Numerical investigation on flow and heat transfer of petal-shaped fuel bundle in hexagonal arrangement under natural circulation conditions

Helical petal-shaped fuel rods have the characteristics of increased heat transfer area and self-supporting positioning, which makes them have great potential for application in small modular reactors. By employing the multi-scale coupled numerical model, the flow and heat transfer characteristics of the petal-shaped bundle in hexagonal arrangement were obtained under natural circulation conditions. The results indicated that the spatial structure of flow channel exhibited a centrally symmetric distribution. Consistent flow and heat transfer behaviors were obtained at symmetric positions. Additionally, fluid viscosity exerted the most significant influence on flow resistance coefficient. Meanwhile, vortices that develop in the opposite direction resulted in flow losses, which induced variations in the resistance coefficient along the channel. Finally, the applicability of existing flow and heat transfer correlations was evaluated under natural circulation conditions. This study has provided significant theoretical guidance for engineering application of the petal-shaped fuel rods.