Numerical Analysis of Critical Heat Flux Phenomenon in a Nuclear Power Plant Core Channel in the Presence of Mixing Vanes

The necessity and importance of a high heat removal potential in various areas particularly in nuclear applications are in a direct relationship with the excessively applied heat flux level. One way to increase the heat transfer performance and subsequently enhance the threshold of the critical heat flux is to employ spacer grids accompanied by mixing vanes. In this study, the effect of the spacers with mixing vanes on the critical heat flux characteristics in the dryout condition has been numerically investigated employing the benefits of the Eulerian-Eulerian framework. In the current research, several vane angles, including vane with 0, 15 and 25 degrees in comparison with the effect of the bare spacer without any mixing vanes on the flow characteristics were examined. It was shown that the existence of the spacer alone, delays the temperature jump under critical heat flux conditions. It was also concluded that increasing the angle of the mixing vanes, further improves the heat transfer performance of the system by postponing the sudden temperature jump occurring in the channel; however, the presence of the spacers and vanes in the flow field imposes an increase of the pressure drop due to the constriction on the coolant flow area.