Mechanistic modeling of liquid entrainment in gas in horizontal pipes

Entrainment in annular flow in horizontal pipes has been studied experimentally and theoretically. It has been found out that wave characteristics and entrainment fraction are strongly interrelated and must be utilized together in any related analysis.; A novel mechanistic model has been developed for the prediction of entrainment fraction based on wave characteristics. The model consists of three sub-models, namely, onset of entrainment, maximum entrainment and entrainment values in between. Comparison between the model prediction and the acquired experimental data shows an absolute average error of 3.5 and standard deviation of 4.1. Similar evaluation of existing entrainment fraction correlations reveals absolute average errors between 13.3 and 44.1 with standard deviations of 15.8 and 61.6.; Two experimental facilities, 2-inch and 6-inch diameter, have been designed, constructed and utilized for entrainment measurements in stratified and annular horizontal flow. Appropriate instrumentation for entrainment (adjustable liquid film extractor) and liquid film characteristics (conductance probes and multi-channel conductivity meter) measurements have been developed and implemented. The effects of fluid properties on entrainment and wave characteristics have been studied by utilizing air-water-Butanol (surface tension effects) and air-water-Glycerin (viscosity effects). Simultaneous measurements have been carried out for both wave characteristics and entrainment for a wide range of flow conditions.; Closure relationships have been developed based on the data for wave celerity, frequency, amplitude and spacing. The entrainment fraction has been normalized with respect to the maximum entrainment fraction and correlated with the ratio of the superficial gas velocity to the superficial gas velocity at the onset. The wave amplitude (Deltahw) normalized by the film thickness (hL) tends to values of Deltahw/hL = 0.2 to 0.3 for high gas rates. The wave spacing (Lw) for air-water normalized by the mean film thickness (hL) exhibits a clear linear behavior with gas velocity, almost independent of the liquid velocity.; It is recommended to conduct tests at high pressures with air-water or natural gas-oil measuring both the entrainment and wave characteristics, and extend the developed model to those conditions.