Mechanisms responsible for sub-micron particle deposition in a laminar wall-jet

Abstract

An experimental study was performed to investigate the dependency of particle size on the deposition rate. Polystyrene latex particles of two radii (0.23 and 0.38 μm) were deposited onto a glass surface covered with indium-tin oxide. Reduced deposition efficiency was observed for the larger particles, although an increase in the deposition efficiency was seen as that the diffusion boundary layer became thicker. A critical degree of surface coverage, θ crit , was defined as the fraction of surface coverage at which the linear variation of flux with time ended. When the two particle sizes were compared, it was found that the value of θ crit depended only on the wall shear stress. This result indicates that surface shielding is an important factor in the decline in particle flux. The deposition process was divided into two separate processes, described by a mass-transfer coefficient and an adhesion rate coefficient. It was found that the process was governed by mass-transfer during the initial period, but for higher degrees of surface coverage adhesion became the rate-determining factor.