JPH0366997A - Multi-layer heat insulating material - 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 relates to a multi-layer insulation material used in a cryogenic device such as a superconducting magnet.

[Prior Art] FIGS. 4 and 5 are longitudinal cross-sectional views showing the structure of a conventional cryogenic device disclosed in Japanese Patent Application Laid-open No. 194171/1984, and the multilayer insulation material used therein. FIG.

In the figure, code (1) is the superconducting coil, (2) is the liquid helium in which the superconducting coil (1) is immersed and cooled.
(3) is a cryogenic fluid tank containing liquid helium (2), (4) is liquid nitrogen that cools the cryogenic fluid tank (3) from the outside, and (5) is a radiant tank that blocks radiant heat from the outside. The shield, (6) is a multilayer heat insulating material provided outside the radiation shield (5), and (7) is a vacuum container wall that houses the above-mentioned parts and maintains the vacuum. In addition, (8) is a substrate of a low radiation insulation material (6a) that constitutes a multilayer insulation material (6) together with a low thermal conduction insulation material, and (9) is a substrate of a low radiation insulation material (6a) that is configured with a low radiation insulation material (6a) on the surface of the substrate (8). a reflective film made of metal deposited on the
(10) is a slit arranged in one direction between adjacent reflective films (9>) to insulate the reflective films (9>).

This cryogenic device is constructed as described above, and includes a superconducting coil (1) immersed in liquid helium (2), etc., which is wrapped and evacuated to form a vacuum insulated vacuum chamber, and a vacuum vessel wall ( 7) and the cryogenic fluid tank (3), the radiation shield (5) cooled with liquid nitrogen (4) etc. and the multilayer insulation material (6) are used to connect the vacuum tank to the cryogenic fluid tank. (3) Reduces the amount of radiant heat entering.

[Problem to be solved by the invention] This multilayer heat insulating material has a substrate such as a plastic film (8
) is coated with a reflective film (9) made of a metal with high thermal conductivity and low emissivity such as aluminum, copper, or silver by vapor deposition or other means.
The structure consists of alternating layers of low-radiation heat insulators with low thermal conductivity such as plastic nets, etc.
When a fluctuating magnetic field is applied from the outside, such as in an IH setting,
Eddy currents flow on the surface of the deposited reflection H(9>).

In order to reduce the eddy current loss by converting this eddy current into a flow, the reflection 11g (9) is connected to the slits (10) at appropriate intervals.
has been established.

However, as in the stator windings of superconducting transformers and superconducting generators, which have recently been developed,
In equipment operated at 60 Hz, if the slits (10) are only in one direction or if the spacing between the slits (10) is an appropriate size as in the past, the value of eddy current loss may become too large. Alternatively, there is a problem in that it is difficult to predict the value of eddy current loss, making the design of the cryogenic device inaccurate, and conventional devices have had the problem of solving such problems.

This invention was made to solve the above problems, and aims to obtain a multilayer insulation material that can accurately grasp the value of eddy current loss occurring in the reflective film and reduce the value sufficiently. purpose.

[Means for Solving the Problems] The multilayer insulation material according to the present invention is provided with slits for electrical insulation so that the area of the reflective film, which is a vapor-deposited metal of the low radiation insulation material, is 100CI112 or less, and The reflecting plates of vertically adjacent low-radiation heat insulating materials, that is, the vapor-deposited metals, are arranged so as to be offset from each other.

[Function] Since the multilayer insulation material according to the present invention is configured as described above, the area of the vapor-deposited metal of the low radiation insulation material is 100 cm.
2 or less, the eddy current value can be reduced, and since the above-mentioned adjacent vapor-deposited metals are staggered from each other, the value can be accurately grasped. be able to.

[Example] This invention will be explained below based on the drawing showing one example of the invention.6 In the drawing, reference numeral (12) indicates a metal having high thermal conductivity and low emissivity on a substrate (8) made of a plastic film or the like. + (13
) is a vertical slit, (14) is a horizontal slit,
The reflections 111 (12) partitioned by these slits (13) (14) are electrically insulated from each other.

(a) is the vertical length of one reflective film (12), (b) is the length of the same as the reflection, Figure 2 is the electrical resistivity of aluminum, and Figure 3 is the electric resistivity of the multilayer insulation material. FIG. 3 is a diagram showing eddy current loss density.

An example of the structure of the low-radiation heat insulating material (11) in a multilayer heat insulating material is, as shown in FIG. was deposited on both sides to a thickness of about 0.1 pm, but this reflection!
A vertical slit (13), a horizontal slit (
14) and is electrically insulated from the adjacent reflective section fi (12).

Here, the area of the section of reflection l1l (12) (vertical length aX
The horizontal length b> is 100c1 or less.

The reason for this is the area of the aluminum vapor deposition section and the AC60
The relationship with eddy current loss in Hz will be described next.

When a magnetic field of Bo·(jωt) is applied perpendicularly to an aluminum block with a stroke length of L (+i) and a thickness of t(-), the eddy current loss per unit area P (W/ +
n'') is expressed by the following formula.

■ P= Bo2ω2tL2 (W/m2)64
ρ where is the electrical resistivity of aluminum and is the angular frequency.

The relationship between the electrical resistivity of aluminum and temperature is shown in FIG.

FIG. 3 shows the relationship between the length of one side of an aluminum block and the eddy current density, using temperature as a parameter. Here, the thickness t of aluminum was 0.1) tm, the applied magnetic field BO was 1, and the number of laminated layers was 30.

On the other hand, the amount of heat that enters a multilayer insulation material due to thermal radiation is 1 (W/+w2) for about 30 layers (according to actual measurements), and it is necessary to suppress the amount of eddy current loss to about 115.

That is, the eddy current loss density in Fig. 3 is P = 0.2 (W/
I2) Therefore, the length of one side of the aluminum block must be less than 1 m (shaded area). Therefore, the area of the aluminum block is required to be 100 cm2. Therefore, the area of 1 section of reflection III (12) is 100C
I112 or less.

In addition, when multiple layers of low radiation insulation materials (11) are stacked as a multilayer insulation material, vertically opposing low radiation insulation materials (11)
The sections in which metal is vapor-deposited, that is, the sectioned reflections M (12) are constructed so that the adjacent upper and lower sections are shifted from each other.

[Effects of the Invention] As explained above, according to the present invention, the vapor-deposited metal of the low-radiation heat insulating material is divided into sections with an area of 100 cm2 or less that is electrically insulated from the vapor-deposited metal in the adjacent section. In addition, when laminated, the layers are stacked so that the sections are offset from each other with respect to the vapor-deposited metal of the adjacent low radiation insulation material above and below, so the accurate value of eddy current loss can be determined. It has the effect of making it possible to grasp the amount of liquid helium or liquid nitrogen consumed, and to obtain a multilayer insulation material with low eddy current loss. This means that a small amount of equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a plan view of a low radiation insulating material constituting the multilayer insulating material of the present invention together with a low thermal conductivity insulating material, and is a plan view showing the surface of a reflective film made of vapor-deposited metal. The resistivity diagram, Figure 3 is the eddy current loss density diagram for the width of the aluminum block, which is a multilayer insulation material, Figure 4 is the vertical cross-sectional view of the cryogenic equipment, and Figure 5 is used in Figure 4. FIG. 2 is a cross-sectional view of a low-radiation heat insulating material constituting a conventional multilayer heat insulating material. (6)...Multilayer insulation material, (8)...Substrate, (9) (12)
)・Vapour-deposited metal (reflective film), (11)・Low radiation insulation material,
(13)...Vertical slit, (14)...Horizontal slit. In each figure, the same reference numerals indicate the same or corresponding parts. 11: 1esn'lfmVsU 122 leather, l gold L (reflection - Enoki) 13° exposed slit 14: fw pickpocket, to agent, person, large rock, male -+
AI (RRR-100) #) ffi EFT'S
P (Ωm)14 'LIL1i! '%:1f7t
P ("/m") 嘂 4 fig. E 5 fig. board

Claims (1)

[Claims] The above-mentioned multilayer insulation material is made up of alternating layers of a low-radiation insulation material with a low emissivity made by vapor-depositing metal on the surface of a substrate such as a plastic film, and a low-thermal conduction insulation material with a low thermal conductivity such as a plastic net. The vapor-deposited metal of the low-radiation heat insulating material is divided into sections such that the area of one vapor-deposited section is 100 cm^2 or less, and is electrically insulated from the vapor-deposited metal in the adjacent section. A multilayer insulation material characterized in that the vapor-deposited metals of the above and below are arranged offset from the vapor-deposited metals of the low-radiation insulation material that are vertically adjacent to each other.