Numerical investigations of flow and heat transfer characteristics of a regenerative cooling channel using supercritical CO2 with different cross-section shapes

Because of the excellent heat and mass transfer ability, this study employed supercritical CO₂ as a supplementary coolant to kerosene for regenerative cooling at extremely high Mach numbers (Ma≥8). The study investigated the effects of cross-section shapes, flow patterns, and wall materials on the flow structures and heat transfer performance associated with entropy generation analysis. From the results, the triangular channel has highest heat transfer coefficient, while the square channel has the lowest the friction factor. Considering both he first and second law of thermodynamics, it is concluded that the channel with the triangular cross-section provides the best thermal performance. The channel with the circular cross-section shows better performance at the channel outlet, primarily attributed to its larger turbulent kinetic energy and thinner momentum and thermal boundary layers. The opposite flow pattern of adjacent channels can not only reduce the maximum wall temperature by at least 10 %, but also improve the wall temperature uniformity and promote heat transfer between adjacent channels. Compared with high-temperature alloys, using Cu as channel materials can greatly increase the heat transfer performance by 16.7 %.