Heat and mass transfer in annular liquid jets: I. Formulation

Heat and mass transfer phenomena in annular liquid jets are analyzed at hig h Reynolds numbers by means of a model derived from the governing equations that takes into account the effects of surface tension and boundary condit ions at the gas-liquid interfaces and the large differences between the the rmal and mass diffusivities,, densities, dynamic viscosities, and thermal c onductivities between gases and liquids. The model clearly illustrates the stiffness in both space and time associated with the concentration, linear momentum and energy boundary layers, and the initial cooling of the gases e nclosed by the jet when, starting from a steady state where gases are injec ted into the volume enclosed by the jet at a rate equal to the heat and mas s absorption rates by the liquid, gas injection is stopped. It is shown tha t, owing to the non-linear integrodifferential coupling between the fluid d ynamics and heat and mass transfer processes, the pressure of the gases enc losed by the jet may vary in either a monotonic or an oscillatory manner de pending on the large number of non-dimensional parameters that govern the h eat and mass transfer phenomena. For the underpressurized jets considered h ere, it is shown that thermal equilibrium is achieved at a much faster rate than that associated with mass transfer, double diffusive phenomena in the liquid may occur, and the mass and volume of the gases enclosed by the jet may increase or decrease as functions of time until a steady equilibrium c ondition is reached. (C) 2000 Elsevier Science Inc. All rights reserved.