JP4236404B2 - Superconducting coil cooling system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cooling device for a superconducting coil mounted on a magnetically levitated railway that can be uniformly cooled and can be downsized.
[0002]
[Prior art]
In recent years, attempts have been made to use superconducting magnets using superconducting coils in magnetic levitation railways, medical equipment (medical MRI, etc.), energy storage devices, generators, etc. An “apparatus for cooling the superconducting coil to a cryogenic temperature lower than the critical temperature” for putting the superconducting coil into a superconducting state is indispensable.
[0003]
For example, FIG. 2 is an explanatory diagram of a “superconducting coil cooling device” used in a superconducting magnet for a floating railway using a superconducting coil made of an Nb—Ti superconducting material.
In this superconducting coil cooling device, helium gas compressed by the helium compressor 11 is introduced into the GM cycle refrigerator 12 through a high-pressure helium pipe, and the displacer of the refrigerator is reciprocated to cool the helium gas. Then, liquid helium having a boiling point of 4.2K is generated from the cooled helium gas by a Linde cycle using a heat exchanger and a throttle valve, and is stored in the liquid helium reservoir 13, which is stored in an inner tank 15 containing a plurality of superconducting coils 14. A configuration is adopted in which the superconducting coil is cooled by being immersed in liquid helium.
In the apparatus, a radiant heat shield plate 16 cooled with liquid nitrogen is installed so as to cover the inner tank 15, and these are accommodated in an aluminum container called an outer tank 17. It has become. The outer tub 17 also plays a role of shielding the fluctuating magnetic field from the ground coil, and the space portion including the radiant heat shield plate 16 inside the outer tub 17 and outside the inner tub 15 is used to block heat conduction. Is held in a vacuum.
[0004]
FIG. 3 is an explanatory view showing more specifically the internal structure of the superconducting coil housing portion in the above-mentioned apparatus. The superconducting coil 14 is housed in a coil holding container 3 made of high-rigidity stainless steel and is electromagnetically deformed. The mounting bracket 18 is firmly fastened between the two so as not to cause a relative shift due to vibration during running or the like.
By the way, the superconducting coil 14 and the coil holding container 3 kept at a very low temperature are subjected to strong magnetic forces such as propulsion, levitation, and guidance due to the interaction with the ground coil. The coil holding container 3 is firmly fixed to the carriage portion by the load support material 4 in order to transmit to the carriage. The load support material 4 is preferably a cylindrical material made of alumina fiber reinforced plastics that is lightweight, has high strength, and has low thermal conductivity.
[0005]
However, since the cooling device of such a conventional type is a system in which the superconducting coil is cooled by sending a cryogenic cooling medium (liquid helium) into the coil holding container, there are various types for handling the cryogenic cooling medium. Equipment and caution are required, which is not only disadvantageous in terms of equipment space, equipment cost, handling, etc., but also difficult to adjust the cooling temperature range.
In the above cooling device, the GM cycle refrigerator used is composed of a displacer driven by a motor or a magnetic regenerator, so that it is disposed near a magnet (superconducting coil). Although it is not preferable, there is a problem that a GM cycle refrigerator that generates and supplies a cryogenic cooling medium (liquid helium) must be placed close to the superconducting coil to prevent heat input to the cooling medium as much as possible. Furthermore, since a GM cycle refrigerator having a displacer and a displacer drive motor must be disposed close to the superconducting coil, further miniaturization of the vicinity of the superconducting coil cannot be realized. There was also a problem.
[0006]
[Problems to be solved by the invention]
For this reason, the object of the present invention is that it is possible to accurately cool the superconducting coil without adversely affecting magnetic properties, and it is also possible to adjust the cooling temperature in a wide range, and It is an object of the present invention to provide an easy-to-handle superconducting coil cooling device that can achieve further miniaturization in the vicinity of the superconducting coil.
[0007]
[Means for Solving the Problems]
The present inventor conducted intensive research from the above viewpoint, and found that a “Stirling cycle refrigerator having a piston” and a “disperser” that have been used as refrigerators for superconducting coil cooling devices have been used. A bubble motor and a plurality of “pulse tube refrigerators” are applied in place of the “GM cycle refrigerator”, and the low temperature ends (cold heads) of the plurality of pulse tube refrigerators are used as components of the coil holding container. It has been found that the object can be achieved by disposing in a plurality of places.
[0008]
The present invention has been made based on the above knowledge and the like, and provides a cooling device for a superconducting coil described below.
The high temperature ends of a plurality of pulse tube refrigerators are connected to the refrigerant gas compressor via a gas distribution valve motor, and the low temperature ends of the pulse tube refrigerators serve as a heat intrusion source to the low temperature system. composed by to perform contact conduction cooling of the superconducting coil by interpolating a plurality of cylindrical load supporting member "for supporting the coil holding container containing a superconducting coil, the superconducting coil to be mounted on the maglev cooling device .
[0009]
Hereinafter, the present invention will be specifically described based on examples.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an example of a superconducting coil cooling device according to the present invention, and is an explanatory view of a main part of an example of a superconducting coil cooling device mounted on a magnetically levitated railway.
In this cooling device, a high temperature end of a plurality of pulse tube refrigerators 2 is connected to a helium compressor (COMP) for compressing helium as a cooling medium via a valve motor 1 for gas distribution. Yes. The helium compressor and the valve motor 1 are connected by a normal temperature helium pipe as in the case of connecting a GM cycle refrigerator to a conventional helium compressor.
[0010]
The low-temperature ends (cold heads) of the plurality of pulse tube refrigerators 2 connected to the gas distribution valve motor 1 at the high-temperature ends are located at a plurality of locations in the coil holding container 3 in which the superconducting coils are housed and fixed. In this example, the load supporting member 4 that supports the coil holding container at four locations is arranged and fixed.
[0011]
The pulse tube refrigerator is a system in which the cooling medium is stopped in the tube and the low temperature end is in contact with the object to be cooled to conduct conduction cooling. Therefore, it is difficult to uniformly cool the object to be cooled. It is.
However, by interposing a valve motor as described above, a plurality of pulse tube refrigerators can be attached to one cooling medium compressor, and the low temperature ends of the plurality of pulse tube refrigerators can be coiled. By disposing the holding container at a plurality of locations, it is possible to prevent “nonuniform temperature distribution of the object to be cooled (superconducting coil)”, which is a drawback of the conduction cooling method.
[0012]
Of course, the low-temperature end of the pulse tube refrigerator 2 may be fixed at a place other than the load support material 4 that supports the coil holding container 3, but a coil holding container in which an alumina fiber reinforced plastic cylinder is usually used. It is preferable to insert it into the load support material 4 that supports the internal structure. This is because the load supporting material 4 that supports the coil holding container is a part that becomes a heat intrusion source to the low temperature system (near the superconducting coil), and it is possible to effectively prevent heat from entering by directly cooling this part. Can do. Furthermore, by embedding the low temperature end of the pulse tube refrigerator 2 in the coil holding container structure as described above, space saving (miniaturization) of the apparatus can also be achieved.
[0013]
In this case, a plurality of valve motors are required. However, compared with the case where a conventional GM cycle refrigerator or the like is added, the apparatus can be reduced in size, and the superconducting coil portion should be arranged as close as possible. Unlike the GM cycle refrigerator, etc., which required a high temperature end of a pulse tube refrigerator, the high temperature end of the pulse tube refrigerator does not need to be placed very close to the superconducting coil portion. -The selection range of the installation location is expanded. Therefore, this point is also an advantageous condition for space-saving design of the apparatus.
[0014]
In addition, since the valve motor is also affected by the magnetic field, it must be installed in a location where the magnetic field is as low as possible. However, as described above, the installation location of the valve motor is small because the selectable range is large. Can also be selected.
[0015]
Above all, since the superconducting coil cooling device according to the present invention enables the application of a pulse tube refrigerator, it does not require a facility for supplying or managing a cryogenic cooling medium, and the cryogenic cooling medium. It has the great advantage that it does not require various considerations associated with the handling.
[0016]
By the way, since the pulse tube refrigerator is cooled with a temperature gradient from the high temperature end to the low temperature end, the superconducting coil cooling device according to the present invention to which the pulse tube refrigerator is applied has a very low temperature. The cooling ability can be exhibited in a wide temperature range up to a relatively high temperature.
Therefore, the superconducting coil cooling device according to the present invention is not only used for cooling to the liquid helium (boiling point: 4.2 K) temperature necessary for cooling the metal superconducting coil, but rather has recently attracted attention as an oxide-based high temperature superconductor. It can be said that this is more suitable for cooling the superconducting coil constituted by (cooling to about 20K or about 100K).
[0017]
As described above, in the superconducting coil cooling device according to the present invention, the configuration in which the helium compressor and the refrigerator are connected by a normal temperature helium pipe is the same as that of the conventional cooling device using the GM cycle refrigerator. Since the portion is divided into a plurality of parts and their low-temperature ends are arranged in a plurality of parts of the member constituting the coil holding container of the superconducting magnet (preferably embedded in the structural material of the coil holding container), The following benefits can be enjoyed.
(a) No equipment for supplying or managing the cryogenic cooling medium is required, and various considerations associated with the handling of the cryogenic cooling medium are not required.
(b) Even if a pulse tube refrigerator is used, the problem of “non-uniform temperature distribution of the object to be cooled”, which is a drawback of conduction cooling type refrigeration, can be suppressed.
(c) The superconducting magnet device can be miniaturized by saving space.
(d) Since the cooling ability can be exhibited in a wide temperature range from a relatively high temperature to a very low temperature, it can be applied to the cooling of superconducting coils of various materials, and an improvement in the efficiency of the cooling device can be expected.
[0018]
In this embodiment, helium (He) is used as the refrigerant gas, but it goes without saying that other gases such as nitrogen may be used as the refrigerant gas .
[0019]
【The invention's effect】
As described above, according to the present invention, the superconducting coil can be uniformly cooled and can be widely used from a high temperature (for example, a critical temperature of a high-temperature superconductor) to a low temperature (for example, a critical temperature of an Nb-Ti superconductor). It is possible to provide an easy-to-handle superconducting coil cooling device that can exhibit cooling capacity in the temperature range and can reduce the size of the superconducting magnet, greatly improving the performance of magnetically levitated railways using superconducting magnets. Industrially useful effects such as being able to contribute are brought about.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of an example of a cooling device for a superconducting coil according to the present invention.
FIG. 2 is an explanatory diagram of a “superconducting coil cooling device” used in a superconducting magnet for a floating railway using a superconducting coil made of Nb—Ti superconducting material.
FIG. 3 is an explanatory view showing more specifically the internal structure of the superconducting coil storage portion of the apparatus according to FIG. 2;
[Explanation of symbols]
1 Valve Motor 2 Pulse Tube Refrigerator 3 Coil Holding Container 4 Load Support Material
11 Helium compressor
12 GM cycle refrigerator
13 Liquid helium reservoir
14 Superconducting coil
15 Inner tank
16 Radiant heat shield plate
17 Outer tank
18 Mounting bracket

Claims (1)

The high temperature ends of a plurality of pulse tube refrigerators are connected to the refrigerant gas compressor via a gas distribution valve motor, and the low temperature ends of the pulse tube refrigerators serve as a heat intrusion source to the low temperature system. composed by to perform contact conduction cooling of the superconducting coil by interpolating a plurality of cylindrical load supporting member "for supporting the coil holding container containing a superconducting coil, the superconducting coil to be mounted on the maglev cooling device .

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