Environmental Engineering Reference
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8.3 Static AMR Magnetocaloric Devices
Currently, there exists no practical solution for the application of a permanent-
magnet assembly that would apply static switching of the high and low magnetic
eld region. This could be performed by temperature gradients, but the risk of
demagnetizing the magnet as well as the slow heat transfer process associated with
such a principle will not lead to a practical solution.
There are, however, ideas that have been recently published by Bali et al. [
2
].
They found that the rotation of a single crystal of the anisotropic HoMn
2
O
5
alloy in
a constant
eld of 7 T led to rather high isothermal entropy change. Despite the fact
that this kind of solution is actually related again to the movement of the mag-
netocaloric material (rotation for a certain angle with respect to the magnetic
ux
direction), the working principle applies the anisotropy of the magnetocaloric
material and does not really change in the external parameters.
In this section we therefore focus only on the application of resistive and
superconducting magnets. An example of such a system with two static magnetic
fl
eld sources and two static AMRs is shown in Fig.
8.24
.
Imagine the application of the bi-directional pump. An ON-OFF operation of the
magnetic
eld source provides magnetization and demagnetization of AMRs. To
this process the bi-directional pump is synchronized, which in the case of the AMR
Brayton-like cycle switches immediately after the process of magnetization or
demagnetization is performed. A major advantage of such a system is that, besides
the pump system and related
fl
uid
fl
ow, there is no need for moving parts. However,
Fig. 8.24 Application of an ON-OFF operation for the static magnetic eld source over the static
AMRs, classication no: R21(3)2(5)(6)00002
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