Numerical investigation on heat transfer characteristics of S−CO₂ in equal-section inclined tubes

Abstract

The heat transfer characteristics of $\mathrm{S}\text{-}\mathrm{C}{\mathrm{O}}_2$ are investigated at different inclination angles ($\mathrm{\alpha }=$15°, 30°, 45°, 60°, and 90°) and pressures (p = 8, 9, and 10 $\mathrm{MPa}$). It is found that the $\mathit{SST} k-\omega$ model can more accurately predict the heat transfer of $\mathrm{S}\text{-}\mathrm{C}{\mathrm{O}}_2$ in horizontal tubes. When $q_w/G$ is large, the top surface temperature will rise sharply. It is due to the gas-like film weakens the thermal absorption efficiency and impedes the fluid in the core region from taking up thermal in the near-wall area, resulting in severe heat transfer deterioration. The buoyancy criterion ${Gr}_q^{*}/{Gr}_{\mathit{qth}}$ shows that the buoyancy and the gas-like film thickness decrease as the inclination angle increases, which effectively improves the heat transfer performance in the top area and weakens the heat transfer deterioration phenomenon. Affected by the critical temperature and the peak of specific heat, the bulk temperature also increases when the pressure increases. In the region of $\theta$ = 45° to 315°, raising the pressure is accompanied by higher circumferential wall temperature, whereas in contrast to the change in ${Nu}_w.$

Keywords:

• S$-{\mathrm{CO}}_2$
• turbulence model
• gas-like film
• buoyancy
• inclination angle

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Guizhou Science and Technology Plan Project ([2020]1Y237), National Natural Science Foundation of China (52066004) and Innovation team of Guizhou Province (CXTD2022-009).