Heterostructured Surface Strategy for High-flux Liquid Cooling at Extreme Conditions

Description

Cooling technologies that dissipate heat at high heat flux and function stably at extreme temperatures are fundamental to a vast number of high-power systems including aerospace, nuclear reactors, electronics, etc. Phase-change-based spray cooling, characterized by superior heat capacity, excellent uniformity, and minimal coolant consumption, has been recognized as one promising solution to meet the severe cooling demand. However, its efficacy at extreme conditions is restricted by the inevitable formation of a complete vapor cushion beneath the sprayed droplet in Leidenfrost regime. To solve this bottleneck, extensive studies have been conducted to explore the fundamental origins of Leidenfrost effect and develop surface engineering approaches to extend temperature domains for boiling heat transfer. Despite concerted efforts, current cooling strategies suffer from the mutual exclusiveness in heat flux and Leidenfrost point, which dramatically limits their practical implementations.In this proposal, we aim to decipher the complex heat transfer mechanism of hightemperature droplets and establish new design rationales for high-flux cooling at extreme conditions. Our preliminary results reveal that the porous copper cantilever can accelerate the evacuation of evaporated vapor while maintaining fast liquid wicking even at a temperature near to material melting point, decreasing the droplet lifetime by ten times. Drawing from this, we propose the design of heterostructured surfaces by integrating tilt and porous fins with directional and solid bases. On the one hand, tilt and porous fins can facilitate the downward liquid replenishment (z-axis) for massive evaporation; On the other hand, gaps between tilt fins and solid base will form separated and directional channels, reinforcing vapor evacuation along y-axis. As such, we can break the integrity of the vapor cushion, enabling mutual enhancement in heat flux and Leidenfrost point. By combining microscale visualization with theoretical analysis, we will explore how heterogeneous integrations of surface attributes affect the dynamic evolution of liquid/solid contacts, and establish critical design criteria for high-fluxcooling at extreme conditions. Further, leveraging the hydrodynamic and thermodynamic characterization of droplets, we will examine the cooling efficacy promoted by heterostructured surfaces. Finally, the practical feasibility of our design will be tested under typical water spray platforms, and alternative manufacturing techniques that are low-cost, scalable, and deployable will be explored to broaden their application scenarios. We envision that the heterostructured surface strategy proposed here represents an innovative solution to decouple the conventional trade-off between heat flux and Leidenfrost point, and will open new avenues for effective heat dissipation of high-power systems.