Environmental Engineering Reference
In-Depth Information
1
T
H
T
C
E
¼
Q
c
ð
9
:
15
Þ
and B
0
represents the applied magnetic
ux density in units of Tesla, V
mc
is the
volume of magnetocaloric material and f
R
is the frequency at which the magnet-
ocaloric material is cycled.
The device frequency f
D
was de
fl
ned as the rate at which the alignment of
magnets and regenerator is repeated. The relation between the magnetocaloric
material
'
s frequency and the device frequency was given with the following
relation:
f
R
¼
ab
f
D
ð
9
:
16
Þ
where a represents the fraction of refrigerant seen by a single high-
eld region and
b represents the number of high-
eld regions.
As an example, in the article he was investigating the economics of a small
magnetic refrigerator with a cooling power of 70 W, operating with a heat source
temperature of 7.4
C (temperature span of
47 K). The cost of the magnetic refrigerator was based on the costs of the per-
manent-magnet material (40 US$kg
−
1
) and the costs of the magnetocaloric material
(20 US$kg
−
1
). No other costs were taken into account, since the magnets and the
magnetocaloric material were assumed to represent the major cost contribution. In
order to compare with the conventional refrigeration technology, Rowe [
39
] con-
sidered the cost of the compressor unit as 0.5 US$/Wcooling (for COP = 1.6) and
1.9 US$/Wcooling (for COP = 2.6).
The results of the study reveal that for the considered application, in order to be
applied on the market, the speci
°
C and a heat sink temperature of 54.4
°
c exergetic power must be between 400 and
1,000 W(lT)
−
1
if the COP is in the range 1.6
2.6, with the cost of the cooling being
less than 2 US$(Wcooling)
−
1
. However, Rowe [
39
] emphasized that if the COP of
the magnetic refrigerator can be higher, then a higher device cost and a lower
speci
-
c exergetic power will be acceptable.
A year earlier, in 2010, Roudaut et al. [
40
] carried out a cost analysis and related
comparison of existing prototype devices. For the purpose of the study the costs of
the Nd
-
Fe
-
B magnets, gadolinium (as the magnetocaloric material), Fe and FeCoV
were considered to be 100, 130, 1 and 80 eurokg
−
1
, respectively. The study
revealed the following speci
c costs (Table
9.8
) of a device per cooling power (see
Table 9.8 Devices for which
the cost estimation was
performed by Roudaut et al.
[
40
]
Speci
c cost (euroWcooling
−
1
)
Authors
Bj
ø
rk et al. [
41
]
3.16
Tura and Rowe [
42
]
16.4
Lee et al. [
43
]
5.35
Zheng et al. [
44
]
2.46
Okamura et al. [
45
,
46
]
1.69
Zimm et al. [
47
]
4.56
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