Environmental Engineering Reference
In-Depth Information
cooling power and temperature span. There it was assumed that the cooling power
is directly proportional to the mass of the magnetocaloric material. The authors used
Eq. (
9.13
) and for each temperature span and magnetic
eld calculated the com-
bined cost of the magnet and the magnetocaloric material. This was repeated for all
the parameters. Then the lowest cost was chosen for the presentation.
Figure
9.17
shows the minimum costs for a Gd-based AMR consisting of a
packed bed of spheres and parallel plates, respectively. The
gure was produced
based on data from Bj
rk et al. [
38
]. The costs are presented as a function of the
cooling power. Additionally, the costs for an ideally layered AMR with the prop-
erties of gadolinium are shown. All the cases correspond to a temperature span of
30 K.
The authors also presented the masses that corresponded to a particular cooling
power and temperature span. However, they did not consider the coef
ø
cient of
performance at which the temperature span and the particular cooling power can be
obtained.
In 2011, Rowe also presented his work on the con
guration and performance
analysis of magnetic refrigerators [
39
]. He based his economic evaluation on an
exergy analysis and proposed a model for such an evaluation. In the model he
presented the speci
c costs per watt of cooling as a function of the speci
c exer-
getic cooling power, which he de
ned as
f
R
B
0
E
V
mc
l
¼
ð
9
14
Þ
:
which has units of watt of exergy of cooling per litre of magnetocaloric material
and per magnetic
fl
ux density in Tesla and where E represents the exergy of the
cooling energy:
Fig. 9.17 The minimum combined cost of permanent-magnet material and magnetocaloric
material for a parallel-plate and packed-bed magnetic refrigeration system with a magnetocaloric
material of gadolinium for a temperature span of 30 K (data taken from Bj
ø
rk et al. [
38
]). Ideal
represents an ideally layered AMR with the properties of Gd
Search WWH ::
Custom Search