Overview of Existing Magnetocaloric Prototype Devices - Magnetocaloric Energy Conversion: From Theory to Applications - page 271

temperature span of 23 K. In a lower magnetic eld of 1 T, a speci c cooling power

of 18.2 W kg − 1 was obtained for a temperature span of 11 K.
In 2005 researchers from Hokkaido University presented their

rst prototype in
the article by Kawanami et al. [ 12 ]. It was a Gd packed-bed AMR with a perma-
nent-magnet assembly that produced a magnetic eld of 0.9 T. The heat-transfer

fl uid was air. In 2007 Kawanami [ 13 ] presented an improved device. The Gd

particles of 0.6 mm diameter were lled in a packed bed with a total packing mass

of 62 g. A magnetic eld of 1 T was provided by a permanent magnet. The highest

possible operating frequency was approximately 0.35 Hz. The heat-transfer uid

used was distilled water. The maximum temperature span achieved was approxi-
mately 12 K.
Later, in 2008, a joint paper was published by researchers from Hokkaido
University, Kobe University and Kushiro National College of Technology by
Nakamura et al. [ 14 ]. Their device consisted of 33.4 g of Gd spheres packed in an
AMR, using a permanent-magnet assembly with a magnetic

fl

eld of 2 T. They

applied water and air as the heat-transfer fl uids. In the case of air as the heat-transfer

fl uid, the maximum no-load temperature span was 7 K, whereas with water, the

temperature span was increased to 21 K.
A year later, in 2009, another prototype was built in a joint project involving the
above-mentioned institutions by Hirano et al. [ 15 ]. They presented a reciprocating
device where a static permanent-magnet assembly was magnetizing and demag-
netizing a moving AMR bed with a magnetic

eld of 2.3 T. They tested AMRs with

La Si spheres having diameters of 1.6, 1 and 2 mm. In additional tests they also

experimentally evaluated an AMR consisting of Gd spheres with a diameter of
0.6 mm. The total mass of each AMR was 12, 13, 15 and 33 g, respectively. The
applied heat-transfer

Fe

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owing through all four AMRs was air. The highest no-
load temperature span was achieved with the gadolinium-based AMR and was
equal to 4.2 K. The highest no-load temperature span of the La

fl uid fl

Si AMRs was
achieved with the smallest diameter of spheres. This temperature span was 3.7 K. In
the case of spheres with a diameter of 1.6 mm, a 3.1 K of temperature span was
obtained, while in the case of the largest spheres of 2 mm, the temperature span was
2.7 K.
Table 7.3 presents the reciprocating magnetocaloric device designed by Toshiba
Corporation in 2006.

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7.1.4 Chinese Prototypes

In the past decade, China became one of the most active countries regarding the
number of research papers as well as the number of prototypes for magnetic
refrigeration devices. The

rst recorded Chinese reciprocating prototypes were

presented in 2005 at the rst International Conference on Magnetic Refrigeration at

Room Temperature in Montreaux, Switzerland [ 16 , 17 ].