Environmental Engineering Reference
In-Depth Information
Fig. 6.33 Temperature
distribution of a cascade
magnetocaloric device with
thermal diodes along the
length (y-direction in
Fig.
6.32
) of the device
neighbouring MC materials, as shown in Fig.
6.34
. Figure
6.34
presents all four
phases of the cascade device
s operation in the steady state. It shows the operation
for a given example from Fig.
6.32
. In Fig.
6.34
a the processes of alternating
magnetization and demagnetization can be observed. The MCMs denoted by
numbers 1, 3 and 5 are magnetized, thus their temperature increases due to the MC
effect. Meanwhile, the MCMs denoted by numbers 2 and 4 are demagnetized;
therefore, their temperatures decrease due to the MC effect. All six thermal diodes
are, at this point, non-operational. Figure
6.34
b presents the second phase where the
thermal diodes denoted by numbers 1, 3 and 5 become operational (in this example
all the thermal diodes are considered to be passive thermal diodes).
Thermal diode 5 transports heat from the magnetized MCM 5 to the demag-
netized MCM 4. Thermal diode 3 transports the heat from MCM 3 to MCM 2.
Thermal diode 1, on the other hand, transports heat from MCM 1 to the hot
'
uid.
Thermal diodes 2, 4 and 6 are non-operational during this process, preventing the
heat from being transported from the magnetized MCMs or the cold
fl
uid back to
the neighbouring demagnetized MCMs, which are at a lower temperature.
In the third process presented in Fig.
6.34
c the processes of magnetization and
demagnetization are altered. The MCMs denoted by numbers 2 and 4 are magne-
tized, while the MCMs denoted by numbers 1, 3 and 5 are demagnetized, which
results in a temperature increase or decrease, respectively. All the thermal diodes
are non-operational in this phase. In the last and fourth process (Fig.
6.34
d), the
thermal diodes denoted by numbers 2 and 4 start to transport heat from the mag-
netized MCMs 2 and 4, to the demagnetized MCMs 1 and 3. Thermal diode 6
transports heat from the cold
fl
uid to the demagnetized MCM 6. All four phases of
operation represent one operating thermodynamic cycle of the device.
fl
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