Diffusion characteristics of the industrial submicron particle under Brownian motion and turbulent diffusion

Abstract

The industrial release of submicron aerosol particles at workplace could cause undue health effect on workers. To effectively capture and remove airborne particles, we need to study the characteristics of various interactive particle motion forces (drag force, Brownian force, Saffman lift force, etc.) and the dispersion of these aerosol particles in indoor air. In this study, the dominant force of submicron particles was determined by calculating the acting forces with different particle sizes. Then, a Discrete Particle Model (DPM) was used to calculate the trajectory of particle movement in turbulent thermal plume flow. Horizontal dispersity ( DH) was defined to evaluate the horizontal diffusion of the particulate matter. The impact of different particle diameters, heat source temperatures and initial relative velocities on DH was investigated. This study showed that the main acting forces for submicron aerosol particles were drag force, Brownian force, Saffman lift force and thermophoresis force. Brownian force cannot be ignored when the particle diameter was below 0.3 µm, which would promote the irregular movement of particles in space and enhance their diffusion ability. The smaller the particle size, the higher the heat source temperature and the lower the particles' initial velocity would lead to the increase of DH.