Design Issues and Future Perspectives for Magnetocaloric Energy Conversion - Magnetocaloric Energy Conversion: From Theory to Applications - page 360

Table 8.2 Predicted general features of future magnetocaloric devices depending on the
frequency of the operation (number of thermodynamic cycles per unit of time)
Target market/target of design Frequency

1 Hz 5 Hz 10 Hz 20 Hz 50 Hz

AMR

✔ ✔

Thermal diode mechanism

✔ ✔ ✔

AMR with liquid metal ✔ ✔

advanced working uids, e.g. liquid metals, the frequency could be increased up to

10 Hz. All the higher frequencies of operation will demand the application of a
thermal diode or similar mechanisms.
Table 8.1 shows the potential future magnetocaloric devices related to the
magnetic

fl

eld source. It is based on present knowledge with respect to magnet-
ocaloric energy conversion. As can be seen from Table 8.1 , we can expect that
magnetic refrigerators, magnetic air conditioners, magnetic heat pumps and mag-
netic chillers, whose cooling or heating power will be in a range below 300 kW,
will most probably apply permanent magnets. However, for large-scale units,
including the power generation, a superconducting magnetic eld source will be

applied.
Another example is shown in Table 8.2 . This shows the frequency dependence
of three different applications that relate to a magnetocaloric material, its geometry
and operation: basic AMR principle, the AMR principle with advanced working
fl

uids (e.g., with liquid metals) and the principle of AMR combined with the
thermal diode mechanism. This table predicts magnetocaloric energy conversion
that enables high ef

ciencies and certain temperature spans that are comparable
with conventional compressor-based refrigeration.
As can be seen from Table 8.2 , the basic AMR principle with water-based uids

or similar will most probably not bridge the frequency of the operation of 5 Hz. Of
course, a high frequency with such devices will be possible, but their ef

fl

ciency and
also the restricted temperature span will represent too large an obstacle with respect
to conventional devices. The solution with liquid metals and the AMR principle is
actually more cost-effective and more energy ef

cient solution than that of the

application of conventional uids.

Thus we may expect such solutions to enable doubling of the power at the same

fl

ef uids, for instance,

water. For high frequencies of operation above 10 Hz, the present knowledge shows
that only solutions with thermal diode mechanisms can lead to such applications.
These, in contrast to other AMR principles, can also apply conventional refrigerants
and can even operate in a similar manner as heat pipes. Note that the application of
a thermal diode mechanism will not be perfect for frequencies of operation below,
e.g. 5 or 10 Hz. We hope again that the research community will be encouraged by
this topic to enter into design of magnetocaloric devices with thermal diode
mechanisms.

ciency with respect to solutions of AMR with conventional fl