Brownian diffusion

The accurate prediction of particle deposition in ventilation ducts is an important step in estimating the exposure risk of building occupants to particulate matter. In this paper a mathematical model for predicting particle deposition in rectangular ventilation duct flow by incorporating existing theoretical and experimental results is presented. The influences of Brownian diffusion, turbulent diffusion and gravity on particle deposition are considered. Model equations are presented for calculating the deposition velocities on vertical surfaces and the floor and ceiling of ducts.