Mathematical model to predict the solid airborne particles concentration in occupational settings

Abstract

In the workplace, the contaminant exposure to airborne hazards should be evaluated due to health and safety issues. It can be done numerically or experimentally, but the numerical approach can be useful when challenging to perform experiments. The well-mixed room (WMR) model is a simple model that can predict the exposure levels to gaseous contaminants, but its use for aerosols is questionable since it omits important phenomena such as particle deposition to solid surfaces. The main objective of this master’s thesis was to determine whether or not the deposition of airborne particles is significant inside a small chamber. To reach this objective, the standard WMR model has been modified to consider the deposition of particles by gravitational settling and Brownian and turbulent deposition. Three deposition models were also implemented in the model. The time-dependent concentrations of airborne particles were compared to experimental results. Experiments were conducted in a 0.512 m3 chamber with polystyrene particles of 1, 2, and 3 μm in diameter and two ventilation air change rates (1.4 and 3.0). The numerical results showed that the average difference between the predicted deposition rate by the three models was less than 2%. The experimental and numerical results were compared for a particle emission period and a period without particle emission (decay period). In the emission period, the numerical results closely follow the experimental data. However, the modified WMR model overestimate significantly the experimental results in the decay period. This finding is due to an underestimation of the deposition rate in the model. According to our experimental parameters, the particle deposition is significant, but the deposition mechanisms that were considered in the model were not sufficient to predict deposition rates. The role of other removal mechanisms should be investigated.

Date	28 Feb 2022
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Stéphane Hallé (Supervisor) & Ludwig Vinches (Co-supervisor)