Environmental Engineering Reference
In-Depth Information
Fig. 4.24 a
Schematic presentation of a parallel-plate AMR (up) and packed-bed AMR (down).
b
Table with geometry of the analysed AMRs
Since the Brayton and Ericsson-like AMR cycles and the corresponding time
periods are already shown in Table
4.5
, the Table
4.6
only shows the time periods
for the Hybrid Brayton
Ericsson-like AMR cycle.
-
ned temperature spans
between the heat source and heat sink, i.e. 4, 8,12, 16 and 20 K (with a heat source
temperature of 293 K). In this particular case, two operating frequencies (
The
rst simulations were performed for different prede
) were
applied in the simulations, i.e. 0.5 and 3 Hz, respectively. The utilization factor
(de
ʽ
xed with the value U = 0.3. Note that the selected
operating conditions have been often realized in the best magnetocaloric cooling
devices built to date [
5
].
For the particular cases in Figs.
4.25
and
4.26
, the ratios between the magne-
tization period and the period of constant magnetic
ned by Eq.
4.26
) was
˄
const
= 1:4 for
both frequencies of operation; however, for different absolute time periods (mat-
ched to a particular cycle).
Figure
4.25
shows the dependence of the temperature span and the COP on the
speci
eld were
˄
mag
:
c cooling power for three different types of magnetic refrigeration cycle for a
packed-bed AMR.
Figure
4.26
shows the dependence of the temperature span and the COP on the
speci
c cooling power for three different types of AMR cycles for a parallel-plate
AMR.
From Figs.
4.25
and
4.26
, it is evident that the Brayton-like cycle can achieve
the highest speci
c cooling power, regardless of the temperature span and the AMR
geometry. A slightly lower speci
c cooling power can be obtained with the Hybrid
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