High Porosity Particulate Beds Structurally Stabilized by Epoxy
The present invention provides a porous thermal regenerator apparatus and method of making a porous thermal regenerator comprised of metallic or intermetallic particles that are held together in a porous three dimensional network by a binding agent (such as epoxy). One aspect of the apparatus is that the porosity of the porous thermal regenerator is greater than the tapped porosity of the particles comprising the porous thermal regenerator; moreover, the high-porosity apparatus is durable, that is, it remains intact when exposed to strong time-varying magnetic forces while immersed in aqueous fluid. This high porosity, when combined with high strength and aqueous heat transfer fluid stability, leads to improved porous thermal regenerators and concomitantly to magnetic refrigerators with improved performance.
1 . A method of fabricating a thermal regenerator having one or more layers comprising the following steps:
(a) mixing a plurality of magnetocaloric particles and a binding agent to form a moldable porous mass;
(b) transferring a predetermined weight of the moldable porous mass to a mold;
(c) distributing the moldable porous mass to fill a cross-section of the mold such that the moldable porous mass extends to a substantially constant predetermined height within the mold defining a desired volume to form a layer;
(d) mixing a second plurality of magnetocaloric particles, distinct from the first plurality of magnetocaloric particles, and a binding agent to form a second moldable porous mass;
(e) repeating steps (b)-(e) with a second predetermined weight of the second moldable porous mass distributed to extend to a second substantially constant desired height within the mold defining a second predetermined volume; and
(e) allowing the binding agent to harden within the mold to form a hardened mass.
2 . The method of claim 1 further comprising the following steps which precede step (a):
agitating the plurality of magnetocaloric particles while in contact with an aqueous detergent solution;
filtering the aqueous detergent solution from the particles; and
rinsing and filtering the aqueous detergent solution from the particles.
3 . The method of claim 1 further comprising the following steps which precede step (a):
agitating the plurality of magnetocaloric particles while in contact with a non-aqueous solvent;
filtering the non-aqueous solvent from the particles; and
rinsing and filtering the non-aqueous solvent from the particles.
4 . The method of claim 1 further comprising the step of applying an organosilane film to the plurality of particles before step (a).
5 . The method of claim 1 further comprising the following steps between step (a) and step (b):
forming clusters of particles from the moldable porous mass; and
collecting the clusters of particles and adding secondary binding agent to form a new moldable mass.
6 . The method of claim 5 further comprising the following steps which precede step (a):
agitating the plurality of magnetocaloric particles while in contact with an aqueous detergent solution;
filtering the aqueous detergent solution from the particles; and
rinsing and filtering the aqueous detergent solution from the particles.
7 . The method of claim 5 further comprising the following steps which precede step (a):
agitating the plurality of magnetocaloric particles while in contact with a non-aqueous solvent;
filtering the non-aqueous solvent from the particles; and
rinsing and filtering the non-aqueous solvent from the particles.
8 . The method of claim 5 further comprising the step of applying an organosilane film to the plurality of particles before step (a).
9 . A method of fabricating a thermal regenerator having one or more layers which includes the steps of:
(a) mixing a plurality of magnetocaloric particles and a primary binding agent to form a porous mass;
(b) forming clusters of particles from the porous mass and at least partially curing the clusters; and
(c) collecting the partially cured clusters of particles and adding a secondary binding agent into a larger mass to form a new porous mass.