An air-gap thermal switch

Abstract

The present invention discloses an air-gap thermal switch, which is characterized in that: the thermal switch includes a cold end (2), a first hot end (3) and a second hot end (7) that do not contact each other, and the three are hermetically fixed by a thin-wall support tube (1). The cold end (2) is sequentially inserted into the inner cavities of the first hot end (3) and the second hot end (7), and there are slits between the three; the cold end (2) with small holes is connected to an adsorbent container (5) filled with an adsorbent (6) through a connecting tube (4), and the adsorbent container (5) is communicated with the above-mentioned slit through the connecting tube (4). A heating sheet (8) connected to an external power supply through a lead wire is provided on the adsorbent container (5). The air-gap thermal switch of the present invention can control the open / closed state of the thermal switch by controlling the heating sheet, so as to achieve the effect of actively controlling the thermal switch and realize the control of the heat exchange between one cold end and two hot ends.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal switches, and more particularly to a gas-gap thermal switch for pre-cooling a cryogenic system. Background Art

[0002] In the field of cryogenic applications, it is often necessary to make the same component in different states of thermal isolation and thermal connection at different times. For example, in a multi-stage cryogenic system, the temperature of each stage is different, and there should be sufficient adiabatic performance between them. However, during the cooling process starting from room temperature, the coldest stage in the system needs to be cooled in the shortest time, which requires a good thermal connection between the coldest stage and the cold source. At this time, the thermal switch can meet the above requirements. The existing thermal switches are all designed with one cold end corresponding to one hot end. When used in a multi-stage system, thermal switches are installed between every two adjacent stages. In the initial cooling process, the multi-stage system is cooled step by step, that is, the intermediate stages will be cooled first, and finally the coldest stage will be cooled, which will greatly extend the cooling time. Summary of the Invention

[0003] The object of the present invention is to provide a gas-gap thermal switch for pre-cooling a cryogenic system in view of the problems existing in the prior art; one cold end of the gas-gap thermal switch can exchange heat with two hot ends, and can be used in a multi-stage cryogenic system to cool multiple stages simultaneously, greatly shortening the cooling time.

[0004] The object of the present invention is solved by the following technical solutions:

[0005] A gas-gap thermal switch, characterized in that: the thermal switch includes a cold end, a first hot end and a second hot end that do not contact each other, and the three are hermetically fixed by a thin-wall support tube to form a closed space containing a heat-conducting gas with a pressure less than 1 bar at room temperature. The cold end is sequentially inserted into the inner cavities of the first hot end and the second hot end, and there are slits between them; the cold end with a small hole is connected to an adsorbent container filled with an adsorbent through a connecting tube, and the adsorbent container is connected to the above-mentioned closed space through a connecting tube. A heating sheet connected to an external power supply through a lead wire is provided on the adsorbent container; in the non-heating state, the low-temperature adsorbent adsorbs the gas in the slit of the closed space, and the inside of the thermal switch becomes a high-vacuum state, and the cold end, the first hot end and the second hot end cannot exchange heat through the heat-conducting gas, and the thermal switch is in the off state; in the heating state, the adsorbent releases the heat-conducting gas, and the cold end, the first hot end and the second hot end exchange heat through the heat-conducting gas, and the thermal switch is in the closed state.

[0006] The cold-end mounting surface arranged perpendicular to the cold end and the first hot-end mounting surface arranged perpendicular to the first hot end that penetrates the inner cavity are parallel to each other, and the cold-end mounting surface and the first hot-end mounting surface are sealed and fixed by a thin-wall support tube. The first hot-end mounting surface arranged perpendicular to the first hot end and the second hot-end mounting surface arranged perpendicular to the second hot end and closing the inner cavity of the second hot end are parallel to each other, and the first hot-end mounting surface and the second hot-end mounting surface are sealed and fixed by a thin-wall support tube. There are slits between the first hot end and the cold end, between the first hot end and the second hot end, and between the second hot end and the cold end, and the above slits communicate with each other.

[0007] The thin-wall support tube, the cold end, the first hot end, the second hot end, the connecting tube and the adsorbent container form a sealed space, and the sealed space contains a heat-conducting gas with a pressure less than 1 bar at room temperature.

[0008] The width of the slit does not exceed 1 mm.

[0009] The cold end, the first hot end, and the second hot end are all made of materials with a thermal conductivity greater than 200 W / (m•K).

[0010] One of copper, aluminum, and silver is selected for the cold end, the first hot end, and the second hot end, and high-conductivity oxygen-free copper is preferred.

[0011] The thin-wall support tube is made of materials with a thermal conductivity less than 10 W / (m•K).

[0012] One of stainless steel or titanium alloy is selected for the material of the thin-wall support tube and the connecting tube; the wall thickness of the thin-wall support tube does not exceed 0.5 mm.

[0013] Activated carbon is selected as the adsorbent.

[0014] Helium is selected as the heat-conducting gas.

[0015] The present invention has the following advantages compared with the prior art:

[0016] The air-gap thermal switch of the present invention can control the open / closed state of the thermal switch by controlling the heating sheet, so as to achieve the effect of actively controlling the thermal switch; the thermal switch has no moving parts. When working in a multi-stage cryogenic system, the thermal switch is in the off state and the heating sheet is not heated, so no additional load will be introduced into the multi-stage cryogenic system. Therefore, in a multi-stage cryogenic system, the thermal switch is reliable and efficient, can shorten the pre-cooling time of the multi-stage cryogenic system, and is suitable for popularization and use. Brief Description of the Drawings

[0017] Attached Figure 1 is a schematic structural diagram of the air-gap thermal switch of the present invention;

[0018] Attached Figure 2Schematic diagram of the state of the air-gap thermal switch of the present invention when used in a multi-stage cryogenic system.

[0019] Wherein: 1 - thin-wall support tube; 2 - cold end; 3 - first hot end; 4 - connecting tube; 5 - adsorbent container; 6 - adsorbent; 7 - second hot end; 8 - heating sheet; 9 - GM refrigerator; 10 - vacuum chamber flange; 11 - vacuum chamber; 12 - 50K flange; 13 - 50K cold shield; 14 - 4K flange; 15 - 1.5K flange; 16 - 0.3K flange; 17 - 4K cold shield; 100 - thermal switch; 201 - cold end mounting surface; 301 - first hot end mounting surface; 701 - second hot end mounting surface. Specific embodiments

[0020] The present invention will be further described below in conjunction with the drawings and embodiments.

[0021] As Figure 1 shown: An air-gap thermal switch, the cold end 2, the first hot end 3, the second hot end 7 and the thin-wall support tube 1 are fixed by welding, and the weld is ensured to be sealed. The cold end 2, the first hot end 3 and the second hot end 7 do not contact each other and maintain a slit within 1 mm. The cold end 2, the first hot end 3 and the second hot end 7 are all made of materials with a thermal conductivity greater than 200 W / m•K, such as high-conductivity oxygen-free copper, silver, etc.; the thin-wall support tube 1 is made of materials with a thermal conductivity less than 10 W / m•K, such as stainless steel, titanium alloy, etc.; the adsorbent container 5 is filled with the adsorbent 6, and the adsorbent 6 is activated carbon or other materials with adsorption ability. The adsorbent container 5 and the cold end 2 are connected through the connecting tube 4. The thin-wall support tube 1, the cold end 2, the first hot end 3, the second hot end 7, the connecting tube 4 and the adsorbent container 5 form a closed space, and a heat-conducting gas with a pressure less than 1 bar at room temperature is contained in the closed space, and the heat-conducting gas is helium. A heating sheet 8 is installed on the upper surface of the adsorbent container 5, and the heating sheet 8 has two leads connected to an external power supply. When the power supply is energized, the heating sheet 8 converts electrical energy into heat energy to heat the adsorbent 6.

[0022] It should be noted that: the characteristic of the adsorbent 6 is that when the temperature decreases, the adsorption capacity of the adsorbent 6 will gradually increase, and when the temperature continues to decrease to a critical value, the adsorption capacity of the adsorbent 6 will suddenly increase and adsorb all the heat-conducting gas.

[0023] As Figure 1The working process of the thermal switch shown is as follows: When the heating sheet 8 is not heated, the cold quantity at the cold end 2 will be transferred to the adsorbent 6 through the connecting pipe 4 and the adsorbent container 5. The temperature of the adsorbent 6 drops below the critical value, and all the heat-conducting gas is adsorbed. There is no gas heat conduction in the slit between the cold end 2 and the first hot end 3 and the second hot end 7, and the thermal switch is in the off state. When the heating sheet 8 is heated, the temperature of the adsorbent 6 rises, releasing the heat-conducting gas. The heat-conducting gas fills the slit between the cold end 2 and the first hot end 3 and the second hot end 7. The cold end 2 exchanges heat with the first hot end 3 and the second hot end 7 through gas heat conduction, and the thermal switch is in the closed state.

[0024] Figure 2 It is a schematic diagram of a multi-stage cryogenic system device using an embodiment of the thermal switch of the present invention. As shown in the figure, the cold source of the present invention is provided by a GM refrigerator 9. The first-stage cold head of the GM refrigerator 9 is connected to the 50K flange 12, and the second-stage cold head of the GM refrigerator 9 is connected to the 4K flange 14. The cold end 2 of the thermal switch 100 is installed on the 4K flange 14, the first hot end 3 is installed on the 1.5K flange 15, and the second hot end 7 is installed on the 0.3K flange 16. When starting up, first turn on the GM refrigerator 9. All components of the system cool down from room temperature. At this time, the temperature of the adsorbent 6 in the thermal switch 100 is relatively high, and it can maintain the closed state without additional heating. When the 4K flange 14 cools down to about 20K, turn on the heating of the heating sheet 8. The adsorbent 6 releases the heat-conducting gas, and the cold end 2 exchanges heat efficiently with the first hot end 3 and the second hot end 7. The temperatures of the 4K flange 14, 1.5K flange 15, and 0.3K flange 16 continue to drop, maintaining the closed state of the thermal switch 100 for a certain period of time until the temperatures of the 4K flange 14, 1.5K flange 15, and 0.3K flange 16 are close to the same, all about 4K. Turn off the heating of the heating sheet 8. The temperature of the adsorbent 6 drops, and its adsorption capacity increases greatly. The heat-conducting gas is completely adsorbed, and there is no cold quantity exchange between the cold end 2 and the first hot end 3 and the second hot end 7. The thermal switch 100 is in the off state, and at this time, the precooling process of the multi-stage cryogenic system is completed. Figure 2 (Not shown in the figure) Start an additional refrigeration step to continue cooling the 1.5K flange 15 to 1.5K and the 0.3K flange 16 to 0.3K. At this time, the sample installed on the 0.3K flange 16 can be tested.

[0025] The air-gap type thermal switch of the present invention can control the on / off state of the thermal switch 100 by controlling the heating sheet 8, thus achieving the effect of actively controlling the thermal switch 100. This thermal switch 100 has no moving parts. When the multi-stage cryogenic system is working, the thermal switch 100 is in the off state and the heating sheet 8 is not heated, so it will not introduce additional load to the multi-stage cryogenic system. Therefore, in the multi-stage cryogenic system, this thermal switch 100 is reliable and efficient, can shorten the precooling time of the multi-stage cryogenic system, and is suitable for popularization and use.

[0026] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the present invention; the technologies not covered by the present invention can all be realized through the prior art.

Claims

1. An air-gap thermal switch, characterized in that: The thermal switch includes a cold end (2), a first hot end (3) and a second hot end (7) that do not contact each other, and the three are hermetically fixed by a thin-wall support tube (1). The cold end (2) is sequentially inserted into the inner cavities of the first hot end (3) and the second hot end (7), and there are slits between the three; the cold end (2) with small holes is connected to an adsorbent container (5) filled with an adsorbent (6) through a connecting tube (4), and the adsorbent container (5) is connected to the above-mentioned slit through the connecting tube (4). A heating sheet (8) connected to an external power supply through a lead wire is provided on the adsorbent container (5); a cold-end mounting surface (201) arranged perpendicular to the cold end (2) and a first hot-end mounting surface (301) arranged perpendicular to the first hot end (3) with a through inner cavity are parallel to each other, and the cold-end mounting surface (201) and the first hot-end mounting surface (301) are hermetically fixed by the thin-wall support tube (1). The first hot-end mounting surface (301) arranged perpendicular to the first hot end (3) and the second hot-end mounting surface (701) arranged perpendicular to the second hot end (7) and closing the inner cavity of the second hot end (7) are parallel to each other. The first hot-end mounting surface (301) and the second hot-end mounting surface (701) are hermetically fixed by the thin-wall support tube (1). There are slits between the first hot end (3) and the cold end (2), between the first hot end (3) and the second hot end (7), and between the second hot end (7) and the cold end (2), and the above-mentioned slits are connected; the thin-wall support tube (1) is made of a material with a thermal conductivity less than 10 W / (m•K).

2. The air-gap thermal switch according to claim 1, characterized in that: The thin-wall support tube (1), the cold end (2), the first hot end (3), the second hot end (7), the connecting tube (4) and the adsorbent container (5) form a sealed space, and the sealed space contains a heat-conducting gas with a pressure less than 1 bar at room temperature.

3. The air-gap thermal switch according to claim 1, characterized in that: The width of the slit does not exceed 1 mm.

4. The air-gap thermal switch according to claim 1, characterized in that: The cold end (2), the first hot end (3) and the second hot end (7) are all made of materials with a thermal conductivity greater than 200 W / (m•K).

5. The air-gap thermal switch according to claim 4, characterized in that: The cold end (2), the first hot end (3) and the second hot end (7) are all selected from one of copper, aluminum and silver.

6. The air-gap thermal switch according to claim 1, characterized in that: The material of the thin-wall support tube (1) and the connecting tube (4) is selected from one of stainless steel or titanium alloy; the wall thickness of the thin-wall support tube (1) does not exceed 0.5 mm.

7. The air-gap thermal switch according to claim 1, characterized in that: The adsorbent (6) is selected as activated carbon.

8. The air-gap thermal switch according to claim 2, characterized in that: The heat-conducting gas is selected as helium.

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