Nanoengineering-Enhanced Capillary Cooling Achieves Sustained Thermal Protection for Ultra-High Heat Flux and Temperature.

Extreme thermal conditions with heat flux densities exceeding 1 MW m or temperatures reaching up to 1000 °C are prevalent in various situations. However, thermal protection ability depends on specialized materials or is currently limited with existing cooling schemes. Herein, an innovative cooling scheme that relies on evaporation-driven capillary flow, enhanced by nanoengineering-designed porous structures with common materials, is proposed. Experimentally-obtained capillary flow cooling curve identifies critical heat flux corresponding to evaporation-driven flow stage, where coolants cool the surface and subsequent vapor impedes heat transfer from thermal boundaries. Nanoengineering provides opportunities for enhanced capillary flow, which proves to endow bronze, TC4 (titanium alloy, Ti-6Al-4V), and AlO with thermal protection ability 50-180% higher than that without nanoengineering-designed. The authors' scheme achieves critical heat flux up to 2.0-3.1 MW m and performs thermal dissipation capacity almost twice higher than inherent latent heat of coolant. Further, in a supersonic wind tunnel with total temperature reaching up to 1792 K, this scheme effectively protects surfaces by cooling them to surface temperatures below 500 K. Nanoengineering-enhanced capillary cooling gives access to the application of common materials for high-temperature and high-heat-flux environments and paves the way for development of lightweight, long-lasting, and large-scale solutions for thermal protection.