A high-speed camera was used to visualize and determine the size of formed droplet for liquid-liquid two-phase flow in the T-junction microchannels with different aspect ratios.Microchannels with different dimensions of 400 μm×400 μm

400 μm×600 μm

400 μm×800 μm in depth and width were used in this work.Cyclohexane and deionized water with 0.3% surfactant sodium dodecyl sulfate (SDS)-glycerol (20%

40%

60%) were used as the oil (dispersed) and water (continuous) phases

respectively.The effects of microchannel geometry

flow rates of both phases and physical properties of fluids on the size of droplet formed were investigated in the slug

transient and droplet regimes.The result showed that the droplet size decreased with increasing flow rate

viscosity and capillary number of the continuous phase

while it increased with increasing width of microchannels and flow rate of the dispersed phase.The correlations for predicting the size of formed droplet were proposed in taking capillary number

ratio of oil/water flow rates and aspect ratio of microchannels into account

and the calculated values by presented correlations agreed well with the experimental data.