Prediction of void fraction for PWR and BWR conditions with the sub-channel code F-COBRA-TF

The present paper discusses a comprehensive extension of the already substantial validation of the sub-channel code F-COBRA-TF with respect to void fraction prediction. In contrast to many established sub-channel codes, F-COBRA-TF allows a two-fluid/three-field representation of two-phase flow. Due to this modeling F-COBRA-TF, does not need to apply classical void correlations predicting void fraction according to quality. Instead, void fraction is a direct result of the basic transport equations for mass, momentum, and energy by using flow regime dependent interfacial friction correlations.Experimental data from open literature (tube boiling measurements in the sub-cooled region), from the OECD/NRC PSBT benchmark, and from in-house tests in AREVA's KATHY loop were used for validating F-COBRA-TF. In summary, it can be stated that all measurements could be recalculated with F-COBRA-TF with overall good agreement. Especially having in mind that no special code tuning concerning certain flow geometries or ranges of flow conditions had been performed, the obtained results look very convincing. Both, BWR and PWR conditions were simulated with exactly the same model set.

► This work presents an extension of the already substantial validation of AREVA's sub-channel code F-COBRA-TF.
► Experimental data from open literature, from the OECD/NRC PSBT benchmark, and from in-house tests in AREVA's KAHTY loop were recalculated.
► A detailed measurement uncertainty analysis regarding the OECD/NRC PSBT benchmark was performed.
► An overall good agreement was achieved without any special code tuning concerning different flow geometries or ranges of boundary conditions.