Liquid entrainment rates in annular two-phase flow in smooth tube

A simplified theoretical model is developed for prediction of the liquid entrainment rates in annular two-phase flow. Utilizing the understanding that liquid entrainment results from the generation of disturbance waves at the gas/liquid interface, an approximate model is developed to relate entrainment rate with the displacement of the wave surface. The dispersion equation relating the wave frequency and wave number was obtained by a linear analysis of an incompressible, potential, separated, two-phase flow. The linear homogeneous differential system describing the flow field requires a single independent constant (perturbation intensity) which can be specified in terms of the inlet conditions of the flow. Experiments were performed to measure liquid film flow rates and total entrainment rates in air-water two-phase flow. The data were then used to obtain a correlation for the perturbation intensity. The approximate theoretical model proposed in the present study satisfactorily describes the liquid entrainment rate as a function of the product of fluid density and the displacement of small disturbance waves