Mixed convection in a ventilated enclosure

Abstract

This paper presents analysis, visualizations and differential pressure measurements of the flow within a confined ventilated space resulting from a buoyant turbulent 2D plume originating at the bottom of the enclosure with initial source volume flux, Q 0 and buoyancy flux, B 0. The enclosure is ventilated through lower and upper openings of heights H E and H S separated by a vertical distance H. Simple analysis shows that flow regimes between the interior and the exterior of the enclosure depends on a densitometric Froude number Fr ¯ H = Q 0 2 / ( Δ ρ ¯ H / ρ ) gH ( C S A S ) 2 related to the source flow rate, the density inside the enclosure and the area of the upper opening. For Fr ¯ H < 2 , a displacement regime is observed with inflow at the lower opening and outflow at the higher opening. For Fr ¯ H > 2 , the regime is blocked with two outflows. When the enclosure is well mixed the value Fr ¯ H = 2 corresponds to the criteria given by Woods et al. (2003). Experiments show that the natural regime is observed for Fr ¯ H < 2 while the blocked regime appears when Fr ¯ H > 2.6 . There is an intermediate regime for 2 > Fr ¯ H > 2.6 . This last regime where inflow and outflow are both present through the lower opening is due to the non negligible size of this opening not taken into account in the analysis.