Assessment age of air and thermal comfort in a classroom by adopting displacement ventilation with chilled ceiling system

This study aims to investigate the effect of the cooling load ratio covered by the chilled ceiling on the age of air and comfort level in a classroom in a hot and dry climate in Iraq-Hilla city. Air age, air exchange efficiency, and concentrations of pollutants in a classroom are investigated numerically by used AIRPAK software under displacement ventilation combined with a chilled ceiling system. Four cases are studied at different values of the cooling load covered by the chilled ceiling (0%, 25%, 50%, 80%) with respect to total classroom cooling load. Cooling load removes by chilled ceiling varied from (0 to 84.5 W/m(2)) based on the classroom area, and its temperature varied between (17.5-22.5 degrees C). The displacement ventilation airflow rate was kept at 0.3m(3)/s, and the air temperature supply varied between (19.5-24.5 degrees C) depend on the amount of cooling load covered by displacement ventilation. The results showed that the mean local air age increasing with height. The room mean air age increase and air exchange efficiency reduce with increasing load portion, which treated by the chilled ceiling. Increasing the portion of the load treated by chilled ceiling tends to improve comfort levels.