Design Issues and Future Perspectives for Magnetocaloric Energy Conversion - Magnetocaloric Energy Conversion: From Theory to Applications - page 333

Fig. 8.6 A simpli ed cascade magnetocaloric device based on the linear operating principle with
moving magnetic eld sources (a upper AMRs magnetized, lower AMRs demagnetized; b upper
AMRs demagnetized, lower AMRs magnetized)

done in a similar way as in conventional double-stage refrigerators, where the
condenser of the rst unit is coupled with the evaporator of the second unit.

As one can see, the transfer of heat between the lower and upper stages is usually
provided by the counter-

ow heat exchanger. In the ideal case, the inlet temperature
on the warm side would equal the inlet temperature at the cold side. If one removes
the intermediate heat exchanger then a new con

fl

guration can be obtained, as shown

in Fig. 8.6 .
As can be seen from Fig. 8.6 , when a cascade system is required to produce a
larger temperature span between the heat source and the heat sink, but the AMR
principle is applied, then the intermediate heat exchangers between the two stages
are actually not required. The reason for this is the fact that the AMRs already
provide the regeneration of the heat and therefore the temperature span. From the
point of view of design and also ef

ciency, it makes sense to actually have a single
and longer AMR instead of two shorter AMRs, such as shown in the case of
Fig. 8.6 . In this way one can avoid any potential dead volume, heat transfer and heat
losses (gains) and other losses, related, e.g. to additional viscous losses, magnetic
fl ux leakage, etc.