The Institute of Safety Research at the Forschungszentrum Rossendorf (FZR) focuses on safety assessments in nuclear plant and the chemical process industry. In this field, most of the passive safety components rely on natural convection to remove heat, and often involve large heat fluxes and boiling flows. We chose CFX-4 to help us in studying these flows because of its open interface that allows us easily to add our own models when required.

Before deciding on CFX-4, we undertook a number of validation projects. An example was the simulation of a scaled emergency condenser (NOKO) constructed in the laboratory of Forschungszentrum Jülich. We modelled the heat transfer from heated tubes in the primary circuit to the pool in the secondary circuit, accounting for the transient and laminar flow in the pool. CFX-4's calculation of the temperature stratification and the development of the plume were in good agreement with the experimental results.