Small particle diffusion penetration of an annular duct compared to other geometries

The problem of steady-state diffusion of aerosols without axial diffusion inside a long annular channel and for a small diffusion parameter, μ, is treated in an analytic form. A solution for laminar flow without a velocity boundary layer is given and the results are compared with existing numerical approaches. Comparisons of the collection behaviour between a flat rectangular channel, a circular tube and an annular channel are made through dimensionless efficiency curves for different ratios R1/R2.