Biomedical Engineering Reference
In-Depth Information
Field lines
U
mf
<
U
<
U
t
U
<
U
mf
U
mf
<
U
<
U
t
H
<
H
c
H
>
H
c
H
(I)
(II)
(III)
U
>
U
t
U
>
U
t
H
<
H
c
H
>
H
c
(IV)
(V)
FIGURE 12.3
Different behaviors of a magnetic stabilized and fluidized bed: (I) fixed bed;
(II) fluidized stabilized bed; (III) fluidized expanded bed; (IV) bubbling bed;
(V) heterogeneous bed.
velocities above the velocity of transition,
U
t
; (5)
Heterogeneous Bed
—in this
region it is observed that the system starts creating preference paths for the
fluid to flow, as the particles tend to align with the field. This phenomenon
appears when the magnetic field is maintained above a certain magnitude and
for velocities above the velocity of transition,
U
t
.
In Figure 12.3 we present a graphical depiction of the bed behavior in each
of these regions. Increasing the velocity too much will lead to the collapse of the
bed and the particles will be dragged by the flow—this is called
elutriation
and
the corresponding velocity is known as elutriation velocity. On the other hand,
if the magnetic field is increased too much, regardless of the velocity value,
the magnetic particles in the bed will start to align with the field creating the
above cited preference paths, which allow a tunneling effect of the flow, and
the pressure drops abruptly.
There are several important characteristics of the MSFB that make them
the best option for several biotechnological and biomedical applications, and
many of them are referred in several sections of this chapter. Nonetheless,
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