Pressure drops and mixture friction factor for gas–liquid two-phase transitional flows in a horizontal pipe at low gas flow rates

Abstract In this work, we investigate the behaviors of gas–liquid two-phase flow in a horizontal pipe under the transition from laminar flow to turbulence at low gas flow rates. The variations of frictional pressure drop gradient with different liquid flow rates and volumetric gas quality are obtained experimentally and verified theoretically by two separated models. Then, the critical Reynolds number is found for different volumetric gas quality. The composite correlations between the friction factor and Reynolds number are proposed for two-phase transitional flows, and the dependence of friction factor on volumetric gas quality is determined. Finally, the flow field inside the pipe are analyzed by numerical simulation. The results reveal that the influence of gas flow rates on the pressure drop is more significant for higher liquid flow rate, the composite correlations for the mixture friction factor fit well with experimental data and can be described by the logistic dose–response curves.