Environmental Engineering Reference
In-Depth Information
Fig. 9.2 Permanent-magnet
assembly that provides 1 T of
magnetic flux density in a
volume of 120 cm
3
(see also
[
8
])
Table 9.2 The magnetocaloric properties of the analysed materials (see Chap.
4
for the denition
of the maximum specic refrigeration capacity)
Material
Δ
s
is
(Jkg
−
1
K
−
1
)[
9
]
q
Rmax
(Jkg
−
1
)
Δ
T
ad
(K) [
9
]
Gd
3.3
3.1
910
LaFeCoSi
2.2
5.3
1,553
Table 9.3 The theoretical maximum cooling power (W) for the selected case at T
R
= 292 K
Frequency (Hz)
Material
1
2
5
10
Gd (W)
604
1,208
3,019
6,039
LaFeCoSi (W)
1,031
2,061
5,153
10,306
gadolinium manufactured as the AMR. In this analysis we assume that the mass
production manufacturing costs of magnet assembly (labour, energy and manu-
facturing devices) represent 25 % of the basic capital cost.
Now, for the chosen magnet assembly (Fig.
9.3
) we can assume the mass pro-
duction and the following costs for materials and manufacturing (Table
9.4
).
The maximum relative costs for a refrigerator
s compressor relates to very small
units (large compressor unit represent substantially smaller relative costs than
smaller units). Despite this a 50-W compressor
'
s production costs are approximately
12 euros or 0.24 euros/Wcooling power. So, what level of theoretical costs for the
magnet assembly is acceptable? We assume again the most ideal case, which con-
siders that the costs of the compressor are equivalent only to the magnet assembly
with the magnetocaloric material, by neglecting all the other components of the
magnetic refrigerator. By combining the results in Tables
9.3
and
9.4
we can now
express the speci
'
c costs in euro per watt of cooling power, as shown in Fig.
9.3
.
Despite the fact that Fig.
9.3
shows that a frequency of operation higher than
2 Hz is required to obtain the same speci
c costs as for the compressor, note that the
magnet assembly with the magnetocaloric material will account for up to 60
80 %
of the total costs of the magnetic refrigerator [
10
]. Therefore, in order to have a
-
Search WWH ::
Custom Search