Active Magnetic Regeneration - Magnetocaloric Energy Conversion: From Theory to Applications - page 152

Fig. 4.34 Photograph of Gd in different forms. a Spheres with a diameter of approximately
0.4 mm. b Cylinders with a length of 4 mm and a diameter of 2.5 mm. c Plates with a thickness of
0.25 mm. d Powder with an average size of 0.4 mm

should be avoided. Namely, during the (de)magnetization process the particles will,
if not xed, move, and cause friction. It should also be noted that the shape of the

particles signi cantly affects the uniformity of the porosity. The powder, for

example has, in addition to spheres, more than one spatial degree of freedom.
Therefore, it can be randomly oriented inside the AMR and its porosity would be
higher and less homogenous compared to the spheres.
There are a few techniques applied for the fabrication of parallel-plate AMRs
based on thin Gd plates. In general, they can be divided into two groups: the AMRs
with a spacing integrated into the housing and the jointed AMR. An example of the

131 ] and is schematically shown in Fig. 4.35 .
The magnetocaloric plates are inserted into the housing with integrated spacings
(space dividers). The main disadvantage of this method is the limit in the spacing
thickness, as it cannot be fabricated as thin as would be necessary for more ef

rst one can be found in, e.g. [ 129 -

cient

heat transfer (<0.1 mm).
The jointed AMRs are based on magnetocaloric plates and narrower plates
(ribbon) that work as the spacing between the plates (see Fig. 4.35 b). In this case,
we are not limited by the spacing thickness. The magnetocaloric plates and the