Abstract

Air curtains are used to reduce the heat and the mass exchange between an indoor environment and the ambient. Their sealing ability is assessed in terms of the effectiveness E, which describes by how much the air curtain reduces the exchange flow compared to the open-door situation. Previous work studied the air curtain effectiveness when the doorway is the only means of ventilating a space. In this talk we examine effects of an additional displacement ventilation pathway on the effectiveness. The main controlling parameter is the deflection modulus D_{m} which is the ratio of the momentum flux of the air curtain and the transverse forces due to the displacement ventilation. For small values of D_{m} the air curtain is drawn inside the space by the ventilation flow. For high values of D_{m} the flow is controlled by the air curtain. A smooth transition occurs between these two regimes. Our model makes a quantitative and qualitative prediction of the E(D_{m}) – curve. Laboratory experiments were conducted to test the proposed model. The experimental data were compared to theoretical predictions and good agreement was found.