Numerical Investigation on Flow and HeatTransfer in Sub-channel of SCWR Core with Split-vans

There are fuel assemblies in the core of Supercritical Water Reactor (SCWR). Grid spacers are the essential part of fuel assembly in SCWR Core. Grid spacers are used for keeping the fuel rods in a place and preventing the excessive vibration. However, the flow and heat transfer of the sub-channels in SCWR Core is also changed by Grid spacers. In this paper, the influence of split-vans attached to the end of grid spacers on local flow and heat transfer was investigated in the sub-channels of SCWR core with the pressure of 25MPa, mass rate of 1000kg/m²s and heat flux of 800kW/m²K. The ANSYS ICEM was employed for modeling and meshing, and the computational fluid dynamics code ANSYS CFX was adopted for numerical simulation. The characteristics of local flow and heat transfer in low enthalpy region, the great specific heat region and the high enthalpy region in sub-channels are simulated respectively. The distribution of wall temperature and the secondary flow at the cross section of downstream of split-vanes are presented in this paper. The numerical results show that, there is obviously different distribution of wall temperature and fluid flow field in three regions. The vortex generated by the split-vanes is similar in three enthalpy regions. The circumferential heterogeneities of the heat transfer in the sub-channels are evidently enhanced at the downstream of the grid spacer with split-vanes. Additionally, there is a phenomenon of heat transfer weakening at the downstream of grid spacer in the great specific heat region.