Environmental Engineering Reference
In-Depth Information
Fig. 14.12 The frequency
dependence of the real
component of the Clausius-
Mossotti factor, for the
probes A, B, and C
14.3.2 Numerical Simulations
14.3.2.1 Mathematical Model
The experimental results obtained by dimensional analysis and dielectric measure-
ments are used as input data for the simulation of the transport phenomena inside a
realistic DEP device for nanoparticle trapping from flue gas. First, we compute the
pDEP force distribution inside a typical DEP device and then we move to the
problem of determining the distribution profile of nanoparticles under the influence
of dielectrophoresis. Finally, we analyze and discuss the obtained numerical results
in terms of
Filtration rate
, a global quantity correlated with the concentration field,
which offers a more suggestive characterization of the capabilities of the device
regarding the separation process of nanoparticles from flue gas. All the numerical
simulations were performed using the COMSOL Multiphysics program.
A typical DEP-based separation device with parallel interdigitated bar electrodes
placed on the bottom surface is illustrated in Fig.
14.2
. In most of the proposed
models, due to the symmetry of the geometry and considering the electrodes much
longer than their width, the problem is treated in two dimensions and the electrodes
'
height is neglected. In our study, in order to have a more realistic description of the
experimental device, a 3D geometry and a detailed description of the electrodes
shape are used. Anyway, taking into account the periodic distribution of the
electrodes, the numerical calculations of the DEP force and the concentration
field can be performed considering as computational domain only a so-called
basic unit cell, which fully describes the entire system, except the vicinity of the
walls. The geometry of the computational domain, together with the associated
boundary conditions necessary to solve the Laplace equation for electric potentials,
V
R
and
V
I
, is presented in Fig.
14.13
.
