Design Issues and Future Perspectives for Magnetocaloric Energy Conversion - Magnetocaloric Energy Conversion: From Theory to Applications - page 344

Fig. 8.17 A magnetocaloric
device with a rotary
movement of the magnet
assembly over two static
AMRs with the application of
the switching valve system
and the uni-directional pump
(a upper AMR magnetized,
lower AMR demagnetized; b
upper AMR demagnetized,
lower AMR magnetized),
classication no: R20(3)1(5)
(6)01101(12)

(stator) and the rotary part (rotor) (Fig. 8.18 b). The simplest case for the latter is to
apply a double or triple Halbach structure. However, this will not be the most cost-
effective solution. A more effective solution can be provided by the rotation of the
magnetic

eld source, such as, for example, shown in Fig. 8.19 .
According to Fig. 8.19 (left), a four-pole rotating magnet provides for the
magnetization and demagnetization of eight AMR beds. Such a magnet assembly
can be simply designed to be longer in the case of axial ow (parallel to the

rotation axis), when a longer AMR is required. This certainly represents a simpler
construction over applications with a radial or azimuth

fl uid fl

ow through the AMR.
This is especially so if the up-scaling of devices is required. In Fig. 8.19 (right)
another example is shown in which the two-pole magnet is applied. In this case we
show two different examples of the magnetization of AMRs. However, in most
cases such an arrangement will provide a smaller magnetic

fl uid fl

fl ux density than in the

case of Fig. 8.19 (left).
Another very important issue that needs to be addressed in the case of rotating
magnetic eld sources is to follow the design and knowledge from permanent

magnet motors. Such an example is shown in the two cases of Fig. 8.20 .
In the cases a

c for Fig. 8.20 , we can follow the knowledge on the design of
permanent magnet motors in order to provide an ef

-

cient solution for the magnetic

fl ux density in

such a particular case of multiple pole magnets will be, in most cases, low.
Therefore, compared to permanent magnet motors, the design architecture should
be modi

ux distribution as well as to minimize the torque. The magnetic fl

ed for application of magnetic refrigeration.