CFD Modeling of High-Pressure Subcooled Flow Boiling in Vertical Pipes

Subcooled flow boiling is an attractive phenomenon to enhance heat transfer from fuel assemblies in nuclear power reactors. Eulerian-Eulerian Two Fluid (EETF) model in conjunction with Wall Heat Flux Partitioning (WHFP) model is found suitable to simulate the physics of subcooled flow boiling. However, these models depend on a large number of closure relations. For high-pressure applications, development and testing of such correlations are still underway, owing to the complexity of various multi-scale processes involved in this mechanism of heat transfer. The developmental nature of these models makes it an attractive option to use open-source codes like OpenFOAM due to the flexibility of incorporating new models and testing them. In the current study, the EETF and WHFP models available in OpenFOAM are evaluated against the extensive experimental data set (pressure: 15–150 bar, mass flux: 400–2000 kg/m2/s, heat flux: 0.38–2 MW/m2) from literature using generally recommended closure relations. It is observed that the model predictions for the overall trends in the cross-section averaged void fraction profiles are reasonable, while some systematic deviations are discussed. This study is expected to serve as a baseline for further research in improving the high-pressure subcooled boiling models and their testing in OpenFOAM.