Magnetic Field Sources - Magnetocaloric Energy Conversion: From Theory to Applications - page 75

Fig. 3.33 Design of static coaxial permanent-magnet assemblies for a rotating AMR, a a solution
without an outer soft iron shield (see Egolf et al. [ 44 ], Vuarnoz et al. [ 45 ]), b a solution with an
outer shield, without showing the inner static part (see Egolf et al. [ 46 ])

shielding is not provided in a direction that is perpendicular to the surface plane of
the magnet (direction of observer of Fig. 3.32 ).
Another class of static permanent magnets is shown in Figs. 3.33 and 3.34 .In
this case, the magnetocaloric material, in the form of a rotating cylinder, is posi-
tioned between two static coaxial cylinders, which represent a soft magnetic
material for the guidance of the magnetic ux. The magnet assembly in Fig. 3.33 a

was designed by the team from the University of Applied Sciences of Western
Switzerland (UASWS); it was

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rst presented in a study for the Swiss Federal Of ce

of Energy (SFOE) in 2008 [ 44 ], and later in the article of Vuarnoz et al. [ 45 ].
In the solution in Fig. 3.33 a, the outer ring made of soft magnetic material can be
added with a slight modi cation of the direction of the magnetization of permanent

magnets. A similar design was presented by the same team (UASWS) in 2009 in
another study for the SFOE (Fig. 3.32 b) [ 46 ].
Later in 2010, the team from the DTU

Risoe presented a similar solution to the
previous two, with the difference that both the inner and the outer static cylinders
would represent a magnet assembly [ 47 , 48 ]. This magnet assembly is shown in
Fig. 3.34 . The angles of the magnetization of the magnets were assumed and
approximated by the authors of this topic. A maximum magnetic

—

ux density of
1.24 T was obtained in the regions shown by the red arrow in Fig. 3.34 .
Note that all the magnet assemblies presented in Figs. 3.33 and 3.34 can have
different magnetic

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ux densities, which can be controlled in the design by the
thickness of the magnetocaloric cylinder, as well as the diameters of the outer and the
inner static parts of the magnet assembly. Therefore, such an approach enables scaling
of device from a few watts to kilowatts of cooling power. For instance, three different
designs of the magnet assembly in Fig. 3.33 b were performed in the study of Egolf
et al. [ 46 ], i.e. for 1, 1.5 and 2 T, respectively. The dimensions of the outer diameter of
the magnet assembly in this case were taken to be 400 mm for all the three cases,
whereas the inner static soft iron part (not shown in Fig. 3.33 b would have a diameter

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