Radial distribution and formation mechanism of the void fraction in an inclined circular tube

Void fraction radial distribution of gas-liquid two phase flow in an inclined circular tube was investigated experimentally by using an optical fiber probe, and the reason for its formation was also illustrated. Experiments were conducted in an inclined circular tube made of perspex with inner diameter of 50 mm, and inclination angles of 5°, 15° and 30°. The specific liquid velocity was 0.071~0.284 m/s and the specific gas velocity covered the range of 0~0.5 m/s. The results show that, with increase of the inclined angle, the radial distribution of void fraction gradually shifts from the 'core peak' and 'wall peak' to the single 'wall peak' distribution. The analysis of the buoyancy component in radius and lateral lift forces as well as wall force acting on bubbles shows that the combined effects of these forces lead to the bubbles gathering around the radial position between 15 mm and 22 mm, resulting in the 'wall peak' distribution of the void fraction.