Two-phase flow regimes for counter-current air-water flows in narrow rectangular channels

A study of counter-current two-phase flow in narrow rectangular channels ha s been performed. Two-phase flow regimes were experimentally investigated i n a 760 mm long and 100 mm wide test section with 2.0 and 5.0 mm gap widths . The resulting flow regime maps were compared with the existing transition criteria. The experimental data and the transition criteria of the models showed relatively good agreement, However, the discrepancies between the ex perimental data and the model predictions of the flow regime transition bec ame pronounced as the gap width increased. As the gap width increased the t ransition gas superficial velocities increased. The critical void fraction for the bubbly-to-slug transition was observed to be about 0.25. The two-ph ase distribution parameter for the slug flow was larger for the narrower ch annel. The uncertainties in the distribution parameter could lead to a disa greement in slug-to-churn transition between the experimental findings and the transition criteria, For the transition from churn to annular flow the effect of liquid superficial velocity was found to be insignificant.