JPH0584651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cryogenic device such as a superconducting magnet, and particularly to a cryogenic device using a natural circulation cooling method. [Technical background of the invention and its problems] In a superconducting magnet device, a superconducting coil is
It is necessary to cool it to an extremely low temperature of about 4K.
Conventionally, superconducting coils have been cooled by immersing them in a liquid helium reservoir. However, this method has drawbacks such as the helium reservoir requiring a large space, the need to store a large amount of helium, and the helium reservoir manufacturing process being complicated. In contrast, a method has been proposed in which a refrigerant such as liquid helium is forced to circulate in a refrigerant circulation path that is thermally connected to the superconducting coil to cool the superconducting coil. However, since this method requires equipment for forced circulation of the refrigerant, it has been difficult to apply it to small superconducting coils. In addition, it is necessary to constantly force the refrigerant to circulate not only during pre-cooling but also after the superconducting coil has been cooled to an extremely low temperature, which places a heavy burden on the refrigerant circulation power source such as a compressor. [Object of the Invention] The present invention was made in view of the above circumstances, and its purpose is to reduce the space and helium storage amount necessary for cooling objects to be cooled such as superconducting coils. The object of the present invention is to provide a cryogenic device that can be easily manufactured and can be applied to small superconducting coils. [Summary of the Invention] The gist of the present invention is to use a so-called natural fall circulation type cooling device as a cooling device for cooling objects to be cooled such as superconducting coils, and to forcibly flow a refrigerant through a pipe dedicated to precooling during precooling. There is a particular thing. That is, the present invention provides a cryogenic apparatus that includes an object to be cooled and a cooling device that cools the object to an extremely low temperature. It consists of a liquid reservoir and a vaporizer that constitutes a cooling cycle, and the piping is installed in a closed loop via the liquid reservoir, and at least the refrigerant from the vaporizer to the liquid reservoir is directed upward in the direction of gravity. a refrigerant circulation path configured to proceed to the object to be cooled; a means for thermally connecting the vaporizing section to the object to be cooled; and a refrigerant circulation path in which the object to be cooled is cooled by forcing the refrigerant to flow during precooling. A pre-cooling pipe is provided which is independent of the pipe. [Effects of the Invention] According to the present invention, since a natural fall circulation method is adopted that uses the density difference between liquefied refrigerant and vaporized refrigerant to obtain refrigerant circulation power, it is not necessary to use a compressor like a compressor except during pre-cooling. No means for obtaining refrigerant circulation power is required. In other words, once the object to be cooled, such as the superconducting coil, has been cooled to a low temperature (or an intermediate temperature), the circulating power of the refrigerant is no longer necessary, and energy savings can be achieved. Further, during precooling, it is sufficient to simply attach a power source such as a compressor for flowing refrigerant to the precooling gas pipe, and it is also possible to configure this power source to be externally attached. Therefore, the overall configuration can be simplified, and application to small superconducting coils is also possible. Furthermore, since the present invention employs a method of cooling the object to be cooled by thermally connecting the refrigerant circulation path and the object to be cooled, a liquefied helium reservoir for immersing the object to be cooled is not required. I don't. Therefore,
The space required for cooling the object to be cooled and the amount of helium stored can be reduced. [Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The figure is a partially cutaway perspective view of a superconducting magnet device according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a superconducting coil (an object to be cooled) formed in an annular shape, and the coil 1 is cooled to an extremely low temperature by a cooling device 2 that covers its entire outer peripheral surface. The cooling device 2 is specifically configured as follows. That is, the outer circumferential surface of the superconducting coil 1 is entirely covered by the heat equalizing plate 11. Soaking plate 1
1 is constructed by fixing each circumferential end of two semicircular divided bodies 11a and 11b made of a good thermal conductor such as copper with insulating bolts 13 through an electrically insulating plate 12. ing. With this configuration, induction heating of the heat equalizing plate 11 due to excitation of the superconducting coil 1 is suppressed. The heat soaking plate 11 and the superconducting coil 1 are integrated using an epoxy resin 14 having a coefficient of thermal expansion similar to that of copper and having excellent thermal conductivity for the purpose of improving thermal adhesion. Note that a plurality of holes 15 are bored in the heat equalizing plate 11, and the epoxy resin 14 on both sides of the heat equalizing plate 11 is integrated through these holes 15. Therefore, the heat soaking plate 11 and the epoxy resin 14 are designed to thermally shrink together. Therefore, the superconducting coil 1 has the above-mentioned heat soaking plate 11
It is cooled by the cooling device main body 16 of a natural fall circulation type. The cooling device main body 16 includes a liquid helium tank (liquid reservoir) 17 installed above the superconducting coil 1, and a refrigerant flow pipe 18 that allows a refrigerant to flow from the bottom of the liquid helium tank 17 to the same side.
It is made up of. The liquid helium tank 17 stores liquid helium P. The refrigerant flow pipe 18 includes two divided bodies 11a and 11 of the heat equalizing plate 11.
Two systems are installed so as to crawl on the outside surface of b,
Each system includes a refrigerant pumping section 21 that advances downward in the direction of gravity from the bottom of the liquid helium tank 17 on the outer circumferential surface of the heat equalizing plate 11, and a refrigerant pumping section 21.
The vaporizer 22 is guided upward in the direction of gravity from the lowest end of the liquid helium tank 17 onto the free liquid surface of the liquid helium tank 17. The refrigerant pumping part 21 is fixed to the heat equalizing plate 11 via a heat insulating spacer 23 having poor thermal conductivity, and is thermally insulated from the heat equalizing plate 11. In addition, the vaporization section 22
is embedded in the epoxy resin 14 so as to be in direct contact with the heat equalizing plate 11, and is fixed to the heat equalizing plate 11 at a predetermined portion or over the entire length by a method such as soldering. Furthermore, the vaporization section 22
It is composed of a plurality of branch pipes 31 that are provided in close contact with the circumferential surface of the heat equalizing plate 11 and extend in the circumferential direction, and headers 32 and 33 that commonly connect both ends of these branch pipes 31. Therefore, the liquid helium P pumped out from the liquid helium tank 17 passes through the refrigerant pumping part 21 and reaches the header 33 at the lower end.
In the process of ascending from 3 to each branch pipe 31, heat is exchanged with the superconducting coil 1 and vaporized. The vaporized refrigerant is
It is collected in the header section 32 at the upper end and returned to the liquid helium tank 17 via the return pipe 34. On the other hand, a pre-cooling pipe 51 that is independent of the refrigerant circulation path 18 is provided on the outer peripheral surface (of the epoxy resin 14) of the heat equalizing plate 11. This pre-cooling pipe 51
A cold gas or liquid is sent from the supply port 52, and the flow of this gas or liquid causes the coil 1 to
is cooled to an intermediate temperature. The gas or steam heated by the coil 1 is then discharged from the exhaust port 53. The above-mentioned superconducting coil 1 and cooling device 2 are surrounded by a radiation shield 24 of about 50 to 80K, for example, and the whole is housed inside a vacuum container 25 to block heat from entering from the outside. . In the superconducting magnet device according to this embodiment configured as described above, the superconducting coil 1, which is the object to be cooled, is cooled in the following manner. That is, the liquid helium P contained in the liquid helium tank 17 is pumped out from the bottom of the liquid helium tank 17 to the refrigerant pumping part 21 by gravity. Since the refrigerant pumping part 21 is thermally insulated from the heat equalizing plate 11, the liquid helium P reaches the lowest end in the gravity direction at the same temperature. Furthermore, the vaporization section 2
The liquid helium P that has reached 2 is heat exchanged with the superconducting coil 1 via the heat equalizing plate 11 and vaporized. The vaporized refrigerant rises in a meandering manner through the vaporization section 22 and returns to the free liquid surface of the liquid helium tank 17 . The refrigerant gas on the free liquid surface is liquefied by a liquefaction device (not shown) and pumped out from the refrigerant pumping section 21 again. Note that this liquefaction device may not be necessary.
In this case, liquid helium must be refilled.
In this refrigeration cycle, a difference in the density of the refrigerant occurs between the inside of the refrigerant pumping section 21 and the inside of the vaporization section 22, so that the circulating power of the refrigerant can be obtained from this density difference. Therefore, this cooling device 2 does not require any special means for circulating the refrigerant. On the other hand, when cooling (precooling) the superconducting coil 1 from room temperature to an intermediate temperature, a compressor or the like is attached to the supply port 52 of the precooling piping 51, and liquid nitrogen or the like is fed from the supply port 52. Thereby, liquid nitrogen or nitrogen gas is forced to flow into the precooling gas pipe 51, and the superconducting coil 1 can be rapidly cooled by heat exchange via the heat equalizing plate 11. The vaporized nitrogen vapor heated by the coil 1 is discharged from the exhaust port 53. When the precooling of the coil 1 is completed, a blind stopper is placed on the discharge port 53, and the supply port 52 is evacuated and then sealed. Once the superconducting coil 1 has been cooled to an intermediate temperature, even if the flow of the refrigerant in the pre-cooling pipe 51 is stopped, the superconducting coil 1 will be cooled to an extremely low temperature by the refrigerant circulating in the refrigerant passage 18. Ru. In other words,
After cooling to an intermediate temperature, a circulating power source such as a compressor is not required. As described above, according to this embodiment, the refrigerant flow pipe 1 is operated without using a device for forcedly circulating the refrigerant except during precooling.
Since the refrigerant can be naturally circulated inside the device 8, the entire device can be downsized and the configuration can be simplified, and furthermore, energy savings can be achieved. Also,
Since the pre-cooling pipe 51 is provided independently of the refrigerant passage 18, residual nitrogen during pre-cooling does not enter the liquid helium tank 17, and troubles with the refrigerator can be prevented. can. Further, since a liquid helium reservoir in which the superconducting coil 1 is immersed is not required, there are advantages such as the space required for cooling the superconducting coil 1 and the amount of liquid helium stored can be reduced. Note that the present invention is not limited to each of the embodiments described above. For example, the refrigerant flowing through the pre-cooling pipe is not limited to liquid nitrogen, but may be gas as long as it can cool the object to be cooled to a predetermined intermediate temperature. Further, the refrigerant to be circulated in the refrigerant circulation path is not limited to liquid helium, and can be changed as appropriate depending on the temperature at which the object to be cooled is cooled. Furthermore, the object to be cooled is not limited to superconducting coils, but can be applied to any object that needs to be cooled to an extremely low temperature. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

The figure is a partially cutaway perspective view of a superconducting magnet device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Superconducting coil (cooled object), 2 ... Cooling device, 11... Soaking plate, 12... Insulating plate, 14...
...Epoxy resin, 16 ...Cooling device main body, 17...
...liquid helium tank (liquid reservoir), 18...refrigerant flow pipe, 21...refrigerant pumping section, 22...vaporization section,
24... Radiation shield, 25... Vacuum container, 31
... Branch piping, 32, 33 ... Header, 51 ... Precooling pipe, 52 ... Supply port, 53 ... Discharge port, P ... Liquid helium.

Claims (1)

[Scope of Claims] 1. In a cryogenic apparatus comprising an object to be cooled and a cooling device that cools the object to an extremely low temperature, the cooling device includes a cooling device installed above the object to be cooled. It consists of a liquid reservoir for low-temperature liquid and a vaporizer that constitutes a cooling cycle, and the piping is installed in a closed loop through the liquid reservoir, and at least the refrigerant from the vaporizer to the liquid reservoir flows in the direction of gravity. a refrigerant circulation path configured to advance upward to a refrigerant circuit, and means for thermally connecting the vaporization section to the object to be cooled;
A cryogenic device characterized by comprising a pre-cooling pipe provided independently of the refrigerant circulation path and for cooling the object to be cooled by forcibly flowing a refrigerant during pre-cooling. 2. The cryogenic device according to claim 1, wherein the object to be cooled is a superconducting coil. 3. Claim 1, characterized in that, as a means for thermally connecting the vaporizing section to the object to be cooled, a heat equalizing plate is used which contacts the vaporizing section and covers the object to be cooled. cryogenic equipment. 4. The cryogenic apparatus according to claim 3, wherein the heat soaking plate is divided into a plurality of parts in the circumferential direction of the object to be cooled, and each part is electrically insulated.