The performance of an exterior hood is known to be affected by the cross draft (1, 2). Based on the knowledge from a classical "Rankin's nose" or "semi-infinite body" problem, in which the opening shrinks to a sink instead of a finite opening, the exhausted airflow combining the cross draft forms a capture envelope in front of the hood(3). All streamlines within the envelope lead to the hood opening, those outside of the envelope lead to infinity. Therefore, contaminant released inside the envelope tends to be captured by the hood; otherwise, it tends to escape beyond capture.
When designing push-pull ventilation system as usual, it has been considered that supply airflow should be thoroughly exhausted by suction inlet. However, an escape of some of the supply airflow from an exhaust inlet could be permitted in the push-pull ventilation system, if all of the contaminants transported to the exhaust inlet do not escape and can be exhausted. In this study, we investigate appropriate flow rate for push-pull ventilation system by using CFD techniques.
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