Application of Mixing and Deposition Data of Brownian Particles in a Model Alveolus to Human Alveoli

Abstract

Air-mixing in an expanding and contracting vessel influences the deposition of Brownian particles. In the present work, by using a previously developed technique to measure mixing and deposition of aerosol particles in a balloon (Otani et al., 1990), extensive data were collected to cover a wide range of balloon expansion and contraction conditions. The results were examined in terms of dimensionless parameters derived from the convective diffusion equation to predict the behavior of submicron particles in actual human alveoli. It was found that (1) convective mixing in the balloon is characterized by the Reynolds number at the balloon throat; (2) for Re > 5, the mixing is determined by fluid convection; (3) for Re < 5, Brownian diffusion enhances the mixing; and (4) when dimensionless duration of balloon expansion and contraction is longer than 5 × 10^–4, the mixing does not influence particle deposition and the deposition efficiency can be predicted by diffusional deposition of particles in a spherical vessel with constant volume.