A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting shunt reactors

Abstract

This invention discloses a closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors, relating to liquid nitrogen cooling technology. The device includes a Dewar assembly, a circulation assembly, and a refrigeration assembly. The circulation assembly includes a circulation pipe, on which, along the liquid nitrogen flow direction near the outlet end of the Dewar assembly, are sequentially installed an outlet valve, a pressure gauge before the pump, a liquid nitrogen pump, a pressure gauge after the pump, a vent valve, an electric regulating valve, a liquid nitrogen valve, a temperature sensor, and a pressure gauge after the valve. The refrigeration assembly includes a Stirling refrigerator and a water-cooled unit for dissipating heat from the Stirling refrigerator. This invention, by distributing multiple pressure gauges and valves along the circulation pipe, monitors the temperature and pressure at key measuring points of the superconducting magnet and the refrigeration system in real time, understands the operating status of the monitoring system, and thus achieves automated control operation, effectively improving the working stability and reliability of the superconducting magnet.

Description

Technical Field

[0001] This invention relates to liquid nitrogen cooling equipment, specifically a closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors. Background Technology

[0002] Liquid nitrogen is inexpensive to prepare and has stable chemical and insulating properties, making it a reliable cooling medium for cooling high-temperature superconducting power devices. Therefore, liquid nitrogen is now used as a refrigerant in many countries.

[0003] Liquid nitrogen refrigeration methods are divided into open-loop and closed-loop refrigeration. Compared with open-loop refrigeration, the main advantage of closed-loop refrigeration is its lower operating cost and the avoidance of using relatively large liquid nitrogen storage tanks for daily liquid nitrogen refilling. However, for closed-loop liquid nitrogen refrigeration systems, since they do not require an external cold source and rely on internal refrigeration components for cooling, ensuring stable operation under design conditions and maintaining a highly uniform temperature is crucial. Furthermore, for this type of system, because the inlet and outlet pipes inside the Dewar flask are fixed, large dead zones of stagnant liquid nitrogen can easily form inside the Dewar flask during prolonged circulation of supercooled liquid nitrogen, affecting heat exchange performance. Therefore, improvements are necessary. Summary of the Invention

[0004] The purpose of this invention is to provide a closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors, so as to solve the problem mentioned in the background art of how the prior art can ensure the stable operation of the cooling device under the design conditions.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors includes a Dewar assembly for holding liquid nitrogen, a circulation assembly for driving the liquid nitrogen circulation flow, and a refrigeration assembly for cooling the liquid nitrogen. The Dewar assembly includes a Dewar canister, and the reactor is disposed inside the Dewar canister.

[0007] The circulation assembly includes a circulation pipe for connecting the Dewar assembly and the refrigeration assembly, one end of the circulation pipe being connected to the liquid outlet pipe of the Dewar assembly and the other end of the circulation pipe being connected to the liquid inlet pipe of the Dewar assembly;

[0008] Along the liquid nitrogen flow direction, the circulation pipe near the outlet pipe of the Dewar assembly is sequentially equipped with an outlet valve, a pressure gauge before the pump, a liquid nitrogen pump, a pressure gauge after the pump, a vent valve, an electric regulating valve, a liquid nitrogen valve, a temperature sensor, and a pressure gauge after the valve; an inlet valve is fixedly installed on the circulation pipe near the inlet pipe of the Dewar assembly; the refrigeration assembly includes a Stirling refrigerator and a water-cooled unit for dissipating heat from the Stirling refrigerator.

[0009] As a further aspect of the present invention: the Dewar assembly includes an insulated box, a support platform is fixedly installed on the bottom of the inner wall of the insulated box, a Dewar jar is placed on the support platform, a cover is fixedly installed on the top of the insulated box, an airtight ring is fixedly connected to the edge of the cover, and a lifting ring is fixedly connected to the top of the cover.

[0010] As a further aspect of the present invention: the top edge of the cover is rotatably connected with a number of locking bolts, the top edge of the heat insulation box is provided with a number of bolt holes, and the bottom of the number of locking bolts is threadedly connected to the number of bolt holes respectively.

[0011] As a further aspect of the present invention: a flow-dividing assembly is fixedly installed on the top of the Dewar jar. The flow-dividing assembly includes a flow-dividing cover plate. A central tube is fixedly connected to the top of the flow-dividing cover plate. A mounting ring is rotatably connected to the middle of the central tube. A lower mating gear is fixedly connected to the bottom of the mounting ring. An upper mating gear is fixedly connected to the top of the mounting ring. A mounting frame is fixedly connected above the mounting ring. A drive motor is fixedly connected to one side of the mounting frame. A drive gear is fixedly connected to the output end of the drive motor. The drive gear meshes with the upper mating gear. A plurality of flow-dividing pipes are fixedly connected to the bottom of the central tube. A flow-dividing regulating valve is fixedly connected to the middle of each of the plurality of flow-dividing pipes. An adjusting gear is fixedly connected to the adjusting end of each of the plurality of flow-dividing regulating valves. Each of the plurality of adjusting gears meshes with the lower mating gear.

[0012] As a further aspect of the present invention: the middle part of the liquid inlet pipe is curved, the end of the liquid inlet pipe near the circulation pipe is horizontally set and fixedly connected to the circulation pipe, and the bottom of the liquid inlet pipe is vertically set and fixedly connected to the top of the central pipe.

[0013] As a further aspect of the present invention: a dehumidification component is fixedly installed on one side of the heat insulation box. The dehumidification component includes a housing, an air inlet hood is fixedly connected to the top of the housing, an air outlet hood is fixedly connected to one side of the housing, an air inlet pipe is fixedly connected to the bottom of the air inlet hood, an air inlet pump is fixedly connected to the bottom of the air inlet pipe, an air outlet pipe is fixedly connected to the output end of the air inlet pump, one end of the air outlet pipe is fixedly connected to the air outlet hood, and a water removal filter is fixedly installed in the middle of the air outlet pipe.

[0014] As a further aspect of the present invention: a reversing valve is fixedly installed in the middle of the air inlet pipe, and an exhaust pipe is fixedly connected to one end of the reversing valve, with one end of the exhaust pipe communicating with the inside of the heat insulation box.

[0015] As a further aspect of the present invention: the outer wall of the circulation pipe is covered with a heat insulation pad, and an outer protective sleeve is fixedly connected to the outer wall of the heat insulation pad.

[0016] As a further aspect of the present invention, the operating method of the closed-loop subcooled liquid nitrogen circulation device includes the following steps:

[0017] Step 1: Leak test the Dewar assembly, perform a 0.05MPa airtightness test on the Dewar canister and hold the pressure for 20 minutes; then perform vacuum replacement, use a vacuum pump to evacuate to 0.1Pa, hold the pressure for 30 minutes, then fill with nitrogen to 0.02MPa and hold the pressure for 30 minutes, repeat this process 3 times; finally, add liquid nitrogen.

[0018] Step 2: Leak detection of the circulation pipe. After connecting the circulation assembly, Dewar assembly, and refrigeration assembly, open the liquid outlet valve and use liquid nitrogen flow to check for leaks in the circulation pipe and the entire circulation assembly.

[0019] Step 3: Pre-cooling the circulation pipe. Open the electric regulating valve, the vent valve, and the branch low-temperature solenoid valve inside the Stirling refrigerator in sequence. Then gradually open the liquid outlet valve. At this time, liquid nitrogen will flow into the circulation pipe through the valve. Pre-cool until the temperature sensor displays a temperature of -196℃, indicating that the pre-cooling of the circulation pipe is complete.

[0020] Step 4: Start the refrigeration system. First, turn on the water-cooled unit, then gradually open the vent valve and observe the outlet status of the vent valve. If all the liquid nitrogen is sprayed out in columnar form, the liquid nitrogen pump can be turned on. After the liquid nitrogen pump is running stably, turn on the Stirling refrigeration unit.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: Liquid nitrogen in the Dewar jar flows into the circulation pipe through the outlet valve, and is powered by the liquid nitrogen pump. It is then diverted to the liquefaction chamber of the Stirling refrigerator through the circulation pipe. After being cooled in the liquefaction chamber, the liquid nitrogen reaches a supercooled state and then flows into the Dewar jar through the inlet valve through the circulation pipe, thus forming a circulation and achieving the purpose of supercooling the liquid nitrogen inside the Dewar jar. By distributing multiple pressure gauges and valves on the circulation pipe, the temperature and pressure of each key measuring point of the superconducting magnet and the refrigeration system are monitored in real time to understand the operating status of the monitoring system and thus realize automated control operation, effectively improving the working stability and reliability of the superconducting magnet.

[0022] This invention uses multiple distribution pipes to deliver liquid nitrogen from different locations. By adjusting the flow rate of each distribution pipe with a regulating valve, the liquid nitrogen output from each distribution pipe is changed. This allows the liquid nitrogen inside the Dewar flask to flow slowly under the impetus of the liquid nitrogen delivered from different locations, thus avoiding the formation of dead zones and the problem of liquid nitrogen dead zones inside the Dewar flask caused by liquid nitrogen being delivered from a single location.

[0023] This invention reduces the moisture content of the ambient air in the working area by setting up a dehumidification component, using an air intake pump to draw in outside air, and using a dehumidification filter to filter and remove water vapor from the air, thereby effectively preventing water vapor from condensing on pipeline equipment; by changing the connection direction of the air intake pipe through a reversing valve, the air inside the insulation box is extracted by the exhaust pipe, thus achieving the removal of water vapor inside the insulation box. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the device layout of the present invention;

[0025] Figure 2 This is a perspective view of the Dewar assembly of the present invention;

[0026] Figure 3 This is a schematic diagram showing the installation state of the Dewar flask of the present invention;

[0027] Figure 4 This is a cross-sectional view of the current splitter assembly of the present invention;

[0028] Figure 5 This is a cross-sectional view of the dehumidification component of the present invention;

[0029] Figure 6 This is a cross-sectional view of the circulation pipe of the present invention.

[0030] In the diagram: 1. Dewar assembly; 101. Insulated box; 102. Inlet pipe; 103. Outlet pipe; 104. Cover; 105. Airtight ring; 106. Bolt hole; 107. Lifting ring; 108. Support platform; 2. Stirling refrigerator; 3. Water-cooled unit; 4. Circulation assembly; 41. Outlet valve; 42-1. Pressure gauge before pump; 42-2. Pressure gauge after pump; 42-3. Pressure gauge after valve; 43. Liquid nitrogen pump; 44. Vent valve; 45. Electric regulating valve; 46. Liquid nitrogen valve; 47. Temperature sensor; 48. Inlet valve; 401. Circulation pipe; 402. Isolation... 403. Heating pad; 5. Outer protective sleeve; 6. Dewar canister; 7. Diverter assembly; 8. Diverter hood; 9. Center tube; 10. Diverter pipe; 11. Diverter regulating valve; 12. Adjusting gear; 13. Mounting bracket; 14. Drive motor; 15. Drive gear; 16. Upper mating gear; 17. Lower mating gear; 18. Mounting collar; 19. Dehumidification assembly; 10. Housing; 11. Inlet pump; 12. Inlet hood; 13. Water filter; 14. Outlet hood; 15. Reversing valve; 16. Exhaust pipe; 17. Outlet pipe. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see Figure 1 In this embodiment of the invention, a closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors includes a Dewar assembly 1 for holding liquid nitrogen, a circulation assembly 4 for driving the liquid nitrogen circulation flow, and a refrigeration assembly for cooling the liquid nitrogen. The Dewar assembly 1 includes an insulated box 101, and a Dewar canister 5 is disposed inside the insulated box 101. The reactor is disposed inside the Dewar canister 5. The superconducting parallel reactor targeted in this application includes a glass fiber G10 skeleton and a high-temperature superconducting tape. Conventional hollow superconducting reactors face the problem of magnetic leakage. Although traditional magnetic shielding can suppress spatial magnetic leakage, it will lead to increased reactor operating losses and cause changes in inductance parameters. Therefore, a toroidal reactor structure is selected to reduce magnetic leakage.

[0033] Please see Figure 1 and Figure 2 A liquid inlet pipe 102 is fixedly connected to the top of one side of the insulated box 101, and a liquid outlet pipe 103 is fixedly connected to the bottom of one side of the insulated box 101. The refrigeration components include a Stirling refrigerator 2 and a water-cooled unit 3 for dissipating heat from the Stirling refrigerator 2. Both the Stirling refrigerator 2 and the water-cooled unit 3 are implemented using existing technologies. Liquid nitrogen in the Dewar jar 5 flows into the circulation pipe 401 through the liquid outlet valve 41. The liquid nitrogen pump 43 provides circulation power, and the liquid nitrogen is diverted to the liquefaction chamber of the Stirling refrigerator 2 through the circulation pipe 401. After passing through the liquefaction chamber, the liquid nitrogen is cooled from 77K to 70K, reaching a supercooled state. Then, it flows into the Dewar jar 5 through the liquid inlet valve 48 through the circulation pipe 401, thus forming a circulation and achieving the purpose of supercooling the liquid nitrogen inside the Dewar jar 5. The entire system is connected to an electrical control cabinet, which includes a data acquisition system, a control screen, a communication module, and a safety shutdown system. The signals of the entire system are controlled automatically by the PLC inside the control cabinet, enabling both remote and local control. This allows for precise control of the refrigeration system, ensuring reliable operation and convenient maintenance.

[0034] Please see Figure 2 and Figure 3 The circulation assembly 4 includes a circulation pipe 401 for connecting the Dewar assembly 1 and the refrigeration assembly. The two ends of the circulation pipe 401 are connected to the liquid outlet pipe 103 and the liquid inlet pipe 102, respectively. This is to reduce temperature changes in liquid nitrogen during pipeline transportation, to reduce heat conduction between liquid nitrogen and the external environment during transportation, and to reduce pipeline vibration noise during liquid nitrogen transportation. Please refer to [link to relevant documentation]. Figure 6 The outer wall of the circulation pipe 401 is covered with a heat insulation pad 402, and the outer wall of the heat insulation pad 402 is fixedly connected with an outer protective sleeve 403;

[0035] Please see Figure 1 Along the liquid nitrogen flow direction, the circulation pipe 401 near the outlet pipe 103 of the Dewar assembly 1 is equipped with, in sequence, an outlet valve 41, a pressure gauge 42-1 before the pump, a liquid nitrogen pump 43, a pressure gauge 42-2 after the pump, a vent valve 44, an electric regulating valve 45, a liquid nitrogen valve 46, a temperature sensor 47, and a pressure gauge 42-3 after the valve. The pressure gauges 42-1 before the pump, 42-2 after the pump, and 42-3 after the valve monitor the pressure before the liquid nitrogen pump 43, the pressure after the liquid nitrogen pump 43, and the pressure after the liquid nitrogen valve 46, respectively. The electric regulating valve 45 is used to control the flow rate of circulating liquid nitrogen. The temperature sensor 47 is used to monitor the liquid nitrogen temperature after the electric regulating valve 45. The liquid nitrogen valve 46 is used to prevent excessive pressure in the pipeline.

[0036] A liquid inlet valve 48 is fixedly installed on the side of the circulation pipe 401 near the liquid inlet end of the Dewar assembly 1. By setting pressure gauges and valves at various locations, the temperature and pressure of each key measuring point of the superconducting magnet and the cooling system can be monitored in real time to understand the operating status of the monitoring system. At the same time, high-precision control and automated operation can be achieved, effectively improving the working stability and reliability of the superconducting magnet.

[0037] Please see Figure 3 The bottom of the inner wall of the heat insulation box 101 is fixedly installed with a support platform 108. The top surface of the support platform 108 is recessed downward to form an arc-shaped groove. The Dewar jar 5 is placed in the arc-shaped groove on the support platform 108. The inner wall shape of the arc-shaped groove is consistent with the bottom shape of the Dewar jar 5, so as to achieve stable support for the Dewar jar 5.

[0038] To reduce heat conduction between the Dewar jar 5 and the external environment, a cover 104 is fixedly installed on the top of the insulated box 101. An airtight ring 105 is fixedly connected to the edge of the cover 104 to cover the gap between the cover 104 and the insulated box 101. A lifting ring 107 is fixedly connected to the top of the cover 104 to facilitate opening the cover 104.

[0039] To improve the sealing capability of the cover 104 to the heat insulation box 101, the top edge of the cover 104 is rotatably connected with several locking bolts, and the top edge of the heat insulation box 101 is provided with several bolt holes 106. The bottom of the several locking bolts is threadedly connected to the several bolt holes 106 respectively, so as to avoid reducing internal nitrogen leakage.

[0040] Please see Figure 3 and Figure 4To avoid the problem of liquid nitrogen dead zones inside the Dewar jar 5 caused by liquid nitrogen being supplied from a single location, a flow-dividing assembly 6 is fixedly installed on the top of the Dewar jar 5. The flow-dividing assembly 6 includes a flow-dividing cover plate 601, a central tube 602 is fixedly connected to the top of the flow-dividing cover plate 601, and several flow-dividing pipes 603 are fixedly connected to the bottom of the central tube 602. A flow-dividing regulating valve 604 is fixedly connected to the middle of each of the several flow-dividing pipes 603. This application sets multiple flow-dividing pipes 603 to supply liquid nitrogen from different locations. With the flow-dividing regulating valve 604, the flow rate of each flow-dividing pipe 603 is adjusted, thereby changing the amount of liquid nitrogen supplied from different flow-dividing pipes 603. This allows the liquid nitrogen inside the Dewar jar 5 to flow slowly under the impetus of liquid nitrogen supplied from different locations, thereby avoiding the formation of dead zones.

[0041] To achieve synchronous flow regulation of the three diversion pipes 603 and ensure that the liquid nitrogen supplied by the inlet pipe 102 can enter at a stable flow rate, thereby ensuring the stability of pipeline pressure and liquid nitrogen circulation speed, a mounting collar 611 is rotatably connected to the middle of the central pipe 602. A lower mating gear 610 is fixedly connected to the bottom of the mounting collar 611. Adjusting gears 605 are fixedly connected to the adjusting ends of several diversion regulating valves 604, and all adjusting gears 605 are meshed with the lower mating gear 610. An upper mating gear 609 is fixedly connected to the top of the mounting collar 611. A mounting bracket 606 is fixedly connected above the mounting collar 611. A drive motor 607 is fixedly connected to one side of the mounting bracket 606. A drive gear 608 is fixedly connected to the output end of the drive motor 607, and the drive gear 608 is mated with the upper mating gear 609. Gear 609 meshes and connects; this application sets adjusting gears 605 at the adjusting ends of each diversion regulating valve 604, and drives the adjusting gears 605 to rotate through the drive motor 607 and other structures, so as to synchronously adjust each diversion regulating valve 604. The initial opening state of each diversion regulating valve 604 is different. That is, when some diversion regulating valves 604 gradually open due to the rotation of adjusting gear 605, another part gradually closes due to the rotation of adjusting gear 605. This makes the total liquid nitrogen flow through each diversion pipe 603 consistent with the liquid nitrogen flow delivered by the inlet pipe 102, ensuring the stability of the overall liquid nitrogen circulation flow. That is, the diversion component 6 set in this application only changes the outflow of each diversion pipe 603 individually, so as to guide the flow of liquid nitrogen in the Dewar tank 5 and avoid the formation of dead zones.

[0042] Please see Figure 3The liquid inlet pipe 102 is curved in the middle. The end of the liquid inlet pipe 102 near the circulation pipe 401 is set horizontally and fixedly connected to the circulation pipe 401. The bottom of the liquid inlet pipe 102 is set vertically and fixedly connected to the top of the central pipe 602. By setting the liquid inlet pipe 102 to be curved, the liquid nitrogen flows more smoothly in the pipeline, avoiding the problem of vibration caused by the small-angle bend of the pipeline when the liquid nitrogen flows through, and improving the operational stability of the device.

[0043] In practical use, the entire device is installed in an enclosed indoor working environment. Please refer to [link / reference needed]. Figure 2 and Figure 5 To prevent moisture from condensing on the surface of pipes or other components due to low temperatures during operation, thus affecting the normal performance of the device, this application fixes a dehumidification component 7 on one side of the insulation box 101. The dehumidification component 7 includes a housing 701, an air inlet hood 703 fixedly connected to the top of the housing 701, an air outlet hood 705 fixedly connected to one side of the housing 701, an air inlet pipe fixedly connected to the bottom of the air inlet hood 703, an air inlet pump 702 fixedly connected to the bottom of the air inlet pipe, an air outlet pipe 708 fixedly connected to the output end of the air inlet pump 702, one end of the air outlet pipe 708 fixedly connected to the air outlet hood 705, and a water removal filter 704 fixedly installed in the middle of the air outlet pipe 708. By setting up the water removal component, the air inlet pump 702 draws in outside air, and the water removal filter 704 filters and removes moisture from the air in the enclosed working environment, thereby reducing the moisture content of the ambient air and effectively preventing moisture condensation on the pipes and equipment.

[0044] To filter the moisture inside the insulation box 101, a reversing valve 706 is fixedly installed in the middle of the air inlet pipe. One end of the reversing valve 706 is fixedly connected to an exhaust pipe 707, and one end of the exhaust pipe 707 is connected to the inside of the insulation box 101. By changing the connection direction of the air inlet pipe through the reversing valve 706, the air inside the insulation box 101 is extracted through the exhaust pipe 707, thereby removing the moisture inside the insulation box 101.

[0045] The operation method of this closed-loop subcooled liquid nitrogen circulation device includes the following steps: First, check whether the instruments of each device are normal; after completing the overall encapsulation of the reactor and Dewar 5, the Dewar assembly 1 is leak-tested, specifically: the Dewar 5 is subjected to a 0.05MPa airtightness test and pressure is maintained for 20 minutes; then, a vacuum replacement is performed, using a vacuum pump to evacuate to 0.1Pa, and pressure is maintained for 30 minutes, then nitrogen is added to 0.02MPa and pressure is maintained for 30 minutes, and this process is repeated 3 times; finally, liquid nitrogen is slowly added.

[0046] Next, leak detection is performed on the circulation pipe 401. First, the Dewar assembly 1 is connected to the refrigeration assembly. Specifically, the cap 104 is opened, and the Dewar canister 5, along with its diversion assembly 6, is placed into the insulation box 101 and supported by the support platform 108. Then, the inlet pipe 102 and the outlet pipe 103 are fixedly connected to both ends of the circulation pipe 401. After completion, the cap 104 is installed, and several locking bolts are turned to fix the cap 104 to the insulation box 101. Then, the outlet valve 41 is opened, and liquid nitrogen is used to check for leaks in the circulation pipe 401 and the entire circulation assembly 4. Since the working pressure of the entire system pipeline is low, foam water can be used to check for leaks in the instruments, valve assemblies, and their connection points with the pipeline to ensure that the entire system is leak-free.

[0047] Then, pre-cooling of the circulation pipe 401 is carried out by opening the electric regulating valve 45, the vent valve 44 and the branch low-temperature solenoid valve inside the Stirling refrigerator 2 in sequence, and then gradually and slowly opening the liquid outlet valve 41. At this time, liquid nitrogen will flow into the circulation pipe 401 through the liquid outlet valve 41. Pre-cooling continues until the temperature sensor 47 displays a temperature of -196℃, indicating that the pre-cooling of the circulation pipe 401 has been completed.

[0048] When the equipment is started and running for cooling, first turn on the water-cooled unit 3, then gradually and slowly open the vent valve 44 and observe the outlet status of the vent valve 44. If all the liquid nitrogen is sprayed out in columnar form, then turn on the liquid nitrogen pump 43. Note that the operating frequency of the liquid nitrogen pump 43 needs to be gradually increased from 20Hz to 100Hz. At this time, the pressure gauge 42-3 after the valve shows that the liquid nitrogen pressure at the outlet of the vent valve 44 will rise significantly. At this time, the vent valve 44 needs to be closed. After closing the vent valve 44, observe the pressure gauge 42-1 before the pump and the pressure gauge 42-2 after the pump. Wait for the pressure before and after the liquid nitrogen pump 43 to stabilize. After the liquid nitrogen pump 43 is running stably, turn on the Stirling refrigerator 2. The Stirling refrigerator 2 will continuously cool the liquid nitrogen in the circulation pipe 401 to ensure the stable operation of the superconductor in the Dewar jar 5.

[0049] During the operation of the equipment, the reciprocating rotation of the drive motor 607 drives the rotation of each adjusting gear 605, thereby opening and closing each diversion regulating valve 604, which in turn changes the liquid nitrogen output of each diversion pipe 603, drives the liquid nitrogen flow inside the Dewar tank 5, and avoids the formation of dead zones.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting shunt reactors, characterized in that, It includes a Dewar assembly (1) for holding liquid nitrogen, a circulation assembly (4) for driving the liquid nitrogen circulation flow, and a refrigeration assembly for cooling the liquid nitrogen. The circulation assembly (4) includes a circulation pipe (401) for connecting the Dewar assembly (1) and the refrigeration assembly. The circulation pipe (401) is equipped with an outlet valve (41), a pressure gauge (42-1) before the pump, a liquid nitrogen pump (43), a pressure gauge (42-2) after the pump, a vent valve (44), an electric regulating valve (45), a liquid nitrogen valve (46), a temperature sensor (47), and a pressure gauge (42-3) after the valve along the liquid nitrogen flow direction. An inlet valve (48) is fixedly installed on the circulation pipe (401) near the inlet end of the Dewar assembly (1). The refrigeration assembly includes a Stirling refrigerator (2) and a water-cooled unit (3) for dissipating heat from the Stirling refrigerator (2). The Dewar assembly (1) includes a Dewar canister (5), a flow divider assembly (6) is fixedly installed on the top of the Dewar canister (5), the flow divider assembly (6) includes a flow divider cover (601), a central tube (602) is fixedly connected to the top of the flow divider cover (601), a plurality of flow divider tubes (603) are fixedly connected to the bottom of the central tube (602), and a flow divider regulating valve (604) is fixedly connected to the middle of each of the plurality of flow divider tubes (603); a mounting collar (611) is rotatably connected to the middle of the central tube (602), and the bottom of the mounting collar (611) is... A lower docking gear (610) is fixedly connected to the part, and an adjusting gear (605) is fixedly connected to the adjusting end of a plurality of the diversion regulating valves (604). The plurality of adjusting gears (605) are all meshed with the lower docking gear (610). An upper docking gear (609) is fixedly connected to the top of the mounting collar (611). A drive motor (607) is provided above the mounting collar (611). A drive gear (608) is fixedly connected to the output end of the drive motor (607). The drive gear (608) meshes with the upper docking gear (609). The initial opening states of each diversion regulating valve (604) are different. That is, when some diversion regulating valves (604) gradually open due to the rotation of the regulating gear (605), the other part gradually closes due to the rotation of the regulating gear (605), thereby making the total liquid nitrogen flow through each diversion pipe (603) consistent with the liquid nitrogen flow sent in by the inlet pipe (102), ensuring the stability of the overall liquid nitrogen circulation flow.

2. The closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 1, characterized in that, The Dewar assembly (1) includes an insulated box (101), a support platform (108) is fixedly installed on the bottom of the inner wall of the insulated box (101), the Dewar canister (5) is placed on the support platform (108), a cover (104) is fixedly installed on the top of the insulated box (101), and an airtight ring (105) is fixedly connected to the edge of the cover (104).

3. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 2, characterized in that, The top edge of the cover (104) is rotatably connected with several locking bolts, and the top edge of the heat insulation box (101) is provided with several bolt holes (106), and the bottom of the several locking bolts is threadedly connected to the several bolt holes (106).

4. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 2, characterized in that, A liquid inlet pipe (102) is fixedly connected to the top of one side of the heat insulation box (101). The liquid inlet pipe (102) is curved in the middle. The end of the liquid inlet pipe (102) near the circulation pipe (401) is set horizontally and fixedly connected to the circulation pipe (401). The bottom of the liquid inlet pipe (102) is set vertically and fixedly connected to the top of the central pipe (602).

5. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 2, characterized in that, A dehumidification assembly (7) is fixedly installed on one side of the heat insulation box (101). The dehumidification assembly (7) includes a housing (701). An air inlet hood (703) is fixedly connected to the top of the housing (701). An air outlet hood (705) is fixedly connected to one side of the housing (701). An air inlet pipe is fixedly connected to the bottom of the air inlet hood (703). An air inlet pump (702) is fixedly connected to the bottom of the air inlet pipe. An air outlet pipe (708) is fixedly connected to the output end of the air inlet pump (702). One end of the air outlet pipe (708) is fixedly connected to the air outlet hood (705). A water removal filter (704) is fixedly installed in the middle of the air outlet pipe (708).

6. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 5, characterized in that, A reversing valve (706) is fixedly installed in the middle of the air inlet pipe. One end of the reversing valve (706) is fixedly connected to an exhaust pipe (707), and one end of the exhaust pipe (707) is connected to the inside of the heat insulation box (101).

7. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 1, characterized in that, The outer wall of the circulation pipe (401) is covered with a heat insulation pad (402), and an outer protective sleeve (403) is fixedly connected to the outer wall of the heat insulation pad (402).

8. A closed-loop subcooled liquid nitrogen circulation device suitable for superconducting parallel reactors according to claim 1, characterized in that, The operation of this closed-loop subcooled liquid nitrogen circulation device includes the following steps: Step 1: Leak test the Dewar assembly (1), perform a 0.05MPa airtightness test on the Dewar canister (5) and hold the pressure for 20 minutes; then perform vacuum replacement, use a vacuum pump to evacuate to 0.1Pa, hold the pressure for 30 minutes, then fill with nitrogen to 0.02MPa and hold the pressure for 30 minutes, repeat this process 3 times; finally, add liquid nitrogen. Step 2: Leak detection of circulation pipe (401). After connecting circulation assembly (4), Dewar assembly (1), and refrigeration assembly, open liquid outlet valve (41) and use liquid nitrogen flow to check for leaks in circulation pipe (401) and the entire circulation assembly (4). Step 3: Pre-cooling the circulation pipe (401), open the electric regulating valve (45), the vent valve (44) and the branch low temperature solenoid valve inside the Stirling refrigerator (2) in sequence, and then gradually open the liquid outlet valve (41). At this time, liquid nitrogen will flow into the circulation pipe (401) through the valve; pre-cooling continues until the temperature sensor (47) displays a temperature of -196℃, indicating that the circulation pipe (401) has been pre-cooled. Step 4: Start the refrigeration. First, turn on the water-cooled unit (3), then gradually open the vent valve (44) and observe the outlet status of the vent valve (44). If all the liquid nitrogen is sprayed out in columnar form, then the liquid nitrogen pump (43) can be turned on. After the liquid nitrogen pump (43) is running stably, turn on the Stirling refrigeration unit (2).

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