CN116206847A

CN116206847A - Cooling system and superconducting magnet system

Info

Publication number: CN116206847A
Application number: CN202310343344.1A
Authority: CN
Inventors: 吕秉坤; 王维; 信纪军; 梁磐仪; 方志春; 王春栋; 赵婉吟; 李来风
Original assignee: Songshan Lake Materials Laboratory
Current assignee: Songshan Lake Materials Laboratory
Priority date: 2023-04-03
Filing date: 2023-04-03
Publication date: 2023-06-02

Abstract

The invention belongs to the technical field of superconducting magnets, and particularly discloses a cooling system and a superconducting magnet system. The cooling system comprises a vacuum cover, refrigerating machines and first thermal switches, wherein at least two refrigerating machines are arranged, each refrigerating machine is provided with a cold head, the first thermal switches are arranged in one-to-one correspondence with the refrigerating machines, and the cooled load, the cold heads and the first thermal switches are all positioned in the vacuum cover; the first thermal switch comprises a first low-temperature pulsating heat pipe, an evaporation section of the first low-temperature pulsating heat pipe is connected with the cooled load, a condensation section of the first low-temperature pulsating heat pipe is connected with the cold head, and when the cold head is at the final refrigeration temperature, a first working medium in the first low-temperature pulsating heat pipe is in a two-phase flow state. The invention can avoid the heat on the refrigerator from being transferred to the cooled load when the refrigerator stops running or fails, and improve the running safety and reliability of the cooled load.

Description

Cooling system and superconducting magnet system

Technical Field

The invention relates to the technical field of superconducting magnets, in particular to a cooling system and a superconducting magnet system.

Background

The wide application of superconductivity has been indistinguishable from low temperature density, and the superconductivity can be achieved only by cooling the magnet below the superconducting transition temperature, and once the superconducting transition temperature is exceeded, the huge joule heat generated by quench can damage the structure of the superconducting magnet, even cause explosion accidents. The most widely used superconducting magnet at present is a low-temperature superconducting magnet, the superconducting transition temperature of which is very low, for example, nbTi has a superconducting transition temperature of 9.6K, nb ₃ The superconducting transition temperature of Sn is 18.1K, and even a liquid nitrogen temperature zone superconducting magnet called a high temperature superconducting magnet needs to have a superconducting transition temperature of approximately 77K. Therefore, ensuring that superconducting magnets operate stably in a low temperature environment is critical to the application of superconducting technology.

With the development of the technology of a small refrigerator, the application of a superconducting magnet system directly cooled by the refrigerator is more and more extensive, and compared with the traditional low-temperature liquid soaking method, the superconducting magnet system has the advantages of no liquid helium consumption, low cost, small volume, compact structure, easiness in use and maintenance and the like. The typical chiller cooling system includes a chilled load, a radiation protection cold screen, a chiller, a vacuum vessel and other accessories, the radiation protection cold screen is connected to a primary chiller of the chiller, and the chilled load is connected to a secondary chiller. When the cooling system is running, the secondary cold head of the refrigerator reaches the lowest temperature of the closed circulation refrigerator.

In some application scenarios of the superconducting magnet system, such as when applied to space astronomical telescopes, because system maintenance is difficult, a refrigerator redundancy system is usually provided in the refrigeration system, and the service life of the refrigerator unit is prolonged by dividing the operation time between each redundancy refrigerator and reducing the duty cycle of each refrigerator, or when a certain refrigerator fails, the cooled load is ensured to be cooled by the rest of the refrigerators so as to keep normal operation. Therefore, the low-temperature heat switch is positioned between the cooled load and the refrigerator, and when the refrigerator works, the heat switch is conducted, so that the heat resistance is smaller, and the heat load is effectively removed at the design temperature; when the refrigerator stops working or fails, the thermal switch is closed, so that the thermal resistance is larger, the heat transfer path between the refrigerator and the cooled load is blocked, the heat is prevented from flowing from the refrigerator to the load with lower temperature, and the operation of the low-temperature system is not affected.

Low temperature thermal switches typically include mechanical contact thermal switches, superconducting thermal switches, air gap thermal switches, magnetoresistive thermal switches, and the like. The mechanical contact type thermal switch realizes the switching of the state of the thermal switch by utilizing the contact or disconnection of the movable surface, has the advantages of unrestricted working temperature area and complete disconnection, but has the advantages that the thermal conduction is difficult to be higher due to pressure limitation, and an additional driving structure is required to be arranged to drive the thermal switch to move, so that the design difficulty is higher and the occupied space is larger; the principle of the superconducting thermal switch is that the thermal switch is switched by utilizing the difference of the thermal conductivity of superconducting materials in a normal state and a superconducting state, the thermal conductivity coefficient is higher when the thermal switch is conducted, but the thermal switch is only suitable for a temperature region below 0.5K, a magnetic field acting on the superconducting thermal switch needs to be additionally applied, so that the complexity of a system and the cost of the system are increased, meanwhile, the magneto-thermal effect when the magnetic field is applied to the thermal switch also generates heat, and heat leakage exists when the thermal switch is disconnected; the working principle of the air gap type thermal switch is that an adsorbent is placed on one side with lower temperature, when the temperature of the side is lower, the adsorbent adsorbs gas, so that the air pressure of a blade gap is lower, the thermal switch is in an off state, as the temperature of the side is increased, the adsorbent is desorbed, the gas enters the gap, and the thermal switch is in an on state, so that the thermal switch can be driven passively, but the requirement on the preset working temperature range is higher, precise manufacturing is needed, and the cost is higher; the reluctance type thermal switch principle is that the reluctance effect of certain metals is utilized, when a magnetic field is applied, the action of Lorentz force is applied, the movement of heat-carrying electrons is restrained, the heat conductivity of the material can be reduced to the level of heat conduction only by phonons, so that the switch is larger, but the reluctance type thermal switch is only limited to extremely low-temperature application, a large magnetic field and a corresponding electromagnet are needed, the cost is higher, the occupied space is larger, meanwhile, the reluctance material is too fragile and easy to damage, and the processing and maintenance cost is increased.

Disclosure of Invention

An object of the present invention is to provide a cooling system capable of improving the operational safety and stability of the cooling system, improving the structural compactness of the cooling system, and reducing the installation cost of the cooling system.

Another object of the present invention is to provide a superconducting magnet system capable of improving the structural compactness of the superconducting magnet system and improving the operation efficiency, operation safety and operation reliability of the superconducting magnet system.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the cooling system is used for cooling a cooled load and comprises a vacuum cover, refrigerating machines and first thermal switches, wherein at least two refrigerating machines are arranged, each refrigerating machine is provided with a cold head, the first thermal switches are arranged in one-to-one correspondence with the refrigerating machines, and the cooled load, the cold heads and the first thermal switches are all positioned in the vacuum cover;

the first thermal switch comprises a first low-temperature pulsating heat pipe, an evaporation section of the first low-temperature pulsating heat pipe is connected with the cooled load, a condensation section of the first low-temperature pulsating heat pipe is connected with the cold head, and when the cold head is at the final refrigeration temperature, a first working medium in the first low-temperature pulsating heat pipe is in a two-phase flow state.

As an alternative technical scheme of the refrigerating system, the cooling system further comprises a primary radiation protection screen, the primary radiation protection screen is suspended in the vacuum cover, the cooled load is positioned in the primary radiation protection screen, and the cold head is in thermal connection with the primary radiation protection screen.

As an alternative technical scheme of a refrigerating system, each refrigerating machine comprises two cold heads, wherein the two cold heads are a first-stage cold head and a second-stage cold head respectively, a condensation section of the first low-temperature pulsating heat pipe is connected with the second-stage cold head, and the first-stage cold head is thermally connected with the first-stage radiation-proof screen;

the cooling system further comprises a second thermal switch, the second thermal switch comprises a second low-temperature pulsating heat pipe, a condensation section of the second low-temperature pulsating heat pipe is thermally connected with the first-stage cold head, an evaporation section of the second low-temperature pulsating heat pipe is thermally connected with the cooled load, and a triple point critical in the second low-temperature pulsating heat pipe is higher than the final refrigeration temperature of the first-stage cold head.

As an alternative technical scheme of the refrigerating system, a secondary radiation-proof screen is suspended in the primary radiation-proof screen, the cooled load is positioned in the secondary radiation-proof screen, and the secondary cold head is in thermal connection with the secondary radiation-proof screen.

As an alternative technical scheme of the refrigerating system, the secondary radiation protection screen is connected with the secondary cold head through a third thermal switch, the third thermal switch comprises a third low-temperature pulsating heat pipe, an evaporation section of the third low-temperature pulsating heat pipe is thermally connected with the secondary radiation protection screen, a condensation section of the third low-temperature pulsating heat pipe is thermally connected with the secondary cold head, and when the secondary cold head is at a final refrigerating temperature, a third working medium in the third low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

As an alternative technical scheme of the refrigerating system, the cold head is thermally connected with the primary radiation protection screen through a fourth thermal switch, the fourth thermal switch comprises a fourth low-temperature pulsation heat pipe, an evaporation section of the fourth low-temperature pulsation heat pipe is thermally connected with the primary radiation protection screen, a condensation section of the fourth low-temperature pulsation heat pipe is thermally connected with the cold head, and when the cold head is at a final refrigerating temperature, a fourth working medium in the fourth low-temperature pulsation heat pipe is in a gas-liquid two-phase flow state.

As an alternative technical scheme of the refrigerating system, the cooling system comprises a first filling system, the first filling system is used for filling a first working medium into the first low-temperature pulsating heat pipe, and the first filling system and the first thermal switch are arranged in one-to-one correspondence.

As an alternative technical scheme of the refrigeration system, the first working medium is helium, hydrogen, neon or nitrogen;

the second working medium in the second low-temperature pulsating heat pipe is neon, argon, nitrogen, oxygen or methane.

As an alternative technical scheme of the refrigeration system, the outer surface of the cold head and/or the first thermal switch is/are coated with a heat insulation layer;

and/or the first thermal switch is provided with a first connecting surface and a second connecting surface, the first connecting surface is in thermal connection with the cold head, the second connecting surface is in thermal connection with the cooled load, and the first connecting surface and/or the second connecting surface is/are provided with a heat conducting coating and/or a heat conducting sheet.

A superconducting magnet system comprising a superconducting magnet, and further comprising a cooling system as described above, the superconducting magnet being the cooled load.

The invention has the beneficial effects that:

according to the cooling system provided by the invention, the first heat switch comprises the first low-temperature pulsating heat pipe, when the refrigerator corresponding to the first heat switch works normally, the temperature of the cold head of the refrigerator can reach the final refrigeration temperature, so that the first working medium in the condensation section of the first low-temperature pulsating heat pipe can be condensed into a liquid state, the first working medium in the evaporation section of the first low-temperature pulsating heat pipe is evaporated into a gaseous state due to the influence of the temperature of a cooled load, and the first working medium in the first low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state due to the influence of capillary force due to the thinner pipe diameter, so that the heat conductivity is higher, the heat transfer is better, and the heat generated during the operation of the cooled load can be taken away through the first low-temperature pulsating heat pipe quickly; when the refrigerator fails or stops working, the temperature of a cold head of the refrigerator rises, the temperature of a condensation section connected with the refrigerator rises to be higher than the critical temperature of a first working medium, the first working medium in the condensation section is converted into a gaseous state, the thermal resistance of the first low-temperature pulsating heat pipe is increased, and the first thermal switch is in an off state, so that heat is prevented from being transmitted to a cooled load through the first thermal switch.

According to the superconducting magnet system provided by the invention, by adopting the cooling system, at least two refrigerators and the first thermal switch comprising the first low-temperature pulsating heat pipe are connected before the refrigerators and the cooled load, so that when the refrigerators fail, the high temperature of the refrigerators is prevented from being transmitted to the cooled load, the cooled load is ensured to safely and stably operate under the cooling action of other refrigerators, and the operation safety and reliability of the superconducting magnet system are improved; meanwhile, as the thermal switch occupies smaller space, the arrangement is flexible, and the structural compactness of the superconducting magnet system can be effectively improved.

Drawings

Fig. 1 is a schematic view of a superconducting magnet system according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram of a pulsating heat pipe according to a first embodiment of the present invention;

fig. 3 is a schematic structural diagram of a filling system according to a second embodiment of the present invention;

fig. 4 is a schematic structural diagram of a first thermal switch according to a third embodiment of the present invention;

FIG. 5 is a top view of the structure of FIG. 4;

FIG. 6 is a side view of the structure of FIG. 4;

fig. 7 is a schematic structural diagram of a first thermal switch according to a fourth embodiment of the present invention;

fig. 8 is a schematic structural diagram of a first thermal switch and a fourth thermal switch according to a fifth embodiment of the present invention;

Fig. 9 is a schematic structural view of a superconducting magnet system provided in a sixth embodiment of the present invention;

fig. 10 is a schematic structural view of a superconducting magnet system provided in a seventh embodiment of the present invention;

fig. 11 is a schematic structural view of a superconducting magnet system according to an eighth embodiment of the present invention.

The figures are labeled as follows:

1. a vacuum cover; 11. an outer cylinder; 12. a flange plate; 2. a primary radiation shield; 3. a refrigerating machine; 31. a cold head; 31a, a primary cold head; 31b, a secondary cold head; 4. a first thermal switch; 41. a first low temperature pulsating heat pipe; 411. a parallel tube portion; 412. a bending part; 413. a joint pipe section; 42. a condensing plate; 421. a first positioning groove; 43. an evaporation plate; 431. a second positioning groove; 44. a liquid injection joint; 5. a second thermal switch; 6. a power supply assembly; 61. a superconducting wire; 62. high temperature superconductive current lead; 64. an external current wiring assembly; 65. a superconducting excitation power supply; 7. a first support structure; 8. a second support structure; 9. a secondary radiation shield;

10. a cooled load; 101. a room temperature hole; 20. a filling system; 201. a buffer tank; 202. a gas cylinder; 203. a molecular pump unit; 204. a first stop valve; 205. a second shut-off valve; 206. a third stop valve; 207. a first pressure sensor; 208. a second pressure sensor; 209. a filling pipe; 30. a third thermal switch; 40. a fourth thermal switch;

100a, an evaporation section; 100b, a condensation section; 100c, an insulation section; 100d, air plug; 100e, liquid plug.

Detailed Description

The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.

In the description of the present invention, unless explicitly stated and limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "right", etc. orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are merely for convenience of description and simplicity of operation, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the invention. Furthermore, the terms "first," "second," and the like, are used merely for distinguishing between descriptions and not for distinguishing between them.

Example 1

As shown in fig. 1, the present embodiment provides a cooling system that can cool a cooled load 10 to a preset operating temperature, so that the cooled load 10 is kept operating in a low-temperature environment, ensuring the operational safety and reliability of the cooled load 10. Wherein the load 10 to be cooled may be a superconducting magnet or other device having a relatively high specific heat capacity and requiring operation in a cryogenic environment.

Specifically, the cooling system includes a vacuum enclosure 1, a refrigerator 3, and a first thermal switch 4. The refrigerators 3 are provided with at least two, each refrigerator 3 is provided with a cold head 31, the first thermal switches 4 are arranged in one-to-one correspondence with the refrigerators 31, and the cooled load 10, the cold heads 31 and the first thermal switches 4 are all positioned in the vacuum cover 1. The first thermal switch 4 comprises a first low-temperature pulsating heat pipe 41, a condensation section of the first low-temperature pulsating heat pipe 41 is thermally connected with the cold head 31, an evaporation section of the first low-temperature pulsating heat pipe 41 is connected with the cooled load 10, and when the cold head 31 is at a final refrigeration temperature, a first working medium in the first low-temperature pulsating heat pipe 41 is in a two-phase flow state.

According to the cooling system provided by the embodiment, the first heat switch 4 comprises the first low-temperature pulsating heat pipe 41, when the refrigerator 3 corresponding to the first heat switch 4 works normally, the temperature of the cold head of the refrigerator 3 can reach the final refrigeration temperature, so that the condensation section of the first low-temperature pulsating heat pipe 41 is lower than the saturation temperature, the first working medium in the pipe can be condensed into a liquid state, the evaporation section of the first low-temperature pulsating heat pipe 41 is higher than the saturation temperature, the first working medium in the pipe is evaporated into a gaseous state due to the influence of the temperature of the cooled load 10, and the capillary pipe diameter is small, the first working medium in the first low-temperature pulsating heat pipe 41 is in a gas-liquid two-phase flow state under the action of capillary force, so that the heat conductivity is higher, the heat transfer is better, and the heat generated when the cooled load 10 operates can be quickly taken away through the first low-temperature pulsating heat pipe 41; when the refrigerator 3 fails or stops working, the temperature of the cold head 31 of the refrigerator 3 rises, the temperature of the condensation section connected with the refrigerator 3 rises to be higher than the critical temperature of the first working medium, the first working medium in the condensation section is converted into a gaseous state, the thermal resistance of the first low-temperature pulsating heat pipe 41 is increased, the first thermal switch 4 is in an off state, and heat is prevented from being transferred to the cooled load 10 through the first thermal switch 4.

That is, in the cooling system provided in this embodiment, by providing at least two refrigerators 3 and providing the first thermal switch 4 between the cold head 31 of the refrigerator 3 and the cooled load 10, the operation safety and reliability of the cooling system can be ensured by the redundant arrangement of the refrigerators 3; meanwhile, when the first low-temperature pulsating heat pipe 41 is conducted, the heat conduction is higher than that of heat conduction metal by several orders of magnitude, the heat transfer efficiency is high, the cooling efficiency of the cooled load 10 can be effectively improved, meanwhile, the switch is relatively large (can reach more than 2500), the heat insulation performance of the first heat switch 4 when being disconnected can be effectively ensured, and the use reliability of a cooling system is ensured; moreover, as the first thermal switch 4 can be automatically turned off and on according to the temperature change of the cold head 31, mechanical and electromagnetic driving is not needed, the control difficulty is reduced, the control precision is improved, the use reliability of the first thermal switch 4 is ensured, meanwhile, the structural complexity and the space occupation rate of the first thermal switch 4 are reduced, and the cost of a cooling system is reduced; furthermore, the first cryogenic pulsating heat pipe 41 has small volume, light weight and long heat transfer distance, and can be arranged in a bending manner, so that the first cryogenic pulsating heat pipe 41 can be easily integrated into a structure with strict quality and space limitation, the structural compactness of the cooling system is improved, and the cooling system is particularly suitable for remote superconducting magnet applications sensitive to vibration, such as nuclear magnetic resonance imaging.

As shown in FIG. 2, it is worth noting that the pulsating heat pipe is a passive heat transfer device, which is a serpentine tubular structure formed by repeatedly bending a metal capillary tube with a smaller inner diameter, typically 0.5-3 mm, between a hot end and a cold end, and the tube is filled with two-phase fluid. Because the pipe diameter is small enough, capillary action is dominant, and surface tension enables working medium to form air plugs 100d and liquid plugs 100e which are distributed in random and alternating mode in the capillary.

Pulsating heat pipes generally include a condensing section 100b, an evaporating section 100a, and an insulating section 100c between condensing section 100b and evaporating section 100 a. In the running process of the pulsating heat pipe, a heat load is applied to the evaporation section 100a, working medium positioned in the evaporation section 100a absorbs heat, and evaporates in the liquid or on the surface of the liquid film to generate new bubbles or increase the volume of the original bubbles, so that the length of the air lock 100d is increased, and the pressure in the evaporation section 100a is increased; meanwhile, a cold load is applied to the condensation section 100b, and the gaseous working medium in the condensation section 100b is liquefied and released into a liquid working medium, so that bubbles in the condensation section 100b are reduced or disappear, and the pressure in the condensation section 100b is reduced. That is, the pressure difference between the evaporation section 100a and the condensation section 100b of the pulsating heat pipe, which is generated by the temperature difference, pushes the working medium from the evaporation section 100a to the condensation section 100b, and the growth and the rupture of bubbles cause the pressure difference between the evaporation section 100a and the condensation section 100b and the pressure imbalance between the adjacent pipes, so that the working medium is pushed to perform pulsating movement or guide the circulating flow in the pipes, and the sensible heat transfer heat is generated when the working medium flows through the latent heat of the gas-liquid phase change and the liquid plug 100e. That is, the oscillating fluid flow and heat transfer in the pulsating heat pipe are driven entirely by transient pressure differences caused by local evaporation and condensation, mechanical power output is not needed, and moving parts are not needed, so that the pulsating heat pipe has higher reliability. Meanwhile, compared with other heat pipes, the pulsating heat pipe has the advantages that the gas phase and the liquid phase of the pulsating heat pipe flow in the same direction generally, the problem that the gas hinders the liquid backflow does not exist, the forced convection heat transfer between the working medium and the pipe wall is very obvious besides the phase change heat transfer, and the pulsating heat pipe has stronger heat transfer capability.

The working medium in the pulsating heat pipe is a working medium with high heat conductivity, and the low-temperature pulsating heat pipe is a pulsating heat pipe with lower critical temperature of the working medium in the pulsating heat pipe. In this embodiment, according to the preset working temperature of the load 10 to be cooled and the final cooling temperature reached by the primary cold head 31a, the first working medium may be selected as helium, neon, hydrogen or nitrogen or other working medium capable of being used as the pulsating heat pipe working medium, where the gas-liquid saturation temperature of helium at normal pressure is about 4.2K, the gas-liquid saturation temperature of neon at normal pressure is about 25K, the gas-liquid saturation temperature of hydrogen at normal pressure is about 20K, and the gas-liquid saturation temperature of nitrogen at normal pressure is about 77K.

In this embodiment, the condensing section may be directly connected to the cold head 31, and/or the evaporating section may be directly connected to the cooled load 10, or the condensing section and/or the evaporating section may be fixed to a metal plate with high heat conductivity, and then the metal plate is connected to the corresponding cold head 31 or the cooled load 10.

It is to be understood that, in the present embodiment, the heat insulation section, the evaporation section and/or the condensation section of the first low temperature pulsating heat pipe 41 may be vertically arranged or bent, so as to be suitable for the connection of the first low temperature pulsating heat pipe 41 to the cold head 31 and the cooled load 10, which is not particularly limited in the present invention.

The first thermal switch 4 has a first connection surface thermally connected to the cold head 31 and a second connection surface connected to the cooled load 10, and the first connection surface and/or the second connection surface are provided with a heat conductive structure including a heat conductive coating and/or a heat conductive sheet to increase the thermal conductivity at the connection and reduce the contact thermal resistance for improving the heat conduction efficiency. Preferably, the heat conducting layer is an apizon N high heat conducting grease layer, and the heat conducting sheet is an indium sheet.

As shown in fig. 1, the refrigerator 3 is preferably a GM refrigerator or a pulse tube refrigerator, and the refrigeration power of the refrigerator 3 and the final refrigeration temperature that the cold head 31 can reach can be specifically determined according to the preset operation temperature required by the cooled load 10. The refrigerator 3 is an existing mature product, and the specific structure of the refrigerator 3 will not be described in detail in this embodiment.

In this embodiment, the vacuum cover 1 includes an outer cylinder 11 with two open ends and flanges 12 mounted on the upper and lower ends of the outer cylinder 11, and the flanges 12 are detachably connected with the outer cylinder 11 and block corresponding ports of the outer cylinder 11. The structure of this kind of vacuum cover 1 sets up, is favorable to the dismouting of vacuum cover 1 inner structure, improves cooling system's dismouting and maintenance convenience. In other embodiments, the outer cylinder 11 may be open at the upper end, i.e. the flange 12 is provided at the upper end of the outer cylinder 11.

The vacuum housing 1 is preferably made of a non-magnetic stainless steel material to avoid rust and to improve the support stability of its internal structure. The outer cylinder 11 may be, but not limited to, a cylinder, and the shape of the flange 12 is adapted to the shape of the outer cylinder 11.

The cooling system further comprises a vacuumizing device, wherein the vacuumizing device is used for vacuumizing the inner space of the vacuum cover 1. An aviation socket and a vacuum extraction opening are formed in a flange plate 12 at the upper end of the vacuum cover 1, the vacuumizing device is located outside the vacuum cover 1, and vacuumizing is carried out inside the vacuum cover 1 through the vacuum extraction opening, so that gas heat conduction is reduced.

In order to further improve the cooling efficiency of the cooled load 10, the cooling system further comprises a primary radiation protection screen 2, wherein the primary radiation protection screen 2 is suspended in the vacuum cover 1, and the cooled load 10 is suspended in the primary radiation protection screen 2. The primary radiation shield 2 is used for reducing heat radiation from the outside of the vacuum enclosure 1 to the cooled load 10 and reducing interference of the external environment to the cooled load 10.

The primary radiation shield 2 is preferably suspended within the vacuum enclosure 1 using a second support structure 8, and the cooled load 10 passes through the primary radiation shield 2 of the first support structure 7. The first support structure 7 and the second support structure 8 may be made of a high-strength low-thermal-conductivity material, such as G10 glass fiber reinforced plastic, according to the prior art, and the present invention is not limited thereto. The primary radiation shield 2 is preferably made of oxygen free high purity copper.

The primary radiation shield 2 is preferably thermally coupled to the coldhead 31 such that the temperature of the primary radiation shield 2 approaches the temperature of the coldhead 31, reducing radiation heat leakage from the environment external to the vacuum enclosure 1 to the cooling load 10.

Preferably, the cold head 31 is thermally connected to the primary radiation shield 2 through a fourth thermal switch 40, the fourth thermal switch 40 includes a fourth low-temperature pulsating heat pipe, an evaporation section of the fourth low-temperature pulsating heat pipe is thermally connected to the primary radiation shield 2, a condensation section of the fourth low-temperature pulsating heat pipe is thermally connected to the cold head 31, and when the cold head 31 is at a final refrigeration temperature, a fourth working medium in the fourth low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state. This arrangement ensures that when a particular refrigerator 3 is shut down or fails, the fourth thermal switch 40 corresponding to that refrigerator 3 is turned off, preventing heat from the refrigerator 3 from being transferred to the primary radiation shield 2.

In other embodiments, the coldhead 31 may also be thermally coupled directly to the primary radiation shield 2 to reduce cost. In another embodiment, the two refrigerators 3 may be a main refrigerator and a standby refrigerator, respectively, the cold head 31 of the main refrigerator is directly thermally connected to the primary radiation shield 2, and the cold head of the standby refrigerator may be thermally connected to the primary radiation shield 2 through the fourth thermal switch 40.

In this embodiment, the fourth working medium in the fourth low-temperature pulsating heat pipe is the same as the first working medium in the first low-temperature pulsating heat pipe.

To reduce the radiation leakage heat, the outer surface of the primary radiation shield 2, the first thermal switch 4, the cooled load 10, the fourth thermal switch 40 and/or the coldhead 31 is covered with a heat insulating Layer, preferably made of a high vacuum Multi-Layer Insulation (MLI).

Further, the cooling system further comprises a filling system for filling the first cryopulsation heat pipe 41 with a working medium. The structure of the filling system and the liquid injection manner of the first low-temperature pulsating heat pipe 41 can be referred to in the related art, and this embodiment is not limited thereto.

In this embodiment, preferably, a filling system is disposed corresponding to each first thermal switch 4, so as to implement separate filling control for the first low-temperature pulsating heat pipe 41 in each first thermal switch 4. In other embodiments, all the first thermal switches 4 may share the same filling system, i.e. the same filling system fills the first cryopulsation heat pipes 41 in all the first thermal switches 4 simultaneously.

In an embodiment, each fourth thermal switch 4 is correspondingly provided with a filling system, and one realizes the independent filling control of the fourth low-temperature pulsating heat pipe in each fourth thermal switch 4.

The present embodiment also provides a superconducting magnet system, which includes a superconducting magnet and the cooling system described above, and the superconducting magnet is the cooled load 10. According to the superconducting magnet system provided by the embodiment, by arranging at least two refrigerators 3 and connecting the first thermal switch 4 comprising the first low-temperature pulsating heat pipe 41 between the refrigerator 3 and the cooled load 10, when the refrigerator 3 fails, the high temperature of the refrigerator 3 is prevented from being transmitted to the cooled load 10, the cooled load 10 can be ensured to safely and stably operate under the cooling action of other refrigerators 3, and the operation safety and reliability of the superconducting magnet system are improved; meanwhile, the first thermal switch 4 occupies a small space, is flexible to arrange, can effectively improve the structural compactness of the superconducting magnet system, and is particularly suitable for remote superconducting magnet applications sensitive to vibration, such as nuclear magnetic resonance imaging.

It is understood that the preset operating temperature of the superconducting magnet is lower than the superconducting transition temperature.

Further, the superconducting magnet includes a superconducting magnet coil and a support frame for mounting the superconducting magnet coil. The superconducting magnet is fixed in the primary radiation shield 2 by a first support structure 7, the first support structure 7 may comprise a pull rod or a pull ring, and the first support structure 7 is preferably made of a material with low thermal conductivity, high insulation and high strength, such as G10 glass fiber reinforced plastic, etc. The support skeleton is a cylindrical structure, and the inner hole forms a room temperature hole 101 for placing a sample. When the superconducting magnet is operated, there is a uniform magnetic field in the room temperature bore 101.

In order to obtain high magnetic field strength, the superconducting magnet coil may be composed of a plurality of coils, and the coil material may be NbTi, nb ₃ Sn, or magnesium diboride, yttrium barium copper oxide, or the like. The supporting framework can be made of 6063-T1 aluminum alloy and other materials.

The central axis of the room temperature hole 101 may be disposed in a vertical direction or a horizontal direction, or may be disposed in other directions, that is, the central axis of the room temperature hole 101 may be specifically disposed according to a specific type of superconducting magnet system and an application scenario.

In the present embodiment, the evaporation section of the first thermal switch 4 is connected with the support frame to improve the connection convenience of the first thermal switch 4 and the superconducting magnet.

The superconducting magnet system further includes a diode assembly for quench protection of the superconducting magnet. The superconducting magnet system further includes a power supply assembly 6, the power supply assembly 6 including a superconducting field power supply 65 and a wire 61 connected between the superconducting field power supply 65 and the superconducting magnet coils. The superconducting excitation power supply 65 is located outside the vacuum enclosure 1.

To better achieve the connection between the superconducting magnet and the superconducting excitation power supply 65, the superconducting magnet system further comprises an external current wiring assembly 64 and a high-temperature superconducting current lead 62, the high-temperature superconducting current lead 62 is thermally connected with the cold head 31, wires 61 are connected between the external current wiring assembly 64 and the high-temperature superconducting current lead 62 and between the high-temperature superconducting current lead 62 and the cooled load 10, and the external current wiring assembly 64 is mounted on the vacuum enclosure 1 so as to butt-joint the wires 61 located on the inner side and the outer side of the vacuum enclosure 1. The external current connection assembly 64 is provided insulated from the vacuum envelope 1. The specific structure of the high temperature superconductive current lead 62 and the external current connection set 64 may refer to the prior art, and the present invention is not repeated and limited in this description.

The superconducting magnet system provided by the embodiment can be applied to the aspects of information technology, biomedicine, environmental technology, military industry, industrial processing, sea, transportation, major science engineering and superconducting power, such as medical nuclear magnetic resonance imaging equipment MRI, nuclear magnetic resonance spectrometer MNR, superconducting magnetic separation system, superconducting energy storage system, superconducting motor, superconducting cable, superconducting transformer, superconducting current limiter, superconducting induction heating, superconducting particle accelerator, superconducting magnetic suspension train and the like.

Example two

The present embodiment provides a cooling system and a superconducting magnet system, and the cooling system and the superconducting magnet system provided in the present embodiment are based on further improvements of the structure in the first embodiment, and the description of the same structure as that in the first embodiment is omitted.

In this embodiment, the cooling system further includes a filling system 20, where the filling system 20 is used to fill the first low-temperature pulsating heat pipe 41 of the first thermal switch 4 with the first working fluid, and the filling system 20 is mainly located outside the vacuum enclosure 1.

Specifically, the filling system 20 includes a buffer tank 201, a gas storage bottle 202, a molecular pump unit 203 and a filling pipe 209, where the buffer tank 201 is connected to an air inlet end of the filling pipe 209 through a first pipeline, the molecular pump unit 203 is connected to an air inlet end of the filling pipe 209 through a second pipeline, an air outlet end of the filling pipe 209 is connected to the first thermal switch 4, and the gas storage bottle 202 is connected to an air inlet end of the filling pipe 209 through a third pipeline. Wherein, be provided with first stop valve 204 on the filling pipe 209, be provided with second stop valve 205 on the second pipeline, be provided with third stop valve 206 on the third pipeline.

The charging system 20 further comprises a first pressure sensor 207, provided on the charging pipe 209, for detecting pressure fluctuations in the condensing section of the first cryopulsating heat pipe 41. A second pressure sensor 208 is provided at the buffer tank 201 for detecting the pressure of the buffer tank 201 and calculating the filling rate.

The gas cylinder 202 stores a first working medium with high purity (purity is 99.999%) and in a gaseous state, and the liquid filling process of the first low-temperature pulsating heat pipe 41 specifically comprises the following operation steps:

(1) Temperature and pressure data are collected and recorded.

(2) The first low temperature pulsating heat pipe 41, the buffer tank 201 and the pipes in the filling system 20 are purged and purified of gas by using the high purity first working substance and a set of molecular pump units 203 to prevent residual air or other impurities in the pipes from affecting the experiment.

The specific process is as follows:

first, the first stop valve 204 and the second stop valve 205 are opened, the third stop valve 206 is closed, and the molecular pump set 203 is used to pump the first cryopulsation heat pipe 41 and the filling system 20 to a high vacuum (< 1×10) ^-3 Pa)；

Then the second stop valve 205 is closed, the first stop valve 204 and the third stop valve 206 are opened, and 99.999 percent of Gao Chundi working medium is filled into the first low-temperature pulsating heat pipe 41 and the buffer tank 201 from the gas storage bottle 202;

The same process is repeated more than 5 times to thoroughly remove the impurity gases from the pulsating heat pipe and the filling system 20, and after completion, a high vacuum is drawn.

(3) After the purification process is completed, the third stop valve 206 is opened, the first stop valve 204 and the second stop valve 205 are closed, the gas cylinder 202 is opened, the buffer tank 201 is filled with the high-purity first working medium, then the first stop valve 204 is closed, and the initial pressure P of the buffer tank 201 at the moment is recorded ₀ 。

(4) The first stop valve 204 is opened, the second stop valve 205 and the third stop valve 206, gao Chundi are closed, and working medium enters the first low-temperature pulsating heat pipe 41 from the buffer tank 201.

(5) Vacuumizing the vacuum cover 1 by using another group of molecular pump units 203 until the vacuum degree in the vacuum cover 1 is less than 1×10 ^-3 After Pa, the refrigerator 3 is started to cool down the first low-temperature pulsating heat pipe 41.

(6) As the temperature of the condensing section of the first low-temperature pulsating heat pipe 41 decreases, the pressure also decreases, when the temperature of the gas-liquid two-phase flow temperature zone of the first working medium decreases, the liquid first working medium starts to be generated, the pressure rapidly decreases, the liquid first working medium moves from the condensing section to the evaporating section under the action of gravity and absorbs heat to evaporate, and the evaporating section is accelerated to cool to the working temperature. When the pressure of the buffer tank 201 is reduced to the pressure P corresponding to the target filling rate ₁ When the first shut-off valve 204 is closed, the first low temperature pulsating heat pipe 41 is isolated from the filling system 20. At this time, the inside of the first low-temperature pulsating heat pipe 41 is in an initial state in which air plugs and liquid plugs are alternately distributed, and the liquid filling process is ended.

The mass of the first working medium filled in the first low-temperature pulsating heat pipe 41 is expressed by the filling rate, and for comparison with the existing research data, when the first working medium is helium, the filling rate is defined as the ratio of the volume of liquid helium to the volume of the pulsating heat pipe under 4.215K.

When the liquid filling rate is calculated, the first low-temperature pulsating heat pipe 41 and the first working substance in the filling system 20 are regarded as ideal gas, and the mass m of the first working substance is filled according to the law of conservation of mass and the ideal gas state equation _t Can be calculated by the following formula:

wherein: p (P) ₀ And P ₁ The initial pressure and the final pressure of the buffer vessel 201 at the beginning and end of the filling process, respectively, are given in Pa; v (V) _FT And V _BT The volumes of the liquid charging pipe (the part from the first stop valve 204 to the first low-temperature pulsating heat pipe 41) and the buffer tank 201 are respectively m ³ ；T _FT And T _BT Average temperature of the liquid charging pipeline and the buffer tank 201 is K; r is R _g Is the gas constant of the first working medium, e.g. R when the first working medium is helium _g ＝2077J/(kg·K)；m _t The unit is kg for filling the working medium of the pulsating heat pipe.

The mass of the liquid working medium charged into the first low-temperature pulsating heat pipe 41 is the sum of the saturated gas mass and the saturated liquid mass of the first working medium. Taking the first working medium as helium as an example, the mass of liquid helium charged into the first cryogenic pulsating heat pipe 41 is the sum of the saturated helium mass and the saturated liquid helium mass. Since the density of the saturated helium gas and the saturated liquid helium gas and the mass of the helium charged into the first cryogenic pulsating heat pipe 41 are known, the volume of the saturated liquid helium gas can be obtained by:

m _t ＝ρ _l V _l +ρ _v (V _PHP -V _l ) (formula 2);

wherein V is _PHP And V _l The unit is m, which is the volume of the first low-temperature pulsating heat pipe 41 and the volume of liquid helium in the pipe respectively ³ ；ρ _v And ρ _l The density of saturated helium and saturated liquid helium at 4.215K is kg/m ³ 。

Therefore, the filling ratio is:

the liquid filling rate of the first low-temperature pulsating heat pipe 41 can be determined based on the initial pressure and the final pressure of the buffer tank 201 in the combined type 1 to 3. The calculation of the fill rate takes into account the effect of the fill tube volume while the volume of the rest of the tubing of the filling system 20 is considered to be a fraction of the volume of the buffer tank 201.

It should be noted that the liquid filling method is also applicable to other low-temperature working media.

The liquid filling rate of the first low-temperature pulsating heat pipe 41 is recommended to be between 20% and 80%, the liquid filling rate is too low to be burnt out, the flow resistance is large, and the operation is difficult to start.

In addition to controlling the liquid filling rate before the operation of the first low temperature pulsating heat pipe 41, the buffer tank 201 can automatically adjust the liquid filling rate and pressure during the operation of the first low temperature pulsating heat pipe 41 to prevent dry out. The first stop valve 204 is only required to be opened, so that the buffer tank 201 is connected with the first low-temperature pulsating heat pipe 41 to operate.

It should be noted that, when the filling system corresponding to the fourth thermal switch 40 and the filling system corresponding to the first thermal switch 4 are respectively set, the filling system of the fourth thermal switch 40 may be set with reference to the filling system of the first thermal switch 4.

Example III

The present embodiment provides a cooling system and a low-temperature superconducting magnetic system, and the cooling system provided in the present embodiment is a further improvement of the cooling system in the first embodiment, and the details of the cooling system in the first embodiment are not described in detail.

As shown in fig. 4 to 6, in the present embodiment, the first thermal switch 4 further includes a condensation plate 42, an evaporation plate 43, and a liquid injection joint 44. The first low-temperature pulsating heat pipe 41 is formed in a serpentine structure by bending a capillary tube, and includes a plurality of parallel pipe portions 411 arranged in parallel and at intervals in a first direction and a bending portion 412 connected between two adjacent parallel pipe portions 411. The parallel pipe portion 411 has a condensing section, an insulating section, and an evaporating section connected in order.

The condensing plate 42 is provided with a plurality of first positioning grooves 421, the surface of the evaporating plate 43 is provided with a plurality of second positioning grooves 431, the first positioning grooves 421 and the second positioning grooves 431 are arranged in one-to-one correspondence with the parallel pipe portions 411, the condensing section of the parallel pipe portions 411 is positioned in the first positioning grooves 421, the evaporating section of the parallel pipe portions 411 is positioned in the second positioning grooves 431, and soldering tin is filled in the first positioning grooves 421 and the second positioning grooves 431 so as to fix the first low-temperature pulsating heat pipes 41 and the corresponding condensing plate 42 and evaporating plate 43, heat resistance is reduced, and good thermal contact between the first low-temperature pulsating heat pipes 41 and the condensing plate 42 and the evaporating plate 43 is ensured. The bending part 412 connected to the condensation section is located at one side of the condensation plate 42 away from the evaporation plate 43, and the bending part 412 connected to the evaporation section evaporates one side of the condensation plate 42 away from the evaporation plate 43.

The groove widths of the first positioning groove 421 and the second positioning groove 431 are preferably larger than the outer diameter of the first low-temperature pulsating heat pipe 41, so that the first low-temperature pulsating heat pipe 41 is accommodated in the first positioning groove 421 and the second positioning groove 431, and space is provided for filling soldering tin. The evaporating plate 43 and the condensing plate 42 are preferably made of pure copper, so that the heat conduction efficiency is high. The first cryopulse heat pipe 41 is preferably made of stainless steel or pure copper.

The first thermal switch 4 is preferably a multi-layer structure, that is, the parallel tube portion 411 extends along the second direction, the first thermal switch 4 preferably includes multiple layers of first low-temperature pulsating heat pipes 41 arranged side by side along the third direction, the evaporating plate 43 and the condensing plate 42 are respectively arranged in one-to-one correspondence with the first low-temperature pulsating heat pipes 41, and the first direction, the second direction and the third direction are mutually perpendicular. The first thermal switch 4 having the multilayer first low-temperature pulsating heat pipe 41 can increase the thermal conductivity, save the space occupied by the first thermal switch 4, and improve the structural compactness of the first thermal switch 4.

In the present embodiment, all the evaporation plates 43 are stacked and fastened together in the third direction, and all the condensation plates 42 are stacked and fastened together in the third direction.

A liquid filling channel is arranged in the liquid filling joint 44, and a filling pipe of the filling system is communicated with the first low-temperature pulsating heat pipe 41 through the liquid filling channel. In this embodiment, all the first low-temperature pulsating heat pipes 41 are arranged in parallel, the two ends of each first low-temperature pulsating heat pipe 41 are formed with joint pipe portions 413, the liquid injection channels are arranged in one-to-one correspondence with the first low-temperature pulsating heat pipes 41, and the two joint pipe portions 413 of each first low-temperature pulsating heat pipe 41 are inserted into the liquid injection channels and are communicated with the liquid injection channels in a sealing manner. This kind of setting can simplify the processing of first thermal switch 4, improves first thermal switch 4 dismouting convenience.

In other embodiments, all the first low-temperature pulsating heat pipes 41 are arranged in series, i.e. the corresponding ends of two adjacent first low-temperature pulsating heat pipes 41 are connected, all the first low-temperature pulsating heat pipes 41 have only two joint pipe portions 413, the liquid injection joint 44 is provided with one liquid injection channel, and the two joint pipe portions 413 are inserted into the liquid injection channel and are in sealing communication with the liquid injection channel.

Illustratively, the first low-temperature pulsating heat pipe 41 is provided with four layers, each layer of the first low-temperature pulsating heat pipe 41 having 12 parallel pipe sections 411. In other embodiments, the number of layers of the first low-temperature pulsating heat pipe 41 and the number of parallel pipe sections 411 included in the first low-temperature pulsating heat pipe 41 may be set according to requirements, for example, three, five or more layers may be provided, and each layer includes 6 to 18 parallel pipe sections 411.

Further, during the processing of the first thermal switch 4, the evaporating plates 43 between two adjacent layers and the condensing plates 42 between two adjacent layers are welded with tin first, so that the gaps are filled with tin as much as possible; all evaporation plates 43 and all condensation plates 42 are fastened by bolts or screws.

In other embodiments, the first thermal switch 4 may also include a plurality of first low-temperature pulsating heat pipes 41 disposed side by side in the first direction, where each first low-temperature pulsating heat pipe 41 is separately provided with a liquid injection joint 44 and a filling system, that is, each first low-temperature pulsating heat pipe 41 may be separately controlled to be injected with liquid. In still another embodiment, the first thermal switch 4 may include a plurality of first low-temperature pulsating heat pipes 41 arranged side by side in the first direction, and both ends of each of the first low-temperature pulsating heat pipes 41 are connected into a communication pipe, which communicates with the charging system.

The first thermal switch 4 has a first connection surface thermally connected to the cold head 31 and a second connection surface thermally connected to the load 10 to be cooled. In the present embodiment, the evaporating plate 43 of the outermost layer has a second connection surface on a side away from the adjacent evaporating plate 43, and the condensing plate 42 of the outermost layer has a first connection surface on a side away from the adjacent condensing plate 42.

In order to improve the heat conduction efficiency, the first connecting surface and/or the second connecting surface are/is provided with a heat conduction structure, and the heat conduction structure comprises a heat conduction coating and/or a heat conduction sheet so as to increase the heat conduction rate of the connecting part and reduce the contact thermal resistance. Preferably, the heat conducting layer is an apizon N high heat conducting grease layer, and the heat conducting sheet is an indium sheet.

It should be noted that the structure of the fourth thermal switch 40 may be set with reference to the structure of the first thermal switch 4, which is not described herein.

Example IV

As shown in fig. 7, the present embodiment provides a cooling system and a superconducting magnet system, which are substantially the same as those of the third embodiment, and only have differences in partial arrangement, so that the present embodiment will not be repeated for the same structure as that of the third embodiment.

In this embodiment, the plurality of evaporation plates 43 are divided into at least two groups separately disposed, each group of evaporation plates 43 includes one evaporation plate 43 or at least two evaporation plates 43 stacked, two adjacent groups of evaporation plates 43 are disposed at intervals in the first direction, and each group of evaporation plates 43 has a second connection surface.

By providing at least two sets of evaporation plates 43, the contact position of the first thermal switch 4 with the load 10 to be cooled can be increased, thereby improving the cooling uniformity across the load 10 to be cooled, and further improving the cooling efficiency.

In the present embodiment, the first thermal switch 4 and the fourth thermal switch 40 are separately disposed, the first thermal switch 4 has two groups of evaporation plates 43, and two second connection surfaces of the two groups of evaporation plates 43 are respectively connected to the upper and lower ends of the cooled load 10, so as to reduce the cost while improving the cooling uniformity of the cooled load 10.

Example five

As shown in fig. 8, the present embodiment provides a cooling system and a superconducting magnet system, which are substantially the same as those of the third embodiment, and only have differences in partial arrangement, and the present embodiment does not provide a redundant description of the same structure as that of the third embodiment.

In this embodiment, the first thermal switch 4 and the fourth thermal switch 40 are integrally disposed, the evaporating plates 4 corresponding to the first thermal switch 4 and the fourth thermal switch 40 are disposed in a staggered manner, the condensing plates corresponding to the first thermal switch 4 and the fourth thermal switch 40 are disposed in a stacked manner, and the first thermal switch 4 and the fourth thermal switch 40 share a liquid injection joint. This arrangement can reduce the occupied space of the first thermal switch 4 and the fourth thermal switch 40, improve the structural compactness, and realize simultaneous liquid injection to the first thermal switch 4 and the fourth thermal switch 40.

It will be appreciated that in the present embodiment, the first thermal switch 4 may also be provided with two or more groups of evaporation plates 42, and each group of evaporation plates 42 is connected to the cooled load 10 to improve the cooling uniformity of the cooled load 10. The fourth thermal switch 40 may also be provided with two or more sets of evaporation plates, each set of evaporation plates being thermally connected to the primary radiation shield 2 to improve the uniformity with which the primary radiation shield 2 is cooled.

Example six

As shown in fig. 9, the present embodiment provides a cooling system and a superconducting magnet system, and the basic structure of the cooling system and the superconducting magnet system provided in the present embodiment is the same as that of the first embodiment, only a part of the basic structure is different, and the details of the first embodiment are not repeated.

In this embodiment, the refrigerator 3 has two cold heads 31, the two cold heads 31 are a primary cold head 31a and a secondary cold head 31b, respectively, and when the refrigerator 3 is operating normally, the final cooling temperature of the primary cold head 31a is higher than the final cooling temperature of the secondary cold head 31b, and the first thermal switch 4 is thermally connected to the secondary cold head 31 b.

The refrigerating system further comprises a second thermal switch 5, the second thermal switch 5 comprises a second low-temperature pulsating heat pipe, an evaporation section of the second low-temperature pulsating heat pipe is connected with the cooled load 10, a condensation section of the second low-temperature pulsating heat pipe is connected with the first-stage cold head 31a, and the triple point critical of a second working medium in the second low-temperature pulsating heat pipe is higher than the final refrigerating temperature of the first-stage cold head 31 a.

In the cooling system provided in this embodiment, since the critical temperature of the second low-temperature pulsating heat pipe is higher than the final cooling temperature of the first-stage cold head 31a, and the final cooling temperature of the first-stage cold head 31a is higher than the final coldest temperature of the second-stage cold head 31b, when the refrigerator 3 is not in operation, the working medium in the first low-temperature pulsating heat pipe 41 is in a gaseous state, at this time, the thermal resistance of the second thermal switch 5 is relatively high, and the second thermal switch 5 is in an off state; in the cooling process of the cooling system, the temperature of the first-stage cold head 31a is firstly reduced to the critical temperature of the second low-temperature pulsating heat pipe, the second working medium of the condensing section of the second low-temperature pulsating heat pipe is condensed into a liquid state, the second low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state, the heat conductivity coefficient is higher, the transfer effect is higher, the second thermal switch is in a conducting state, the cold quantity of the first-stage cold head 31a is transferred to the cooled load 10, the cooled load 10 is accelerated to cool down, and the time required by the cooled load 10 to be cooled to the preset working temperature is shortened, so that the operation efficiency of the cooling system is improved; after the cooled load 10 is cooled to the triple point temperature of the second working medium, the temperature of the condensing section of the second low-temperature pulsating heat pipe is reduced to below the triple point temperature of the second working medium along with the first-stage cold head 31a, the second working medium in the second low-temperature pulsating heat pipe is converted into a solid state, the flow is stopped, the thermal resistance is increased, the second thermal switch 5 is in an off state, the cooled load 10 conducts heat mainly through the first thermal switch 4, the temperature of the cooled load 10 is reduced along with the reduction of the temperature of the second-stage cold head 31b, and finally the cooled load 10 is cooled to a preset working temperature.

Meanwhile, in the running process of the cooled load 10, if the temperature of the cooled load 10 rises to the three-phase temperature of the second low-temperature pulsating heat pipe, the second working medium in the evaporation section of the second low-temperature pulsating heat pipe is melted into a liquid state, the second working medium in the second low-temperature pulsating heat pipe can be in a gas-liquid two-phase flow state by controlling the temperature of the first-stage cold head 31a, namely the second thermal switch 5 is conducted, the heat of the cooled load 10 is quickly transferred to the first-stage cold head 31a through the thermal switch 5, the heat conduction from the first thermal switch 5 to the first-stage cold head 31a is realized, the heat transfer efficiency is improved, the temperature rise of the cooled load 10 is avoided to be larger, the return of the cooled load 10 from the temperature rise state to the normal working state is effectively promoted, and the time of the cooled load 10 returning to the normal working state is shortened.

That is, the cooling system provided in this embodiment can realize the redundant design of the refrigerator 3, and at the same time, can increase the utilization of the cooling capacity of the refrigerator 3, improve the cooling efficiency of the cooled load 10, reduce the cooling time, and effectively improve the operation reliability of the cooling system and the superconducting magnet system.

The second working medium filled in the second low-temperature pulsating heat pipe is preferably nitrogen, and the cost is low. The working medium of the second low-temperature pulsating heat pipe can be argon, krypton, oxygen, ammonia, methane and the like, and the working medium of the first low-temperature pulsating heat pipe can also be helium, hydrogen, neon and the like. The first working medium in the first low-temperature pulsating heat pipe and the second working medium in the second low-temperature pulsating heat pipe may be specifically selected according to the preset working temperature required by the cooled load 10.

The structure of the second thermal switch 5 may be set with reference to the structure of the first thermal switch 4 in the first embodiment, the third embodiment or the fourth embodiment, and this embodiment will not be described again. The structure of the first thermal switch 4 in this embodiment may also be the structure of the thermal switch in the third embodiment and the fourth embodiment, which will not be described here again.

In this embodiment, the filling system and the filling method corresponding to the second low-temperature pulsating heat pipe may refer to the arrangement in the second embodiment, and this embodiment will not be described in detail.

Preferably, in the present embodiment, the primary coldhead 31a is thermally coupled to the primary radiation shield 2 to absorb thermal radiation from the environment to the primary radiation shield 2.

In this embodiment, the first stage cold head 31a is connected to the first stage radiation shield 2 through the fourth thermal switch 5, the fourth thermal switch 40 includes a fourth low-temperature pulsating heat pipe, an evaporation section of the fourth low-temperature pulsating heat pipe is thermally connected to the first stage radiation shield 2, a condensation section of the fourth low-temperature pulsating heat pipe is thermally connected to the first stage cold head 31a, and when the first stage cold head 31a is at a final cooling temperature, a fourth working medium in the fourth low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state. This arrangement ensures that when a particular refrigerator 3 is shut down or fails, the fourth thermal switch 40 corresponding to that refrigerator 3 is turned off, preventing heat from the refrigerator 3 from being transferred to the primary radiation shield 2.

That is, in this embodiment, the fourth working medium is different from the first working medium, and the triple point temperature of the fourth working medium is higher than the triple point temperature of the first working medium and lower than the triple point temperature of the second working medium. The type of the fourth working fluid may be determined according to the final cooling temperature of the primary cold head 31 a.

It should be noted that, a heat insulating layer is wrapped outside the superconducting magnet, outside the primary radiation shield 2, outside the first thermal switch 4, outside the second thermal switch 5, outside the fourth thermal switch 40, outside the primary cold head 31a and/or the secondary cold head 31b, and the heat insulating layer is preferably made of MLI material, so as to improve heat insulating effect and reduce radiation and heat leakage. The heat insulating layer preferably has at least 20 layers to enhance the heat insulating effect.

Further, a filling system is correspondingly arranged on each first thermal switch 4, each second thermal switch 5 and each fourth thermal switch 40 respectively, so as to realize independent filling control of each thermal switch.

Example seven

As shown in fig. 10, the present embodiment provides a cooling system and a superconducting magnet system, and the cooling system provided in the present embodiment is substantially the same as the cooling system in the fifth embodiment, only has a difference in part of the structure, and the present embodiment will not be described in detail in the same manner as in the sixth embodiment.

In the present embodiment, the primary cold head 31a is thermally connected to the primary radiation shield 2 through the fourth thermal switch 40, and the secondary cold head 31b is thermally connected to the cooled load 10 through the first thermal switch 4.

That is, the first-stage coldhead 31a provided in the present embodiment is not connected to the load 10 to be cooled, or is connected to the load 10 to be cooled through another low-temperature thermal switch, and the fourth thermal switch 40 is connected to the first-stage radiation shield 2, so that the first-stage coldhead 31a can absorb heat at the first-stage radiation shield 2 when the refrigerator 3 is in operation, reducing the influence of heat radiation on the load 10 to be cooled. When the refrigerator 3 stops operating or fails, the temperatures of the primary cold head 31a and the secondary cold head 31b corresponding to the refrigerator 3 are raised, and the first thermal switch 4 and the fourth thermal switch are both in an off state.

Example eight

As shown in fig. 11, this embodiment provides a cooling system and a superconducting magnet system, where the cooling system of the superconducting magnet system provided in this embodiment is a further improvement of the cooling system in any of the foregoing embodiments, and the structure of this embodiment that is the same as that of the foregoing embodiment is not repeated.

In this embodiment, the primary radiation shield 2 has a secondary radiation shield 9 suspended therein, and the cooled load 10 is located inside the secondary radiation shield 9. That is, by providing the secondary radiation shield 9 inside the primary radiation shield 2 and disposing the load to be cooled 10 inside the secondary radiation shield 9, it is possible to better restrict the heat radiation at the vacuum enclosure 1 to the load to be cooled 10.

The primary cold head 31a is thermally connected with the primary radiation shield 2 to absorb radiation heat leakage of the primary radiation shield 2; the secondary coldhead 31b is thermally coupled to the secondary radiation shield 9 to absorb radiant heat leakage from the secondary radiation shield 9 and to maintain the secondary radiation shield 9 at the same temperature as the load 10 being cooled, facilitating better maintenance of the operating environment temperature of the load 10 being cooled.

Preferably, in the present embodiment, the secondary radiation protection screen 9 is connected to the secondary cold head 31b through the third thermal switch 30, the third thermal switch 30 includes a third low-temperature pulsating heat pipe, an evaporation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary radiation protection screen 9, a condensation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary cold head 31b, and when the secondary cold head 31b is at a final refrigeration temperature, a third working medium in the third low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

By the arrangement, when one refrigerator 4 is stopped or fails, the first-stage thermal switch 4 and the third thermal switch 30 corresponding to the refrigerator 4 are disconnected, so that heat on the refrigerator 4 is prevented from being transferred to the second-stage radiation shield 9 to influence the temperature control of the second-stage radiation shield 4, and the refrigerating effect is improved.

In other embodiments, the secondary coldhead 31b may also be thermally coupled directly to the secondary radiation shield 9 to reduce cost. In another embodiment, the two refrigerators 3 may be a main refrigerator and a standby refrigerator, respectively, the secondary cold head 31b of the main refrigerator is directly thermally connected to the secondary radiation shield 9, and the secondary cold head 31b of the standby refrigerator may be thermally connected to the secondary radiation shield 9 through the third thermal switch 30.

In this embodiment, the third working medium in the third low-temperature pulsating heat pipe is the same as the first working medium in the first low-temperature pulsating heat pipe. The three-phase temperature of the second working medium in the second low-temperature pulsating heat pipe is higher than that in the fourth low-temperature pulsating heat pipe, and the three-phase temperature in the fourth low-temperature pulsating heat pipe is higher than that of the first working medium.

In this embodiment, the second thermal switch 5 and the third thermal switch 30 may be set in any of the second embodiment to the fifth embodiment, that is, the second thermal switch 5 and the third thermal switch 30 may be set separately or may be set integrally, which is not described in detail in this embodiment.

Preferably, the outer parts of the primary radiation protection screen 2 and the secondary radiation protection screen 9 are respectively coated with a heat insulation layer, and the heat insulation layers are preferably made of high-vacuum multi-layer heat insulation materials so as to further reduce radiation heat leakage.

Further, the primary cold head 31a, the secondary cold head 31b, the first thermal switch 4, the second thermal switch 5, the third thermal switch 30 and/or the fourth thermal switch 40 are all wrapped with heat insulation layers, and the heat insulation layers are preferably made of high-vacuum multi-layer heat insulation materials.

Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims

1. A cooling system for cooling a cooled load (10), the cooling system comprising a vacuum hood (1), a refrigerator (3) and a first thermal switch (4), wherein the number of the refrigerators (3) is at least two, each refrigerator (3) is provided with a cold head (31), the first thermal switch (4) is arranged in one-to-one correspondence with the refrigerator (3), and the cooled load (10), the cold heads (31) and the first thermal switch (4) are all positioned in the vacuum hood (1);

the first thermal switch (4) comprises a first low-temperature pulsating heat pipe (41), an evaporation section of the first low-temperature pulsating heat pipe (41) is connected with the cooled load (10), a condensation section of the first low-temperature pulsating heat pipe (41) is connected with the cold head (31), and when the cold head (31) is at a final refrigeration temperature, a first working medium in the first low-temperature pulsating heat pipe (41) is in a two-phase flow state.

2. The cooling system according to claim 1, further comprising a primary radiation shield (2), the primary radiation shield (2) being suspended within the vacuum enclosure (1), the cooled load (10) being located inside the primary radiation shield (2), the coldhead (31) being thermally connected to the primary radiation shield (2).

3. The cooling system according to claim 2, characterized in that each of the refrigerators (3) comprises two cold heads (31), the two cold heads (31) being a primary cold head (31 a) and a secondary cold head (31 b), respectively, the condensation section of the first cryopulsation heat pipe (41) being connected to the secondary cold head (31 b), the primary cold head (31 a) being thermally connected to the primary radiation shield (2);

the cooling system further comprises a second thermal switch (5), the second thermal switch (5) comprises a second low-temperature pulsating heat pipe, a condensation section of the second low-temperature pulsating heat pipe is thermally connected with the first-stage cold head (31 a), an evaporation section of the second low-temperature pulsating heat pipe is thermally connected with the cooled load (10), and the three-phase point temperature of a second working medium in the second low-temperature pulsating heat pipe is higher than the final refrigeration temperature of the first-stage cold head (31 a).

4. A cooling system according to claim 3, characterized in that the primary radiation shield (2) is internally suspended with a secondary radiation shield (9), the cooled load (10) is located inside the secondary radiation shield (9), and the secondary coldhead (31 b) is thermally connected to the secondary radiation shield (9).

5. The cooling system according to claim 4, wherein the secondary radiation shield (9) is connected to the secondary cold head (31 b) through a third thermal switch (30), the third thermal switch (30) includes a third low-temperature pulsating heat pipe, an evaporation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary radiation shield (9), a condensation section of the third low-temperature pulsating heat pipe is thermally connected to the secondary cold head (31 b), and when the secondary cold head (31 b) is at a final cooling temperature, a third working fluid in the third low-temperature pulsating heat pipe is in a gas-liquid two-phase flow state.

6. The cooling system according to any one of claims 2-5, wherein the cold head (31) is thermally connected to the primary radiation shield (2) through a fourth thermal switch (40), the fourth thermal switch (40) comprising a fourth low temperature pulsating heat pipe, an evaporation section of the fourth low temperature pulsating heat pipe being thermally connected to the primary radiation shield (2), a condensation section of the fourth low temperature pulsating heat pipe being thermally connected to the cold head (31), a fourth working substance within the fourth low temperature pulsating heat pipe being in a gas-liquid two phase flow state when the cold head (31) is at a final refrigeration temperature.

7. The cooling system according to any one of claims 1-5, further comprising a first filling system (20), wherein the first filling system (20) is configured to fill the first low-temperature pulsating heat pipe (41) with a first working fluid, and the first filling system (20) is arranged in a one-to-one correspondence with the first thermal switch (4).

8. The cooling system of any one of claims 3-5, wherein the first working fluid is helium, hydrogen, neon, or nitrogen;

9. The cooling system according to any one of claims 1-5, characterized in that the outer surface of the cold head (31) and/or the first thermal switch (4) is covered with a heat insulating layer;

And/or the first thermal switch (4) has a first connection surface thermally connected to the cold head (31) and a second connection surface thermally connected to the cooled load (10), wherein the first connection surface and/or the second connection surface is/are provided with a thermally conductive coating and/or a thermally conductive sheet.

10. A superconducting magnet system comprising a superconducting magnet, further comprising a cooling system according to any of claims 1-9, the superconducting magnet being the cooled load (10).