Liquid Super-Spreading Boosted High-Performance Jet-Flow Boiling for Enhancement of Phase-Change Cooling.

Abstract

Enhanced boiling heat transfer via surface engineering is a topic of general interest for its great demand in industrial fields. However, as a dynamic interfacial phenomenon, deep understanding of its process and mechanism, including liquid re-wetting and vapor departure, is still challenging. Herein, we design a micro-/nanostuctured Cu surface containing periodic micro-groove/pyramid array with rich nano-wrinkles, where super-spreading (<134.1ms) of organic cooling agents highly boosts liquid re-wetting process, causing a discontinuous solid-liquid-vapor three-phase contact line and ultra-low under-liquid bubble adhesion force (∼1.3 μN). Therefore, a characteristic, ultra-fast jet-flow boiling (bubbles rapidly ejected in multiple strips) is obtained on this surface, giving a priority to nucleation (superheat ∼1.5°C) and simultaneously enhancing the critical heat flux and heat-transfer coefficient by up to 80% and 608%, respectively, compared with a flat surface. In situ observation and analysis of the nucleation, growth, and departure of micro-sized jet-flow bubbles reflects that micro-grooves/pyramids with nano-wrinkles promote the latent heat exchange process by super-spreading induced ultra-fast liquid re-wetting and constant vapor film coalescing. Based on the designed structures, high-performance phase-change cooling for CPU heat management in supercomputer centers is accomplished with an ultra-low power usage effectiveness (PUE<1.04). This article is protected by copyright. All rights reserved.