Two-phase flow modelling within expansion and contraction singularities

Abstract

An experimental study is performed in order to describe the single- and two-phase (air-water) horizontal flowin the presence of pipe expansion and contraction. Three types of singularities are investigated; smooth convergence and sudden and progressive enlargement. The opening angles for progressive singularities are 5, 8, 9 and 15 degrees. The surface area ratios tested are σ = 0.43, 0.64, 0.65 and 1.56. Bubbly flow is the dominant flow regime that is investigated for volumetric quality up to 30%. The pressure distribution for both single and two-phase horizontal flow is examined versus axial position. For expansion geometries, it is found that the smaller the enlargement angle, the larger the recovery pressure for the same flow conditions; the pressure drop caused by the singularity is higher in the case of a sharper expansion. The comparison of the experimental results to published models leads to a proposed corrective coefficient for Jannsen's correlation. Flow visualization is also performed; the flow patterns downstream from the different singularities are identified in each configuration and plotted in Baker's map for horizontal flow. © 2009 WIT Press.