Onset of Liquid-Film Reversal n Upward-Inclined Pipes

Accumulation of oil and/or water at the bottom of an upward-inclined pipe is known to be the source of many industrial problems, such as corrosion and terrain slugging. Therefore, accurate prediction of the critical gas velocity that can avoid the liquid accumulation is of great importance. An experimental study of onset of liquid-film reversal, which is believed to be the main cause of liquid accumulation, was conducted in a hilly-valley test section at low-liquid-loading condition. A new, easily implemented mechanistic model to predict critical gas velocity, which is specifically developed based on the liquid-film reversal in stratified flow, is proposed in this work. The new model was verified with the data acquired in the study and other studies from the open literature, showing a fair agreement. This work also reviewed and evaluated other critical-gas-velocity-prediction models. The new model performs best compared with other models, especially in terms of the inclination angle and liquid-flow-rate effect on critical gas velocity. The total average absolute error was reduced 6.0% compared with the current best-prediction model (Zhang et al. 2003), and 38.2% for the widely used Turner et al. (1969) droplet removal model.