An investigation of condensation from steam-gas mixtures flowing downward inside a vertical tube

This research investigates experimentally local heat transfer from condensation in the presence of noncondensable gases inside a vertical tube. Using a novel experimental apparatus for accurately measuring local heat fluxes, an extensive data base has been obtained for the condensation of pure steam, steam-air mixtures and steam-helium mixtures. Three different correlations, implementing the degradation factor method, diffusion layer theory, and mass transfer conductance model, are presented. The correlation using the simple degradation factor method has been shown to give satisfactory engineering accuracy. However, this method is based on very simplified arguments that do not fully represent the complex physical phenomena involved. Based on diffusion layer theory and a mass transfer conductance model, more physically based correlations were developed for the heat transfer of vapor-gas side. The total heat transfer coefficient predicted by the correlations from these two mechanistic models are in close agreement with experimental values. (C) 1997 Elsevier Science S.A.