Effect of Prandtl Number and Diameter Ratio on Laminar Natural Convection from Isothermal Horizontal Cylindrical Annuli

A numerical investigation of transient, two-dimensional natural convection in horizontal isothermal cylindrical annuli is performed to investigate the Prandtl number and diameter ratio effect on flow heat transfer characteristics. The finite difference method used solve governing equations, which buoyancy modeled via Boussinesq approximation. Both vorticity energy equations are solved using alternating direction implicit (ADI) stream function equation by successive over relaxation (SOR) method. Solutions for laminar case obtained up Grashof 105 as well three different ratios, namely 1.2, 1.5, 2.0 varies from 0.7 10 considered. computed patterns temperature fields shown means streamlines isotherms, respectively, average coefficients also presented. results summarized Nusselt vs. correlations with a parameter. parametric study show that have profound influence field they almost independent low fluid. increases 25% at large number. Good agreement earlier available data obtained.