Two Phase Flow Pressure Drops in Sudden Contractions and Expansions

Abstract

Pressure drop through sudden expansions and contractions have been numerically investigated for two-phase flow of oil-water emulsions. Two-phase computational fluid dynamics calculations, using Eulerian–Eulerian model are employed to calculate the velocity profiles and pressure drops across sudden expansion and contraction. The oil concentration is varied over a wide range of 0-97.3 % by volume. From the pressure loss and velocity data, the loss coefficients are obtained. The loss coefficients for the emulsions are found to be independent of the concentration and type of emulsions. In the single phase flow of water and two-phase flow of oil-water emulsions vena contracta is always established at a distance of about 0.5D after the contraction section and depends only slightly on the concentration and inlet velocity of flow. Pressure drop across sudden contractions in pipes are also numerically investigated for two-phase air-water mixtures. Eight area ratios ranging from 0.0568 to 0.619 have been considered for the present computation. The mass flow qualities are varied from 0 to 97% and mass fluxes are varied from 500 to 4000 kg/m2/s. The effect of various parameters such as mass flux, mass flow quality, area ratios, flow directions (horizontal/vertical), system pressures etc on the two-phase pressure drops have been studied.