Modeling of interfacial shear for gas liquid flows in annular film condensation

Internal flow of pure vapor experiencing film condensation on the walls of a straight horizontal duct is studied. The commonly occurring annular case of turbulent (or laminar) vapor flow in the core and laminar flow of the liquid condensate—with or without waves on the interface—is emphasized. We present a new methodology which models interfacial shear with the help of theory, computations, and reliable experimental data on heat transfer rates. The theory—at the point of onset of condensation—deals with issues of asymptotic form of interfacial shear, nonuniqueness of solutions, and selection of the physically admissible solution by a stability type criteria. Other details of the flow are predicted with the help of the proposed modeling approach. These predictions are shown to be in agreement with relevant experimental data. The trends for film thickness, heat transfer rates, and pressure drops are also made available in the form of power-law correlations