CN2733299Y - High vacuum cryostat by employing low heat-leakage flexible connection structure - Google Patents

Abstract

The utility model discloses a high-vacuum low-temperature thermostat adopting a flexible connection structure with low heat leakage. It has a refrigerator fixing flange, the outer side of the refrigerator fixing flange and the outer wall of the upper end of the thermostat are fixed by a bolt structure, the inner side of the refrigerator fixing flange and the outer wall of the upper end of the thermostat are fixed by bellows welding, inside the thermostat, the refrigerator is fixed A vacuum jacket, an upper heat sink, a flexible thermal connection structure, and a lower heat sink are arranged sequentially under the flange. The utility model has the advantages: the vacuum jacket adopts the type of thin-walled stainless steel pipe, bellows or folded sleeve, which has the characteristics of low heat leakage; the stainless steel bellows in the fixed structure can eliminate the mechanical vibration caused by the operation of the low-temperature refrigerator ; The flexible connection structure allows a certain mechanical deflection between the cold head of the refrigerator and the object to be cooled; the additional indium sheet between the cold head and the heat sink and the heat sink and the object to be cooled can reduce the contact thermal resistance between the connecting parts in an attempt to reduce Loss of effective cooling capacity.

Description

High vacuum cryostat with low heat leakage flexible connection structure

technical field

The utility model relates to a high-vacuum low-temperature thermostat adopting a flexible connection structure with low heat leakage.

Background technique

Many applications (such as the cooling of the vacuum environment simulation chamber) need to provide a low-temperature environment. In the past, the low-temperature liquid was used to flow through the coil coiled on the object to be cooled to achieve cooling purposes. The operation is complex, and additional liquefaction equipment or cryogenic storage tanks are required to provide a large amount of cryogenic liquid. The treatment of the evaporated gas after heat exchange is also a difficult problem. For example, the high price and safety issues of cryogenic gas require the installation of gas recovery device, which in turn will greatly increase the complexity of the system. In this context, refrigerant-free solutions using direct cooling with cryogenic refrigerators have become more and more widely used. Compared with the traditional solution using refrigerant for cooling, the non-refrigerant solution also brings a new problem, that is, how to efficiently transfer the cold energy of the cryogenic refrigerator to the object to be cooled, which not only has to overcome the rigid connection that causes The problem of mechanical stress, and in terms of structural installation, the object to be cooled is required to allow a certain degree of freedom of movement. In addition, there is a need to overcome the problem of mechanical vibration caused by the operation of the refrigerator. These issues require a flexible connection solution with low heat leakage.

Contents of the invention

The purpose of the utility model is to provide a high-vacuum low-temperature thermostat adopting a flexible connection structure with low heat leakage.

It has a refrigerator fixing flange, the outer side of the refrigerator fixing flange and the outer wall of the upper end of the thermostat are fixed by bolt structure, the inner side of the refrigerator fixing flange and the outer wall of the upper end of the thermostat are fixed by bellows welding, inside the thermostat, the refrigerator is fixed A vacuum jacket, an upper heat sink, a flexible thermal connection structure, and a lower heat sink are arranged in sequence under the flange.

The utility model has the advantages: the vacuum jacket adopts the type of thin-walled stainless steel pipe, bellows or folded sleeve, which increases the heat conduction resistance and reduces the axial heat leakage, and has the characteristics of low heat leakage; the vacuum jacket and the outer wall of the upper end of the thermostat The stainless steel bellows are used in the fixed structure, which can eliminate the mechanical vibration caused by the operation of the cryogenic refrigerator; the thermal connection between the cold head of the cryogenic refrigerator and the object to be cooled adopts a flexible connection structure, allowing the cold head of the cryogenic refrigerator to be connected to the cooled object There is a certain degree of freedom between the cooling objects to achieve mechanical deflection; the connection between the flexible oxygen-free copper braid and the heat sink in the flexible connection structure adopts silver welding to reduce contact thermal resistance, and at the same time, the welding holes are connected with each other And there is a common air outlet channel, which can prevent the gas sealed in the welding hole from being gradually released to the vacuum environment and affect the vacuum degree; the additional indium sheet between the cold head and the heat sink and the heat sink and the object to be cooled can reduce the connection. The contact thermal resistance between them is used to reduce the loss of effective cooling capacity.

Description of drawings

Fig. 1(a) is a structural schematic diagram of a high vacuum cryostat using a low heat leakage flexible connection structure;

Fig. 1 (b) is the b-b view of the upper heat sink of the utility model;

Fig. 1 (c) is the c-c view of the lower heat sink of the utility model;

Fig. 2 is a schematic diagram of the connection structure of a stainless steel bellows used in the vacuum jacket of the present invention;

Fig. 3 is a schematic diagram of the connection structure of the vacuum jacket of the present invention using a stainless steel folded sleeve.

Detailed ways

In order to achieve the purpose of low heat leakage, the utility model adopts three schemes in the aspect of the vacuum jacket, that is, a thin-walled stainless steel tube, a corrugated tube and a folded sleeve. The thin-walled tube solution (Fig. 1-3a) is to increase the heat conduction resistance through the thin-walled tube, while the common point of the corrugated tube (Fig. 2-3b) and the folded sleeve (Fig. 3-3c) is to increase the heat conduction path to achieve The purpose of reducing axial heat leakage. The latter two solutions are more suitable for occasions where the cooling temperature is relatively low, because at this time, reducing heat leakage and effectively utilizing the cooling capacity of the refrigerator are the key problems to be solved in the system. At the same time, since the contact thermal resistance between the cold head and the heat sink and between the heat sink and the object to be cooled will lead to an increase in the temperature difference between the connecting parts and a loss of effective cooling capacity, the use of additional soft metal indium sheets can reduce the thermal resistance.

The thermal connection between the cold head of the cryogenic refrigerator and the object to be cooled is not a direct hard connection, but a flexible connection structure, that is, the cold head of the refrigerator transfers the cold energy to the upper heat sink through the indium sheet, and then, through the high thermal conductivity The high-efficiency flexible oxygen-free copper braid transfers the cold energy to the lower heat sink, and finally connects to the object to be cooled through the bolt structure with additional indium sheets. This flexible connection structure allows a certain degree of freedom between the cold head of the refrigerator and the object to be cooled to achieve mechanical deflection.

The connection between the flexible oxygen-free copper braid and the heat sink in the flexible connection structure adopts silver soldering to reduce contact thermal resistance. In order to prevent the gas sealed in the welding holes from being gradually released to the vacuum environment, each welding hole is connected with each other and passes through a common outlet channel to release the gas in the holes.

The low-heat-leakage flexible connection scheme between the low-temperature refrigerator and the object to be cooled generally consists of a low-temperature refrigerator 1, a refrigerator fixed casing structure 2, a vacuum jacket 3, an upper heat sink 4, a lower heat sink 6, and a flexible thermal connection structure 5 It is composed of parts such as cooled object 7 and the like.

First of all, the cryogenic refrigerator 1 needs to be installed in the whole system. Since the object to be cooled 7 is usually placed in a vacuum environment 13 inside the thermostat, in order to facilitate the installation and disassembly of the refrigerator, the cryogenic refrigerator part 1 adopts a In the independent vacuum space 14 formed by the vacuum jacket 3, the vacuum jacket 3 is first fixed to the outer wall 15 of the vacuum environment 13 thermostat equipped with the object to be cooled, and then the cryogenic refrigerator 1 is fixed in the vacuum jacket 3, through The O-ring 18 achieves a vacuum seal within the jacket.

In order to eliminate the impact of the vibration brought by the operation of the refrigerator on the system, the connection between the vacuum jacket 3 and the outer wall 15 of the thermostat is fixed by a bellows 16-bolt structure 17. The sleeve pipe of the vacuum jacket 3 can adopt three forms: a thin-walled stainless steel straight pipe 3a, a stainless steel corrugated pipe 3b, and a stainless steel folded pipe 3c. The latter two are to reduce heat conduction loss by increasing the thermal resistance of the heat conduction path. The latter two schemes are structurally more suitable for occasions where the refrigeration temperature is relatively low, because the heat leakage problem at this time is a problem that needs to be overcome in the system. In addition, in order to prevent structural stability problems caused by insufficient rigidity when the corrugated tube 3b is used, the wall thickness of the stainless steel bellows 3b itself should not be smaller than that of the thin-walled stainless steel straight tube 3a.

The cooling of the cooled object 7 by the cold head 9 of the refrigerator is realized through the upper heat sink 4 and the lower heat sink 6, and a soft metal indium sheet 8 is added between them to reduce contact thermal resistance and heat transfer temperature difference. Considering the thermal expansion and contraction of the connection system and the improvement of the connection flexibility (including shape and position, etc.) with the object to be cooled 7, the low-temperature refrigerator 1-upper heat sink 4, lower heat sink 6-to-be-cooled object 7 adopts flexible The connection structure 5 is connected by 9 flexible oxygen-free copper braided strips 10 (8 of which are evenly distributed along the circumference and 1 in the center). The distribution is shown in Figure 1(b) and Figure 1(c). Silver soldering is used between the flexible oxygen-free copper braid 10 and the upper heat sink 4 and the lower heat sink 6 . In order to prevent the gas sealed in the welding holes from gradually releasing to the vacuum environment and affecting the surrounding vacuum environment, each welding hole is communicated with each other and passes through a common outlet channel 12 to release the gas in the holes. The connection between the heat sink 6 and the cooled object 7 is fixed by bolts, and a soft metal indium sheet 11 is sandwiched between the two.

Claims (7)

1. A high vacuum cryostat adopting a low heat leakage flexible connection structure is characterized in that it has a refrigerator fixing flange (2), and the outer wall (15) of the refrigerator fixing flange (2) and the upper end of the refrigerator adopts The bolt structure (17) is fixed, the inner side of the refrigerator fixing flange (2) and the outer wall (15) of the upper end of the thermostat are welded and fixed by bellows (16), inside the thermostat, the refrigerator fixing flange (2) is sequentially provided with A vacuum jacket (3), an upper heat sink (4), a flexible thermal connection structure (5), and a lower heat sink (6). 2. A high vacuum cryostat using a low heat leakage flexible connection structure according to claim 1, characterized in that said vacuum jacket (3) is made of stainless steel bellows (3b). 3. A high-vacuum cryostat adopting a low-heat-leakage flexible connection structure according to claim 1, characterized in that said vacuum jacket (3) adopts a stainless steel folded tube (3c). 4. A high-vacuum cryostat using a low-heat-leakage flexible connection structure according to claim 1, characterized in that said flexible thermal connection structure (5) uses a flexible oxygen-free copper braid (10). 5. A high vacuum cryostat using a low heat leakage flexible connection structure according to claim 1, characterized in that said upper heat sink (4) and lower heat sink (6) are provided with an air outlet channel (12) . 6. A high vacuum cryostat adopting a low heat leakage flexible connection structure according to claim 1, characterized in that a soft metal indium sheet (8) is provided inside the upper heat sink (4). 7. A high vacuum cryostat adopting a low heat leakage flexible connection structure according to claim 1, characterized in that a soft metal indium sheet (11) is provided at the lower end of said lower heat sink (6).

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