Drift-flux model for downward two-phase slug flow

Behavior of a single large bubble was experimentally studied in circular tubes of seven different diameters ranging from 9 to 38 mm for vertically downward flows of water and water solution of glycerin. The bubble velocity for co-current and counter-current flows was measured and correlated on the basis of the one-dimensional drift-flux model. Bubbles in the downward flow were unstable and asymmetrically located in the tube. This asymmetrical behavior was especially promoted in a turbulent flow. Consequently, values of distribution parameter and drift velocity differed from those of an upward flow. Comparison of parameters obtained in this study with those for the downward slug flow regime confirmed the applicability of the parameters to the slug flow. (author)