Study of the Pressure Drop of Liquid–Liquid Slug Flow in a Circular Microchannel

In this paper, the pressure drop of liquid–liquid slug flow was studied. The effects of flow velocity, slug length, and interfacial tension on the pressure drop were investigated individually. Furthermore, the frictional and interfacial pressure drops were investigated. Computational fluid dynamics (CFD) simulation was used to modify the Hagen–Poiseuille equation to predict the frictional pressure drop with end effects. According to the findings, the interfacial pressure drop exhibits different characteristics for developing and fully developed slug flows. For the developing and fully developed slug flows, the interfacial pressure drop is considerably affected and unaffected, respectively, by the slug length and interfacial tension. These findings have not been reported in previous studies and cannot be well explained by the most commonly used pressure drop models. A criterion parameter was proposed to predict the transition of the developing slug flow to the fully developed slug flow. A new pressure drop model was established for the two flow patterns. The experimental results presented in this paper and other study can be well predicted using the new model, demonstrating its wide applicability.