Numerical study on transient airflows and air exchange induced by door motion in thermally stratified environment

Abstract

Door motion has been identified as a contribution factor for containment transport between indoor and outdoor, but the combined airflow characteristics due to door motion, ventilation airflow and thermal effects have not been clarified. This paper investigated transient airflow characteristics and amount of air exchange induced by hinged door motions in thermally stratified environment with displacement ventilation using dynamic CFD simulation. The results show that about 40% amount of air exchange occurs in the first phase when door angle β < 30° although the consumed time is only 15% of the whole door motion process. Indoor and outdoor air temperature difference and rotation speed of the hinged door are two important influencing factors. When the door motion is slow enough and temperature difference is above 3 °C, the thermal convective flow could significantly affect the airflow pattern through the doorway. When there is no indoor and outdoor temperature difference, the amount of air exchange increases linearly with door motion speed. Under combined effects of buoyancy force and door motion, a moderate door speed results in minimum air exchange. The door motion only affects the air temperatures near the door. The overall thermal stratification in the displacement ventilated room is not significantly destroyed by a single door open and close cycle. The findings could provide suggestions for reducing door motion induced contaminant transport, and enhance understanding of dynamic disturbance effects in thermally stratified environments.