A Model To Predict Liquid Holdup and Pressure Gradient of Near-Horizontal Wet-Gas Pipelines

Abstract

Summary A mechanistic two-fluid model with new closure relationships is proposed to predict liquid holdup and pressure gradient of stratified flow. The proposed closure relationships include correlations of wetted-wall fraction factor, liquid-wall friction factor, and interfacial-friction factor. An iterative calculation procedure is implemented to solve for liquid holdup and pressure gradient for a given set of operating conditions, pipe geometry, and fluid properties. Two sets of facilities, a small-scale facility with 51-mm internal diameter (ID) and a large-scale facility with 150-mm-ID test sections, were used to tune the model. Superficial gas and liquid velocities were varied from 5 to 25 m/s and 0.00025 to 0.03 m/s, respectively, in the small-scale facility while they were varied from 7.5 to 21 m/s and 0.005 to 0.05 m/s, respectively, in the large-scale facility. The pipe inclination angle varied from −2 to 2°. The liquid holdup was ranged between 0.003 and 0.12, emphasizing the low-liquid-loading two-phase flow. The tuned model performance was then benchmarked against the high-pressure (up to 90 bar) SINTEF-stratified flow data. The model predictions agreed well with measured values of liquid holdup and pressure gradient. The comparison between the present model and OLGA® (a commercial transient multiphaseflow simulator by Scandpower Petroleum) performance was also presented.