Measurement of gas entrainment from stationary liquid slug in horizontal tube with double-sensor conductivity probe

Slug flow is encountered frequently in oil and gas pipelines. Stationary liquid slug was constructed in horizontal pipe to study the process of gas entrainment in a slug front and the two-phase flow parameters of liquid slug were measured by a double-sensor conductivity probe. It was found that the gas entrainment flowrate increases as the Froude number and Reynolds number of the liquid film ahead of the slug front increases. A turbulent shear layer exists in the mixing region and the radial distributions of void fraction and bubble frequency have peaks in the layer. As the distance into the slug increases, the void fraction and bubble frequency decrease and tend to be linearly distributed. The radial distribution of the bubble velocity indicates that the velocity gradient is high in the velocity boundary layer near the bottom of the pipe at the mixing region. The velocity profile agrees well with 1/7-th power law in the fully developed zone of the liquid slug.

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► Gas entrainment increases with increasing Fr and Re of the ahead liquid film.
► Gas bubble distribution of liquid slug is determined by turbulent shear layer.
► Radial distributions of void fraction and bubble frequency have peaks.
► The stationary liquid slug in horizontal pipe constitutes of four regions.