JPH10325661A - Superconductive member cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit continuous operation for a long period of time by a method wherein liquid nitrogen is cooled by a refrigerating machine to a temperature, whereat the nitrogen is supercooled under an atmospheric pressure, and obtained liquid nitrogen of supercooled condition is employed to cool a superconductive member directly as it is. SOLUTION: In a cooling vessel 3, a superconductive member 1 is cooled and retained at about 67 K by the liquid nitrogen 11 of an atmospheric pressure under the supercooled condition of about 65 K. On the other hand, the liquid nitrogen, whose temperature is raised to about 70 K due to heat from the superconductive member 1 in the cooling vessel 3, is returned into a supplying side vessel 21 through a circulating tube 17. Then, the circulated liquid nitrogen is cooled by the cooling head 41A of a refrigerating machine 41 and is sent again into the cooling vessel 3 by a liquid feed pump 43. In this case, convection mixing is precluded between the vicinity of a liquid level 11A and liquid bottom part side by a heat insulating member 11. As a result, the liquid nitrogen 11 for cooling, which is in a bottom part whereat the superconductive member 1 is positioned, can be maintained surely under the supercooled condition of about 65 K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting member for cooling and holding a superconducting member such as a superconducting transformer, a superconducting magnet, various superconducting coils or a superconducting cable, particularly a high-temperature superconducting member, with liquid nitrogen at a low temperature. The present invention relates to a cooling device.

[0002]

2. Description of the Related Art In cooling a superconducting member such as a superconducting coil, particularly a superconducting member utilizing high-temperature superconductivity, relatively inexpensive liquid nitrogen (LN ₂ ) is often used as a cooling medium. In this case, saturated liquid nitrogen at atmospheric pressure, that is, liquid nitrogen of about 77K is generally used. That is, the superconducting member is housed in a cooling vessel substantially open to the atmosphere called a cryostat insulated by vacuum, and about 77 K of atmospheric pressure saturated liquid nitrogen is injected into the cooling vessel to form the liquid nitrogen. Normally, the superconducting member is immersed therein, and cooled and held.

[0003]

It is known that in a high-temperature superconducting member, the superconducting characteristics are significantly improved if the temperature is lowered even a little. For example, it is known that the critical current increases several times even if it is reduced from 77K to 70K.

[0004] Therefore, it is conceivable that the superconducting member is immersed in liquid nitrogen whose temperature has been reduced to, for example, about 65K by reducing the pressure of liquid nitrogen at atmospheric pressure to cool the superconducting member to a temperature lower than 77K. In that case, in a container for immersing the superconducting member in liquid nitrogen, it is necessary to maintain the decompressed state of liquid nitrogen. By the way, since a generally used cryostat is assumed to be used in a state of being substantially opened to the atmosphere, if this kind of general-purpose cryostat is applied to decompressed liquid nitrogen, a lid or a current introduction terminal is required. Insufficient sealing at such places as above, atmospheric pressure air containing moisture is sucked in from the outside, clogging due to moisture freezing in the gas vent hole of the current introduction terminal and ice on the superconducting member surface Sticking,
Practical operation may not be possible. Therefore, for the above-mentioned purpose, it is necessary to design and manufacture a new special container, and in that case, there is a problem that causes a significant rise in cost, and for that reason, practical use has been hesitated. .

On the other hand, when the superconducting member is operated by immersing the superconducting member in saturated liquid nitrogen at atmospheric pressure, the saturated liquid nitrogen is immediately vaporized by the heat generated by the superconducting member and gas bubbles are generated. There is a problem that the electrical insulation is reduced by the bubbles or the cooling efficiency is reduced. However, as described above, even when the superconducting member is immersed in liquid nitrogen whose temperature is reduced to about 65 K by decompression, for example. However, under reduced pressure, the heat generated by the superconducting member immediately vaporizes the liquid nitrogen to generate air bubbles, which is not a fundamental solution to the generation of air bubbles. Therefore, this is also one of the reasons that the use of decompressed liquid nitrogen has been hesitated.

Accordingly, the present inventors have already filed Japanese Patent Application No. Hei 8-23.
In No. 2566, when cooling a high-temperature superconducting member with liquid nitrogen, a special general-purpose cryostat that is open to the atmosphere is used as a superconducting member cooling vessel without performing special vacuum sealing, etc. We have proposed a superconducting member cooling device that can improve the superconducting performance by cooling the superconducting member and suppress the generation of gas bubbles from liquid nitrogen due to heat generated by the high-temperature superconducting member when the high-temperature superconducting member operates. ing.

[0007] The superconducting member cooling device proposed above basically has a configuration in which a cooling container for accommodating the superconducting member and cooling the superconducting member is substantially opened to the atmospheric pressure.
Liquid nitrogen in a supercooled state at atmospheric pressure, for example, about 67K is disposed in the cooling container, and the superconducting member is cooled by the liquid nitrogen in a supercooled state at the atmospheric pressure. Further, in the superconducting member cooling device proposed above, liquid nitrogen in a supercooled state at atmospheric pressure, which functions as a cooling medium for the superconducting member, is obtained as follows. That is, a decompression container is provided separately from the cooling container described above, and a heat exchanger is provided in the decompression container, and a liquid nitrogen for heat exchange (for example, an atmospheric pressure of about 77K) is provided in the decompression container. Saturated liquid nitrogen) is supplied, and the pressure in the pressure reducing container is reduced by a vacuum pump, and the temperature of the liquid nitrogen in the pressure reducing container is reduced from atmospheric pressure to a low temperature of, for example, 65K. On the other hand, apart from the liquid nitrogen for heat exchange, liquid nitrogen for cooling at atmospheric pressure (for example, saturated liquid nitrogen of about 77K) is led to the heat exchanger, where the pressure is reduced by 65K in the depressurizing vessel in the heat exchanger. The liquid nitrogen for heat exchange is heat-exchanged, and is cooled, for example, to about 67 K while maintaining the atmospheric pressure, and is brought into a supercooled state at the atmospheric pressure.
Then, supercooled liquid nitrogen of, for example, 67 K under superatmospheric pressure at this atmospheric pressure is introduced into the above-described cooling container, and the superconducting member is cooled to 67 K.
Cooling to a low temperature close to K (for example, 70K) is performed.

In the superconducting member cooling device proposed in Japanese Patent Application No. 8-232566, the temperature of the superconducting member can be reduced to a lower temperature than in a case where saturated liquid nitrogen at atmospheric pressure of about 77 K is used as a cooling medium. The superconducting member can be cooled, so that the performance of the superconducting member can be improved. In this case, the space above the surface of the supercooled cooling liquid nitrogen in the cooling vessel is largely evaporated from the cooling liquid nitrogen. Since it is filled with nitrogen gas at atmospheric pressure, it is unlikely that atmospheric pressure air containing moisture will be sucked in from the outside.Therefore, sealing of the lid of the cooling vessel, the current introduction terminal, etc. must be particularly strict. Further, since the cooling liquid nitrogen in which the superconducting member is immersed is in a supercooled state as described above, even if the superconducting member generates heat during the operation of the superconducting member, the superconducting member is heated around the heat generation site. There is a temperature margin to the body nitrogen reaches the vaporization temperature, therefore is not immediately generated gas bubbles,
Therefore, there is an advantage that there is little possibility that the insulating property or the cooling efficiency is reduced by the gas bubbles.

[0009] By conducting experiments and studies for practical use of the superconducting member cooling device proposed above, the following problems were found.

That is, in the superconducting member cooling apparatus proposed above, liquid nitrogen for heat exchange is supplied into the depressurizing vessel separately from liquid nitrogen for cooling, and the inside of the depressurizing vessel is depressurized by a vacuum pump to generate heat. Reduce the temperature of the replacement liquid nitrogen,
The liquid nitrogen for heat exchange and the liquid nitrogen for cooling whose temperature has dropped are exchanged with each other to obtain liquid nitrogen for cooling in a supercooled state at atmospheric pressure. The liquid nitrogen is gradually evaporated and vaporized by the decompression, and the vaporized gas is exhausted by the pump, so that the liquid nitrogen liquid level in the decompression container drops rapidly, and finally heat exchange in the decompression container The vessel will be exposed. If the heat exchanger is exposed from the liquid surface in this manner, sufficient heat exchange efficiency cannot be obtained, and it becomes difficult to cool the cooling liquid nitrogen to a sufficiently supercooled state. In practice, before the heat exchanger is exposed from the liquid surface, liquid nitrogen must be replenished into the depressurizing vessel, and the operation must be stopped once during the liquid nitrogen replenishment.

As described above, the proposed superconducting member cooling device has a problem that the operation cannot be continuously performed for a long time because the operation must be stopped to supply the liquid nitrogen in the depressurizing container. In addition, there is a problem that the labor for replenishing liquid nitrogen and for stopping and restarting the operation for the liquid nitrogen is also complicated. Of course, there is no particular problem in the case of short-time operation, but in experiments, research, measurement, etc. for the practical use of superconducting members, continuous operation for a long time is often required, and The fact is that replenishment of the container with liquid nitrogen for heat exchange has been a major bottleneck to the spread of the proposed device.

The present invention has been made in view of the above circumstances. Basically, similar to the above-mentioned proposal, while using liquid nitrogen supercooled at atmospheric pressure as a cooling medium for a superconducting member, the present invention The use of a decompression vessel or heat exchanger as in the case of, and the accompanying shutdown of replenishment of liquid nitrogen for heat exchange into the decompression vessel can be avoided for a long time It is an object of the present invention to provide a superconducting member cooling device which enables continuous operation of the superconducting member.

[0013]

In order to solve the above-mentioned problems, a superconducting member cooling apparatus according to the present invention comprises:
Liquid nitrogen is cooled by a refrigerator to a temperature at which it is supercooled under atmospheric pressure, and the obtained low-temperature liquid nitrogen in a supercooled state at atmospheric pressure is directly used as a cooling medium for directly cooling the superconducting member. I have.

More specifically, a superconducting member cooling apparatus according to a first aspect of the present invention includes a superconducting member for accommodating the superconducting member and cooling the superconducting member, the cooling container being substantially open to the atmosphere, and supplying the cooling container. A supply-side container substantially open to atmospheric pressure for containing liquid nitrogen to be supplied, liquid nitrogen supply means for supplying liquid nitrogen to the supply-side container, and liquid nitrogen in the supply-side container. A refrigerator for cooling under superatmospheric pressure to a supercooling temperature, and transfer means for transferring liquid nitrogen cooled to supercooling temperature under atmospheric pressure in the supply-side container to the cooling container. Wherein the superconducting member is immersed in supercooled liquid nitrogen at atmospheric pressure supplied by the transfer means into the cooling vessel so as to leave a space above the liquid surface. It is.

In the superconducting member cooling apparatus according to the first aspect of the present invention, the liquid nitrogen supplied to the supply side container which is substantially open to the atmospheric pressure (for example, about 77K under the atmospheric pressure)
Liquid nitrogen) is further cooled by a refrigerator under atmospheric pressure in the container and the temperature thereof drops, for example, to 65K.
The temperature drops to a low temperature. That is, it is supercooled under the atmospheric pressure. Then, under the atmospheric pressure, the liquid nitrogen supercooled to, for example, about 65K is led to a cooling vessel substantially opened to the atmosphere, and the superconducting member immersed in the liquid nitrogen is cooled to a low temperature of, for example, about 67 to 70K. Can be cooled. In other words, the cooling can be performed to a lower temperature than in the case where the normal saturated liquid nitrogen of about 77K is used.

Here, in the supply-side container, the liquid nitrogen is cooled to a supercooling temperature by a refrigerator under atmospheric pressure, so that the liquid nitrogen in the container is rapidly vaporized as in the case where the temperature is lowered by reducing the pressure. And the liquid nitrogen in the cooling container and the supply side container is maintained at a constant level without decreasing. Therefore, after a predetermined amount of liquid nitrogen is initially injected, continuous operation can be performed for a long time without replenishing the respective containers with liquid nitrogen.

The cooling vessel is substantially open to the atmosphere, and the space above the liquid nitrogen level in the cooling vessel is filled with atmospheric nitrogen vaporized from the liquid nitrogen in the cooling vessel. In addition, there is little possibility that atmospheric pressure air containing moisture is sucked into the inside from outside, and therefore, the sealing of the lid portion of the cooling vessel, the current introduction terminal, and the like does not need to be particularly strict. Further, since the liquid nitrogen in which the superconducting member is immersed is in a supercooled state as described above, even if the superconducting member generates heat during the operation of the superconducting member, it takes a temperature for the liquid nitrogen to reach the vaporization temperature around the heat generating portion. Since there is a margin, gas bubbles are not immediately generated, and therefore, there is no possibility that the gas bubbles may lower insulation properties or lower cooling efficiency.

Also, the supply side container is substantially open to the atmosphere as in the case of the cooling container, so that strictness is not required for sealing the lid and the like as in the case of the cooling container.

The superconducting member cooling device according to a second aspect of the present invention is the superconducting member cooling device according to the first aspect, wherein the supercooled liquid nitrogen is substantially below the liquid level in the supercooled state in the cooling container that is substantially open to the atmosphere. Further, the heat insulating member is immersed in a position above the superconducting member.

In the superconducting member cooling device according to the second aspect of the present invention, the liquid nitrogen on the upper surface side of the heat insulating member and the heat insulating member are provided by the heat insulating member below the liquid nitrogen in a supercooled state in the cooling vessel. A temperature gradient is actively formed between the temperature of the liquid nitrogen and the liquid nitrogen on the lower side, and the temperature of the liquid nitrogen on the upper surface side of the heat insulating member and the temperature of the liquid nitrogen on the lower side of the heat insulating member by convection stirring Can be prevented from being made isothermal. As a result, the temperature of the portion where the superconducting member is provided can be maintained at a low temperature, and the superconducting member can be cooled and maintained at a sufficiently low temperature.

The superconducting member cooling apparatus according to a third aspect of the present invention is the superconducting member cooling apparatus according to the first aspect, wherein the space above the liquid surface of the supercooled liquid nitrogen in the cooling vessel substantially open to the atmosphere. Is provided with nitrogen gas supply means for supplying nitrogen gas at atmospheric pressure.

In the superconducting member cooling apparatus according to the third aspect of the present invention, the space above the liquid nitrogen in a supercooled state in the cooling vessel is filled with nitrogen gas at atmospheric pressure supplied from the outside. Therefore, the space above the liquid nitrogen level is reliably prevented from being decompressed, and the atmosphere containing moisture is reliably and effectively prevented from invading from the lid of the cooling vessel, the current introduction terminal, and the like. can do.

According to a fourth aspect of the present invention, there is provided a superconducting member cooling apparatus according to the first aspect, wherein the superconducting member cooling apparatus is provided below the liquid nitrogen level in the supply side container which is substantially open to the atmosphere. In addition, the heat insulating member is immersed in a position above a position where the liquid nitrogen is pumped toward the cooling container by the transfer means.

In the cooling device for a superconducting member according to the fourth aspect of the present invention, the heat insulating member below the liquid nitrogen level in the supply-side container allows the liquid nitrogen on the upper surface side of the heat insulating member and the lower side of the heat insulating member. A temperature gradient is actively formed between the liquid nitrogen and the temperature of the liquid nitrogen, and the temperature of the liquid nitrogen on the upper surface side of the heat insulating member and the temperature of the liquid nitrogen below the heat insulating member are isothermal due to convection agitation. Can be prevented. As a result, the temperature of the portion where liquid nitrogen is pumped out to the cooling container is maintained at a low temperature, and sufficiently low-temperature liquid nitrogen can be supplied to the cooling container.

The superconducting member cooling device according to a fifth aspect of the present invention is the superconducting member cooling device according to the first aspect, wherein the space above the liquid surface of the liquid nitrogen in the supply side container which is substantially open to the atmosphere has an atmospheric pressure. Nitrogen gas supply means for supplying the nitrogen gas.

In the superconducting member cooling apparatus according to the fifth aspect of the present invention, the space above the liquid nitrogen level in the supply-side container is filled with nitrogen gas at atmospheric pressure supplied from the outside. It is possible to reliably prevent the space above the liquid level of nitrogen from being decompressed, and to reliably and effectively prevent the atmosphere containing moisture from entering from the lid of the supply-side container.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

[0028]

FIG. 1 shows a superconducting member cooling apparatus according to an embodiment of the present invention.

In FIG. 1, a superconducting member 1 to be cooled is arranged at the bottom of a cooling vessel 3. The cooling vessel 3 is composed of a general-purpose cryostat substantially open to the atmosphere, the outer peripheral wall and the bottom wall of which are a vacuum heat insulating structure 5, and the upper end is openable and closable. A lid 7 is provided. The lid 7 is not vacuum-sealed with respect to the container body, and the lid 7 is provided with a current introduction terminal similar to that of a general-purpose cryostat. The inside of the cooling container 3 is substantially open to the atmosphere through a gap between the container main body and a current introduction terminal. Note that a safety valve 19 is provided on the lid 7, and the safety valve 19 is
Internal pressure is, for example, +0.1 kgf with respect to external atmospheric pressure
/ Cm ² and functions to maintain the internal pressure within a substantial atmospheric pressure range from atmospheric pressure to atmospheric pressure + 0.1 kgf / cm ² . The superconducting member 1 is suspended from the lid 7 by supporting members 9A and 9B. Liquid nitrogen (cooling liquid nitrogen) 11 which is supercooled at atmospheric pressure is supplied to the bottom of the cooling vessel 3 via a transfer tube 45 as described later, and the superconducting member 1 is immersed in the liquid nitrogen 11. Is done. At a position slightly below the liquid level 11A of the liquid nitrogen 11 in the cooling vessel 3, the outer shape of the horizontal cross section is substantially similar to the inner circumferential shape of the horizontal cross section of the cooling vessel 3. In addition, a heat insulating member 13 having a predetermined thickness in the vertical direction is provided. In short, the heat insulating member 13 may be made of a material having a small thermal conductivity such as FRP, or a hollow material, as long as the heat conduction in the vertical direction as a whole is much smaller than that of liquid nitrogen. The hollow portion may have a vacuum insulation structure. The heat insulating member 13 is suspended from the lid 7 by the support members 9A and 9B described above, and the periphery of the heat insulating member 13 keeps a slight gap 14 with respect to the inner peripheral wall surface of the cooling container 3. Made in. On the other hand, a space (space between the lid 7 and the liquid surface 11A) 15 left above the liquid surface 11A of the cooling liquid nitrogen 11 in the cooling container 3 is supplied from an external first nitrogen gas supply source 16 to the space 15. Atmospheric pressure nitrogen gas is supplied through a nitrogen gas supply pipe 18. A reflux pipe 17 to be described later is provided at a position on the lower surface side of the heat insulating member 13 in the cooling vessel 3.
Is open at the base end side.

Further, a supply side container 21 is provided separately from the cooling container 3 which is substantially open to the atmosphere as described above.

The supply-side container 21 is substantially open to the atmosphere similarly to the cooling container 3 described above. The outer peripheral wall and the bottom wall of the supply-side container 21 are formed of a vacuum heat insulating structure 23. A lid 25 that can be opened and closed is provided. This lid 2
5 is not vacuum-sealed with respect to the container body, and the inside of the supply-side container 21 is substantially open to the atmosphere through such a gap between the lid 25 and the container body. Has become. The supply side container 21 is supplied with liquid nitrogen 33 from an external liquid nitrogen supply source 27 via a control valve 29 and a supply pipe 31. The liquid level 33 of the liquid nitrogen 33 in the supply side container 21
At a position slightly lower than A, a heat insulating member 35 having an outer shape of a horizontal cross section substantially similar to the horizontal cross sectional shape of the supply-side container 21 and having a predetermined thickness in the vertical direction, It is disposed in a state of being suspended from the lid 25 by the support members 37A and 37B. This heat insulating member 35
Also, as with the heat insulating member 13 in the cooling vessel 3, the heat transfer in the vertical direction as a whole may be much less than that of liquid nitrogen, and is made of a material having a low thermal conductivity such as FRP. Or a hollow vacuum insulation structure. Further, the periphery of the heat insulating member 35 has a slight gap 39 with respect to the inner peripheral wall surface of the supply-side container 21, similarly to the heat insulating member 13 in the cooling container 3.

Further, a refrigerator 41 is disposed on the lid 25 of the supply container 21, and a cooling head 41 A extending from the refrigerator 41 is below the liquid nitrogen level in the supply container 21. In addition, the cooling head 41A of the refrigerator 41 immerses the liquid nitrogen 33 in the supply-side container 21 below the temperature of the saturated liquid nitrogen under the atmospheric pressure. The cooling is performed to a cooling temperature (a temperature lower than about 77K). Further, a liquid feed pump 43 is provided in the supply side container 21 in a state of being suspended from the lid 25. This liquid sending pump 43
Is disposed such that its inlet (pump outlet) is located below the heat insulating member 35 in the supply-side container 21 (normally near the bottom of the supply-side container 21). The outlet side of the liquid supply pump 43 is connected to a transfer tube 45, and the transfer tube 45 is guided into the cooling container 3 as described above. Further, the reflux pipe 17 from the cooling vessel 3 is guided into the supply-side vessel 21, and the open end of the reflux pipe 17 has the bottom end of the supply-side vessel (below the cooling head 41 A of the refrigerator 41. Position).

The liquid nitrogen 33 in the supply side container 21
Space above the liquid level 33A (the lid 25 and the liquid level 3).
Atmospheric pressure nitrogen gas is supplied from an external second nitrogen gas supply source 49 via a nitrogen gas supply pipe 51 to the space 47 between the space 3A and the space 47.

Here, the liquid nitrogen supply source 27 and the control valve 2
The supply pipe 9 and the supply pipe 31 constitute liquid nitrogen supply means 63 for supplying liquid nitrogen to the supply side container 21.
Further, the liquid sending pump 43 and the transfer tube 45
Constitutes a transfer means 65 for transferring liquid nitrogen, which has been cooled to a supercooled state at atmospheric pressure in the supply-side container 21, to the cooling container 3. On the other hand, the first nitrogen gas supply source 1
6. The nitrogen gas supply pipe 18 constitutes a first nitrogen gas supply means 67 for supplying nitrogen gas at atmospheric pressure to the space 15 above the liquid level in the cooling vessel 3, and a second nitrogen gas supply means 67. The supply source 49 and the nitrogen gas supply pipe 51 are connected to the supply side container 2.
A second nitrogen gas supply means 69 for supplying nitrogen gas at atmospheric pressure to the space 47 above the liquid surface in FIG.

The overall function of the superconducting member cooling apparatus of the embodiment shown in FIG. 1 will be described below.

The liquid nitrogen supply source 2 of the liquid nitrogen supply means 63
7 supplied to the supply side container 21 from the
However, the liquid nitrogen is cooled under the atmospheric pressure in the supply side container 21 by the cooling head 41A of the refrigerator 41, and the saturated liquid nitrogen temperature (77
(About K), for example, about 65K. Then, the liquid nitrogen 33 at atmospheric pressure supercooled to about 65K is pumped up from the vicinity of the bottom of the supply side container 21 by the liquid sending pump 43, and is substantially opened to the atmosphere via the transfer tube 45. 3
Guided inside. The supercooled state liquid nitrogen in the supercooled state introduced into the cooling container 3 is indicated by reference numeral 11 in FIG. 1 and corresponds to the cooling liquid nitrogen.

In the cooling vessel 3, the superconducting member 1 is cooled and held at, for example, about 67K by the liquid nitrogen 11 at the atmospheric pressure in a supercooled state of, for example, 65K as described above. In the cooling vessel 3, the liquid nitrogen whose temperature has risen to, for example, about 70 K by heat from the superconducting member 1 returns to the supply side vessel 21 via the reflux pipe 17. The fluid nitrogen refluxed to the supply-side container 21 in this manner is again cooled to about 65K under atmospheric pressure by the cooling head 41A of the refrigerator 41, and is again sent to the cooling container 3 by the liquid sending pump 43 as described above. Will be done.

Here, nitrogen gas at atmospheric pressure is introduced into the space 15 above the liquid surface 11A of the cooling liquid nitrogen 11 in the cooling vessel 3 through a nitrogen gas supply pipe 18. Therefore, the space 15 above the liquid surface of the cooling container 3 is filled with nitrogen gas at atmospheric pressure. Therefore, the pressure in the cooling container 3 is reliably maintained at the atmospheric pressure, and the air is reliably prevented from being drawn in from the outside via the sealing portion of the lid 7 and the current introduction terminal portion.

Further, since the heat insulating member 13 is provided below the liquid level of the cooling liquid nitrogen 11 in the cooling container 3,
Liquid surface of cooling liquid nitrogen 11 (approximately 77
K) and its lower side than the heat insulating member 13, especially the superconducting member 1
It is possible to reliably provide a thermal gradient with the bottom of the cooling vessel where is located. Also, the presence of the heat insulating member 13 prevents convection agitation between the liquid surface 11A and the bottom side. As a result, the cooling liquid nitrogen 11 at the bottom where the superconducting member 1 is located can be reliably maintained in a supercooled state at a low temperature of about 65K. Since the superconducting member 1 is thus surrounded by the low-temperature liquid nitrogen 11 in a supercooled state of, for example, 65K, even if the superconducting member 1 generates heat during the operation of the superconducting member 1, the surrounding liquid nitrogen is kept at atmospheric pressure. There is a margin of about 10K or more before reaching the lower vaporization temperature (about 77K), so that the heat generated by the superconducting member 1 effectively vaporizes the surrounding liquid nitrogen and immediately generates gas bubbles. Can be prevented.

The liquid nitrogen 3 in the supply side container 21
Atmospheric pressure nitrogen gas is also introduced into the space 47 above the third liquid level 33A via the nitrogen gas supply pipe 51. Therefore, the space 47 above the liquid surface of the supply side container 21 is also filled with the nitrogen gas at the atmospheric pressure. Therefore, the pressure in the supply-side container 21 is reliably maintained at the atmospheric pressure, and air is reliably prevented from being drawn in from the outside and entering through the sealed portion of the lid 25 or the like.

Further, similarly to the cooling container 3, the supply-side container 21
The heat insulating member 35 is also provided below the liquid surface of the liquid nitrogen 33 in the inside, so that the liquid surface of the liquid nitrogen 33 (about 77 K because of the gas-liquid interface) and the lower side than the heat insulating member 35,
Particularly, a thermal gradient can be reliably provided between the liquid feeding pump 43 and the vicinity of the inlet. In addition, the presence of the heat insulating member 35 prevents convection agitation between the vicinity of the liquid surface 33A and a portion below the heat insulating member 35. As a result, the liquid nitrogen 33 in the vicinity of the inlet of the liquid sending pump 43 is surely maintained in a low-temperature supercooled state of about 65K.
Liquid nitrogen in a supercooled state at a low temperature of about 5K can be sent to the cooling container 3.

In the above embodiment, nitrogen gas at atmospheric pressure is introduced into the space 15 above the liquid surface 11A of the cooling liquid nitrogen 11 in the cooling container 3 through the nitrogen gas supply pipe 18. In some cases, a configuration in which nitrogen gas at atmospheric pressure is not positively introduced into the space 15 may be adopted. That is, when the liquid surface 11A of the cooling liquid nitrogen 11 in the cooling container 3 is high (the liquid surface 11A is
), It is possible to maintain the liquid-gas equilibrium state of nitrogen under the atmospheric pressure at the liquid surface 11A due to the heat penetrating from the lid 7, and therefore, the space above the liquid surface 11A By maintaining the pressure at 15 substantially at atmospheric pressure, it is possible to prevent the suction of air from the outside and to fill the space 15 with nitrogen gas at atmospheric pressure by vaporization from the liquid surface 11A. However, in order to surely fill the space 15 with nitrogen gas at atmospheric pressure, it is of course desirable to positively introduce nitrogen gas at atmospheric pressure from the outside as described above.

The liquid nitrogen 33 in the supply side container 21
The same applies to the space 47 above the liquid surface 33A. In this case, a configuration in which nitrogen gas at atmospheric pressure is not actively introduced into the space 47 from the outside may be adopted in some cases.

[0044]

According to the superconducting member cooling device of the first aspect of the present invention, as a cooling medium for immersing and cooling the superconducting member, liquid nitrogen in a supercooled state at atmospheric pressure, that is, liquid nitrogen in a saturated state at atmospheric pressure. Since liquid nitrogen at a lower temperature is used, the superconducting member can be cooled and held at a lower temperature to further improve its performance, and the space above the liquid surface of the liquid nitrogen is nitrogen gas at atmospheric pressure. Therefore, a general-purpose inexpensive cryostat that is substantially open to the atmosphere can be used as the cooling container that contains the superconducting member and the liquid nitrogen, and thus the cost can be reduced. Further, as described above, since the superconducting member is immersed in the supercooled liquid nitrogen and the superconducting member is surrounded by the supercooled liquid nitrogen, gas bubbles are generated due to heat generation of the superconducting member during operation of the superconducting member. The generation of gas bubbles can be effectively prevented, so that the generation of gas bubbles is less likely to cause a decrease in electrical insulation and a decrease in cooling efficiency.

Further, in the superconducting member cooling apparatus according to the first aspect of the present invention, the cooling liquid nitrogen for cooling the superconducting member is supercooled at atmospheric pressure in the supply side container opened to atmospheric pressure. Since the liquid nitrogen is directly cooled to the atmospheric supercooling temperature by the refrigerator, the liquid nitrogen for heat exchange is cooled to the atmospheric supercooling temperature by decompression and the liquid nitrogen for heat exchange and the liquid nitrogen for cooling are heated. Unlike the case of replacement, the decompression container, the heat exchanger and the liquid nitrogen for heat exchange are not required, so that the cost of the entire apparatus can be reduced, and it is not necessary to stop the operation for replenishing the liquid nitrogen. Therefore, continuous operation can be performed for a long period of time, and labor for stopping and restarting operation for replenishing liquid nitrogen is not required.

In the superconducting member cooling device according to the second aspect of the present invention, a heat insulating member is disposed below the liquid level of the supercooled liquid nitrogen in the cooling container so that the superconducting member at the bottom in the cooling container is provided. The liquid nitrogen at the portion where the member is disposed can be reliably maintained in a supercooled low temperature state, so that the effect of the first aspect of the present invention can be more reliably exerted.

Further, according to the superconducting member cooling device of the third aspect of the present invention, nitrogen gas at atmospheric pressure is positively introduced into the space above the liquid surface of the cooling vessel, so that the pressure in the space is reliably increased to atmospheric pressure. By maintaining, it is possible to more reliably prevent the invasion of the outside air from the lid or the like.

On the other hand, in the superconducting member cooling apparatus according to the fourth aspect of the present invention, by providing a heat insulating member below the liquid nitrogen level in the supply side container, a bottom portion in the supply side container, that is, the cooling container The liquid nitrogen at a portion where liquid nitrogen is pumped toward the liquid nitrogen can be reliably maintained in a supercooled low temperature state, and the low temperature liquid nitrogen can be supplied to the cooling container. Can be exhibited more reliably.

Further, according to the superconducting member cooling apparatus of the fifth aspect of the present invention, nitrogen gas at atmospheric pressure is positively introduced into the space above the liquid surface of the supply side container, so that the pressure in the space is reliably reduced to atmospheric pressure. , It is possible to more reliably prevent outside air from entering from the lid and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a superconducting member cooling device according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 superconducting member 3 cooling container 11 cooling liquid nitrogen 13 heat insulating member 21 supply side container 35 heat insulating member 41 refrigerator 63 liquid nitrogen supply means 65 transfer means 67 first nitrogen gas supply means 69 second nitrogen gas supply means

Claims (5)

[Claims] A cooling vessel, substantially open to the atmosphere, for containing and cooling the superconducting member;
A supply-side container substantially open to atmospheric pressure for containing liquid nitrogen to be supplied to the cooling container; liquid nitrogen supply means for supplying liquid nitrogen to the supply-side container; A refrigerator for cooling liquid nitrogen in the container to a supercooling temperature under atmospheric pressure; and for transferring liquid nitrogen cooled to a supercooling temperature under atmospheric pressure in the supply-side container to the cooling container. Transfer means; and so that the superconducting member is immersed in supercooled liquid nitrogen at atmospheric pressure supplied into the cooling vessel by the transfer means so as to leave a space above the liquid surface. A superconducting member cooling device, characterized in that: 2. The superconducting member cooling device according to claim 1, wherein the superconducting member is below a liquid nitrogen level in a supercooled state under atmospheric pressure in the cooling vessel substantially open to the atmosphere and above the superconducting member. A superconducting member cooling device in which a heat insulating member is immersed in a position. 3. A superconducting member cooling apparatus according to claim 1, wherein nitrogen gas at atmospheric pressure is supplied to a space above the liquid surface of liquid nitrogen in an atmospheric pressure supercooled state in said cooling vessel substantially open to the atmosphere. Superconducting member cooling device provided with a nitrogen gas supply means for performing the operation. 4. The superconducting member cooling device according to claim 1, wherein the liquid nitrogen is directed to the cooling container by the transfer means under the liquid nitrogen level in the supply-side container substantially open to the atmosphere. A superconducting member cooling device in which a heat insulating member is immersed in a position above a position where the heat is drawn out. 5. The superconducting member cooling apparatus according to claim 1, wherein nitrogen gas at atmospheric pressure is supplied to a space above the liquid nitrogen level in the supply-side container substantially open to the atmosphere. A superconducting member cooling device comprising a supply means.