RESUMO

A two-phase flow across a vertically split U-type junction inside two 6.7 mm smooth tubes having curvature ratios of 3 and 7 was visually observed. The range of mass flux is 100−700 kg/m²·s. The gas mass flux in the upper and lower tubes is generally increased with the rise of gas quality while the distribution of liquid mass flux reveals a minimum and a maximum phenomenon. The gas mass flux in the lower tube is continuously increased with gas quality and is generally lower than that in the upper tube. However, its value may exceed that of its counterpart at the upper tube when semi-annular or annular flow takes place (x > 0.1). The surprising results can be attributed to the negligible influence of buoyancy, the airflow dragged by the gravity-induced liquid flow in the lower tube, and the liquid obstacle in the upper leg hindering the airflow path.