Experiments and modelling of three-phase vertical pipe flow

A set of two- and three-phase experiments were conducted in a 50 m long 400 vertical pipe using nitrogen, Exxsol D60 and water at 45 bara pressure. The results show that the liquid content and pressure drop are highly sensitive to the injected water cut. The proposed explanation for this surprising result is that the presence of liquid droplets constrains the gas bubble capacity of the liquid so that the concentration of small bubbles inside the liquid becomes smaller in three-phase flows than in two-phase flows. To test this hypothesis, a simple flow model was implemented using closure laws from the public literature, combined with the assumption that the concentration of gas bubbles is reduced by the presence of liquid droplets. The model shows that the observed three-phase effects can be reproduced very accurately using this assumption.