JP3310872B2 - Magnetic refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic refrigerator used for liquefying a cryogenic fluid such as hydrogen.

[0002]

FIG. 3 is a longitudinal sectional view of a conventional magnetic refrigerator. In the figure, reference numeral 1 denotes an insulated vacuum vessel for reducing intrusion heat, 2 denotes a flange portion of the insulated vacuum vessel, 3 denotes a liquid nitrogen tank for shielding radiant heat from room temperature, 4 denotes liquid nitrogen, and 5 denotes liquid nitrogen. Supply pipe 6; evaporating liquid nitrogen 4
Reference numeral 40 denotes a small gas refrigerator, for example, a Gifford McMahon refrigerator. 7 is a small refrigerator 4
Reference numeral 0 denotes a first-stage cold generating unit, 8 denotes a shield plate attached to the first-stage cold generating unit 7 for suppressing radiant heat from the liquid nitrogen tank 3, and 9 denotes a second-stage cold of the small refrigerator 40. The portions denoted by reference numerals 11 and 12 are contact-type heat-discharge switches for discharging heat from a magnetic body 20 described later. Reference numeral 11 denotes a copper portion of the exhaust heat switch. Reference numeral 12 denotes an insulator portion of the exhaust heat switch for reducing the influence of Joule heat generated when the magnetic field of the superconducting magnet 13 described below is operated in a pulsed manner. Quartz or the like having high conductivity is used. Reference numeral 10 denotes a copper block for connecting the second-stage cold generating section 9 of the small refrigerator to the copper portion 11 of the exhaust heat switch with good heat conductivity.

Reference numeral 14 denotes a stepping motor including a vertical movement mechanism, reference numeral 15 denotes a base for supporting the stepping motor 14, and reference numeral 16 denotes a rod connecting the exhaust heat switches 11, 12 and the stepping motor 14. 17 is an exhaust heat switch 1
An easily deformable copper mesh for maintaining thermal contact with the copper block 10 even when the first and second units are moved up and down by the stepping motor, 18 is a container for accommodating the heat-dissipating switch, and 19 is the same. Helium gas filled in the container, 2
0 is a magnetic substance, 21 is a cryogenic fluid to be liquefied. The helium gas 19 is for promoting heat transfer when the magnetic body 20 and the exhaust heat switch 12 are in contact with each other. For example, when the liquefied cryogenic fluid 21 to be liquefied is hydrogen or the like, the magnetic body 20 is made of GGG (Gd ₃ Ga ₅ O ₁₂ : gadolinium gallium garnet) or DAG (Dy ₃ Al
₅ O ₁₂ : dysprosium, aluminum, garnet).

Reference numeral 22 denotes a seal; 23, a spring for pressing the magnetic body 20 to supply necessary pressure to the seal 22;
Is a flange for receiving the force of the spring, 25 is a container for storing the cryogenic fluid 21 to be liquefied, 26 is a cylindrical container for containing the magnetic material 20, and 27 is a space between the magnetic material 20 and the cylindrical container 26. The gap is about several mm.

[0005] Reference numeral 13 denotes a superconducting magnet, 28 denotes liquid helium for cooling the superconducting magnet 13, 29 denotes a liquid helium container, and 30 denotes a liquid helium 28 injection tube. 3
Reference numeral 1 denotes an exhaust pipe for a vaporized gas of the liquid helium 28.

In the magnetic refrigerator having the above structure, a low temperature is generated by repeating the following steps, and the cryogenic fluid 21 to be liquefied is cryogenically cooled to liquefaction. (1) Adiabatic excitation process: When a magnetic field is applied by the superconducting magnet 13 in a state where the magnetic body 20 is not in contact with the exhaust heat switches 11 and 12 by the stepping motor 14, the temperature of the magnetic body 20 rises. (2) Isothermal magnetization process: When the temperature of the magnetic body 20 rises to a certain temperature, the heat removal switches 11 and 12 are lowered by the stepping motor 14 and applied to the magnetic body 20 in a state of contact with the magnetic body 20. Increase the magnetic field. At this time, the magnetic body 20 is kept at a constant temperature, and the exhaust heat switch 11,
12 to release heat. (3) Adiabatic demagnetization process: Next, the heat removal switches 11 and 12 are raised by the stepping motor 14, and the magnetic field is reduced while being separated from the magnetic material. At this time, the temperature of the magnetic body 20 decreases. (4) Isothermal demagnetization process: When the magnetic field is further reduced and the temperature of the magnetic material 20 decreases to the boiling point of the cryogenic fluid 21, the cryogenic fluid 21 that has been evaporated and turned into a gas liquefies on the wall surface of the magnetic material 20. Condense.

By repeating the above cycle,
A magnetic refrigerator can generate extremely low temperatures intermittently.
The evaporative gas around the magnetic body 20 is heated in the excitation process, and becomes a large thermal load on the magnetic body 20 in the isothermal demagnetization process, thereby lowering the refrigeration output. Therefore, there is a type in which the amount of evaporative gas around the magnetic body 20 is reduced, and the heat load on the magnetic body 20 is further reduced by covering the circumference of the magnetic body 20 with an adiabatic vacuum tank.

[0008]

The above-described conventional magnetic refrigerator has the following two problems to be solved. First, since the structure is such that the magnetic body 20 is pressed against the seal 22 by the spring 23, the seal is not sufficient, and
The high-temperature helium gas 19 sealed in 8 is mixed into the cryogenic fluid container 25, and the refrigeration output of the cryogenic fluid 21 decreases. Second, the heat switches 11 and 12 and the magnetic body 20 are likely to be in one-sided contact due to a manufacturing error or the like, and the heat exhausted from the magnetic body 20 becomes insufficient, and the performance of the refrigerator is reduced.

The present invention solves the above-mentioned disadvantages of the prior art, and prevents the high-temperature helium gas 19 in the exhaust heat switch container 18 from flowing into the cryogenic fluid container 25 by using a means instead of the seal 22. The purpose is to prevent one-sided contact between the exhaust heat switch containers 11 and 12 and the magnetic body 20.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and comprises a magnetic material, a superconducting magnet, a contact-type heat-dissipating switch, and a pole connected to a lower part of a container accommodating the heat-dissipating switch. A magnetic refrigerator provided with a low-temperature fluid storage container has the following features. (1) A magnetic material container made of a heat conductive material is installed at the lower end of the exhaust heat switch container via a vertically movable flexible member, and the outer wall of the magnetic material container is used for storing the cryogenic fluid. Exposure to the vapor of the cryogenic fluid in the container, containing the magnetic material in the magnetic material container, filling a filler for heat transfer between the magnetic material container and the magnetic material, The cryogenic fluid is condensed on the outer wall surface of the container. (2) In the magnetic refrigerator described in the above item (1), a vacuum heat insulating container is attached to the outside of the outer wall of the magnetic material container while keeping a gap.

[0011]

FIG. 1 is a longitudinal sectional view of a magnetic refrigerator according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. In FIG. 2, reference numeral 32 denotes a magnetic material container connected to the lower end of the exhaust heat switch container via a bellows 33;
0 is a magnetic substance contained in the same magnetic substance container, 3
Reference numeral 5 denotes a heat transfer filler having a high thermal conductivity filled between the magnetic material container 32 and the magnetic material 20, and a cylindrical member 34 attached to the outside of the magnetic material container 32 with a space 27 therebetween. It is an insulated vacuum container in the shape of a letter. The magnetic material container 32 and the heat insulating vacuum container 34 are connected at the upper part. Therefore, when the magnetic material container 32 moves with the movement of the magnetic material 20, the heat insulating vacuum container 34 moves together, so that the gap 27 is kept constant. The configuration of other parts is the same as that of the conventional technology (FIG. 3).

The magnetic material container 32 is made of a material having a high thermal conductivity and a high electric resistance such as stainless steel so as to suppress generation of heat due to eddy current when the magnetic field of the superconducting magnet 13 changes in a pulsed manner. Steel or aluminum is used.

The heat transfer filler 35 promotes heat transfer between the magnetic material 20 and the magnetic material container 32.
The cold generated in the magnetic material 20 is transmitted to the magnetic material container 32 by the filler, and condenses the evaporated gas of the cryogenic fluid 21 on the outer wall surface of the magnetic material container 32. The size of the gap 27 is appropriately selected so as to increase the amount of condensed and liquefied.

Since the magnetic substance container 32 is connected to the exhaust heat switch container 18 via the bellows 33, the exhaust heat switch container 18 and the cryogenic fluid storage container 25 are connected by the magnetic substance container 32 and the bellows 33. They are completely separated. Therefore, since the helium gas 19 in the exhaust heat switch container 18 cannot flow into the cryogenic fluid storage container 25, the liquefaction efficiency caused by the helium gas 19 flowing into the cryogenic fluid storage container 25 is reduced. Drop can be prevented.

The magnetic substance container 32 has a bellows 3
3. A spring 23 is attached to the lower part. Bellows 3
3 allows the magnetic body 20 to freely change the direction of the contact surface with the heat removal switch 12, and the spring 23 causes the magnetic body 20 to be pressed down when the magnetic body 20 comes into contact with the heat switch 12. Generates a repulsive force that pushes back upward. Therefore, when the heat-dissipating switches 11 and 12 descend obliquely with respect to the upper end surface of the magnetic body, the magnetic body 2
Since the repulsive force of the spring 23 acts on the portion where the gap between the heat switch 12 and the heat switch 12 is larger, the upper end surface of the magnetic body 20 moves so as to conform to the lower end surface of the heat switch 12, and no one-side contact occurs. It is possible to adhere.

In the excitation process, if a large amount of evaporative gas of the cryogenic fluid 21 heated by the magnetic material 20 exists around the magnetic material 20, the magnetic material
The heat load becomes zero, and the refrigeration output decreases. The adiabatic vacuum vessel 34 is provided to reduce the amount of evaporative gas of the heated cryogenic fluid 21 existing around the magnetic body 20 and increase the refrigeration output.

Since the magnetic refrigerator of this embodiment has the above-described configuration and operation, it is possible to prevent the magnetic body 20 from being in contact with the exhaust heat switch 12 at the time of exhausting heat and increase the amount of exhaust heat. Further, since the helium gas 19 in the exhaust heat switch container 18 cannot flow into the cryogenic fluid storage container 25, the helium gas 19 flows into the cryogenic fluid storage container 25. The resulting reduction in liquefaction efficiency can be prevented. Further, the presence of the adiabatic vacuum vessel 34 reduces the amount of evaporative gas of the heated cryogenic fluid 21 around the magnetic body, so that the refrigeration output can be increased. Further, the gap 27 for liquefying the cryogenic fluid 21 can maintain a constant size even when the magnetic body 20 moves, so that the cryogenic fluid 21 is effectively condensed and liquefied.

[0018]

In the magnetic refrigerator according to the present invention, a magnetic material container made of a heat conductive material is provided at the lower end of the heat exhaust switch container via a vertically movable flexible member. The outer wall of the storage container is exposed to the cryogenic fluid vapor in the cryogenic fluid storage container, the magnetic material is stored in the magnetic material storage container, and the magnetic material is transferred between the magnetic material storage container and the magnetic material. Since the cryogenic fluid is condensed on the outer wall surface of the magnetic substance storage container by filling with a heat filler, high-temperature helium gas in the exhaust heat switch container is prevented from flowing into the cryogenic fluid container. In addition, one-sided contact between the exhaust heat switch and the magnetic body is prevented.

In the case where the vacuum heat insulating container is attached to the outside of the outer wall of the magnetic material container with a gap kept therebetween, the amount of evaporative gas of the heated cryogenic fluid around the magnetic material can be reduced. , Can increase the refrigeration capacity.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a magnetic refrigerator according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG. 1;

FIG. 3 is a longitudinal sectional view of a conventional magnetic refrigerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulated vacuum container 2 Flange part 3 Liquid nitrogen tank 4 Liquid nitrogen 5 Liquid nitrogen supply pipe 6 Nitrogen gas escape pipe 7 First stage cold generation part of small refrigerator 40 8 Shield plate 9 Second stage cold generation of small refrigerator 40 Part 10 Copper block 11 Copper part of heat removal switch 12 Insulation part of heat removal switch 13 Superconducting magnet 14 Stepping motor 15 Stepping motor support base 16 Stepping motor rod 17 Copper net 18 Heat removal switch container 19 Helium Gas 20 Magnetic body 21 Cryogenic fluid 22 Seal 23 Spring 24 Flange 25 Cryogenic fluid storage container 26 Cylindrical container 27 Gap 28 Liquid helium 29 Liquid helium container 30 Liquid helium injection pipe 31 Helium gas escape pipe 32 Magnetic substance container 33 Bellows 34 Insulated vacuum vessel 35 Filling for heat transfer 40 small refrigerator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F25B 21/00

Claims (2)

(57) [Claims] 1. A magnetic refrigerator comprising a magnetic body, a superconducting magnet, a contact-type exhaust heat switch, and a cryogenic fluid storage container connected to a lower portion of a container containing the exhaust heat switch. At the lower end of the container, a magnetic material container made of a heat conductive material is installed via a vertically movable flexible member, and the outer wall of the magnetic material container is filled with the cryogenic fluid in the cryogenic fluid storage container. Exposure to steam, containing the magnetic material in this magnetic material container, filling a filler for heat transfer between the magnetic material container and the magnetic material, A magnetic refrigerator characterized by condensing a low-temperature fluid. 2. The magnetic refrigerator according to claim 1, wherein a vacuum heat insulating container is attached to the outside of the outer wall of the magnetic material container with a gap therebetween.