Single-phase flow in helical cruciform fuel assembly with conjugate heat transfer

Abstract

The helical cruciform fuel (HCF) is promising to improve the power density and safety margin of reactors core by its advantages in the heat transfer area-to-volume ratio and continual inter-channel mixing. In this work, the turbulent mixing and heat transfer characteristics of HCF assembly for pressurized water reactor was studied. A novel mesh generation strategy was used to discretize the computational domain of helical fuel assembly with hexahedron meshes. The velocity field, inter-channel cross flow intensity, heat transfer coefficient and the circumferential distribution of wall temperature and heat flux were obtained based on the CFD simulation. The cross flow intensity in the side gaps was greater than that in the internal gaps, which were all significant larger than that of traditional circular rod bundle. The heat transfer coefficient of helical fuel assembly was slightly larger than traditional circular rod bundle under same mass flow rate condition. The helical fuel assembly can offer 38.4% more heat transfer area. The peak-to-average heat flux in the circumferential direction was larger than 2.0, which may result in early boiling crisis.