Multiple regimes of stack ventilation driven by a thermal source in a room with a high-level opening and a doorway

Laboratory experiments were conducted to examine flow regimes in a room with a high-level opening and a doorway connected to the environment. Based on the neutral level concept, theoretical formulations for three distinct flow regimes (displacement, arrested outflow, and unbalanced exchange) are re-derived and validated against laboratory experiments. These models successfully predict both the stratified interface height and the neutral level position. This agreement demonstrates that the two-fluid model serves as an extension and complement to the classical hydraulic approach employed in previous studies. In the regimes of the displacement and arrested flows, the neutral level position is determined solely by the area ratio of the upper to lower openings for a fixed effective area. In the unbalanced exchange flow regime, increasing the doorway height or width is more effective in raising the interface height than increasing the upper opening area under a given effective area. This study is particularly significant for understanding and predicting the flow in a room with a high-level opening and a doorway, as well as for determining the geometry of the doorway at the preliminary architectural design stage.