Validation of the interfacial area transport equation coupled with void transport in condensing flows

The Interfacial Area Transport Equation (IATE) has been proposed in order to dynamically predict the evolution of interfacial structure in two-phase flows as a means to improve the phase coupling required by the two-fluid model. The dependence of the IATE on bubble interaction mechanisms such as bubble breakup and coalescence has been extensively studied. However, the IATE still requires attention in phase-change flows where the IATE is closely related to the void fraction development described by the continuity equation. The emphasis in this work is to expand the validation of the IATE in condensing flows to higher pressure and higher flow rate conditions as well as evaluating the modeling sensitivity in both the decoupled and coupled IATE. Two datasets are used for validation spanning a range of pressure, inlet subcooling and mass flux. The analysis shows that the current form of the condensation modeling results in an over-prediction of both condensation mass transfer and interfacial area concentration loss. From the decoupled IATE simulation, it is established that the boundary diameter must be used in the Nusselt number correlation in the condensation model to get good predictions of the interfacial area concentration. The coupled IATE simulation model result in better agreement in void fraction and the interfacial area concentration predictions with the proposed modifications to the condensation model. Overall, a coupled simulation is recommended for benchmarking IATE in phase change flows.