Effects of wire-spacer shape in LMR on thermal–hydraulic performance

In this work, analyses of three-dimensional flow and convective heat transfer in wire-wrapped fuel assemblies with different shaped wire-spacers have been carried out using Reynolds-averaged Navier–Stokes equations with shear stress transport turbulence model. Three cross-sectional shapes of wire-spacer, circle, hexagon and rhombus have been tested. All the assemblies have been analyzed for single pitch of wire-spacer with periodic boundary conditions applied at inlet and outlet of the calculation domain. It is found that the assemblies exhibit the directional periodicity in radial gradients between the adjacent subchannels due to presence of wire-spacer. The overall pressure drop is highest in case of rhombus shaped wire-spacer assembly followed by hexagonal shaped. Although circular shaped wire-spacer gives lowest peak temperature as well as lowest overall temperature difference in the assembly, the rhombus shaped wire-spacer assembly gives highest Nusselt number on fuel rod surface.