Effect of rectangular ribs on the thermal–mechanical behavior of supercritical CO ₂ in regenerative cooling channel

Supercritical carbon dioxide (SCO ₂) has broad application prospects in SCRamjet cooling and thermoelectric conversion systems. This study provides a comprehensive investigation of the thermal–mechanical coupling mechanisms of rib-enhanced heat transfer in regenerative cooling channel. The results show that ribs regulate the spatial distribution of buoyancy and suppress the flow acceleration effect. The upstream side of the rib shows markedly higher local heat flux and thermal stress, which intensify from the rib root toward the rib tip. Thermal stress is identified as the main component of the equivalent stress. Compared with the smooth channel, the ribbed channel reduces the peak equivalent stress by up to 16.9%, while slightly increasing the average stress. Rib height primarily influences the range and intensity of shear layer. Increasing rib height enhances heat transfer but also intensifies stress concentration, shifting the maximum cross-sectional stress from the top wall to the rib. Meanwhile, rib pitch mainly affects the frequency of flow disturbances, and larger pitch results in a significant increase in peak stress. Considering the combined thermal–hydraulic–mechanical effects, the reasonable rib parameters are identified as h= 0.3–0.35 mm and p= 9–12 mm. The results provide valuable guidance for heat transfer enhancement and structural optimization in regenerative cooling channel utilizing SCO ₂.