Dimensionless analysis on liquid-liquid two-phase flow patterns in a numbered-up microfluidic device

Flow patterns of six liquid-liquid systems in a numbered-up microfluidic set-up were studied in this work. Chloroform-water, butyl acetate-water, ethyl acetate-water, kerosene-water, butanol-water and octanol-water were chosen as test liquids. Three distinct flow regimes were observed in the parallelized microfluidic device: slug flow, droplet flow and parallel flow. A uniform flow distribution was achieved in the scaled-out microfluidic device for all observed flow regimes. Flow non-uniformity was determined based on both the volumetric flow rate and slug size/droplet size/interface position for each microchannel. The two-phase interface's position relative to the microchannel walls was considered a criterion for flow non-uniformity measurement in parallel flow. A comprehensive dimensionless analysis was also performed to determine which dimensionless numbers are appropriate for presenting universal flow maps. Re--0.(31), We(0.)(41), We(0.)(07)Ca(0.31), (ReCa0.41)-Ca-0.-Ca-07, Ca(0.5)Oh(-0.)(14), We(0.)(25)Oh(0.)(31) and Re(0.5)Oh(0.32) were identified as the suitable combinations of dimensionless numbers for proposing generalized flow pattern maps for the numbered-up set-up. For the slug and droplet flow regimes, slug and droplet length and velocity were also investigated.