A numerical study of natural convection in concentric and eccentric horizontal cylindrical annuli with mixed boundary conditions

Abstract Numerical solutions are presented for steady laminar two-dimensional natural convection in concentric and eccentric horizontal cylindrical annuli with constant heat flux on the inner wall and a specified isothermal temperature on the outer wall. The heat and fluid flow patterns in the annuli are vividly visualized by means of the contour maps of streamlines and heatlines. Results of the parametric study conducted further reveal that the influence of the Prandtl number is quite weak; the heat and fluid flows are primarily dependent on the modified Rayleigh number and the eccentricity of the annulus. Above all, the specification of different thermal boundary conditions has a significant effect on the average heat transfer rate across the annulus.