COMPUTATION OF FREE CONVECTIVE NUSSELT NUMBER FROM HORIZONTAL CYLINDERS USING EMPIRICAL DATA.

The natural convective heat transfer from a horizontal cylinder to a fluid is studied. A test cylinder of length 20 cm and diameter 53 mm was used. A thin wire with a diameter of 0.025 mm runs coaxially in a copper cylinder, which is maintained at a constant temperature of 540C by an electric current. The wire was exposed progressively to Toluene, methanol, acetone, air, argon, carbon dioxide, nitrogen, and oxygen at atmospheric pressure and at 230C. On a logarithmic scale, the Nusselt number is plotted against the Raleigh number using five traditional correlations; Kyte et al, Chu & Churchill, Kuehn & Goldstein, Raithby & Holland, Lykoudis & Yu, and Ben & Haque. Empirical data for Toluene, methanol, acetone, air, argon, carbon dioxide, nitrogen, and oxygen are plotted. The different correlations plotted fit the empirical data fairly well. The correlation proposed for this investigation provides the best fit