Assessment of Nucleation Boiling Models and Improvement by the Chen Correlation for Two-fluid Model CFD

Abstract

• We assess a total of 42 combinations of nucleation boiling models using 3-D CFD code ANSYS CFX. • No specific departure frequency model or departure diameter model could consistently perform the best. • We propose an approach to determine the departure frequency directly using the Chen correlation. • Using the Chen correlation in place of the departure frequency model can improve the void fraction prediction. • The Chen correlation is shown to be a reliable approach for determining the void fraction in realistic application before more accurate mechanistic models are available. Accurate prediction of vapor generation due to wall nucleation boiling is important in boiling heat transfer systems such as nuclear reactors. In current studies, simulations were performed using the commercial three-dimensional (3-D) Computational Fluid Dynamics (CFD) code ANSYS CFX to compare the predictive capabilities of different bubble departure diameter models and departure frequency models for subcooled boiling flow. Six diameter models and seven frequency models, a total of 42 model combinations, were compared with data from four experimental conditions. The simulation results showed a large variation between different model combinations. There was no specific frequency model or diameter model which could consistently perform the best. Also, most of the results showed smaller void fraction than the experimental data near the heated wall as well as the bulk region. To improve, the Chen correlation was used in place of the bubble departure frequency model. The results showed void fraction predictions closer to experimental data.