Void fraction measurements of bubbly flow in a horizontal 90° bend using wire mesh sensors

Wire mesh sensors were used to investigate the void fraction distribution of two-phase gas-liquid bubbly flow in a 50.8 mm diameter horizontal test section containing a 90° bend. The 90° bend had a radius of curvature of 76.2 mm, and its inlet was installed at an axial distance of one hundred pipe diameters from the test section's inlet. Wire mesh sensors measurements were recorded at axial locations of 97.5, 112.8, and 130.8 pipe diameters from the air-water inlet, which included axial locations both upstream and downstream of the 90° bend. Deionised water and compressed air were used as the working fluids, with the bubbly flow regime achieved at superficial liquid velocities ranging from 3.50 m/s to 5.42 m/s and superficial gas velocities, referenced at atmospheric conditions, ranging from 0.10 to 1.25 m/s. The effects of the 90° bend, as well as superficial gas and liquid velocities, on the void fraction distribution were parametrically investigated. Extensive measurements of the area-averaged, time-averaged, and bulk-averaged void fraction are reported for a total of 27 individual test cases. Radial profiles of the time-averaged void fraction are presented for all test cases along both vertical and horizontal axes. Results demonstrated the effects of superficial liquid and gas velocities on phase distribution before and after the bend. Statistical techniques were applied to discretize a transitional bubbly-slug flow pattern into constituent small bubble and large bubble flow patterns.