Laminar Combined Convection in a Horizontal Annulus Subject to Constant Heat Flux Inner Wall and Adiabatic Outer Wall

Steady-state, fully developed velocity and temperature fields in mixed convection through a horizontal annulus (ratio of outside to inside radii of 1.25), with a prescribed constant heat flux on the inner cylinder and an adiabatic outside cylinder are analyzed using finite difference approximations. The effects of the buoyancy-driven lateral flow on the temperature of the inner surface are studied in detail. The results show that, as the buoyancy potential (Rayleigh number) increases, the lateral flow structure changes from one cell (on each side) to two cells. The consequence of these flow regimes is that as Rayleigh number increases the temperature of the upper portion of the inner cylinder first increases significantly above its value for pure forced convection and then decreases significantly as the number of cells increases. The average temperature of the inner cylinder decreases monotonically as the Rayleigh number increases.