Environmental Engineering Reference
In-Depth Information
Fig. 8.13 Different magnetic flux directions will require different arrangements of AMR plates as
shown in cases (a) and (b), classi
cation no: R20(3)0(5)(6)0(8)111(12)
150 mm, depending on the type of the working
uid, the AMR structure, the
magnetocaloric material, the frequency of the operation and of course the desired
temperature span). This, however, in some cases will not be suf
fl
cient to provide the
desired temperature span. However, there are solutions in which for instance the
fl
ows forwards and backwards in the radial direction through the U-shaped
AMR. Another solution is when the fluid passes the AMR in the radial direction;
however, it also moves in a kind of zig-zag arrangement in the azimuth direction.
Also in radial devices, the number of poles (high magnetic
uid
fl
eld regions) can
vary. Therefore, a similar example as shown in Figs.
8.10
and
8.11
can be applied
for radial devices as well.
8.2.1.3 Azimuth Rotary Magnetocaloric Devices with Rotating AMRs
The magnetocaloric material in this case is attached to a rotating ring. It is important
to separate the AMRs in order to provide pipe connections and therefore enable the
azimuth
uid (Fig.
8.14
). What kind of central diameter of such
an AMR structure (ring) has to be provided? For the two-pole magnet, four AMRs
can be applied. Since the space that allows the entering and exiting of the working
fl
fl
ow of the working
fl
uid has to be comprised, the length of a single AMR will be, in this case, about 0.5
of the value of the central diameter (where the maximum possible length of each of
four AMRs corresponds to
d/4, where d represents the central diameter of the
AMR ring) of the ring with AMRs. In the four-pole magnet (eight AMRs), half of
this value (0.25) will be approximately available. Let us consider the four-pole
magnet with the length of each AMR being in the range from 50 to 150 mm. Then
this would require that the outer diameter of the ring with eight AMRs (four
magnetized and four demagnetized) is in the range from about 200 to 600 mm (for
the length of a single AMR being L = 0.25 d). This simple example shows the
design restrictions of devices based on the azimuth
π
fl
ow of the working
fl
uid.
Furthermore, one should also take care about
nding the proper
fl
uid
fl
ow solution
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