20.500.12556/RUL-182650 On the limitations of CFD modelling of flow boiling at high flow velocities and high heat fluxes The ability of computational fluid dynamics (CFD) models to predict flow boiling at high heat flux and high flow velocity conditions has been investigated. High heat fluxes of about 10 MW/m$^2$ and high flow velocities of about 10 m/s typically appear in water cooling channels of divertor target elements in fusion reactors. In particular, the heat flux partitioning model used in the two-fluid CFD formulation was studied. CFD simulations of flow boiling in realistic divertor target cooling channels were performed and compared with conservative single-phase simulations. The predictive capability of CFD models for boiling was evaluated using experimental data, covering a wide range of flow velocities and heat fluxes. Existing CFD models correctly predicted void fraction and wall temperature at low flow velocities, but produced erroneous results at higher velocities (above 3 m/s) resulting in unphysical wall temperature overestimation. The study identified the wall heat flux partitioning model as the main contributor to the mispredictions. By analysing the effects of key boiling parameters, the limitations of the conventional RPI (Rensselaer Polytechnic Institute) model have been identified and a targeted modification is proposed to improve its performance under divertor-relevant conditions. The proposed modification serves as a demonstrative improvement and a basis for future mechanistic model development. The simulations and model analyses are performed within the framework of the ANSYS CFX code and the results are compared with flow boiling experiments in uniformly and top-heated flow channels. flow boiling heat flux partitioning high flow velocities wall temperature CFD void fraction razdelitev toplotnega toka vrelišče toka temperatura stene true false true Angleški jezik Slovenski jezik Članek v reviji 2026-05-20 09:43:54 2026-05-20 09:44:02 2026-05-21 04:57:12 0000-00-00 00:00:00 2026 0 0 21 str. Vol. 245, art. 127707 Jan. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 536 1879-2189 10.1016/j.ijheatmasstransfer.2025.127707 246364419 1-s2.0-S0017931025010440-main.pdf 1-s2.0-S0017931025010440-main.pdf 1 3EF042343ACC09EBFECF87D216F9E777 b4553d91007a9c1d18ee98e973b63a9ed13f4808c73e454685bda0a0773126b8 c4ee4943-541f-11f1-b0ab-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=234101 https://www.sciencedirect.com/science/article/pii/S0017931025010440 1 5ace4982-541f-11f1-b0ab-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=234100 Fakulteta za matematiko in fiziko 0 0 0