Liquid metal turbulent heat transfer in cross-flow bundles for advanced nuclear reactors

Heavy liquid metals (HLM) are attractive coolants for innovative heat exchangers in both nuclear fission and fusion applications due to their excellent thermal properties. In this paper, the ANSYS Fluent CFD code is used to characterize the fluid dynamics and heat transfer for the case of HLM (Pr=0.021) turbulent cross-flow in square and triangular rod bundles, for both loose (S=1.25) and tight (S=1.45) pitch lattice arrangements. Extensive code validation is performed for water and LM cross-flow cases, finally selecting the k-ω SST model for the purpose of the study. Steady-state simulations are performed for a test geometry with at least 10 rod ranks for uniform wall temperature and heat flux boundary conditions, in the range Pe=767÷1150. Numerical results are compared with simplified theoretical models based on experimental data, observing large underprediction (40%÷54%) and slight overprediction (12%÷31%) for the average Nusselt number in square and triangular bundles, respectively.