CHARACTERIZATION OF THREE-PHASE AIR-WATER-OIL FLOWS IN A DOWNWARD INCLINED PIPE: PRESSURE GRADIENT AND INTERFACIAL WAVE PARAMETERS

This work aims at characterizing flow patterns, pressure drop, and wave parameters of a three-phase air−water−oil flow through an experimental campaign conducted in a 40 mm inner diameter Plexiglas® pipe, inclined downward at 15°. Superficial velocities are investigated ranging from 0.75 to 2.25 m/s for air, 0.66 to 1.33 m/s for water, and 0.54 to 1.08 m/s for oil. The observed flow patterns are compared with the predictions from maps available in the open literature. The frictional pressure gradient and wave frequency are measured and evaluated against both mechanistic and empirical models. Additionally, images are used to assess other wave parameters, such as amplitude and wavelength. The results show good predictive accuracy for the wave parameters when correlated with gas−liquid Froude numbers. Moreover, the measured frictional pressure gradients are compared with the models proposed by Taitel & Dukler and Ullmann & Brauner, using eight different bulk viscosity correlations for the liquid mixture. Good agreement with experimental data is achieved when the Toshiba and Brinkman correlations are used to estimate, respectively, the oil holdup and the equivalent bulk viscosity of the mixture in the Taitel & Dukler model (MPE = 1.08%, MAPE = 16.85%).