Effect of ventilation duct as a particle filter

Abstract

This paper discusses the effect of ventilation duct as a particle filter by modeling particle deposition in ventilation ducts, which is the reason that ventilation ducts could “filter” particles. An Eulerian model is employed to predict the particle deposition velocity onto the wall and floor from fully developed turbulent flow in ventilation ducts [Zhao B, Wu J. Modeling particle deposition from fully developed turbulent flow in ventilation duct. Atmospheric Environment 2006;40:457–66], while an empirical equation is proposed to predict the particle deposition velocity onto the ceiling combined with experimental data and, another empirical equation by McFarland et al. [Aerosol deposition in bends with turbulent flow. Environmental Science and Technology 1997;31:3371–7] is used for predicting the particle penetration through the bends, which are hard to analyze by theoretical method.Losses through ventilation duct are thus evaluated for the particle size range 0.01–100μm. Both straight duct (implies fully developed turbulent flow) and duct bend (implies developing turbulent flow) cases are analyzed. Then particle penetration through the supply duct of a swimming pool, including some straight ducts and bends, is analyzed as an application case. The results show that when particle diameter is larger than 5μm, the filtration of the duct might not be ignored as the obvious loss by deposition.