Numerical investigation on flow and thermal performance of supercritical CO2 in a horizontal ribbed tube

The numerical simulation is performed to investigate the thermal performance of supercritical carbon dioxide (sCO2) in horizontal ribbed tubes at mass flux ranging from 200 kg/(m2·s) to 400 kg/(m2·s), heat flux, 20 kW/m2 to 30 kW/m2, pressure 8–9 MPa and inlet temperature 290–310 K. Three types of ribs were selected to investigate the effects of rib geometry, buoyancy and rib parameters on the thermal-hydraulic performance. The results indicated that the triangular ribbed tube (TRT) could significantly improve the heat transfer coefficient (HTC) and reduce the wall temperature. Nevertheless, circular ribbed tubes have the best performance from the performance evaluation criteria (PEC) viewpoint. Moreover, the rib configuration promotes the transition of the flow field from “flattened shape” to “U-shaped”, which improves the heat transfer. Finally, small rib size and medium pitch can further enhance supercritical CO2 turbulent heat transfer. [Display omitted] •Supercritical CO2 heat transfer in horizontal ribbed tubes was numerically studied.•The thermal performance of different geometries of ribbed tubes was compared.•Triangular ribbed tubes have higher heat transfer coefficient than other tubes.•Rib configuration can improve heat transfer and mitigate buoyancy effect.