Upward air-water bubbly flow characteristics in a vertical square duct

• Published in: Journal of nuclear science and technology Vol. 51; no. 3; pp. 267 - 281
• Main Authors: Sun, Haomin, Kunugi, Tomoaki, Shen, Xiuzhong, Wu, Dazhuan, Nakamura, Hideo
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 04-03-2014
• Subjects: bubble diameter; hot-film anemometry; large square duct; liquid velocity; measurement; optical probe; two-phase flow; void fraction
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/00223131.2014.863718

In nuclear engineering fields, gas-liquid bubbly flows exist in channels with various shape and size cross-sections. Although many experiments have been carried out especially in circular pipes, those in a noncircular duct are very limited. To contribute to the development of gas-liquid bubbly flow model for a noncircular duct, detail measurements for the air-water bubbly flow in a square duct (side length: 0.136 m) were carried out by an X-type hot-film anemometry and a multi-sensor optical probe. Local flow parameters of the void fraction, bubble diameter, bubble frequency, axial liquid velocity and turbulent kinetic energy were measured in 11 two-phase flow conditions. These flow conditions covered bubbly flow with the area-averaged void fraction ranging from 0.069 to 0.172. A pronounced corner peak of the void fraction was observed in a quarter square area of a measuring cross-section. Due to a high bubble concentration in the corner, the maximum values of both axial liquid velocity and turbulent kinetic energy intensity were located in the corner region. It was pointed out that an effect of the corner on accumulating bubble in the corner region changed the distributions of axial liquid velocity and turbulent kinetic energy intensity significantly.