A fully automatic oil return system for the cryogenic stage of a carbon dioxide cascade refrigeration system

Abstract

This utility model belongs to the field of large-scale cold storage refrigeration technology, specifically relating to a fully automatic oil return system for the low-temperature stage of a carbon dioxide cascade refrigeration system. It includes a gas-liquid separator, with an inlet pipe (II), an exhaust pipe (IV), and a drain pipe (I). A carbon dioxide shielded pump is installed on the drain pipe (I). A drain pipe (II) is installed and connected to the end of the drain pipe (I). An oil return pipe (I) is installed and connected to the outer periphery of the drain pipe (II). A gas return pipe (I) is installed and connected between the carbon dioxide shielded pump and the gas-liquid separator. An oil return valve assembly is installed on the oil return pipe (I). A plate heat exchanger is detachably connected and connected to the end of the oil return pipe (I). A carbon dioxide compressor module is detachably connected and connected to the plate heat exchanger. Compared to existing technologies, this utility model reduces energy loss in subsequent refrigeration stages, achieves fully automatic control of the oil return process, eliminates the need for manual operation, reduces labor costs, and avoids human error.

Description

Technical Field

[0001] This utility model belongs to the field of large-scale cold storage refrigeration technology, specifically relating to a low-temperature stage fully automatic oil return system for a carbon dioxide cascade refrigeration system. Background Technology

[0002] Currently, carbon dioxide cascade refrigeration systems are widely used due to their environmental friendliness and high efficiency. In this system, oil balance is crucial. Traditional oil return systems often employ a three-point return system, which struggles to automatically capture rich oil layers, often requiring manual intervention and increasing labor costs. Furthermore, the high viscosity and poor fluidity of lubricating oil at low temperatures make it difficult to ensure reliable oil return even with the small pressure difference between the compressor and the pump. Additionally, the mixture of refrigerant and lubricating oil in this system can easily lead to excessive refrigerant entering the compressor, causing liquid slugging and shortening the equipment's lifespan. Utility Model Content

[0003] To address the aforementioned problems, this invention provides a fully automatic oil return system for the low-temperature stage of a carbon dioxide cascade refrigeration system.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a fully automatic oil return system for the low-temperature stage of a carbon dioxide cascade refrigeration system, comprising a gas-liquid separator, wherein the gas-liquid separator is equipped with and connected to an inlet pipe two, an exhaust pipe four, and a drain pipe one, wherein a carbon dioxide shielded pump is installed on the drain pipe one, wherein a drain pipe two is installed and connected to the end of the drain pipe one, wherein an oil return pipe one is installed and connected to the outer periphery of the drain pipe two, wherein a gas return pipe one is installed and connected between the carbon dioxide shielded pump and the gas-liquid separator, wherein an oil return valve group is installed on the oil return pipe one, wherein a plate heat exchanger is detachably connected and connected to the end of the oil return pipe one, and wherein a carbon dioxide compressor module is detachably connected and connected to the plate heat exchanger.

[0005] Preferably, the carbon dioxide compressor module includes an oil separator and a carbon dioxide compressor assembly. A second oil return pipe and a first exhaust pipe are installed and connected between the oil separator and the carbon dioxide compressor assembly. The second exhaust pipe is installed and connected to the outer periphery of the oil separator. The second exhaust pipe is detachably connected and connected to a plate heat exchanger. A third exhaust pipe is installed and connected inside the plate heat exchanger. A third oil return pipe is installed and connected inside the plate heat exchanger. An intake pipe is detachably connected and connected to the end of the third oil return pipe. The first intake pipe is detachably connected and connected to the carbon dioxide compressor assembly.

[0006] Preferably, the return oil valve assembly includes a stop valve one and a stop valve two, both of which are installed on the return oil pipe one. A filter, a sight glass, and an electronic expansion valve are sequentially installed on the return oil pipe one from the stop valve one to the stop valve two. A pressure sensor, a temperature sensor, and valve one are installed on the return oil pipe three.

[0007] Preferably, the carbon dioxide compressor assembly includes multiple carbon dioxide compressors, each of which has an oil return branch pipe, an intake branch pipe, and an exhaust branch pipe installed and connected inside. The end of the oil return branch pipe is detachably connected to and connected to an oil return pipe, the end of the intake branch pipe is detachably connected to and connected to an intake pipe, and the end of the exhaust branch pipe is detachably connected to and connected to an exhaust pipe.

[0008] Preferably, valve 2 is installed on the oil return branch pipe, air intake branch pipe and exhaust branch pipe.

[0009] Preferably, the gas-liquid separator is equipped with an air intake mechanism, and valves are installed on both the second air intake pipe and the fourth exhaust pipe.

[0010] Preferably, valve four is installed on both the exhaust pipe three and the intake pipe one. The end of the exhaust pipe three is detachably connected to and communicates with the end of the intake pipe two, and the end of the intake pipe one is detachably connected to and communicates with the end of the exhaust pipe four.

[0011] Preferably, a valve is installed between the end of the drain pipe away from the carbon dioxide shielded pump and the return oil pipe.

[0012] Preferably, the pressure sensor is externally connected to a controller, and the temperature sensor, shut-off valve one, shut-off valve two, and electronic expansion valve are all communicatively connected to the controller.

[0013] Compared with the prior art, the advantages and positive effects of this utility model are as follows:

[0014] (1) Existing traditional oil return systems mostly use three-point oil return systems, while this utility model uses a plate heat exchanger to exchange the low-temperature mixed medium transported by the oil return pipe with the high-temperature gaseous carbon dioxide discharged from the carbon dioxide compressor module: the low-temperature medium absorbs heat and evaporates, and the high-temperature gaseous carbon dioxide is cooled. This process realizes the evaporation cycle of the refrigerant and pre-cools the high-temperature gas, reducing the energy loss of the subsequent refrigeration links and improving the energy utilization efficiency of the entire cascade refrigeration system.

[0015] (2) By linking the controller with the pressure sensor, temperature sensor, electronic expansion valve, and shut-off valve one and shut-off valve two, the return oil process can be fully automatically controlled, eliminating the need for manual operation, reducing labor costs, and avoiding human error.

[0016] (3) Plate heat exchangers use the difference in boiling points between refrigerant and lubricating oil to achieve separation, ensuring a stable oil-to-liquid ratio in the medium entering the carbon dioxide compressor. At the same time, by controlling the superheat, excessive refrigerant liquid is prevented from entering the carbon dioxide compressor, fundamentally preventing liquid slugging in the carbon dioxide compressor and significantly extending the service life of the equipment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below:

[0018] Figure 1 This is a front view of the fully automatic oil return system for the cryogenic stage of the carbon dioxide cascade refrigeration system provided in Example 1.

[0019] Figure 2 for Figure 1 Enlarged view of point A;

[0020] Figure 3 for Figure 1 Enlarged view of point B;

[0021] Figure 4 for Figure 1 Enlarged view of point C;

[0022] Figure 5 for Figure 1 Enlarged view of point D.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1. Gas-liquid separator; 2. Carbon dioxide shielded pump; 3. Return gas pipe 1; 4. Drain pipe 2; 5. Return oil pipe 1; 6. Return oil valve assembly; 7. Carbon dioxide compressor; 8. Oil-liquid separator; 9. Return oil pipe 2; 10. Exhaust pipe 1; 11. Exhaust pipe 2; 12. Exhaust pipe 3; 13. Inlet pipe 1; 14. Return oil pipe 3; 15. Plate heat exchanger; 16. Inlet pipe 2; 17. Exhaust pipe 4; 18. Inlet mechanism; 19. Shut-off valve 1; 20. Filter; 21. Sight glass; 22. Electronic expansion valve; 23. Shut-off valve 2; 24. Pressure sensor; 25. Temperature sensor; 26. Inlet branch pipe; 27. Return oil branch pipe; 28. Exhaust branch pipe. Detailed Implementation

[0025] To better understand the above-mentioned objectives, features and advantages of this utility model, the present utility model will be further described below in conjunction with the accompanying drawings and embodiments.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed in the following specification.

[0027] Example 1

[0028] The following is in conjunction with the appendix Figure 1-5 To further describe this utility model, a fully automatic oil return system for the low-temperature stage of a carbon dioxide cascade refrigeration system, such as... Figure 1 As shown, it includes a gas-liquid separator 1, which is equipped with and connected to an inlet pipe 2 16, an exhaust pipe 4 17, and a drain pipe 1. A carbon dioxide shielded pump 2 is installed on the drain pipe 1, and a drain pipe 2 4 is installed and connected to the end of the drain pipe 1. A return oil pipe 1 5 is installed and connected to the outer periphery of the drain pipe 2 4. A return gas pipe 3 is installed and connected between the carbon dioxide shielded pump 2 and the gas-liquid separator 1. A return oil valve group 6 is installed on the return oil pipe 1 5, and a plate heat exchanger 20 is detachably connected and connected to the end of the return oil pipe 1 5. A carbon dioxide compressor module is detachably connected and connected to the plate heat exchanger 20.

[0029] like Figure 1 As shown, the carbon dioxide compressor module includes an oil separator 8 and a carbon dioxide compressor assembly. A return oil pipe 2 9 and an exhaust pipe 10 are installed and connected between the oil separator 8 and the carbon dioxide compressor assembly. An exhaust pipe 2 11 is installed and connected to the outer periphery of the oil separator 8. The exhaust pipe 2 11 is detachably connected to and connected to the plate heat exchanger 20. An exhaust pipe 3 12 is installed and connected inside the plate heat exchanger 20. A return oil pipe 3 14 is installed and connected inside the plate heat exchanger 20. An intake pipe 13 is detachably connected and connected to the end of the return oil pipe 3 14. The intake pipe 13 is detachably connected and connected to the carbon dioxide compressor assembly.

[0030] like Figure 1 , Figure 2 and Figure 3 As shown, the return oil valve group 6 includes a first shut-off valve 19 and a second shut-off valve 23. Both the first shut-off valve 19 and the second shut-off valve 23 are installed on the first return oil pipe 5. A filter 20, a sight glass 21 and an electronic expansion valve 22 are installed sequentially on the first return oil pipe 5 from the first shut-off valve 19 to the second shut-off valve 23. A pressure sensor 24, a temperature sensor 25 and a valve are installed on the third return oil pipe 14.

[0031] like Figure 1 , Figure 4 and Figure 5As shown, the carbon dioxide compressor assembly includes multiple carbon dioxide compressors 7. Each of the multiple carbon dioxide compressors 7 has an oil return branch pipe 27, an intake branch pipe 26, and an exhaust branch pipe 28 installed and connected inside. The end of the oil return branch pipe 27 is detachably connected to and connected to the second oil return pipe 9. The end of the intake branch pipe 26 is detachably connected to and connected to the first intake pipe 13. The end of the exhaust branch pipe 28 is detachably connected to and connected to the first exhaust pipe 10.

[0032] like Figure 1 , Figure 4 and Figure 5 As shown, valve 2 is installed on the oil return branch pipe 27, the air intake branch pipe 26, and the exhaust branch pipe 28.

[0033] like Figure 1 As shown, an air intake mechanism 18 is installed and connected inside the gas-liquid separator 1, and valves 3 are installed on both the second air intake pipe 16 and the fourth exhaust pipe 17.

[0034] like Figure 1 As shown, valve 4 is installed on both exhaust pipe 3 12 and intake pipe 1 13. The end of exhaust pipe 3 12 is detachably connected to the end of intake pipe 2 16 and is connected to it. The end of intake pipe 1 13 is detachably connected to the end of exhaust pipe 4 17 and is connected to it.

[0035] like Figure 1 As shown, valve 5 is installed between the end of drain pipe 4 away from carbon dioxide shielded pump 2 and return oil pipe 5.

[0036] In this invention, the pressure sensor 24 is externally connected to a controller, and the temperature sensor 25, shut-off valve 19, shut-off valve 23 and electronic expansion valve 22 are all communicatively connected to the controller.

[0037] In this utility model, valve one, valve two, valve three, valve four and valve five are also connected in communication with the controller.

[0038] The working principle of this utility model is as follows: The gas-liquid separator 1 receives the mixed medium from the outside through the air intake mechanism 18. After internal separation, the liquid carbon dioxide enters the carbon dioxide shielded pump 2 through the drain pipe 1. The head of the carbon dioxide shielded pump 2 provides a pressure difference to supply the mixed liquid of carbon dioxide refrigerant and lubricating oil to the return oil pipe 1 5. The mixed liquid of carbon dioxide refrigerant and lubricating oil entering the plate heat exchanger 20 exchanges heat with the high temperature gaseous carbon dioxide from the carbon dioxide compressor module (transported through the exhaust pipe 2 11). The carbon dioxide refrigerant absorbs heat and evaporates into carbon dioxide gaseous refrigerant. Due to the difference in boiling points, the lubricating oil and refrigerant are separated. At the same time, the high temperature gaseous carbon dioxide in the exhaust pipe 2 11 is cooled, which improves the efficiency of the refrigeration system. The carbon dioxide working fluid after heat exchange is divided into two paths: the gaseous part enters the intake pipe 2 16 through the exhaust pipe 3 12 and flows back to the gas-liquid separator 1; the other part enters the intake pipe 1 13 through the return oil pipe 3 14 and is finally sucked into the carbon dioxide compressor assembly.

[0039] In this invention, the oil on the low-temperature side enters the return oil pipe 5 along with the carbon dioxide working fluid, and enters the plate heat exchanger 20 after being regulated by the return oil valve group 6. The filter 20 in the return oil valve group 6 can intercept impurities, and the sight glass 21 facilitates observation of the oil flow status. The electronic expansion valve 22 automatically adjusts the flow rate according to the feedback signals from the pressure sensor 24 and the temperature sensor 25, and works with the shut-off valve 19 and the shut-off valve 23 to realize the on / off control of the oil circuit (automatic control by the controller).

[0040] In this invention, the temperature and pressure parameters in the oil return pipe 14 are detected by the pressure sensor 24 and the temperature sensor 25 and transmitted to the controller. The controller compares the superheat value with the set value. If the calculated superheat value is greater than or equal to the set value, the opening degree of the oil return valve group 6 is increased. If the calculated superheat value is less than the set value, the opening degree of the oil return valve group 6 is decreased. This ensures a quantitative supply of the mixture of refrigerant and lubricating oil, and avoids excessive refrigerant liquid entering the carbon dioxide compressor 7, which could cause liquid slugging in the carbon dioxide compressor 7 and damage the service life of the equipment.

[0041] In this invention, the working principle of the carbon dioxide compressor module is existing technology.

[0042] In this invention, the opening and closing of valves one, two, three, four and five can be controlled by a controller.

[0043] As the technical solution of this utility model, the provided hardware configuration is merely to facilitate the implementation of specific braking control based on the hardware facilities. How to specifically implement braking control and the braking control method are not the technical problems to be solved or the objects of protection of this utility model. Furthermore, the communication methods between the devices all adopt existing communication methods, which are not the focus of this application.

[0044] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model without departing from the technical solution of the present utility model shall still fall within the protection scope of the present utility model.

Claims

1. A full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system, comprising a gas-liquid separator (1), characterized in that, The gas-liquid separator (1) is equipped with and connected to an inlet pipe 2 (16), an exhaust pipe 4 (17) and a drain pipe 1. A carbon dioxide shielded pump (2) is installed on the drain pipe 1. A drain pipe 2 (4) is installed and connected to the end of the drain pipe 1. A return oil pipe 1 (5) is installed and connected to the outer periphery of the drain pipe 2 (4). A return gas pipe 1 (3) is installed and connected between the carbon dioxide shielded pump (2) and the gas-liquid separator (1). A return oil valve group (6) is installed on the return oil pipe 1 (5). A plate heat exchanger (15) is detachably connected and connected to the end of the return oil pipe 1 (5). A carbon dioxide compressor module is detachably connected and connected to the plate heat exchanger (15).

2. The full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system according to claim 1, characterized in that, The carbon dioxide compressor module includes an oil separator (8) and a carbon dioxide compressor assembly. A return oil pipe (9) and an exhaust pipe (10) are installed and connected between the oil separator (8) and the carbon dioxide compressor assembly. An exhaust pipe (11) is installed and connected to the outer periphery of the oil separator (8). The exhaust pipe (11) is detachably connected to and connected to a plate heat exchanger (15). An exhaust pipe (12) is installed and connected inside the plate heat exchanger (15). A return oil pipe (14) is installed and connected inside the plate heat exchanger (15). An intake pipe (13) is detachably connected and connected to the end of the return oil pipe (14). The intake pipe (13) is detachably connected and connected to the carbon dioxide compressor assembly.

3. The fully automatic oil return system for the cryogenic stage of the carbon dioxide cascade refrigeration system according to claim 2, characterized in that, The return oil valve group (6) includes a stop valve one (19) and a stop valve two (23). Both the stop valve one (19) and the stop valve two (23) are installed on the return oil pipe one (5). A filter (20), a sight glass (21) and an electronic expansion valve (22) are installed sequentially on the return oil pipe one (5) from the stop valve one (19) to the stop valve two (23). A pressure sensor (24), a temperature sensor (25) and a valve one are installed on the return oil pipe three (14).

4. The full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system according to claim 3, characterized in that, The carbon dioxide compressor assembly includes multiple carbon dioxide compressors (7). Each of the multiple carbon dioxide compressors (7) has an oil return branch pipe (27), an intake branch pipe (26), and an exhaust branch pipe (28) installed and connected inside. The end of the oil return branch pipe (27) is detachably connected to and connected to the second oil return pipe (9). The end of the intake branch pipe (26) is detachably connected to and connected to the first intake pipe (13). The end of the exhaust branch pipe (28) is detachably connected to and connected to the first exhaust pipe (10).

5. The full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system according to claim 4, characterized in that, Valve II is installed on the oil return branch pipe (27), air intake branch pipe (26) and exhaust branch pipe (28).

6. The full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system according to claim 5, characterized in that, The gas-liquid separator (1) is equipped with an air intake mechanism (18) and is connected to it. Both the second air intake pipe (16) and the fourth exhaust pipe (17) are equipped with valves.

7. The fully automatic oil return system for the cryogenic stage of the carbon dioxide cascade refrigeration system according to claim 6, characterized in that, Valve 4 is installed on both the exhaust pipe 3 (12) and the intake pipe 1 (13). The end of the exhaust pipe 3 (12) is detachably connected to the end of the intake pipe 2 (16) and communicates with it. The end of the intake pipe 1 (13) is detachably connected to the end of the exhaust pipe 4 (17) and communicates with it.

8. The full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system according to claim 7, characterized in that, A valve is installed between the end of the drain pipe away from the carbon dioxide shielded pump (2) and the return oil pipe (5).

9. The full-automatic oil return system for low-temperature stage of carbon dioxide cascade refrigeration system according to claim 3, characterized in that, The pressure sensor (24) is connected to an external controller, and the temperature sensor (25), shut-off valve one (19), shut-off valve two (23) and electronic expansion valve (22) are all connected to the controller in communication.

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