Abstract
Indoor air quality (IAQ) plays a critical role in occupant health and productivity, with carbon dioxide (CO2) concentration serving as a key indicator of ventilation performance. This study applies computational fluid dynamics (CFD) to analyze CO2 transport and airflow behavior in office environments with varying configurations. The CFD model builds on previously validated work: airflow matched to anemometer data, mesh independence confirmed, and CO2 field validated against sensor measurements. It is adapted for office conditions. Two office spaces are modeled, both featuring distinct air conditioning (AC) systems: window-type unit (Site I) and ceiling-mounted 4-way cassette unit (Site II). Airflow validation produced root mean square errors (RMSE) of 0.185 m/s and 0.27 m/s for Site I and Site II, respectively. At t = 2 h and maximum occupancy, Site I recorded 2,121 to 2,137 ppm at breathing height with a homogeneous distribution. In contrast, Site II recorded 1,930 to 2,620 ppm, demonstrating strong spatial localization and less effective mixing. Although the ceiling-mounted 4-way AC regulated temperature effectively, it concentrated CO2 in specific quadrants, reducing ventilation efficiency. Occupant distribution, particularly in meeting room settings, further influenced pollutant buildup, demonstrating the role of occupancy patterns in indoor pollutant distribution. These findings underscore the importance of HVAC design: careful planning of AC placement, airflow paths, and room layout is essential to ensure uniform air distribution and prevent stagnant CO2 zones.
