ANALYSIS OF NATURAL-CONVECTION FILM BOILING FROM SPHERES USING THE SPHERICAL COORDINATE SYSTEM

The problem of natural convection film boiling on a sphere was analyse d by solving the momentum and energy equations in spherical coordinate s. These solutions were compared to the analytical model of Frederking and Clark based on the Cartesian coordinate system, empirical correla tion of Frederking and Clark and recent experimental data of Tso et al . for boiling in various refrigerants and liquid nitrogen. For the ave rage Nusselt number, good agreement with Frederking and Clark's model was obtained. Results using spherical coordinates yield a limiting val ue of 2 for the average Nusselt number near a modified Rayleigh number of 1 which could not be extracted from Frederking and Clark's model.