Influence of the Dufour and Soret effects on the characteristics of evaporating liquid flows

Abstract

The characteristics of regimes of two-layer flows with diffuse evaporation in an infinite channel are studied in the frame of the Boussinesq approximation for the Navier - Stokes equations. A joint flow of an evaporating liquid and a co-current gas flux is simulated with the help of the exact solution of a special type for the convection equations. The effects of thermodiffusion and diffusive thermal conductivity are additionally taken into account to model the flow in the gas phase and in the boundary conditions on the thermocapillary interface and upper solid wall of the channel. The character and extent of the impact of the Soret and Dufour effects on the structure of the appearing regimes of evaporative convection is investigated at the example of HFE-7100 - nitrogen and ethanol - nitrogen systems. It is shown that these effects do not influence the topological structure of the flows but can lead to a qualitative change of the regime pattern. The Soret effect can cause significant variations of the vapor content in the system upon changing the liquid layer thickness and external thermal load, and result in the transformation of the phase transition mode (evaporation/condensation). The influence of the Dufour effect can be neglected. Critical characteristics of the stability for the flow under study are determined depending on the intensity of the thermodiffusion effects. The weak destabilizing influence of the Soret effect is ascertained for all the considered configurations.