Experimental Study of a Thermal Plume Evolving Inside a Rectangular Tunnel: Effects of the Source Height

Abstract

The aim of this work is to simulate experimentally a plume of fire placed at different heights evolving inside a horizontal tunnel, in order to determine the effect of the source site on the plume structure. The plume is produced from an electrically heated disc at a constant and uniform temperature. It is then placed inside the tunnel. First, we studied the evolution of the thermal plume while placing the source at a height above the ground. The study of the thermal and dynamic fields of the flow shows the existence of 3 zones during the vertical evolution of the thermal plume. In the first zone, the flow is strongly influenced by the presence of the thermal plume generating source. Followed by a second zone where the plume undergoes a contraction which prepares the flow to be passed in a third zone where the thermal plume divides into 2 parts by touching the ceiling. The first part (backlayering) moves towards the side blocked by the blower and the second moves towards the free side while going along the ceiling. We then determined the effect of the source site compared to the ground level on the behavior of the thermal plume inside the tunnel. For that, 3 sites of the source (h = 2 cm, h = 7, 5 cm and h = 15 cm) were studied. The comparative study shows that the structure of the flow is influenced by the site of the hot source. doi: 10.14456/WJST.2015.15