Hydrodynamics and mass transfer in liquid-liquid non-circular microchannels: Comparison of two aspect ratios and three junction structures

•Mass transfer using different aspect ratios and mixing junctions were compared.•KLa and KL in a square channel were higher than those in a rectangular channel.•Using a cross-shaped junction improved KLa up to 35 percent.•Effect of the junction structure on mass transfer was greater than the aspect ratio.

Hydrodynamics and mass transfer in liquid-liquid slug flow inside a square microchannel (MC-1, aspect ratio 1) and a rectangular microchannel (MC-2, aspect ratio 2) with identical hydraulic diameter (400 µm) were investigated experimentally. The results showed that the overall volumetric mass transfer coefficient (KLa) in MC-2 was 16.2% lower than that in MC-1 due to enlargement of the dispersed phase slugs in MC-2, leading to development of stagnant zones within plugs and reduction of wall film renewal. Three different junction configurations (JC) were studied. KLa was enhanced by up to 34.8% using JC-1, compared to JC-2 or JC-3 due to greater movement of the biphasic interface, resulting in higher mixing within slugs using JC-1. The junction arrangement influenced not only the mass transfer during the slug-formation stage, but also the slug-flowing stage due to effects on the vortex patterns along the microchannel.

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