Overview of Existing Magnetocaloric Prototype Devices - Magnetocaloric Energy Conversion: From Theory to Applications - page 265

Chapter 7
Overview of Existing Magnetocaloric
Prototype Devices

Since Brown [ 1 ] built the rst magnetic refrigerator prototype working near room

temperature in 1976 there has been a large number of different prototypes [ 2 ]
designed and built over the past 40 years. However, despite there being 4 decades of
scienti eld of magnetocaloric energy conversion near room tem-

perature, the technology is only now at the brink of commercialization. With every
new prototype that is built, we see slow but measureable improvements toward the
desired goal. Figure 7.1 shows the number of prototypes built until 2014. It is clear
that the number of prototypes increases with each new year, pointing to the fact that
the magnetocaloric energy conversion research community is expanding research
activities together with the S-curve of technology development.
The reasons why magnetocaloric technology near room temperature is only now
slowly becoming market-ready lie in the fact that there are a number of different
obstacles regarding the device

c input into the

nal-
izing the idea of commercializing magnetocaloric technology. Addressing all the
design issues is, of course, a dif

' s design, which need to be overcome before

cult task. With each prototype built researchers try
to solve different design issues, ranging from the heat-transfer problems of the
AMRs and the working uids, the design issues of the AMRs and magnet

assemblies, to the problems related to peripheral elements, such as pump and valves
systems. In this manner, each prototype built up until now has its own special
feature. Each of them is trying to address one or more of the engineering barriers,
but almost never a system as a whole.
However, there is one major characteristic that can be distinguished for all the
existing prototypes. There are two groups of devices, i.e. the ones operating in a
reciprocating (linear motion) manner and the others operating in a rotary manner.
The reciprocating and rotary operations of the magnetocaloric device are more or
less related to the way how the AMR is exposed to the alternating magnetic

fl

eld, as
is described in Chap. 4 on Active Magnetic Regeneration (see also Chap. 8 ). One
possibility is to move the AMR or the magnet in a reciprocal direction back and
forth, and the other is to rotate the AMR or the magnet. As you will see in the
following sections, each of the two methods has its pros and cons, depending on the
functionality of the device. Is it an experimental testing device? Or is it a real