The mechanism of bubbly to slug flow regime transition in air-water two phase flow: A new transition criterion

• Published in: International journal of heat and mass transfer 2017-05, Vol.108, p.1579-1590
• Main Authors: Zhang, Muhao, Pan, Liang-ming, Ju, Peng, Yang, Xiaohong, Ishii, Mamoru
• Format: Article
• Language: English
• Subjects: Bubbly flow; Bubbly velocity; Flow regime; Theoretical transition criteria; Velocity ratio
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2017.01.007

•Air-water two-phase upward flow experiments are conducted in 25.4mm round tube.•It was found that the velocity ratio has strong connection with flow regime transition.•Theoretical model is built to verify such connection.•New transition criterion is presented based on such phenomenon. Air-water two-phase upward flow experiments are conducted in a tubular test section with the inner diameter of 25.4mm in order to investigate the transition mechanism of bubbly flow to slug flow. Flow regime identification is carried out by using ReliefF-FCM clustering algorithm, i.e., a new objective flow regime identification method. It is found that the velocity ratio decreases with the increase of superficial gas velocity in bubbly flow at the constant liquid superficial velocity. And the velocity ratio always reaches its minimum during the flow regime transition. The present research finds that the changes of bubble size and shape may result in the decrease of velocity ratio in bubbly flow. From this point of view, a new mechanism for bubbly to slug flow regime transition has been proposed. A transition criterion based on the mechanism is also built. The comparison of the transition criterion with the experimental results at different flow conditions is carried out. Although the transition criterion is empirically modified based on the present experimental data, it shows the reasonable agreements.