Study on the Effect of Wire Winding Pitch on Gas Flow and Heat Transfer in Rod-shaped Fuel for Cooling

The wire-wrapping in gas-cooled fast reactor (GCFR) fuel rods plays a crucial role in providing positional support and enhancing heat conduction. Thermal-hydraulic analysis of fuel assemblies is an essential part of reactor performance assessment. This paper utilizes CFD (Computational Fluid Dynamics) numerical simulation software to investigate the effect of wire-wrapping pitch on gas flow and heat transfer in rod bundle channels. Based on 3D fuel assembly modeling and simulation, the following conclusions were drawn: The wire-wrapping structure significantly enhances the mixing of the flow field, which increases the coolant velocity and promotes heat removal from the fuel rods. As the wire-wrapping pitch decreases, the pressure drop across the inlet and outlet increases, the coolant velocity rises, and the cladding temperature on the fuel rods significantly decreases. In this simulation model, the highest cladding temperature at the outlet without wire winding is 1686 K, while for wire winding pitches of 100 mm and 50 mm, the temperature decreases by 52 K and 217 K, respectively.