Abstract
The dispersion and deposition of nano-particles in laminar flows in the presence of an electric field were studied. The Eulerian-Lagrangian particle tracking method was used to simulate nano-particle motions under the one-way coupling assumption. For nano-particles in the size range of 5–200 nm, in addition to the Brownian excitation, the electrostatic and gravitational forces were included in the analysis. Different charging mechanisms including field and diffusion charging as well as the Boltzmann charge distributions were investigated. The simulation methodology was first validated for Brownian and electrostatic forces. For the combined field and diffusion charging, the simulation results showed that in the presence of an electric field of 10 kV/m, the electrostatic force dominates the Brownian effects. However, when the electric field was 1 kV/m, the Brownian motion strongly affected the particle dispersion and deposition processes. For the electric field intensity of 1 kV/m, for 10 nm and 100 nm particles, the deposition efficiencies for the combined effects of electrostatic and Brownian motion were, respectively, about 27% and 161.2% higher than the case in the absence of electric field. Furthermore, particles with the Boltzmann charge distribution had the maximum deposition for 20 nm particles.
Highlights
It is well-known that air pollutants have serious adverse health effects (Shy et al, 1978)
For nano-particles, which are of concern in this study, the contributions of diffusion charging are higher than those by field charging for all the studied electric field intensities
In this paper, the effects of Brownian diffusion on nano-particle deposition in a fully developed duct flow were compared with electrophoresis in the presence of various electric field intensities
Summary
It is well-known that air pollutants have serious adverse health effects (Shy et al, 1978). Dixkens and Fissan (1999) studied particle deposition in electrostatic precipitators numerically and experimentally They considered the effects of diffusion, electrostatic force, thermophoresis and sedimentation, and included the effects of field charging. Dong et al (Dong et al, 2018) studied the charging and transport of fine particles in a wire-plate electrostatic precipitator using multiple wire electrodes They employed the Lagrangian particle tracking method and considered the effects of Brownian diffusion and electrophoresis and analysed the influence of applied voltage. The Lagrangian particle tracking method is used for evaluating the transport and deposition of nano-particles in fully developed laminar duct flow, considering the effects of Brownian, electrostatic and gravity forces. A comparative study of the effects of electrophoresis and Brownian diffusion on charged nano-particle deposition in the presence of different electric fields is performed
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