An Assessment of Void Fraction Predicting Methods for Gas-Liquid Two-Phase Flow in an Annulus

Gas void fraction plays an important role in the calculationofseveral multiphase flow parameters. The prediction of a void fractionfor gas-liquid two-phase flow in an annulus is needed by manydesign practices. In the present work, void fraction correlationsbased on the homogeneous method, slip-ratio method, and drift-fluxmethod are reviewed, and a total of 24 correlations, 8 for each group,are collected. A database covering 1136 experimental data points ofvoid fractions from 0.009 to 0.972 in an annulus is developed, withthe range of hydraulic diameters from 0.002 to 0.057 m, and the pipeinclinations from horizontal to vertical. The 24 correlations aretested against the entire database to evaluate their abilities inpredicting the void fraction of two-phase flow in annuli. It is foundthat no correlation studied here provides satisfactory agreement withthe whole database, and many correlations show good symmetry but withpoor concentration. A void fraction correlation for flow in annuliis proposed based on the drift-flux model with a new equation forthe distribution parameter. Comparison of the predicted value withthe experimental data shows good agreement.