Abstract
An improved theoretical model was presented to predict the filtration efficiency of cigarette filters. Filtration equations of single fibers considering the interference of neighboring fibers were applied in the model. Cellulose acetate fibers in cigarette filters were approximated as cylinders. The fiber size was adjusted by its size projected on the flow field. The solid fraction of fibers in cigarette filters was recalculated using the size of the virtual cylinders. The varying flow velocity during smoking was taken into account when calculating the filtration efficiency. The effective hydrodynamic particle diameter of cigarette smoke was estimated to be 0.44 μm by the difference of filtration efficiencies under ISO and Health Canada Intense (HCI) smoking regimes. Filtration contributions due to diffusion, interception and inertial impaction were 62%, 32% and 6%, respectively, at a flow velocity of 0.38 m/s for particles of 0.44 μm diameter. The effect of inertial impaction was insignificant but not negligible under ISO smoking regime. The measured and predicted efficiencies of two cigarette samples were compared and satisfactory agreement was obtained. [Beitr. Tabakforsch. Int. 26 (2015) 232-240]