JPH0331978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus using a solid as a heat storage medium to improve cooling efficiency in a magnetic refrigeration apparatus.

Compared to conventional gas refrigeration equipment, magnetic refrigeration (i) has a smaller molar volume of the working medium, which essentially makes the equipment smaller and lighter; (ii) it does not require a compressor for the working medium, resulting in lower noise; (iii) Since most of the operations are electromagnetic, computer control is easy, and a highly reliable refrigeration system can be obtained.

It has many features such as, and is expected to bring new developments to the refrigeration industry.

Attempts have begun to use magnetic refrigeration in low-temperature regions of several tens of degrees K or less, but in recent years, the development of superconducting magnets has made it easier to obtain strong magnetic fields, making it difficult to apply it to higher-temperature regions. Possibilities are opening up.

However, in the temperature range where the lattice specific heat of the magnetic working material acts as a large heat load, it is necessary to use a cycle that includes a homomagnetization or isomagnetic field process, which corresponds to the reverse Starling or reverse Ericsson cycle in gas refrigeration. To do so, it is necessary to use an appropriate regenerative cold storage device.

An example of such a magnetic refrigeration device is shown in FIG. 1 is a magnetic working substance having a suitable Curie point, 2 is a cold storage liquid, 3 is a heat insulating container thereof, and 4 is an electromagnet, and the heat insulating container 3 is movable up and down.
A strong magnetic field _H1 is applied by the electromagnet 4 while the work material 1 is above the cool storage liquid as shown in FIG. This process is shown in Figure 2, from A to B in the reverse Ericsson cycle.
This corresponds to a quasi-isothermal magnetization process, and heat generation occurs as the entropy S decreases due to the alignment of the magnetic moments of the atoms constituting the working material 1, but the heat is radiated by heat exchange with the cold storage liquid 2. The insulating container 3 then rises, as shown in FIG. 1b, until the working material 1 reaches its bottom. (Equimagnetic field process from B to C) When the electromagnet 4 is deenergized by stopping the energization, heat absorption occurs due to an increase in entropy due to disturbance in the arrangement of magnetic moments, and the temperature of the surrounding cool storage liquid 2 decreases.
(Quasi-isothermal process from C to D) Finally, the container 3 is slowly lowered and returns to its initial state. (Equimagnetic field process from D to E) This cycle creates a temperature gradient in the vertical direction of the cold storage liquid 2, and the temperature of the working material 1, which has returned to the state shown in Figure 1 a, rises to E, and the cycle continues from E to E. F
→ G → H → I → J → K, and the lower part of the cold storage liquid 2 is cooled.

In conventional devices such as those described above, fluids such as liquids and gases have been used as regenerators. However, as shown in Figure 1, as the working material in the regenerator moves, the regenerator fluid also moves together, resulting in an effect called "mixing of regenerator fluids" or "crowding of regenerator fluids by magnetic materials." Therefore, the cold storage effect deteriorates, and depending on the temperature range, there may be cases where there is no suitable cold storage fluid.

The present invention aims to provide a regenerator that eliminates the above-mentioned drawbacks by using a solid as a regenerator medium.

Furthermore, by arranging the solid refrigerant medium into blocks arranged at regular intervals, it is possible to cut off heat conduction between each block and to select and use a material with the largest heat capacity in the temperature range for each block.

FIG. 3 shows an embodiment of the magnetic refrigeration system of the present invention, in which the regenerator 5 is composed of an appropriate number of solid blocks 51, 5.
2, 53, 54, etc., and is filled with gas for heat exchange. Reference numeral 6 denotes a guide rod made of Teflon, which serves as a guide for the vertical movement of the magnetic working substance 1. Reference numeral 7 denotes an upper heat exchange chamber for heat dissipation, in which heat is exhausted by gas flowing back from an inlet 71 to an outlet 72.
8 is a lower heat exchange chamber, from an inlet 81 to an outlet 82.
The gas refluxing to is guided to the object to be cooled.

The operating principle of this device is the same as that of the device shown in FIG. It acts only as a heat exchange medium between the block and the magnetic working material 1, and even some mixing from above and below does not reduce the cooling effect. In addition, solid blocks 51, 52, 5
3,... are placed at regular intervals, so
Even if there is a temperature difference between adjacent blocks, heat conduction between them is blocked, and this can prevent the cold storage effect from deteriorating.

Furthermore, in general, solid specific heat rapidly decreases at low temperatures, reducing the cold storage effect of solid blocks. However, it is known that ferromagnetic materials have an abnormal specific heat near the Curie point, and each block 51, 5
By using a material having a Curie point near the operating temperature of each of No. 2, 53, ..., the heat capacity can be increased and the device can be made smaller.

Substances that can be used as an example and their Curie points
If T _c is shown, it is as follows.

Compound T _c (〓) Gd ₃ Al ₂ 282 Tb ₃ Al ₂ 180 Dy ₃ Al ₂ 74 Ho ₃ Al ₂ 33 E _r Al ₂ 25 E _u S 16 Between 280〓 and 180〓, (G _dx T _b1-x ) ₃ By changing X of Al ₂ , between 180〓 and 74〓 becomes (T _bx −
D _y1-x ) ₃ By changing X of Al ₂ , 74〓
~33〓, (D _yx H _01-x ) ₃ A solid solution having any T _c can be obtained by changing X of Al ₂ .

This magnetic refrigeration system operates similarly to the refrigeration system shown in FIG. That is, as shown in FIG.
Multiplying H ₁ generates heat as the magnetic moments align. This heat is transferred to the solid cold storage block by the gas filled in the device, but since the heat transfer through the gas increases rapidly as the heat transfer surface spacing becomes smaller, in effect, the magnetic working material 1 Heat is transferred only to the adjacent block 51. Next, either the heat insulating container 3 is raised or the magnetic working material and the electromagnet 4 are lowered, so that the magnetic working material 1
reaches the bottom of the heat insulating container 3 while sequentially exchanging heat with the blocks 52, 53, etc. When the electromagnet 4 is demagnetized here, the temperature decreases due to heat absorption due to the disordered arrangement of the magnetic moments, and the temperature of the block 54 decreases. Finally, it slowly returns to the state shown in FIG. 3, but during this time heat exchange is performed with blocks 53 and 52 in sequence. In this way, the temperature of block 51 increases and the temperature of block 54 decreases. During this time,
As mentioned above, heat exchange occurs only between the magnetic working material 1 and the blocks adjacent thereto, and heat conduction is blocked between the blocks because of the large distance between them.
Exhaust heat from the block 51 is carried out by gas recirculation in the upper heat exchange chamber 7 for heat dissipation, and cooling heat is carried out by gas reflux in the lower heat exchange chamber 8. Since these heat exchange chambers are isolated from the inside of the heat insulating container 3, the reflux of this gas does not create a gas flow inside the container.

Another embodiment is shown in FIG.
On the top, cold storage blocks 91, 92, 93, . . . are arranged in a disk shape. A magnetic field is applied to the solid block 91 at the location of the magnetic working substance 1, and the block 91 is heated. Next, the regenerator 9 rotates half a turn, and the block 9
When the electromagnet 4 is in the position of the work material 1, the electromagnet 4 is demagnetized and the block 94 is cooled. Furthermore, cold storage 9
It returns to its original state after half a rotation and completes one cycle. Cool storage device 9
may be unidirectional rotation or reciprocating and reverse rotation.

Alternatively, the magnetic working substance 1 may be arranged in a disk shape and rotated. In this case, the working material is magnetized and demagnetized by entering and exiting a constant magnetic field, so there is no need to turn on and off the electromagnet, which is advantageous for use with superconducting magnets, etc.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the operation of a conventional magnetic refrigeration system, Figure 2 is an entropy temperature diagram of a refrigeration cycle, Figure 3 is a configuration diagram of one embodiment of the refrigeration system of the present invention, and Figure 4 is a diagram of another A configuration diagram of an example. 1: Magnetic working substance, 2: Cold storage liquid, 3: Heat insulating container, 4: Electromagnet, 5: Solid regenerator, 7, 8: Heat exchange chamber, 9: Disc-shaped solid regenerator.

Claims (1)

[Claims] 1. Consisting of a magnetic working substance, a magnetic device that applies a magnetic field to the magnetic working substance, and a regenerator that exchanges heat with the magnetic working substance, the regenerator is disposed in a heat exchange medium such as gas. A magnetic refrigeration device characterized by having a solid cold storage medium provided therein. 2. The magnetic refrigeration system according to claim 1, wherein the solid regenerator medium is formed from a plurality of solid blocks spaced at regular intervals from the high temperature side to the low temperature side of the regenerator. 3. The magnetic refrigeration device according to claim 2, wherein the plurality of solid blocks are formed of materials having different Curie points depending on their operating temperatures.