JPS61197964A - Small-sized cryogenic refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a small-sized cryogenic refrigeration system that uses magnetic refrigeration and is applicable to cryopumps, He liquefaction equipment, and the like.

[Conventional technology] Conventional compact cryogenic cooling? j! ? c21 has a piston-shaped displacer slidably fitted into the cylinder, and by reciprocating the displacer, the volume of the expansion chamber formed between the displacer and the low temperature end of the cylinder is increased or decreased. It is common that the expansion chamber expands and contracts to sequentially expand the gas to run a predetermined refrigeration cycle, but in principle such a device can pump heat of 20 to 15K. temperature limit.

Therefore, in order to realize an extremely low temperature of about the liquid helium temperature (4.2K), a combination with a freezing means that can pump heat from 4K to 20K is required.

On the other hand, recently, the use of magnetic refrigerators that utilize magnetic refrigeration materials (substances whose entropy changes depending on the strength of the magnetic field at extremely low temperatures) has been attracting attention as one type of refrigeration means that can be combined with such gas refrigerators. It is growing. In other words, in this magnetic refrigerator, when the magnetic refrigeration material is subjected to a repeating cycle of demagnetization and excitation, during demagnetization the temperature decreases due to adiabatic demagnetization and heat is absorbed as entropy increases, and during excitation the temperature decreases due to adiabatic excitation. It can act as a heat pump, dissipating heat as the entropy decreases as the temperature increases, and research by JLT has demonstrated that it can be used to pump heat from If 4 K to 20°C.

However, when using such a magnetic refrigerator,
It is necessary to intermittently perform thermal connection at predetermined timings between this magnetic refrigerator, which pumps heat from a level of 4 to 20 degrees, and a gas refrigerator, which pumps heat from 20K to room temperature.

In other words, when the temperature of the magnetic refrigeration material increases due to adiabatic excitation, heat is transferred from the magnetic refrigerator to the cold head side of the gas refrigerator, while when the temperature of the magnetic refrigeration material decreases due to adiabatic demagnetization, heat is transferred from the high temperature side to the magnetic refrigeration material. It is necessary to switch the thermal connection between the two to cut off the inflow of the He gas.Currently, the specific means for this purpose is to use He as a heat transfer medium and to transfer the condensation heat of the He gas and the heat transfer between the He gas thin layer. It was devised to realize a thermal switch by the difference in the
(Refer to Publication No. 184471) However, in such a product, the heat switch mechanism is complicated and refrigeration is difficult. : Not only does this lead to an increase in the size of the equipment, but the switch operation is not reliable, and it is expected that there will be a large amount of heat intrusion into the magnetic refrigeration material from the high temperature side, which will reduce the efficiency of the magnetic refrigerator. There is a problem of deterioration.

At the same time, a small gas refrigerator operated by Solvay Cycle etc. may be used as a means to pump the heat pumped out by the two-magnetic refrigerator from the 20°C level to room temperature.
This type of fist had the problem of not being able to pump out a sufficient amount of heat at a level of 20 [Problems to be solved by the invention] The present invention was made by focusing on the following problems. H by combining a gas refrigerator and a magnetic refrigerator.
e A compact cryogenic refrigeration system capable of realizing cryogenic temperatures below the liquefaction temperature that can simultaneously solve the above problems, that is, turn on and off the thermal switch reliably at the required timing; The aim is to provide a new product with a sufficiently large ability to pump out heat from the 20 level.

[Means for solving problems] The present invention aims to achieve such an objective.

A magnetic refrigeration material was installed inside the first dewar, and this Fi
i A magnetic refrigerator with variable magnetic field means for periodically excitation and demagnetization of a gas refrigerating material, and a gas-liquid two-phase flow of the working gas by freely expanding hydrogen, neon, or nerium gas with a Joule-Thomson valve. a gas refrigerator configured to inject gas into a second deyuwa connected to the first deyuwa; a partition wall between the first deyuwa and the second deyuwa is formed of the magnetic refrigeration material; The present invention is characterized in that the Joule-Thompson valve is opened for each excitation cycle to intermittently inject the gas-liquid two-phase flow into the magnetic and pneumatic refrigerating material.

[Effect]

With this configuration, when the magnetic refrigerant is adiabatically excited and the temperature rises, the 51% refrigerant will have H? , a gas-liquid two-phase flow of Ne or Ne-He mixed gas can be injected, and the vaporization heat transfer of the liquefied working gas is much greater than the heat transfer of gas. The machine will be thermally connected to the machine. Therefore, with this device, it is possible to realize a thermal switch that can reliably turn on and off the heat wave at a predetermined timing according to the excitation/demagnetization cycle of the magnetic refrigeration material. It is possible to significantly reduce heat intrusion from the inside. By using this magnetic refrigeration material, the W
The heat pumped out to the S2 dewar is pumped out to the room temperature side by a gas cycle in which the vaporized gas in the second deyuwa is circulated by VA and a gas-liquid two-phase flow is intermittently injected from the Joule-Thompson valve.

If there is a gas refrigerator in which such a two-phase flow after free expansion is directly injected with magnetic refrigeration material, it will be possible to significantly increase the ability to pump out heat from a small size, even at a level of 20. .

[Example〕 An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 are diagrams showing a schematic configuration of a small cryogenic refrigerator used for reliquefaction of helium using neon gas as the working gas, in which a magnetic refrigerator 1 is placed on the lower cryogenic side, and a magnetic refrigerator 1 is placed on the upper cryogenic side. It is constructed by disposing a gas refrigerator 2 on the room temperature side.

81 air frozen $! 11 is a magnetic refrigerating material 3 made of, for example, GG (Gallium◆Garnet), which is installed in the first dewar 5 that stores liquid helium 4, and a variable magnetic field that periodically excites and demagnetizes the magnetic refrigerating material 3. It is provided with means 6. That is, in this case, the magnetic field variable means 6 is a movable means that reciprocates the superconducting magnet 7 positioned and held above the liquid level in the first dewar 5 and the magnetic refrigerating material 3 set at the center of the magnet 7 up and down. 8.

Specifically, the strength of the &i field applied to the magnetic refrigeration material 3 can be varied by moving the magnetic refrigeration material 3 in and out of the magnetic field created by the magnet 7, and the magnetic refrigeration material is When it descends, it is demagnetized, and conversely, when it rises close to the magnet 7, it becomes excited. The movable means 8 for reciprocating the magnetic refrigeration material 3 is provided with a piston rod that hangs down from the room temperature side above, and the magnetic refrigeration material 3 is attached to the lower end of the piston rod 8 at its upper surface 3a. There is. The piston rod 8 is lowered by a crank mechanism (not shown) to a position in close proximity to the liquid level below when the magnetic refrigerating material 3 at its lower end is at the top dead center, and is positioned just at the bottom when the piston rod 8 is at the bottom dead center. It is advanced and retreated so that it rises to the height position of the magnet 7.

The gas refrigerator 2 also includes an 'S2 dewar 9 that is in contact with the upper part of the first deyuwa 5, and a compressor 11 in the second deyuwa 9. Ne gas is fed under pressure through a Joule-Thompson valve 12. an air supply system path 13 for supplying;
The Ne gas in this second dewar 9 is removed from the comb ref 11.
an exhaust system line 14 for sucking and circulating the gas, and heat exchangers 15, 18, and 17 of an appropriate number of stages for transferring the cold heat of the gas passing through the exhaust system line 14 to the gas passing through the supply air system line 13. and an expansion turbine 18 which introduces a part of the gas passing through the air supply system passage 13, cools it by adiabatic expansion, and returns it to the exhaust system passage 14, and connects the gas from the compressor 11 to the heat exchanger IS.
, 16 and 17, and is finally allowed to freely expand in the Joule-Thompson valve 12, the tip nozzle 1 of the injection pipe 19 provided in the second dewar 9
A gas-liquid two-phase flow GL containing the liquefied mist in Ne gas is injected from 9a.

Therefore, the first deyuwa 5 of the Fii air refrigerator 1 and the second deyuwa 9 of the gas refrigerator 2 connected thereto are as follows:
The magnetic refrigeration material 3 is used as a partition wall that directly partitions both chambers, and its lower surface 3b faces into the first dew 5, while its upper surface 3a faces the piston, which is attached to the second dew upper surface 3a. The rod 8 is passed through the center of the second dewar 9 and extends upward in an airtight manner, and the second deyuwa 9 suspends the magnetic refrigeration material 3 and is accommodated in the first deyuwa 5.
A bellows 20 that can be expanded and contracted while keeping a part of the peripheral wall airtight.
I try to form it with Also, the injection pipe 19 provided in the second deyuwa 9 is made to face the upper surface 3a of the magnetic refrigeration material 3 forming the bottom wall of the second deyuwa 9, and the piston rod 8 reaches the bottom dead center. When the magnetic refrigeration material 3 at the lower end rises to the position of the magnet 7, its tip nozzle 19a is brought close to the magnetic refrigeration material 3 at a predetermined distance, and at this time, the Joule φ Thomson valve 12 is opened. The configuration is such that a gas-liquid two-phase flow GL of Ne is injected from the nozzle 19a onto the upper surface 3a of the magnetic refrigeration material 3. Note that the Joule-Thompson valve 12 is opened and closed at 0 N- in synchronization with the forward and backward displacement of the piston rod 8, etc.
This can be done automatically using a valve drive device that is turned off.

Note that 21 in Figure 1 is a vacuum chamber for insulating the low temperature part of this refrigeration system.

Next, the operation of this refrigeration system will be explained.

As shown in FIG. 1, after the magnetic refrigeration material 3 receives the injection of the gas-liquid two-phase flow GL onto its upper surface 3a, the magnetic refrigeration material 3 descends into the first dewar 5 together with the piston rod 8. During the cycle, the magnetic refrigerating material 3 is demagnetized as it leaves the magnetic field of the magnet 7, but at this time both surfaces 3a and 3b of the magnetic refrigerating material 3 are brought into contact with vaporized gas. Therefore, the heat transfer with these gases is negligible and small, so the magnetic refrigerating material 3 first undergoes adiabatic demagnetization to lower its temperature. Then, when the temperature of the magnetic refrigeration material 3 falls to the level 4 in the vS1 dewar 5, the He gas surrounding it is liquefied on its lower surface 3b.
Due to the large heat transfer accompanying this liquefaction, the magnetic refrigeration material 3 is thermally connected to the He gas in the first dewar and can effectively pump up heat. At this time, the upper surface 3 of the magnetic refrigeration material 3
Thermal connection on the a side is broken due to heat transfer with the Ne gas.

Next, in a cycle in which the magnetic refrigerating material 3 rises together with the piston rod 8 from the state shown in FIG.
The &i magnetic refrigeration material enters the magnetic field of the magnet 7 and becomes excited, but at this time, since both surfaces 3a and 3b of the magnetic refrigeration material 3 are also in contact with vaporized gas, the magnetic refrigeration material first The material 3 is adiabatically excited and its temperature increases. Then, at the same time that the magnetic refrigeration material 3 reaches its bottom dead center and the temperature rises to the level 20 in the second deyuwa 9, the Joule Φ Thomson valve 12 is turned on and Ne is discharged from the nozzle 19a in the second deyuwa 9. Since the gas-liquid two-phase flow GL is injected onto the upper surface 3a of the magnetic refrigerant 3, at this time Ne
Magnetic refrigerating material 3 due to large heat transfer due to vaporization of mist
is thermally connected to the two-phase flow of Ne in the second dewar 9 and effectively dissipates heat. At this time, the lower surface 3b side of the magnetic refrigeration material 3 is thermally disconnected due to heat transfer with the He gas.

Therefore, if it is like this, it is essentially 51
At a predetermined timing, the air refrigeration material 3 is thermally connected to the He gas only when it is adiabatically demagnetized and cooled down, and is thermally connected to the Ne gas-liquid two-phase flow only when it is adiabatically excited and heated up. A thermal switch that can reliably perform 0N-OF-F can be realized, which can significantly reduce heat intrusion from the high temperature side into the magnetic refrigeration material, and improve the performance of the magnetic refrigeration machine. . The heat pumped from the first deyuwa 5 to the second deyuwa 9 by the magnetic refrigeration material 3 is
Gas-liquid two-phase by circulating the vaporized gas in the second dewar 9 and passing through the Joule-Thompson valve 12? The fiGL is pumped out to the room temperature side by a gas cycle that intermittently injects it, and the two-phase flow GL after free expansion is directly transferred to the air refrigeration material 3.
Even if the gas refrigerator 2 is small in size, it is possible to significantly increase the ability to pump out heat from a level of 20. For this reason, although this refrigeration system is small and has a simple structure, it can
The ability to pump out heat from 20 to 20 degrees to room temperature is large, and the overall capacity is large.

It is possible to significantly improve the refrigeration capacity of a small-sized He liquefaction device.

Although one embodiment has been described above, the small-sized cryogenic refrigeration apparatus of the present invention is not limited to this, but can be modified and implemented in various ways. To give an example of this, first of all, the magnetic refrigeration material used in the great invention is not necessarily limited to the above-mentioned GdG, but in other words, it can be any material whose entropy changes at extremely low temperatures depending on the strength of the magnetic field, etc. It is expected that it will be widely used. In addition, in the embodiment, a means for fixing a superconducting magnet and relatively moving the magnetic refrigerating material was adopted as the magnetic variable means, but 1. This can be done by moving the magnet in the opposite direction, or by changing the coil current of an electromagnet that does not move relative to the 8i air refrigeration material to 0N-OFFt.
The configuration of the gas refrigerator used in the present invention also depends on the type and number of stages of the heat exchanger and expander, and the configuration of the gas flow path system. It is possible to make various modifications as necessary.

In the present invention, it is preferable to store liquefied helium in the first dewar 5, which corresponds to the cryogenic part, as in the embodiment. In addition to neon in the embodiment, hydrogen gas or nerium gas, which is a combination of neon and helium, may be used as the working gas injected to the magnetic refrigeration material as a two-phase flow.

In addition, when using a turbo type compressor to send high-pressure gas to the Joule Thomson valve, if Ne gas is used as the working gas, the comb reflux will be lower than when using He gas due to the difference in its molecular structure. The rotational speed of the grass can be set to 172.5, and the stress on the χ wheel can be reduced, so there is an advantage that the structure can be made simpler.

(Effects of the Invention) Since the present invention has one or more configurations, it is possible to use a magnetic refrigerator that can be applied to helium liquefaction, etc., so that the magnetic refrigerator changes from a low temperature level to a high temperature level. The heat switch required to pump heat effectively has a reliable ON-OFF function, which makes it possible to increase the efficiency of pumping heat from level 4. At the same time, the ability to pump out heat from the level was also increased to 20, making it possible to provide a compact cryogenic refrigeration system that was small overall and had a simple structure, but with significantly improved refrigeration capacity. be.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a cross-sectional view showing the schematic configuration of the refrigeration system according to the present invention, and FIG. It is a sectional view of the same part. 1 fist...magnetic refrigerator 2...gas cold 7! II machine 3...-Magnetic refrigeration material 3 A 1111 I upper surface, 3bφ-lower surface 4--
Temperature liquid helium 511-・1st deyuwa 6・1111 magnetic variable means 7・e・magnet 8・・Φ piston rod (movable means) 9 s s *2nd deyuwa 12・ya・Joule-Thomson valve 13・・supply Air system path 14...Exhaust system path 19...
・Injection pipe 19a Yuichi-nozzle 2011 ・Bellows GL・φ gas-liquid two-phase flow

Claims (1)

[Claims] A magnetic refrigerator is provided with a magnetic refrigeration material installed in a first dewar and a variable magnetic field means for periodically excitation and demagnetization of the magnetic refrigeration material, and hydrogen, neon, or nerium gas is freely expanded using a Joule-Thomson valve. a gas refrigerator configured to inject a gas-liquid two-phase flow of the working gas of the lever into a second dewar connected to the first dewar;
The dewar and the partition wall of the second dewar are formed of the magnetic refrigeration material, and the Joule-Thompson valve is opened every excitation cycle of the magnetic refrigeration material to intermittently apply the gas-liquid two-phase flow to the magnetic refrigeration material. A small cryogenic refrigeration device characterized by being designed to inject water into the air.