Computational modeling of aerosol transport and deposition: Electrophoretic and thermophoretic effects

A computational scheme for studying aerosol particle transport and deposition in turbulent and laminar flows is developed. Particle equation of motion including nonlinear drag, lift, gravity, Brownian, electrical and thermal forces are used in the Lagrangian trajectory analysis. The Brownian force is modeled as a Gaussian white noise random process. The effects of presence of an imposed electric field, as well as a temperature gradient field on particle dispersion and deposition are studied. The mean turbulent flow and temperature fields are evaluated with the aid of the FLUENT code. The Reynolds stress transport turbulence model is used in the analysis. The instantaneous fluctuation velocity field is generated by the continuous filtered white noise model.; Deposition of neutral and charged particles in nearly developed turbulent duct flows is studied. The cases that the duct is vertical or horizontal and when the particles have Boltzmann, static electrification, as well as saturation charge distributions are analyzed. For heat conducting duct flows, dispersion and deposition of aerosol particles including the effect of thermophoresis under laminar and turbulent flow conditions are studied. An improved model for thermophoretic force acting on small particles is presented. The simulation results are compared with the available experimental data, the earlier numerical results and those obtained from empirical equations for fully developed duct flows.; The computational model is applied to study dispersion and deposition of particles with eletrophoresis in an axisymmetric turbulent pipe flow with sudden expansion. The simulated fluid and particle mean velocities are compared with the available experimental data. Ensembles of particle trajectories are evaluated and statistically analyzed. For a point source and a uniform inlet concentration, wall capture efficiencies for neutral and charged particles of different sizes are evaluated. Influences of particle size and source location on dispersion and deposition processes are studied. The results show that the presence of a strong electric field significantly affects the charged particle deposition rate.; A series of simulations for particle transport in a triboelectric coal/ash cleaning system are also performed. The particle trajectories are evaluated and their distribution at various sections is analyzed. The effect of electric field on the performance of the separator is studied. The performance of a separator with manufacturing imperfections is also studied.; Dispersion and deposition of particles in a combustor with swirling flow and chemical reaction are analyzed using the Lagrangian numerical simulation procedure. The simulation results for axial, radial and tangential mean gas velocities, as well as temperature distributions are compared with the corresponding experimental data. Ensembles of several thousand particle trajectories are evaluated and statistically analyzed. Particle concentration at different sections and deposition distribution are also evaluated.; A computer simulation study of gas flow and particle transport and deposition in the CONSOL Pilot Scale Boiler with the cooling system is also performed. The Gambit code is used to generate the geometry and an unstructured computational grid. The gas mean velocity, the turbulence fluctuation energy, mean pressure, temperature fields and chemical species concentrations, as well as, particle trajectories and deposition rates on different surfaces in the boiler are evaluated.