CFD Modelling of subcooled boiling

Heat transfer and boiling are key phenomena in critical equipment used in power generation facilities. Modelling of boiling in 1D thermal hydraulic codes was state of the art right from the beginning of their development, whereas boiling models in 3D thermal hydraulic codes are far from reaching this level of maturity. In this paper, the boiling model implemented in the CFD code CFX-4 was applied, to analyse several boiling experiments, the results of which are published in literature. The validity of the implemented correlations is examined. In many cases the model yields a good agreement with experiments. However, especially in the low pressure region, the steam volume fraction is under predicted. The models implemented in CFX are critically reviewed and compared to alternative solutions. The sensitivity of the calculated results on different parameters are compared. The need for improvements in the model and for further experiments are derived. Main attention should be focused on measuring and modelling of the correct size of the steam bubbles generated.