Effects of confining walls on laminar natural convection from a horizontal cylinder

The laminar natural convection from an isothermal horizontal cylinder confined between vertical walls is investigated by experimental and numerical methods. The experimental and numerical data are well correlated, independently, to equations which give the average Nusselt number in terms of the wall spacing to cylinder diameter ratio, t/D, and the Rayleigh number, Ra, for two different values of the wall height to cylinder diameter ratios, H/D=7 and 15.2. For the low Rayleigh numbers considered (Ra<1000), there are certain conditions for the confining walls under which heat transfer from the cylinder is maximum. Results are compared with the reported numerical and/or experimental results which show a reasonable agreement.