Preparation of microbubbles with the generation of Dean vortices in a porous membrane

A platform based on gas–liquid membrane dispersion with helical internals inserted is developed for microbubble generation. The effects of internals on microbubble size are investigated, including circular, helical, twisted, and polygonal geometries. Parametric studies are conducted by varying the liquid flow velocity, liquid physical properties, geometric shape, helical pitch and thickness. Compared with membranes developed with other internals inserted, the membrane with helical internals has the highest performance for microbubble generation. The size of microbubbles decreases with increasing helical pitch and decreasing helical thickness in different liquid phases. CFD simulation is used to reveal the flow field with internals inserted into the membrane, which indicates that Dean vortices are effectively generated by inserting helical internals. An empirical correlation describing the microbubble size in the metallic membrane is developed considering the contribution of the gas–liquid ratio, capillary force and Dean vortices, showing good agreement with experimental data.