Phase Distribution for Air-water Two-phase Flow in Annuli

Abstract

Experimental data are presented on the phase distribution of air-water two-phase mixtures which flow vertically upwards in annular passages. Three annuli with different radius ratios, R₁/R₂ =5/13, 8/13 and 10/13, are used in the present experiments. Flow patterns observed in the annuli are first demonstrated. Next, two items characterizing void fraction distributions, i.e. void fraction near the wall and the position of the radius of maximum void fraction are discussed with attention paid to the effect of the passage width. Flow regimes concerned here-in cover bubbly, slug, froth and froth-annular or huge wave flow. Finally, an attempt is made to obtain a correlation for evaluating cross-sectional average void fraction. The proposed correlation is in good agreement with experimental values for both the annuli and a round tube.