Investigation on heat split in a vertical 3 × 3 dual-cooled annular rod bundle

Abstract

Single-phase heat transfer experiment in a 3 × 3 dual-cooled annular rod bundle was performed to study the heat split behavior and evaluate the applicability of heat transfer correlations to annular fuel. The parametric effects on heat split were investigated. The results showed that the heat split obviously increased with the flow split, and slightly increased with increasing inlet temperature and heating power. The thermal-conduction resistances of gaps played a leading role in heat split mechanism and the convective heat transfer was the secondary factor affecting the heat split. The applicability of heat transfer correlations was assessed by the experimental data. The predictive performance was significantly improved when replacing the hydraulic equivalent diameter by the heated equivalent diameter in the Nusselt number calculation. The DB and El-Genk correlations had the best predictive effect on the heat transfer in the external channel, with the MAE of 0.082 and 0.094 respectively.