Interfacial area transport of vertical upward air–water two-phase flow in an annulus channel

An experimental study on the interfacial area transport (IAT) of vertical, upward, air–water two-phase flows in an annulus channel has been conducted. The inner and outer diameters of the annular channel were 19.1 mm and 38.1 mm, respectively. Nineteen inlet flow conditions were selected, which cover bubbly, cap–slug, and churn–turbulent flows. The local flow parameters, such as void fraction, interfacial area concentration (IAC), and bubble interface velocity, were measured at nine radial positions for the three axial locations (z/DH = 52, 149 and 230). The radial and axial evolutions of local flow structure were interpreted in terms of bubble coalescence and breakup. The measured data can be used for the development of the bubble coalescence/breakup models for the IAT model and some closure models for computational fluid dynamics.