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magnetocaloric materials used were 1-mm-thick Gd plates. The plates were
immersed in the heat-transfer
uid, which was a mixture of 80 % water and 20 %
ethyl alcohol. The magnetic regenerative material was moved reciprocally from the
hot end to the cold end of the heat-transfer
fl
eld of
7 T was applied using a superconducting magnet. The highest no-load temperature
span achieved was 47 K. Brown proposed a cascade system to further increase the
temperature span of his magnetocaloric device.
The second reciprocating magnetocaloric device was designed at David Taylor
Research Center by Green et al. in 1990 [
3
]. The two magnetocaloric materials used in
the AMRwere Gd (T
c
= 293K) and Tb (T
c
= 235K). Rolled ribbons of 1/3 of Tb, 1/3 of
Gd
fl
uid and vice versa. A magnetic
Tb alloy and 1/3 of Gd were layered along the length of the AMR (the direction in
which the temperature gradient occurs due to the
-
ow). The AMR was 140 mm
long, 40 mm in diameter and contained 500 g of magnetocaloric material. A super-
conducting magnet was used to induce 7 T of magnetic
fl
uid
fl
uid
was nitrogen gas. The device could operate at a frequency of 0.0143 Hz and achieved a
maximum no-load temperature span of 24 K. At 5 K of temperature span, the device
produced 10 W kg
−
1
of speci
eld. The heat-transfer
fl
c cooling power (cooling power per mass of magnet-
ocaloric material), whereas at 20.5 K the speci
c cooling power was 4 W kg
−
1
.
The third reciprocating prototype was built by Astronautics Technology Center
and Ames Laboratory from Iowa State University (Table
7.1
) and presented by
Zimm et al. in 1998 [
4
]. The prototype consisted of two AMRs moving reciprocally
in and out from the Nb
eld
was 5 T. Each AMR contained 1.5 kg of Gd spherical particles with a diameter
varying between 0.15 and 0.3 mm. The heat-transfer
Ti superconducting magnet. The induced magnetic
−
fl
uid was water. Such a device
c cooling power of 200 W kg
−
1
could produce a speci
for a temperature span of
9 K and at a magnetic
eld change of 5 T. At 1.5 T and 7 K, the speci
c cooling
power was 70 W kg
−
1
.
In 2002 researchers from Los Alamos National Laboratory presented a recipro-
cating prototype in an article by Blumenfeld et al. [
5
]. The prototype consisted of a
high-temperature superconducting magnet and a spherical Gd packed-bed AMR. In
this way the magnet and the AMR were static, while the heat-transfer
fl
uid was
oscillatory,
fl
owing through the AMR bed with the help of a piston. The heat-transfer
fl
eld strength was 1.7 T. The cylindrical
AMR was 160 mm long, with a diameter of 25 mm and the packed-bed spheres had a
diameter of 0.2 mm. The total mass of the AMR was 64.6 g. The operating charac-
teristics were measured at two operating frequencies, i.e., 0.017 and 0.034 Hz. At
0.017 Hz the no-load temperature span achieved was 23 K. When a speci
uid used was water. The magnet
'
s magnetic
c cooling
load of 12.4Wkg
−
1
was applied, the temperature span in the steady state was 18 K. At
0.034 Hz, a no-load temperature span was not reported. However, when applying
46.4 W kg
−
1
of speci
c cooling load, a temperature span of 13.5 K was achieved.
In 2012 researchers from Oak Ridge National Laboratory also presented their
rst reciprocating magnetic prototype in Shassere et al. [
6
]. The testing device
consisted of electromagnet assembly that could induce magnetic
eld of 0.75 T.
Two AMRs were constructed from 1-mm-thick Gd sheets with spacings of 0.25 and
0.5 mm. This accounted for total AMR masses of 575 and 475 g, respectively.
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