Nonintrusive experimental study of natural convection in an open square cavity at different inclinations

In this paper, a natural convection study of an open square cavity is carried out in order to un-derstand the heat transfer and the fluid flow inside the cavity. The rectangular cavity considered in this work has a square cross section and is made of two adiabatic walls and an isothermal wall. The thermally active wall is maintained at a relatively higher temperature than the ambient temperature. Experiments are performed for three different Rayleigh numbers for five different inclinations (from side wall open to top wall open) with air (Pr = 0.71) as the working flu-id. A nonintrusive optical technique (Mach–Zehnder interferometer) is employed to capture the depth-averaged two-dimensional steady-state temperature field in the cavity. In addition to that, smoke visualization is also carried out to see the flow behavior inside the cavity. The physics of fluid flow has been discussed with the help of interferograms, corresponding two-dimensional temperature field, and smoke visualization results. The losses due to natural convection at different orientations have been quantified and are presented in terms of Nusselt numbers on the thermally active wall. The average heat transfer rates on the thermally active wall are found to be dependent on the orientation of the cavity. As the cavity is rotated such that the open face moves from the side to top, it is noted that the average Nusselt number decreases. However, when the opening of the cavity is at the top, there is a sudden increment in heat transfer due to Rayleigh–Benard convection in the cavity. The experimentally obtained average Nusselt numbers have been compared with those obtained by numerical simulations and good agreement between these two results is seen. The study reveals that higher driving potential for the higher angle of inclination led to higher heat transfer.