CN116344150A - A kind of cooling system, superconducting magnet system and cooling method - Google Patents

Abstract

The invention belongs to the technical field of superconducting magnets, and particularly discloses a cooling system, a superconducting magnet system and a cooling method. The cooling system comprises a vacuum cover, a refrigerator, a thermal switch and a temperature control device, wherein the refrigerator is provided with a first-stage cold head and a second-stage cold head, the cooled load, the first-stage cold head and the second-stage cold head are all positioned in the vacuum cover, the thermal switch comprises a first low-temperature pulsating heat pipe, a condensation section of the first low-temperature pulsating heat pipe is thermally connected with the first-stage cold head, an evaporation section of the first low-temperature pulsating heat pipe is connected with the cooled load, a heat conduction piece is connected between the second-stage cold head and the cooled load, the final refrigeration temperature of the first-stage cold head is lower than the three-phase temperature of a working medium in the first low-temperature pulsating heat, and the temperature control device is used for controlling the preset working temperatures of the first-stage cold head and the second-stage cold head. The invention can improve the cooling efficiency of the cooled load, reduce the harm caused by the overhigh temperature rise in the working process of the cooled load, and improve the operation safety and reliability of the cooling system and the superconducting magnet system.

Description

A kind of cooling system, superconducting magnet system and cooling method

technical field

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

Background technique

The wide application of superconductivity has always been inseparable from low temperature. Only by cooling the magnet below the superconducting transition temperature can superconducting characteristics be realized. Once the superconducting transition temperature is exceeded, the huge Joule heat generated by the quench may burn the superconducting wire and even cause an explosion accident. . At present, the most widely used superconducting magnets are low-temperature superconducting magnets, whose superconducting transition temperature is very low. For example, the superconducting transition temperature of NbTi is 9.6K, and the superconducting transition temperature of Nb ₃ Sn is 18.1K. The superconducting transition temperature of the superconducting magnet in the liquid nitrogen temperature region of the superconducting magnet also needs to be approximately 77K. Therefore, ensuring the stable operation of superconducting magnets in a low temperature environment is the key to the application of superconducting technology.

With the development of small refrigerator technology, the use of refrigerators to directly cool superconducting magnet systems is becoming more and more widely used. Compared with the traditional low-temperature liquid immersion method, it has the advantages of no liquid helium consumption, low cost, small size, compact structure and easy to use. and maintenance advantages. A typical cooling system of a refrigerator includes a cooled load, a radiation-proof cold shield, a refrigerator, a vacuum container and other accessories. The radiation-proof cold shield is connected to the primary cold head of the refrigerator, and the cooled load is connected to the secondary cold head. When the cooling system is running, the chiller secondary cold head will reach the minimum temperature of the closed cycle chiller.

Since the cooling power of the first-stage cold head is much higher than that of the second-stage cold head, the temperature of the first-stage cold head will soon approach the final temperature, and when the heat capacity of the cooled load is large, the second-stage cold head may require a longer time to cool the cooling load to the minimum temperature. In order to shorten the cooling time of the cooled load to the lowest temperature, a low-temperature thermal switch can be installed between the primary cold head of the refrigerator and the cooled load. The large cooling capacity of the head first pre-cools the load to be cooled. When the minimum temperature of the first-stage cold head is reached, the low-temperature thermal switch must be interrupted, so that the second-level cold head can continue to cool the cooled load to a lower temperature.

Low temperature thermal switches generally include mechanical contact thermal switches, superconducting thermal switches, air gap thermal switches, and magnetoresistive thermal switches. The mechanical contact thermal switch uses the contact or disconnection of the movable surface to switch the thermal switch state. It has the advantages of unlimited working temperature range and complete disconnection, but it is difficult to achieve high thermal conductivity due to the pressure limit. And it is necessary to set up an additional driving structure to drive the thermal switch to move, which is difficult to design and takes up a large space; the principle of the superconducting thermal switch is to use the difference in thermal conductivity of the superconducting material in the normal state and the superconducting state to conduct heat transfer. The switching of the switch has a high thermal conductivity when it is turned on, but it is only suitable for the temperature range below 0.5K, and an additional magnetic field acting on the superconducting thermal switch is required, which increases the complexity and cost of the system. At the same time, the The magneto-caloric effect when the thermal switch applies a magnetic field will also generate heat, and there will be heat leakage when the thermal switch is turned off; the working principle of the air-gap thermal switch is to place an adsorbent on the side with a lower temperature. When it is low, the adsorbent adsorbs gas, so that the air pressure in the blade gap is low, and the thermal switch is in the off state. As the temperature on this side rises, the adsorbent desorbs, the gas enters the gap, and the thermal switch is in the conductive state, which can be driven passively. However, the preset operating temperature range is relatively high, and it requires precision manufacturing, and the cost is high; the principle of the magnetoresistive thermal switch is to use the magnetoresistance effect of some metals. When a magnetic field is applied, it is subjected to the Lorentz force, and the hot electron The movement of the material will be suppressed, and the thermal conductivity of the material can be reduced to the level where only phonons conduct heat, so its switch is relatively large, but the magnetoresistive thermal switch is limited to extremely low temperature applications, requiring a large magnetic field and corresponding electromagnets, The cost is high, and the floor space is large. At the same time, the magnetoresistive material is too brittle and easy to be damaged, resulting in increased processing and maintenance costs.

Contents of the invention

An object of the present invention is to provide a cooling system that can improve the cooling efficiency of the load to be cooled, increase the switching ratio of the thermal switch and the thermal conductivity when it is turned on, and reduce the footprint and installation of the thermal switch. Cost, improve the structure compactness, operation safety and operation stability of the cooling system.

Another object of the present invention is to provide a superconducting magnet system, which can improve the structural compactness of the superconducting magnet system, and can improve the operating efficiency, operating safety and operating reliability of the superconducting magnet system.

Another object of the present invention is to provide a cooling method, which can improve the cooling efficiency of the load to be cooled, reduce the cooling time, and improve the operation safety and efficiency of the load to be cooled.

To achieve the above object, the present invention adopts the following technical solutions:

A cooling system for cooling a cooled load, the cooling system includes a vacuum cover, a refrigerator, a thermal switch and a temperature control device, the refrigerator has a primary cold head and a secondary cold head, the cooled load , the primary cold head and the secondary cold head are located in the vacuum cover, the thermal switch includes a first low temperature pulsating heat pipe, the condensation section of the first low temperature pulsating heat pipe is connected to the primary cold head Thermally connected, the evaporation section of the first low-temperature pulsating heat pipe is connected to the cooled load, a heat conduction element is connected between the secondary cold head and the cooled load, and the final cooling temperature of the primary cold head is Lower than the triple point temperature inside the first low-temperature pulsating heat pipe, the temperature control device is used to control the refrigeration temperature of the primary cold head and the secondary cold head.

As an optional technical solution of the cooling system, the thermal switch includes an evaporation plate and a condensation plate, the condensation section of the first low-temperature pulsating heat pipe is fixed on the condensation plate, and the evaporation plate and the condensation plate are composed of Made of heat-conducting metal, the evaporation section of the first low-temperature pulsating heat pipe is fixed to the evaporation plate, the condensation plate is connected to the primary cold head, and the evaporation plate is connected to the cooled load.

As an optional technical solution of the cooling system, the thermal switch includes at least two first low-temperature pulsating heat pipes, and the evaporation plate and the condensation plate are arranged in one-to-one correspondence with the first low-temperature pulsating heat pipes;

All the condensing plates are stacked and fixedly connected, and one of the condensing plates located on the outside is connected to the primary cold head;

All the evaporating plates are divided into at least two groups that are arranged separately, and each group of evaporating plates includes at least one evaporating plate or a plurality of evaporating plates stacked and fixedly arranged, and each group of evaporating plates is located on the outside One of the evaporation plates is connected to the load to be cooled.

As an optional technical solution of the cooling system, the cooling system also includes a primary radiation protection screen, the primary radiation protection screen is suspended in the vacuum cover, and the cooled load is suspended in the one Inside the primary radiation shield, the primary cold head is thermally connected to the primary radiation shield.

As an optional technical solution of the cooling system, the cooling system also includes a secondary radiation protection screen, the secondary radiation protection screen is suspended inside the primary radiation protection screen, and the cooled load is suspended on the Inside the secondary radiation shield, the secondary cold head is thermally connected to the secondary radiation shield.

As an optional technical solution of the cooling system, the heat conduction element includes a second low-temperature pulsating heat pipe, the evaporation section of the second low-temperature pulsating heat pipe is connected to the load to be cooled, and the condensation section of the second low-temperature pulsating heat pipe It is thermally connected with the secondary cold head, and the final cooling temperature of the secondary cold head is between the triple point temperature and the critical point temperature of the working medium in the second low-temperature pulsating heat pipe.

As an optional technical solution of the cooling system, the working fluid in the first low-temperature pulsating heat pipe is argon, nitrogen, oxygen or methane;

The working fluid in the second low temperature pulsating heat pipe is helium, hydrogen or neon.

As an optional technical solution of the cooling system, there are at least two refrigerators, and the thermal switch and the heat conduction member are provided in one-to-one correspondence with the refrigerators.

As an optional technical solution of the cooling system, the outer surface of the primary cold head, the secondary cold head, the thermal switch, the load to be cooled and/or the heat conduction member is covered with multiple layers of insulating material ;

And/or, the thermal switch has a first connection surface and a second connection surface, the first connection surface is thermally connected to the primary cold head, and the second connection surface is thermally connected to the cooled load, The first connecting surface and/or the second connecting surface is provided with a thermally conductive coating and/or a thermally conductive sheet.

A superconducting magnet system includes a superconducting magnet, and further includes the above-mentioned cooling system, the superconducting magnet being the load to be cooled.

A cooling method applied to the above cooling system, the cooling method comprising:

evacuating the inside of the vacuum cover until the vacuum value is less than a preset vacuum value;

start the refrigerator;

When the temperature of the first-stage cold head reaches the gas-liquid two-phase flow temperature zone of the first low-temperature pulsating heat pipe, control the temperature of the first-stage cold head to maintain the gas-liquid two-phase flow temperature zone, so that The thermal switch is in a conduction state;

When the temperature of the cooled load is lower than the triple point temperature of the thermal switch, stop the temperature control of the primary cold head, so that the temperature of the primary cold head drops to the first low temperature pulse The temperature of the triple point of the working fluid in the heat pipe causes the thermal switch to be disconnected.

As an optional technical solution of the cooling method, the cooling method also includes:

During the operation of the load to be cooled, when the temperature of the load to be cooled rises to the gas-liquid two-phase flow temperature zone of the first low-temperature pulsating heat pipe, the temperature of the primary cold head is adjusted to the specified The gas-liquid two-phase flow temperature zone is set so that the thermal switch changes from an off state to an on state.

The beneficial effects of the present invention are:

The cooling system provided by the present invention includes the first low-temperature pulsating heat pipe through the use of a thermal switch, which can effectively utilize the cooling capacity of the first-stage cold head of the refrigerator, accelerate the cooling of the cooled load to the preset working temperature, improve the efficiency of the cooling system, and can also Shorten the time for the cooled load to recover from the temperature rise state to the normal working state, and improve the operation safety and reliability of the cooling system; at the same time, when the first low-temperature pulsating heat pipe is turned on, the thermal conductivity is several orders of magnitude higher than that of the heat-conducting metal, and the heat transfer coefficient is higher than that of the heat-conducting metal. The thermal efficiency is high, which can effectively improve the cooling efficiency of the cooled load and the recovery efficiency of the cooled load. At the same time, the switch is relatively large, which can effectively ensure the thermal insulation performance when the thermal switch is turned off, and ensure the reliability of the cooling system; moreover, due to The thermal switch can automatically disconnect and conduct according to the temperature change without mechanical and electromagnetic drive, which reduces the difficulty of control, improves the control accuracy, ensures the reliability of the thermal switch, and reduces the structural complexity and space occupancy of the thermal switch, reducing the The cost of the cooling system; moreover, the first low-temperature pulsating heat pipe is small in size, light in weight, and has a long heat transfer distance, and can be bent and arranged, so that the first low-temperature pulsating heat pipe can be easily integrated into a In the structure, the structure compactness of the cooling system is improved.

The superconducting magnet system provided by the present invention, by adopting the above-mentioned cooling system, can reduce the time for the superconducting magnet to be pre-cooled to the preset working temperature, improve the operating efficiency of the superconducting magnet system, and shorten the recovery time of the superconducting magnet to The time in the superconducting state improves the operation safety and reliability of the superconducting magnet system; at the same time, because the thermal switch occupies a small space and can be arranged flexibly, the compact structure of the superconducting magnet system can be effectively improved.

The cooling method provided by the invention can improve the cooling efficiency of the load to be cooled, thereby improving the working efficiency of the load to be cooled, and improving the operation safety and reliability of the load to be cooled.

Description of drawings

Fig. 1 is a schematic structural diagram of a superconducting magnet system provided by Embodiment 1 of the present invention;

Fig. 2 is a schematic diagram of a pulsating heat pipe provided by Embodiment 1 of the present invention;

Fig. 3 is a schematic structural diagram of a liquid filling system provided by Embodiment 2 of the present invention;

Fig. 4 is a schematic structural diagram of a thermal switch provided in Embodiment 3 of the present invention;

Fig. 5 is a top view of the structure in Fig. 4;

Fig. 6 is a side view of the structure in Fig. 4;

Fig. 7 is a schematic structural diagram of a thermal switch provided in Embodiment 4 of the present invention;

Fig. 8 is a schematic structural diagram of a superconducting magnet system provided in Embodiment 5 of the present invention;

Fig. 9 is a schematic structural diagram of a superconducting magnet system provided by Embodiment 6 of the present invention;

Fig. 10 is a schematic structural diagram of a superconducting magnet provided by Embodiment 7 of the present invention.

The markings in the figure are as follows:

1. Vacuum cover; 11. Outer cylinder; 12. Flange; 2. Primary radiation shield; 3. Refrigerator; 31. Primary cold head; 32. Secondary cold head; 4. Thermal switch; 41 , the first low-temperature pulsating heat pipe; 411, the parallel pipe part; 412, the bending part; 413, the joint pipe part; 42, the condensation plate; 421, the first positioning groove; 43, the evaporation plate; 431, the second positioning groove; 44 , liquid injection joint; 5, heat conduction parts; 6, power supply components; 61, superconducting wires; 62, high temperature superconducting current leads; 63, internal current wiring components; 64, external current wiring components; 65, superconducting excitation power supply; 7 , the first support structure; 8, the second support structure; 9, the secondary radiation shield; 10, the load to be cooled; 101, the room temperature hole; 20, the liquid filling system; 201, the buffer tank; 202, the gas storage bottle; 203 , Molecular pump unit; 204, the first shut-off valve; 205, the second shut-off valve; 206, the third shut-off valve; 207, the first pressure sensor; 208, the second pressure sensor; 209, the filling pipe;

100a, evaporation section; 100b, condensation section; 100c, adiabatic section; 100d, gas plug; 100e, liquid plug.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, only some structures related to the present invention are shown in the drawings but not all structures.

In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected" and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integrated ; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components or the interaction relationship between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

In the present invention, unless otherwise clearly specified and limited, a first feature being "on" or "under" a second feature may include direct contact between the first and second features, and may also include the first and second features Not in direct contact but through another characteristic contact between them. Moreover, "above", "above" and "above" the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

In the description of this embodiment, the terms "up", "down", "right", and other orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operations, rather than indicating Or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first" and "second" are only used to distinguish in description, and have no special meaning.

Embodiment one

As shown in Figure 1, this embodiment provides a cooling system that can cool the cooled load 10 to a preset operating temperature, so that the cooled load 10 can be kept running in a low temperature environment, ensuring the safe operation of the cooled load 10 sex and reliability. Wherein, the cooled load 10 may be a superconducting magnet or other devices with large specific heat capacity and need to operate in a low temperature environment.

Specifically, the cooling system includes a vacuum cover 1, a refrigerator 3, a thermal switch 4 and a temperature control device. The refrigerator 3 has a primary cold head 31 and a secondary cold head 32, the load to be cooled 10, the primary cold head 31 and the secondary cold head 32 are all located in the vacuum cover 1, and the thermal switch 4 includes a first low-temperature pulsating heat pipe 41, The condensation section of the first low-temperature pulsating heat pipe 41 is thermally connected to the primary cold head 31 , the evaporation section of the first low-temperature pulsating heat pipe 41 is connected to the load to be cooled 10 , and a heat conduction member is connected between the secondary cold head 32 and the load to be cooled 10 5. The triple point temperature of the working medium in the first low-temperature pulsating heat pipe 41 (hereinafter referred to as the first working medium) is higher than the final cooling temperature of the first-stage cold head 31, and the temperature control device is used to control the first-stage cold head 31 and the second-stage cold head. The cooling temperature of the cold head 32. Wherein, the final cooling temperature is the temperature that the primary cooling head 31 can reach when the temperature of the secondary cooling head 32 drops to the target cooling temperature.

In the cooling system provided by this embodiment, when the refrigerator 3 is not working, the working medium in the first low-temperature pulsating heat pipe 41 is in a gaseous state, and at this time, the thermal resistance of the thermal switch 4 is relatively large, and the thermal switch 4 is in an off state; During the cooling process of the system, the temperature of the primary cold head 31 first drops below the critical temperature of the first low-temperature pulsating heat pipe 41, the working fluid in the condensation section of the first low-temperature pulsating heat pipe 41 is condensed into a liquid state, and the first low-temperature pulsating heat pipe 41 is in the In the state of partial gas-liquid two-phase flow, the effective thermal conductivity is high, so that the thermal switch 4 is in a conducting state, and the cooling capacity of the primary cold head 31 is transferred to the cooled load 10, which accelerates the cooling of the cooled load 10 and shortens the cooling time of the cooled load. 10 the time required for cooling to the preset operating temperature, thereby improving the operating efficiency of the cooling system; when the cooled load 10 is cooled to a temperature lower than the triple point, the temperature of the condensation section of the first low-temperature pulsating heat pipe 41 increases with the temperature of the first-stage cold head 31 When the temperature drops below the triple point, the working fluid in the first low-temperature pulsating heat pipe 41 condenses into a solid state, the flow stops, the thermal resistance increases, and the thermal switch 4 is turned off. The cold head 32 conducts heat, and the temperature of the load to be cooled 10 decreases as the temperature of the secondary cold head 32 decreases, and finally the load to be cooled 10 is cooled to a preset working temperature.

At the same time, during the operation of the cooled load 10, if the temperature of the cooled load 10 rises to a temperature higher than the triple point temperature of the first low-temperature pulsating heat pipe 41, the working fluid in the evaporation section of the first low-temperature pulsating heat pipe 41 will change from solid to In the gas-liquid two-phase flow state, by controlling the temperature of the primary cold head 31, the first working medium in the condensation section of the first low-temperature pulsating heat pipe 41 can also be in the gas-liquid two-phase flow state, that is, the thermal switch 4 is turned on, and the The heat of the cooled load 10 is quickly transferred to the first-stage cold head 31 through the thermal switch 4, so as to realize the heat conduction between the thermal switch 4 and the heat conduction member 5, improve the heat transfer efficiency, and avoid the large temperature rise of the cooled load 10. Effectively promote the recovery of the cooled load 10 from the temperature rising state to the normal working state, and shorten the time for the cooled load 10 to return to the normal working state.

That is, by making the thermal switch 4 include the first low-temperature pulsating heat pipe 41, the cooling capacity of the primary cold head 31 of the refrigerator 3 can be effectively used, and the cooling of the cooled load 10 to the preset operating temperature can be accelerated, and the efficiency of the cooling system can be improved. Shorten the time for the cooled load 10 to return from the temperature rise state to the normal working state, and improve the operation safety and reliability of the cooling system; at the same time, when the first low-temperature pulsating heat pipe 41 is turned on, the thermal conductivity is several orders of magnitude higher than that of heat-conducting metals , the heat transfer efficiency is high, which can effectively improve the cooling efficiency of the cooled load 10. At the same time, the switch is relatively large (can reach more than 2500), which can effectively ensure the thermal insulation performance when the thermal switch 4 is turned off, and ensure the reliability of the cooling system; Moreover, since the thermal switch 4 can be automatically disconnected and turned on according to temperature changes, no mechanical or electromagnetic drive is required, the difficulty of control is reduced, the control accuracy is improved, the reliability of the thermal switch 4 is ensured, and the structural complexity of the thermal switch 4 is reduced at the same time and space occupancy, reducing the cost of the cooling system; moreover, the first low-temperature pulsating heat pipe 41 is small in size, light in weight, and has a long heat transfer distance, and can be bent and arranged so that the first low-temperature pulsating heat pipe 41 can be easily integrated To increase the compactness of the cooling system in structures with strict mass and space constraints.

As shown in Figure 2, it is worth explaining that the pulsating heat pipe is a passive heat transfer device, which is formed by repeatedly bending a metal capillary tube with a small inner diameter, generally 0.5-3 mm, between the hot end and the cold end. Serpentine tubular structure filled with two-phase fluid. Since the tube diameter is small enough, the capillary action is dominant, and the surface tension causes the working fluid to form gas plugs 100d and liquid plugs 100e randomly and alternately distributed in the capillary.

The pulsating heat pipe generally includes a condensing section 100b, an evaporating section 100a, and an adiabatic section 100c between the condensing section 100b and the evaporating section 100a. During the operation of the pulsating heat pipe, a heat load is applied to the evaporating section 100a, and the working fluid located in the evaporating section 100a absorbs heat, evaporates inside the liquid or on the surface of the liquid film, generates new bubbles or increases the volume of the original bubbles, resulting in gas As the length of the plug 100d increases, the pressure in the evaporating section 100a increases; at the same time, a cooling load is applied to the condensing section 100b, and the gaseous working medium in the condensing section 100b liquefies and releases heat to become a liquid working medium, so that the air bubbles in the condensing section 100b decrease. small or disappear, and the pressure in the condensation section 100b decreases. That is, the temperature difference between the evaporating section 100a and the condensing section 100b of the pulsating heat pipe produces a pressure difference that pushes the working fluid to flow from the evaporating section 100a to the condensing section 100b. There is a pressure imbalance between the tubes, thereby pushing the working medium to pulsate or lead to circulate in the tubes, and transfer heat through the latent heat of the gas-liquid phase transition and the sensible heat when the liquid plug 100e flows. That is, the oscillating fluid flow and heat transfer in the pulsating heat pipe are driven entirely by the transient pressure difference caused by local evaporation and condensation, requiring no mechanical power output, and having no moving parts, thus having high reliability. At the same time, compared with other types of heat pipes, the gas-liquid two phases of the pulsating heat pipe usually flow in the same direction, and there is no problem that the gas hinders the liquid backflow. In addition to the phase change heat transfer, the forced convection heat transfer between the working fluid and the tube wall is also very significant. , with a stronger heat transfer capability.

The working fluid in the pulsating heat pipe is a working fluid with high thermal conductivity, and the low-temperature pulsating heat pipe is a pulsating heat pipe with a lower critical temperature of the working fluid in the tube. In this embodiment, the first working fluid is preferably nitrogen, the cost is relatively low, and the gas-liquid saturation temperature is about 77K under normal pressure, and it is easy to control the temperature of the primary cold head 31 to the liquid nitrogen saturation temperature during the cooling process. In other embodiments, according to the preset working temperature of the load to be cooled 10 and the final cooling temperature that the primary cold head 31 can reach, the first working fluid can also be selected as argon, oxygen, methane or other low-temperature pulsating heat pipe working fluid .

In this embodiment, the condensing section can be directly connected to the primary cold head 31, and/or the evaporating section can be directly connected to the cooled load 10, and the condensing section and/or evaporating section can also be fixed on a metal plate with high thermal conductivity , and then connect the metal plate with the corresponding primary cold head 31 or the load to be cooled 10 .

It can be understood that, in this embodiment, the adiabatic section, the evaporation section and/or the condensation section of the first low temperature pulsating heat pipe 41 can be arranged vertically or bent to suit the first low temperature pulsating heat pipe 41 and the first stage. The connection between the cold head 31 and the load to be cooled 10 shall prevail, which is not specifically limited in the present invention.

The thermal switch 4 has a first connection surface and a second connection surface, the first connection surface is thermally connected to the primary cold head 31, and the second connection surface is thermally connected to the cooled load 10, in order to improve heat conduction efficiency, the first connection surface and/or Or the second connection surface is provided with a heat conduction structure, and the heat conduction structure includes a heat conduction coating and/or a heat conduction sheet, so as to increase the thermal conductivity of the connection and reduce the contact thermal resistance. Preferably, the heat conduction layer is an Apiezon N high heat conduction grease layer, and the heat conduction sheet is an indium sheet.

As shown in Figure 1, the refrigerator 3 is preferably a GM refrigerator or a pulse tube refrigerator. Exemplarily, the primary cold head 31 can provide about 35W cooling capacity at 50K, and the secondary cold head 32 can usually provide a cooling capacity of about 35W at 4.2K. Provide about 1.5W cooling capacity. However, it can be understood that the final cooling temperature that can be reached by the primary cold head 31 of the refrigerator 3 and the target cooling temperature that can be reached by the secondary cold head 32 can be specifically determined according to the preset working 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 repeated in this embodiment.

In this embodiment, the vacuum cover 1 includes an outer cylinder 11 with openings at both ends and flanges 12 mounted on the upper and lower ends of the outer cylinder 11. The flange 12 is detachably connected to the outer cylinder 11 and seals the outer cylinder. The corresponding port of the body 11. The structural arrangement of the vacuum cover 1 facilitates the disassembly and assembly of the internal structure of the vacuum cover 1 and improves the convenience of disassembly and maintenance of the cooling system. In other embodiments, only the upper end of the outer cylinder 11 may be open, that is, one flange 12 is provided on the upper end of the outer cylinder 11 .

The vacuum cover 1 is preferably made of non-magnetic stainless steel to avoid corrosion and improve the support stability of its internal structure. The outer cylinder 11 can 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 also includes a vacuum device, which is used to vacuum the inner space of the vacuum cover 1 . The flange 12 on the upper end of the vacuum cover 1 is provided with an aviation socket and a vacuum pumping port. The vacuum pumping device is located outside the vacuum cover 1, and the inside of the vacuum cover 1 is vacuumed through the vacuum pumping port, thereby reducing the heat conduction of the gas.

In order to further improve the cooling efficiency of the cooled load 10, the cooling system also includes a primary radiation shield 2, the primary radiation shield 2 is suspended in the vacuum cover 1, and the cooled load 10 is suspended on the primary radiation shield 2 interior. The primary radiation shield 2 is used to reduce the heat radiation from the outside of the vacuum cover 1 to the load to be cooled 10 and reduce the interference of the external environment to the load to be cooled 10 .

The primary radiation protection screen 2 is preferably suspended in the vacuum cover 1 by the first support structure 7 , and the cooled load 10 is suspended in the primary radiation protection screen 2 through the second support structure 8 . The setting of the first support structure 7 and the second support structure 8 can refer to the prior art, and can be made of high strength and low thermal conductivity materials, such as G10 glass fiber reinforced plastics, which is not limited in the present invention. The primary radiation shield 2 is preferably made of oxygen-free high-purity copper.

The primary radiation shield 2 is preferably thermally connected to the primary cold head 31, so that the temperature of the primary radiation shield 2 is close to the temperature of the primary cold head 31, and the radiation heat leakage from the vacuum cover 1 and the external environment to the cooled load 10 is reduced.

In this embodiment, the heat conducting member 5 is a metal member, and the material of the metal member is preferably made of pure copper or other metal materials with high thermal conductivity. That is, in an embodiment, the heat conducting member 5 may be a conventional copper braid structure.

In order to reduce radiation heat leakage, the outer surface of the first-level radiation shield 2, the outer surface of the thermal switch 4, the first-level cold head 31, the second-level cold head 32, the cooled load 10 and/or the outer surface of the heat-conducting member 5 are wrapped with a heat-insulating layer. The layers are preferably made of high-vacuum multi-layer insulation (Multi-Layer Insulation, MLI).

Further, the cooling system further includes a liquid filling system, which is used to fill the first low temperature pulsating heat pipe 41 with working fluid. The structure of the liquid filling system and the liquid injection method of the first low temperature pulsating heat pipe 41 can refer to the prior art, which is not limited in this embodiment.

This embodiment also provides a superconducting magnet system, which includes a superconducting magnet and the above-mentioned cooling system, and the superconducting magnet is the load 10 to be cooled. The superconducting magnet system provided in this embodiment, by adopting the above-mentioned cooling system, can reduce the pre-cooling time of the superconducting magnet to the preset working temperature, improve the operating efficiency of the superconducting magnet system, and shorten the recovery time when the superconducting magnet quenches. The time to the superconducting state improves the operation safety and reliability of the superconducting magnet system; at the same time, because the thermal switch 4 occupies a small space and can be arranged flexibly, the structure compactness of the superconducting magnet system can be effectively improved. It can be 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 supporting frame for installing the superconducting magnet coil. The superconducting magnet is fixed in the primary radiation shield 2 through the second support structure 8. The second support structure 8 may include a pull rod or a pull ring. The second support structure 8 is preferably made of a material with low thermal conductivity, high insulation and high strength. into, such as G10 fiberglass and so on. The support frame is a cylindrical structure, and the inner hole forms a room temperature hole 101 for placing samples. When the superconducting magnet is in operation, there is a uniform strong magnetic field in the hole 101 at room temperature.

In order to obtain high magnetic field strength, the superconducting magnet coil can be composed of multiple coils, and the coil materials can be conventional superconducting materials such as NbTi and Nb ₃ Sn or high-temperature superconducting materials such as magnesium diboride and yttrium barium copper oxide. The supporting frame can be made of 6063-T1 aluminum alloy and other materials.

The central axis of the room temperature hole 101 can be arranged vertically or horizontally, or along other directions, that is, the central axis of the room temperature hole 101 can be set according to the specific type and application scene of the superconducting magnet system.

In this embodiment, both the evaporation section of the thermal switch 4 and the heat conduction element 5 are connected to the supporting frame, so as to improve the connection convenience between the thermal switch 4 and the heat conduction element 5 and the superconducting magnet.

The superconducting magnet system also includes a diode assembly, which is used for quench protection of the superconducting magnet. The superconducting magnet system also includes a power supply assembly 6, which includes a superconducting excitation power supply 65 and wires connected between the superconducting excitation power supply 65 and the coil of the superconducting magnet. The superconducting excitation power supply 65 is located outside the vacuum enclosure 1 .

In order to better realize the connection between the superconducting magnet and the superconducting excitation power supply 65, the superconducting magnet system also includes an internal current wiring assembly 63 and an external current wiring assembly 64, and the internal current wiring assembly 63 is installed on the primary radiation shield 2 to connect the wires inside and outside the first-level radiation shield 2, and the external current wiring assembly 64 is installed on the vacuum cover 1 to connect the wires located on both sides of the vacuum cover 1. The internal current wiring assembly 63 is insulated from the primary radiation shield 2 , and the external current wiring assembly 64 is insulated from the vacuum cover 1 . For the specific structures of the internal current wiring assembly 63 and the external current wiring group 64, reference may be made to the prior art, which is not described and limited in the present invention.

Further, the power supply assembly 6 also includes a high temperature superconducting current lead 62 located inside the primary radiation shield 2, the high temperature superconducting current lead 62 is thermally connected and insulated with the secondary cold head 32 of the refrigerator 3, and the high temperature superconducting current lead A superconducting wire 61 is connected between 62 and the superconducting magnet, and a wire is connected between the high temperature superconducting current lead 62 and the internal current wiring assembly 63 .

The superconducting magnet system provided in this embodiment can be applied to information technology, biomedicine, environmental technology, military industry, industrial processing, marine, transportation, large scientific 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 maglev train, etc. , the present invention does not limit the specific type and application scenarios of the superconducting magnet system.

Embodiment two

This embodiment provides a cooling system and a superconducting magnet system, and the cooling system and the superconducting magnet system provided in this embodiment are further improvements based on the structure in Embodiment 1, and this embodiment is no longer the same as Embodiment 1 structure is described.

As shown in FIG. 3 , in this embodiment, the cooling system further includes a liquid filling system 20 for filling the first low temperature pulsating heat pipe 41 of the thermal switch 4 with a first working fluid. The liquid filling system 20 is mainly located outside the vacuum enclosure 1 .

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

The liquid filling system 20 also includes a first pressure sensor 207 , which is arranged on the filling pipe 209 and used for detecting the pressure fluctuation of the condensation section of the first low temperature pulsating heat pipe 41 . The buffer tank 201 is provided with a second pressure sensor 208 for detecting the pressure of the buffer tank 201 and calculating the filling rate.

The gas cylinder 202 stores a high-purity (purity: 99.999%) gaseous first working fluid, and the specific operation steps of the liquid filling process of the first low-temperature pulsating heat pipe 41 are as follows:

(1) Collect and record temperature and pressure data.

(2) Use the first high-purity working fluid and a group of molecular pump units 203 to purge and purify the pipelines in the first low-temperature pulsating heat pipe 41, the buffer tank 201 and the liquid filling system 20, so as to prevent residual gas in the pipelines. Air or other impurities affect the experiment.

The specific process is:

First, open the first shut-off valve 204 and the second shut-off valve 205, close the third shut-off valve 206, and use the molecular pump unit 203 to evacuate the first low-temperature pulsating heat pipe 41 and the liquid-filled system 20 to a high vacuum (vacuum value<1×10 ⁻³ Pa);

Then close the second shut-off valve 205, open the first shut-off valve 204 and the third shut-off valve 206, and fill the 99.999% high-purity first working fluid from the gas cylinder 202 into the first low-temperature pulsating heat pipe 41 and the buffer tank 201;

The same process is repeated more than 5 times to completely remove the impurity gas in the pulsating heat pipe and the liquid-filled system 20, and then evacuate to a high vacuum after completion.

(3) After the purification process is completed, open the third shut-off valve 206, close the first shut-off valve 204 and the second shut-off valve 205, open the gas storage bottle 202, fill the buffer tank 201 with high-purity first working fluid, then close the second shut-off valve A cut-off valve 204 to record the initial pressure P ₀ of the buffer tank 201 at this time.

(4) Open the first stop valve 204 , close the second stop valve 205 and the third stop valve 206 , and the high-purity first working fluid will enter the first low-temperature pulsating heat pipe 41 from the buffer tank 201 .

(5) Use another group of molecular pump units 203 to vacuumize the inside of the vacuum cover 1, and after the vacuum degree in the vacuum cover 1 is less than 1× ^10-3 Pa, start the refrigerator 3 to cool down the first low-temperature pulsating heat pipe 41 cool down.

(6) As the temperature of the condensing section of the first low-temperature pulsating heat pipe 41 decreases, the pressure also decreases. When it falls to the gas-liquid two-phase flow temperature zone of the first working medium, the liquid first working medium begins to be generated, and the pressure drops rapidly , the liquid first working medium moves from the condensation section to the evaporation section under the action of gravity, and accelerates the cooling of the evaporation section to the gas-liquid two-phase flow temperature zone. When the pressure of the buffer tank 201 drops to the pressure _P1 corresponding to the target filling rate, the first cut-off valve 204 is closed, and the first low-temperature pulsating heat pipe 41 is isolated from the filling system 20 . At this time, the first low-temperature pulsating heat pipe 41 is in an initial state in which gas plugs and liquid plugs are alternately distributed, and the liquid filling process ends.

The liquid filling rate is used to represent the mass of the liquid first working fluid filled in the first low-temperature pulsating heat pipe 41. In order to compare with the existing research data, when the first working fluid is nitrogen, the liquid filling rate is defined as 77.34K lower liquid The ratio of the nitrogen volume to the volume of the pulsating heat pipe.

When calculating the liquid filling rate, the first working fluid in the first low-temperature pulsating heat pipe 41 and the liquid filling system 20 is regarded as an ideal gas. According to the law of mass conservation and the ideal gas state equation, the mass _mt of the first working fluid can be calculated as follows: formula calculation:

Wherein: P ₀ and P ₁ are the initial pressure and the final pressure of the buffer tank 201 at the beginning and end of the filling process respectively, and the unit is Pa; V _FT and V _BT are the filling pipes (from the first stop valve 204 to the first low temperature part of the pulsating heat pipe 41) and the volume of the buffer tank 201, the unit is m ³ ; T _FT and T _BT are the average temperature of the liquid-filled pipeline and the buffer tank 201, respectively, and the unit is K; R _g is the gas of the first working medium constant; m _t is the mass of the working fluid charged into the pulsating heat pipe, in kg.

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

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

Among them, V _PHP and V _l are the volume of the first low-temperature pulsating heat pipe 41 and the volume of liquid nitrogen in the tube, respectively, in ^m3 ; ρ _v and ρ _l are the densities of saturated nitrogen and saturated liquid nitrogen at 77.34K, respectively, in units of It is kg/m ³ .

Therefore, the filling rate is:

The simultaneous equations 1 to 3 can determine the liquid filling rate of the first low-temperature pulsating heat pipe 41 according to the initial pressure and the final pressure of the buffer tank 201 . The calculation formula of the liquid filling rate takes into account the influence of the volume of the liquid filling pipe, and at the same time the volume of the remaining pipes of the liquid filling system 20 is considered as a part of the volume of the buffer tank 201 .

It should be noted that this filling method is also applicable to other cryogenic working fluids.

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

The function of the buffer tank 201 is not only to control the filling rate before the operation of the first low-temperature pulsating heat pipe 41, but also to automatically adjust the liquid filling rate and pressure when the first low-temperature pulsating heat pipe 41 is running, so as to prevent drying out. It is only necessary to open the first cut-off valve 204 and let the buffer tank 201 connect to the first low-temperature pulsating heat pipe 41 to operate.

Embodiment three

This embodiment provides a cooling system and a low-temperature superconducting magnetic system, and the cooling system provided by this embodiment is a further improvement on the cooling system in Embodiment 1. This embodiment no longer uses the same components as Embodiment 1 The content will be repeated.

As shown in FIGS. 4-6 , in this embodiment, the 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 a serpentine structure formed by capillary bending, which includes a plurality of parallel tube parts 411 arranged in parallel and at intervals in the first direction and a bend connected between two adjacent parallel tube parts 411 Section 412. The parallel pipe section 411 has a condensation section, an adiabatic section and an evaporation section connected in sequence.

The condensation plate 42 is provided with a plurality of first positioning grooves 421, and 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 set in one-to-one correspondence with the parallel pipe parts 411. The condensation section of the parallel pipe part 411 is located in the first positioning groove 421, the evaporation section of the parallel pipe part 411 is located in the second positioning groove 431, and both the first positioning groove 421 and the second positioning groove 431 are filled with solder to fix The first low-temperature pulsating heat pipe 41 and the corresponding condensing plate 42 and evaporating plate 43 reduce thermal resistance and ensure good thermal contact between the first low-temperature pulsating heat pipe 41 , the condensing plate 42 and the evaporating plate 43 . The bent portion 412 connected to the condensing section is located on a side of the condensing plate 42 away from the evaporating plate 43 , and the bent portion 412 connected to the evaporating section is located on a side of the evaporating plate 43 away from the condensing plate 42 .

The groove width of the first positioning groove 421 and the second positioning groove 431 is preferably larger than the outer diameter of the first low-temperature pulsating heat pipe 41, so as to ensure that the first low-temperature pulsating heat pipe 41 is accommodated in the first positioning groove 421 and the second positioning groove 431, And provide space for solder filling. Both the evaporating plate 43 and the condensing plate 42 are preferably made of pure copper, and the heat conduction efficiency is relatively high. The first low temperature pulsating heat pipe 41 is preferably made of stainless steel or pure copper.

The thermal switch 4 is preferably a multi-layer structure, that is, the parallel tube portion 411 extends along the second direction, and the thermal switch 4 preferably includes a multi-layer first low-temperature pulsating heat pipe 41 arranged side by side along the third direction, and the evaporating plate 43 and the condensing plate 42 are connected with each other. The first low-temperature pulsating heat pipes 41 are arranged in one-to-one correspondence, and the first direction, the second direction and the third direction are perpendicular to each other. The thermal switch 4 with the multi-layer first low-temperature pulsating heat pipe 41 can increase the thermal conductivity while saving the occupied space of the thermal switch 4 and improving the compactness of the thermal switch 4 .

In this embodiment, all the evaporating plates 43 are stacked and fastened in the third direction, and all the condensation plates 42 are stacked and fastened in the third direction.

A liquid injection channel is arranged in the liquid injection joint 44 , and the filling pipe of the liquid filling system communicates with the first low-temperature pulsating heat pipe 41 through the liquid injection channel. In this embodiment, all the first low-temperature pulsating heat pipes 41 are arranged in parallel, and joint pipes 413 are formed at both ends of each first low-temperature pulsating heat pipe 41, and the liquid injection channels are arranged in one-to-one correspondence with the first low-temperature pulsating heat pipes 41. The two joint pipe parts 413 of each first low-temperature pulsating heat pipe 41 are inserted into the liquid injection channel and are in sealing communication with the liquid injection channel. This arrangement can simplify the processing of the thermal switch 4 and improve the convenience of disassembling and assembling the thermal switch 4 .

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

Exemplarily, the first low temperature pulsating heat pipe 41 is provided with four layers, and each layer of the first low temperature pulsating heat pipe 41 has 12 parallel pipe parts 411 . In other embodiments, the number of layers of the first low-temperature pulsating heat pipe 41 and the number of parallel pipe portions 411 contained in the first low-temperature pulsating heat pipe 41 can be set according to requirements, such as three layers, five layers or more layers, each The layer includes 6 to 18 parallel pipe parts 411 .

Further, during the processing of the thermal switch 4, the evaporating plates 43 between two adjacent layers and the condensing plates 42 between the adjacent two layers are all welded with solder first, so that the gaps are filled with solder as much as possible; Lock all evaporating plates 43 and lock all condensing plates 42 .

In another embodiment, the thermal switch 4 may also include a plurality of first low-temperature pulsating heat pipes 41 arranged side by side in the first direction, and each first low-temperature pulsating heat pipe 41 is independently provided with a liquid injection joint 44 and a liquid filling system. , that is, each first low-temperature pulsating heat pipe 41 can be individually controlled to inject liquid. In yet another embodiment, the 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 first low-temperature pulsating heat pipe 41 are connected to a connecting pipe. , the connecting pipe communicates with the liquid filling system.

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

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

Embodiment four

As shown in Figure 7, this embodiment provides a cooling system and a superconducting magnet system. The cooling system and the superconducting magnet system provided in this embodiment are basically the same as those in Embodiment 3, only some settings are different, and this embodiment does not The same structure as that of the third embodiment will be described again.

In this embodiment, a plurality of evaporating plates 43 are divided into at least two groups that are separately arranged, and each group of evaporating plates 43 includes one evaporating plate 43 or at least two evaporating plates 43 that are stacked, and the adjacent two groups of evaporating plates 43 are on the second Set at intervals upwards on one side. Each group of evaporating plates 43 has a second connection surface in contact with the load to be cooled 10 .

By arranging at least two groups of evaporating plates 43, the contact position between the thermal switch 4 and the load to be cooled 10 can be increased, thereby improving the uniformity of cooling around the load to be cooled 10, and further improving the cooling efficiency.

Preferably, two groups of evaporating plates 43 are provided, and the two groups of evaporating plates 43 are respectively connected to both ends of the load to be cooled 10 , so as to effectively improve the cooling uniformity of the load to be cooled 10 while reducing the number of evaporating plates 43 .

Embodiment five

As shown in Figure 8, this embodiment provides a cooling system and a superconducting magnet system, and the basic structure of the cooling system provided by this embodiment is the same as that of Embodiment 1, only the arrangement of the heat conduction member 5 is different. The same structure as that of the first embodiment will not be described again.

In this embodiment, the heat conduction element 5 includes a second low-temperature pulsating heat pipe, the second low-temperature pulsating heat pipe is filled with a second working fluid, the critical temperature of the second working fluid is lower than the critical temperature of the first working fluid, and the secondary cold head The final refrigeration temperature of 32 is between the triple point temperature and the critical point temperature of the second working substance. When the secondary cold head 32 is at the final cooling temperature (ie, the target cooling temperature), the second working fluid in the second low-temperature pulsating heat pipe is in a two-phase flow state. The evaporating section of the second low-temperature pulsating heat pipe is thermally connected to the load to be cooled 10 , and the condensing section of the second low-temperature pulsating heat pipe is thermally connected to the secondary cold head 32 .

By making the heat conduction element 5 include a second low-temperature pulsating heat pipe, that is, using the second low-temperature pulsation heat pipe to transfer the cold energy of the secondary cold head 32 to the cooled load 10, the thermal conductivity of the heat conduction element 5 can be improved, and the heat conduction efficiency can be improved, thereby reducing The time required to cool the cooled load 10 to the preset operating temperature improves the efficiency of the cooling system; at the same time, due to the high thermal conductivity of the second low-temperature pulsating heat pipe, it can quickly realize the temperature drop of the cooled load 10 and reduce the cooled load 10 temperature rise probability, improve the operation safety and reliability of the cooling system; at the same time, the connection between the first low-temperature pulsating heat pipe 41 and the second low-temperature pulsating heat pipe and other structures is a flexible connection, flexible installation, not limited by direction and structure, both The weight is reduced, and the function of isolating the vibration of the refrigerator 3 can be achieved, which is especially suitable for applications of long-distance conduction superconducting magnets that are sensitive to vibration, such as nuclear magnetic resonance imaging.

The second working fluid filled in the second low temperature pulsating heat pipe is preferably helium, whose critical temperature is relatively low. However, it can be understood that the working fluid of the second low-temperature pulsating heat pipe can also be hydrogen, neon or the like. The working fluid of the first low temperature pulsating heat pipe 41 can be nitrogen, argon, krypton, oxygen, ammonia, methane, etc., the first working fluid in the first low temperature pulsating heat pipe 41 and the second working fluid in the second low temperature pulsating heat pipe can be according to The preset operating temperature required by the cooled load 10 is specifically selected.

The structure of the heat conduction member 5 can be set with reference to the structure of the thermal switch 4 in the first embodiment, the third embodiment or the fourth embodiment, and will not be repeated in this embodiment. Moreover, the structure of the thermal switch 4 in this embodiment can also adopt the structure of the thermal switch in Embodiment 3 and Embodiment 4, which will not be repeated here.

In this embodiment, the liquid filling system and liquid filling method corresponding to the second low-temperature pulsating heat pipe can refer to the settings in the second embodiment, and this embodiment will not repeat it this time.

In the superconducting magnet system provided in this embodiment, when the superconducting magnet is cooled to the liquid helium working temperature zone, the superconducting excitation power supply 65 starts to excite and generate a magnetic field, and the heat generated due to AC loss during excitation is generated by the second low-temperature pulsating heat pipe It is efficiently transmitted to the secondary cold head 32 of the refrigerator 3 to prevent the temperature of the superconducting magnet from exceeding the critical temperature and quenching. At the same time, due to the extremely high effective thermal conductivity of the second low-temperature pulsating heat pipe (the effective thermal conductivity is several orders of magnitude higher than that of copper), even if the superconducting magnet is quenched during excitation, the second low-temperature pulsating heat pipe can quickly transfer heat to the refrigerator 3 The secondary cold head 32 quickly recovers the temperature of the superconducting magnet to the working temperature range. In addition, the second low-temperature pulsating heat pipe has the advantage of a small temperature difference. Even if the heat transfer distance is very long, the temperature difference between the superconducting magnet and the secondary cold head 32 of the refrigerator 3 is still very small, so the refrigerator 3 can be kept away from the superconducting magnet. The magnetic conductor thus prevents the refrigerator 3 from being affected by the magnetic field during operation, thereby ensuring the refrigeration performance. In addition, the connections between the second low-temperature pulsating heat pipe and the first low-temperature pulsating heat pipe 41, the refrigerator 3 and the superconducting magnet are all flexible connections, which allow for flexible installation and are not limited by direction and structure. 3 The role of vibration, especially suitable for applications of long-distance conduction superconducting magnets that are sensitive to vibration, such as nuclear magnetic resonance imaging.

It should be pointed out that, on the outer side of the superconducting magnet, the outer side of the first-level radiation shield 2, the outer side of the first low-temperature pulsating heat pipe 41, the outer side of the second low-temperature pulsating heat pipe, the outer side of the first-level cold head 31 and/or the outer side of the second-level cold head 32 are wrapped with The heat insulation layer is preferably made of MLI material to improve the heat insulation effect and reduce radiation heat leakage. The thermal insulation layer preferably has at least 20 layers in order to increase the thermal insulation effect.

Embodiment six

This embodiment provides a cooling system and a superconducting magnet system. The cooling system of the superconducting magnetic system provided by this embodiment is a further improvement on the cooling system in any of the above-mentioned embodiments. This embodiment is no longer related to the above-mentioned The same structure as the embodiment will be described in detail.

In this embodiment, the secondary radiation protection screen 9 is suspended inside the primary radiation protection screen 2 , and the load to be cooled 10 is located inside the secondary radiation protection screen 9 . That is, by setting the secondary radiation protection screen 9 inside the primary radiation protection screen 2, the load to be cooled 10 is arranged in the secondary radiation protection screen 9, further reducing radiation heat leakage.

Preferably, in this embodiment, the primary cold head 31 is connected to the primary radiation shield 2 to absorb heat radiation from the environment to the primary radiation shield 2; the secondary cold head 32 is connected to the secondary radiation shield 9 , to absorb the heat radiation from the primary radiation shield 2 to the secondary radiation shield 9, and keep the secondary radiation shield 9 at a temperature close to that of the cooled load 10, which is beneficial to better maintain the work of the cooled load 10 ambient temperature.

In this embodiment, the secondary cold head 32 is connected to the secondary radiation shield 9 and the heat conduction element 5 respectively, so that the cooling energy of the secondary cold head 32 is directly transferred to the second low-temperature pulsating heat pipe. In other embodiments, the secondary cold head 32 can be connected with the secondary radiation shield 9, and the condensation section of the second low-temperature pulsating heat pipe is connected with the secondary radiation shield 9, so as to realize the connection between the condensation section and the secondary cold head 32. The thermal connection simplifies the connection structure between the secondary cold head 32 and the secondary radiation shield 9 and the second low-temperature pulsating heat pipe, reducing the difficulty of assembly.

Preferably, the exteriors of the primary radiation protection screen 2 and the secondary radiation protection screen 9 are covered with a thermal insulation layer, and the thermal insulation layer is preferably made of high-vacuum multilayer thermal insulation materials to further reduce heat radiation.

Furthermore, the exterior of the primary cold head 31, the secondary cold head 32, the first low-temperature pulsating heat pipe 4 and the second low-temperature pulsating heat pipe are all wrapped with a heat insulating layer, and the heat insulating layer is preferably made of a high-vacuum multi-layer heat insulating material.

Embodiment seven

As shown in Figure 10, this embodiment provides a cooling system and a superconducting magnet system, and the cooling system and the superconducting magnet system provided in this embodiment are further improved based on the superconducting magnet system provided in Embodiment 5. Example The same structure as that of the fifth embodiment will not be repeated.

In this embodiment, by using at least two refrigerators 3 , the running time of each redundant refrigerator 3 can be separated, and the duty cycle of the refrigerators 3 can be reduced, thereby prolonging the service life of the refrigerators 3 . Several refrigerators 3 can also run in parallel to improve the cooling efficiency of the cooled load 10 and ensure the operation safety and reliability of the cooled load.

In this embodiment, there are at least two refrigerators 3, and each refrigerator 3 has a primary cold head 31 and a secondary cold head 32, and each primary cold head 31 communicates with the load to be cooled through a thermal switch 4 10 connection, each secondary cold head 32 is connected to the load to be cooled 10 through the heat conduction member 5, the thermal switch 4 includes at least one first low-temperature pulsating heat pipe 41, the heat conduction member 5 includes at least one second low-temperature pulsating heat pipe, and the first The critical temperature of the first working fluid in the low temperature pulsating heat pipe 41 is higher than the critical temperature of the second working fluid in the second low temperature pulsating heat pipe.

In the cooling system provided in this embodiment, when one of the refrigerators fails or stops operating, the temperatures of the condensation sections of the first low-temperature pulsating heat pipe 41 and the second low-temperature pulsating heat pipe connected to the refrigerator 3 exceed the critical temperature, and the operation stops. , the first low-temperature pulsating heat pipe 41 and the second low-temperature pulsating heat pipe are all disconnected, preventing the heat load from being transferred to the cooled load 10 from the refrigerating machine 3 returning to normal temperature, and at the same time, the remaining refrigerating machines 3 are working normally, thus not affecting normal operation of the cooling system.

In this embodiment, preferably, each thermal switch 4 is correspondingly provided with a liquid filling system, so as to realize individual liquid filling control for the first low-temperature pulsating heat pipe 41 in each thermal switch 4 . In other embodiments, all the thermal switches 4 can share the same liquid filling system, that is, the same liquid filling system can fill the first low-temperature pulsating heat pipes 41 in all the thermal switches 4 synchronously.

Further, each heat conducting element 5 is correspondingly provided with a liquid filling system, so as to realize independent liquid filling control for the second low temperature pulsating heat pipe in each heat conducting element 5 . In other embodiments, all the heat conducting elements 5 may share the same liquid filling system, that is, the same liquid filling system performs liquid filling for the second low-temperature pulsating heat pipes in all the heat conducting elements 5 synchronously.

Embodiment eight

This embodiment provides a cooling method, which is applied to the cooling system and the superconducting magnet system provided in any one of Embodiments 1 to 7. In this embodiment, the structure of the cooling system and the superconducting magnet system will not be described in detail.

Specifically, the cooling method provided in this embodiment includes:

S1. Vacuumize the inside of the vacuum cover 1 until the vacuum value is less than the preset vacuum value;

Wherein, the vacuum degree corresponding to the preset vacuum value is less than 1×10 ⁻³ Pa.

S2, start the refrigerator 3;

S3. When the temperature of the primary cold head 31 reaches the gas-liquid two-phase flow temperature zone of the first low-temperature pulsating heat pipe 41, control the temperature of the primary cold head 31 to maintain the gas-liquid two-phase flow temperature zone, so that the thermal switch 4 in conduction state;

S4. When the temperature of the cooled load 10 is lower than the triple point temperature of the thermal switch 4, stop the temperature control of the primary cold head 31, so that the temperature of the primary cold head 31 drops below the temperature of the first low-temperature pulsating heat pipe The temperature of the triple point of the first working fluid causes the thermal switch 4 to be disconnected;

S5. When the temperature of the load to be cooled 10 drops to the preset working temperature along with the secondary cold head 32, the load to be cooled 10 starts to run.

The cooling method provided in this embodiment can improve the cooling efficiency of the load to be cooled 10 , thereby improving the working efficiency of the load to be cooled 10 , and improving the operation safety and reliability of the load to be cooled 10 .

Further, the cooling method further includes: during the operation of the cooled load, when the temperature of the cooled load rises to the gas-liquid two-phase flow temperature zone of the first low-temperature pulsating heat pipe 41, regulating the temperature of the primary cold head 31 To the gas-liquid two-phase flow temperature zone, so that the thermal switch 4 is turned from the off state to the on state.

The above setting can improve the efficiency of returning the cooled load 10 to the preset working temperature when the temperature rises during operation, and improve the operation safety and reliability of the cooled load 10 .

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, rearrangements and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the present invention The scope is determined by the scope of the appended claims.

Claims (12)

1. A cooling system for cooling a cooled load (10), characterized in that the cooling system comprises a vacuum cover (1), a refrigerator (3), a thermal switch (4) and a temperature control device, the The refrigerator (3) has a primary cold head (31) and a secondary cold head (32), and the cooled load (10), the primary cold head (31) and the secondary cold head (32) are located in the vacuum cover (1), the thermal switch (4) includes a first low-temperature pulsating heat pipe (41), and the condensation section of the first low-temperature pulsating heat pipe (41) is connected to the primary cold head (31 ) thermal connection, the evaporation section of the first low temperature pulsating heat pipe (41) is connected to the cooled load (10), and the secondary cold head (32) is connected to the cooled load (10). The heat conduction element (5), the final cooling temperature of the primary cold head (31) is lower than the triple point temperature of the working medium in the first low-temperature pulsating heat pipe (41), and the temperature control device is used to control the The refrigeration temperature of the primary cold head (31) and the secondary cold head (32). 2. The cooling system according to claim 1, characterized in that, the thermal switch (4) also includes an evaporation plate (43) and a condensation plate (42), and the evaporation plate (43) and the condensation plate ( 42) are made of heat-conducting metal, the condensation section of the first pulsating heat pipe (41) is fixed on the condensation plate (42), and the evaporation section of the first pulsating heat pipe (41) is fixed on the evaporation plate ( 43), the condensation plate (42) is connected to the primary cold head (31), and the evaporation plate (43) is connected to the cooled load (10). 3. The cooling system according to claim 2, characterized in that the thermal switch (4) comprises at least two of the first low-temperature pulsating heat pipes (41), the evaporation plate (43) and the condensation plate (42) are set in one-to-one correspondence with the first low-temperature pulsating heat pipe (41); All the condensation plates (42) are stacked and fixedly connected, and one of the condensation plates (42) located on the outside is connected to the primary cold head (31); All the evaporating plates (43) are divided into at least two groups that are separately arranged, and each group of evaporating plates (43) includes at least one evaporating plate (43) or a plurality of evaporating plates (43) stacked and fixedly arranged. ), in each group of evaporator plates (43), one of the evaporator plates (43) located on the outside is connected to the load to be cooled (10). 4. The cooling system according to claim 1, characterized in that, the cooling system also includes a primary radiation protection screen (2), and the primary radiation protection screen (2) is suspended from the vacuum cover (1 ), the load to be cooled (10) is suspended inside the primary radiation shield (2), and the primary cold head (31) is thermally connected to the primary radiation shield (2). 5. The cooling system according to claim 4, characterized in that, the cooling system also includes a secondary radiation protection screen (9), and the secondary radiation protection screen (9) is suspended from the primary radiation protection Inside the screen (2), the cooled load (10) is suspended inside the secondary radiation protection screen (9), and the secondary cold head (32) is thermally connected to the secondary radiation protection screen (9). connect. 6. The cooling system according to any one of claims 1-5, characterized in that, the heat conducting member (5) comprises a second low-temperature pulsating heat pipe, and the evaporation section of the second low-temperature pulsating heat pipe is connected to the cooled The load (10) is connected, the condensation section of the second low-temperature pulsating heat pipe is thermally connected to the secondary cold head (32), and the final cooling temperature of the secondary cold head is at the working fluid in the second low-temperature pulsating heat pipe between the triple point temperature and the critical point temperature. 7. The cooling system according to claim 6, characterized in that, the working medium in the first low-temperature pulsating heat pipe (41) is argon, nitrogen, oxygen or methane; The working fluid in the second low temperature pulsating heat pipe is helium, hydrogen or neon. 8. The cooling system according to claim 6, characterized in that at least two refrigerators (3) are provided, and the thermal switch (4) and the heat conduction member (5) are connected with the refrigerator (3) One-to-one correspondence setting. 9. The cooling system according to any one of claims 1-5, characterized in that, the primary cold head (31), the secondary cold head (32), the thermal switch (4), the The outer surface of the load to be cooled (10) and/or the heat conduction member (5) is covered with multiple layers of heat insulating material; And/or, the thermal switch (4) has a first connecting surface and a second connecting surface, the first connecting surface is thermally connected to the primary cold head (31), and the second connecting surface is connected to the Thermally connected to the cooling load (10), the first connection surface and/or the second connection surface are provided with a heat-conducting coating and/or a heat-conducting sheet. 10. A superconducting magnet system, comprising a superconducting magnet, characterized in that it further comprises the cooling system according to any one of claims 1-9, the superconducting magnet being the cooled load (10). 11. A cooling method, characterized in that it is applied to the cooling system according to any one of claims 1-9, the cooling method comprising: Vacuumize the inside of the vacuum cover (1) until the vacuum value is less than the preset vacuum value; Start the refrigerator (3); When the temperature of the primary cold head (31) reaches the gas-liquid two-phase flow temperature zone of the first low-temperature pulsating heat pipe (41), control the temperature of the primary cold head (31) to maintain the temperature of the gas-liquid two-phase flow. Liquid two-phase flow temperature zone, so that the thermal switch (4) is in a conducting state; When the temperature of the cooled load (10) is lower than the triple point temperature of the thermal switch (4), stop the temperature control of the primary cold head (31), so that the primary cold head (31) The temperature drops below the triple point temperature of the working medium in the first low-temperature pulsating heat pipe (31), so that the thermal switch (4) is turned off; When the cooled load (10) drops to a preset working temperature along with the secondary cold head (32), the cooled load (10) starts to run. 12. cooling method according to claim 11, is characterized in that, described cooling method also comprises: During the operation of the load to be cooled (10), when the temperature of the load to be cooled (10) rises to the gas-liquid two-phase flow temperature zone of the first low-temperature pulsating heat pipe (41), adjust the The temperature of the first-stage cold head (31) reaches the temperature range of the gas-liquid two-phase flow, so that the thermal switch (4) changes from an off state to an on state.

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