JP2014044003A - Method of manufacturing heat exchanger composed of magnetic refrigerating material, and heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a heat exchanger composed of a magnetic refrigerating material capable of suppressing degradation of performance by suppressing deposition of α-Fe, and the heat exchanger composed of the magnetic refrigerating material.SOLUTION: A thin band body 13 is manufactured by a melt quenching method by using a power material 11. Then the thin band body 13 is heated in a heating chamber 21 filled with an inert gas. Four sheets of the thin band bodies 13 having undergone heat treatment, are stacked to prepare a plate-shaped stacked body 31. A material piece 33 as a plate-shaped member provided with a groove of 0.1 mm depth extending in the depth direction on its main face, is formed by cutting, grinding and polishing the stacked body 31. The material piece 33 is charged into a heat treatment furnace 35 to be heated, so that a material piece 41 is prepared by making the material piece 33 absorb hydrogen, and the material pieces 41 are stacked to manufacture a heat exchanger 43 in which the groove part is applied as a micro-channel.

Description

  The present invention relates to a heat exchanger made of a magnetic refrigeration material that can be used in a refrigeration cycle used for air conditioning, refrigeration, refrigeration and the like.

As an environmentally-friendly refrigeration technology, research on clean and energy-efficient magnetic refrigeration technology is underway. Magnetic refrigeration is to apply a magnetic field from the outside to a magnetic refrigeration material, which is a magnetic material, to develop a magnetocaloric effect in the magnetic refrigeration material. As a magnetic refrigeration material, a La (FeSi) ₁₃ -based material exhibits a high magnetocaloric effect. It is known. In addition, it is known that the magnetic refrigeration material changes its Curie temperature by storing hydrogen and exhibits the magnetocaloric effect at room temperature.

  In order to improve the heat exchange efficiency of the magnetic refrigeration material, it is conceivable to form a heat exchanger made of the magnetic refrigeration material into a microchannel. In order to form a microchannel, a method of sintering a magnetic refrigeration material that has been pulverized into powder has been proposed (see Patent Document 1).

JP 2007-291437 A

Α-Fe is mixed in the La (FeSi) ₁₃ material described above. When the amount of α-Fe mixed is large, the magnetocaloric effect, that is, the entropy change (ΔS) is lowered. In order to reduce the amount of α-Fe, it is effective to perform a heat treatment. However, when sintering is performed to form a powdered magnetic refrigeration material in the process of manufacturing a microchannel, α-Fe is again formed. The amount of entropy change may be reduced due to precipitation.

  The objective of this invention is providing the manufacturing method of a magnetic refrigeration material heat exchanger and a magnetic refrigeration material heat exchanger which can suppress precipitation of (alpha) -Fe and can suppress performance degradation.

The invention according to claim 1, which has been made to solve the above-mentioned problem, is an alloy production in which a molten alloy of a magnetic refrigeration material containing La, Fe, and Si is quenched with a cooling roll to produce a ribbon-like alloy (13). Forming a groove on the ribbon-like alloy, laminating a ribbon-like alloy having a groove formed by the groove-forming step, and forming a heat exchanger (43) having the groove as a flow path And a heat treatment step of increasing the La (FeSi) ₁₃ phase by subjecting the ribbon-shaped alloy to a heat treatment, and a manufacturing method of a magnetic refrigeration material heat exchanger.

In such a method for manufacturing a magnetic refrigeration material heat exchanger, a thin-band alloy produced by the so-called strip cast method in the alloy production process increases the La (FeSi) ₁₃ phase and reduces the α-Fe phase by heat treatment. Has been. In addition, there is no need to perform a high-temperature heat treatment in which α-Fe is easily reprecipitated, such as sintering, at the stage of manufacturing the heat exchanger. Therefore, a decrease in entropy change amount can be suppressed, and a heat exchanger exhibiting a high magnetocaloric effect by suppressing performance deterioration of the magnetic refrigeration material can be manufactured.

Further, the steps of powdering the magnetic refrigeration material and re-forming by sintering can be omitted, and the manufacturing cost can be reduced.
In addition, although the timing which performs the heat processing process of this invention is not specifically limited, The possibility that the joining in an assembly process will be cancelled | released by heating will be lost by performing before the assembly process after the said alloy preparation process.

  Moreover, in this invention, you may provide the hydrogen absorption process which makes a thin strip | belt-shaped alloy absorb hydrogen by heat processing. This hydrogen absorption step is preferably performed after the heat treatment step in order to prevent the absorbed hydrogen from being detached, and the timing is not particularly limited as long as it is after the heat treatment step.

  By the way, the groove formed by the groove forming step may be formed in a size to be a microchannel. Specifically, it is preferable that the width of the channel (the length on the short side in the opening) is several mm or less, particularly 0.5 mm or less.

  The manufacturing method may further include a stacking step for manufacturing a plate-like member (31) formed by stacking the ribbon-shaped alloys manufactured by the alloy manufacturing step. In that case, the groove forming step is a step of forming a groove in the plate-like member produced by the laminating step, and the assembling step is a step of laminating the plate-like member (41) in which the groove is formed. Good.

In such a method for manufacturing a magnetic refrigeration material heat exchanger, since the grooves are formed in the plate-like member on which the ribbon-like alloys are stacked, each of the ribbon-like alloys can be thinly formed. If the ribbon-like alloy is thinned, the temperature decrease rate in the melt quenching method (strip casting method) is increased, so that a fine structure tends to be formed. As a _{result, La (Fe x, Si 1} -x) 13 likely size of the particles is reduced, it is possible to shorten the time needed for the heat treatment in the heat treatment step.

  The lamination step may be a step of joining and laminating the ribbon-like alloy with an adhesive (51). The adhesive at that time may be a conductive adhesive. By using an adhesive, it is possible to satisfactorily fill the gaps in the ribbon-like alloy and suppress breakage. Moreover, when a conductive adhesive is used, the thermal conductivity can be increased as compared with a normal adhesive, and the performance of the heat exchanger can be improved.

  Moreover, the said lamination process is good also as a process of joining and laminating | stacking the said strip-shaped alloy by pressure bonding. Specifically, a bonding material containing at least one of the metal powder (53) and the metal ribbon (55) is disposed between the ribbon-shaped alloys and pressed to form a thin film via the bonding material. It is good also as a process of joining and laminating strip-shaped alloys, and forming a metal thin film (71) on the surface of a thin strip-shaped alloy, and joining and laminating thin strip-like alloys through the metal thin film It is good. The metal thin film may be formed by any one method selected from the group consisting of vapor deposition, sputtering, and plating.

By sandwiching and joining the metal material in the ribbon-like alloy as described above, the thermal conductivity can be increased and the performance of the heat exchanger can be improved.
In the laminating step, a metal material having a melting point lower than the heat treatment temperature in the heat treatment step is disposed between the ribbon-like alloys, and is pressed by hot pressing at a temperature lower than the heat treatment temperature and higher than the melting point. It is good also as a process of laminating. In such a lamination process, the ribbon-like alloy can be firmly joined by once melting the metal.

  The invention described in claim 10 is a heat exchanger (43) having a microchannel using a magnetic refrigeration material, and is a plate formed by laminating a ribbon-like alloy (13) containing La, Fe, and Si. This is a magnetic refrigeration material heat exchanger comprising a plate-like magnetic refrigeration material laminated with a groove serving as a flow path formed on one of its main surfaces. .

  The magnetic refrigeration material heat exchanger configured in this way does not require high-temperature heat treatment in which α-Fe is easily reprecipitated, such as sintering, at the stage of manufacturing the heat exchanger. It can be suppressed, and a high magnetocaloric effect is achieved.

  In addition, the code | symbol in the parenthesis described in this column and a claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is shown. It is not limited.

It is a figure explaining the manufacturing process of a microchannel heat exchanger. (A) is a perspective view in which an adhesive is disposed between the ribbons, (B) is a perspective view in which metal powder is disposed between the ribbons, and (C) is between the ribbons. It is the perspective view which arranged the metal ribbon. (A) is a figure which performs the assembly process by adhesion | attachment, (B) is a figure which shows the lamination process by a press.

Embodiments of the present invention will be described below with reference to the drawings.
[Example 1]
<Manufacture of microchannel heat exchangers using magnetic refrigeration materials>
In this example, a microchannel heat exchanger was manufactured using a magnetic refrigeration material. As the magnetic refrigeration material, a LaFe ₁₃ -based material having a NaZn ₁₃ crystal structure was used. The LaFe ₁₃ material is a _{La (Fe x, Si 1-} x) 13 (0 ≦ x ≦ 1), the x and predetermined value. In this embodiment, x = 0.88. The manufacturing process will be described with reference to FIG. Since FIG. 1 is a schematic diagram, the ratio of the size of each component may be different from the actual one.

(1) Powder preparation A single element powder (or bulk) was prepared and mixed at a predetermined ratio to obtain a powder raw material 11 of a magnetic refrigeration material. The composition example of the powder raw material 11 is shown below.
La: 17 wt%
Fe: 78 wt%
Si: 5 wt%
(2) Melting and quenching (alloy manufacturing process)
Using the prepared powder raw material 11, a ribbon ₁₃ which is a ribbon-like alloy having a NaZn ₁₃ crystal structure was produced by a melt quenching method (strip casting method).

  Here, the molten metal 17 of the powder raw material 11 was discharged from the nozzle 15 to a copper rotating roll 19 (cooling roll) and rapidly cooled to form a thin ribbon. At this time, the width of the ribbon 13 was adjusted to 7 mm and the thickness to 0.1 mm.

(3) Heat treatment step In the heating chamber 21 filled with an inert gas, the ribbon 13 was heated by a heater 23 at 1000 ° C. for 200 hours. By this heat treatment, the proportion of α-Fe was reduced. In addition, when the heating temperature is 900 to 1100 ° C. and the heating time is about 10 to 350 hours, the ratio of α-Fe can be satisfactorily reduced. Further, instead of filling the inert gas, the heating chamber 21 may be vacuum-treated for heat treatment.

(4) Molding of laminated body (lamination process)
Four thin strips 13 subjected to the heat treatment in the heat treatment step were laminated to form a plate-like laminate 31 having a molding dimension of 7 mm in width and 0.4 mm in thickness.

  As shown in FIG. 2 (A), this laminated body 31 is obtained by arranging and bonding a conductive adhesive 51 between the ribbons 13, and a magnetic refrigeration material layer and an adhesive layer are laminated. It has been made. The conductive adhesive 51 is a mixture of metal powder such as silver, copper, and aluminum with an organic solvent, resin, or the like, and exhibits conductivity through the metal powder after bonding.

(5) Molding of material pieces (groove forming process)
The long plate-shaped laminate 31 is cut, ground, polished, etc., and is a rectangular plate having a width of 7 mm × a depth of 10 mm and a thickness of 0.4 mm. The main surface has a depth of 0.1 mm. A piece of material 33, which is a plate-like member having a groove extending in the direction, was formed. This groove becomes a flow path (microchannel).

(6) Hydrogen absorption process The material piece 33 was put into a heat treatment furnace 35 (flow furnace) and heated to 270 ° C. by a heater 37 to produce a material piece 41 of a magnetic refrigeration material in which the material piece 33 absorbed hydrogen. Note that the amount of hydrogen absorbed can be controlled by adjusting the heat treatment temperature in the range of 180 to 300 ° C.

(7) Laminate formation of microchannel (assembly process)
As shown in FIG. 3 (A), the material pieces 41 were stacked and joined together with an adhesive 61 to manufacture a microchannel heat exchanger 43 in which the groove portion becomes a microchannel. The material piece 41a laminated on the uppermost side is one in which no groove is formed.

A microchannel heat exchanger using a magnetic refrigeration material was manufactured by the steps (1) to (7) described above.
<Effect of the invention>
Since the microchannel heat exchanger 43 manufactured by the manufacturing method of the present embodiment is not subjected to high-temperature heat treatment in which α-Fe such as sintering is likely to reprecipitate at the stage of manufacturing the heat exchanger, the entropy change A decrease in the amount can be suppressed, and the performance deterioration of the magnetic refrigeration material can be suppressed, and a high magnetocaloric effect can be maintained. Moreover, since the process of pulverizing and sintering the magnetic refrigeration material is omitted, the manufacturing cost can be reduced.

Further, in the above manufacturing method, since the four strips 13 are laminated to form the laminate 31, the strip 13 is formed very thin in the melting and quenching process. When thinning the thin-strip alloy, will microstructure for lowering the rate of temperature becomes _{faster, La (Fe x, Si 1} -x) 13 likely size of the particles is reduced, the time required for the heat treatment in the heat treatment step Can be shortened.

  Moreover, since the thin strip 13 is joined by the conductive adhesive 51, the gap of the thin strip 13 can be filled well, and the strength of the laminated body 31 can be increased and the damage can be suppressed. In addition, since the conductive material has a large thermal conductivity, the thermal conductivity of the laminate 31 is increased. Since the microchannel heat exchanger 43 made of this laminate 31 has a high thermal conductivity, it can efficiently exchange heat with the refrigerant when generating or absorbing heat when a magnetic field is applied or when the magnetic field is turned off.

In addition, since the LaFe ₁₃ alloy absorbs hydrogen, the lattice expands to cause distortion, and magnetostriction also occurs due to the application of a magnetic field. Therefore, stress is generated and cracks and cracks are likely to occur. Thus, in the laminated structure through the conductive adhesive 51, the stress can be released in the conductive adhesive region, and the occurrence of cracks and cracks can be suppressed.

[Example 2]
In this example, a microchannel heat exchanger was manufactured by the same manufacturing method as in Example 1 except for the step of forming the laminate of the above (4). However, in the step of forming the laminate, a conductive adhesive was used. Instead of 51, the metal powder 53 shown in FIG. 2 (B) was disposed between the ribbons 13, and the ribbons 13 were bonded by pressure bonding.

  Copper was used as the metal powder 53, and as shown in FIG. The average particle size of the metal powder 53 used was 1 to 100 μm. When the average particle size is 100 μm or less, the adhesive layer (metal layer) can be prevented from becoming too thick, and the laminated body becomes large, or the proportion of the magnetic refrigeration material layer becomes small and the performance deteriorates. This can be suppressed. Further, when the average particle size is 1 μm or more, it is possible to sufficiently secure the thickness of the adhesive layer, and it is possible to suppress a decrease in adhesive force. The average particle size was measured by the following method. A metal powder is dispersed in a solvent such as water and a photograph is taken. This photograph is image-analyzed to derive the average particle size of the powder. This laminated body 31 is formed by laminating a magnetic refrigeration material layer and a metal layer.

  The press temperature is preferably lower than the heat treatment temperature of the heat treatment step (3) so as not to affect the performance of the magnetic refrigeration material (so that the amount of α-Fe does not increase). It may be between 700 ° C. Moreover, it is good to adjust and set a press pressure suitably.

  Similar to the microchannel heat exchanger manufactured in Example 1, the microchannel heat exchanger manufactured by the manufacturing method of this example can exhibit a high magnetocaloric effect and achieves reduction in manufacturing cost. it can.

Moreover, since the laminated body 31 is formed by sandwiching a metal material between the ribbons 13, the heat conductivity can be increased and the performance of the heat exchanger can be improved.
In addition, it replaces with the metal powder 53 mentioned above, the metal strip 55 shown in FIG.2 (C) may be arrange | positioned between each strip 13, and the strip 13 may be crimped | bonded together. A microchannel heat exchanger having the same effects as in the present embodiment can be manufactured. In this case, the thickness of the metal ribbon 55 was 1 to 100 μm. The reason why the thickness is in this range is the same reason as that of the metal powder described above.

[Example 3]
In this example, a microchannel heat exchanger was manufactured by the same manufacturing method as in Example 1 except for the step of forming the laminate of the above (4). However, in the step of forming the laminate, a conductive adhesive was used. In place of 51, a bonding layer 71 made of a metal thin film was formed on the surface of the ribbon 13, and the ribbon 13 was pressure bonded in that state.

  The bonding layer 71 was formed by a vapor deposition apparatus that forms a metal thin film by a vapor deposition method. Aluminum was used as the material for the metal thin film. The thickness of aluminum was 1 μm. Thereafter, as shown in FIG. 3 (B), the laminate 31 was formed by press bonding with a press 63 at a temperature of 20 ° C. and a pressure of 10 MPa. The pressing temperature and pressure can be adjusted as appropriate.

  The microchannel heat exchanger manufactured by the manufacturing method of the present embodiment can exhibit a high magnetocaloric effect similarly to the microchannel heat exchanger manufactured in the first and second embodiments. Further, compared to the case of using a metal powder or a metal ribbon as in Example 2, it is easy to control the thickness of the metal thin film, and since the metal thin film is fixed to the surface of the ribbon 13, the ribbon There is an advantage that handling of 13 becomes easy.

  In addition, since melting | fusing point of aluminum is 660 degreeC, when forming the laminated body 31, you may join by the temperature more than melting | fusing point (for example, 700 degreeC) and the hot press of pressure 10MPa. In this case, since aluminum melts, the bonding strength can be increased.

[Modification]
As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example at all, and as long as it belongs to the technical scope of this invention, it cannot be overemphasized that various forms can be taken.

  For example, in each of the above-described embodiments, the configuration in which the four strips 13 are stacked to form the stacked body 31 is illustrated, but three or less or five or more strips 13 may be stacked, The piece of material 33 may be formed by using a single ribbon 13 without being laminated.

  When the material piece 33 is formed by one piece of the ribbon 13, the thickness of the ribbon 13 may be the same as the thickness of the material piece 33. When laminating a plurality of ribbons 13, the ribbons 13 having the same thickness may be laminated, or the ribbons 13 having different thicknesses may be laminated.

  When the number of laminated layers required for forming one laminated body 31 is increased, the thickness of the ribbon 13 is reduced, and the time required for the heat treatment in the heat treatment step for reducing the ratio of α-Fe is increased. Can be shortened. On the other hand, as the strip 13 is thicker, the number of stacks can be reduced and the stacking process can be simplified.

  Moreover, in the said Example 1, although the structure which joins the ribbon 13 using the conductive adhesive 51 was illustrated, although the heat conductivity of the laminated body 31 may fall, it has electroconductivity. You may join using the adhesive which is not. For example, an epoxy adhesive, a rubber adhesive, a cyanoacrylate adhesive, or the like can be used. In order to suppress a decrease in thermal conductivity, the adhesive layer may be thinned.

Moreover, as the adhesive 61 used for laminating the material pieces 41, a conductive adhesive may be used, or an adhesive having no conductivity may be used.
Moreover, in the said Example 2, although the structure which uses copper as the metal powder 53 or the metal thin strip 55 was illustrated, metals other than copper may be used. However, it is preferable to use one having a low melting point.

  In addition, the bonding layer 71 formed by the vapor deposition apparatus in Example 3 may be formed of a metal other than aluminum. Further, a metal thin film may be formed by a sputtering method or a plating method using a sputtering device or a plating device instead of the vapor deposition device. When using a plating apparatus, it is conceivable to use copper instead of aluminum.

  Further, in each of the above embodiments, the configuration in which the strip 13 and the material piece 33 have the same width is illustrated, but the width of the strip 13 is formed wide and cut to obtain the width of the target piece 33. You may comprise. In this case, although the number of steps for cutting increases, the accuracy of the width can be increased.

  Moreover, in each said Example, although the structure which performs the heat treatment process after producing the strip 13 by melt | dissolution quenching was illustrated, the timing which performs a heat treatment process is not specifically limited. However, it is preferable to carry out before these steps so as not to release the bonding in the laminating step or the assembling step. Moreover, it is preferable to carry out before the hydrogen absorption step so that hydrogen absorbed in the hydrogen absorption step is not separated.

DESCRIPTION OF SYMBOLS 11 ... Powder raw material, 13 ... Thin strip, 15 ... Nozzle, 17 ... Molten metal, 19 ... Rotary roll, 23 ... Heater, 31 ... Laminated body, 33 ... Material piece, 37 ... Heater, 41 ... Material piece, 43 ... Micro Channel heat exchanger, 51 ... conductive adhesive, 53 ... metal powder, 55 ... metal ribbon, 61 ... adhesive, 63 ... press, 71 ... bonding layer

Claims (11)

An alloy production process for producing a ribbon-shaped alloy (13) by quenching a molten metal of a magnetic refrigeration material containing La, Fe, and Si with a cooling roll;
A groove forming step of forming a groove in the ribbon-shaped alloy produced by the alloy production step;
An assembly step of laminating the ribbon-shaped alloy having grooves formed by the groove forming step, and forming a heat exchanger (43) having the grooves as flow paths;
And a heat treatment step of increasing the La (FeSi) ₁₃ phase by heat-treating the ribbon-like alloy. A method for manufacturing a magnetic refrigeration material heat exchanger. A lamination step of producing a plate-like member (31) formed by laminating the ribbon-like alloy produced by the alloy production step;
The groove forming step is a step of forming a groove in the plate-like member produced by the laminating step,
The method for manufacturing a magnetic refrigeration material heat exchanger according to claim 1, wherein the assembling step is a step of laminating the plate-like member (41) having grooves formed by the groove forming step. The method of manufacturing a magnetic refrigeration material heat exchanger according to claim 2, wherein the laminating step is a step of joining and laminating the ribbon-shaped alloy with an adhesive (51). The method for manufacturing a magnetic refrigeration material heat exchanger according to claim 3, wherein the adhesive is a conductive adhesive. The method of manufacturing a magnetic refrigeration material heat exchanger according to claim 2, wherein the laminating step is a step of joining and laminating the ribbon-shaped alloy by pressure bonding. In the laminating step, a bonding material containing at least one of the metal powder (53) and the metal ribbon (55) is disposed between the ribbon-like alloys and is bonded via the bonding material. The method for producing a magnetic refrigeration material heat exchanger according to claim 5, wherein the step is a step of joining and laminating the ribbon-like alloys. The said lamination process is a process of forming a metal thin film (71) on the surface of the said strip-shaped alloy, and joining and laminating the said strip-shaped alloys through the said metal thin film. 6. A method for producing a magnetic refrigeration material heat exchanger according to 5. The manufacturing method of the magnetic refrigeration material heat exchanger according to claim 7, wherein the metal thin film is formed by any one method selected from the group consisting of a vapor deposition method, a sputtering method, and a plating method. Method. In the laminating step, a metal material having a melting point that is lower than the heat treatment temperature in the heat treatment step is disposed between the ribbon-like alloys, and is crimped by hot pressing at a temperature lower than the heat treatment temperature and higher than the melting point. The method for producing a magnetic refrigeration material heat exchanger according to claim 5, wherein the method is a step of laminating. A heat exchanger (43) having microchannels using magnetic refrigeration material, comprising:
A plate-like magnetic refrigeration material (41) formed by laminating a ribbon-like alloy (13) containing La, Fe, and Si, wherein the plate-like groove is formed with a groove serving as a flow path on one of its main surfaces. A magnetic refrigeration material heat exchanger characterized by being laminated with a magnetic refrigeration material. The plate-like magnetic refrigeration material is formed by laminating the ribbon-shaped alloy and an adhesive (51) layer or a metal (53, 55, 71) layer. A magnetic refrigeration material heat exchanger according to claim 1.