Mass transfer across the falling film: Simulations and experiments

Mass transfer across the thin falling film gas–liquid interface is a very important process as in chemical engineering and other fields, and yet there is still a lack of general predictability of the transfer quantity based on basic hydrodynamic parameters and independent of the geometrical setup. In this work, a numerical simulation is carried out for a vertical falling film arrangement. The wave dynamics and the associated mass transfer phenomena are discussed and compared with previous experimental empirical relationships. Based on the validity of the simulated results for wave parameters, numerical experiments for mass transfer were carried out with the aim of comparing to the empirical relation based on a single hydrodynamic parameter ββ (the gradient of the vertical fluctuating velocity at the interface) established previously by Law and Khoo [2002. Transport across a turbulent gas–liquid interface. A.I.Ch.E. Journal 48(9), 1856–1868.] and Xu et al. [2006. Mass transfer across the turbulence gas–water interface. A.I.Ch.E. Journal 52, 3363–3374] with various non-falling film   experiments. Separately, experiments in an inclined plate thin falling film apparatus were carried out to determine the ββ distribution and associated mass transfer. It is found that there is reasonable concurrence with the mentioned empirical relation, hence suggesting the general applicability of ββ characterizing the scalar transport across the gas–liquid interface independent of the means of turbulence generation.