Heat exchanger and method for making the same   

The magnetocaloric effect is a phenomenon whereby, for appropriately chosen materials (referred to as “magnetocaloric materials”), a change in the temperature of the material can be induced by exposing the material to a changing magnetic field. Specifically, increasing the magnitude of an externally applied magnetic field orders the magnetic moments within the material, increasing the temperature via the magnetocaloric effect. Conversely, decreasing the magnitude of the externally applied magnetic field disorders the magnetic moments within the material, reducing temperature via the magnetocaloric effect.

In one aspect, an apparatus, such as a heat exchanger, is provided. The apparatus can include a first tubular region that is substantially hollow. A second tubular region can be disposed adjacent to the first tubular region. For example, the first and second tubular regions can define respective elongated axes that are substantially parallel, with the first and second tubular regions being, say, juxtaposed. The first and second tubular regions can each have a dimension less than or equal to about 100 μm, and/or can each have an aspect ratio of at least five.

The first and second tubular regions can respectively include pluralities of first and second tubular regions tubular regions, with at least one first tubular region being adjacent to at least one second tubular region. In some embodiments, the first and second tubular regions may be arranged so as to form an array, for example, of alternating first and second tubular regions. In some embodiments, the first and second tubular regions can be disposed within a major passage defined by a major tubular structure. In other embodiments, the first and second tubular regions may be incorporated into a unitary structure.

The apparatus may include a first tubular structure that defines a first passage, with the first tubular region being defined by the first passage. The first tubular structure may include a plurality of first tubular structures that are arranged so as to define therebetween said second tubular region. Alternatively, or additionally, the apparatus may further include a second tubular structure that defines a second passage, with the second tubular region being defined by the second passage. The first and/or second tubular structures can be formed at least partially of copper, silver, aluminum, and/or a thermoplastic.

A first material can be disposed within the second tubular region. The first material can be granular, and may have a strain to failure of less than about 1% at room temperature. For example, the first material can be a magnetocaloric material. A second material may also be disposed within the second tubular region.

Where the first material includes magnetocaloric material, the apparatus may also include a magnetic field generating component configured to vary a magnetic field to which the magnetocaloric material is exposed. A working fluid can be directed through the first tubular region so as to exchange heat with the magnetocaloric material.

In another aspect, a method is provided, the method including providing a first tubular structure that defines a first passage. A sacrificial material can be disposed in the first passage. A second tubular structure can be provided so as to be adjacent to the first tubular structure, with the second tubular structure defining a second passage within which can be disposed a granular material. The first and second tubular structures can then be deformed (e.g., drawn, rolled, and/or swaged) together so as to reduce an external dimension of each of the first and second tubular structures, for example, by at least 50%. The sacrificial material can then be removed from the first passage, for example, through etching, melting, and/or decomposing the sacrificial material.

In some embodiments, a major tubular structure can be provided, the major tubular structure acting to define a major passage. The first and second tubular structures can be disposed within the major passage, and the first and second tubular structures can be deformed together with major tubular structure.

In yet another aspect, an apparatus, such as a heat exchanger, is provided. The apparatus can include a first tubular region with a sacrificial material and, in some cases, a second material, such as another sacrificial material, disposed therein. A second tubular region can be disposed adjacent to the first tubular region, with a first material being disposed in the second tubular region.

In still another aspect, a method is provided, the method including providing a major tubular structure defining a major passage. A first tubular structure can be provided, the first tubular structure that defines a first passage that has disposed therein sacrificial material. A first, granular material can be disposed in an area between the first tubular structure and the major tubular structure. The major and first tubular structures can be deformed together, and the sacrificial material can be removed.

In yet another aspect, a method is provided, the method including providing a plurality of first tubular structures, each of which defines a first passage. A sacrificial material can be disposed in each of the respective first passages. The first tubular structures can be configured so as to enclose therebetween an interstitial space, within which interstitial space can be disposed a first, granular material. The plurality of first tubular structures and the first, granular material can be deformed together, and the sacrificial material can be removed.

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of a heat exchanger configured in accordance with an example embodiment;

FIG. 2 is a perspective view of the heat exchanger of FIG. 1 sectioned along plane 2 of FIG. 1;

FIG. 3 is a perspective view of the heat exchanger of FIG. 1 sectioned along plane 3 of FIG. 1;

FIG. 4 is a partially exploded view of the heat exchanger of FIG. 3;

FIG. 5 is a perspective view of a heat exchanger configured in accordance with another example embodiment;

FIG. 6 is a perspective view of a heat exchanger configured in accordance with yet another example embodiment;

FIG. 7 is a perspective view of a heat exchanger configured in accordance with still another example embodiment;

FIG. 8 is a perspective view of a heat exchanger configured in accordance with yet another example embodiment;

FIG. 9 is a perspective view of a heat exchanger configured in accordance with still another example embodiment;

FIG. 10 is a perspective view of a heat exchanger configured in accordance with yet another example embodiment;

FIG. 11 is a perspective view of a heat exchanger configured in accordance with still another example embodiment;

FIG. 12 is a perspective schematic view of a magnetic refrigeration system configured in accordance with an example embodiment;

FIGS. 13-19 are schematic depictions of a method for making a heat exchanger, the method being in accordance with an example embodiment; and

FIGS. 20-24 are schematic depictions of a method for making a heat exchanger, the method being in accordance with another example embodiment.

DETAILED DESCRIPTION

Example embodiments of the present invention are described below in detail with reference to the accompanying drawings, where the same reference numerals denote the same parts throughout the drawings. Some of these embodiments may address the above and other needs.

Referring to FIGS. 1-4, therein is shown an apparatus, such as a heat exchanger 100, configured in accordance with an example embodiment. The heat exchanger 100 can include a first tubular region 102 and a second tubular region 104 adjacent to the first tubular region 102. The first and second tubular regions 102, 104 can define respective elongated axes a1, a2 that are substantially parallel. Each of the first and second tubular regions 102, 104 can have a dimension, such as a width w1, w2 measured transverse to the elongated axes a1, a2, that is less than or equal to about a few millimeters, and in some cases less than or equal to about 100 μm, and in other cases less than or equal to about 10 μm. Further, each of the first and second tubular regions 102, 104 can have an aspect ratio (e.g., length L divided by width w1 or w2) of anywhere from at least 5 to more than 1000.

The first tubular regions 102 can be substantially hollow so as to define respective passages 106 therealong, while a first material 108 can be disposed within the second tubular regions 104. The first material can be granular, and may be compacted within the second tubular regions 104 so as to substantially fill the second tubular regions. The granular first material 108 may include granules of any shape, including, for example, one or more of spherical, cubic, pyramidal, etc. Regardless of shape, the granules may have diameters less than or equal to about 100 μm, and in some cases less than or equal to about 50 μm. Caps 110 can be provided in order to enclose the first material 108 within the second tubular regions 104. The first material 108 can be relatively brittle, for example, exhibiting a strain to failure of less than about 1% at room temperature. In some embodiments, a multiple materials may be disposed within the second tubular regions 104. For example, a second granular material may be mixed with the granular first material 108. The second material, when included, may also be relatively brittle. In other embodiments, respective second tubular regions 104 may contain different materials.

The first and second tubular regions 102, 104 may have cross sections that are substantially geometrically similar. For example, the first and second tubular regions 102, 104 may define square or rectangular cross sections that are roughly similar to one another in size and shape. However, the first and second tubular regions 102, 104 need not have rectangular cross-sections, and need not have cross-sectional shapes similar to one another. For example, referring to FIG. 5, therein is shown a heat exchanger 200 configured in accordance with another example embodiment. The heat exchanger 200 can include first and second tubular regions 202, 204 that each have rectangular cross sections, but of differing aspect ratios. Again, the second tubular region 204 can include therein a granular material 208.

Referring to FIG. 6, in yet another example embodiment, a heat exchanger 300 can include first and second tubular regions 302, 304 that have different cross-sectional shapes from one another (e.g., rectangular and circular, respectively). Referring to FIG. 7, in still another example embodiment, a heat exchanger 400 can include first and second tubular regions 402, 404 that have again different cross-sectional shapes from one another. Here, the first tubular regions 402 have a star-shaped cross section. Respective second tubular regions 402 have one of a circular cross section or a rectangular cross section. By utilizing different shapes for the cross sections of the tubular regions, packing of the tubular regions can be optimized for different applications.

Referring again to FIG. 1, in one embodiment, the first and second tubular regions 102, 104 may be incorporated into a unitary structure. For example, the first and second tubular regions 102, 104 may be bores in a monolithic structure. However, referring to FIG. 8, therein is shown a heat exchanger 500 configured in accordance with another example embodiment. The heat exchanger 500 can include first tubular regions 502 that are substantially hollow, and second tubular regions 504 that are each adjacent to a first tubular region and include therein a first material 508. A major tubular structure 512 defining a major passage 514 can also be included. The first and second tubular regions 502, 504 can be disposed within the major passage 514. For example, a first tubular structure 516 may define a first passage 506 that in turn defines the first tubular region 502. A second tubular structure 518 may define a second passage 520 that in turn defines the second tubular region 504.

Referring to FIG. 9, therein is shown a heat exchanger 600 configured in accordance with another example embodiment. The heat exchanger 600 can include a plurality of hollow first tubular structures 616 that define therein respective first tubular regions 602. The first tubular structures 616 can be disposed within a major tubular structure 612. Second tubular regions 604 can then be defined in the spaces between the first tubular structures 616 and also in the spaces between the respective first tubular structures and the major tubular structure 612. Referring to FIG. 10, in another embodiment, the major tubular structure 612 is excluded, and the plurality of first tubular structures 616 are arranged so as to define therebetween the second tubular region 604.

In all of the previously described embodiments, the first and second tubular regions have been juxtaposed. Referring to FIG. 11, therein is shown a heat exchanger 700 configured in accordance with another example embodiment. The first and second tubular regions 702, 704 can be arranged in a nested arrangement (e.g., concentrically). A first tubular structure 716 may define a first passage 706, and a second tubular structure 718 may define a second passage in which the first tubular structure is disposed. A second tubular region 704 containing a material 708 may then be defined between the first and second tubular structures 716, 718.

Referring to FIGS. 1-4, the first material 108 may include a magnetocaloric material. Examples of magnetocaloric materials include, for example, Gd5(SixGe1-x)4, La(FexSi1-x)Hx, MnFeP1-xAsx, GdDy, and GdTb. Where magnetocaloric material is disposed in the second tubular region 102, the heat exchanger 100 may be utilised as a working fluid regenerator for a magnetic refrigeration system. For example, referring to FIG. 12, therein is shown a schematic depiction of a magnetic refrigeration system 830 configured in accordance with an example embodiment. The magnetic refrigeration system 830 can include a heat exchanger 800 having first and second tubular regions 802, 804. The first tubular region 802 can be substantially hollow, such that a working fluid 832 may be directed therethrough. The second tubular region 804 can include a magnetocaloric material 808. The working fluid 832 can be circulated between the heat exchanger 800 and a refrigerated compartment 834. A magnetic field generating component 836 can be configured to vary a magnetic field B to which the magnetocaloric material 808 is exposed. For example, the magnetic field generating component 836 can be a permanent magnet configured to move relative to the magnetocaloric material 808, or can be an electromagnet configured to generate a varying magnetic field. As the working fluid 832 is directed through the first tubular region 802, it can exchange heat with the magnetocaloric material 808, for example, cooling the working fluid. Thereafter, the cooled working fluid 832 can move into thermal contact with the refrigerated compartment 834 to receive heat therefrom.

In order to maximize the thermal performance of the magnetic refrigeration system 830, efficient thermal contact may be facilitated between the working fluid 832 in the first tubular region 802 and the magnetocaloric material 808 in the second tubular region 804. In embodiments where each of the adjacent first and second tubular regions is defined by a tubular structure (e.g., as depicted in FIG. 8), the tube wall of the first and second tubular structures may be configured to have a thickness less than or equal to a few centimeters, and in some cases as little as about 0.01 mm.

In some embodiments, the heat exchanger 800 can be configured such that 50-90% of the overall cross-sectional area of the heat exchanger (i.e., the area of the surface opposing the flow of working fluid 832) is consumed by magnetocaloric material 808. Generally, the operation of the heat exchanger 800 will be enhanced by proportionately higher concentrations of magnetocaloric material in the heat exchanger. In other embodiments, the heat exchanger 800 can be configured such that at least 70% of the overall cross-sectional area of the heat exchanger is consumed by magnetocaloric material 808, with about 25% being consumed by hollow areas for channeling working fluid flow, and another 5% being consumed, for example, by the structures defining the first and second tubular regions 802, 804.

Referring to FIGS. 13-19, therein is schematically depicted a method for making an apparatus, such as the heat exchanger 100 of FIG. 1, the method being in accordance with an example embodiment. Initially, one or more first tubular structures 916 may be provided (FIG. 13), which first tubular structures respectively define first passages 906. One or more second tubular structures 918 can also be provided (FIG. 13), which second tubular structures respectively define second passages 920. Sacrificial material 940 can be disposed in the first passage 906, while a granular material 908 can be disposed in the second passage 920 (FIG. 14). The first and second tubular structures 916, 918 can then be sealed so as to enclose the sacrificial and granular materials 940, 908, respectively (FIG. 15). The first and second tubular structures 916, 918 can then be placed adjacent to one another (e.g., so as to form an array) and, in some cases, disposed in the major passage 914 defined by a major tubular structure 912 (FIG. 16).

The first and second tubular structures 916, 918 can then be deformed together (say, along with the major tubular structure 912) so as to reduce an external dimension of each of the first and second tubular structures (FIGS. 17 and 18). For example, the first and second tubular structures 916, 918 can be subject to one or more of drawing, rolling, or swaging in order to reduce the sizes of the first and second tubular structures in a transverse direction (i.e., a direction perpendicular to the drawing, rolling, or swaging direction). In some embodiments, the first and second tubular structures 916, 918 can have respective transverse dimensions W1 and W2 prior to being deformed, and following deformation can have respective transverse dimensions w1<0.5 W1 and w2<0.5 W2. In other embodiments, the first and second tubular structures 916, 918 can have respective transverse dimensions W1 and W2 prior to being deformed, and following deformation can have respective transverse dimensions w1<0.01 W1 and w2<0.01 W2. Generally, conventional drawing/swaging procedures can affect a reduction in cross section of a few orders of magnitude, with a concomitant increase in length. In order to facilitate the deformation process, the first and second tubular structures 916, 918 can be formed of one or more materials that are amenable to being deformed. For example, in some embodiments, the first and second tubular structures 916, 918 can be formed of copper, silver, aluminum, and/or a thermoplastic.

Following deformation of the first and second tubular structures 916, 918 the sacrificial material 940 can be removed from the first passages 906 to produce a heat series of adjacent tubular structures that either include either granular material 908 or define passages 906 that are hollow (FIG. 19). For example, the deformed first and second tubular structures 916, 918 can be cut so as to expose the sacrificial material 940 (and the granular material 908), and the sacrificial material can be, say, etched, melted, dissolved, and/or decomposed. In order to facilitate the sacrificial material removal process, the sacrificial material 940 can be formed of one or more materials that are amenable to being removed through a feasible procedure. For example, in some embodiments, the sacrificial material 940 may be formed of wax, gypsum, sodium chloride (NaCl), and/or camphor.

Once the sacrificial material 940 has been removed from the first tubular structures 916, the first and second tubular structures 916, 918 together may form a heat exchanger 900 with fluid conduits formed integrally therein (i.e., the hollow passages 906). It is noted that the first and second tubular structures 916, 918 may be cut to any desired length (e.g., to a length ranging from about 0.1 mm to a few centimeters). As mentioned, when cutting the first and second tubular structures 916, 918 may, both the sacrificial material 940 and the granular material 908 may be exposed. However, either during the sacrificial material removal process or during ultimate use of the heat exchanger 900, it may be desirable to protect the granular material 908 from exposure to the surrounding environment. In such cases, the ends of the second tubular structures 918 can be covered/protected by chemically inert coatings/barriers.

The above-described process may enable the manufacture of components having relatively complex geometries and formed substantially of brittle materials. Such materials are typically challenging to machine or otherwise shape. By utilizing the brittle materials in granular form and enclosing the granules in another, more ductile material, relatively complex geometries can be formed. It is noted that the first, second, and major tubular structures 912, 916, 918 could, in some embodiments, be replaced by a monolithic structure through which a series of bores may be formed, which bores could then be respectively filled with granular material and sacrificial material. Further, a drawing/swaging process may, in some embodiments, result in a higher density than would otherwise be realizable for structures formed of granular materials. Finally, where the brittle material is a magnetocaloric material, a drawing/swaging process may, in some embodiments, result in a magnetocaloric material with a microstructure consisting of grains that are elongated in the drawing/swaging direction, which aspect may enhance the magnetocaloric properties of the material.

It is noted that the major tubular structure 912 may be excluded in some cases. In such embodiments, the deformation of the first and second tubular structures 916, 918 may act to bind these structures together, either through a physical interlocking of the tubes or due to reactions between or localized melting of the tubes.

In some embodiments, the deformation process may be facilitated through the use of a granular material 908 having granules with generally regular surface profiles, such that the surfaces of the granules lack asperities, protrusions, sharp indentations, etc. (other than nanometer and/or atomic level roughness). For example, this may allow the granules to flow past one another more readily, thereby helping to avoid instances of unusually low density and/or voids therein. In order to produce granules having a sufficiently smooth surface, the granules may be subjected to an isotropic chemical etch, which will tend to preferentially etch more pronounced surface features.

Referring to FIGS. 20-24, in another embodiment, a major tubular structure 1012 defining a major passage 1014 can be provided, along with a first tubular structure 1016 that defines a substantially hollow first passage 1006 (FIG. 20). Sacrificial material 1040 can be disposed in the first passage 1006 (FIG. 21), and granular material 1008 can be disposed in an area between the first tubular structure 1016 and the major tubular structure 1012 (FIGS. 22 and 23). The major and first tubular structures 1012, 1016 can then be deformed together to reduce an external dimension thereof, and the sacrificial material 1040 can be removed.

Referring again to FIGS. 13-19, in still other embodiments, the major and second tubular structures 912, 918 may both be excluded. For example, one or more first tubular structures 916 can be provided, each first tubular including therein a sacrificial material 940. The first tubular structures 916 can then be configured so as to enclose therebetween an interstitial space containing granular material (e.g., as depicted in FIG. 10). The first tubular structures 916 and the granular material enclosed therebetween can then be deformed together, with the deformation process causing the first tubular structures to bind together. Finally, the sacrificial material 940 can be removed.

While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.