SHEATH-INTEGRATED MAGNETIC REFRIGERATION MEMBER, PRODUCTION METHOD FOR THE MEMBER AND MAGNETIC REFRIGERATION SYSTEM

Abstract

Provided are a sheath-integrated magnetic refrigeration member capable of preventing degradation of a magnetic refrigeration material with time in a magnetic refrigeration system without lowering the magnetocaloric effect and the thermal conductivity of the magnetic refrigeration material and its production method, and a magnetic refrigeration system using the sheath-integrated magnetic refrigeration member.

The invention is a linear or thin band-like sheath-integrated magnetic refrigeration member including a sheath part 1 containing a non-ferromagnetic metal material and a core part 2 containing a magnetic refrigeration material. The production method for a sheath-integrated magnetic refrigeration member of the invention includes a step of filling a powder of a magnetic refrigeration material into the cavity of a pipe containing a non-ferromagnetic metal material, and a step of linearly working the pipe filled with a powder of a magnetic refrigeration material according to one or more working methods selected from the group consisting of grooved reduction rolling, swaging and drawing. The magnetic refrigeration system of the invention is provided with a means of operating in an AMR (active magnetic refrigeration) cycle using the sheath-integrated magnetic refrigeration member of the invention as the AMR bed.

Claims

1. A linear or thin band-like sheath-integrated magnetic refrigeration member comprising: a sheath part containing a non-ferromagnetic metal material and a core part containing a magnetic refrigeration material.

2. The sheath-integrated magnetic refrigeration member according to claim 1, wherein the non-ferromagnetic metal material contains one or more materials selected from the group consisting of Cu, a Cu alloy, Al, an Al alloy, and a non-ferromagnetic SUS.

3. The sheath-integrated magnetic refrigeration member according to claim 1, wherein the magnetic refrigeration material contains one or more alloys selected from the group consisting of an RFeSi alloy, where R is a rare earth element, and an RFeSiH alloy, where R is a rare earth element, in which the main component has an NaZn.sub.13 type structure.

4. The sheath-integrated magnetic refrigeration member according to claim 3, wherein the composition of the alloy differs in the lengthwise direction of the sheath-integrated magnetic refrigeration member.

5. The sheath-integrated magnetic refrigeration member according to claim 1, wherein a void ratio of the core part is less than 20%.

6. The sheath-integrated magnetic refrigeration member according to claim 1, wherein the sheath-integrated magnetic refrigeration member deforms two-dimensionally or three-dimensionally.

7. The sheath-integrated magnetic refrigeration member according to claim 1, provided with a metal mesh or a porous metal plate bonded to the sheath part.

8. The sheath-integrated magnetic refrigeration member according to claim 7, wherein the sheath part is bonded to the metal mesh or the porous metal plate according to one or more bonding methods selected from the group consisting of brazing, soldering and adhering with an adhesive.

9. A method for producing a sheath-integrated magnetic refrigeration member, comprising: filling a powder of a magnetic refrigeration material into the cavity of a pipe containing a non-ferromagnetic metal material, and linearly working the pipe filled with a powder of a magnetic refrigeration material according to one or more working methods selected from the group consisting of grooved reduction rolling, swaging and drawing.

10. The method for producing a sheath-integrated magnetic refrigeration member according to claim 9, wherein the magnetic refrigeration material contains one or more alloys selected from the group consisting of an RFeSi alloy, where R is a rare earth element, and an RFeSiH alloy, where R is a rare earth element, in which the main component has an NaZn.sub.13 type structure.

11. The method for producing a sheath-integrated magnetic refrigeration member according to claim 9, wherein the cross-sectional shape of the linearly-worked pipe filled with a powder of a magnetic refrigeration material is one or more shapes selected from the group consisting of a circular shape, a semicircular shape and a square shape.

12. The method for producing a sheath-integrated magnetic refrigeration member according to claim 9, further comprising thin band-like working the linearly-worked pipe filled with a powder of a magnetic refrigeration material according to reduction rolling.

13. A magnetic refrigeration system provided with a means of operating in an AMR (active magnetic refrigeration) cycle using the sheath-integrated magnetic refrigeration member according to claim 1 as the AMR bed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1A, FIG. 1B and FIG. 1C are each a schematic view of a cross section vertical to the lengthwise direction of a sheath-integrated magnetic refrigeration member of one embodiment of the present invention.

[0027] FIG. 2A and FIG. 2B are each a schematic view of a sheath-integrated magnetic refrigeration member of one embodiment of the present invention.

[0028] FIG. 3A is a schematic view of a metal mesh bonded to a sheath part in a sheath-integrated magnetic refrigeration member of one embodiment of the present invention; FIG. 3B is a schematic view of a porous metal plate bonded to a sheath part in a sheath-integrated magnetic refrigeration member of one embodiment of the present invention

[0029] FIG. 4 is a schematic view showing one example of an arrangement of sheath-integrated magnetic refrigeration members in an AMR bed where sheath-integrated magnetic refrigeration members are used.

[0030] FIG. 5 is a schematic view of a cross section vertical to the lengthwise direction and a cross section parallel to the lengthwise direction of a sheath-integrated magnetic refrigeration member of one embodiment of the present invention.

[0031] FIG. 6 is a schematic view showing one example of a magnetic refrigeration system using a sheath-integrated magnetic refrigeration member of one embodiment of the present invention.

[0032] FIG. 7 is a view showing one example of a magnetic Brayton cycle of a sheath-integrated magnetic refrigeration member used in a magnetic refrigeration system.

DESCRIPTION OF EMBODIMENTS

[0033] Hereinunder the present invention is described in detail.

Sheath-Integrated Magnetic Refrigeration Member

[0034] The present invention relates to a sheath-integrated magnetic refrigeration member that shows high performance and high corrosion resistance.

[0035] The present invention is a linear or thin band-like sheath-integrated magnetic refrigeration member that includes a sheath part containing a non-ferromagnetic metal material and a core part containing a magnetic refrigeration material. The sheath-integrated magnetic refrigeration member can prevent degradation of a magnetic refrigeration material with time in a magnetic refrigeration system without lowering the magnetocaloric effect and the thermal conductivity of the magnetic refrigeration material.

[0036] From the viewpoint of improving the magnetocaloric effect of the sheath-integrated magnetic refrigeration member, the content of the magnetic refrigeration material in the core part is preferably 85% by mass or more, more preferably 90% or more, even more preferably 95% by mass or more, further more preferably 98% by mass or more.

[0037] From the viewpoint of stably attaining a great magnetocaloric effect in a room temperature range and from the viewpoint of not containing a toxic element, the magnetic refrigeration material preferably contains one or more alloys selected from the group consisting of an RFeSi alloy (where R is a rare earth element) and an RFeSiH alloy (where R is a rare earth element) in which the main component has an NaZn.sub.13 type structure. Here, the RFeSi alloy can be produced by melting, casting and homogenizing treatment according to an ordinary method. The RFeSiH alloy can be produced by melting, casting and homogenizing treatment followed by hydrogenation treatment according to an ordinary method. The content of the alloy in the magnetic refrigeration material is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more.

[0038] The RFeSi alloy in which the main component has an NaZn.sub.13 type structure is, for example, an alloy in which the main component is an R.sup.1(Fe,Si).sub.13 compound (R.sup.1: 7.14 atom %) having an NaZn.sub.13 type structure. Regarding the alloy composition of this alloy, preferably, R.sup.1 is 6 to 10 atom % (R.sup.1 is one or more selected from a rare earth element and Zr, and La is indispensable therein), and the Si amount is 9 to 12 atom % among the elements except R.sup.1 in the compound. Also preferably, a part of Fe in the R.sup.1(Fe,Si).sub.13 compound is substituted with M (one or more elements selected from the group consisting of Co, Mn, Ni, Al, Zr, Nb, W, Ta, Cr, Cu, Ag, Ga, Ti and Sn) to produce a series of alloys each having a different Curie temperature (for example, alloys in which the main component is an R.sup.1(Fe,M,Si).sub.13 compound (R.sup.1: 7.14 atom %) having an NaZn.sub.13 type structure). By combining the thus-produced alloys each having a different Curie temperature in layers to use them in a magnetic refrigeration system (for example, see FIG. 5), the cooling performance of the refrigeration system can be further increased.

[0039] The above-mentioned alloy can be obtained by melting a raw material metal or alloy in vacuum or in an inert gas, preferably in an Ar atmosphere, and then casting the resultant melt into a planar mold or a book mold or casting it according to a liquid quenching technique or a strip casting method. Also preferably, a powdery alloy can be produced according to an atomizing method. Depending on the alloy composition, the cast alloy may be composed of a primary crystal -Fe(, Si) and an RSi phase (where R is a rare earth element). In this case, for forming an R(Fe,Si).sub.13 compound (where R is a rare earth element), the alloy may be homogenized at around the decomposition temperature of the compound (at around 900 to 1300 C., greatly depending on the alloy composition) or lower than the temperature for a predetermined period of time (10 hours to 30 days, though depending on the morphology of the alloy).

[0040] The alloy after homogenization in which the main component is an R(Fe,Si).sub.13 compound is brittle, and can be mechanically ground with ease into a powder having a size of a few hundred m. For absorption of H, the alloy may be heat-treated in a hydrogen atmosphere after roughly ground as above or without being ground. The treatment condition may be changed depending on the amount of hydrogen to be absorbed, but preferably, in general, the alloy may be heat-treated under a hydrogen partial pressure of around 0.1 to 0.5 MPa at 200 to 500 C. for about 1 to 20 hours. After hydrogenation treatment, the alloy becomes more brittle, and at the time when it is taken out, the alloy is often a powder in a size of a few hundred m.

[0041] The thus-produced powder may be filled into a pipe containing a non-ferromagnetic metal material, for example, into the cavity of a pipe containing one or more materials selected from the group consisting of Cu, a Cu alloy, Al, an Al alloy and a non-ferromagnetic SUS. At that time, preferably, tapping is combined to fill the powder at a possibly highest filling rate. Also preferably, a metal soap or the like is mixed before filling so as to previously increase the filling performance. For intentionally increasing the thermal conductivity thereof, the hydrogenated powder may be mixed with a metal powder such as Cu or Al. The particle size and the weight fraction thereof may be appropriately determined depending on the performance of the system, but preferably a powder having an average particle size of around 1 to 100 m is mixed in an amount of 1 to 15% by weight. The content of the one or more materials selected from the group consisting of Cu, a Cu alloy, Al, an Al alloy and a non-ferromagnetic SUS in the non-ferromagnetic metal material is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more.

[0042] As needed, both ends of the pipe filled with a magnetic refrigeration material powder may be crushed or a metal lid may be brazed to each end of the pipe, for example. After a magnetic refrigeration material powder is filled into a pipe, the pipe filled with a magnetic refrigeration material powder may be linearly worked according to one or more working methods selected from the group consisting of grooved reduction rolling, swaging and drawing. For example, preferably, until the outer diameter of the pipe reaches 10 to 80% or so of the original outer diameter thereof, the pipe filled with a magnetic refrigeration material powder is drawn. As a result of the treatment, the filling rate of the magnetic refrigeration material powder can be increased without heating. After worked, the cross section of the pipe filled with a magnetic refrigeration material powder may be any one or more shapes selected from the group consisting of a circular shape (see FIG. 1A), a semicircular shape and a square shape (see FIG. 1B). Finally, in the case where the pipe filled with a magnetic refrigeration material powder is worked into a thin band-like shape (ribbon-like shape) (see FIG. 1C), the pipe may be further rolled for reduction after drawn into a predetermined level. Also the pipe may be rolled for reduction with a grooved roll to have a rectangular cross section. One example of a cross section vertical in the lengthwise direction of the thus-produced sheath-integrated magnetic refrigeration member is schematically shown in FIG. 1. A sheath part 1 is formed of a material of the pipe, and preferably a core part 2 contains one or more alloys selected from the group consisting of an RFeSi alloy and an RFeSiH alloy.

[0043] As a result of the working treatment as above, the pipe filled with a magnetic refrigeration material powder is worked into a linear or thin band-like pipe, and accordingly, the filling rate of the magnetic refrigeration material powder therein increases, and owing to increase in the occupancy rate of the magnetic refrigeration material per the unit volume in the core part, the resultant pipe can exhibit a highly-efficient magnetic refrigeration effect. The filling rate of the magnetic refrigeration material powder in the core part in this case is preferably higher, and is ideally most preferably 100%, but is substantially preferably 80% or more, more preferably 90% or more. The occupancy rate can be calculated from the area-based void ratio (areal void ratio) in the core part in observation of an arbitrary cross section of the sheath-integrated magnetic refrigeration member, and the relationship between the occupancy rate V and the areal void ratio S is V=100S (%). Here, the relationship between the occupancy rate and the filling rate is (occupancy rate)1=filling rate. Accordingly, ideally, the void ratio is most preferably 0%, but is substantially preferably less than 20%, more preferably less than 10%.

[0044] The resultant linear or thin band-like sheath-integrated magnetic refrigeration member is cut into a size suitable for a magnetic refrigeration system, and as needed, the sheath part of the cut edge is pressure-bonded or the cut edge is sealed with a resin, for example. Further, the member is worked to have a suitable form and then arranged in a magnetic refrigeration system. For efficient heat exchange with a heat medium, the sheath-integrated magnetic refrigeration member may be two-dimensionally or three-dimensionally deformed in accordance with the medium stream so as to have any desired shape such as a waved shape or a swirly shape, as schematically illustrated in FIG. 2. Deformation and cut edge sealing may be carried out in reverse order. Also as needed, the sheath part 1 may be bonded to a metal mesh 3 or a porous metal plate 4 through which a heat medium can pass according to one or more bonding methods selected from the group consisting of, for example, brazing, soldering and adhesion with an adhesive, as schematically illustrated in FIG. 3. Having the configuration, heat exchange can be attained efficiently and the sheath-integrated magnetic refrigeration member can be handled with ease.

[0045] In the case where the sheath-integrated magnetic refrigeration member is used as an AMR bed, preferably, the sheath-integrated magnetic refrigeration member is so arranged that a heat medium can run in a vertical direction 5 relative to the lengthwise direction of the member, as shown in FIG. 4. In the case where a heat medium runs in a parallel direction 6 relative to the lengthwise direction of the sheath-integrated magnetic refrigeration member owing to planning of a refrigeration system (see FIG. 4), the composition of the magnetic refrigeration material may differ in the lengthwise direction of the sheath-integrated magnetic refrigeration member. For example, as schematically illustrated in FIG. 5, plural magnetic refrigeration materials 2a to 2j may be filled in one sheath in descending order or ascending order of the Curie temperature (Tc) thereof to provide the sheath-integrated magnetic refrigeration member. With that, the sheath-integrated magnetic refrigeration member can create a large temperature difference. In FIGS. 5, 2a to 2j each show a magnetic refrigeration material having a mutually different composition. Each having such a mutually different composition, the magnetic refrigeration materials 2a to 2j also mutually differ in the Curie temperature (Tc). Preferably, the Curie temperature (Tc) of the magnetic refrigeration materials 2a to 2j differs in descending or ascending order of the magnetic refrigeration materials 2a to 2j.

[0046] Thus obtained, the sheath-integrated magnetic refrigeration member has a high filling rate of 80% or more in the core part, and the magnetic refrigeration material therein is not corroded as surrounded by the sheath part, and in addition, since the thermal conductivity of the sheath part is high, the sheath-integrated magnetic refrigeration member can realize a high thermal exchange efficiency in a magnetic refrigeration system.

Magnetic Refrigeration System

[0047] The magnetic refrigeration system of the present invention is provided with a means of operating in an AMR (active magnetic refrigeration) cycle using the sheath-integrated magnetic refrigeration member of the present invention as the AMR bed. One example of the magnetic refrigeration system of the present invention is shown in FIG. 6.

[0048] One example of the magnetic refrigeration system of the present invention is provided with an AMR bed 10, a solenoid 20 to generate a magnetic field in the AMR bed, a cooling part 40 to cool a fluid to be cooled using a heat medium 30 cooled by the AMR bed 10, and a heat exhausting part 50 to exhaust the heat of the heat medium 30 heated by the AMR bed 10, as shown in FIG. 6. The AMR bed 10 uses the sheath-integrated magnetic refrigeration member of the present invention. The cooling part 40 is provided with a displacer 41 for injecting and ejecting the heat medium 30 in or from the cooling part 40 and a heat exchanger 42 for carrying out heat exchange between the heat medium 30 cooled by the AMR bed 10 and the fluid to be cooled. The heat exhausting part 50 is provided with a displacer 51 for injecting and ejecting the heat medium 30 in or from the heat exhausting part 50 and a heat exchanger 52 for exhausting heat from the heat medium 30 heated by the AMR bed 10. The heat medium 30 passes through the AMR bed 10 and moves between the cooling part 40 and the heat exhausting part 50. For example, in the case where water is cooled using one example of the magnetic refrigeration system of the present invention, the fluid to be cooled is water, and in the case where alcohol is cooled, the fluid to be cooled is alcohol.

[0049] Next, an AMR cycle utilized by one example of the magnetic refrigeration system of the present invention is described with reference to FIG. 6 and FIG. 7. FIG. 7 is a view showing one example of a magnetic Brayton cycle used by one example of the magnetic refrigeration system of the present invention mentioned above, using a sheath-integrated magnetic refrigeration member. A curve with H=0 is a temperature-entropy curve of the sheath-integrated magnetic refrigeration member in demagnetization. A curve with H=H.sub.1 is a temperature-entropy curve of the sheath-integrated magnetic refrigeration member in a magnetic field.

[0050] In a state where the heat medium 30 is in the cooling part 40, the AMR bed 10 is adiabatically magnetized to increase the temperature of the sheath-integrated magnetic refrigeration member in the AMR bed 10 (in FIG. 7, A.fwdarw.B). Next, the displacers 41 and 51 in the cooling part 40 and the heat exhausting part 50 are respectively moved to move the heat medium 30 from the cooling part 40 to the heat exhausting part 50. As a result, the heat medium 30 receives heat from the sheath-integrated magnetic refrigeration member in the AMR bed 10 and the temperature of the heat medium 30 therefore increases. On the other hand, the heat of the sheath-integrated magnetic refrigeration member in the AMR bed 10 is absorbed by the heat medium 30, and therefore the temperature of the sheath-integrated magnetic refrigeration member in the AMR bed 10 lowers (in FIG. 7, B.fwdarw.C). The heat medium 30 that has received the heat from the sheath-integrated magnetic refrigeration member in the AMR bed 10 exhausts the heat in the heat exchanger 52 in the heat exhausting part 50.

[0051] In a state where the heat medium 30 is in the heat exhausting part 50, the AMR bed 10 is adiabatically demagnetized to lower the temperature of the sheath-integrated magnetic refrigeration member in the AMR bed 10 (in FIG. 7, C.fwdarw.D). Next, the displacers 41 and 51 in the cooling part 40 and the heat exhausting part 50 are respectively moved to move the heat medium 30 from the heat exhausting part 50 to the cooling part 40. As a result, the heat of the heat medium 30 is absorbed by the sheath-integrated magnetic refrigeration member in the AMR bed 10 and the temperature of the heat medium 30 therefore lowers. On the other hand, the sheath-integrated magnetic refrigeration member in the AMR bed 10 receives heat from the heat medium 30, and therefore the temperature of the sheath-integrated magnetic refrigeration member in the AMR bed 10 increases (in FIG. 7, D.fwdarw.A). The heat medium 30 that has been cooled by the sheath-integrated magnetic refrigeration member in the AMR bed 10 then cools the fluid to be cooled via the heat exchanger 42 in the cooling part 40. In the manner as above, one example of the magnetic refrigeration system of the present invention can utilize an AMR cycle. The sheath-integrated magnetic refrigeration member for use in the AMR bed draws a magnetic Brayton cycle of A.fwdarw.B.fwdarw.C.fwdarw.D as in FIG. 7.

[0052] The magnetic refrigeration system of the present invention is not limited to the above-mentioned one example of the magnetic refrigeration system of the present invention so far as the system is provided with a means of operating in an AMR cycle. Also the AMR cycle is not limited to the above-mentioned AMR cycle so far as magnetic refrigeration can be carried out by utilizing an AMR bed using the sheath-integrated magnetic refrigeration member of the present invention.

EXAMPLES

[0053] Hereinunder more specific embodiments of the present invention are described with reference to Examples, to which, however, the present invention is not limited.

[0054] According to a strip casting method of radiofrequency-melting La having a purity of 99% by weight or more, an Fe metal, and Si having a purity of 99.99% by weight or more in an Ar atmosphere, followed by casting the melt into a copper single roll, a thin band-like alloy containing 7.2 atom % of La and 10.5 atom % of Si with a balance of Fe was produced. The alloy was exposed to H.sub.2 of 0.2 MPa at 200 C. for hydrogen absorption, then cooled and sieved to give a coarse powder of 250 mesh or less.

[0055] Subsequently, stearic acid was added to the coarse powder in a ratio of 0.1% by weight, and stirred with a V blender for 30 minutes, and the resultant powder was filled with tapping into a copper pipe having a size of outer diameter 6 mminner diameter 5 mm and a length of 300 mm. As calculated from the weight change m between the weight of the unfilled copper pipe, and the total weight of the filled copper pipe and the powder, the density of the coarse powder, and the pipe inner volume Vp, the filling rate of the coarse powder was about 50%.

[0056] The copper pipe filled with the coarse powder was rolled for reduction using a grooved roll until the outer diameter thereof could reach 3 mm to give a sheath-integrated magnetic refrigeration member. The cross section thereof vertical to the rolling direction was observed, and the area-based void ratio of La(Fe.sub.0.89Si.sub.0.11).sub.13H.sub.x was 7%, and the area-based filling rate was 93%. In the thus-produced sheath-integrated magnetic refrigeration member, La(Fe.sub.0.89Si.sub.0.11).sub.13H.sub.x is protected from a heat medium by the copper sheath part, and therefore La(Fe.sub.0.89Si.sub.0.11).sub.13H.sub.x can be prevented from being degraded by a heat medium. Since the copper sheath part has a high thermal conductivity, heat exchange between La(Fe.sub.0.89Si.sub.0.11).sub.13H.sub.x and a heat medium can be attained effectively. Further, since the filling rate of La(Fe.sub.0.89Si.sub.0.11).sub.13H.sub.x in the core part is high, the magnetocaloric effect of La(Fe.sub.0.89Si.sub.0.11).sub.13H.sub.x can be high.

REFERENCE SIGNS LIST

1 Sheath Part

2 Core Part

2a to 2j Magnetic Refrigeration Materials

3 Metal Mesh

4 Porous Metal Plate

5 Heat Medium Running Direction 1

6 Heat Medium Running Direction 2

10 AMR Bed

20 Solenoid

30 Heat Medium

40 Cooling Part

41, 51 Displacers

42, 52 Heat Exchangers

50 Heat Exhausting Part