Quasi-Steady Laminar Film Condensation of Steam on Copper Spheres

An experimental study of laminar film condensation of steam on copper spheres of 1.90, 2.54, and 3.17 cm dia has been made. Experiments have been performed by submerging cold spheres in nearly stagnant water vapor at a saturation temperature of about 99° C. Values of Nusselt number based on average heat transfer coefficient are obtained for saturation to wall temperature differences of 5–65° C and for cp ΔT/hfg in the range of 0.009–0.12. The data are compared with the steady-state predictions of Dhir and Lien-hard and of Yang. Analysis has been made to show that it is valid to use steady-state solutions in quasi-steady condensation as long as the dimensionless thermal diffusion time constant is small, and the film does not move very slowly.