Direct numerical simulation of bubble-liquid mass transfer coupled with chemical reactions: Influence of bubble shape and interface contamination

This work deals with the study of bubble-liquid mass transfer coupled with chemical reactions. The absorption of carbon dioxide in aqueous solution of sodium carbonate and bicarbonate is used as a reference case. The influences of the interface contamination state and of the ellipsoidal shape of the bubble on the mass transfer rate are studied using a two-dimensional (2D) axisymmetric model. On the one hand, the case of a spherical bubble with a partially contaminated interface is investigated. It is assumed that a fixed stagnant cap lies on a part of the bubble surface in the rear. On the other hand, the case of an ellipsoidal bubble with a clean interface is investigated. irst stage, correlations to estimate the transfer rate without reaction are presented and compared to the 2D model results. In a second stage, the mass transfer rate is computed with chemical reactions for several reaction rates. The influences of the coupling reactions – contamination state and the coupling reactions – ellipsoidal shape are then presented and discussed. These 2D model results are also compared to mass transfer rate estimations based on classical one-dimensional (1D) models. It is shown that 1D approaches are useful to provide a rough estimation of the mass transfer rate but 2D models have to be used when an accurate estimation of the mass transfer rate is required.