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

Abstract

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-0.31We0.41, We0.07Ca0.31, Re0.07Ca0.41, Ca0.5Oh-0.14, We0.25Oh0.31 and Re0.5Oh0.82 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.