Wall nucleation and the two-fluid model in subcooled boiling flow

In an effort to improve the prediction of two-phase flows in boiling systems, the wall nucleation phenomenon is studied in the context of the interfacial area transport equation for use with the two-fluid model. A complete review of the current modeling of the wall nucleation parameters including active nucleation site density, bubble departure diameter, and bubble departure frequency is presented along with the available database from literature. Wall nucleation experiments in an annulus channel are performed to extend the database of the bubble departure diameter and departure frequency. New models and modeling strategies are proposed for the bubble departure diameter and departure frequency. With the compiled database, the preliminary models are shown to improve the predictive capability of the wall nucleation source term in the interfacial area transport equation. The one-group area-averaged interfacial area transport equation is benchmarked in subcooled boiling flow, confirming the improvement of the new wall nucleation modeling. A low pressure and elevated pressure benchmark is discussed in detail along with a sensitivity study of important models and boundary conditions. The benchmark suggests accurate scale-up ability of the bubble departure diameter and departure frequency models to high pressure conditions.