CFD thermo-hydraulic analysis of the CIRCE fuel bundle

The present paper focuses on the CFD post-test analysis of the experimental campaign performed in the frame of the Integral Circulation Experiment (ICE) configuration of the CIRCulation Eutectic (CIRCE) facility located at the ENEA Brasimone Research Centre (Italy). Experiments were carried out aiming to fully investigate the heat transfer phenomena in grid spaced fuel pin bundles providing experimental data in support of European Lead cooled Fast Reactor development. The fuel pin bundle simulator is composed by 37 electrical pins arranged in a hexagonal lattice cooled by lead bismuth eutectic (LBE). The thermal power is about 1 MW with a uniform linear power up to 25 kW/m. The CFD geometrical domain reproduces an angle of 60° of the FPS and lateral rotational periodic boundary conditions are adopted. High-resolution Reynolds Average Navier Stokes (RANS) simulations were carried out adopting the Ansys CFX commercial code with enhanced wall and the SST k-ω turbulence model. Due to the relatively low molecular Prandtl number of heavy liquid metal, a sensitivity study on the Prt was performed. Numerical results for the pin wall temperature and the coolant temperature in the central subchannel were compared with the experimental data. The Nusselt number was derived for each simulation for the central subchannel and compared both with the experimental results and Nusselt numbers obtained from convective heat transfer correlations available in literature for Heavy Liquid Metals. The good agreement found justifies the use of high quality RANS with a modified turbulent Prandtl number in the investigation of heat transfer in fuel pin bundle at high Re.