodiments, to facilitate the gas-liquid separation of the gas-liquid mixture composed of gaseous refrigerant, liquid lubricating oil, and liquid refrigerant discharged from the outlet pipes of the cooling fan 3 and the coil pipe 4 under the action of gravity at the outlet of the outlet pipe 33 of the cooling fan, a connection port 32 for the return air branch pipe of the cooling fan and a connection port 42 for the return air branch pipe of the coil pipe may also be respectively opened on the side walls of the outlet pipe of the cooling fan and the exhaust gas collecting header of the coil pipe.

[0039] In this embodiment, the heat source of the heat exchanger is the high-temperature gaseous refrigerant in the compressor outlet pipe. In some other embodiments, the heat source of the heat exchanger 5 may also be the high-pressure liquid storage tank of the pump feeding system, or the domestic waste heat or waste heat pipe.

[0040] Those of ordinary skill in the art should understand that the above description is only specific embodiments of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. An end oil return system for a refrigeration system, characterized in that, It includes a compressor unit (1), an oil collecting tank (6), and at least one end evaporator. The outlet pipes of the end evaporators are all connected with oil return branch pipes. The oil return branch pipes are connected to the bottom of the outlet pipes, and at least part of the side of the oil return branch pipe close to the outlet pipe extends vertically downward; the other side of the oil return branch pipe is connected to an oil return header (61), and the outlet end of the oil return header (61) is communicated with the inlet of the oil collecting tank (6). The outlet of the oil collecting tank (6) is directly or indirectly communicated with the lubricating oil inlet or the refrigerant inlet of the compressor unit (1).

2. The end oil return system of a refrigeration system according to claim 1, characterized in that, It further includes a suction branch pipe. The outlet pipes are all connected with the suction branch pipes. The suction branch pipes are arranged in parallel with the oil return branch pipes one by one. The connection port of the suction branch pipe and the outlet pipe is higher than the connection port of the oil return branch pipe and the same outlet pipe. The extending direction of the side of the suction branch pipe close to the outlet pipe is opposite or perpendicular to the extending direction of the oil return branch pipe. The other side of the suction branch pipe is connected to a refrigeration suction main pipe (11), and the outlet end of the refrigeration suction main pipe (11) is communicated with the refrigerant inlet of the compressor unit (1).

3. The end oil return system of a refrigeration system according to claim 1 or 2, characterized in that, The system further includes a heat exchanger (5) and a condenser (2). The high-temperature gas outlet of the compressor unit (1) is communicated with the condenser (2) through an exhaust main pipe (13). The refrigerant inlet of the heat exchanger (5) is connected to the outlet of the oil collecting tank (6) through a heat exchange inlet oil pipe (63). The refrigerant outlet of the heat exchanger (5) is connected to the lubricating oil inlet or the refrigerant inlet of the compressor unit (1) through a suction return oil pipe (12); the heat medium inlet of the heat exchanger (5) is connected to the exhaust main pipe (13) through a heat supply inlet pipe (14). The heat medium outlet of the heat exchanger (5) is connected to the exhaust main pipe (13) through a heat supply outlet pipe (15). The connection points of the heat supply inlet pipe (14) and the heat supply outlet pipe (15) with the exhaust main pipe (13) are arranged at intervals in sequence along the gas flow direction in the exhaust main pipe (13).

4. The end oil return system of a refrigeration system according to claim 3, characterized in that, Stop valves (7) are provided at one ends of the heat exchange inlet oil pipe (63) and the suction return oil pipe (12) close to the heat exchanger (5); a differential pressure regulating valve (9) is provided between the connection points of the heat supply inlet pipe (14) and the heat supply outlet pipe (15) with the exhaust main pipe (13); stop valves (7) and stop check valves (8) are respectively provided on the heat supply inlet pipe (14) and the heat supply outlet pipe (15).

5. The end oil return system of a refrigeration system according to claim 4, characterized in that, Stop valves (7) are provided on both sides before and after the differential pressure regulating valve (9) between the connection points of the heat supply inlet pipe (14) and the heat supply outlet pipe (15) with the exhaust main pipe (13).

6. The end oil return system of a refrigeration system according to claim 2, characterized in that, The top of the oil collecting tank (6) is communicated with the refrigeration suction main pipe (11) through a balance pipe (62).

7. An end oil return system for a refrigeration system according to any one of claims 1-2 or claims 4-6, characterized in that, There are multiple said end evaporators, including a cooling fan (3) and a pipe coil (4). The outlet ends of the air outlet pipes of the cooling fans (3) are each connected to an oil return branch pipe and a gas return branch pipe through a tee. The relatively arranged ports in the tee are horizontally arranged and are respectively connected to the air outlet pipe of the cooling fan (3) and the gas return branch pipe. The other port in the tee is vertically downward and is connected to the oil return branch pipe. The air outlet pipe of the pipe coil is an exhaust manifold of the pipe coil. An opening is made at the bottom side wall of the exhaust manifold of the pipe coil, and the oil return branch pipe is connected to the exhaust manifold of the pipe coil through the opening. The side of the oil return branch pipe close to the exhaust manifold of the pipe coil is perpendicular to the exhaust manifold of the pipe coil and extends vertically downward, and the side of the gas return branch pipe close to the exhaust manifold of the pipe coil extends vertically upward.

8. The end oil return system of a refrigeration system according to claim 3, characterized in that, There are multiple said end evaporators, including a cooling fan (3) and a pipe coil (4). The outlet ends of the air outlet pipes of the cooling fans (3) are each connected to an oil return branch pipe and a gas return branch pipe through a tee. The relatively arranged ports in the tee are horizontally arranged and are respectively connected to the air outlet pipe of the cooling fan (3) and the gas return branch pipe. The other port in the tee is vertically downward and is connected to the oil return branch pipe. The air outlet pipe of the pipe coil is an exhaust manifold of the pipe coil. An opening is made at the bottom side wall of the exhaust manifold of the pipe coil, and the oil return branch pipe is connected to the exhaust manifold of the pipe coil through the opening. The side of the oil return branch pipe close to the exhaust manifold of the pipe coil is perpendicular to the exhaust manifold of the pipe coil and extends vertically downward, and the side of the gas return branch pipe close to the exhaust manifold of the pipe coil extends vertically upward.

9. The end oil return system of a refrigeration system according to claim 1 or 2, characterized in that The system further includes a heat exchanger (5). The refrigerant inlet of the heat exchanger (5) is connected to the outlet of the oil collecting tank (6) through a heat exchange inlet oil pipe (63). The refrigerant outlet of the heat exchanger (5) is connected to the lubricating oil inlet or the refrigerant inlet of the compressor unit (1) through a suction oil return pipe (12). The heat medium inlet of the heat exchanger (5) is connected to the high-pressure liquid storage tank of the pump liquid supply system or to the domestic waste heat or waste heat pipeline through a heat supply inlet pipe (14). The heat medium outlet of the heat exchanger (5) is connected to the high-pressure liquid storage tank of the pump liquid supply system or to the domestic waste heat or waste heat pipeline through a heat supply outlet pipe (15).

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