Magnetothermal module, preparation method and heat insulation and demagnetization refrigeration device
By using porous foam metal to replace the traditional thermal bus structure in extremely low temperature refrigeration technology, the problems of small specific surface area and long production time in the prior art are solved, and more efficient heat transfer capacity and lower refrigeration cost are achieved.
Patent Information
- Application Number
- CN202311679124.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-08
- Publication Date
- 2025-06-10
AI Technical Summary
In the existing extremely low temperature refrigeration technology, the thermal bus structure of the magnetothermal module has problems such as small specific surface area, long production time, unsolid welding and difficult processing, which affects the refrigeration efficiency and cost.
Porous foam metal is used to replace the traditional thermal bus structure, and a sealing cavity is formed through sleeves, end caps and heat transfer copper rods. Built-in foam metal and magnetothermal materials are used to bond and seal with epoxy resin.
The heat exchange area between the magnetothermal material and the heat transfer structure is improved, the heat transfer capacity between the crystal and the heat transfer structure is enhanced, the loss of refrigeration fluid is reduced, and the production time and cost are saved.
Smart Images
Figure CN120115868A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of cryogenic refrigeration technology, and particularly relates to a magnetic thermal module, a preparation method, and an adiabatic demagnetization refrigeration device. Background Art
[0002] Cryogenic refrigeration technology is an important scientific and technological field, which is widely used in frontier fields such as space exploration and quantum technology. In astronomical observations, condensed matter physics experiments, and industrial applications, high-resolution detectors must be cooled to extremely low temperatures (<0.3K) to obtain the required sensitivity, such as bolometers, superconducting TES sensors, and superconducting tunnel junction detectors. Among several cryogenic refrigeration methods, adiabatic demagnetization refrigeration (ADR for short) is based on the magnetocaloric effect of solid materials, that is, the heat effect generated by magnetic thermal materials with the change of the external magnetic field for refrigeration. It has the advantages of high efficiency, independence from gravity, no moving parts, and operation without relying on scarce resources 3 He.
[0003] A typical ADR consists of a superconducting magnet, a thermal switch, a magnetic thermal module, a high-temperature side heat sink, and a low-temperature side cold head. The magnetic thermal module releases / absorbs heat in a changing magnetic field, and cooperates with the conduction and disconnection of the thermal switch to complete the refrigeration cycle.
[0004] The design of the heat transfer structure in the magnetic thermal module is very important, especially for the magnetic thermal materials in the low-temperature region. Because the size of the hydrated paramagnetic salt grains is small, and the boundary thermal resistance between the grains is very large, it is often necessary to design a special heat transfer structure to assist the grains in transferring heat outward. Its heat transfer structure includes: a heat bus and a heat conducting copper rod. The heat bus mainly plays the role of assisting the crystal itself in transferring heat outward, and the heat conducting copper rod mainly plays the role of assisting the connection between the magnetic thermal module and other subsequent structures.
[0005] When manufacturing a heat bus type magnetic thermal module, there are the following problems:
[0006] 1. Regarding the specific surface area of the heat bus. At extremely low temperatures, there is a large Kapitza thermal resistance between the crystal and the heat bus. To reduce this thermal resistance, it is necessary to increase the contact area between the crystal and the heat bus. However, the specific surface areas of the existing two heat bus structures (thread-passing type and electrical discharge wire cutting type) are small, and increasing the heat transfer area of the heat bus often means the loss of a large amount of effective refrigeration working medium.
[0007] 2. Regarding the manufacture of the thread-passing type heat bus. The thread-passing type structure requires threading hundreds or even more thinner metal wires (usually 0.2mm) into a punched metal sheet (hole diameter 0.5mm). Since the threading is often made manually, for a magnetic thermal module with a diameter of 30mm, the threading usually takes 2 - 3 days.
[0008] 3. For the welding between the thread-through type heat bus and the heat transfer copper rod. During the heating process of flame welding and argon arc welding, oxidation of copper will inevitably occur; although vacuum brazing can effectively avoid the oxidation problem, the solder will flow to the middle section of the heat bus under capillary action, resulting in insufficient filling of the welding material at this position and poor heat transfer between the copper rod and the heat bus. Moreover, during the process of the solder flowing from the end of the heat bus to the middle section of the heat bus, multiple metal wires will be welded into one strand, weakening the flexibility and being not conducive to the final positioning and fitting with the housing.
[0009] 4. For the fabrication of the electric discharge wire cutting type heat bus. Although this structure does not require welding the heat transfer copper rod and the heat bus, affected by the processing technology, the material of the heat bus used is usually oxygen-free copper annealed at high temperature, which is softer than ordinary pure copper and is prone to deformation during processing; in addition, the diameter of the heat bus cut by electric discharge wire cutting is often larger than that of the finished metal wire, and the processing difficulty and cost of the heat bus with higher precision and thinner diameter will increase sharply. Summary of the Invention
[0010] In view of this, it is necessary to provide a magnetic thermal module, a preparation method and an adiabatic demagnetization refrigeration device that use foam metal to replace the existing heat bus in view of the defects existing in the prior art.
[0011] To solve the above problems, the present application adopts the following technical solutions:
[0012] One object of the present application is to provide a magnetic thermal module, including: a sleeve, end caps respectively arranged on both sides around the sleeve, and heat transfer copper rods, wherein the sleeve, the end caps and the heat transfer copper rods form a sealed cavity, and foam metal and magnetic thermal material are distributed in the sealed cavity.
[0013] In some embodiments, the foam metal includes but is not limited to copper or silver.
[0014] In some embodiments, the sleeve includes but is not limited to G10 epoxy glass fiber or stainless steel.
[0015] In some embodiments, a plurality of small holes are provided on the inner wall of the sleeve.
[0016] In some embodiments, the magnetic thermal material includes but is not limited to hydrated paramagnetic salts, and the hydrated paramagnetic salts include ferric ammonium alum and potassium chromium alum.
[0017] Another object of the present application is to provide a preparation method of the magnetic thermal module as described above, including the following steps:
[0018] Select foam metal;
[0019] Fix the heat transfer copper rod and the foam metal to make a heat transfer skeleton;
[0020] Put the sleeve and the end cap on the heat transfer skeleton and bond them with epoxy resin to form a sealed magnetocaloric module container;
[0021] Distribute the magnetocaloric material in the magnetocaloric module container and seal it with epoxy resin to form the magnetocaloric module.
[0022] In some embodiments, in the step of selecting the metal foam, it specifically includes:
[0023] Select metal foams with appropriate PPI, porosity, and pore diameter, cut them into appropriate sizes. The diameter of the metal foam is slightly smaller than the diameter of the end concave platform of the heat transfer copper rod. The metal foam includes but is not limited to copper or silver.
[0024] In some embodiments, in the step of fixing the heat transfer copper rod and the metal foam to make the heat transfer skeleton, it specifically includes:
[0025] Place solder between the end concave platform of the heat transfer copper rod and the metal foam, and weld the assembled structure to make the heat transfer skeleton. The welding includes but is not limited to vacuum brazing, flame welding, argon arc welding, electron beam welding, ion beam welding, laser welding, or other processes capable of local welding.
[0026] In some embodiments, in the step of distributing the magnetocaloric material in the magnetocaloric module container and sealing it with epoxy resin to form the magnetocaloric module, it specifically includes:
[0027] Open several small holes on the inner wall of the sleeve, put the sleeve on the heat transfer skeleton, and distribute the magnetocaloric material in the heat transfer skeleton. The sleeve includes but is not limited to G10 epoxy glass fiber or stainless steel. The magnetocaloric material includes but is not limited to hydrated paramagnetic salts, and the hydrated paramagnetic salts include ammonium iron alum and potassium chrome alum.
[0028] The third object of this application is to provide a magnetic adiabatic demagnetization refrigeration device including the magnetocaloric module described above.
[0029] This application adopts the above technical solutions, and the beneficial effects are as follows:
[0030] The magnetocaloric module, preparation method, and magnetic adiabatic demagnetization refrigeration device provided by this application include: a sleeve, end caps respectively arranged on both sides of the sleeve, and a heat transfer copper rod. The sleeve, the end caps, and the heat transfer copper rod form a sealed cavity, and a metal foam and a magnetocaloric material are distributed in the sealed cavity. This application uses porous metal foam to replace the traditional heat bus structure. The specific surface area of the traditional heat bus is 0.05m 2 / g. The specific surface area of copper foam is greatly affected by the structural size and can usually reach 1 m 2 / g. The specific surface area of foam metal is larger than that of traditional heat buses. Therefore, under the premise of sacrificing as little crystal quality as possible, the heat transfer area between the magnetocaloric material and the heat transfer structure can be increased to enhance the heat transfer ability between the crystal and the heat transfer structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for describing the embodiments of the present application or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0032] Figure 1 FIG. 1 is a schematic structural diagram of a magnetothermal module provided in Embodiment 1 of the present invention;
[0033] Figure 2 FIG. 2 is a flowchart for preparing the magnetothermal module provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and should not be construed as a limitation of the present application.
[0035] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application.
[0036] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.
[0037] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and embodiments.
[0038] Embodiment 1
[0039] Please refer to Figure 1 , the structural schematic diagram of the magnetothermal module provided by the embodiment of the present application, including: a sleeve 10, end caps 20 respectively arranged on both sides of the sleeve 10, and heat transfer copper bars 30. The sleeve 10, the end caps 20 and the heat transfer copper bars 30 form a sealed cavity, and a foam metal 40 and a magnetothermal material 50 are distributed in the sealed cavity. The specific implementation manners of each component are described in detail below.
[0040] In this embodiment, the sleeve 10 includes, but is not limited to, G10 epoxy fiberglass or stainless steel.
[0041] It can be understood that the sleeve 10 is not limited to the above materials, and can also be other non-magnetic metal materials, or other non-metallic materials with better low-temperature strength.
[0042] Furthermore, a plurality of small holes are provided on the inner wall of the sleeve 10.
[0043] It can be understood that a plurality of small holes are provided inside the sleeve 10 to facilitate the circulation of the solution during crystal growth.
[0044] In this embodiment, the foam metal 40 includes, but is not limited to, copper or silver.
[0045] It can be understood that in this embodiment, porous metal copper is used to replace the traditional heat bus structure. The specific surface area of the foam metal is larger than that of the traditional heat bus. The typical specific surface area of the traditional heat bus is 0.05 m 2 / g. The specific surface area of the foam copper is greatly affected by the structural size, and some can reach 1 m 2 / g. Therefore, on the premise of sacrificing as little crystal quality as possible, the heat transfer area between the magnetothermal material and the heat transfer structure can be increased to enhance the heat transfer ability between the crystal and the heat transfer structure.
[0046] In addition, the manufacturing process of the foam metal is mature and there are many commercial products. Compared with the wire-type heat bus, it can be directly purchased on the market without manual production, saving the production time cost and labor cost. And the price of the foam metal is cheap. Compared with the high processing cost brought by the wire-cut heat bus, using the foam metal as the heat transfer structure can save economic costs.
[0047] In this embodiment, the magnetothermal material 50 includes, but is not limited to, hydrated paramagnetic salts, and the hydrated paramagnetic salts include ammonium iron alum and potassium chromium alum.
[0048] Specifically, hydrated paramagnetic salts, such as ammonium iron alum (Fe(SO 4 ) 2 NH 4 ·12H 2 O, abbreviated as FAA), potassium chromium alum (CrK(SO 4 )2 ·12H 2 O, abbreviated as CPA), etc. Its advantages are that the magnetic order transition temperature is low (FAA 26 mK, CPA 9 mK), and refrigeration at 10 mK or even lower temperatures can be achieved. Its disadvantages are that the thermal conductivity is very small, the grain size is small, and the boundary thermal resistance between grains is large, which will have two adverse effects on the performance of the ADR: one is to increase the heat transfer temperature difference, affecting the efficiency and refrigeration temperature; the other is to extend the cycle period, affecting the specific power of the system (especially for continuous ADR).
[0049] It should be noted that in practice, appropriate magnetocaloric materials can be selected according to the application scenario.
[0050] For the magnetothermal module provided in the above embodiment of the present application, porous foam metal is used to replace the traditional heat bus structure. The typical specific surface area of the traditional heat bus is 0.05 m 2 / g. The specific surface area of copper foam is greatly affected by the structural size, and some can reach 1 m 2 / g. The specific surface area of foam metal is larger than that of the traditional heat bus. Therefore, on the premise of sacrificing as little crystal quality as possible, the heat transfer area between the magnetocaloric material and the heat transfer structure can be increased to enhance the heat transfer ability between the crystal and the heat transfer structure, and it can be used in adiabatic demagnetization refrigeration devices.
[0051] Embodiment 2
[0052] Please refer to Figure 2 together for a preparation method of the magnetothermal module provided in this Embodiment 2, including the following steps S110 to S140. The implementation methods of each step are described in detail below.
[0053] Step S110: Select foam metal.
[0054] In this embodiment, in the step of selecting foam metal, it specifically includes:
[0055] Select metal foam with appropriate PPI (number of pores per inch length), porosity, and pore diameter, cut it into appropriate sizes. The diameter of the foam metal is slightly smaller than the diameter of the end concave platform of the heat transfer copper rod. The foam metal includes but is not limited to copper or silver.
[0056] Step S120: Fix the heat transfer copper rod and the foam metal to form a heat transfer skeleton.
[0057] In this embodiment, in the step of fixing the heat transfer copper rod and the foam metal to form a heat transfer skeleton, it specifically includes:
[0058] Place solder between the end concave platform of the heat transfer copper rod and the foam metal ( Figure 1As shown in 60, and weld the assembled structure to form a heat transfer skeleton. The welding includes but is not limited to vacuum brazing, flame welding, argon arc welding, electron beam welding, ion beam welding, laser welding or other processes capable of performing local welding.
[0059] It should be noted that: in order to ensure the brazing effect, corresponding welding fixtures will actually be designed to ensure that appropriate stress can be provided to the copper foam during the welding process to strengthen the welding. At the same time, the applied stress should not be too large, otherwise the copper foam will be crushed.
[0060] It can be understood that although there will be a problem of solder climbing during the welding between the foam metal and the copper rod, due to the use of welding fixtures to assist in applying stress during the welding process, the solder can still ensure relatively tight filling in the gap between the copper foam and the heat transfer copper rod after welding.
[0061] Step S130: Sleeve the sleeve and the end cap on the heat transfer skeleton and bond them with epoxy resin to form a sealed magnetic thermal module container;
[0062] Step S140: Distribute the magnetic thermal material in the magnetic thermal module container and seal it with epoxy resin to form the magnetic thermal module.
[0063] Specifically, several small holes are opened on the inner wall of the sleeve. The sleeve is sleeved on the heat transfer skeleton, and the magnetic thermal material is distributed in the heat transfer skeleton. The sleeve includes but is not limited to G10 epoxy glass fiber or stainless steel. The magnetic thermal material includes but is not limited to hydrated paramagnetic salts, and the hydrated paramagnetic salts include ammonium iron alum and potassium chrome alum.
[0064] It can be understood that several small holes are opened on the inside of the sleeve 10 to facilitate the circulation of the solution during crystal growth.
[0065] It can be understood that crystal growth is carried out in the magnetic thermal module by the cooling crystallization method. The crystal growth direction is not limited to horizontal growth or vertical growth. Holes can also be opened at the end instead of the side, and then vertical growth of the crystal is carried out.
[0066] In the preparation method of the magnetic thermal module provided by the above embodiments of the present application, porous foam metal is used to replace the traditional heat bus structure. The typical specific surface area of the traditional heat bus is 0.05 m 2 / g. The specific surface area of copper foam is greatly affected by the structural size, and some can reach 1 m 2 / g. The specific surface area of foam metal is larger than that of the traditional heat bus. Therefore, on the premise of sacrificing as little crystal quality as possible, the heat exchange area between the magnetic thermal material and the heat transfer structure can be increased to strengthen the heat transfer ability between the crystal and the heat transfer structure, and it can be used in adiabatic demagnetization refrigeration devices.
[0067] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0068] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.
Claims
1. A magnetocaloric module, characterized in that, it comprises: a sleeve, end caps respectively arranged on both sides of the sleeve, and heat transfer copper bars. The sleeve, the end caps and the heat transfer copper bars form a sealed cavity, and a metal foam and a magnetocaloric material are distributed in the sealed cavity.
2. The magnetocaloric module according to claim 1, characterized in that, the metal foam includes but is not limited to copper or silver.
3. The magnetocaloric module according to claim 1, characterized in that, the sleeve includes but is not limited to G10 epoxy glass fiber or stainless steel.
4. The magnetocaloric module according to claim 1, characterized in that, a plurality of small holes are provided on the inner wall of the sleeve.
5. The magnetocaloric module according to claim 1, characterized in that, the magnetocaloric material includes but is not limited to hydrated paramagnetic salts, and the hydrated paramagnetic salts include ammonium iron alum and potassium chromium alum.
6. A preparation method of the magnetocaloric module according to any one of claims 1 to 5, characterized in that, it comprises the following steps: select a metal foam; fix the heat transfer copper bar and the metal foam to make a heat transfer skeleton; put the sleeve and the end caps on the heat transfer skeleton and bond them with epoxy resin to form a sealed magnetocaloric module container; distribute the magnetocaloric material in the magnetocaloric module container and seal it with epoxy resin to form the magnetocaloric module.
7. The preparation method of the magnetocaloric module according to claim 6, characterized in that, in the step of selecting a metal foam, it specifically comprises: select a metal foam with appropriate PPI, porosity and pore diameter, cut it into appropriate sizes, the diameter of the metal foam is slightly smaller than the diameter of the end concave platform of the heat transfer copper bar, and the metal foam includes but is not limited to copper or silver.
8. The preparation method of the magnetocaloric module according to claim 7, characterized in that, in the step of fixing the heat transfer copper bar and the metal foam to make a heat transfer skeleton, it specifically comprises: place solder between the end concave platform of the heat transfer copper bar and the metal foam, and weld the assembled structure to make a heat transfer skeleton. The welding includes but is not limited to vacuum brazing, flame welding, argon arc welding, electron beam welding, ion beam welding, laser welding or other processes capable of performing local welding.
9. The preparation method of the magnetocaloric module according to claim 1, characterized in that, in the step of putting the sleeve and the end caps on the heat transfer skeleton and bonding them with epoxy resin to form a sealed magnetocaloric module container, it specifically comprises: drill a plurality of small holes on the inner wall of the sleeve, put the sleeve on the heat transfer skeleton, and distribute the magnetocaloric material in the heat transfer skeleton. The sleeve includes but is not limited to G10 epoxy glass fiber or stainless steel, and the magnetocaloric material includes but is not limited to hydrated paramagnetic salts, and the hydrated paramagnetic salts include ammonium iron alum and potassium chromium alum.
10. An adiabatic demagnetization refrigeration device, characterized in that, it comprises the magnetocaloric module according to any one of claims 1 or 6.