One-dimensional interfacial area transport of vertical upward bubbly flow in narrow rectangular channel

Highlights: ► Experiments are performed in vertical narrow rectangular channel. ► Local data of IAC and others are measured by imaging processing technique. ► Developing two-phase flow is characterized by great changes of local parameters. ► Existing frictional multiplier correlations and drift-flux models are verified. ► Existing IAC model is modified to predict the IAC and the Sauter mean diameter. - Abstract: The design and safety analysis for miniature heat exchangers, the cooling system of high performance microelectronics, research nuclear reactors, fusion reactors and the cooling system of the spallation neutron source targets requires the knowledge of the gas–liquid two-phase flow in a narrow rectangular channel. In this study, flow measurements of vertical upward air–water flows in a narrow rectangular channel with the gap of 0.993 mm and the width of 40.0 mm were performed at seven axial locations by using the imaging processing technique. The local frictional pressure loss gradients were also measured by a differential pressure cell. In the experiment, the superficial liquid velocity and the void fraction ranged from 0.214 m/s to 2.08 m/s and from 3.92% to 42.6%, respectively. The developing two-phase flow was characterized by the significant axial changes of the local flow parameters due to the bubble coalescence and breakup in the tested flow conditions. The existing two-phase frictional multiplier correlations such as and were verified to give a good prediction for the measured two-phase frictional multiplier. The predictions of the drift-flux model with the rectangular channel distribution parameter correlation of and several existing drift velocity correlations of and agreed well with the measured void fractions and gas velocities. The interfacial area concentration (IAC) model of was modified by taking the channel width as the system length scale and the modified IAC model could predict the IAC and Sauter mean diameter acceptably.