Experimental study of interfacial area transport in air–water two phase flow in a scaled 8×8 BWR rod bundle

► Facility scaled from ‘typical’ BWR fuel bundle. ► New data for local flow quantities in an 8×8 rod bundle. ► Data includes axial development of flow parameters. ► Data shows interfacial area concentration higher than in pipes and strong effect of length scales. ► Spacer grid effects require further study. In order to accurately predict nuclear reactor behavior, the ability to predict the transfer of mass, momentum and energy between the phases in two-phase flows, whether in the Reactor Pressure Vessel (RPV) or steam generator, is essential. A significant component of this prediction is the area available for transfer per unit volume, called the interfacial area concentration. Current thermal-hydraulic system analysis code predictions use empirical models to predict the interfacial area concentration; however accuracy and reliability can be improved through the use of an Interfacial Area Transport Equation (IATE). The IATE requires rigorously developed models for sources and sinks due to bubble interactions or phase change and an extensive database to validate those models. To provide this database, experiments using electrical conductivity probes to measure the interfacial area concentration at several axial positions have been performed in an 8×8 rod bundle which was carefully scaled from an actual BWR rod bundle.