JP2941865B2 - Low temperature storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a low-temperature heat storage device filled with a heat storage material.

(Prior Art) In recent years, the development of superconducting technology has been remarkable, and the development of a small-sized and high-performance refrigerator has become indispensable as its application field has expanded. Such small refrigerators are required to be lightweight, small and have high thermal efficiency.

For this reason, research has been actively conducted on a new refrigeration method (magnetic refrigeration) using a heat cycle (eg, Carnot and Ericsson) using the magnetocaloric effect instead of gas refrigeration and on improving the performance of gas refrigeration using the Stirling cycle. ing.

In order to improve the performance of a gas refrigerator by a heat cycle such as the Stirling method, it is important to improve the heat storage unit, the compression unit, and the expansion unit. In particular, the performance of the heat storage material constituting the heat storage device is greatly affected. As such a heat storage material, a material having a high specific heat even at 20 K or less, at which the specific heat of copper or lead is remarkably reduced, has been demanded, and various magnetic materials have been studied.

Further, the regenerator is often used by being incorporated into a refrigerator, for example, a device that operates a Stirling cycle,
It is used in devices that operate on the Billmeyer cycle or devices of the Gifford-McMahon type. In these devices, a compressed working medium flows unidirectionally through the regenerator and supplies its thermal energy to the filler material, where the expanded working medium flows in the opposite direction and receives thermal energy from the filler material. . In this process, as the recuperation effect becomes better, the thermal efficiency of the working medium cycle becomes better, and a lower temperature can be realized.

By the way, in the low-temperature heat storage device, the filling material is conventionally formed of lead or bronze balls or a wire mesh layer of copper or phosphor bronze. However, such packing materials have a specific heat of 20.
Since it is excessively small at extremely low temperatures of K or less, sufficient thermal energy cannot be stored in the packing material every cycle at extremely low temperatures during operation with the above-described refrigerator, and the working medium is not sufficiently separated from the packing material. Can no longer receive high thermal energy. As a result, there is a problem that a refrigerator incorporating the regenerator having the filling material cannot reach extremely low temperatures.

Therefore, in order to improve the regenerative characteristics at extremely low temperatures of the regenerator, the filling material has a maximum value of specific heat of 20K or less, and the value is sufficiently large in specific heat per unit volume (volume specific heat). R-Rh intermetallic compound (R; Sm, Gd, Tb, Dy, Ho, Er,
Tm, Yb) has been proposed (JP-A-51-523).
No. 78). However, since such a filling material uses Rh (rhodium) as one component and is extremely expensive, there is a problem in practical use as a filling material for a regenerator used on the order of several hundred grams.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and has an excellent magnetocaloric effect at an extremely low temperature such as liquid nitrogen temperature or lower, and has an excellent heat transfer. An object of the present invention is to provide a low-temperature heat storage device filled with a relatively inexpensive magnetic material having characteristics and recuperation characteristics as a heat storage material.

[Configuration of the invention]

(Means for Solving the Problems) The present invention relates to a low-temperature heat storage device filled with a heat storage material, wherein a general formula (I) AMz ... (I) (where A is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy,
At least one rare earth element selected from Ho, Er, Tm, Yb, Lu; M is selected from Ni, Co, Cu, Ag, Au, Mn, Fe, Al, Zr, Pd, B, Si, P, C At least one species, z represents 0.001 ≦ z ≦ 9.0)
A low-temperature heat storage device characterized by being filled as a heat storage material with one or two or more kinds of amorphous magnetic materials represented by the following formula:

The reason why the heat storage material is made of an amorphous magnetic material is as follows with respect to a compound magnetic material.

In order to realize a large magnetic specific heat in a cryogenic temperature range, the magnetic transition point must be lowered to the cryogenic temperature range. To that end, it is necessary to increase the rare earth concentration. However, in a compound system, for example, RMrz, there is no compound having a high rare earth concentration having a z value of less than 2, and an optimum z value range (0.
001z <2) cannot be obtained. On the other hand, in the amorphous state, the z value is arbitrary, so that a material having a high rare earth concentration can be obtained, and a magnetic material having a large magnetic specific heat in an extremely low temperature region can be obtained.

The lattice specific heat in the cryogenic temperature range is determined by the Debye temperature unique to a substance. The Debye temperature also decreases as the rare earth concentration increases, and the lattice specific heat in the cryogenic region increases accordingly. For the same reason as described above, an amorphous material having a low Debye temperature with a composition not existing as a compound can be obtained, and a magnetic material having a large lattice specific heat in an extremely low temperature region can be obtained.

By making it amorphous, a material having excellent mechanical strength can be obtained. For example, it is possible to obtain a magnetic material having high durability against impact and abrasion due to repeated pressure changes exceeding 10 atm in a gas refrigerator.

For the above reasons, it is possible to use the amorphous magnetic material according to the present invention to configure a regenerator having high heat storage characteristics and high durability.

The reason why the z value is set to 0.001 or more is to facilitate the production of amorphous.

It is desirable that the amorphous magnetic material has an average particle diameter, a fiber diameter or a thickness of 1 to 2000 μm. The reason for this is that if the average particle size or fiber diameter is less than 1 μm, when the regenerator is filled, it tends to flow out of the regenerator together with the high-pressure working medium (for example, helium gas). If the fiber diameter exceeds 2000 μm, the thermal conductivity of the amorphous magnetic material becomes a rate-determining factor for heat transfer between (magnetic material) and (working medium), and the heat transferability may be significantly reduced, leading to a decrease in the recuperative effect. Because there is. The reason for defining the upper limit of the average particle diameter or the fiber diameter will be described more specifically. In order to utilize 100% of the heat capacity of the heat storage material, a large volume specific heat (ρCp;
(p is specific heat) and high thermal conductivity is required. That is, the penetration depth (ld) that determines the effective volume of the heat storage material that contributes to heat storage is represented by ld = λ / (ρCpπf). Here, λ is the thermal conductivity, ρ is the density of the working medium, Cp is the specific heat, and πf is the refrigeration cycle. Therefore, for example, when ρCp is 6K or more, 0.
When a heat storage material such as ErNi _1/3 , which is as large as ³ J / cm ³ K, is used, ld is 600 due to its thermal conductivity (80 mW / Kcm).
Since it is about μm, it is necessary to set the upper limit of the particle diameter of the heat storage material to 1000 μm.

The amorphous magnetic material is regularly filled in the three-dimensional direction to achieve uniform heat transfer and reduced pressure loss. It is desirable to use a certain fibrous shape, a ribbon shape having a plurality of through holes having a diameter of 1 to 2000 μm and capable of passing gas in the thickness direction.

In order to produce the above-mentioned spherical magnetic material, there are a method of cooling rapidly with an inert gas or liquid after forming a molten droplet, and a method of cooling while rolling on a metal refrigerant. For example, a method of dropping a molten liquid onto a high-speed rotating disk and tearing the molten liquid into droplets by centrifugal force, or converting powder into a molten droplet by high-temperature plasma, arc discharge, high-frequency induction There is a way. Since the molten droplet becomes spherical due to surface tension and rapidly cools and solidifies as it is, when cooling rapidly with an inert gas, it is desirable to increase the cooling rate to 1 atmosphere or more.

To produce the above fibrous amorphous magnetic material,
For example, a woven fabric made of a metal fiber such as W or B, glass fiber, carbon fiber, plastic fiber, or the like is used as a core material, and vapor-phase growth such as thermal spraying or sputtering, and liquid-phase growth are performed using the general formula (I). A method of coating the expressed amorphous can be mentioned.

In order to manufacture a ribbon having the above-described through-hole, a method of mechanically or laser-punching a ribbon produced by quenching a molten metal using a rotating roll can be used.

Among the amorphous magnetic materials represented by the general formula (I), those having the following composition are preferred.

. General formula ANiz ... (II) (where A is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy,
At least one rare earth element selected from Ho, Er, Tm, and Yb, z represents 0.1 ≦ z ≦ 9.0), and has an average particle diameter or fiber diameter of 1 to 2 1000
μm amorphous magnetic material. Among such magnetic materials, those having a composition in which z is 0.1 ≦ z ≦ 2.0 are more preferable for the above-mentioned reason.

. General formula A ′ _1-X DxMz (III) (where A ′ is at least one rare earth element selected from Er, Ho, Dy, Tb, and Gd, and D is Pr, Nd, Sm, Ce) M is at least one metal selected from Ni, Co and Cu, x is 0 ≦ x <1, and z is 0.01
≦ z ≦ 9.0), and an amorphous magnetic material having an average particle diameter or a fiber diameter of 1 to 2000 μm. In the general formula (III), by using a heavy rare earth element such as Er, Ho, Dy, Tb, or Gd as A ', an alloy with M, such as Ni, can exhibit a particularly remarkable magnetic specific heat, and the maximum value of the specific heat peak Can be increased. Also, by selecting light rare earth elements such as Pr, Nd, Sm, and Ce as D to replace these heavy rare earth elements, the maximum value of the specific heat peak and the temperature width (half width) are adjusted by utilizing the Schottky anomaly and the like. It is possible to do. Furthermore, for the reasons described above, z
Those having a composition of 0.1 ≦ z <2.0 are more preferable.

Further, part of M in the general formula (I) is represented by B, Al, Ga, In, Si.
The amorphous magnetic material substituted by, for example, is shown below as general formula (IV) and general formula (V). However, among these substituted metals, Fe has a strong direct exchange effect of Fe-Fe, and if it is excessively substituted, the temperature at which the specific heat peak appears becomes 77 K or higher, which is considerably high. It is necessary to

A (M _1-y Xy) z (IV) (where A is Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,
At least one rare earth element selected from Ho, Er, Tm, Yb, M is at least one metal selected from Ni, Co and Cu, X is B, Al, Ga, In, Si, Ge, Sn, Pb , Ag, Au, Mg, Zn, Ru, Pd, P
t, Re, Cs, Ir, Fe, Mn, Cr, Cd, Hg, Os, at least one element constituting an amorphous magnetic material, y is 0 ≦ y <1.
0, preferably y ≦ 0.5, and z represents 0.001 ≦ z ≦ 9.0).

A _1−X Dx (M _1−y Xy) z (V) (where A ′ is at least one rare earth element selected from Er, Ho, Dy, Tb and Gd, and D is Pr, X is at least one element selected from Nd, Sm, and Ce, and X is B, Al, Ga, In, Si, Ge, Sn,
Pb, Ag, Au, Mg, Zn, Ru, Pd, Pt, Re, Cs, Ir, Fe, Mn, Cr, Cd, Hg, Os
X is 0 ≦ x <1, and y is 0 ≦ y ≦ 0 when X is Fe.
8, when X is other than Fe, 0 ≦ y <1.0, preferably y ≦ 0.
5, z represents 0.001 ≦ z ≦ 9.0), or an amorphous magnetic material composed of one or more kinds.

(Action) The amorphous magnetic material used in the present invention, which is composed of one or two or more kinds of rare earth elements having a high rare earth concentration represented by the general formula (I) and a transition metal represented by M such as NiCo, is 10 mW. / cmK or more, and by filling the amorphous magnetic material with a predetermined particle size or fiber diameter as a heat storage material, it can be used at extremely low temperatures such as liquid nitrogen temperature or lower (especially 40K or lower). A relatively inexpensive low-temperature regenerator exhibiting excellent lattice specific heat and magnetocaloric effect and having excellent heat transfer characteristics and recuperation characteristics can be obtained. Especially,
By setting z in the range of 0.01 ≦ z <2.0, there is an advantage that the lattice specific heat on the high temperature side of the heat storage material made of a magnetic material can be improved. In addition, such a cold storage material having a high rare earth concentration can be easily obtained.

In addition, by using an amorphous magnetic material in which the compound represented by the general formula (I) is a mixed aggregate of two or more kinds, the specific heat peak becomes broad and the heat capacity decreases, but the specific heat increases over a wider temperature range. Thus, the recuperation characteristics of the low-temperature heat storage device can be improved.

Furthermore, by stacking and filling a plurality of types of magnetic materials having different magnetic transition points (temperatures at which specific heat reaches a peak) in accordance with the temperature gradient of the low-temperature regenerator, a low-temperature regenerator with even better recuperation characteristics is obtained. be able to.

(Example) Hereinafter, an example of the present invention will be described in detail.

Examples 1-3 First, an alloy having a composition ratio of ErNi _0.4 , an alloy having a composition ratio of ErNi _1.1 , and an alloy having a composition ratio of ErNi _1.8 were each prepared using an arc melting furnace, and these alloys were mixed in a helium gas atmosphere. Three kinds of amorphous magnetic materials were produced by high-frequency melting and injection into a rotating disk. The final gas pressure reached 1.8 atm in this injection.

Observation of the obtained magnetic materials of Examples 1 to 3 with SEM photographs confirmed that the magnetic materials were spherical having an average particle diameter of 40 to 100 μm.

Further, when the volume specific heat of each of the obtained spherical amorphous magnetic materials was measured, the characteristic diagram shown in FIG. 1 was obtained. In addition,
FIG. 1 also shows the volume specific heats of Pb and Cu as comparative examples. As is apparent from FIG. 1, the spherical amorphous magnetic material as the heat storage material in Examples 1 to 3 was about
It can be seen that at very low temperatures of 15K or less, it has an excellent volume specific heat as compared with conventional thermal storage materials Pb and Cu, and has an excellent lattice specific heat at a temperature range of 15K or more. In particular, alloys having a composition in which z in the general formula (I) is in the range of 0.01 ≦ z <2.0 (Example 1; ErNi _0.4 , Example 2; ErNi _1.1 ) are superior to Pb in a temperature range of 15 K or more. It can be seen that it has a lattice specific heat.

Further, among the above-mentioned spherical amorphous magnetic materials, a spherical amorphous magnetic material having a composition ratio of ErNi _1/3 (average particle diameter of 50 to 100 μm) is used.
m) into a cold storage container made of phenolic resin (filling rate: 63
%), A GM refrigeration cycle in which helium gas having a heat capacity of 25 J / K was supplied under the conditions of a mass flow rate of 3 g / sec and a gas pressure of 16 atm was performed to measure cool storage efficiency. As a result, in the regenerator filled with a spherical magnetic material having a composition ratio of ErNi _0.4 , the same average particle size,
It was confirmed that the efficiency was improved by 8 times or more in the temperature range of 40K to 4K as compared with spherical lead (comparative example) having a filling factor.

Examples 4 to 7 First, using an arc melting furnace, an alloy having a composition ratio of DyNi _0.4 , an alloy having a composition ratio of (Er _0.5 Dy _0.5 ) Ni _0.4 , and (Er _0.75 Dy)
_0.25 ) After preparing an alloy having a composition ratio of Ni _0.4 and an alloy having a composition ratio of ErNi _0.4 , four kinds of amorphous magnetic materials were manufactured from these alloys in the same manner as in Example 1.

Observation of the obtained magnetic materials of Examples 4 to 7 with SEM photographs confirmed that they were spherical having an average particle size of 40 to 100 μm.

Further, when the volume specific heat of each of the spherical amorphous magnetic materials was measured, the characteristic diagram shown in FIG. 2 was obtained. The second
In the figure, the volume specific heat of Pb as a comparative example is also shown. As is apparent from FIG. 2, the spherical amorphous magnetic materials as the heat storage materials of Examples 4 to 7 all have excellent volume specific heat at extremely low temperatures of about 15 K or less as compared with the conventional heat storage material Pb. It can be seen that the alloy has excellent lattice specific heat in a temperature range of 15 K or more. Moreover, in the fourth to fourth embodiments.
It can be seen that, among the spherical amorphous magnetic materials of No. 7, the temperature at which the peak value of the volume specific heat is shifted to a lower temperature side as the concentration of Er which is one component of the alloy increases.

Examples 8 to 10 First, using an arc melting furnace, an alloy having a composition ratio of (Er _0.8 Pr _0.2 ) Ni _0.4 , an alloy having a composition ratio of (Er _0.7 Pr _0.3 ) Ni _0.4 and an alloy having a composition ratio of (Er _0.6 Pr _0.4 ) Ni _0.4 After preparing alloys having the respective composition ratios, three kinds of amorphous magnetic materials were produced from these alloys in the same manner as in Example 1.

The obtained amorphous magnetic materials of Examples 8 to 10 were subjected to SEM
Observation with a photograph confirmed that the particles were spherical having an average particle size of 40 to 100 μm.

Each of the spherical amorphous magnetic materials of Examples 1 to 10 was filled in a phenol resin cold storage container (filling rate: 65%).
%), A GM refrigeration cycle of supplying a helium gas having a heat capacity of 25 J / K at a mass flow rate of 3 g / sec and a gas pressure of 16 atm was performed to perform a refrigeration test. As a result, Example 1
It was confirmed that in the regenerators filled with the spherical magnetic materials of ~ 10, the lowest attained temperature in the no-load state was reduced by 1K or more as compared with spherical lead (comparative example) having the same average particle size and filling rate.

Examples 11 and 12 First, an alloy having a composition ratio of ErCo _0.4 and an alloy having a composition ratio of ErCo _0.1 were respectively prepared using an arc melting furnace, and these alloys were subjected to high-frequency melting in a helium gas atmosphere, and further to a rotating disk. By injection, two types of amorphous magnetic materials were produced. The final reached argon gas pressure in this injection was 1.8 atm.

Observation of the obtained amorphous magnetic materials of Examples 11 and 12 by SEM photograph confirmed that they were spherical with an average particle diameter of 40 to 100 μm.

After filling each spherical amorphous magnetic material into a cold storage container made of phenol resin (filling rate: 65%), helium gas with a heat capacity of 25 J / K was supplied under a condition of a mass flow rate of 3 g / sec and a gas pressure of 16 atm. The supplied GM refrigeration cycle was performed to measure the cool storage efficiency. As a result, it was confirmed that in the regenerators filled with the spherical magnetic materials of Examples 11 and 12, the efficiency was improved 7 times or more as compared with spherical lead (comparative example) having the same average particle size and the same filling ratio.

Examples 13 to 15 First, using an arc melting furnace, an alloy having a composition ratio of (Er _0.8 Nd _0.2 ) Co _0.4 , an alloy having a composition ratio of (Er _0.7 Nd _0.3 ) Co _0.4 and an alloy having a composition ratio of (Er _0.6 Nd _0.4 ) Co _0.4 After preparing alloys having the respective composition ratios, three kinds of amorphous magnetic materials were produced from these alloys in the same manner as in Example 11.

The obtained amorphous magnetic materials of Examples 13 to 15 were subjected to SEM.
Observation with a photograph confirmed that the particles were spherical having an average particle size of 40 to 100 μm.

After filling each spherical magnetic material into a phenol resin cold storage container (filling rate: 65%), helium gas with a heat capacity of 25 J / K was supplied under the conditions of a mass flow rate of 3 g / sec and a gas pressure of 16 atm. The GM refrigeration cycle was performed to measure the cold storage efficiency. As a result, in the regenerators filled with the spherical amorphous magnetic materials of Examples 13 to 15, it was confirmed that the efficiency was improved by 8 times or more as compared with spherical lead (comparative example) having the same average particle size and filling rate. .

Examples 16 and 17 First, an alloy having a composition ratio of ErCu _0.4 and an alloy having a composition ratio of ErCu _0.1 were respectively prepared using an arc melting furnace, and these alloys were subjected to high frequency melting in a helium gas atmosphere, and further to a rotating disk. By injection, two types of amorphous magnetic materials were produced. The final gas pressure in this injection was 1.8
Atmospheric pressure.

Observation of the obtained amorphous magnetic materials of Examples 16 and 17 by SEM photograph confirmed that they were spherical bodies having an average particle size of 40 to 100 μm.

After filling each spherical magnetic material into a phenol resin cold storage container (filling rate: 65%), helium gas with a heat capacity of 25 J / K was supplied under the conditions of a mass flow rate of 3 g / sec and a gas pressure of 16 atm. The GM refrigeration cycle was performed to measure the cold storage efficiency. As a result, it was confirmed that the regenerator filled with the spherical amorphous magnetic material of Examples 11 and 12 had an efficiency eight times or more higher than that of spherical lead (comparative example) having the same average particle size and filling rate. .

Examples 18-23 First, an alloy having a composition ratio of ErNi _0.4 and an alloy having a composition ratio of ErNi _0.1 using an arc melting furnace, an alloy having a composition ratio of ErCo _0.4 ,
Alloy with ErCo composition ratio, alloy with ErCu _z composition ratio and ErCu _0.1
Alloys having the following composition ratios were prepared. Next, when the fiber diameter is 10
The above alloys were sprayed onto a woven fabric of μm tungsten (W) fiber to produce six kinds of fibrous amorphous magnetic materials.

When the average fiber diameter of the obtained fibrous magnetic bodies of Examples 18 to 23 was measured, it was confirmed to be 40 to 100 μm.

After laminating and filling each of the above fibrous magnetic materials in a phenol resin cold storage container (filling rate: 75%),
A GM refrigeration cycle in which 5 J / K helium gas was supplied under the conditions of a mass flow rate of 3 g / sec and a gas pressure of 16 atm was performed, and the cool storage efficiency was measured. As a result, in the regenerator in which the fibrous magnetic materials of Examples 8 to 10 were stacked and filled, the efficiency was 10 times higher than that of a woven fabric of lead alone having the same fiber diameter and filling ratio (comparative example).
It was confirmed that it improved more than twice.

〔The invention's effect〕

As described in detail above, according to the present invention, a relatively inexpensive amorphous material having an excellent calorie effect at an extremely low temperature such as liquid nitrogen temperature or lower (especially 40K or lower), and having excellent heat transfer characteristics and recuperation characteristics. It is possible to provide a low-temperature regenerator filled with a magnetic substance as a regenerator material, and by this low-temperature regenerator
It has remarkable effects such as realizing a 4K class GM refrigerator. In particular, a regenerator material having a high concentration of rare earth can be easily obtained. In particular, by forming the amorphous magnetic material into a spherical shape having a predetermined average particle diameter or a fibrous shape having a predetermined fiber diameter, the magnetic material can be regularly filled in a three-dimensional direction, and a filling rate and heat transfer with a working medium such as helium gas can be achieved. It is possible to obtain a low-temperature regenerator with further improved characteristics and reduced pressure loss.

[Brief description of the drawings]

 1 and 2 are characteristic diagrams.

Claims (1)

(57) [Claims] In a low-temperature heat storage device filled with a heat storage material, a general formula (I) AMz... (I) (where A is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy,
At least one rare earth element selected from Ho, Er, Tm, Yb, Lu; M is selected from Ni, Co, Cu, Ag, Au, Mn, Fe, Al, Zr, Pd, B, Si, P, C At least one species, z represents 0.001 ≦ z ≦ 9.0)
A low-temperature heat storage device characterized by being filled as a heat storage material with one or two or more kinds of amorphous magnetic materials represented by the formula: