Experimental and numerical investigation of turbulent liquid metal heat transfer along a heated rod in annular cavity

The turbulent heat transfer from a heated rod concentrically placed in annular cavity towards the liquid metal represents a crucial element for the design of a fuel assembly of advanced liquid metal cooled nuclear systems. Therein, this configuration represents the most idealized simple geometry tractable by numerical means. Hence the single pin experiment acts in the framework of the EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in Accelerator Driven System (EUROTRANS) as the validation case for several thermal-hydraulic fuel assembly experiments aimed at the understanding of the turbulent momentum and heat transport of heavy liquid metal (HLM) flows at reactor conditions. The single experiment operated in Pb45Bi55 of the THESYS loop of KALLA covers regarding the Prandtl number, the power density and the pin dimensions the entire range of flow parameters potentially occurring in fuel assemblies of an PDS-XADS (Preliminary Design Studies of an eXperimental Accelerator-Driven System) or of a lead cooled fast reactor (LFR). This study focuses on a complementary experimental and numerical study of the turbulent heat transfer from the heated fuel pin simulated to liquid metal at forced convective flow conditions, since they represent the preferential nominal operation mode of the reactor. Within the experiment velocities and temperatures are recorded around of the fuel pin simulator. The rod is aligned within the gravity field in the loop and it is centred by means of three equidistant placed spacers along its axis. The complementary conducted numerical studies aim at interpreting the experimental results as well as the validation of used turbulent models. The paper presents also the effect of spacer on the flow field, and consecutive on the heat transfer from the heated rod. Regarding the turbulent forced convective flow an acceptable agreement between the numerical and experimental data is obtained both for temperature and velocity field. The observed discrepancies can be attributed to imperfections of the experimental set-up or the neglecting of internals by the numerical simulation. (author)