Modelling of Particle Deposition and Rebound Behaviour on Ventilation Ducting Wall Using an Improved Wall Model

Abstract

This paper reports a study of particle deposition and rebound behaviour in a vertical two-dimensional ventilation duct, employing a Lagrangian particle model incorporating an algebraic rigid particle—wall impact model. A RNG κ - ε turbulence model was applied to solve the turbulent duct flow. Fifteen particle size groups ranging from 5 to 200 μm are investigated with one-way coupling approach. The turbulent airflow and particle movement were validated by experimental data. Adopting the particle—wall impact model, the dimensionless deposition velocities have been predicted smaller than those using conventional ‘‘trap’’ model, especially for particles of large relaxation time. The dimensionless deposition velocity and deposition fraction would first increase, and then decrease with increasing particle diameter. The deposition and capture fraction would roughly decrease with increasing frictional velocity. Additionally, Saffman force has played an important role in this improved wall model. This paper has demonstrated that particle rebound could have a considerable effect on the deposition and concentration of large particles in rooms and ventilation ducts. These findings would benefit the design of filters in ventilation systems and the control of particle contaminants that could affect the indoor air quality of the living spaces.