A new approach to analyze entrance region mass transfer within a falling film

Abstract A boundary layer model is developed to analyze diffusion through a laminar falling film for incomplete penetration of the dissolved gas. Regarding the rather intractable nature of the problem, Kantorovich Integral Method is chosen. Accordingly, a mass transfer boundary layer is assumed to keep growing perpendicularly to the falling film until it hits the wall. Such an approach is superior to its preceding artworks based on Higbie’s penetration theory in terms of implementation of more realistic conditions/modeling assumptions. Furthermore, unlike penetration model, this approach gives a criterion whether the diffusion is complete. Comparing the two models, boundary layer model estimates up to 2.3 % larger mass transfer coefficients. Moreover, a sensitivity analysis of liquid velocity distribution upon Sherwood number is conducted. It is found that the local velocity at gas–liquid interface is of highest dominance. Experimental data of SO2 absorption in water reported in literature is exploited to validate the model. It is shown that boundary layer model better fits the experimental data.

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