New correlation theory for steady natural-convective heat-transport data for horizontal annuli

A correlation theory, for two dimensional natural convective heat transport data for horizontal annuli of arbitrary cross section, was developed and applied to two configurations: (1) concentric cylinders and (2) an annulus formed by an inner hexagonal cylinder and an outer circular cylinder. Also embodied in the theory is the capability to predict the local and mean heat transfer. Thermal boundary conditions of the form T'x(M) can be accommodated. Data for the Rayleigh number varied from 10 to 10 to the 7th power, Prandtl number (Pr) varied from 0.7 to 3100, and the aspect ratio varied from 0.125 to 2.0. Even with these large variations, the present correlation theory collapses all the experimental data for the annular geometries to a single line. The theory is applicable to annuli of arbitrary cross-section. Therefore, the physical problem appears to be completely specified by a single equation when the thermal boundary condition, the fluid, the aspect ratio, and the Rayleigh number are known.