STUDY OF LIQUID-LIQUID SLUG BREAK UP MECHANISM IN A MICROCHANNEL T-JUNCTION AT VARIOUS MODIFIED WEBER NUMBER

Abstract

The formation of immiscible liquid droplets, or slugs, in microchannels features the advantages of volume control and mixing enhancement over single-phase microflows. Although the applications of droplet-based microfluidics have been widely demonstrated, the fundamental physics governing droplet break-up remains an area of active research. This study defines an effective Weber (We_eff) number that characterizes the interplay of interfacial tension, shear stress and channel pressure drop in driving slug formation in T-junction microchannel for a relative range of low, intermediate and high flow rates. The immiscible fluid system in this study consists of Tetradecane slug formation in Acetonitrile. The progressive deformation of slug interfaces during break-up events is observed. Experimental results indicate that, at a relatively low We_eff, clean slug break-up occurs at the intersection of the side and main channels. At intermediate We_eff, the connecting neck of the dispersed phase is stretched to a short and thin trail of laminar flow prior to breaking up a short distance downstream of the T-junction. At a relatively high We_eff, the connecting neck develops into a longer and thicker trail of laminar flow that breaks up further downstream of the main channel.