Non-passive particle dispersion in a displacement ventilated room - a numerical study.

Health effects caused by aerosol air pollutants in the breathing air is a main target for occupational health investigations. The effects of aerosol particles on health usually depend on the dose of particulate matter (PM:) retained at various locations of the respiratory tract. Displacement ventilation has been proved to be an effective ventilation system for the removal of passive pollutants in many buildings. The question is often asked about the performance of non-passive particle removal in a room ventilated by displacement ventilation. In the present paper, non-passive particle dispersion behaviour in a room ventilated by displacement ventilation is investigated numerically. The dispersion of particles is predicted by a drift-flux model where a settling term is added to the concentration equation, and the body force term in the momentum equation is treated using the principle of a Boussinesq approximation, similar to that in a thermal-buoyancy-driven flow. Turbulence effects in the air stream are modelled with a standard k-e turbulence model. Some preliminary model validation work has been done by comparing numerically calculated result; with those measured in an aerosol chamber. The main purpose of this study is to find out how particles of different sizes behave in a displacement ventilated room, and how different ventilation conditions change the exposure levels in the breathing zone.