Experimental investigation on two-phase air/high-viscosity-oil flow in a horizontal pipe

The flow of very-viscous-oil and air through a horizontal pipe (inner diameter 22 mm) is experimentally studied. We first build and analyze the flow pattern map; a comparison between the air–water and the air–oil flow pattern maps shows a strong influence of the fluid properties. The experimental flow maps are compared with empirical and theoretical ones – Baker (1954), Mandhane et al. (1974), and Petalas and Aziz (1998) – showing a poor agreement. Experimental pressure gradients are also reported and compared with theoretical model, but also in this case the agreement is not very satisfactory. Finally, the elongated bubble velocity and length are measured and compared to model present in the literature. We conclude that the high viscosity of the liquid phase has a strong influence on the results and that the current models are not able to predict the flow features satisfactorily.

► The paper presents a new data set on high-viscosity-liquid/air flows through a horizontal pipe.
► Despite the large amount of work on two-phase flows, high-viscosity systems have been investigated only marginally.
► In this work, we present experimental flow maps, pressure gradient and dynamical feature of flow (bubble length and velocity).
► In addition, we compare our experimental results against the predictions of theoretical model widely used for water–air flows.