JPH0363484A - cryogenic container - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to devices that utilize superconducting magnets, such as M
The present invention relates to a cryogenic container applied to HI (nuclear magnetic resonance imaging apparatus) and the like.

[Prior Art] In MRI and the like, a cryogenic cryogen such as liquid helium is used to cool a superconducting magnet.

In order to fill these cryogens, a special cryogenic container as shown in FIG. 5 is generally used. This product consists of an inner container 1 filled with cryogenic cryogen a, an outer container 2 that encloses the inner container 1 under vacuum insulation, and a heat exchanger interposed between the inner container 1 and the outer container 2. shield plate 3,
The inner container 1 is provided with a pipe 4 that penetrates the heat shield plate 3 and the outer container 2 and connects the internal space of the inner container 1 to the outside. The inner container 1, outer container 2, and piping 4 are made of a material with low thermal conductivity, and conversely, the heat shield plate 3 is made of a material with high thermal conductivity. The inner container 1 and the heat shield plate 3 are held in the outer container 2 by a heat insulating support rod 5.

Piping 4 is necessary for drawing lead wires for energization and excitation into the superconducting magnet that is destroyed by cryogenic cryogen a,
It also serves as a pressure release passageway to prevent the inner container 1 from being damaged by evaporated gas that grows in the internal space of the inner container 1 when the superconductor is broken (this is called quenching). 6 is a destructive safety valve.

However, when such a pipe 4 is provided, heat intrusion is likely to occur due to conduction in the pipe wall 4a and convection inside the pipe wall 4a, and as a result, the temperature of the inner container 1 increases and the refrigerant a
This causes the inconvenience of increasing the amount of evaporation.

Therefore, in the past, a thermal anchor (copper wire, etc.) 7 as shown in Fig. 6 is buried in a part of the pipe wall 4a, and this is cooled to a constant temperature and used as a fixed temperature point to prevent conduction and convection. I am trying my best to do so. In this case, a heat shield plate 3 is used for cooling, and the thermal anchor 7 is connected to this heat shield plate 3.
It is customary to be connected in a thermally conductive manner to the Also,
A cooling vibe 8 connected to a refrigerator (not shown) is attached to the heat shield plate 3 in order to reduce heat radiation from the outer container 2 to the inner container 1. It is cooled to a constant temperature by a refrigerator or by a refrigerator (not shown).

In addition, the piping 4 may extend approximately horizontally due to the advantages and disadvantages of space, and in this case, a convection prevention mechanism 9 as shown in the figure is generally provided to prevent active heat intrusion due to convection. It is. This convection prevention mechanism 9 includes a plurality of partition plates 9a arranged intermittently along the tube axis.
It is designed to prevent convection from occurring beyond the point 9a, and during quenching, the partition plate 9a is crushed or deformed to release pressure.

Also, because this would create resistance during quenching,
Some devices are provided with a straw-shaped convection prevention mechanism 10 as shown in FIG. In this device, a self-weight type sealing valve 10b is attached to the high temperature end of the flow path 10a, allowing convection only within each flow path 10a, and when quenching, the valve 10b opens to release pressure. There is.

In any case, taking appropriate measures to prevent heat intrusion through the pipe 4 can be said to be an extremely important factor in stabilizing the extremely low temperature state of the inner container 1 and ensuring proper operation of the superconducting magnet.

[Problems to be Solved by the Invention] However, in all of these conventional systems, when the temperature distribution inside the pipe 4 is actually extremely low, the temperature distribution in the center as shown in FIG. The higher the temperature, the lower the temperature, and the higher the flow rate of evaporated gas, the higher the temperature shift in the opposite direction to the diagram, the temperature gradient is uneven and steep, and it cannot be a sufficient measure to prevent convection. .

One of the reasons for this is thought to be that although the thermal anchor 7 can create a fixed temperature point on the tube wall 4a, it cannot exert an effect on the internal space.

The present invention has been made based on this point of view, and an object of the present invention is to further reduce heat intrusion into piping by providing a more effective temperature fixed point.

[Means for Solving the Problems] The present invention takes the following measures in order to distantly achieve the above object.

That is, the cryogenic container of the present invention comprises an inner container filled with a cryogenic cryogen, an outer container enclosing the inner container under vacuum insulation, and a heat exchanger interposed between the inner container and the outer container. A device comprising a heat shield plate and a pipe that passes through the heat shield plate and the outer container to communicate the internal space of the inner container to the outside, wherein the heat shield plate has a large number of gas passage holes in the pipe. It is characterized in that an exchange plate is provided, and this heat exchange plate is connected to a heat shield plate outside the piping in a heat conductive manner.

[Function] By doing this, the heat exchange plate is cooled by the heat shield plate, so that the cross section inside the pipe in this area is kept at a uniform and constant temperature, and the temperature gradient with the inner container is also effectively reduced. be done. As a result, it becomes possible to create an environment in which convection is more difficult to occur than in the past. Moreover, since the heat exchange plate has gas passage holes, there is no flow path resistance during quenching.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2. Note that parts common to those in FIG. 5 are given the same reference numerals.

The cryogenic container of this embodiment has the basic configuration shown in FIG. 5, in which a plurality of partition plates 9a are intermittently attached to the core material 11 with low thermal conductivity along the tube axis direction, and these are connected to the piping. It is inserted within 4. These partition plates 9a are made of a flexible polymer sheet or the like, and have several cuts in the radial direction. The gas is allowed to flow through the small gap created by this cut, and at the time of quenching, the partition plate deforms into a conical shape, allowing the gas to pass through smoothly.

1 and 2 between these partition plates 9a.
A heat exchange plate 13 as shown in the figure is attached. This heat exchange plate 13 has a copper mesh 13b with good thermal conductivity attached to the opening of a thin ring-shaped frame 13a. It is connected to conductive finger 13c. At the insertion position, these fingers 13c are attached to the thermal anchor 7 embedded in the tube wall 4C. The thermal anchor 7 is connected to the heat shield plate 3 with a conventional copper wire or the like so as to be thermally conductive.

According to such a structure, as the heat exchange plate 13 is cooled by the heat shield plate 3, the entire copper net 13b is cooled, and this portion is kept at a constant temperature evenly. Therefore, there is almost no temperature difference between the upper space and the lower space within the pipe 4.

Moreover, by creating a flat temperature fixed point in this way, the temperature gradient between the inner container 1 and the inner container 1 is surely reduced, and as a result, the possibility of convection is effectively reduced compared to the conventional method. I can do it. Moreover, since gas passage holes are formed between the joints formed by the copper mesh 13b, the jet flow during quenching passes through smoothly, and no flow path resistance impairs the original function of the piping 4. Therefore, it becomes possible to put it to practical use as a device that exhibits a superior convection prevention effect compared to the conventional one.

Moreover, this structure can also be used in reverse to eliminate the need for the cooling pipe 8. That is, the above explanation was for applying cold heat from the heat shield plate 3 to the heat exchange plate 13, but if the evaporated gas is made to flow outward little by little through the pipe 4 in the illustrated configuration, the evaporated gas is The copper net 13b takes away cold heat and supplies it to the heat shield plate 3. Therefore, there is no need to provide the cooling pipe 8.

The cooling pipe 8 has traditionally been a heat transfer factor along with the piping 4, and the production and inspection of airtight welded parts was labor-intensive and led to high costs, so being able to eliminate it would bring great benefits. Don't wait to say it.

Although one embodiment of the present invention has been described above, the configuration of each part is not limited to the illustrated example. For example, if the heat shield plate is 2
When the heat exchange plates 13a are installed in double or triple layers, the number of fixed temperature points can be increased by sequentially connecting the heat exchange plates 13a to the heat shield plates on the low temperature side as shown in FIGS. 3 and 4. Conversely, it is of course possible to provide cold heat to each heat shield plate from each heat exchange plate 13a. Further, the heat exchange plate is not limited to copper mesh, and may be a porous relatively thick plate. Furthermore, even if the pipes are arranged vertically or inclined, similar effects can be achieved by applying the present invention.

[Effects of the Invention] Since the present invention has the above configuration, it is possible to exchange heat between the evaporated gas and the heat shield plate via the heat exchange plate, and when applying cold heat to the evaporated gas from the heat shield plate. This makes it possible to securely maintain a fixed temperature point and suppress convection, and conversely, it becomes possible to eliminate the need for cooling pipes when applying cold heat from evaporated gas to the heat shield plate.

[Brief explanation of drawings]

FIGS. 1 and 2 show an embodiment of the present invention, with FIG. 1 being a longitudinal cross-sectional view of piping, and FIG. 2 being a perspective view showing a heat exchange plate. FIGS. 3 and 4 are diagrams schematically showing piping according to other embodiments of the present invention. Figures 5 to 8 show conventional examples, Figure 5 is a schematic overall view of the cryogenic container, Figures 6 and 7 are diagrams schematically showing piping, and Figure 8 is an explanatory diagram of the operation. It is.

Claims (1)

[Claims] An inner container filled with cryogenic cryogen, an outer container enclosing this inner container under vacuum insulation, a heat shield plate interposed between the inner container and the outer container, this heat shield plate and the above-mentioned A heat exchange plate having a large number of gas passage holes is disposed in the pipe, and the heat exchange A cryogenic container characterized by a plate connected to a heat shield plate outside the piping for heat conduction.