Exploring the correlation between inclination angle and flow pattern transition in oil-water flow

Abstract

The impact of pipe inclination angle on oil-water flow regimes transition boundaries is vital in various engineering applications, including pipeline and separator inlet design. Understanding this influence is crucial for identifying alternative and optimal designs. The standard way of presenting oil and water superficial velocities on 2D flow pattern maps doesn't consider how the flow pattern varies with pipe tilt angle. This article aims to clarify how the angle of pipe inclination affects oil-water flow regime transitions. This method uses pipe inclination angle as a direct representation, with the angle shown on the x-axis of a 2D flow pattern map, which has not been done before in literature. The y-axis, or ordinate, is a dimensionless number that accounts for mixture velocity, fluid densities, and pipe diameter. Two dimensionless numbers were utilized. The Froude number based on mixture velocity, FrM, and the Reynolds number (ReOM) based on mixture velocity and oil properties, are plotted against pipe inclination angle. The evaluation and validation of the proposed methods for the effect of the inclination angle were performed using a database of more than 10,000 points established from studies reported in the literature. The findings show that both the Dispersed (DF) and Semi-Dispersed flow regimes (SDF) exhibit higher FrM values than smooth stratified regardless of the pipe's incline. Moreover, the spreading area is symmetric around the horizontal line which means that the DF and SDF can be observed at similar FrM for both positive and negative inclinations. Focusing horizontally, FrM is highest for ST-MI, lower for SW, and lowest for ST. This paper also presents and demonestrates a case study showcasing a new application for flow pattern maps, illustrating their potential in design purposes.