Heat transfer and deformation mechanisms of a nature-inspired transpiration cooling system for deformable aircraft

Abstract

Plants cooldown by moving water from their roots to their leaves at no energy expense, uniformly and reliably. Can engineers mimic plants to deliver intelligent cooling systems for supersonic/hypersonic flight? Evidence here suggests that such an advancement is possible. We propose a radically new transpiration cooling concept which is inspired by nature and combines supreme characteristics: the coolant flow adjusts naturally to the external heat flux environment thanks to capillary forces and the system can deform excessively if rubber-based materials are used. Experiments on exemplary nickel-based cooling systems indicate that the peak solid temperature can be maintained below 130 °C at heat loads of 270 kW/m², attributable to an excellent convective cooling efficiency of $\eta =$ 91 %. This efficiency is predicted to reduce to $\eta =$ 54 % for the case of silicon rubber, suggesting that the system could provide efficient cooling in future deformable aircraft wings, if rubber-based walls with intricate cooling channels can be manufactured. Computational Fluid Dynamics (CFD) and Finite Elements (FE) analyses also indicate that the cooling performance and structural integrity of the proposed TPS can be improved by modifying cooling channel geometry. Our study will hopefully provide a steppingstone to developing nature inspired TPS for greener aerospace vehicles.