Numerical study on heat transfer deterioration of supercritical-pressure carbon dioxide in a square channel

Based on the use of carbon dioxide rather than hydrocarbon fuel for aero-engine thermal protection, a numerical study was conducted to examine the deterioration of supercritical carbon dioxide heat transfer in a square cooling channel. The heat transfer characteristics along the axial and circumferential directions of the channel were studied, and the reasons for the deterioration of heat transfer were explained through the distributions of temperature, local mass flux and streamlining. The evolution process of heat transfer deterioration was further elaborated by the boundary layer analysis. The effect mechanisms of operating pressure and wall roughness on heat transfer were investigated. The critical heat fluxes for heat transfer deterioration at different operating pressures and wall roughness conditions were obtained, and the critical heat flux prediction criterion was established. The findings indicate that the features of heat transfer deterioration include the streamline distortion, local mass flux reduction, and high-temperature gas-like layer close to the channel’s top wall. The severe reduction of turbulent kinetic energy and the peak of velocity in the buffer layer are the reasons for deteriorated heat transfer. Increasing the operating pressure and increasing the wall roughness can help to suppress the deteriorated heat transfer. The established criterion (error ±15%) has a good prediction for the critical heat flux of heat transfer deterioration. © 2024 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.