Liquid nitrogen precooling device for conduction cold superconducting magnet

Abstract

The invention discloses a liquid nitrogen pre-cooling device for a conduction cold superconducting magnet, and relates to the technical field of low-temperature pre-cooling in superconducting magnets. Comprising an integrated flange assembly, a first-stage neck pipe corrugated pipe, a transition neck pipe, a second-stage neck pipe corrugated pipe, a cold seat transition pipe and a pre-cooling circulation assembly which are coaxially sealed and fixed in sequence to form a tubular pre-cooling main body; a liquid conveying sealing seat and an exhaust port assembly are mounted on the integrated flange assembly, and an exhaust pipe and a pluggable liquid conveying pipe in the exhaust port assembly are vertically arranged in the tubular pre-cooling main body in parallel; the pre-cooling circulation assembly comprises a pre-cooling base, a liquid inlet pipe communicating with the liquid conveying pipe and an air outlet pipe communicating with the exhaust pipe, and the end, away from the pre-cooling base, of the liquid inlet pipe communicates with the end, away from the pre-cooling base, of the air outlet pipe to achieve closed-loop type circulation pre-cooling. By means of the pre-cooling cavity sealing circulation structure, the sealing performance and the heat exchange efficiency are enhanced, and meanwhile the vacuum stability is guaranteed; the operation characteristic of low temperature reduction in the conduction cold superconducting magnet is utilized, a liquid nitrogen precooling device is additionally arranged, and the precooling time is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of low-temperature precooling of superconducting magnets, in particular to a liquid nitrogen precooling device for conduction-cooled superconducting magnets. Background Art

[0002] Conventional superconducting magnets generally operate at low temperatures, and the required superconducting material properties form a superconducting state at a specific temperature. The cooling methods of superconducting magnets are mainly divided into two categories: wet immersion cooling and dry conduction cooling. Among them, wet immersion cooling is to place the cold mass of the supermagnet in a low-temperature liquid medium (such as liquid helium) to achieve the target low temperature, while dry conduction cooling is to achieve the cooling of the cold mass magnet through refrigerator technology. At present, the world has shown unprecedented concerns about the supply of helium. According to the current global usage rate, it is expected that the global helium will be exhausted in 2040. The application of dry conduction cooling technology is one of the main means to solve the helium energy problem.

[0003] However, the current dry conduction cooling technology has problems such as low cooling power and long pre-cooling cycle. The purpose of pre-cooling is to speed up the cooling speed and reduce the operation time of the refrigeration system. The traditional refrigerator system pre-cooling technology only relies on the refrigerator to cool the magnet cold mass, which requires a long pre-cooling cycle and high pre-cooling cost. Secondly, the traditional single-stage circulation pipe cooling needs to ensure the sealing of the circulation pipe and the vacuum stability of the entire magnet. To this end, we provide a liquid nitrogen pre-cooling device for conduction-cooled superconducting magnets. Summary of the invention

[0004] The purpose of the present invention is to provide a liquid nitrogen precooling device for a conduction-cooled superconducting magnet. The liquid nitrogen precooling device for a conduction-cooled superconducting magnet used in the present invention forms an independent sealed cavity to achieve improved sealing and precooling efficiency during liquid nitrogen precooling.

[0005] The technical problems solved by the present invention are:

[0006] (1) The prior art pre-cooling technology only uses refrigerants to cool the magnets, which results in a long cooling cycle and high cost;

[0007] (2) The existing technology has problems with the single-machine circulation pipe cooling's poor sealing and vacuum stability.

[0008] The present invention can be implemented by the following technical scheme: a liquid nitrogen precooling device for a conduction-cooled superconducting magnet, comprising an integrated flange assembly, a primary neck tube bellows, a transition neck tube, a secondary neck tube bellows, a cold seat transition tube and a precooling circulation assembly, which are coaxially sealed and fixed vertically downward in sequence, to form a tubular precooling body; an infusion sealing seat and an exhaust port assembly are installed on the integrated flange assembly, an exhaust pipe in the exhaust port assembly and a pluggable infusion pipe are vertically and parallelly arranged in the tubular precooling body, the tops of the exhaust pipe and the infusion pipe both pass through the integrated flange assembly, and the bottoms of both extend to the precooling circulation assembly;

[0009] The precooling circulation component includes a precooling seat, a liquid inlet pipe connected to the liquid infusion pipe, and an air outlet pipe connected to the exhaust pipe, and the ends of the liquid inlet pipe and the air outlet pipe away from the precooling seat are connected to realize closed-loop circulation precooling.

[0010] A further technical improvement of the present invention is that a transition thermal cutoff is fixedly installed on the outer side of the transition neck tube, and the transition thermal cutoff is connected to the external cold shield.

[0011] A further technical improvement of the present invention is that the transition heat cutoff is located at the first equal division point of the three equal division points of the entire precooling device close to the normal temperature end, and the position close to the top end of the entire precooling device is the normal temperature end.

[0012] A further technical improvement of the present invention is that the integrated flange assembly includes an integrated flange fixed to the top of the first-level neck tube bellows, an infusion guide tube is fixedly installed at the bottom of the integrated flange, the infusion guide tube is coaxially arranged with the infusion sealing seat, and the infusion tube can be plugged and unplugged in the infusion guide tube.

[0013] A further technical improvement of the present invention is that the infusion sealing seat comprises a sealing socket penetrating the integrated flange, a sealing sleeve is coaxially arranged inside the sealing socket, and the relative position of the sealing sleeve and the sealing socket is fixed by a plug nut sleeved on the outside of the sealing sleeve.

[0014] A further technical improvement of the present invention is that the sealing sleeve includes two structural forms: an open sealing sleeve and a self-sealing sealing sleeve. When the infusion tube is inserted into the infusion guide tube, the sealing sleeve adopts the open sealing sleeve structure. When the infusion tube is pulled out of the infusion guide tube, the sealing sleeve adopts the self-sealing sealing sleeve structure.

[0015] A further technical improvement of the present invention is that a sealing clamp and an exhaust ball valve are installed on the outer side of one end of the exhaust pipe that passes through the integrated flange to control the gas exhaust speed and cavity pressure.

[0016] A further technical improvement of the present invention is that two vertical connecting holes are opened at the top of the pre-cooling circulation component, the bottom end of the infusion tube is sealed with the side wall of the vertical connecting hole by a Teflon sealing gasket, and the top of the vertical connecting hole connected to the infusion tube is provided with a guide groove for smooth docking of the infusion tube.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention increases the sealing performance of the circulation pipeline and the heat exchange efficiency of the magnet cold mass through the pre-cooling cavity sealing circulation structure, while ensuring the vacuum stability of the entire magnet.

[0019] 2. The present invention utilizes the low-temperature cooling operating characteristics of the conduction-cooled superconducting magnet, replacing the traditional conduction-cooled superconducting magnet's long-term cooling method through a refrigerator, adding a liquid nitrogen precooling device, reducing the overall superconducting magnet precooling time, and improving the overall superconducting magnet precooling control working performance.

[0020] 3. The present invention uses transition heat cutoff to improve the primary and secondary heat leakage distribution of the overall precooling device and reduce the conductive heat leakage of the entire device.

[0021] 4. The present invention uses two neck tube bellows to compensate for the installation volume and the structural stress caused by cold shrinkage, while lengthening the effective heat transfer distance from the high-temperature end to the thermal cutoff and from the thermal cutoff to the low-temperature end, thereby reducing heat leakage of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0023] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

[0024] Figure 2 It is a schematic diagram of the 1 / 2 cross-sectional structure of the present invention;

[0025] Figure 3 It is a cross-sectional schematic diagram of the open structure of the infusion sealing seat of the present invention;

[0026] Figure 4 It is a schematic cross-sectional view of the self-sealing structure of the infusion sealing seat of the present invention;.

[0027] In the figure: 1. infusion tube; 2. infusion sealing seat; 3. integrated flange assembly; 4. primary neck tube bellows; 5. transition neck tube; 6. transition heat cutoff; 7. secondary neck tube bellows; 8. cold seat transition tube; 9. pre-cooling circulation assembly; 10. Teflon sealing gasket; 11. exhaust port assembly; 12. Dewar interface; 13. cold screen interface; 14. cold mass interface; 201. plug nut; 202. O-ring; 203. sealing sleeve; 2031. open sealing sleeve; 2032. self-sealing sealing sleeve; 204. sealing socket; 301. integrated flange; 302. infusion guide tube; 901. liquid inlet tube; 902. air outlet pipe; 903. pre-cooling seat; 1101. exhaust ball valve; 1102. sealing clamp; 1103. exhaust pipe. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0029] See also Figure 1-4 As shown, a liquid nitrogen precooling device for a conduction-cooled superconducting magnet comprises a primary neck tube bellows 4, a transition neck tube 5, and a secondary neck tube bellows 7 which are coaxially arranged in sequence from top to bottom, the top and the bottom of the transition neck tube 5 are respectively fixedly connected to the primary neck tube bellows 4 and the secondary neck tube bellows 7 by welding, the bottom of the secondary neck tube bellows 7 is coaxially fixedly connected to a cold seat transition tube 8, and the bottom of the cold seat transition tube 8 is brazed to a precooling circulation assembly 9 to form a precooling main structure;

[0030] The outer side of the transition neck tube 5 is brazed with a transition heat cutoff 6 for transitioning from normal temperature to low temperature, and the transition heat cutoff 6 is connected to an external cold screen; the specific position of the transition heat cutoff 6 is located at a position that divides the entire precooling device into three equal parts and is one equal division point away from the room temperature end, in other words, at a position two equal division points away from the low temperature section, so as to facilitate the primary and secondary heat leakage distribution of the overall precooling device.

[0031] It should be noted that the transition heat cutoff 6 is used for temperature cutoff from room temperature to low temperature. According to Fourier's law, its equivalent heat transfer heat is related to the temperature gradient from the high temperature end to the low temperature end, the cross-sectional area and length of the object and the thermal conductivity of the material. In order to effectively cut off the heat from the high temperature zone to the low temperature end, a heat cutoff is added in the middle for isolation, so as to realize heat transfer from the high temperature end to the heat cutoff and from the heat cutoff to the low temperature end, thereby reducing the system conduction heat leakage.

[0032] The two neck tube bellows connected at the top and bottom of the transition neck tube 5 have three functions: ① to compensate the installation amount during the installation process of the pre-cooling structure to facilitate the adjustment of the axial spacing; ② to lengthen the effective heat transfer distance from the high-temperature end to the thermal cutoff and from the thermal cutoff to the low-temperature end to reduce the heat leakage of the system; ③ to utilize the flexible characteristics of the bellows to avoid excessive stress caused by cold contraction when the device is running at low temperature, which may cause damage to the structure.

[0033] The top of the primary neck tube bellows 4 is sealed and fixedly connected with an integrated flange assembly 3, which includes an integrated flange 301 and an infusion guide tube 302, wherein an infusion seal seat 2 and an exhaust port assembly 11 are arranged on the top of the integrated flange 301, the infusion guide tube 302 is vertically fixed to the bottom of the integrated flange 301 and is coaxially arranged with the infusion seal seat 2, and the pluggable infusion tube 1 passes through the infusion seal seat 2 and extends downward inside the infusion seal seat 2 under the guidance of the infusion guide tube 302 to the precooling circulation assembly 9;

[0034] The infusion sealing seat 2 includes a sealing socket 204 penetrating the integrated flange 301, a sealing sleeve 203 is provided in the sealing socket 204 through an O-ring 202 coaxially with the sealing sleeve, and the sealing sleeve 203 is fixed relative to the sealing socket 204 by a plug nut 201 sleeved on the outside, and the plug nut 201 is threadedly connected to the top outer side of the sealing socket 204;

[0035] Furthermore, the sealing sleeve 203 includes two structural forms, namely, an open sealing sleeve 2031 and a self-sealing sealing sleeve 2032, which are used to achieve compatibility with or without the infusion tube 1; when the infusion tube 1 is inserted into the infusion guide tube 302, the sealing sleeve 203 adopts the open sealing sleeve 2031 structural form; when the infusion tube 1 is pulled out of the infusion guide tube 302, the sealing sleeve 203 adopts the self-sealing sealing sleeve 2032 structural form, ensuring that the cavity is sealed after the infusion tube 1 is removed after infusion;

[0036] The exhaust port assembly 11 includes an exhaust pipe 1103 which is arranged in parallel with the infusion guide tube 302 and extends vertically downward. A sealing clamp 1102 and an exhaust ball valve 1101 are installed on the outer side of one end of the exhaust pipe 1103 which passes through the integrated flange 301 .

[0037] The precooling circulation component 9 includes a precooling seat 903 as a connecting body, and two vertical connecting holes are provided at the top of the bottom of the precooling seat 903. The ends of the infusion tube 1 and the exhaust pipe 1103 are connected and arranged in the two vertical connecting holes, and the bottom end of the infusion tube 1 is sealed with the side wall of the vertical connecting hole by a Teflon sealing gasket 10. A guide groove is provided on the top of the vertical connecting hole connected to the infusion tube 1 to facilitate smooth docking of the infusion tube 1 during installation. A liquid inlet pipe 901 is provided on one side of the bottom, and an air outlet pipe 902 is provided on one side of the bottom of the vertical connecting hole connected to the exhaust pipe 1103. The liquid inlet pipe 901 and the air outlet pipe 902 are connected to each other at one end away from the precooling seat 903, thereby realizing closed-loop circulation precooling. Liquid nitrogen enters from the liquid inlet pipe 901, forms a gas-liquid two-phase state after heat exchange with the magnet cold mass, and is discharged through the air outlet pipe 902. The exhaust ball valve 1101 can control gas discharge and cavity pressure.

[0038] When the present invention is in use, if the infusion tube 1 is inserted into the infusion guide tube 302 and extends into the pre-cooling circulation component 9, the liquid nitrogen enters the vertical connecting hole through the infusion tube 1 and then flows into the liquid inlet tube 901. After the heat exchange of the magnet cold mass, the liquid nitrogen evaporates and absorbs heat to become a gas-liquid two-phase state, and then is discharged from the gas outlet pipe 902 through the exhaust pipe 1103. The exhaust ball valve 1101 controls the gas discharge speed and the pressure of the entire pipeline cavity; after the liquid nitrogen is injected, the infusion tube 1 is withdrawn from the infusion guide tube 302, and the open sealing sleeve 2031 is replaced by the self-sealing sealing sleeve 2032 to ensure that the cavity is sealed after the infusion tube 1 is withdrawn after the infusion; during the pre-cooling process, the presence of the transition heat cutoff 6 reduces the conduction heat leakage of the device.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A liquid nitrogen precooling device for a conduction-cooled superconducting magnet, characterized in that: It comprises an integrated flange assembly (3), a primary neck tube bellows (4), a transition neck tube (5), a secondary neck tube bellows (7), a cold seat transition tube (8) and a pre-cooling circulation assembly (9) which are coaxially sealed and fixed vertically downward in sequence, forming a tubular pre-cooling body; an infusion sealing seat (2) and an exhaust port assembly (11) are installed on the integrated flange assembly (3); an exhaust pipe (1103) in the exhaust port assembly (11) and a pluggable infusion tube (1) are vertically and parallelly arranged in the tubular pre-cooling body; the tops of the exhaust pipe (1103) and the infusion tube (1) both pass through the integrated flange assembly (3), and the bottoms of both extend to the pre-cooling circulation assembly (9); The precooling circulation component (9) comprises a precooling seat (903), a liquid inlet pipe (901) connected to the liquid infusion pipe (1), and an air outlet pipe (902) connected to the exhaust pipe (1103), and the ends of the liquid inlet pipe (901) and the air outlet pipe (902) away from the precooling seat (903) are connected to realize closed-loop circulation precooling.

2. A liquid nitrogen precooling device for conduction-cooled superconducting magnets according to claim 1, characterized in that: A transition thermal cutoff (6) is fixedly mounted on the outer side of the transition neck tube (5), and the transition thermal cutoff (6) is connected to an external cold shield.

3. A liquid nitrogen precooling device for conduction-cooled superconducting magnets according to claim 2, characterized in that: The transition heat cutoff (6) is located at the first equal-division point of the three equal-division points of the entire precooling device close to the normal temperature end, and the position close to the top end of the entire precooling device is the normal temperature end.

4. The liquid nitrogen precooling device for conduction-cooled superconducting magnet according to claim 1, characterized in that: The integrated flange assembly (3) comprises an integrated flange (301) fixed to the top of the first-level neck tube bellows (4); an infusion guide tube (302) is fixedly installed at the bottom of the integrated flange (301); the infusion guide tube (302) is coaxially arranged with the infusion sealing seat (2); and the infusion tube (1) is pluggable and arranged in the infusion guide tube (302).

5. The liquid nitrogen precooling device for conduction-cooled superconducting magnet according to claim 4, characterized in that: The infusion sealing seat (2) comprises a sealing socket (204) penetrating the integrated flange (301), a sealing sleeve (203) is coaxially arranged inside the sealing socket (204), and the relative position of the sealing sleeve (203) and the sealing socket (204) is fixed by a plug nut (201) sleeved on the outside of the sealing sleeve (203).

6. The liquid nitrogen precooling device for conduction-cooled superconducting magnets according to claim 5, characterized in that: The sealing sleeve (203) comprises two structural forms: an open sealing sleeve (2031) and a self-sealing sealing sleeve (2032); when the infusion tube (1) is inserted into the infusion guide tube (302), the sealing sleeve (203) adopts the open sealing sleeve (2031) structural form; when the infusion tube (1) is pulled out of the infusion guide tube (302), the sealing sleeve (203) adopts the self-sealing sealing sleeve (2032) structural form.

7. The liquid nitrogen precooling device for conduction-cooled superconducting magnet according to claim 1, characterized in that: A sealing clamp (1102) and an exhaust ball valve (1101) are installed on the outer side of one end of the exhaust pipe (1103) that passes through the integrated flange (301) to control the gas exhaust speed and cavity pressure.

8. The liquid nitrogen precooling device for conduction-cooled superconducting magnets according to claim 1, characterized in that: The precooling circulation component (9) has two vertical connecting holes at the top, the bottom end of the infusion tube (1) is sealed with the side wall of the vertical connecting hole via a Teflon sealing gasket (10), and the top of the vertical connecting hole connected with the infusion tube (1) is provided with a guide groove for facilitating smooth docking of the infusion tube (1).

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