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