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

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 K_L 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 K_L 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 R_Ωc 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 R_Ωc is 0.93, indicating that the two parameters are highly correlated. Furthermore, the cause of lower correlation coefficient value is discussed.