JPH0228314Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a cryogenic pipe joint, and particularly to a cryogenic pipe joint suitable for transferring a cryogenic fluid such as liquid helium.

[Background of the idea]

In cryogenic equipment such as helium transfer tubes,
It becomes necessary to connect pipes to equipment or pipes to pipes.
An example of a conventionally used pipe joint structure is shown in FIG. In FIG. 1, 1 is an outer tube, 2 is a sleeve fixed to the outer tube 1, and an O-ring 5 is attached to the outer periphery. A metal fitting 3 is fixed to the tip of the outer tube 1, and a packing 4 is attached to the metal fitting 3. 6 is an insertion tube, 7 is a metal fitting fixed to the insertion tube 6, and 9 is a receiver similarly fixed to the insertion tube 6. 8 is a nut for fixing the entire helium transfer tube to the insertion tube 6; 10 is an inner tube whose tip is fixed to the metal fitting 3; 11 is a mounting plate to which the insertion tube 6 is fixed. In this case, although not shown, the mounting plate 11 represents a part of the vacuum insulated container.

In the above configuration, the role of each part will be explained.
A cryogenic fluid such as liquid helium flows inside the inner tube 10 . A gap 12 between the outer tube 1 and the inner tube 10 is in a high vacuum atmosphere for insulation purposes. By engaging the threads of the metal fitting 7 and the nut 8, the sleeve 2, that is, the entire helium transfer tube including the outer tube 1, is pushed into the insertion tube 6, and as a result, the gasket 4 is pressed against the tapered portion of the receiver 9. It will be done. Therefore, the cryogenic fluid in the inner tube 10 is prevented from entering the gap 13 between the outer tube 1 and the insertion tube 6, which is effective in preventing heat loss. O-ring 5
This is effective against adverse effects such as heat loss and freezing caused by air entering the gap 13. The atmosphere in the gap 13 is generally created by loosening the nut 8 when assembling the transfer pipe, slightly lifting the packing 4, and replacing the atmosphere with the same fluid as in the inner pipe 10.

However, this structure had the following drawbacks. The tip of the outer tube 1 is at an extremely low temperature, and the portion where it is fixed to the sleeve 2 is at room temperature. Furthermore, the insertion tube 6 also has a similar temperature gradient. Therefore, outer tube 1
The insertion tube 6 suffers heat loss due to thermal conduction from room temperature.

Let's try calculating the heat loss mentioned above under the following assumptions. The outer tube 1 has an outer diameter of 14 mm and a wall thickness of 0.5 mm, the insertion tube 6 has an outer diameter of 20 mm and a wall thickness of 0.5 mm, and both the outer tube 1 and the insertion tube 6 have a length of 300 mm and are made of stainless steel. The heat loss due to thermal conduction is calculated from the following equation (1).

Q=a/l∫ ^t2 _t1 λdt ...(1) Here, Q: Heat loss due to thermal conduction [W] l: Length of the member [cm] a: Cross-sectional area of the member [cm ² ] λ: Heat of the member Conductivity [W/cm・K] t ₁ : Cooling end temperature of the member [K] t ₂ : High temperature end temperature of the member [K] If t ₁ is 4.2K and t ₂ is 300K, the heat loss is from the outer tube. 1
Approximately 0.22W for insertion tube 6, approximately 0.31W for insertion tube 6, total approximately
This is 0.53W, and the insertion tube 6 accounts for 58% of the total approximately 0.53W. 0.31W at a temperature around 4.2K
To achieve that cold temperature, you would need at least 1500 times more energy, or 465W or more.

One cryogenic device requires a large number of transfer pipe joints as described above, and the heat loss is expected to be considerable.

As described above, with the conventional structure, that is, with the insertion length of the joint portion being shortened to 300 mm in this case, there was a problem that heat loss due to heat conduction of the insertion tube 6 could not be reduced. Note that in order to reduce heat loss due to heat conduction in the transfer pipe joint, the length of the joint portion may be made considerably long, but it cannot be made very long due to structural or other reasons.

[Purpose of invention]

An object of the present invention is to provide a cryogenic pipe joint that can reduce heat loss due to heat intrusion from the outside, even when the joint length is short.

[Summary of the idea]

This invention is a bayonet-type cryogenic pipe joint that connects a cryogenic vacuum insulated transfer pipe and a vacuum insulated container, in which a male joint of the cryogenic vacuum insulated transfer pipe protrudes from inside the vacuum insulated container into which it is inserted. By providing a flow path in the middle part of the internal part of the insertion tube provided in this manner, through which a low-temperature medium having a temperature higher than the cryogenic fluid transferred by the cryogenic vacuum insulation transfer tube flows.
Even in a cryogenic pipe joint with a short joint length, it is possible to prevent heat from entering from the outside in the middle part, thereby reducing heat loss of the cryogenic fluid.

[Example of idea]

An embodiment of the present invention will be explained with reference to FIG. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same parts, and their explanation will be omitted.

14 is a jacket provided on the insertion tube 6, 15 is a refrigerant inlet, and 16 is a refrigerant outlet.

In the above configuration, the refrigerant flowing through the middle of the insertion tube 6 into the jacket 14 maintains the temperature sufficiently lower than when no refrigerant flows. In this way, the heat loss due to thermal conduction of the insertion tube 6 is determined using the same calculation method as described above. In this case, the cooling point of the insertion tube 6 by the jacket 14 is set midway between the room temperature end and the cryogenic end, that is, 150 mm from room temperature, the refrigerant is liquid nitrogen, and the other conditions are the same as in the above case.
According to the calculation, the conductive heat loss of the insertion tube 6 is 0.065W
becomes. When the refrigerant in the jacket 14 was not used, it was 0.31W, so according to this example, it was about 1/2
can reduce heat loss.

As described above, according to this embodiment, the middle part of the insertion tube 6 is cooled with the transfer fluid, in this case liquid nitrogen, which has a higher temperature than liquid helium, so that the temperature that enters the insertion tube 6 from the normal temperature part is lowered. It is possible to prevent high heat from entering in the middle part, and even in cryogenic pipe joints with short joint lengths, it is possible to reduce heat loss due to heat entering from the outside.

[Effect of idea]

According to the present invention, even a cryogenic pipe joint with a short joint length has the effect of reducing heat loss due to heat intrusion from the outside.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional pipe joint, and FIG. 2 is a longitudinal sectional view of an embodiment of a pipe joint according to the present invention. 1... Outer tube, 6... Insertion tube, 10... Inner tube, 1
4...Jacket.

Claims (1)

[Scope of utility model registration request] In a bayonet type cryogenic pipe joint that connects a cryogenic vacuum insulated transfer pipe and a vacuum insulated container,
The cryogen to be transferred by the cryogenic vacuum insulated transfer tube is placed in the middle of the internal portion of the insertion tube, which is provided so as to protrude from the inside of the vacuum insulated container to the outside into which the male joint of the cryogenic vacuum insulated transfer tube is inserted. A cryogenic pipe joint characterized by having a flow path through which a low-temperature medium having a higher temperature than a low-temperature fluid flows.