A computational study of the pseudosteady-state two-dimensional natural convection within spherical containers is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables. Natural convection effect is modeled via the Boussinesq approximation. Parametric studies were performed for two Prandtl numbers of 4.16 and 10.26. For each Prandtl number, the Rayleigh number was varied in order to cover the laminar regime adequately. Under pseudosteady-state conditions, the fluid heated adjacent to the surface rises replacing the colder fluid which sinks downward. As buoyancy-induced convection effects become more dominant, the temperature contours' deviations from concentric ring patterns (limiting case of zero Rayleigh number) become more marked. As the Rayleigh number increases, the fluid motion is more intensified. The radial location of the eye of the recirculation pattern is found to be dependent on the Rayleigh number. Local heat transfer rates near the bottom of the sphere is very marked in comparison to the top of the sphere. The heat transfer rates near the top are independent of the extent of natural convection, whereas gravity-induced fluid motion greatly enhances the heat transfer rate near the bottom. The mean Nusselt numbers exhibit an extremely weak dependence on the Prandtl number. Finally, flow and temperature field details during the transient evolution to the pseudosteady-state are presented. It is shown that the dominant transport mechanism at the early stages is due to heat conduction. At any instant, the heat transfer rate is greater near the bottom of the sphere. In contrast, the local heat transfer rate is lower near the top. As time progresses, the difference between the heat transfer rates near the top and bottom become more pronounced.
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