Reflux condensation of steam inside a short vertical large diameter tube

An experimental investigation of the reflux steam condensation inside a vertical tube at the atmospheric pressure is presented. The data were obtained for duralumin tube with the internal diameter of 200 mm, length of 220 mm and roughness height less than 0.05 mm. The film and vapor Reynolds numbers were varied within the range of 1-25 and 790-3680, respectively. The data were lower than Nusselt theory prediction. In contrast to Nusselt theory according to which the modified Nusselt number decreases with the film Reynolds number, the obtained data show inverse dependence when the film Reynolds number is less than ten. For fixed vapor Reynolds numbers there are the maximum values of the Nusselt number for definite film Reynolds numbers. The correlations are suggested for the Nusselt number in the case of a constant and variable wall temperature along the tube. The general correlation based on the presented and earlier published experimental data for the tubes with different height and diameter ratio is suggested in addition.