A SIMPLIFIED APPROACH FOR MODELLING AIRBORNE NANOPARTICULES TRANSPORT AND DIFFUSION

A simplifi ed approach is proposed and used to study the TiO2 nanoparticle transport and diffusion in an exposure chamber. This exposure chamber is used to assess lung toxicity in rats resulting from the inhalation of airborne nanoparticles. The simplifi ed approach uses computational fl uid dynamics (CFD) commercial software. The mathematical model for airfl ow is based on the three-dimensional Reynolds-averaged Navier–Stokes equations with turbulence modeling. The mathematical model for airborne nanoparticles transport is based on assumptions such that their motions are similar to those of a single-sized diameter distribution of a passive contaminant. This model is valid as long as the nanoparticle concentration is low and the particle diameter is small enough that settling is negligible, which is the case for the exposure chamber studied. With this model, the diffusion coeffi cient is a property that plays a signifi cant role in the transport of airborne nanoparticles. The particle diffusion coeffi cient can be expressed in terms of a friction coeffi cient, and three possible relationships to model particle diffusion are presented. Their infl uences on the friction and diffusion coeffi cients are considered for the particu-lar case of TiO2 nanoparticles. Although all the models studied here predict a decrease in the value of the diffusion coeffi cient with increasing particle diameter, some signifi cant variations can be observe