Experimental study and modelling of developing intermittent slug flow in inclined annular pipelines

Abstract

Geometric arrangements known as flow patterns are typically observed when there are multiple immiscible fluids flowing through any control volume. The adequate modelling of the flow characteristic is important, especially in applications where flow visualization is not possible due to field constrains, like, for instance, in oil production. Intermittent slug flow occurs frequently in petroleum production systems and there is a lack of understanding of its characteristics in inclined annular geometries. Even though this is a frequent geometry encountered in the production system, there is lack of in-depth experimental studies about it. Moreover, existing models for calculating the slug frequency in vertical annular duct cannot predict the slug frequency in inclined annular duct. In this work, a dedicated experimental apparatus equipped with flow meters and a high-speed camera was built in order to investigate some characteristics of the slug flow in slightly inclined annulus, mainly the drift-flux parameters and the frequency of the slug. It is shown that modified drift-flux models for vertical annular flow can be used to calculate drift-flux parameters in inclined annular flow. In addition, a new model is proposed for calculating the slug frequency with improved accuracy when compared to the models available in the literature. The proposed model is suitable for industrial applications in the design of equipment in which such duct geometry is present.