Fig. 1. Diagrams of fuel assembly geometry models (a) Round rod, (b) Wire-wrap, (c) Spiral two-fin rod, (d) Spiral four-fin rod

Fig. 2. Localized geometry of spiral four-fin

Fig. 3. Schematic diagram of fuel rod and subchannel numbering

Fig. 4. Computational domain mesh distribution(a) Round rod, (b) Wire-wrap, (c) Spiral two-fin rod, (d) Spiral four-fin rod

Fig. 5. The local grid distribution of the computational domain(a) Wire-wrap, (b) Spiral four-fin rod

Fig. 6. Changes of LBE properties with temperature (color online)

Fig. 7. Grid independence verification (a) The circumferential mean temperature of rod 10, (b) Local temperature distribution

Fig. 8. Comparison of simulated values with experimental results (color online) (a) z=1H/6, (b) z=11H/6, (c) z=15H/6, (d) Comparison of frictional resistance coefficients of different turbulence models

Fig. 9. Temperature distribution at z=11H/6 for different types of fuel assembly cross sections (color online)(a) Round rod, (b) Wire-wrap, (c) Spiral two-fin rod, (d) Spiral four-fin rod

Fig. 10. Heat transfer coefficients of different types of fuel assemblies

Fig. 11. Comparative analysis of local heat transfer coefficients of fuel rods at different locations (color online)

Fig. 12. Second flow intensity distribution at z=11H/6 for different types of fuel assembly cross sections (color online)(a) Round rod, (b) Wire-wrap, (c) Spiral two-fin rod, (d) Spiral four-fin rod

Fig. 13. The vector distribution of local secondary flow at z=11H/6 section and local sub-channel streamline diagram (color online)

Fig. 14. Average turbulent mixing coefficients for different types of fuel assemblies