Impact of Airflow Rate and Supply-Exhaust Configuration on Displacement Ventilation in Airborne Pathogen Removal

Displacement ventilation systems can offer healthy indoor air quality (IAQ) by maintaining stratified flows that transport and expel airborne contaminants through the upper region of indoor spaces. Using large eddy simulation (LES), we investigate displacement ventilation in a generic indoor space under varying ventilation flow rates and supply–exhaust configurations. Assessing the ventilation system requires quantitative evaluation of airborne contaminants, for which CO 2 concentration is typically used as a proxy. However, in this study, we show that there is both a qualitative and quantitative correlation between CO 2 and airborne respiratory particles using computational particle fluid dynamics simulations. The role of the ventilation flow rate in ventilation efficacy is investigated for low values ranging from 0.01 to 0.06 m 3 /s, and the role of supply–exhaust configuration is assessed by considering in-line and staggered layouts. At low flow rates (0.01 to 0.04 m 3 /s), the ventilation system maintains a stable stratified layer within the room. Within this regime, the CO 2 level in the occupied zone is inversely proportional to the ventilation rate. At higher flow rates, the ventilation transitions to a mixing regime, effectively nullifying the intended design of the system. Interestingly, the two opening configurations produce nearly identical trends, suggesting that jet strength and room geometry dominate over modest opening shifts in this setup.