JPS60155100A - Large-sized liquid helium storage tank - Google Patents

Abstract

PURPOSE:To efficiently use helium gas and reduce the evaporation loss by thermally joining the cooling section of an extremely low-temperature freezer with the outermost shield plate to cool this shield plate. CONSTITUTION:An inner tank storing liquid helium 1 is enveloped by shield plates 4a, 4b and is further enveloped by an outer tank 3, and the space between the inner tank 2 and outer tank 3 is kept vacuum. A pipe 5 passing the evaporated gas of liquid helium 1 through it is provided on the surface of individual shield plates 4a, 4b in series from the inner shield plate 4b to the outer shield plate 4a in sequence, and the evaporated gas cools the shield plates 4a, 4b then is recovered. The cooling section 11 of an extremely low-temperature freezer 10 is thermally joined with the outermost shield plate 4a to cool the shield plate 4a, thereby the radiation heat from the inner surface of the shield plate 4a is widely reduced, and the evaporation ratio is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to large liquid helium storage tanks for long-term storage.

Conventional technology In the field of cryogenic technology, which has been in the spotlight in recent years,
Although the amount of liquid helium used continues to increase, the amount of helium is limited, and users are looking for large storage tanks that have a low evaporation rate, are economical, and are easy to maintain.

Currently, storage tanks for cryogenic liquids such as liquid helium have an inner tank that stores the liquid, an outer tank that surrounds this at intervals and is in contact with the outside air, and a vacuum is created between the inner and outer tanks. At the same time, one or more stages of shield plates are provided between the inner and outer tanks, and the pipes through which the evaporated gas of the liquid in the storage tank passes are brought into contact with the outer shield plate sequentially from the inner shield plate in series or in parallel. The gas shield method for cooling has been widely adopted, and it is known that the evaporation rate of the culm liquid that increases the number of layers of the shield plate decreases. The number of layers of the plate is 1 to 2, and the evaporation rate remains at about 0.5 to 1.0%/day.

The liquid helium storage tanks used in the past have a capacity of about 5,000 e at most, and there was no problem with this level of evaporation rate, but in the future there will be a need for 10,000 e,
In large-scale liquid helium storage tanks for long-term storage of 000# class and above, it is impossible to reduce the evaporation rate by one order of magnitude from an economic point of view. To reduce the evaporation rate, increase the number of layers of the shield plate, but the more the number of layers of the shield plate increases,
It is difficult to manufacture, the cost is high, and the external dimensions of the storage tank are also large, so there is a limit due to economic efficiency.

This invention, in view of the above circumstances, has been developed to make efficient use of limited helium gas, and has a low evaporation rate that reduces evaporation loss even during long-term storage. Our objective is to provide a large-sized liquid helium and storage tank that is highly economical.

Structure: The large liquid helium storage tank of the present invention that achieves the above objects has the following features:
The cooling section of one or more cryogenic refrigerators is thermally coupled to the outermost shield plate of one or more layers of shield plates provided between the inner and outer tanks kept in a vacuum to cool the shield plate. It is characterized by being made to do.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

The accompanying drawing is a vertical sectional view schematically showing an embodiment of a large liquid helium storage tank according to an embodiment of the present invention.

The large liquid helium storage tank shown in the figure consists of an inner tank 2 that stores liquid 1, and an outer tank 3 that is bent at intervals and exposed to the outside air.
and a shield plate 4 (
4a, 41)). Each shield plate 4 a
, 41) A tube 5 through which vaporized gas of the stored liquid helium 1 passes is sequentially contacted in series from the innermost shield plate 4b to the outermost shield plate 4a to cool the shield plates and then collected. It is like that. This storage tank is supported on a foundation 7'' by a plurality of (four in the illustrated example) pillars 6 attached to the lower part of the outer tank 3. The inner tank 2 is supported by the outer tank by a multi-pipe support member 8. Multi-tube 3- The support member is made by arranging multiple tubes stacked concentrically to form a multi-tube in the form of one tube turned over several times to lengthen the heat conduction path12 and increase heat transfer. The resistance is increased to reduce heat conduction from the outer tank to the inner tank. Additionally, thermal anchors are used between the shield plates to suppress heat input into the inner tank. A liquid helium inlet/outlet 9 is provided at the top of the inner tank 2 and penetrates through the outer tank, and can be sealed by a sealing device (not shown). The configuration described so far is essentially the same as the configuration generally used in conventional small cryogenic liquid storage tanks such as liquid helium.

However, in the large liquid helium storage tank of this embodiment, as shown in the figure, the cooling part 11 of the small cryogenic refrigerator 10 is thermally coupled to the outer surface of the outermost shield plate 4a, and thereby the outermost shield plate 4a It is designed to cool down.

Now, since the space between the inner tank 2 and the outer tank 3 is kept in a vacuum, the heat is transferred from the outer tank 3 to the inner tank 2-L'). z are exclusively due to radiation. If the shield plates 4a and 4b are installed between the inner and outer tanks,
If there is no superincision on the outer surface of the inner tank 2, the amount of radiant heat from the inner surface of the outer tank directly enters the inner tank. In that case, if the outer surface of the inner tank is used as a reflective surface and super insulation is applied, the heat radiated from the inner surface of the outer tank 3 will be reflected and the heat input rate will be reduced. Therefore, by installing one or more layers of shield plates 4 between the inner and outer tanks and applying super insulation, the heat input rate of the radiant heat from the inner surface of the outer tank to the inner tank can be adjusted by multiplying the heat input rate of each shield plate. The product decreases. Since the radiant heat is proportional to the fourth power of the absolute temperature of the radiator, by lowering the temperature of the shield plate, the amount of radiant heat from its inner surface toward the inner tank 2 can be reduced. The gas shielding system in conventional liquid helium storage tanks is intended to achieve this purpose.

In the large liquid helium storage tank of the present invention, the cooling units 11 of a desired number of small cryogenic refrigerators 10 are thermally coupled to the outer surface of the outermost shield plate 4a, so that the outermost shield plate 4a is generally uniformly By making the temperature even lower than in the case of the gas shield method, the amount of radiant heat from the inner surface of the outermost shield can be significantly reduced compared to conventional methods, reducing the evaporation rate by, for example, 0.1 to 0.05%. /day.

Effects As a result, it is possible to significantly reduce the number of layers of super insulation that would be required to obtain the same effect without the present invention, and to reduce the external shape of the storage tank. It is a large liquid that is suitable for long-term storage and has excellent economical efficiency, such as being able to prevent the increase in size and cost, as well as the ability to liquefy recovered gas and reduce power consumption. You will get a Heliuno storage tank.

[Brief explanation of drawings]

The accompanying drawing is a vertical sectional view conceptually showing the structure of a large liquid helium storage tank according to an embodiment of the present invention. 1...Liquid helium 2...Inner tank 3...Outer tank 4a...Claw side shield plate 4b...
Innermost shield plate 5...Evaporative gas tube 6...Support member 7...Foundation 8...Multiple tube support member 10...Small cryogenic refrigerator 11...its cooling section

Claims (1)

[Claims] an inner tank for storing liquid helium; an outer tank that surrounds the liquid helium at intervals and is in contact with the outside air; and one or more stages of shield plates that are located between the inner tank and the outer tank and surround the entire inner tank. -4- The space between the inner tank and the outer tank is maintained in a vacuum,
A large liquid helium storage tank in which each shield plate is cooled by a tube through which vaporized gas of liquid helium stored in the inner tank is brought into contact with the outer shield plate in order from the inner shield plate. A cooling section of one or more cryogenic refrigerators is thermally coupled to the outermost shield plate of the one or more stages of shield plates as described in 1 above, so that the shield plate is cooled. Large liquid helium storage tank.