Natural Convection of Cold Water in a Vertical Annulus With Constant Heat Flux on the Inner Wall

A numerical solution for steady laminar natural convection of cold water in a vertical annulus with a constant-heat-flux heated inner wall and an isothermally cooled outer wall is examined. Results are generated for flow in annuli with aspect ratio 0.5 ≤ A ≤8, the radius ratio varying between 1.2 and 10, and the density inversion parameter ranging from −2 and 1 for 10³ ≤ Ra* ≤ 106. The heat and fluid flow structures of cold water are vividly visualized by means of contour maps of heatlines and streamlines. The results clearly indicate that the mixed boundary conditions considered can have a significant influence on the geometric dependence of heat transfer characteristics and fluid flow structures in comparison with those reported for isothermal boundary conditions. Multicellular flow behavior of cold water can arise in a tall annulus of A = 8.