An experimental and numerical investigation to study slug characteristics in miniature geometries

This research presents the prediction of slug length in liquid-liquid two-phase flow using a straight mini capillary of an inner diameter of 2 mm. The study focused on understanding the effects of flow dynamics and thermophysical properties on slug characteristics. Three different combinations of glycerol in distilled water (v/v%) are used to vary the thermophysical properties of the continuous phase. While toluene is used as the dispersed phase. Droplet flow and slug flow are observed as the main flow patterns. The slug length is found to have a proportional relationship with the Reynolds number of the disperse phase while inversed relationship with the Reynolds number of the continuous phase. At a constant Reynolds number of the disperse phase, the specific interfacial area steadily declined with the Reynolds number of the continuous phase. A criterion is proposed for the transition of flow patterns in the form of dimensionless numbers. Further, numerical simulations are performed to understand flow physics at different thermophysical properties using the open software OpenFoam. The inner circulation inside the slug is observed to increase with a decrease in the glycerol content in the continuous phase. Based on experimental data, an artificial neural network model is developed to predict slug length. The results showed that the model successfully establishes the relation between the thermophysical properties of fluids, wall wettability of channel, and slug length. Further, the model is validated with the previously published data and present simulation, showing high accuracy.