Pseudoplastic thin film flow

An experimental and theoretical study was conducted on thin film flow of pseudoplastic, non-Newtonian liquids down a smooth, vertical plate. Also, the stabilizing effect of nonionic surfactants on film flow, and co-current downward gas-liquid film flow were investigated. A boundary layer form of the equation of motion was solved to analyze experimental data on free flow. Satisfactory predictions for mean film thickness and directional effect of pseudoplasticity on friction coefficient were obtained. Predictions for the wave length were unsatisfactory. It was found that an existing equation, developed for stabilizing effects of surfactants on Newtonian thin film could be successfully applied to pseudoplastic films by using zero-shear rate apparent viscosity in place of Newtonian viscosity. In all cases there existed a surfactant concentration for which the stabilizing action was maximized. For co-current gas-liquid downward flow, measured values of pressure drop were up to five times higher than when gas flows alone, and depend highly on liquid shear properties.