Oxygen transfer from growing bubbles: Effect of the physical properties of the liquid

Mass transfer from bubbles generated at dispersion devices is a major operation in chemical engineering. Most mass transfer models have focused on the free rising of the bubbles, but the bubbling process plays an important role because it determines the bubbles’ initial volume, surface area and oscillation amplitude. In this work, the mass transfer mechanism and the shape of a single growing bubble are studied by combining a hydrodynamic model and a mass transfer model, given by Higbie's theory. The complete model has been tested using both, Newtonian and non-Newtonian fluids. Calculated bubble shapes, areas, volumes and detachment times are compared with those recorded by a high speed video camera device in a deoxygenated media. Good agreement is achieved between the results of the models and the experimental recordings. Furthermore, the effect of the physical properties of the liquid, viscosity, density and surface tension, on the Sherwood number of a growing bubble has been studied using the theoretical model. The liquid viscosity and the surface tension increase the Sherwood number meanwhile the liquid density reduces it. A dimensionless expression for the Sherwood number in terms of the Reynolds and the Schmidt numbers has also been developed.