Combined thermal switch and refrigerator
By introducing a combination structure of multi-layer indium sheets and alumina gaskets into the thermal switch body, the thermal switch can be disconnected in stages, solving the problem of heat leakage in traditional thermal switches, improving the cooling efficiency and stability of the refrigerator, and achieving a lower cooling temperature.
Patent Information
- Application Number
- CN202520267929.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-19
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2035-02-19
AI Technical Summary
Existing thermal switches have residual heat leakage issues when disconnected, causing ultra-low temperature systems such as dilution refrigerators to fail to reach the expected temperature and resulting in insufficient cooling capacity.
A combined thermal switch is adopted, which includes adding a first superconducting layer and a second superconducting layer to the hot end of the thermal switch body. The superconducting transition temperature of the first superconducting layer is lower than that of the second superconducting layer. Complete disconnection is achieved by controlling the change of thermal conductivity in stages. Indium sheet and alumina gasket are used as superconducting materials.
It significantly reduces the heat leakage rate when the thermal switch is disconnected, improves the cooling efficiency and stability of the refrigerator, enables lower cooling temperatures, saves cooling capacity, and enhances the controllability and stability of the thermal switch.
Smart Images
Figure CN223771036U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of refrigeration and cryogenic technology, and in particular to a combined thermal switch and refrigeration unit. Background Technology
[0002] A dilution refrigerator is a commercially available refrigerator capable of stably providing extremely low temperatures below 10 mK. It is a key component of quantum computers and is widely used in quantum research. Currently, commonly used dry dilution refrigerators primarily rely on 4K pulse tube refrigerators for precooling, with thermal switches being a crucial component. During precooling, from room temperature (300 K) to the 4K liquid helium temperature, the thermal switch needs to be kept on to accelerate cooling. Once the liquid helium temperature is reached, it needs to be deactivated to minimize heat leakage. Beyond dilution refrigerators, thermal switches are also widely used in adiabatic demagnetizing refrigerators, 1K refrigerators, and other cryogenic systems.
[0003] Thermal switches are mainly classified into air-gap thermal switches, superconducting thermal switches, and mechanical thermal switches based on their working principle. Taking an air-gap thermal switch as an example, it achieves conductivity by filling the space between the upper and lower copper conductors with a heat-conducting gas, typically helium-4 or helium-3, through gas heat transfer. There is also a small chamber at the upper end filled with porous materials such as activated carbon. Because the adsorption capacity of activated carbon increases dramatically with decreasing temperature, it can adsorb helium at low temperatures, maintaining a good vacuum between the conductors. At this point, the thermal conductivity of the thermal switch is greatly reduced, achieving disconnection. If the thermal switch disconnects prematurely, or if it needs to be reconnected, the adsorbed helium can be released by heating the activated carbon, allowing gas heat transfer to resume.
[0004] However, activated carbon cannot completely adsorb all helium gas, leaving some residual gas that continues to conduct heat. Furthermore, when the disconnection temperature is too low, some helium may liquefy and remain in the bottom chamber. When this liquid helium reaches the superfluid temperature, superfluid film creep will occur, further enhancing heat conduction. The cooling capacity of a dilution refrigerator is very small, typically in the milliwatt or even microwatt range. Even a small amount of residual heat leakage can prevent the refrigerator from reaching the desired temperature. Therefore, addressing this residual heat leakage is crucial. Utility Model Content
[0005] This utility model provides a combined thermal switch and refrigerator to solve the defects of traditional thermal switches in the prior art, such as residual heat leakage and incomplete disconnection. It reduces heat leakage when the thermal switch is disconnected, greatly saves the limited cooling capacity of the refrigerator, and enables the refrigerator to achieve a lower cooling temperature. At the same temperature, the cooling capacity is also increased.
[0006] This utility model provides a combined thermal switch, comprising:
[0007] A thermal switch body having a hot end and a cold end disposed opposite to each other;
[0008] A first superconducting layer is disposed on the end face of the hot end and is in close contact with the end face of the hot end;
[0009] The second superconducting layer is disposed on the side of the first superconducting layer away from the hot end, and the first superconducting layer and the second superconducting layer are stacked in a stacked manner.
[0010] The superconducting transition temperature of the first superconducting layer is lower than that of the second superconducting layer.
[0011] According to the present invention, in a combined thermal switch, the first superconducting layer is an indium sheet.
[0012] According to the present invention, a combined thermal switch includes multiple layers of first superconducting layers, which are stacked on top of each other between the second superconducting layer and the end face of the hot end.
[0013] According to the present invention, in a combined thermal switch, the second superconducting layer is an alumina gasket.
[0014] According to the present invention, the radius of the cross-section of the first superconducting layer is greater than or equal to the radius of the end face of the hot end.
[0015] According to the present invention, in a combined thermal switch, the radius of the cross-section of the second superconducting layer is greater than or equal to the radius of the end face of the hot end.
[0016] According to the present invention, the thickness of the first superconducting layer along the axial direction is less than the thickness of the second superconducting layer along the axial direction.
[0017] According to the present invention, a combined thermal switch is provided in which the first superconducting layer is arranged in a ring shape;
[0018] And / or, the second superconducting layer is arranged in a ring shape.
[0019] According to the present invention, a combined thermal switch body includes either an air gap thermal switch or a convection thermal switch.
[0020] This utility model also provides a refrigeration unit, including the combined thermal switch as described above.
[0021] This invention provides a combined thermal switch and refrigerator. By adding a first superconducting layer and a second superconducting layer to the hot end of the thermal switch body, the superconducting transition temperature of the first superconducting layer is lower than that of the second superconducting layer. Both the first and second superconducting layers have good thermal conductivity at higher temperatures, further enhancing the thermal conductivity of the thermal switch. When the temperature drops below the superconducting transition temperature of the second superconducting layer, the second superconducting layer gradually becomes superconducting, and its thermal conductivity gradually decreases. As the temperature further decreases, the second superconducting layer enters deep superconductivity, and its thermal conductivity becomes very low. When the hot end temperature of the thermal switch reaches the superconducting transition temperature of the first superconducting layer, the first superconducting layer becomes superconducting, and its thermal conductivity decreases sharply, thereby causing the thermal switch body to disconnect. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0023] Figure 1 This is a schematic diagram of the combined thermal switch provided by this utility model.
[0024] Figure 2 This is a schematic diagram of the structure of the first superconducting layer provided by this utility model.
[0025] Figure 3 This is a schematic diagram of the structure of the second superconducting layer provided by this utility model.
[0026] Figure label:
[0027] 10. Combined thermal switch;
[0028] 100. Thermal switch body; 110. Cold end; 120. Hot end;
[0029] 200. First superconducting layer;
[0030] 300. Second superconducting layer. Detailed Implementation
[0031] The embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of this utility model.
[0032] In the description of the embodiments of this utility model, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this utility model. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0033] In the description of the embodiments of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model based on the specific circumstances.
[0034] In this embodiment of the utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0035] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0036] The following is combined Figures 1 to 3The combined thermal switch and refrigeration unit provided by the present invention will be described in detail through specific embodiments and application scenarios.
[0037] In the embodiments of this utility model, such as Figure 1 As shown, the combined thermal switch 10 includes a thermal switch body 100 and multiple superconducting layers. The thermal switch body 100 has a hot end 120 and a cold end 110 disposed opposite to each other. The first superconducting layer 200 is disposed on the end face of the hot end 120 and is in close contact with the end face of the hot end 120. The second superconducting layer 300 is disposed on the side of the first superconducting layer 200 away from the hot end 120. The first superconducting layer 200 and the second superconducting layer 300 are stacked. The superconducting transition temperature of the first superconducting layer 200 is lower than that of the second superconducting layer 300.
[0038] The thermal switch body 100 is the main structure of the combined thermal switch 10, having a hot end 120 and a cold end 110 arranged opposite to each other. The thermal switch body 100 serves as a heat transfer path, with its hot end 120 and cold end 110 connecting to the high-temperature zone and the low-temperature zone, respectively. By controlling the on and off states of the thermal switch, heat transfer and isolation are achieved, thereby regulating the temperature.
[0039] The first superconducting layer 200 is disposed on the end face of the hot end 120 and is in close contact with the end face of the hot end 120. The first superconducting layer 200 is made of a superconducting material with a low superconducting transition temperature.
[0040] The second superconducting layer 300 is disposed on the side of the first superconducting layer 200 away from the hot end 120, and is stacked with the first superconducting layer 200. The second superconducting layer 300 is made of a superconducting material with a high superconducting transition temperature.
[0041] At higher temperatures, the first superconducting layer 200 is in a normal state and has good thermal conductivity, which can enhance the thermal conductivity of the thermal switch and allow heat to be transferred smoothly from the hot end 120 to the cold end 110.
[0042] When the temperature drops below the superconducting transition temperature of the second superconducting layer 300, the second superconducting layer 300 gradually enters the superconducting state. With further decreases in temperature, the second superconducting layer 300 enters a deep superconducting state, where its thermal conductivity becomes extremely low. At this point, the second superconducting layer 300 acts as an insulator, significantly reducing heat transfer and partially disconnecting the thermal switch.
[0043] When the temperature continues to drop below the superconducting transition temperature of the first superconducting layer 200, the first superconducting layer 200 also enters the superconducting state, and its thermal conductivity decreases sharply. At this point, the second superconducting layer 300 further enhances the isolation effect of the thermal switch, achieving complete disconnection of the thermal switch.
[0044] The first superconducting layer 200 enables the thermal switch to have a lower heat leakage rate when it is turned off, thus improving the stability and reliability of the thermal switch.
[0045] The superconducting transition temperature of the first superconducting layer 200 is lower than that of the second superconducting layer 300. Due to the difference in superconducting transition temperatures between the first and second superconducting layers 200 and 300, the thermal switch exhibits a phased disconnection characteristic. First, when the temperature drops below the superconducting transition temperature of the second superconducting layer 300, the thermal switch partially disconnects; subsequently, when the temperature continues to drop below the superconducting transition temperature of the first superconducting layer 200, the thermal switch completely disconnects. This phased disconnection characteristic provides better controllability and stability during the disconnection process.
[0046] By adjusting the superconducting transition temperature of the first superconducting layer 200 and the second superconducting layer 300, the thermal switch can be adapted to different temperature requirements.
[0047] This application adds a first superconducting layer 200 and a second superconducting layer 300 to the hot end 120 of the thermal switch body 100. The superconducting transition temperature of the first superconducting layer 200 is lower than that of the second superconducting layer 300. Both the first and second superconducting layers 200 and 300 have good thermal conductivity at higher temperatures, further enhancing the thermal conductivity of the thermal switch. When the temperature drops below the superconducting transition temperature of the second superconducting layer 300, the second superconducting layer 300 gradually becomes superconducting, and its thermal conductivity gradually decreases. As the temperature further decreases, the second superconducting layer 300 enters deep superconductivity, and its thermal conductivity becomes very low. When the temperature of the hot end 120 of the thermal switch reaches the superconducting transition temperature of the first superconducting layer 200, the first superconducting layer 200 becomes superconducting, and its thermal conductivity decreases sharply, thereby causing the thermal switch body 100 to disconnect.
[0048] In some embodiments, the first superconducting layer 200 is an indium sheet.
[0049] Understandably, indium sheets have excellent ductility and can be easily processed into the required shapes and sizes to meet the design requirements of the thermal switch body 100. This ductility also allows for a close fit to the surface of the hot end 120 of the thermal switch body 100, ensuring maximum contact area between the two.
[0050] Indium exhibits high thermal conductivity at room temperature or relatively high temperatures. This allows indium to effectively conduct heat when a thermal switch needs to transfer heat, thereby accelerating the pre-cooling process of the refrigerator.
[0051] The indium foil has a relatively high superconducting transition temperature (around 3.4K). When the temperature of the hot end 120°C of the thermal switch drops to this temperature, the indium foil transitions to a superconducting state. In the superconducting state, the thermal conductivity of the indium foil decreases sharply, which helps to quickly reduce heat leakage from the thermal switch after precooling, thus enabling the thermal switch to open.
[0052] Since indium sheets conduct almost no heat in the superconducting state, using indium sheets as the first superconducting layer 200 in extremely low temperature environments can significantly reduce residual heat leakage when the thermal switch is in the off state.
[0053] The superconducting transition temperature of indium provides a natural temperature control point, allowing the thermal switch to automatically switch between on and off states without the need for external control mechanisms.
[0054] In some embodiments, the combined thermal switch 10 includes multiple layers of the first superconducting layer 200, which are stacked on top of each other between the second superconducting layer 300 and the end face of the hot end 120.
[0055] It is understandable that when the thermal conductivity of a single first superconducting layer 200 and a second superconducting layer 300 is not low enough, two or even more layers of the first superconducting layer 200 and the second superconducting layer 300 can be used to ensure that the thermal switch body 100 has a sufficiently low heat leakage rate when it is disconnected.
[0056] In some embodiments, the second superconducting layer 300 is an alumina gasket.
[0057] It is understandable that the superconducting transition temperature of alumina is approximately 15K, higher than that of the first superconducting layer (e.g., indium, with a superconducting transition temperature of approximately 3.4K). Thus, through a phased disconnection mechanism, the thermal switch gradually disconnects within different temperature ranges. First, when the temperature drops to near the superconducting transition temperature of alumina, the alumina begins to transition to a superconducting state, initially achieving partial disconnection. Then, as the temperature further decreases below the superconducting transition temperature of indium, the latter also enters a superconducting state, further enhancing the thermal isolation effect. By controlling the heat conduction path in stages, the system can better adapt to different needs from pre-cooling to stable operation, improving the overall efficiency and performance of the refrigerator.
[0058] Of course, in other embodiments, the alumina gasket can be replaced with other superconducting materials. Depending on the required disconnection temperature of each system, different superconducting materials can be selected to achieve better thermal switching.
[0059] This invention introduces a combined structure of multilayer indium sheets and alumina gaskets into a traditional thermal switch, enabling the thermal switch to maintain high thermal conductivity and excellent conduction performance even when turned on. Crucially, when the temperature reaches the pre-cooling temperature and the thermal switch needs to be turned off, the superconducting properties of indium and alumina, which are poor conductors of heat (especially when the material is deeply superconducting, it transfers almost no heat), result in an extremely low thermal conductivity for the combined thermal switch.
[0060] The ratio of the thermal conductivity of a thermal switch when it is on to its thermal conductivity when it is off is called the on / off ratio. The on / off ratio is an important parameter for evaluating switch performance, and a higher ratio is better. This invention reduces heat leakage when the thermal switch is off, thereby lowering the thermal conductivity when off, and thus significantly increasing the on / off ratio of the combined thermal switch 10.
[0061] This invention significantly reduces heat leakage when the thermal switch is disconnected, thereby greatly saving the limited cooling capacity of the refrigerator and enabling the refrigerator to achieve lower cooling temperatures. At the same temperature, the cooling capacity is also increased, significantly improving the shortcomings of the prior art.
[0062] Reference Figure 1 The radius of the cross-section of the first superconducting layer 200 is greater than or equal to the radius of the end face of the hot end 120.
[0063] Understandably, by making the radius of the cross-section of the first superconducting layer 200 greater than or equal to the radius of the end face of the hot end 120, i.e., fully covering the end face of the hot end 120, the maximum contact area between the two can be ensured. This ensures that heat can be rapidly transferred from the hot end 120 through the first superconducting layer 200, maximizing heat conduction efficiency. At the same time, it can also reduce radiative heat transfer at the hot end 120, further reducing heat leakage.
[0064] Reference Figure 1 The radius of the cross-section of the second superconducting layer 300 is greater than or equal to the radius of the end face of the hot end 120.
[0065] Understandably, the cross-sectional radius of the second superconducting layer 300 is greater than or equal to the radius of the hot end 120, ensuring maximum contact area between it and the first superconducting layer 200. During the pre-cooling stage, this ensures that heat can be rapidly transferred from the first superconducting layer 200 to the second superconducting layer 300 and ultimately dissipated, maximizing heat transfer efficiency. Furthermore, the larger contact area reduces thermal resistance, allowing for more uniform heat distribution and transfer, avoiding localized overheating or uneven cooling. Simultaneously, it also reduces radiative heat transfer at the hot end 120, further minimizing heat leakage.
[0066] Reference Figures 1 to 3The thickness of the first superconducting layer 200 along the axial direction is less than the thickness of the second superconducting layer 300 along the axial direction.
[0067] Understandably, by designing the thickness of the first superconducting layer 200 to be less than that of the second superconducting layer 300, a temperature gradient can be created in the thermal switch. As the temperature decreases, the thicker second superconducting layer 300 gradually becomes superconducting, reducing heat flow and achieving initial disconnection of the thermal switch; because the first superconducting layer 200 is thinner, it rapidly becomes superconducting when it reaches the superconducting transition temperature, thus achieving complete disconnection of the thermal switch.
[0068] Reference Figure 2 and Figure 3 The first superconducting layer 200 is arranged in a ring shape; the second superconducting layer 300 is arranged in a ring shape.
[0069] Understandably, the annular arrangement of the first superconducting layer 200 and the second superconducting layer 300 provides a uniform heat conduction path. This means heat can be evenly distributed along the annular path, avoiding localized hotspots and improving the overall heat conduction efficiency of the thermal switch. Simultaneously, the annular structure helps disperse thermal stress caused by temperature changes, reducing stress concentration due to thermal expansion and contraction, thereby improving the mechanical stability and lifespan of the thermal switch. Furthermore, when the annular superconducting layers enter the superconducting state, they can form a continuous thermal barrier, effectively blocking heat flow and providing better thermal insulation when the thermal switch is turned off.
[0070] In some embodiments, the thermal switch body 100 includes either an air gap thermal switch or a convection thermal switch.
[0071] Of course, in other embodiments, the thermal switch body 100 may also be other forms of thermal switch, which are not specifically limited here.
[0072] This utility model also provides a refrigerator, which includes the above-mentioned combined thermal switch 10. The specific structure of the combined thermal switch 10 is as described in the above embodiment. It can be understood that since the above-mentioned combined thermal switch 10 is used in the refrigerator, the embodiment of the refrigerator includes all the technical solutions of all the embodiments of the above-mentioned combined thermal switch 10, and the technical effects achieved are exactly the same, so they will not be repeated here.
[0073] In one specific embodiment, in an example of a domestically produced dilution refrigeration unit, a traditional air-gap thermal switch was initially used. Because the traditional thermal switch could not completely disconnect, there was significant heat leakage, causing the evaporator temperature to remain above 1.2K, far exceeding normal levels. By adding an indium sheet and an alumina gasket to the bottom of the traditional thermal switch, transforming it into the novel combined thermal switch 10 of this invention, the evaporator temperature dropped below 1K while keeping other parameters unchanged, indicating a significant reduction in heat leakage. Subsequently, using a combination of two indium sheets and an alumina gasket further reduced the evaporator temperature to 600mK, meeting the usage requirements.
[0074] In one specific embodiment, in a domestically produced 1K refrigerator example, a traditional air-gap thermal switch was initially used. Because the traditional thermal switch could not completely disconnect, there was significant heat leakage, preventing the system from properly liquefying helium-4 gas. Due to the lack of a stable helium liquid surface, the temperature of the 1K disk could only drop to slightly over 2K, far short of the target. By adding an indium sheet and an alumina gasket to the bottom of the traditional thermal switch, transforming it into the novel combined thermal switch 10 of this invention, while keeping other parameters unchanged, the helium-4 gas liquefied successfully, and the temperature of the 1K disk dropped to around 1K, indicating a significant reduction in heat leakage.
[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. A combination thermal switch, characterized by, The combination thermal switch comprises: a thermal switch body having a hot end and a cold end arranged oppositely; a first superconducting layer arranged on an end face of the hot end and in close contact with the end face of the hot end; a second superconducting layer arranged on a side of the first superconducting layer away from the hot end, the first superconducting layer and the second superconducting layer being arranged in a stacked manner; wherein a superconducting transition temperature of the first superconducting layer is lower than a superconducting transition temperature of the second superconducting layer.
2. The combination thermal switch of claim 1, wherein, The first superconducting layer is an indium sheet.
3. The combination thermal switch of claim 1, wherein, The combination thermal switch comprises a plurality of layers of the first superconducting layer arranged in a stacked manner between the second superconducting layer and the end face of the hot end.
4. The combination thermal switch of claim 1, wherein, The second superconducting layer is an aluminum oxide gasket.
5. The combination thermal switch of claim 1, wherein, A radius of a cross section of the first superconducting layer is greater than or equal to a radius of the end face of the hot end.
6. The combination thermal switch of claim 1, wherein, A radius of a cross section of the second superconducting layer is greater than or equal to a radius of the end face of the hot end.
7. The combination thermal switch of claim 1, wherein, A thickness of the first superconducting layer along an axial direction is less than a thickness of the second superconducting layer along the axial direction.
8. The combination thermal switch of claim 1, wherein, The first superconducting layer is arranged in a ring shape. The second superconducting layer is arranged in a ring shape.
9. The combination thermal switch of claim 1, wherein, The thermal switch body comprises any one of an air gap thermal switch or a convection thermal switch.
10. A refrigerator characterized by comprising: The combination thermal switch comprises any one of claims 1 to 9.