Capabilities and limits of actual CFD modelling of subcooled boiling

The verification of design improvements of a fuel assembly of a nuclear reactor core and their influence on the critical heat flux require expensive experiments. Therefore the supplementation or even the replacements of experiments by numerical analyses are of relevant interest in fuel assembly design. The CFD modeling has the potential of simulation independent on the certain geometry.
The presentation describes the actual state of CFX modeling of subcooled boiling and their possible contribution for rod bundle design. The comparative investigation of different designs is possible at least qualitatively. For more quantitatively reliable results the models have to be improved. In the presentation the demands on the accuracy of measured values are established. The usage of model fluids enables the enlargement of the investigated geometry. The most promising results are expected by tomographic methods like gamma tomography or especially by fast X-ray tomography.