Prediction of interfacial shear stress and pressure drop in vertical two-phase annular flow

•Experiments of annular flows with the gas–liquid density ratio of 32–434 and surface tension of 30.7–67.4 mN/m are performed.•Pressure drop, interfacial shear stress, and interfacial friction factor are comprehensively investigated and studied.•Disturbance wave height, linked to the equivalent sand-grain roughness, is found to be critical to the interfacial friction factor.•A correlation is proposed to predict the interfacial friction factor based on the analogy with the moody chart.•A model for pressure drop prediction is proposed and can predict the data under boiling water reactor operating condition. The interfacial shear stress and pressure drop of an upward vertical annular flow of nitrogen–water, HFC134a–water, and nitrogen–95 % ethanol solution were comprehensively investigated considering the effect of the liquid–gas density ratio and surface tension. A direct link between the disturbance wave height and equivalent sand-grain roughness was noted through the analogy with the famous Moody chart for single-phase turbulent flows. A predictive model of the interfacial friction factor was developed based on this finding. To predict the pressure drop of the annular flow, a new model with good predictive performance for annular flows of various working fluids including steam–water under boiling water reactor operating condition (286 °C and 7 MPa) was proposed.