Numerical study of falling film absorption process in a vertical tube absorber including Soret and Dufour effects

Vapor absorption in aqueous LiBr inside a vertical tube absorber is studied numerically. The governing equations of concentration and energy have been derived in general forms, including the species interdiffusion, Soret and Dufour effects due to combined concentration and temperature gradients during absorption process. All thermophysical properties of solution and the heat of absorption are variable, as functions of temperature and concentration in constant absorber pressure. An in-house CFD code is used to solve the governing equations. The obtained results have been validated with available experimental data and a good agreement is observed. The simulation results reveal the important role of the interdiffusion term in energy equation. Moreover, the Soret and Dufour effects result in a relatively small increase in average heat and mass fluxes at the interface.