Modeling of ultrafine particle dispersion in indoor environments with an improved drift flux model

Ultrafine particle (sub-100 nm in diameter) can transport toxic chemicals into the human respiratory system, causing more damage to macrophage phagocytosis than micron particles do. Therefore, various computational fluid dynamics (CFD) models have been developed to help understand the transport and dispersion of these particles in indoor environments. This study is focused on an improved drift flux model that incorporates not only the effect of gravitational settling but also other mechanisms. After an experimental validation of the improved model, it was used to analyze the dispersion of different sizes of ultrafine particles in two typical types of indoor environments (mixing and displacement ventilation). It was found that mixing ventilation had higher concentrations of ultrafine particles than displacement ventilation in the zone below 1 meter, and this finding is different from micron range particles. In addition, both ventilation modes were insensitive to the particles in the range of 0.01–0.1 μm in diameter.