Mutual inter-bubble influence in dynamic flow: CFD analysis of gas–liquid mass transfer efficiency

This paper presents a study of the behavior of a group of gas bubbles in a liquid flow and their mutual influence on mass transfer. This study is a development of a previous analysis of the influence of the shape of a single bubble on mass transfer parameters in multiphase media: the new study examines the influence of gas content (volume fraction of gas in liquid) and the mutual arrangement of bubbles on gas transfer from bubbles to liquid. The results obtained show that at high flow intensity and a large number of bubbles, an increase in the total interfacial contact area does not necessarily lead to a proportional increase in the mass transfer coefficients kL k L and the volumetric coefficient kL a k L a . Moreover, the efficiency of gas dissolution per bubble may decrease. Illustrative simulations of the distribution of dissolved gas concentration around a group of bubbles demonstrate that the concentration “trail” from a single bubble in an intense flow can cast a diffusion shadow, creating a diffusion shielding effect that affects neighboring bubbles and the group dynamics as a whole. A steady-state mass transfer regime is not established: the relationship between bubbles and dynamic interactions leads to constant fluctuations in concentration fields. The data obtained are important for understanding large-scale gas–liquid systems: it has been shown that the mutual location of bubbles and their collective dynamics significantly affect the efficiency of gas dissolution in liquid, and these effects must be taken into account, including when evaluating mass transfer in real systems.