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

AbstractThe heat transfer characteristics of S-CO2 are investigated at different inclination angles (α=15°, 30°, 45°, 60°, and 90°) and pressures (p = 8, 9, and 10 MPa). It is found that the SST k−ω model can more accurately predict the heat transfer of S-CO2 in horizontal tubes. When qw/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 Grq*/Grqth 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 θ = 45° to 315°, raising the pressure is accompanied by higher circumferential wall temperature, whereas in contrast to the change in Nuw.Keywords: S−CO2turbulence modelgas-like filmbuoyancyinclination angle Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis 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).