Diffusion of aerosols in laminar flow in a cylindrical tube

Abstract

Presented herein is the problem of mass transfer of aerosols with axial diffusion in laminar flow through a cylindrical tube. Two cases are studied. In the first case all particles enter the channel inlet and none form within the channel; and in the second case, no particles enter the channel, and “formation in flight” occurs within the channel. For each case, analyses are made for both slug and Poiseuille flows. The effects of axial diffusion on the particle concentration and the fraction of aerosols arriving at any cross-section downstream from the tube inlet are studied for various diffusion Peclet numbers, Pe. It was found that, for Pe ≤ 100, the effect of axial diffusion is still significant at μ < 0·04. Moreover, the effect may be neglected at an axial distance from the tube inlet greater than two and a half times that of the tube diameter for 1 < Pe < 100.