Lesson learned from the adoption of numerical techniques in the analysis of nuclear reactor thermal-hydraulic phenomena

The paper summarises the results of the application of numerical techniques in gaining insight into physical phenomena of interest for nuclear reactor thermal-hydraulics. Emphasis is given to the capabilities that present computational resources offer for achieving a detailed picture of complex phenomena, requiring the adoption of up-to-date means for increasing understanding.The addressed material is related to flow stability in single-phase natural circulation and heated channels with boiling and supercritical fluids, transpiration effects in condensation and evaporation and deterioration of heat transfer to supercritical fluids. Results of both one-dimensional analysis tools and computational fluid-dynamic codes are considered.Conclusions are drawn about the role of numerical tools in stimulating understanding and promoting further research.