Interfacial friction in upward annular gas–liquid two-phase flow in pipes

•Gas–liquid two-phase flow experiments conducted in a large diameter flow loop.•Data were collected for interfacial friction factor in upwards annular flow regimes.•Data were also gathered from other sources spanning both small and large diameter pipes.•Previous correlations’ predictions deviated at high shear regions mainly for large pipes.•Improved correlation is proposed to fit the diverse database of more than 300 data points. Accurate prediction of interfacial friction between the gas and liquid in annular two-phase flow in pipes is essential for the proper modelling of pressure drop and heat transfer coefficient in pipeline systems. Many empirical relationships have been obtained over the last half century. However, they are restricted to limited superficial liquid and gas velocity ranges, essentially apply to atmospheric pressures, and the relationships are only relevant for pipes with inner diameters between 10 and 50mm. In this study, we carried out experiments in a large diameter flow loop of 101.6mm internal diameter with the superficial gas and liquid ranges of 11–29m/s and 0.1–1.0m/s respectively. An examination of published interfacial friction factor correlations was carried out using a diverse database which was collected from the open literature for vertical annular flow. The database includes measurements in pipes of 16–127mm inner diameter for the liquid film thickness, interfacial shear stress, and pressure gradient for air-water, air-water/glycerol, and argon-water flows. Eleven studies are represented with experimental pressures of up to 6bar. Significant discrepancies were found between many of the published correlations and the large pipe data, primarily in the thick film region at low interfacial shear stress. A correlation for the interfacial friction factor was hence derived using the extensive database. The correlation includes dimensionless numbers for the effect of the diameter across pipe scales to be better represented and better fit the wide range of experimental conditions, fluid properties, and operating pressures.