ABSTRACT
In many process applications, vapors often contain more than one molecular species, and some or all of these may condense. In this case, diffusion (with convection) in the vapor phase, leading to differences in temperature and composition between the “bulk” vapor and the vapor adjacent to the interface, is an important mechanism affecting the heat-transfer and condensation rates. The problem of laminar film condensation was first treated by Nusselt for condensation on an isothermal vertical plane surface and an isothermal horizontal tube. For the case of free-convection condensation, Nusselt invoked the additional assumption that the shear stress from the vapor on the surface of the condensate film was negligible. The condensate film first flows laminarly at the top portion of the surface, then changes to sine wave flow, harmonic wave flow, and finally to turbulent flow, if the length of cooling surface is long enough.
