Two-phase flow characteristics across sudden contraction in small rectangular channels

This study examines the two-phase flow pattern change and pressure drop at the sudden contraction from small rectangular channels (3 × 9 mm and 3 × 6 mm) into a 3 mm diameter tube. A unique deflection of contraction pressure drop vs. vapor quality is observed at a very low quality regime with an unusual “liquid like vena contracta”. The measured pressure drops are compared with existing correlations/models, but none of them can accurately predict the available database. By proposing a correction factor accounting for the influence of surface tension (Bond number and contraction ratio) to the original homogeneous model, considerable improvement of the predictive ability of homogeneous model is arrived. The mean deviation of this correlation is 26.18% applicable to the present data (80 points) and available literatures (357 points).