JPS59189254A - Cryogenic thermal damper - 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 This invention relates to a thermal damper that is installed in an fZ helium gas cycle refrigeration system and dampens its temperature amplitude.

Generally, in a helium gas cycle refrigeration system, when cooling an object to be cooled such as a semiconductor laser element or a Josephson element sensor, fixing the element directly to the refrigerator will impair sensor performance due to the temperature amplitude of the low-temperature heat transfer device. Significantly impede or damage. In order to reduce this temperature amplitude, thermal dampers using ceramics with high volumetric specific heat or heat transfer buffers using copper strands are installed between the refrigerator and the object to be cooled, but they are expensive and have an effective temperature range. It has disadvantages such as narrow space and large heat transfer loss.

Fig. 1 is a schematic diagram (not showing the configuration) of a refrigeration system using a conventional gas cycle refrigeration machine; in the figure, 1 is a gas compressor;
is the motor, 3 is the gas switching valve, 4 is the first stage cylinder, 5 is the 2nd stage
Stage cylinder, 6 is 1st stage piston, 7 is 2nd stage piston, 8
1 stage seal, 9 2 stage seal, 10 1 stage cold storage material, 1
1 is a two-stage cold storage material, 12 is a first-stage heat transfer device, 13 is a second-stage heat transfer device, 14 is a first-stage refrigeration generation section, 15 is a second-stage refrigeration generation section,
16 is a copper strand, and 17 is an object to be cooled.

The circulating helium gas is pressurized by the compressor 1, and the high-pressure helium gas enters the switching valve 3, passes through the first stage cold storage material 10, part of it goes to the first stage refrigeration generator 14, and the rest passes through the second stage cold storage material 11. It enters the second stage freezing generation section 15.

At this time, the 1.2-stage piston 6.7 rises within the cylinder 4.5, and high-pressure helium gas fills each 1.2-stage refrigeration generating section. When the piston reaches the top end (C), the switching valve switches to compressor 1.
The high-pressure helium gas in each 1.2-stage refrigeration generating section expands to low pressure and generates refrigeration. After this valley 1.2
The stage piston descends, and the refrigerated gas passes through each of the 1.2 stage regenerator materials and takes the heat from the regenerator material, that is, stores cold heat and returns to the compressor as normal temperature gas, and the above cycle is repeated to generate extremely low temperatures. This generated extremely low temperature is transferred to the cooled body 17.
Heat is transferred to the strands using copper stranded wires 16 and the like.

In the conventional refrigeration system configured as described above, the heat transfer device of the refrigerator is generally made of copper, so the volumetric specific heat of copper, that is, the ability to store thermal energy, becomes extremely small below 20°C. Heat exchange occurs between the temperature at which high-pressure helium gas enters the generation part and the temperature that drops as it expands to low pressure and refrigeration occurs, and appears as a temperature amplitude on the external surface of the heat transfer device with extremely little resistance. If this temperature range is transmitted to a cryo-sensor, such as a semiconductor laser element or an element, it will adversely affect the sensor performance.
- In other words, ceramics, copper stranded wires, etc. are used as thermal dampers, but they have the disadvantage of being expensive because they require the selection of various types of ceramics according to the temperature range and complicated machining. In the case of wires made of gold, a large number of wires and several lengths are required, which has the disadvantage of increasing heat transfer loss and being uneconomical.

FIG. 2 shows physical property values of temperature and volume specific heat of 99.9% copper and helium gases in connection with the present invention. The vertical axis represents the volumetric specific heat (product of density and specific heat), and the horizontal axis represents the absolute temperature.
This figure shows a comparison of the physical properties of a commonly used heat control transfer device for a gas cycle refrigerator and a refrigerant helium gas that corresponds to the operating pressure of the refrigerator.

As is clear from the figure (the intersection of 20 atm high pressure helium gas and steel material is near 27, and the intersection of 5 atm low pressure helium gas and steel material is near 20).

In general, the influence of temperature amplitude occurs as follows in 15, so it can be seen that helium gas as a refrigerant is effective in terms of the volumetric specific heat value of the material.

The present invention encapsulates refrigerating machine circulating helium gas, which has a large volumetric specific heat at cryogenic temperatures, between the heat transfer device of a gas cycle refrigerating machine that uses helium gas as a refrigerant and the object to be cooled, thereby sufficiently storing refrigerating thermal energy. It is an object of the present invention to provide a cryogenic thermal damper which has a good heat transfer structure and can obtain a temperature vibration damping effect more efficiently, simply, and at a lower cost than conventional devices. The present invention will be described in detail below with reference to Examples.

FIG. 3 is a configuration diagram showing an embodiment of the present invention.

1.2.12.13.17 correspond to the corresponding parts of the conventional refrigeration system shown in FIG. 18 is a high-pressure pressure gauge, 19 is a low-pressure pressure gauge, 20 is a self-sealing joint, 21 is a filter, 22 is a pressure damping connecting pipe, 23 is an impure gas absorber, 24 is a capillary tube, 25
is a cryogenic thermal damper.

In the refrigeration system configured as described above, the operation of the refrigeration machine increases as the temperature drops from room temperature to a lower temperature, and the amount of gas processed by the refrigeration machine increases, and the pressure oscillation of the high pressure gauge 18 decreases to about 1. ATM is generated.

This pressure 4 movement is the same for the low pressure pressure gauge 19. Abrasion debris from switching valves, seals, pistons, cylinders, etc. of a gas cycle refrigerator is transported to the compressor together with low-pressure gas when the refrigerator is at low pressure. A filter 21 that filters out this dust or dust in the high-pressure gas supplied from the compressor, a self-sealing joint 20 for introducing gas from the high-pressure system or the low-pressure system,
A pressure damping connecting pipe 22 having an oriswiss or capillary tube (not shown) inserted therein to damp pressure vibrations, an absorber 23 for adsorbing impurity gas contained in helium gas,
A tube 26 and a capillary tube 24 connecting the heat transfer device 12 and the adsorber 23 are provided as shown. The capillary tube 24 surrounds the refrigerator cylinder 5 with appropriate contact and length to prevent heat intrusion. A cryogenic thermal damper 25 is provided between the refrigerator heat transfer device 13 and the object to be cooled 17, such as a sensor. Each component 20.21.22.23.24.25 is communicated.

The object to be cooled is cooled by using the metal case of the cryogenic thermal damper 25, for example, a copper material, and the thermal conductivity of this material is 300 to 5.
It is a good thermal conductor of about 400 w/m, k in the vicinity of . On the other hand, the helium gas contained inside has a density of 0.2 w/m, k at 300°C, and is known to be an extremely poor thermal conductor.

In order to effectively function these contradictory physical properties, the cryogenic thermal damper 25 according to the present invention has high fins 27.2 to increase the heat transfer surface area from the lower metal flange of the case.
8 is provided to increase the effect of convection heat exchange of helium gas.

Cooling 1/Soil This is done using copper materials, etc., which have extremely low heat transfer resistance, and the temperature amplitude is suppressed from 300 to 27K by mainly using steel, which absorbs thermal energy and performs a distributing action.
In the following, helium gas having a large volumetric specific heat mainly performs the damping action. High-pressure helium gas at 20 atm has an effective vibration damping effect below 27, and 5a
tm helium gas is particularly effective below 7.

In the above example, a preparation was used as the material for the Ise low-temperature thermal damper, and a fin-type heat exchanger structure was shown.However, as a thermal damper, a structure with extremely poor heat transfer, such as a box-type structure made of stainless steel, is most effective. . As a modification, the axial wall material of the thermal damper may be stainless steel, the heat transfer material may be aluminum, aluminum alloy, etc., and the heat exchanger type may be spiral type, ribbon type, multi-tube type, etc., and the material and structure may be selected as appropriate. I can do it.

As explained above, the gas cycle refrigeration system equipped with the cryogenic thermal damper 25 according to the present invention has the same operating means as the conventional gas cycle refrigeration system, and can effectively transfer heat from extremely low temperatures to the object to be cooled. However, it stores sufficient thermal energy using helium gas, has a better temperature damping effect than conventional devices, and is simple and economical.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the configuration of a refrigeration system using a conventional gas cycle refrigeration machine, Fig. 2 is a physical property value of temperature and volumetric specific heat of helium gas and copper, and Fig. 3 is an example of a thermal damper of the present invention. 1 is a schematic diagram of a refrigeration system having a In the figure, 1 is a compressor, 2 is a motor, 12 is a first-stage heat transfer device, 13 is a second-stage heat transfer device, 17 is an object to be cooled, 21 is a filter, 22 is a pressure vibration damping connecting pipe, and 23 is an impure gas 24 is a capillary tube, and 25 is a cryogenic thermal damper. Patent Applicant: Osaka Sanso Kogyo Co., Ltd. 7 Ni''-111-1 Opening 11759-189254 (4) t3 times 8

Claims (3)

[Claims] (1) In a gas cycle refrigeration system that uses helium gas as a refrigerant, a cryogenic thermal damper is placed between the refrigeration heat transfer device and the object to be cooled, and encapsulates a portion of the helium gas circulating in the refrigeration machine to suppress temperature amplitude. . (2) A patent claim that is connected to either the high pressure system or the 1 degree pressure system of a gas cycle refrigerator via a connecting pipe that introduces a portion of helium gas and limits pressure vibrations through a filter. Cryogenic thermal damper listed in item 1 of the range. (3) Claim 2, in which the connecting pipe is provided with an impure gas suction device and is connected to a refrigeration heat transfer device of a gas cycle refrigerator.
Cryogenic thermal damper as described in section.