CH-24-C091 - The Effects of Diffuser Location on Ventilated Airflow—A Numerical Simulation Study

The health and comfort of occupants are at the heart of the ubiquitous debate regarding efficient ventilation systems in indoor environments. The air quality, considered from the aspects of thermal comfort and sterility, depends on the distribution of conditioned and clean air. The air distribution, which is governed by the inlet diffusers and the exhaust vents’ locations, has been investigated in many studies. In hot and humid climates, desk fans are often used in combination with mixing ventilation systems to achieve higher thermal set points while still maintaining the thermal comfort. Currently, the studies on desk fans are limited to exploring their impact on personal comfort, without investigating their effects on indoor environment. Therefore, this study aims to study different positioning of the exhaust diffusers and the indoor resultant air distribution patterns when the occupants are using desk fans as it relates to adequate ventilation and contaminant concentration of the occupied zones. In this study, a shared-office space in an educational facility with ceiling-mounted supply and exhaust vent was numerically simulated. Steady-state Computational Fluid Dynamics (CFD) simulations were employed for modeling varied outlet locations, when desk fans were used by the occupants. The simulations were performed using 3D Reynolds-Average Navier-Stokes (RANS) equations and k-e was employed as a turbulence model. The resultant flow patterns were compared to determine the most effective configuration in terms of both thermal comfort and contamination control, estimated by CO2 concentration. The results indicate in mixing ventilation systems, the area situated closer to exhausts exhibit a higher level of indoor environmental quality. Additionally, desk fans alter indoor environment. A significant decrease in temperature and CO2 levels was observed particularly in models where desk fans and wall-mounted (near floor-level) exhausts were used simultaneously. These results are significant, helping strategically positioning of the exhausts for improving indoor environmental quality improvement (thermal comfort and air quality) in places using desk fans.