Fig. 1. Schematic diagram of the geometric model.

Fig. 2. Verification for grid independence.

Fig. 3. Thermophysical properties of S-CO₂ under different pressures: (a) Specific heat at constant pressure c_p; (b) density ρ; (c) thermal conductivity λ; (d) viscosity μ.

Fig. 4. Comparison of wall temperature predicted by simulation against experimental data by Adebiyi and Hall^[12].

Fig. 5. Typical curves of heat transfer characteristics for S-CO₂ in horizontal tube: (a) Axial distribution of inner wall temperature and heat transfer coefficient at top generatrix and bottom generatrix; (b) circumferential distribution of vapor-like film thickness.

Fig. 6. Vector velocity distribution in the characteristic cross-sections.

Fig. 7. Temperature distribution in the characteristic cross-sections.

Fig. 8. Radial distribution of axial velocity for S-CO₂ in horizontal tube.

Fig. 9. Influences of heat flux on wall temperature and second flow intensity.

Fig. 10. Radial distribution curves of thermophyical properties in the characteristic cross-sections under different heat flux: (a) Specific heat at constant pressure c_p; (b) thermal conductivity λ; (c) axial velocity u; (d) turbulent kinetic energy k.

Fig. 11. Effects of mass flux on wall temperature and second flow intensity.

Fig. 12. Radial distribution curves of thermophyical properties in the characteristic cross-sections under different mass flux: (a) Specific heat at constant pressure c_p; (b) thermal conductivity λ; (c) axial velocity u; (d) turbulent kinetic energy k.