Adaptive Hotspot Cooling with Self-Propelled Jumping Condensate

Duke University, Durham NC

Investigators

Abstract

CBET-1236373 Chuan-Hua Chen Duke University Mobile hotspots are prevalent in electronic systems, including microprocessors and power electronics with constantly changing computing tasks and external payloads. Existing cooling solutions are generally designed for fixed hotspots (e.g. thermoelectric coolers) or slowly varying heat loads (e.g. flat plate heat pipes), and are therefore not adequate to address the cooling challenges of moving hotspots. This study aims at developing a novel phase-change cooling mechanism for adaptive thermal management of hotspots, where the self-propelled jumping of dropwise condensate on superhydrophobic surfaces is utilized to promote liquid return to the evaporator. The cooling system consists of water/vapor enclosed by two closely spaced parallel plates, a superhydrophilic evaporator and a superhydrophobic condenser. The hotspots on the evaporator drive the working fluid to vaporize and then condense on the opposing plate. When multiple condensate drops coalesce together, the released surface energy propels the merged drop to jump perpendicularly back to the hotspots, completing the liquid return and sustaining the phase change process. The adaptive cooling is accomplished by the preferential evaporation of the working fluid at the hotspots and the rapid jumping return across the very short inter-plate distance. The jumping-condensate approach offers a unique combination of hotspot cooling capabilities: (i) rapid response to moving hotspots; (ii) adaptive cooling for minimal thermal gradients; and (iii) passive cooling independent of external forces. Through integrated experimental and numerical investigations that are guided by simple scaling laws, the self-propelled jumping condensate will be studied in the context of adaptive hotspot cooling. In terms of interfacial transport phenomena, the project is expected to yield physical insights to surface-energy-powered jumping processes, which are widely observed in nature and potentially useful for improving industrial condensers. In terms of thermal transport processes, the project offers a fundamentally new mechanism for condensate return in phase change systems and a novel approach for adaptive thermal management of moving hotspots. This project is potentially transformative in enabling the thermal management of mobile hotspots which bottleneck the performance of state-of-the-art microprocessors and power electronics. The proposed research is also applicable to the promotion of self-sustained dropwise condensation, particularly for applications where favorable external forces may not exist (e.g. spacecraft cooling), and the development of biomimetic materials and systems harvesting interfacial energy (e.g. anti-dew materials). In addition to training graduate students and attracting minority undergraduates to STEM research, the project will strive to outreach to K-12 students and the general public. Through the PI?s ongoing CAREER program, a high school teacher will continue to translate cutting-edge research in the PI?s lab into refereed curricular units published at teachengienering.org. When appropriate, this project will also leverage the PI?s past successes with major media outlets such as the Discovery Channel to disseminate the research findings.