Numerical Study of Particle Deposition in Two Differently Ventilated Rooms

Abstract

A three-dimensional drift-flux model combined with deposition boundary conditions for the wall surfaces is presented to study particle deposition in a room ventilated either by displacement or mixing. The deposition boundary conditions were developed based on the work by Lai and Nazaroff. The turbulence effects of the indoor airflow were modelled with a zero-equation turbulence model by Chen and Xu. Several particle sizes, 1, 2.5, 5, 7.5, 10 micron, were investigated. The results showed that the deposited particle mass flux at vertical walls and floor were very different in the two differently ventilated rooms, even though the mean particle deposition velocities and mean deposition rate were almost the same for a certain size of particles. The deposited particle mass in rooms ventilated by mixing was larger than that in the room with displacement ventilation. The calculated mean deposition velocities and mean deposition rate of some sizes of particles agree with the measured data reported in the literature, while the results of small size (1µm) and large size (10µm) particles have obvious discrepancies.