A study on the characteristics of airflow in a full scale room with a slot wall inlet beneath the ceiling.

Symmetry is not a sufficient condition for the design of a ventilated room to generate two-dimensional airflow. Three-dimensional effects were observed in a symmetrically designed 3m x 5m x 8.5m test mom having a 0.019m slot inlet opening height under the ceiling in the one end wall. The ceiling jet velocity profile measured in the symmetric plane agreed well with the jet models for two-dimensional !low, but large differences were found out of the symmetric plane. The velocities in the jet 4.5m downstream from the inlet wall were up to a factor of two higher on the one side than the other side. During the measurement period the side with high velocities occasionally changed without any obvious disturbance in the room. Two semi-stable statuses were observed. The measured velocities in the symmetric centre plane were only slightly effected by the switch-over and remained at the same level throughout the experiment In both statuses the return air direction diverged 30° from the symmetric plane. Systematic validation of flow behaviour is thus necessary before the assumption of two-dimensional flow should be accepted and a study is carried out in the symmetric plane only.