Turbulent Rayleigh-Bénard convection of compressed gas: effect of sidewall thermal conductance

Abstract Turbulent Rayleigh-Benard convection is experimentally studied for 1.96 × 10 9 ≤ R a ≤ 1.36 × 10 12 to assess the effect of sidewall thermal conductance on Nusselt numbers and propose a simple yet novel experimental method that eliminates the requirement to correct for this effect. The proposed method relies on power input to a large central-heater located far from the sidewalls for estimating the experimental Nusselt numbers. Experiments are carried out using test cells of varied aspect ratios (width to height, A R ( L / H ) = 0.61 , 1 , 2 ) placed inside a pressure vessel filled with compressed gas. Nusselt numbers obtained using the proposed experimental method are then compared with the sidewall-corrected Nusselt numbers estimated using two semi-analytical models from the literature. This comparison is found to yield a reasonable agreement (to within ± 8.6 % ) with both the models. Results from the present study are also presented in the form of a Nusselt number - Rayleigh number relation for the investigated range of parameters.