Experimental PIV and interferometric analysis of natural convection in a square enclosure with partially active hot and cold walls

In this paper a PIV and Holographic interferometry measuring campaign on natural convection in a square cavity (side H = 0.05 m) filled with air at atmospheric pressure (Pr = 0.71) is presented. Two strips (cold and hot) are applied on the vertical sides of the enclosure; tests involve three different configurations, with the hot strip in the middle of one wall, and the cold strip at the bottom, in the middle or at the top of the opposite wall. For each configuration measures are performed with different temperatures of the hot strip. The aim of the paper is to investigate the relation between dynamic and temperature fields and to describe how the flow and the heat transfer inside the cavity are influenced by the temperature of the hot strip and the position of the cold strip. Velocity maps, streamlines maps and interferograms are presented; the average Nusselt number and an expression of Nu(Ra) for each configuration are calculated. Results show that the configuration with the cold strip at the top of the wall produces the fastest dynamic field and the highest Nusselt number.