The occurrence of slugging in pipes includes irregular and short hydrodynamic slugs, large regular terrain induced slugs and transient slugs resulting from pipeline operations (e.g. start-up or" change in production rates). When a liquid slug propagates in a pipeline gas is entrained at the slug front and can lead to very high gas fractions in the slugs. In mean, steady state slug flow models, relations for the gas fraction in the slugs are supplied as closure relations. For dynamic modeling of the behavior of individual slugs the gas entrainment rate at the slug front is required. This was the motivation for the design of transient experiments for simulation of entrainment processes in slug flow with controlled variation of all parameters. The gas entrainment rate into a liquid front that advances over a liquid film in a pipe has been measured for both oil and water flows. The experiments were made with different gas densities using air, helium, and freon as test fluids. Holdup was dynamically measured with an impedance ring method; conductance for water and capacitance for oil. The fluid properties effects on the measured entrainment rates seems to be weak. A difference is noted for the slip fraction of the dispersed bubbles in the liquid slug. Small bubbles move at about the same velocity as the liquid in an oil slug, but slower than the liquid in a water slug.
Gas entrainment into a liquid front that propagates in a pipe is a phenomenon of practical and fundamental interest. Aeration processes are of importance in many industrial processes involving pipe flow. The self aeration process offers pipe flow as an inexpensive and effective reactor in the chemical industry. The strong mixing between the phases and the large interface area enhance mass transfer processes.
