Due to the recent upsurge of interest in suchprocesses as spray casting, latent-heat-of-fusionthermal storage systems, space radiators, spacecraftenergy conversion systems, rapid solidification,purification of materials, containerless levitationtechnique, etc., there is an urgent need to analyze thetransport phenomena of melting and solidification inspherical configurations. Only a few authors havestudied the transport phenomena with phase change in aspherical shape. The present work will utilize theSIMPLE procedure to solve the unsteady coupled fluidflow and heat transfer equations governing the meltingprocess. The fixed-grid method which utilizes singleformulations for different phases is used and thecoupling condition at the phase change interface isformulated into the governing equations. Thus, there isno need to track the moving interface and a fixed gridcan be used throughout the computations. An enthalpyformulation which can handle phase-change problemsoccurring both at a single temperature and over atemperature range will be utilized.A parametric study to assess the role of buoyancy-driven convection during melting within sphericalcontainers has been undertaken. Emphasis is placed onlow-Prandtl number liquid metals undergoing melting.The surface temperature of a solid spherical metalspecimen is raised to a value greater than its meltingtemperature. Melting will initiate at the surface andthe solid-liquid interface will move into the specimen.As the extent of the liquid state is increased,buoyancy-driven convection will be promoted and a skewedsolid-liquid interface will be observed. Detailedunsteady flow field information including velocityvectors, migration of the interface and temperaturecontours within the sphere will be plotted and discussedin the paper. Results will be compared to the limitingcase of diffusion-controlled melting.This research was partially supported by the US-CzechRepublic Science and Technology Program.
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