INTERFACIAL TRANSPORT OF ENERGY IN LAMINAR OPEN CHANNEL AND FILM FLOWS

A new dispersion theory applicable to interfacial transport is used to analyze unsteady two-dimensional thermal pollution in laminar open channel and film flows. A strip source across the width of the flow at a variable depth is considered. The unsteady state temperature distribution depends on three time variable coefficients which are the convection, dispersion and exchange coefficients and expressions for these coefficients are derived from first principles. The exchange coefficient in the theory depends on time, the thickness and position of the source and the interfacial transport rate. Furthermore, the convection and the dispersion coefficients are affected substantially by interphase transport. The results, which are relevant to reactor design and such separation processes as chromatography, are discussed in physical terms and are compared to those for laminar flow in tubes. The theory can be applied readily to turbulent flow systems but computing the coefficients is a more formidable job. © 1979, Taylor & Francis Group, LLC. All rights reserved.