Physical processes of heat transfer after the boiling crisis (Post-CHF) at high pressure parameters


In innovative nuclear systems, supercritical fluids (water, CO2) are increasingly used. For the safety assessment of thermohydraulic systems with supercritical fluids, detailed knowledge of the heat transfer in a wide pressure range (supercritical and subcritical) is indispensable. A particular focus lies on the study of boiling crises, which lead to drastic deterioration of heat transfer and therefore to an immediate and significant increase of the wall temperature. Since this can lead to damage of the flow tubes, knowledge of their occurrence is of high relevance for the safe design of power plants. In the pressure range up to the reduced pressure value of pr = 0.7, the occurrence of boiling crises and the subsequent heat transfer have already been intensively investigated. In the high pressure range, however, there are only a few models for the critical heat flux (CHF).


The scientific goal of the project is the investigation and a better understanding of the CHF and post-CHF heat transfer in the high pressure range.

In collaboration with multiple university partners, experimental data with Freon, CO2 and water will be generated and integrated into a database. With the help of this database and an improved understanding of the mechanistic processes, existing models for the prediction of CHF and post-CHF heat transfer will be evaluated and extended by new models. Numerical simulations using CFD codes will contribute to a better understanding of the phenomena and support the experimental work. The development of fluid-to-fluid scaling models allows the transfer of the experimental data of the three different fluids. The implementation of the newly developed models and the validation against experimental data will be supported by GRS and is expected to increase the validity of the STH program ATHLET for innovative nuclear systems with supercritical fluids.

For more information see here


Federal Ministry of Education and Research



Jan Oettig, Laura Licht