Ventilation System Performance on the Removal of Respiratory Droplets Emitted During Speaking

Abstract

Abstract The SARS-CoV-2 infection pandemic has led to significant loss of lives and worldwide economic disruption. The leading cause of transmission of infectious respiratory diseases is through aerosolized mucous and salivary droplets containing the virus emitted into the environment through respiratory activities. Depending on their initial size, the droplets evaporate or fall to the ground due to gravitational sedimentation. When a droplet evaporates, the droplet nucleus containing all the viruses in the original droplet remains airborne in the environment for a long duration of time. The ventilation system significantly affects the dispersion and removal of particles from the environment. Therefore, poorly ventilated indoor environments increase the risk of disease transmission. The present study modeled a ventilated small office space with two mannequins sitting across a table. It was assumed that one of the mannequins was speaking and emitting small droplets. Then the effect of the ventilation system on the droplets’ transport and dispersion was simulated. In particular, the performance of the displacement and mixing ventilation systems on particle dispersion and deposition in the room were evaluated and compared. These simulations were performed using the computational fluid dynamics (CFD) approach with Ansys-Fluent software. The Eulerian approach was used to simulate the airflow field in the room, and the Lagrangian trajectory analysis approach was used for the droplets. Experimental data of the thermal plume above the mannequin’s head were used to validate the airflow simulation results. The results showed that the displacement ventilation system has better performance (almost three times more) in removing particles from the environment than the mixing ventilation system.