Study of strongly heated upward turbulent gas flow - 14089

In vertical upward heated flow which is reactor core typical flow configuration, turbulent heat transfer can be deteriorated if the flow is going from forced convection to mixed convection regime which is a phenomenon that can happen during an accident phase. It has been found that Gas-cooled Fast Reactor (GFR) might operate in the deteriorated turbulent heat transfer (DTHT) regime during an accident phase. Several previous works have been done to investigate and describe the phenomenon that occurs in mixed convection regime. This paper will first discuss about the heat transfer regimes that exist and their effect on turbulent heat transfer. Some of the natural circulation data from an experiment will be compared to the numerical results. The problem domain for the CFD analysis is made to represent the experiment of the natural circulation which is the condition that of the reactor core during accidents. The v²-f model is chosen as the turbulence model for this case because it has been proven to perform well for mixed convection case. Through a numerical analysis, the phenomena can be reasonably depicted. (authors)