RESIDENCE TIME DISTRIBUTION IN A WIPED LIQUID-FILM

The present work concerns the evaluation of experimental residence time distribution (RTD) curves obtained in a wiped liquid film formed on the surface of the evaporator cylinder of a molecular evaporator. The dependent variables in the study are the peripheral load and liquid viscosity. The wiping process is modelled by a cascade of apparatuses with laminar falling film ideally mixed at the exit from each stage in a mixer having zero thickness. The comparison of experimental and model data shows that the model developed explains well the actual processes taking place in the him wiped by a segmented wiper. By comparison of the shape of the experimental RTD curves with theoretical model curves, a criterion can be derived, indicating the efficiency of wiping.