Carbon dioxide (CO2) absorption and interfacial mass transfer across vertically confined free liquid film-a numerical investigation

•The mass transfer behaviour of confined free liquid film is investigated numerically.•The use of an open window can significantly enhance mass transfer performance.•Both inner vortices and interfacial vortices exist in a confined free film.•The local mass concentration and vorticity values are highly correlated.

CO2 absorption by a confined free film has been investigated using the CFD approach. Particular attention focuses on the relationship between mass transfer and flow behaviour of the confined free film. Simulation results show that the average KL value grows 26.9% for the open window region and 17.4% for the lower-wall region, respectively, in comparison to the values in the upper-wall region, and the average KL value of confined free film along the flow direction is about 19.2% higher than the value of wall-bounded film, which affirms that the use of an open window can significantly enhance mass transfer performance and such effect also has impact on the entire regions. It was revealed that there exist two types of vortices inside the film, inner vortices and interfacial vortices. In addition, a correlation coefficient RΩc is proposed to provide a quantitative measure to characterise the relationship between the local mass concentration profile and vorticity distribution of confined free film. Simulation shows that the average value of RΩc is 0.93, indicating that the two parameters are highly correlated. Furthermore, the cause of lower correlation coefficient value is discussed.

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