MEASUREMENT OF AEROSOL EFFECTIVE TRANSPORT COEFFICIENTS IN CYLINDRICAL TUBES

Transport of submicrometer aerosols in flows in tubes can be described by an effective one-dimensional axial convection–diffusion equation with apparent aerosol transport properties: mean aerosol velocity, mean aerosol diffusion coefficient (dispersivity) and mean aerosol deposition coefficient. These quantities are investigated experimentally by shape analyses of boluses of submicrometer Latex aerosol particles injected in the clean air flow through long tubes and a diffusion battery of capillary tubes. It is shown that the aerosol effective dispersivity and volumetric deposition coefficient significantly depend on the particle transit (residence) time within the tubes. For sufficiently long residence times these quantities are found to approach their asymptotic limiting values, predicted by the existing theories of the hydrodynamic dispersion. On the other hand, the mean aerosol velocity only weakly differs from the mean air velocity, and is almost independent of the aerosol residence time. The results obtained are important in several applications, including particle sampling using long tubes or lines.