JP2022108091A - Magnetic heat exchange material, heat exchange device, and magnetic heat exchange device including the same - Google Patents

Abstract

To provide a magnetic heat exchange material that has high magnetic heat exchange properties and also has high mechanical strength and practical corrosion resistance.SOLUTION: A magnetic heat exchange material has a main phase having NaZn13 type crystal structure, represented by general formula (1) or (2): La1-aRa(Fe1-b-cSibTc)eHf (1) La1-aRa(Fe1-b-cSibTcCod )eHf (2), which have common definitions: R denotes at least one selected from Sm and Y, T denotes at least one selected from V, Cr, Mn, Ni and Cu, the subscripts a, b, c, e and f satisfy 0<a≤0.30, 0.09≤b≤0.14, 12.5≤e≤13.5, and 1.3≤f≤2.3, and the formula (1) satisfies 0<c≤0.04 and formula (2) satisfies 0<c≤0.05, 0<d≤0.03.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a magnetic heat exchange material that has a large magnetocaloric effect and is suitable for practical use in a room temperature range, a heat exchange device equipped with the same, and a magnetic heat exchange apparatus using the same.

Most of the refrigeration technologies in the room temperature range, which are closely related to daily life, such as refrigerators, freezers, and indoor air conditioners, use a gas compression-expansion cycle. However, refrigeration technology based on a gas compression-expansion cycle poses a major problem of environmental destruction due to the release of specific CFCs into the environment. Against this background, efforts are being made to use natural refrigerants (CO ₂ , ammonia, etc.) and isobutane, which have low environmental risks. In other words, there is a demand for practical use of a safe, clean, and highly efficient refrigeration technology that does not have the problem of environmental destruction associated with the disposal of working gas.

As one of such environment-friendly and highly efficient refrigeration technologies, expectations are rising for magnetic refrigeration, and research and development of magnetic refrigeration technology targeting the room temperature range is progressing. Magnetic refrigeration technology is based on the magnetocaloric effect of Fe. The magnetocaloric effect is a phenomenon in which the temperature of a magnetic substance changes when an externally applied magnetic field is changed to the magnetic substance in an adiabatic state. Refrigeration systems using paramagnetic salts and compounds typified by Gd ₂ (SO ₄ ) _{3.8H 2} O and Gd ₃ Ga ₅ O ₁₂ having magnetocaloric effects have been developed. However, these are mainly applied to the cryogenic region of 20 K or less, and a magnetic field of about 10 T by a superconducting magnet was required.

Since then, many studies have been conducted to realize magnetic refrigeration in the high-temperature region using magnetic transitions between paramagnetic and ferromagnetic states in ferromagnetic materials. As a result, lanthanum series rare earth elements such as Pr, Nd, Dy, Er, Tm and Gd, two or more rare earth alloy materials such as Gd--Y and Gd--Dy, RAl ₂ and RNi ₂ (R: magnetic materials such as rare earth elements) and rare earth intermetallic compounds such as GdPd.

In 1982, Barclay of the United States proposed the AMR ("Active Magnetic Regenerative Refrigeration") method, in which the magnetic refrigeration material has a heat storage effect in addition to the magnetocaloric effect. (Patent Document 1). This AMR method is intended to positively utilize the lattice entropy, which has conventionally been regarded as an impediment to magnetic refrigeration in the room temperature range.

Magnetic refrigeration by the AMR method is performed in the following steps.
(1) Applying a magnetic field to the magnetic refrigeration working material.
(2) The heat generated in (1) is transported from one end to the other by the refrigerant.
(3) removing the magnetic field of the magnetic refrigeration working material;
(4) The cold energy generated in (3) is transported to the end opposite to the one where the heat was transported in (2).
By repeating the heat cycle of (1) to (4), the heat generated by the magnetic refrigeration material is transported in one direction through the heat transport medium in the heat exchange device (inside the magnetic refrigeration work chamber). , a temperature gradient is generated in the direction of heat flow, and a large temperature difference is generated at both ends to perform the refrigeration operation.

After that, by using Gd (gadolinium) as a magnetic refrigeration material in the room temperature range and applying a high magnetic field of up to 5 T by a superconducting magnet to the magnetic refrigerator using the AMR method, the magnetic refrigeration cycle can be continuously operated. Reported.

On the other hand, other than Gd, materials for magnetic refrigeration in the room temperature range have been developed. For example, magnetic materials such as (Hf, Ta) Fe ₂ , (Ti, Sc) Fe ₂ , (Nb, Mo) Fe ₂ and La(Fe, Si) ₁₃ systems exhibit a large magnetic entropy change and are inexpensive. It is characterized by having Fe as the main constituent element and having a small hysteresis during temperature rise and fall of the magnetic phase transition, and has been developed.

In a magnetic refrigerator using such a magnetic refrigeration material, a low temperature is generated by applying the magnetocaloric effect of the magnetic refrigeration material. For example, in a ferromagnetic material, the entropy change when the electron magnetic spin undergoes a magnetic phase transition from the paramagnetic state to the ferromagnetic state by applying an external magnetic field in the vicinity of the ferromagnetic phase transition temperature (Curie temperature; Tc) is used to achieve low temperature.

Among such magnetic materials, La(Fe _1-x Si _x ) ₁₃ having a NaZn ₁₃ -type crystal structure, which is formed by partially substituting Fe with Si, exhibits a particularly large amount of magnetic entropy change. I know In the substance having this crystal structure, Fe mainly enters the sites corresponding to Zn, and rare earth elements such as La mainly enter the sites corresponding to Na.

In order to apply magnetic materials to magnetic refrigeration such as the AMR system, it is necessary to process them into small pieces such as spherical particles that are practical for heat exchange. For example, Patent Literature 2 discloses a technique of hydrotreating a spheroidized La(Fe _1-x Si _x ) ₁₃ alloy to improve the Curie temperature.

U.S. Pat. No. 4,332,135 JP-A-2003-96547

However, the above conventional technology has the following problems. In the technique disclosed in Patent Literature 2, during hydrogenation, the lattice expands due to hydrogen entering between the lattices, and cracks may occur in some cases. Therefore, the La(Fe _1-x Si _x ) ₁₃ -based magnetic material particles in such a state were charged into the heat exchange device of the magnetic refrigeration apparatus, and heat exchange with the refrigerant was attempted to achieve refrigeration. In this case, the magnetic material particles may vibrate in accordance with the frequency of the flow of the refrigerant and the application and removal of the flow of the refrigerant and the application of the magnetic field during heat exchange.

If such a state continues for a relatively long time, the magnetic materials will collide and friction with each other due to the vibration described above, and fine powder will be generated as a result of destruction of the magnetic materials. The generation of fine powder causes a decrease in refrigerating capacity due to a decrease in efficiency of heat exchange, such as an increase in pressure loss of the refrigerant.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a magnetic heat exchange material having both magnetic heat exchange properties including a high magnetic refrigeration effect and durability, that is, crack resistance and corrosion resistance. Also provided is a heat exchange device equipped with the magnetic heat exchange material and a magnetic heat exchange apparatus using the same.

In order to achieve the above object, as a result of intensive research on the magnetic material used for the magnetic heat exchange material to have both magnetic heat exchange characteristics including high magnetic refrigeration effect and durability, we found that at least rare earth elements, iron, The inventors have found that a material containing silicon and hydrogen achieves high magnetic heat exchange characteristics and durability, leading to the development of the present invention.

That is, the magnetic heat exchange material according to the present invention developed to solve the above problems and achieve the above objects is a magnetic heat exchange material having a NaZn ₁₃ -type crystal structure as a main phase, and is represented by the following general formula (1 ) is characterized by being represented by the formula:
La _1-a R _a (Fe _1-b-c Si _b T _c ) _e H _f (1)
Here, R in the above formula (1): at least one selected from Sm and Y,
T: at least one selected from V, Cr, Mn, Ni and Cu;
Subscripts a, b, c, e and f are
0<a≦0.30,
0.09≦b≦0.14,
0<c≦0.04,
12.5≦e≦13.5,
1.3≤f≤2.3
satisfy the conditions of

Further, a magnetic heat exchange material according to the present invention developed to solve the above problems and achieve the above objects is a magnetic heat exchange material having a NaZn ₁₃ -type crystal structure as a main phase, and is represented by the following general formula (2 ) is characterized by being represented by the formula:
La _1-a R _a (Fe _1-bc Si _{b Tc} Co _d ) _e H _f (2)
Here, R in the above formula (2): at least one selected from Sm and Y,
T: at least one selected from V, Cr, Mn, Ni and Cu;
Subscripts a, b, c, d, e and f are
0<a≦0.30,
0.09≦b≦0.14,
0<c≦0.05,
0<d≦0.03,
12.5≦e≦13.5,
1.3≤f≤2.3
satisfy the conditions of

In addition, the magnetic heat exchange material according to the present invention is
(a) X-ray diffraction measurement using a Cu—Kα ray as an X-ray source shows the relationship between the diffraction line intensity of the phase (422) plane of La(Fe _1-x Si _x ) ₁₃ having a NaZn ₁₃ -type crystal structure and the Fe phase The ratio of the diffraction line intensity of the (110) plane of is 7% or less,
(b) In X-ray diffraction measurement using Cu—Kα rays as the X-ray source, the diffraction line intensity of the phase (422) plane of La(Fe _1-x Si _x ) ₁₃ having a NaZn ₁₃ type crystal structure is compared with the CeFeSi type The ratio of the diffraction line intensity of the (101) plane of the LaFeSi phase having a crystal structure is 7% or less,
(c) the magnetic heat exchange material is spherical particles having an aspect ratio of 2 or less;
(d) the magnetic heat exchange material has an average particle size of 0.05 mm or more and 1 mm or less;
etc. is considered to be a more preferable solution.

Further, a heat exchange device according to the present invention, which has been developed to solve the above problems and achieve the above objects, is equipped with any one of the above magnetic heat exchange materials.

Further, a magnetic heat exchange apparatus according to the present invention, which has been developed to solve the above problems and achieve the above objects, is characterized by comprising the above heat exchange device.

As described above, according to the present invention, it is possible to provide a magnetic heat exchange material that exhibits high magnetic heat exchange properties, high mechanical strength, and practical corrosion resistance. Moreover, by using the magnetic heat exchange material of the present invention, it is possible to provide a practically suitable heat exchange device with high heat exchange efficiency and a highly efficient magnetic heat exchange apparatus using the same.

1 is a cross-sectional view showing an embodiment of a magnetic heat exchange device using a magnetic heat exchange material according to the present invention; FIG. It is a sectional view showing an outline of operation of a magnetic heat exchange device to the above-mentioned embodiment. FIG. 4 is a conceptual diagram showing another embodiment of a magnetic heat exchange device using the magnetic heat exchange material according to the present invention; It is a detailed view of the magnetic heat exchange unit according to the other embodiment. It is a graph which shows an example of the X-ray-diffraction measurement result of the magnetic heat exchange material concerning this invention.

Other features and advantages of the present invention will be described below based on the embodiments.

The magnetic heat exchange material of the present invention is a magnetic heat exchange material whose main phase has a NaZn ₁₃ -type crystal structure, and is represented by the following general formula (1).
La _1-a R _a (Fe _1-b-c Si _b T _c ) _e H _f (1)
Here, R in the above formula (1): at least one selected from Sm and Y,
T: at least one selected from V, Cr, Mn, Ni and Cu;
Subscripts a, b, c, e and f are
0<a≦0.30,
0.09≦b≦0.14,
0<c≦0.04,
12.5≦e≦13.5,
1.3≤f≤2.3
satisfy the conditions of

Further, the magnetic heat exchange material of the present invention is a magnetic heat exchange material whose main phase has a NaZn ₁₃ -type crystal structure, and is represented by the following general formula (2).
La _1-a R _a (Fe _1-bc Si _{b Tc} Co _d ) _e H _f (2)
Here, R in the above formula (2): at least one selected from Sm and Y,
T: at least one selected from V, Cr, Mn, Ni and Cu;
Subscripts a, b, c, d, e and f are
0<a≦0.30,
0.09≦b≦0.14,
0<c≦0.05,
0<d≦0.03,
12.5≦e≦13.5,
1.3≤f≤2.3
satisfy the conditions of

The reasons for limiting the component compositions of the magnetic heat exchange materials represented by the general formulas (1) and (2) of the present invention will be described below.

R: R is a rare earth element that substitutes for La and is at least one selected from Sm and Y; Further, the atomic ratio a to the sum of R and La is in the range of more than 0 and 0.30 or less. The magnetic heat exchange material used in the present invention has a NaZn ₁₃ -type structure as a main phase, and contains rare earth elements as elements at the Na site. The rare earth element is based on La, but by partially substituting it with at least one selected from Sm and Y, the durability is improved. Therefore, it is effective in improving the reliability when it is actually mounted on a heat exchange device, for example, a refrigerator and put into operation. The amount replaces at least part of La with these elements, and the upper limit is 0.30. When the substitution ratio a exceeds 0.30, phases other than the NaZn ₁₃ -type crystal structure, such as the α-Fe phase and the R-Fe phase, tend to form, resulting in a reduced magnetocaloric effect. Preferably, it is 0.25 or less. Although Pr and Nd as rare earth elements are not actively used, they may be contained at the level of unavoidable impurities.

Si: Si is an essential element for substituting Fe to stably form a NaZn ₁₃ -type structure, and provides a large magnetocaloric effect. The atomic ratio b of Si substituting Fe is in the range of 0.09 or more and 0.14 or less. If the substitution ratio b is less than 0.09, it becomes difficult to form a NaZn ₁₃ -type structure, making it difficult to obtain a large magnetocaloric effect. On the other hand, when it exceeds 0.14, although the NaZn ₁₃ -type structure is maintained, the magnetocaloric effect is reduced, making it impractical. Preferably, it is in the range of 0.10 or more and 0.13 or less. Note that part of Si can be replaced with Al up to 1/2 in atomic ratio.

T: T is a transition metal element that replaces Fe and is effective in controlling the magnetic transition temperature, and is at least one selected from V, Cr, Mn, Ni and Cu. In addition, depending on the element, an effect of improving corrosion resistance can also be obtained. The atomic ratio c of T that replaces Fe is in the range of more than 0 and 0.04 or less in the case of formula (1) that does not use Co, and in the case of formula (2) that uses Co, it is more than 0 and 0.05 or less. be. If the substitution ratio c exceeds the upper limit, the magnetic transition temperature may become too low. Preferably, it is 0.03 or less.

Co: Co is a transition metal element that is used in the formula (2) to replace Fe and is effective in controlling the magnetic transition temperature, especially setting it to a high temperature. The atomic ratio d of Co substituting Fe is in the range of more than 0 and 0.03 or less. If the upper limit is exceeded, the contribution of the second-order phase transition becomes large, and the magnetocaloric effect may start to decrease and the magnetic transition temperature may become too high. Preferably, it is in the range of 0.005 or more and 0.025 or less. In addition, the presence of Co makes it relatively easy to introduce hydrogen, and is an effective element from this point of view as well.

Atomic ratio e between the rare earth element and the transition metal element: The atomic ratio e between the rare earth element and the transition metal element is 12.5 or more and 13.5 or less. Within this range, the NaZn ₁₃ structure is stably obtained. Below the lower limit, the ThMn ₁₂ structure, the Th ₂ Zn ₁₇ structure, etc. are likely to form, and the number of phases that do not contribute to the magnetocaloric effect increases, making it impossible to obtain sufficient heat exchange efficiency. On the other hand, when the upper limit is exceeded, the Fe phase generated before the heat treatment is less likely to disappear, making it difficult to form a single NaZn ₁₃ phase, resulting in a decrease in the magnetocaloric effect. It is preferably in the range of 12.6 or more and 13.4 or less.

H: H (hydrogen) is an element effective in controlling the magnetic transition temperature to be near room temperature and increasing the magnetocaloric effect. When the atomic ratio f of H to the sum of rare earth elements is in the range of 1.3 or more and 2.3 or less, the magnetic transition temperature becomes appropriate. Preferably, it is in the range of 1.5 or more and 2.2 or less.

Since the magnetic heat exchange material of the present embodiment has little temperature hysteresis due to the magnetocaloric effect, it can stably operate even when used as a material constituting a heat exchange cycle as a magnetic heat exchange device. In addition, since the main component is Fe, the production cost is significantly lower than that of conventional magnetic heat exchange materials, and it can be widely used.

Moreover, the shape of the magnetic heat exchange material is preferably spherical particles, for example. Here, the term “spherical” includes not only true spheres, but also substantially spherical shapes such as elliptical shapes, and those having irregularities on their surfaces. Such a shape can prevent generation of fine powder due to breakage of particles, suppress an increase in pressure loss of the heat exchange medium, and maintain heat exchange efficiency. Specifically, 80% by mass or more of the magnetic heat exchange material preferably has an aspect ratio (ratio of major axis to minor axis) of 2 or less. Experiments were carried out by mixing deformed particles with an aspect ratio of 2 or more in almost spherical particles, and when the mixed amount of deformed particles was 20% or more, exposure to the flow of the heat exchange medium for a long period of time resulted in This is because fine powder is generated and the pressure loss of the heat exchange medium increases.

In order to use the above magnetic heat exchange material in a magnetic heat exchange device as shown below and achieve a high heat exchange capacity, the magnetic heat exchange material and the heat exchange medium filled inside the heat exchange device must be: It is important that the heat exchange is sufficiently performed. For that purpose, it is preferable to increase the specific surface area of the magnetic heat exchange material. In order to increase the specific surface area of the magnetic heat exchange material, it is effective to granulate the magnetic heat exchange material and set the particle size to be small. On the other hand, if the particle size is too small, the pressure loss of the heat exchange medium increases. In addition, conditions such as the viscosity (surface tension) of the heat exchange medium, the capacity and pressure loss of the pump provided in the magnetic heat exchange device, and the size of the heat exchange device also affect the selection of the particle size of the magnetic heat exchange material. . In consideration of these points, the volume average particle diameter (major diameter) is preferably in the range of 0.05 mm or more and 1 mm or less, more preferably 0.08 mm or more and 0.8 mm or less.

The magnetic heat exchange material of this embodiment can be obtained using a generally known method. Specifically, it can be obtained by preparing an alloy by an arc melting method, a casting method, or the like, and heat-treating the alloy. Furthermore, by using an alloy preparation method with a high cooling rate such as a roll quenching method or an atomizing method, the heat treatment time can be greatly shortened, and the material can be made into thin strips or spheroids.

For example, a magnetic heat exchange material can be produced by the following method.
First, the ratio of each constituent element as a raw material is blended within a predetermined range and homogenized by melting. The types and compounding ratios of the raw materials are determined in consideration of the composition ratio (the content of each element) of the target magnetic heat exchange material.

Next, these materials are melted in a high-frequency induction furnace under an inert atmosphere and then cast into a master alloy. At this point, a large amount of Fe phase, a small amount of LaFeSi phase, and La(Fe _1-x Si _x ) ₁₃ phase are included, and heat treatment is performed at 1000 to 1300° C. for 100 to 500 hours in an inert atmosphere, Almost single-phase La(Fe _1-x Si _x ) ₁₃ (NaZn ₁₃ -type crystal structure) can be obtained.

On the other hand, by controlling the cooling rate after melting, the single phase time can be shortened. Specifically, by cooling by a roll quenching method or an atomizing method, the structure can be refined, and the time for single phase formation by the subsequent heat treatment can be greatly shortened. For example, at 1100 to 1300° C. for about 5 to 24 hours, a single phase can be obtained.

_In addition, before the heat treatment, the Fe phase was the most abundant constituent phase, and the _{LaFeSi phase} was also present. and the LaFeSi phase remain. _{The amount of Fe} The ratio of the diffraction line intensity of the (110) plane of the phase is preferably 7% or less, and the ratio of the diffraction line intensity of the (101) plane of the LaFeSi phase having the CeFeSi type crystal structure is preferably 7% or less. . In either case, if the upper limit is exceeded, the magnetocaloric effect is lowered. The remainder is the La(Fe _1-x Si _x ) ₁₃ phase of the NaZn ₁₃ -type crystal structure, which is the main phase, and contains other phases of unavoidable impurity levels that do not affect the magnetocaloric effect.

When a magnetic heat exchange material is installed in a heat exchange device and heat is exchanged with a liquid heat exchange medium, if the volume average particle diameter is 50 μm or less, pressure loss increases and heat exchange efficiency decreases. On the other hand, if the volume average particle diameter exceeds 1 mm, the pressure loss will be small, but the surface area of the magnetic heat exchange material will be reduced, so the heat exchange field will be reduced and the heat exchange efficiency will tend to decrease. From the viewpoint of pressure loss, the magnetic heat exchange material preferably has a shape of spherical particles having an aspect ratio (ratio of major axis to minor axis) of 2 or less. As the manufacturing method thereof, there is no particular limitation on the process, such as a gas atomization method, a rotating disk method, and a rotating electrode method.

In particular, when the gas atomization method is used, spherical powder can be produced. A suitable structure is obtained.

On the other hand, a similar fine structure can be obtained by the roll quenching method, and a single phase can be obtained relatively easily. When actually used as a heat exchange device, it would be too costly to obtain a spherical sample from this form of sample. is preferred.

Hydrogen is introduced into the magnetic heat exchange material by heating a La(Fe _1-x Si _x ) ₁₃ sample having a nearly single-phased NaZn ₁₃ type crystal structure in a temperature range of 250 to 400 ° C. in a hydrogen atmosphere of 0.01 to 1 MPa. Hydrogenation can be performed by treating for 1 to 10 hours under a low temperature environment.

An example of using the magnetic heat exchange material of the present invention is an AMR type magnetic heat exchange device using a liquid heat exchange medium. It comprises a heat exchange device filled with a magnetic heat exchange material, magnetic field generating means for applying and removing a magnetic field to the magnetic heat exchange material, a low temperature side heat exchange section, and a high temperature side heat exchange section. Furthermore, a heat exchange circuit is formed by connecting the heat exchange device, the low temperature side heat exchange section, and the high temperature side heat exchange section, and circulates the liquid heat exchange medium. At least part of the magnetic heat exchange material filled in the heat exchange device is the magnetic heat exchange material of the present invention. The magnetic heat exchange material of the present invention may be loaded into the heat exchange device with one type of magnetic transition temperature. It becomes an efficient heat exchange device.

FIG. 1 is a schematic cross-sectional view of a magnetic heat exchange device according to one embodiment of the present invention. This magnetic heat exchange device uses, for example, water as a liquid heat exchange medium. A low temperature side heat exchange section 21 is provided on the low temperature end side LT of the heat exchange device 10, and a high temperature side heat exchange section 31 is provided on the high temperature end side HT. Between the low temperature side heat exchange section 21 and the high temperature side heat exchange section 31, a switching means 40 for switching the flow direction of the heat exchange medium is provided. Further, a heat exchange medium pump 50 as heat exchange medium transport means is connected to the switching means 40 . The heat exchange device 10, the low temperature side heat exchange section 21, the switching means 40, and the high temperature side heat exchange section 31 are connected by piping to form a heat exchange circuit that circulates the liquid heat exchange medium.

The heat exchange device 10 is filled with a magnetic heat exchange material 12 of the present invention having a magnetocaloric effect. A horizontally movable permanent magnet 14 is arranged outside the heat exchange device 10 as a magnetic field generating means.

Next, the outline of the operation of the magnetic heat exchange device will be described with reference to FIG. A magnetic field is applied to the magnetic heat exchange material 12 in the heat exchange device 10 when the permanent magnet 14 is placed at a position facing the heat exchange device 10 (the position shown in FIG. 2). Therefore, the magnetic heat exchange material 12 having the magnetocaloric effect generates heat. At this time, the heat exchange medium pump 50 and the switching means 40 operate to circulate the liquid heat exchange medium from the heat exchange device 10 toward the high temperature side heat exchange section 31 . Thermal heat is transported to the high temperature side heat exchange section 31 by the liquid heat exchange medium whose temperature has increased due to the heat generated by the magnetic heat exchange material 12 . The high temperature side heat exchange section 31 has a high temperature side heat exchanger 32 and a high temperature side water tank 34 and transfers heat to a radiator 36 .

The permanent magnet 14 is then moved from its position facing the heat exchange device 10 to remove the magnetic field on the magnetic heat exchange material 12 . By removing the magnetic field, the magnetic heat exchange material 12 absorbs heat. At this time, the liquid heat exchange medium is circulated from the heat exchange device 10 toward the low temperature side heat exchange section 21 by operating the heat exchange medium pump 50 and the switching means 40 . Cold heat is transported to the low temperature side heat exchange section 21 by the liquid heat exchange medium cooled by the heat absorption of the magnetic heat exchange material 12 . The low-temperature side exchange section 2 1 has a low-temperature side heat exchanger 22 and a low-temperature side water tank 24 and transports cold heat to a low-temperature consumer 26 .

By repeatedly moving the permanent magnet 14 and repeatedly applying and removing a magnetic field to and from the magnetic heat exchange material 12 in the heat exchange device 10 , a temperature gradient is generated in the magnetic heat exchange material 12 in the heat exchange device 10 . Then, the cooling of the low temperature side heat exchange section 21 is continued by the movement of the liquid heat exchange medium in synchronization with the application/removal of the magnetic field.

A magnetic heat exchange device can achieve high heat exchange efficiency by using a magnetic heat exchange material having a large magnetocaloric effect at a magnetic heat exchange operating temperature.

As an example of another magnetic heat exchange device, a schematic diagram is shown in FIG. 3, and details of the magnetic heat exchange section are shown in FIG. In this figure, 100 is a magnetic heat exchange material, 200 is a heat exchange device, 300 is a heat exchange medium introduction pipe, 400 is a heat exchange medium discharge pipe, 500a and 500b are permanent magnets, 600a and 600b are rotating discs, and 250 is a low temperature. A consumer, 260, represents a radiator. A heat exchange medium can be, for example, water.

As shown in FIG. 4 , the heat exchange device 200 has a cylindrical shape with a rectangular cross section, and the magnetic heat exchange material 100 inside is, for example, spherical with a volume average particle diameter of 0.3 mm. It is filled into the device 200 with a volumetric fill factor of 58%. A heat exchange medium inlet pipe 300 is connected to one end of the heat exchange device 200, and an exhaust pipe 400 is connected to the other end. In this figure, two heat exchange devices 200 having the same shape are provided and arranged parallel to each other.

A pair of rotating discs 600 a and 600 b are provided so as to sandwich the two heat exchange devices 200 , and the rotating discs 600 a and 600 b are supported by a common shaft 700 . This axis 700 is located in the middle of the two heat exchange devices 200 . Permanent magnets 500a and 500b are installed inside the rotating discs 600a and 600b in the vicinity of their rims, respectively. The permanent magnets 500a, 500b face each other and are coupled to each other via a yoke (not shown). As a result, a strong magnetic field space is formed in the gap between the paired permanent magnets 500a and 500b. In this example, two pairs of permanent magnets 500a and 500b are provided so as to correspond to the two heat exchange devices 200, respectively, and are arranged with the axis 700 sandwiched between them.

The permanent magnets 500a and 500b repeatedly approach and separate from the heat exchange device 200 each time the rotary discs 600a and 600b are rotated by 90 degrees. With each pair of permanent magnets 500a, 500b closest to the sidewalls of each heat exchange device 200, the heat exchange device 200 enters and is housed within the magnetic field space formed between the permanent magnets 500a, 500b. A magnetic field is applied to the magnetic heat exchange material 100 .

When the magnetic heat exchange material 100 switches from a state in which a magnetic field is applied to a state in which the magnetic field is removed, the entropy of the electron magnetic spin system increases, and an entropy transfer occurs between the lattice system and the electron magnetic spin system. Thereby, the temperature of the magnetic heat exchange material 100 is lowered, which is transferred to the heat exchange medium, and the temperature of the heat exchange medium is lowered. The heat exchange medium whose temperature has been lowered in this manner is discharged from the heat exchange device 200 through the discharge pipe 400 and supplied to an external low temperature consumer (250: FIG. 4) as heat exchange medium.

In the above-described embodiment, the magnetic heat exchange material 12 in the heat exchange device 10 or the magnetic heat exchange material 100 in the magnetic heat exchange working chamber (heat exchange device) 200 is a single magnetic material having the same composition. The heat exchange material may be uniformly filled, or may be filled with magnetic heat exchange materials having two or more different compositions.

For example, as the magnetic heat exchange material, a plurality of types of magnetic materials may be mixed and filled in the heat exchange device. Also, as the magnetic heat exchange material, a plurality of magnetic materials may be filled in layers in the heat exchange device.

Magnetic heat exchange devices using the above magnetic heat exchange materials can, for example, reduce the size of refrigeration systems, so they can be used for household freezer refrigerators, air conditioners, industrial freezer refrigerators, large freezer refrigerators, liquefied gas storage and transportation. It can be applied to refrigeration systems such as commercial freezers, or heating systems.

After preparing alloys having composition ratios shown in Tables 1-1 and 1-2, they were melted in a vacuum induction melting furnace. After that, the obtained alloy was melted again, and a spherical powder was produced by a gas atomization method. All of the alloys had an aspect ratio of 2 or less and could be formed into spherical particles with a volume average particle diameter in the range of 100 to 150 μm. The produced spherical powder was heat-treated at 1150° C. for 12 hours to increase the La(Fe _1-x Si _x ) ₁₃ phase ratio of the NaZn ₁₃ type crystal structure and reduce the Fe phase and LaFeSi phase. Thereafter, hydrogen was occluded in a hydrogen atmosphere of 0.5 MPa at 300° C. for 5 hours, and cooled to room temperature. In addition, the invention example is sample No. 1 to 22, and sample Nos. for comparative examples. 23-32.

The hydrogenated sample was taken out and subjected to X-ray diffraction measurement and hydrogen content analysis. In the X-ray diffraction measurement using Cu—Kα rays as the X-ray source, the diffraction line intensity of the (422) plane of the La(Fe _1-x Si _x ) ₁₃ phase having the NaZn ₁₃ type crystal structure is compared with the (110) plane of the Fe phase. Table 1 shows the diffraction line intensity ratio of the plane and the diffraction line intensity ratio of the (101) plane of the LaFeSi phase having the CeFeSi type crystal structure. In addition, the hydrogen storage capacity is also represented by the compositional formula. In addition, sample No. is shown in FIG. 5 as an example. 3 shows the X-ray diffraction pattern of 3. In the figure, ● is the (422) plane of the La(Fe _1-x Si _x ) ₁₃ phase, ▴ is the (101) plane of the LaFeSi phase, and × is the (110) plane of the Fe phase.

In addition, 50 spherical powder particles having a diameter of about 100 μm obtained by hydrogenation were examined for the number of cracks in the spherical powder due to hydrogen absorption. Among the 50 samples, samples with 2 or less cracks are indicated as "absent", and samples with 3 or more cracks are indicated as "present". These samples were mounted in a predetermined jig assuming a heat exchange device, and after being subjected to vibration for a certain period of time, the degree of cracking was examined. It could be confirmed.

For the hydrogenated sample, the Curie temperature (Tc) was measured from the temperature characteristics of the magnetization curve, and the magnetic field dependence of magnetization was measured at each temperature. From the magnetization value of , the entropy change ΔS of the electron magnetic spin system was obtained by the following formula 1.

The result is sample no. Tables 1-1 and 1-2 show relative values with 23 as 1. As is clear from this table, the entropy variation ΔS of the electron magnetic spin system is No. 1 in the invention examples. A value approximately equal to or higher than that of No. 23 was obtained, and superiority can be confirmed in terms of practical performance of magnetic heat exchange.

Although the present invention has been described in detail based on the embodiments of the present invention while giving specific examples, the present invention is not limited to the above contents, and can be modified in any way without departing from the scope of the present invention. Change is possible.

10 Heat Exchange Device 12 Magnetic Heat Exchange Material 14 Permanent Magnet 21 Low Temperature Side Heat Exchange Unit 22 Low Temperature Side Heat Exchanger 24 Low Temperature Side Water Tank 26 Low Temperature Consumer 31 High Temperature Side Heat Exchange Unit 32 High Temperature Side Heat Exchanger 34 High Temperature Side Water Tank 36 radiator 40 switching means 50 heat exchange medium pump 100 magnetic heat exchange material 200 heat exchange device 250 low temperature consumer 260 radiator 300 heat exchange medium introduction piping 400 heat exchange medium discharge piping 500a, 500b permanent magnets 600a, 600b rotating disk 700 Axis of rotation HT High temperature field LT Low temperature field

Claims (8)

A magnetic heat exchange material in which the main phase has a NaZn ₁₃ -type crystal structure,
A magnetic heat exchange material characterized by being represented by the following general formula (1).
La _1-a R _a (Fe _1-b-c Si _b T _c ) _e H _f (1)
Here, R in the above formula (1): at least one selected from Sm and Y,
T: at least one selected from V, Cr, Mn, Ni and Cu;
Subscripts a, b, c, e and f are
0<a≦0.30,
0.09≦b≦0.14,
0<c≦0.04,
12.5≦e≦13.5,
1.3≤f≤2.3
satisfy the conditions of A magnetic heat exchange material in which the main phase has a NaZn ₁₃ -type crystal structure,
A magnetic heat exchange material characterized by being represented by the following general formula (2).
La _1-a R _a (Fe _1-bc Si _{b Tc} Co _d ) _e H _f (2)
Here, R in the above formula (2): at least one selected from Sm and Y,
T: at least one selected from V, Cr, Mn, Ni and Cu;
Subscripts a, b, c, d, e and f are
0<a≦0.30,
0.09≦b≦0.14,
0<c≦0.05,
0<d≦0.03,
12.5≦e≦13.5,
1.3≤f≤2.3
satisfy the conditions of _In the _X -ray diffraction measurement using Cu—Kα rays as the _X -ray source, the ₍ 110 3. The magnetic heat exchange material according to claim 1, wherein the diffraction line intensity ratio of the ) plane is 7% or less. In the X-ray diffraction measurement using Cu-Kα rays as the X-ray source, the CeFeSi type crystal structure is compared with the diffraction line intensity of the (422) plane of the La(Fe _1-x Si _x ) ₁₃ phase having the NaZn ₁₃ type crystal structure. 4. The magnetic heat exchange material according to any one of claims 1 to 3, wherein the ratio of the diffraction line intensity of the (101) plane of the LaFeSi phase is 7% or less. The magnetic heat exchange material according to any one of claims 1 to 4, characterized in that said magnetic heat exchange material is spherical particles having an aspect ratio of 2 or less. The magnetic heat exchange material according to any one of claims 1 to 5, characterized in that the volume average particle diameter of the magnetic heat exchange material is 0.05 mm or more and 1 mm or less. A heat exchange device equipped with the magnetic heat exchange material according to any one of claims 1 to 6. A magnetic heat exchange apparatus comprising the heat exchange device according to claim 7 .

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