Experimental study of natural convection in thin horizontal liquid layers

Abstract

Heat transfer through a very thin horizontal liquid layer bounded on top by a cooled glass plate and on bottom by a heated copper plate was measured. Results were correlated in terms of Nusselt number as a function of Rayleigh number. Three different liquids were used under conditions to give a range of Rayleigh number from 350 to 4100 and Prandtl number from 34 to 477. Up to a critical condition heat is transferred by conduction alone. Convection appears when Ra = 1600 ± 100. A correlation for critical Rayleigh number as a function of Prandtl number was obtained.