Environmental Engineering Reference
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Fig. 3.34 Design of a static
coaxial permanent-magnet
assembly for a rotating AMR
(see Bj
ø
rk et al. [
47
,
48
])
—
—
—
of 180 mm (thickness
gap
of the magnetocaloric ring 34 mm), 166 (thickness
—
—
—
gap
of the magnetocaloric ring 18 mm) and 150 mm (thickness
gap
of the
magnetocaloric ring 6.2 mm), respectively.
3.4.3 Rotary Halbach (2D) and Simple (2D) Magnet
Assemblies
A static AMR in a magnetic refrigerator or a magnetic heat pump offers the pos-
sibility of a substantial reduction of losses compared to a rotating AMR. These
losses in the latter relate to the friction of dynamic seals (and related heating),
internal (or even external if the device is not well designed) leakage of the working
fl
uid, which occurs between the static piping part and the rotating AMR.
Therefore, the rotation of a magnetic
eld over a static magnetocaloric material
represents a more ef
cient solution. The simplest way to perform this in rotary
devices is simply by taking a double Halbach magnet array, as shown in Fig.
3.35
.
This was actually done by Tura and Rowe [
49
,
50
], who applied a double Halbach as
the 1.34 T magnetic
eld source for a magnetic refrigerator. This kind of approach
was also studied by Bj
rk et al. [
51
] as well as by Bouchekara and Nahas [
52
].
According to Fig.
3.35
, the inner array rotates with respect to the stationary outer
array. When the magnetic
ø
ux density vector within the space between the two
arrays is aligned, this will provide the ON-operation of the magnetic
fl
eld source, by
summing the individual inductions of each array (Fig.
3.35
a). When the inner array
is rotated by 180
°
ux density vectors of the outer and inner ring
cancel each other, thus, resulting in the minimum low-
the magnetic
fl
eld state (Fig.
3.35
a).
In 2014, Arnold et al. [
53
] presented a triple Halbach array (Fig.
3.36
), which
represented a further optimization of the previously [
49
,
50
] constructed double
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