CN-117287867-B - Magneto-thermal module for cryogenic magnetic refrigeration

CN117287867BCN 117287867 BCN117287867 BCN 117287867BCN-117287867-B

Abstract

The invention discloses a magneto-thermal module for extremely low-temperature magnetic refrigeration, which comprises a shell, a heat conduction assembly, heat conduction pieces and magnetic materials, wherein a sealing cavity is formed in the shell, an opening communicated with the sealing cavity is formed in the side wall of the shell, the heat conduction assembly comprises a plurality of heat conduction sheets, each heat conduction sheet is axially arranged in the sealing cavity, the planes of each heat conduction sheet are parallel to each other, a plurality of flow holes are formed in each heat conduction sheet, the flow holes are positioned in the sealing cavity, one or more fractal structures are further arranged in each flow hole, the fractal structures are of one-stage or multi-stage fractal structures, the heat conduction pieces are connected to the end parts of the heat conduction assembly and are at least partially positioned outside the shell and used for conducting heat, and the magnetic materials are arranged in gaps formed by the heat conduction sheets. The magnetocaloric module for extremely low temperature magnetic refrigeration can ensure good heat transfer performance while occupying less magnetic material volume.

Inventors

SHEN JUN
CHEN ZHUO
ZHAO YANAN
ZHENG WENSHUAI
LU YIAN
GAO JIAHAO
YANG LONG
LIU JUN
LI ZHENXING

Assignees

北京理工大学

Dates

Publication Date: 20260512
Application Date: 20231113

Claims (8)

1. A magnetocaloric module for use in cryogenic magnetic refrigeration, comprising: the shell is internally provided with a sealing cavity, and the side wall of the shell is provided with an opening communicated with the sealing cavity; The heat conduction assembly comprises a plurality of heat transfer sheets, each heat transfer sheet is axially arranged in the sealed cavity, the planes of each heat transfer sheet are parallel to each other, a plurality of flow holes are formed in each heat transfer sheet, the flow holes are positioned in the sealed cavity, one or more fractal structures are further arranged in each flow hole, and each fractal structure is one-stage or multi-stage fractal structure; the heat conduction piece is connected to the end part of the heat conduction assembly and is at least partially positioned outside the shell for heat conduction; a magnetic material provided in the space formed by each of the heat transfer sheets; The flow holes are strip-shaped, and each flow hole is transversely, longitudinally or obliquely distributed on the heat transfer sheet at intervals; The fractal structure comprises a first fractal sheet and a second fractal sheet, wherein one end of the first fractal sheet is fixed at one end of the circulation hole so that a first included angle is formed between the first fractal sheet and the heat transfer sheet, the first fractal sheet is provided with a first fractal hole, one end of the second fractal sheet is fixed at the other end of the first fractal hole so that a second included angle is formed between the second fractal sheet and the first fractal sheet, and the first included angle and the second included angle are zero to one hundred eighty degrees.
2. The magnetocaloric module for extremely low temperature magnetic refrigeration as in claim 1, wherein the fractal structure comprises a third fractal sheet, a fourth fractal sheet and a fifth fractal sheet, wherein one end of the third fractal sheet is fixed at one end of the flow hole so that a third included angle is formed between the third fractal sheet and the heat transfer sheet, one ends of the fourth fractal sheet and the fifth fractal sheet are fixed at the other end of the third fractal sheet in parallel, a fourth included angle is formed between the fourth fractal sheet and the third fractal sheet, and a fifth included angle is formed between the fifth fractal sheet and the third fractal sheet, wherein the third included angle, the fourth included angle and the fifth included angle are all zero to one hundred eighty degrees.
3. The magnetocaloric module for extremely low temperature magnetic refrigeration as set forth in claim 2, wherein the fractal structure comprises a sixth fractal sheet and a seventh fractal sheet, one end of the sixth fractal sheet is fixed at one end of the flow hole so that a sixth included angle is formed between the sixth fractal sheet and the heat transfer sheet, the other end of the sixth fractal sheet is provided with a concave groove, one end of the seventh fractal sheet is fixed in the concave groove at the other end of the sixth fractal sheet, and a seventh included angle is formed between the seventh fractal sheet and the sixth fractal sheet, wherein the sixth included angle and the seventh included angle are both zero to one hundred eighty degrees.
4. A magnetocaloric module for use in cryogenic magnetic refrigeration according to claim 1, wherein the housing comprises a shell and an end cap, the side walls of the shell being provided with the openings, the ends of the shell each being provided with the end cap to form the sealed cavity within the shell, at least part of the thermally conductive member being located outside the end cap.
5. The magnetocaloric module for cryogenic magnetic refrigeration of claim 4, wherein the end cap has the heat conducting member at an end facing away from the sealed cavity, a plurality of radially spaced positioning slots are provided at an end facing the receiving cavity, and the ends of the plurality of heat transfer sheets are respectively fitted in the positioning slots, so that the heat conducting member is connected to the heat transfer sheets through the end cap for conducting heat.
6. A magnetocaloric module for use in cryogenic magnetic refrigeration according to claim 4, wherein the end cap is centrally provided with a central aperture, and the ends of the plurality of heat transfer sheets are interconnected to form the heat conducting member, the heat conducting member passing through the central aperture such that at least part of the heat conducting member is located outside the end cap.
7. The magnetocaloric module of claim 6 further comprising a support frame mounted in said sealed cavity, a plurality of said heat transfer sheets passing through said support frame, said support frame being adjacent said heat transfer member, said heat transfer member being sealed with said central bore by a low temperature glue.
8. The magnetocaloric module for cryogenic magnetic refrigeration of claim 4, wherein the end cap is snap-fit to the housing, the cross-sectional shape of the outer profile of the end cap corresponds to the cross-sectional shape of the inner profile of the housing, and the outer side of the end cap is provided with a cryogenic adhesive.

Description

Magneto-thermal module for cryogenic magnetic refrigeration Technical Field The invention relates to the technical field of extremely low-temperature adiabatic demagnetization refrigeration, in particular to a magneto-thermal module for extremely low-temperature magnetic refrigeration. Background The extremely low temperature is below 1K, and the extremely low temperature is used for heat insulation, demagnetization and refrigeration, has the advantages of no dependence on gravity, no dependence on the rare material 3 He, intrinsic efficiency and the like, and is widely applied to space projects and ground laboratories. The magnetocaloric module is a source of cryogenic adiabatic demagnetization refrigerator cooling capacity. The magnetocaloric module is composed of magnetic material and heat transfer structure. The magneto-thermal effect of the magnetic material is utilized, namely, heat is released to the outside when excitation and absorbed from the outside when demagnetization is carried out, the thermal switch between the magneto-thermal module and the heat sink is conducted to release heat to the heat sink when excitation is carried out, and the thermal switch between the magneto-thermal module and the heat sink is disconnected to absorb heat from the cooled object when demagnetization is carried out, so that the purposes of cooling and refrigerating are achieved. Because the magnetic material needs to be placed in the magnetic field of the magnet, the internal space of the magnet is limited, the shape and the size of the cooled object are different, the cooled object is not easy to be placed in the magnet to directly exchange heat with the magnetic material, and the cooled object needs to be placed outside the magnetic field usually to avoid electromagnetic interference. Therefore, a heat transfer structure is required to conduct the cold generated in the demagnetizing process of the magnetic material to the cooled object. In addition, the temperature of the exciting process of the magnetic material is increased, and heat generated by the magnetic material needs to be transferred to the heat sink through the heat transfer structure. Magnetic materials commonly used in the 10 mK-1K temperature range are mostly paramagnetic salt crystals containing coordinated water. The magnetic materials commonly used in the temperature region include FAA (Fe (SO 4)2NH4·12H2 O, iron ammonium alum), CPA (CrK (SO 4)2·12H2 O, chrome potash), CMN (Ce 2Mg3(NO3)12·24H2 O, cerium magnesium nitrate) and the like, wherein the magnetic materials have poor heat conduction below 1K, CPA is taken as an example, the heat conductivity of the magnetic materials is about 10 -2W·m-1·K-1 at 100mK, SO that the internal cold energy cannot be directly transmitted to the outside by the heat conduction of the magnetic materials, the paramagnetic salt crystals are easy to dehydrate under the condition of high temperature or mechanical impact to cause the failure of the magnetic materials, such as the FAA is dehydrated at 35 ℃, and therefore, the heat transfer cannot be enhanced by grinding the magnetic materials into powder and mixing the powder with the powder of the high heat conduction materials. There are two types of heat transfer structures in the prior art: The first is that a bundle of metal wires (usually copper wires or gold wires, etc.) is made, and a plurality of metal wires are fixed on a threading framework designed according to the size of the magnetic material by adopting a manual threading mode. After the threading work is completed, the tail end of the metal wire is welded on an external heat transfer structure to realize heat exchange with the outside. The wire diameter of the wire used should be as small as possible in order to reduce eddy current heating in a varying magnetic field under conditions that satisfy the wire stress, and the number of wires should be as large as possible in order to uniformly distribute the wires in the magnetic material for heat exchange as sufficiently as possible. The magnetocaloric module as in Astro-E project used a heat transfer structure comprising 4500 gold wires with a wire diameter of 0.2 mm. The second is made of wire-cut heat-conducting metal bars, a thicker copper bar with the diameter equivalent to that of the magnetic material is processed into a plurality of thin copper bars through wire-cutting, and one end of the thick copper bar is kept from being cut off. The thin copper bars are uniformly distributed in the magnetic material. Because the thin copper rod contacted with the magnetic material is integrated with the heat transfer structure, welding is not needed, and the risk of heat transfer resistance caused by poor welding process is avoided. In the reinforced heat transfer structure of the metal wire in the prior art, on one hand, the tail end of a wire harness of the metal wire needs to be welded with other heat transfer structures (such as a heat conducting copper bar) t