JP2982310B2 - Heat shield plate cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling system for a heat shield plate of a cryogenic vessel containing, for example, a superconducting coil.

[0002]

2. Description of the Related Art As a prior art, a superconducting coil for a magnetic levitation type railway and a cryogenic container accommodating the coil will be described as an example. FIG. 2 shows a superconducting magnet for a magnetically levitated railway described in a document (IEEE / Linear Drive Research Group Material (1988-4-26), page 27). In the figure,
2 is an inner tank containing a superconducting coil and liquid helium as a refrigerant, 3 is a liquid helium tank for supplying liquid helium to the inner tank 2, 4 is a heat shield plate covering the inner tank 2 and the liquid helium tank 3, 7 Is a permanent current switch for operating the superconducting coil in the permanent current mode, 8 is a load supporting member for supporting the inner tank 2 insulated, 6 is the inner tank 2, liquid helium tank 3, heat shield plate 3, permanent This is an outer tank, that is, a cryogenic vacuum vessel, in which components such as the current switch 7 and the load support member 8 are stored. Reference numeral 9 denotes a cooling pipe for supplying liquid nitrogen from a liquid nitrogen tank (not shown) by a liquid nitrogen pump.

The operation of the superconducting magnet configured as shown in FIG. 2 will be described with a focus on heat shielding. A superconducting coil is accommodated in the inner tank 2 and is filled with liquid helium supplied from the helium tank 3 to maintain the superconducting coil in a superconducting state. The superconducting coil 2 is supplied with a current from an exciting power supply (not shown), and is operated in a permanent current mode by using a permanent current switch 7. To operate the superconducting coil and the persistent current switch, it is necessary to maintain the superconducting state. For this purpose, it is necessary to minimize the intrusion of heat from the outside into the inner tank 2, and many measures have been taken. For example, the heat shield plate 4
Installation. The heat-insulating load supporting member 8 is a measure for reducing heat penetration due to heat conduction from the outer tub 6 to the inner tub 2, and the heat shield plate 4 is also a measure for reducing heat penetration due to heat radiation. The heat shield plate 4 is usually cooled to a liquid nitrogen temperature (77.3K under one atmosphere).
In this conventional example, liquid nitrogen is passed through the cooling pipe 9 to maintain the temperature near the liquid nitrogen temperature. That is,
The cooling pipe 9 is guided from a liquid nitrogen tank (not shown). In the present apparatus, liquid nitrogen is forcibly circulated in the cooling pipe 9 by a liquid nitrogen pump attached to the liquid nitrogen tank.
The heat shield plate 4 is maintained near the temperature of liquid nitrogen. Of course, heat radiation from the outer bath 6 also exists in the heat shield plate 4, but the amount of heat penetration is covered by liquid nitrogen which is cheaper than liquid helium. It can be called thought.

In the prior art, a liquid nitrogen tank is separately provided and liquid nitrogen is forcibly flowed by a circulation pump. As an improved version, an integrated type in which a liquid nitrogen tank is placed on the liquid helium tank 3 side is used. Conceivable. This type is excellent in that it is compact as a system and that it is a distributed type, so that it has redundancy against failures. The most ideal configuration is to arrange a liquid nitrogen tank around the liquid helium tank, but it is often difficult to save weight or space, in which case the liquid helium tank and the liquid nitrogen tank are arranged side by side I have to adopt a configuration. However, in this type, the supply of the liquid nitrogen to the cooling pipe 9 attached to the heat shield plate is performed by the self-pressure supply by the pressure in the liquid nitrogen tank or the self-weight drop supply by the weight of the liquid nitrogen itself. Become.

[0005]

The conventional superconducting magnet has the following problems because it is constructed and operates as described above.

When using a forced circulation device for liquid nitrogen,
Liquid nitrogen pump is expensive, pump installation space
Requirements, heavy equipment, pumps
Power (motor) to drive, heat from pump
That the load accelerates the evaporation of liquid nitrogen,
Not be affected by the large magnetic field generated by the conducting coil
In addition, there are various problems such as restrictions on the installation location of the pump.
There is. In addition, when the circulating pump becomes abnormal, the pressure in the liquid nitrogen tank is increased and the liquid nitrogen is self-supplied to cope with this.However, auxiliary equipment such as a valve is required, and the operation control function is also provided. Required. Therefore, the self-weight drop method has a simpler configuration and has an advantage that it is easy to drive.

However, in the self-weight dropping method, the cooling pipe must be attached to the heat shield plate at an angle at which the effect of the self-weight can be expected. In other words, there is a disadvantage that the cooling pipe cannot be installed in the horizontal direction.If the liquid nitrogen tank and the heat shield plate are located in the horizontal direction, cooling of the heat shield plate must rely only on the heat conduction of the shield material. There was a problem that the heat shield plate could not be cooled well in many cases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a heat shield plate and a liquid nitrogen bath which are disposed horizontally in a horizontal position, so that the heat shield plate is small and light, and the heat shield plate is efficiently cooled. The purpose is to obtain a heat shield system that can be used.

[0009]

A heat shield plate cooling system according to the present invention has a liquid nitrogen tank and a heat shield plate installed in a horizontal positional relationship, and a lower cooling pipe introduced from a lower portion of the liquid nitrogen tank and a liquid. an upper cooling pipe introduced from the top of the nitrogen tank communicates at a distance with the liquid nitrogen tank, by the inside of the cooling pipe above liquid nitrogen Ru can circulate freely Unishi, at least the lower cooling the pipe The pipe is configured to be in a state in which the liquid nitrogen is stored, and the pipe and the heat shield plate are thermally connected.

[0010]

[Function] In the heat shield system configured as described above, when the self-weight drop method cannot be used due to the positional relationship between the liquid nitrogen tank and the heat shield plate, or when the conduction distance from the liquid nitrogen tank is long, cooling is performed only by conduction. Even with a difficult heat shield plate, heat can be transferred between the liquid nitrogen tank and the heat shield plate satisfactorily, and the temperature of the heat shield plate can be maintained at a sufficiently low temperature.

[0011]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings.
In FIG. 1, 1 is a superconducting coil, 2 is an inner tank, 3 is a liquid helium tank, 4a is a heat shield plate around the inner tank, 4b is a heat shield plate around the liquid helium tank, 5 is a liquid nitrogen tank, and 5a is a liquid. A lower cooling pipe section introduced from the lower part of the nitrogen tank, 5b is an upper cooling pipe section introduced from the upper part of the liquid nitrogen tank, 5c is a communicating pipe section for communicating the cooling pipes 5a and 5b, 5d and 5e are evaporative nitrogen gas. Exhaust pipe part , and at least a lower cooling pipe part 5a and an upper part
A piping structure is formed by the cooling piping portion 5b and the communication piping portion 5c.
Constitute. Reference numeral 6 denotes a vacuum vessel, that is, an outer tank. In this figure, a cooling pipe extending to the heat shield part 4a is omitted.

The basic operation of the superconducting magnet thus configured is the same as that of the conventional example, except for the cooling method of the heat shield plate 4b.

A more detailed description will be given. Considering the conventional example,
The cooling of the heat shield plate 4b had to rely on the thermal conductivity of the heat shield plate itself. That is, in the horizontal direction, a fall due to its own weight cannot occur. However, by installing the communication pipe as in the present embodiment, liquid nitrogen also accumulates in the cooling pipes 5a and 5c, and the liquid nitrogen accumulates at the lower and end portions of the heat shield plate 4b. Configuration. Therefore, the cooling characteristic of the heat shield plate is remarkably improved as compared with the case where the liquid nitrogen tank 5 is used as a cold generation part and only depends on the heat conduction of the shield material. This is because the heat conduction distance becomes very short. For example, in a normal superconducting magnet, the temperature of the liquid nitrogen tank 5 needs to be suppressed to about 78K, and the temperature of the heat shield plate 3 needs to be suppressed to about 100K at most. Although depending on the conditions, even when the temperature of the heat shield plate becomes 100K or more when cooled only by heat conduction, the temperature of the heat shield plate can be set to about 80 to 90K by installing the communication pipe as in the present embodiment. .

The reason why the exhaust pipe section 5d is provided is that a cooling effect by gas flow in the upper cooling pipe section 5b can be expected by allowing the evaporated nitrogen gas in the liquid nitrogen tank 5 to escape from the exhaust pipe section. Of course, it is not necessary. Further, a plurality of communication pipes 5c may be provided, and a plurality of sets of these cooling communication pipes may be provided. Skillful implementation of these multiple configurations can further improve cooling performance

[0015]

As described above, according to the present invention, in a heat shield plate cooling system, a heat shield plate covering a storage tank containing liquid helium or a superconducting coil, and at least partially horizontal to the heat shield plate. A liquid nitrogen tank that is arranged in a positional relationship and contains liquid nitrogen for cooling the heat shield plate, a lower cooling pipe introduced from the lower part of the liquid nitrogen tank, and an upper cooling pipe introduced from the upper part of the liquid nitrogen tank. and a pipe structure that is communicating at a position apart from the liquid nitrogen tank, in at least a lower cooling pipe of the pipe structure
The liquid nitrogen is free while the liquid nitrogen is stored
As well as the above piping structure
Since the heat shield plate is thermally connected to the heat shield plate, the heat shield plate has the same effect as the presence of the liquid nitrogen tank at a necessary portion of the heat shield plate, and has the effect of obtaining good cooling characteristics. Also, there is an effect that the weight can be significantly reduced as compared with the configuration in which the liquid nitrogen tank is provided around the liquid helium tank.

Further, according to the present system , since it is not necessary to adopt the forced circulation system, there is no need to attach auxiliary parts such as a pressure regulating valve, and a small and lightweight apparatus can be obtained.
At the same time, the system configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a cryogenic container for a superconducting coil according to one embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional cryogenic container for a superconducting coil according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 superconducting coil 2 inner tank 3 liquid helium tank 4a heat shield plate covering inner tank 4b heat shield plate covering liquid helium tank 5 liquid nitrogen tank 5a lower cooling pipe 5b upper cooling pipe 5c communication pipe 5d connected to communication pipe Exhaust pipe 5e Exhaust pipe connected to liquid nitrogen tank 6 Outer tank 7 Permanent current switch 8 Adiabatic load support 9 Liquid nitrogen supply pipe

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-4309 (JP, A) JP-A-63-67706 (JP, A) JP-A-60-41271 (JP, A) 185806 (JP, U) JP-A-63-46808 (JP, U) JP 3-17057 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 39/04 F25D 3 /Ten

Claims (1)

(57) [Claims] 1. A heat shield plate for covering a storage tank containing liquid helium or a superconducting coil, and at least partially disposed in a horizontal positional relationship with the heat shield plate and containing liquid nitrogen for cooling the heat shield plate. with a liquid nitrogen tank, and a pipe structure that is communicating at a position where the upper cooling pipe introduced from the lower cooling pipe and the liquid nitrogen tank top introduced from the liquid nitrogen tank bottom away from the liquid nitrogen bath, Above
At least in the lower cooling pipe of the pipe structure, the liquid nitrogen
So that the liquid nitrogen can flow freely when
And the pipe structure and the heat shield plate
A heat shield plate cooling system, wherein the heat shield plate is thermally connected .