JPS62229887A - Cryostat - Google Patents

Abstract

PURPOSE:To reduce the quantity of intruded heat due to convection of gas in a pipe to a very small value, by providing the pipe, whose one end is communicated to a refrigerant container and other end is positioned at a normal temperature part, in a snaking pattern, in which a plurality of rising parts in the direction against gravity are provided. CONSTITUTION:A pipe 6a is used for injection of liquid helium, recovery of helium gas, guiding of gas cooling current leads and the like. The pipe 6a is composed of the following parts: a part 12, which vertical1y descends from a communicating hole 11 at the upper part of the side wall of a refrigerant container 3 enclosing a superconducting coil 1 and liquid helium 2 together; a vertical rising part 13; a vertical descending part 14; a vertical rising part 15; and a part 16, which horizontally extends and penetrates the wall of a vacuum container 5. The pipe is arranged in the snaking state so that the pipe is bent in the up and down directions and advances in the horizontal direction as a whole. When inclination of the rising part is within 20 degrees with respect to the direction of gravity, heat transfer in the rising part due to convection comes to have a very small value.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a cryostat used in superconducting equipment and the like.

(Prior Art) As is well known, a superconducting coil is used while being housed in a cryostat together with liquid helium to cool it. As shown in FIG. 3, a cryostat for a superconducting coil usually includes a refrigerant storage container 3 that accommodates the superconducting coil 1 and liquid helium 2 together, and a refrigerant storage container 3 that covers the refrigerant storage container 3 and is connected to the container 3. A vacuum container 5 in which a vacuum insulation layer 4 is formed, one end of which communicates with the upper space of the refrigerant storage container 3, and the other end of which penetrates through the walls of the vacuum insulation layer 4 and the vacuum container 5 and is located in a room temperature region. is installed for injection of liquid helium and recovery of helium gas.

It is composed of a pipe 6 used for guiding gas cooling current leads, etc.

By the way, in the cryostat configured as described above, one end of the pipe 6 communicates with the refrigerant storage container 3, and the other end is located in the room temperature section.

Heat intrusion through this piping 6 poses a problem. This heat intrusion is considered to be conduction intrusion directly through the piping components.

This can be classified into two types: intrusion due to convection of helium gas filling the pipe 6; By forming the pipe 6 with a material having high heat insulation properties, it is relatively easy to suppress heat intrusion directly through the pipe constituent materials.

Therefore, one problem is how to reduce the amount of heat intrusion due to convection of the helium gas filling the pipe 6. For this reason, in the conventional cryostat, as shown in Fig. 3, the piping 6 is made of a highly insulating material, and a spiral bent part 7 is provided in the middle of the piping to reduce heat intrusion due to convection. The method is adopted.

However, as mentioned above, there is a bend 7 in the middle of the pipe 6.
However, even if it is provided, there is a problem in that the amount of heat penetration cannot actually be suppressed to that extent.

(Problems to be Solved by the Invention) As described above, simply bending the piping in a spiral cannot suppress the amount of heat intrusion caused by the convection of the gas filling the piping.

Therefore, the present invention has a simple structure.

The object of the present invention is to provide a cryostat that can reliably suppress the amount of heat intrusion due to convection of gas filling the piping.

[Configuration of the Invention (Means for Solving Problems) The cryostat according to the present invention has a plurality of parts that rise at an inclination angle of within 20 degrees with respect to the direction of gravity, and the piping is arranged in a meandering relationship. It is set up.

(Operation) As mentioned above, the pipe is filled with refrigerant gas. In the case of a cryostat, the refrigerant gas present in the piping is not all at a uniform temperature, but has a temperature difference due to the influence of one position. If a part of the pipe has a rising part that is close to vertical, low-temperature gas moves downward within this rising part.

Gases with higher temperatures move upward. Therefore, temperature stratification is formed in the nearly vertical rising portion where convection is difficult to occur. In this case, if the inclination of the rising portion is within 20 degrees with respect to the direction of gravity, the heat transfer due to convection within the rising portion becomes a very small value.

Heat intrusion due to convection through the piping is suppressed.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cryostat according to an embodiment of the present invention, and the same parts as in FIG. 3 are designated by the same reference numerals. Therefore, a detailed explanation of the overlapping portion will be omitted.

This embodiment differs from the conventional one in the arrangement of the piping 6a, which is made of a highly insulating material.

That is, the piping 6a incorporated in the cryostat according to this embodiment includes a portion 12 vertically falling from the communication hole 11 provided at the upper side wall of the refrigerant container 3, and a portion 13 vertically rising from this portion 12. This part 1
3, a portion 15 vertically rising from this portion 14, and a portion 16 extending horizontally from this portion 15 and penetrating the wall of the vacuum vessel 5.

As a whole, it is arranged in a meandering state, bending vertically and moving horizontally.

With such a configuration, the temperature inside the pipe 6a is as follows.

Overall, the portion close to the communication hole 11 is the lowest.

The temperature of each part is as follows, although the temperature is highest in the part that protrudes to the outside. That is, in the 9th part 12, the low-temperature helium gas flowing out from the through hole 11 moves downward, so that the upper end temperature and the upper end temperature become almost equal. Further, in the 9 portion 13, low-temperature gas gathers at the lower end, and higher-temperature gas gathers at the upper end, resulting in a temperature difference between the lower end and the upper end. In the portion 14, since the low temperature gas moves toward the lower end, the temperature becomes approximately equal to that of the upper end and the lower end. Furthermore, in the portion 15, low-temperature gas gathers at the lower end, and higher-temperature gas gathers at the upper end, creating a temperature difference between the lower end and the upper end. Therefore, temperature stratification is formed within the first portion 13 and within the portion 15, in which convection is difficult to occur. Therefore, since the two portions 13 and 15 function as a heat insulating layer, it is possible to effectively suppress heat intrusion due to convection from the outside.

By the way, heat transfer occurs even under conditions where thermal stratification is formed. The inventors conducted an experiment to investigate the relationship between the inclination of the rising portion of the pipe with respect to the direction of gravity X and the amount of heat penetration, and obtained the results shown in FIG. 2. As can be seen from these results, the closer the slope of the rising portion of the piping is to horizontal, the greater the amount of heat penetration, and the closer it is to vertical, the smaller the amount of heat penetration. This seems to be due to changes in the heat capacity distribution across the temperature boundary layer.

In this embodiment, in the middle of the pipe 6a, there is a vertically rising portion 13 where the amount of heat intrusion is the least, that is, where convection is difficult to occur.
．． I'm trying to set up 15.

The amount of heat intrusion due to convection can be significantly reduced compared to conventional pipes in which a bend is simply provided in the pipe.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways. In other words, the slope of the rising portion 12.15 of the pipe 6a does not need to be vertical, that is, at 0 degrees with respect to the direction of gravity, but may be within 20 degrees as seen from the experimental results shown in Figure 2. Bye.

Further, the falling portions 12, 14 of the pipe 6a do not directly function as a heat insulating layer. Rather.

It is preferable to ensure that the upper and lower ends of the portions 12, 14 have the same temperature within a short period of time. Therefore, although the nine portions 12 and 14 are formed of a material having good thermal conductivity, a layer having good thermal conductivity may be provided on the inner surface. Also.

The portions 12.14 do not necessarily have to be provided at an angle of inclination of less than 20 degrees with respect to the direction of gravity. moreover.

The number of times of bending is also not limited to the number of times of the example.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a cryostat that can significantly reduce the amount of heat that enters through convection through piping despite having a simple structure.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of a cryostat according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the inclination of piping and the amount of heat penetration, and FIG. be. 1...Superconducting coil, 2...Liquid helium, 3...
- Refrigerant storage container, 4... Vacuum insulation layer, 5... Vacuum container. 6a... Piping, 12.14... Falling part. 13.15...Rising part. Applicant's representative Patent attorney Takehiko Suzue 1S1

Claims (2)

[Claims] (1) A refrigerant storage container that stores a cryogenic refrigerant; a vacuum container that covers the refrigerant storage container and forms a vacuum insulation layer between the refrigerant storage container; one end communicates with the refrigerant storage container, and the other end communicates with the refrigerant storage container; In the cryostat, the piping is provided with a piping whose side penetrates the vacuum insulation layer and the wall of the vacuum container and is located in the room temperature part, the piping has a plurality of parts that stand up at an inclination angle of 20 degrees or less with respect to the direction of gravity. A cryostat characterized in that it is provided in a meandering state. (2) The cryostat according to claim 1, wherein at least the inner surface of the falling portion of the pipe is formed of a material with good thermal conductivity.