Background: Liquid metal has been proposed as the coolant of the fourth generation nuclear reactor and the accelerator driven sub-critical system. Due to its low molecular Prandtl number (Pr)

liquid metal differs from other coolants like water or gas in heat transfer. Purpose: This study aims to investigate the character of heat transfer of liquid metal inside the reactor core. Methods: Speziale-Sarkar-Gatski (SSG) Reynolds stress model was applied to the Computational Fluid Dynamics (CFD) prediction of liquid metal flow and heat transfer inside the sub-channels of the reactor core. Effect of different dimensionless parameters

e.g. Reynolds number (Re)

Pr

Grashof number (Gr) and pitch-to-diameter ratio (P/D) on the turbulent heat transfer calculated results was investigated. Results: The dimensionless convective heat transfer coefficient (Nu)

predicted by the CFD method

agrees well with the experimental data and the empirical relations. Conclusion: Based on the analysis of various dimensionless parameters

it is found that the heat exchange performs better in triangular fuel assembly sub-channels than that in square sub-channels

under the same condition of P/D and Re. The inhomogeneous circumferential distributions of temperature and heat transfer can be effectively improved by increasing Re and P/D or choosing coolants with large Pr. When Re is larger than 10000

the buoyancy effect on liquid metal heat transfer could be ignored. Abstract