Hydrodynamics Of Liquid-Liquid Two-Phase Flow In Microchannels

Due to the complexity of the liquid-liquid two-phase system, theresearch remains still far from sufficient on the hydrodynamics in themicrochannel. This paper presented experimental investigations onhydrodynamics of Newtonian/Newtonian fluids andNewtonian/non-Newtonian fluids two-phase flow in T-junctionmicrochannels with three different dimensions (height(μm)×width(μm))400×400,400×600,400×800, respectively, by using a high-speed camera.And the pressure drops were measured by differential pressure sensors. Thecyclohexane was used as the dispersed phase, the Newtonian fluid(deionized water-glycerol solutions, glycerol:20wt%,40wt%,60wt%) andnon-Newtonian fluid (deionized water-carboxyl methyl cellulose (CMC)solutions, CMC:0.1wt%，0.25wt%，0.5wt%) with0.3wt%sodium dodecylsulfate were used as the continuous phases, respectively. The flow pattern，droplet size, velocity and pressure drop of two phase flow wereinvestigated.When the continuous phase was Newtonian fluid, the flow patternswere observed mainly as slug flow, droplet flow and parallel flow. When thecontinuous phase was non-Newtonian fluid, the flow patterns werevisualized as slug flow, droplet flow, parallel flow and jet flow. The flowregime maps and the flow pattern transition model were also developed andthe results showed that the larger was the viscosity of the continuous phaseand the smaller was dimension of the microchannels, the wider of thedroplet flow region.The droplet size and velocity could be remarkably influenced by theparameters, including the flow rates of two phases, the aspect ratio(height-to-width) of microchannels, the viscosity and capillary number Caof the continuous phase. The results showed that the droplet size decreasedwith increasing aspect ratio of microchannels, viscosity and capillarynumber of the continuous phase, while it increased with the increasing ofthe flow ratio (oil-to-water) in both systems. Droplet mobility increasedwith the increase of droplet size and capillary number of the continuous phase, while it decreased with increasing aspect ratio of microchannels andCMC concentration. When the continuous phase flow rate was given, thedroplet mobility increased with the increase of the dispersed phase flow rate.When the dispersed phase flow rate was given, the droplet mobility firstlydecreased and then increased with the increase of the continuous phase flowrate. The correlations were proposed for predicting the droplet size andmobility.In single-phase flow system, the pressure drop increased with theincrease of the aspect ratio of microchannels, fluid viscosity and the flowrate. In slug flow and droplet flow of the liquid-liquid two-phase system,the pressure drop decreased with the increase of the flow ratio and thedroplet size, while it increased with the increase of the aspect ratio ofmicrochannels, droplet velocity, the viscosity and capillary number Ca ofthe continuous phase. The pressure drop of parallel flow decreased with theincrease of the percentage of oil as well. The models containing superficialvelocity, physical properties and geometric of the microchannels for threedifferent flow patterns were developed to evaluate the pressure dropseparately, and the calculated results showed good conformity to theexperimental data.