Enhancing mass transfer in falling liquid films: The impact of sharp-edged microstructures

The objective of this study is to analyze the mass transfer efficiency into liquid films overflowing sharp-edged micro structured surfaces using numerical simulations. The investigated microstructures are rectangular and triangular in shape, with heights and widths of 0.5 and 0.75 times the Nusselt film thickness, respectively. The fluid dynamics and phase separation are described using the Navier–Stokes and Cahn–Hilliard equations with the addition of mass transfer equations for a dilute species. In this work we study the absorption and mass transport of a solved species from the gas phase into the liquid film. To gain insight into the various effects on mass transfer, a comprehensive numerical investigation is conducted with varying Reynolds number, Schmidt number and Henry number for each microstructure. The results indicate that the deformation and constriction of the film flow, resulting from the introduction of the microstructure, is a crucial factor influencing mass transfer efficiency. Depending on the hydrodynamics and the flow regime, the microstructure must be chosen carefully to actually enhance the mass transfer. • Numerical scheme for CHNS model including the mass transfer of a soluble species. • Validation against well-known analytical solutions for mass transfer into a liquid film. • Fully resolved mass transfer study solved simultaneously with fluid dynamics. • Influence of microstructures studied under varying physical conditions. • Mass transfer efficiency of structured surfaces compared to smooth surface. • Novel insights on the influence of microstructures.