Interfacial area transport of subcooled water–steam condensing bubbly flow in vertical pipe

The interfacial area transport of a subcooled water–steam condensing bubbly flow in a vertical pipe with inner diameter of 29 mm was investigated. Three fundamental parameters, the void fraction, interfacial area concentration (IAC) and bubble Sauter mean diameter, were experimentally obtained using a double-sensor conductivity probe technique. The radial and axial developments of local flow structure were interpreted based on the phase change and bubble interaction mechanisms, such as the bubble condensation, coalescence and break-up. Based on the experimental data sets, a critical Weber number range to identify the core peak was developed for one-component steam–water systems. Furthermore, the theoretical modeling of the one-dimensional interfacial area transport equation (IATE), including the condensation sink term, was discussed and compared with the experimental data. The axial distributions of area-averaged IAC profiles were best computed via the use of the IATE. The evaluation results showed that the interfacial area transport was dominated by the heat-mass transfer mechanism causing bubbles condensation in the flow.