Mechanistic Model for Eccentric Annular Gas-Liquid Flow in Horizontal Pipelines

A mechanistic model for the prediction of pressure drop in horizontal pipelines is presented for annular flow. A new empirical correlation for the liquid/wall interfacial friction is proposed, where the effects of the annular flow eccentricity, due to the difference between the fluid density and viscosity, are accounted for. The model is compared to three different correlation models and five mechanistic models in current use. Its accuracy has been validated against experimental data for annular gas-liquid flow in horizontal pipelines, taken from different sources. A number of 240 experiments were carried out with superficial liquid velocities between 0.003 and 5.96 m/s, superficial gas velocities between 9 and 69.6 m/s, liquid viscosities between 1 and 1200 cP, and pipeline diameters between 0.0261 and 0.0953 m. We find that the mechanistic model proposed here reduces the absolute error of the pressure drop prediction by approximately 20% compared to other mechanistic models.