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To effectively alleviate the heat transfer deterioration (HTD) phenomenon of supercritical CO2 flow in a vertical circular tube, this paper proposes multiple truncated ribs from a whole O-ring rib but distributed in helical-like distribution. The fluid hydraulics and thermal performance with a verified standard k–ω mode are numerically explored. The effects of the height, the distance, and the number of truncated ribs on flow characteristics, and heat transfer are observed and analyzed in detail. Results show that the heat transfer coefficient increases significantly with increasing rib height, and as the pitch decreases the fluid recirculation area behind each rib decreases, resulting in stronger mixing of swirling flow, which enhances turbulent kinetic energy in the downstream and weakens the buoyancy force, thus mitigating heat transfer deterioration. This study suggests that introducing multiple truncated ribs distributed along helices into circular vertical tubes can be a beneficial way to alleviate heat transfer deterioration and to enhance heat transfer of supercritical CO2 flow.

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According to the particular aerodynamic heating loads which hypersonic aerospace aircrafts suffered from in-service environment, a lightweight integrated thermal protection system (ITPS) named pyramidal core sandwich panel is designed. This is considered not only as an insulation structure but also a load-bearing structure. Compared to traditional thermal protection systems (TPSs), the sandwich panel has simultaneous lightweight, load-bearing, and excellent thermal protection property. The finite-element heat transfer analysis for the pyramidal core sandwich structure is performed, and the distributions of temperature in the structure are presented. Then sequential coupling method is adopted to analyze the thermomechanical performance of the structure and presentations of field of stress and displacement under aerodynamic and thermal load are provided. A comparison between corrugated-core sandwich panels and pyramidal core sandwich panels from the perspectives of heat insulation, strength, and mass is carried out. The results indicate that the particular performance of pyramidal-core structure is superior to that of corrugated-core structure.