Modeling and numerical simulation of boiling flows: Application and dataset release of the DEBORA experiment

Computational Fluid Dynamics (CFD) is widely used in nuclear engineering for safety related studies or for new design investigations. Co-developed by EDF, CEA, ASNR and Framatome, the NEPTUNE_CFD code is specialized in nuclear thermal-hydraulic applications allowing the simulation of two-phase flows on complex geometries. Recently, a new Heat Flux Partitioning (HFP) model has been proposed by Favre et al. (2026) for a thorough description of the boiling phenomena, including, among others, the effect of wall sliding bubbles. However, an excessive increase in computation time follows the subsequent modeling improvement. This paper presents an optimization of the bubble sliding calculation returning to a reasonable computation time compatible with industrial applications. The newly developed model is then validated using NEPTUNE_CFD and compared to the DEBORA experimental data, featuring R12 coolant boiling flow within a characteristic non-dimensional scope of a Pressurized Water Reactor (PWR). The improvement in the wall temperature calculation is demonstrated by several simulations implementing the new HFP model. To support the community’s validation and benchmarking efforts, the complete DEBORA experimental dataset is made publicly available for the first time as part of this work, provided under a CC BY 4.0 license. This contribution advances both modeling capabilities and data availability, promoting transparency and reproducibility in multiphase CFD for nuclear applications. • Public release of the DEBORA experiment dataset. • Numerical simulation of the DEBORA experiment with NEPTUNE_CFD. • Optimization of a new mechanistic heat flux partitioning model. • The use of the new boiling model improves the wall temperature calculation. • The core-flow is not impacted by the wall boiling model.