Solidified crust formation and its effect on heat transfer between two separated horizontal liquid layers

Abstract

Experimental and analytical studies have been performed on conjugate heat transfer between two, separated, horizontal, liquid layers, with rapid solidified crust formation in a high density molten metal. Two cases of experiments, those with a low and high aspect ratio, in turn, were performed to analyze the effect of the aspect ratio and Rayleigh number on the crust formation. Two types of steady state tests, natural convection cooling and forced convection cooling, were performed to investigate the effect of coolant conditions in each of the aspect ratio case. The present experimental results on the relationship between the Nusselt number and Rayleigh number in the molten metal pool with and without crust formation were compared with existing correlations. The flow pattern, the temperature distribution, the crust thickness and the heat transfer rate have been evaluated using the CONV-2&3D and FLOW-3D computer programs and the numerical model in the analytical study. The experimental study has shown that the bottom surface temperature of the molten metal layer is the influential parameter in the solidified crust formation, due to the developed natural convection flow. If the natural convection flow is well developed in the molten metal pool region, the overlying coolant conditions do not affect the crust formation. The Nusselt number of experimental cases without crust formation in the molten metal pool region is greater than that of experimental cases with crust formation, due to the crust``s action as a conducting thermal barrier. The forced convection cooling more substantially affects the natural convection heat transfer rate than the natural convection cooling in the molten metal pool with and without crust formation. It is concluded that the present results, on the relationship between the Nusselt number and Rayleigh number in the metal pool region, match well with the Globe and Dropkin``s correlation. The natural convection heat transfer of the low aspe...