CFD Simulations of Low Liquid Loading Multiphase Flow in Horizontal Pipelines

Low Liquid Loading is a very common occurrence in wet gas pipelines where very small amounts of liquid flow along with the gas, mainly due to condensation of hydrocarbon gases and water vapor. The effects of low liquid loading on different flow characteristics, and flow assurance issues such as pipe corrosion prove the necessity of analyzing the flow behavior in more depth. In this study, CFD simulations are conducted for a horizontal pipe where liquid and gas are supplied at separate constant rates at the inlet. The liquid is introduced at the bottom to help shorten the developing section. The simulations are conducted with Ansys Fluent v14.5 using Volume Of Fluid (VOF) as the multiphase model. The analysis targets, mainly, the shape of the interface, velocity fields in both liquid and gas phases, liquid holdup, and shear stress profile. On the other hand, experiments are conducted in a 6-inch ID low liquid loading facility with similar testing condition. Experiments are conducted with water or oil as the liquid phase for a liquid volume fraction range of 0.0005–0.0020 of the inlet stream. For all cases, several flow parameters are measured including liquid holdup and interface wave characteristics. A comparison is conducted between CFD simulation results, model predictions, and experimental results, and a discussion of the sources of discrepancy is presented. Overall, the results help understand the low liquid loading flow phenomenon.