Hydrodynamics and mass transfer of liquid-liquid two-phase flow in circular milli-channels: Sizing-up effect

Background: Microfluidic is one of the most promising technologies for safety production in chemical industry while scale-up is a major challenge for its industrialization. Methods: In this work, hydrodynamics and mass transfer of liquid-liquid two-phase flow in different circular milli-channels were experimentally and numerically studied to investigate the sizing-up effect. Significant findings: Slug flow was observed in toluene-water system and the droplet length was measured. The results showed shorter droplets tended to present under higher flow rates, inlet mode one and smaller T-mixers. The buoyancy exerted on the toluene phase accelerated droplet detachment. For n-butanol-water system, a repetition of ‘parallel flow - annular flow’ was observed due to the prominent gravitational effect. The flow was asymmetric and the phenomenon was especially notable in the serpentine channel with a larger diameter. The detailed velocity field was demonstrated by numerical simulation. Mass transfer enhancement was observed in smaller channels and serpentine channels, resulting from shorter diffusion distance and secondary flow, respectively.