Active Magnetic Regeneration - Magnetocaloric Energy Conversion: From Theory to Applications - page 157

4.8 Where Is the Limit for Applying a Conventional
AMR Cycle?

It is well known that large temperature differences between the uid and the

magnetocaloric material lead to large irreversible heat transfer losses. This is why
researchers tend to improve the heat transfer characteristics of the AMR.
Therefore, the limit of the AMR cycle is given by the applied mechanism of heat
transfer (together with the modest magnetocaloric effect in known magnetocaloric
materials). Even though the magnetocaloric material has a

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ne porous structure,
with a high thermal conductivity and a large heat transfer area, all the experimental
results and numerical calculations indicate (see e.g. [ 15 , 37 , 146 ]) that such solu-
tions will not lead to compact devices. The compactness has a strong correlation
with the cost of a device. Furthermore, low porous structures with a very high heat
transfer surface lead to pump losses and heat generation due to the uid friction.

Therefore, we can expect that future applications will not necessarily apply a
conventional AMR, or the AMR will by integrated together with some other
mechanisms to increase the heat transfer rate, for example thermal diodes. Because
of their importance we dedicated a whole chapter to thermal diodes in this topic.

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