Overview of Existing Magnetocaloric Prototype Devices - Magnetocaloric Energy Conversion: From Theory to Applications - page 279

magnetic uids. These are all fundamental and important

parameters, which may give a useful and systematic study for the further research
and design of magnetic refrigeration prototypes.
In 2009 Engelbrecht et al. [ 28 ] presented the performance of two AMRs: a

elds and heat-transfer fl

at-
plate Gd-based AMR and a two-layered AMR consisting of La(Fe,Co,Si) 13 plates.
The device on which the experiments were carried out was the same as in Bahl et al.
[ 27 ], with the exception that in the last case, instead of the electromagnet a per-
manent-magnet Halbach assembly was applied. The magnet assembly provided a
magnetic

fl

uid was a mixture of 75 % water and
25 % of automotive anti-freeze. This anti-freeze was used for two purposes: it acted
as a corrosion inhibitor and as a

eld of 1.03 T. The heat-transfer fl

C. The Gd and
La(Fe,Co,Si) 13 plates were 0.9 mm thick with a spacing of 0.5 mm. The two layers
of the La(Fe,Co,Si) 13 material had Curie temperatures of approximately 276 and
289 K. The maximum no-load temperature span of the Gd-based AMR was about
9 K, whereas in the two-layered AMR a temperature span of approximately 6.5 K
was obtained. The reason for the smaller temperature span was the large

fl uid with a freezing point below 0 °

“ tem-

perature gap between the two Curie temperatures.

Two years later (in 2011) Engelbrecht et al. [ 29 ] presented the results of another
study on the experimental device described above [ 28 ]. Here,

”

ve different mag-
netocaloric materials were tested. These materials were Gd, three different La(Fe,Co,
Si) 13 materials and a ceramic magnetocaloric material, La 0.67 Ca 0.26 Sr 0.07 Mn 1.05 O 3
(LCSM). The Curie temperatures of the La(Fe,Co,Si) 13 materials were 276, 286 and
289 K, respectively. The Curie temperature of the LCSM was 296 K. The magnet-
ocaloric plates were 0.9 mm thick, with the exception of the LCSM plates, which had
a thickness of 0.3 mm. In the experiment, gurations were

tested: three AMRs with a single material (Gd, LCSM or La(Fe,Co,SI) 13 with
T c = 289 K), two AMRs with two-layers of La(Fe,Co,Si) 13 material,

ve different AMR con

rst with
T c = 276 K, T C = 289 K and second with T c = 286 K, T C = 289 K. The highest no-load
temperature span was achieved with the Gd-based AMR (10.2 K). The experiments
on other two AMRs with a single material led to a no-load temperature span of 7.9 K
for (La(Fe,Co,Si) 13 , T c = 289 K), and 5.9 K of temperature span for LCSM. The two-
layered AMR which had magnetocaloric materials with Curie temperatures closer to
each other (286, 289 K) performed 8.5 K of a temperature span, whereas the tem-
perature span in another two-layered AMR was 6.5 K.

7.1.7 Slovenian Prototypes

The University of Ljubljana presented its rst reciprocating AMR testing device

š

(Table 7.8 ) in 2012 in the papers by Tu 32 ].

The device had a static AMR bed and a moving Nd

ek et al. [ 30 -

- Fe - B magnet assembly,

with a magnetic eld of 1.15 T. The maximum operating frequency was 1 Hz. The

heat-transfer fl uid was a 70/30 % mixture of distilled water and anti-freeze