Oberbeck-Boussinesq approximations and geometrical confinement effects of free convection in open cavity

An experimental study has been conducted on the free convection in an open cavity to investigate the effect of aspect ratio from 3.33 to 0.33 and Rayleigh number from 1.5x10(6) to 9x10(9). Also, the effect of different lateral dimensions (120mmx120mm and 240mmx240mm) of the bottom plate for free convection is studied. The validity of Oberbeck-Boussinesq approximation is also examined using the different approaches, such as fractional deviation in thermo-physical properties of working fluid, density variation, and Busse's parameter. The effect of aspect ratio and the Rayleigh number on the heat transfer efficiency in free convection is observed experimentally and a power law relation having the exponent of 0.30 expressed the change in the Nusselt number with Rayleigh number. The mechanism of heat transfer in different conditions is explained using the temperature distributions with respect to Rayleigh number.