Numerical study of the turbulent flow and vortex structures in a new lattice

Quasi-periodic large scale vortex structures are the major reason for the enhancing of transverse fluid mixing and heat transfer in rod bundles. In this work, the turbulent flow, heat transfer and vortex structures in a new lattice with enhanced heat transfer and fluid mixing are investigated. The numerical simulations are executed by Unsteady Reynolds-Averaged Navier-Stokes (URANS) method with the Reynolds Stress Model (RSM). It is revealed that the transverse fluid mixing and the vortex structures are enhanced as the local wall thickness increases, whereas the Nusselt number shows a peak value. The streamwise velocity in gap regions and the global frictional resistance coefficient will monotonically decrease as the local wall thickness increases. This new lattice is superior to the traditional rod bundles and an optimized value of the local wall thickness with ΔR/δ = 20% is recommended.