Abstract

Boiling is an efficient mode of heat transfer and has important applications that use high heat flux systems. However, a single wettable boiling surface is not appropriate for the dual requirements of low superheat for nucleation and high critical heat flux. Here, we present a hydrophilic composite and a functional hydrophilic-hydrophobic partitioned porous structure that significantly improves boiling heat transfer performance via a double-sintering process. The superheat requirement for the onset of nucleate boiling decreased from 2°C on the single hydrophilic porous structure to 1°C on the hydrophilic-hydrophobic porous structure, the critical heat flux was reduced by 3.3% in the early stages of boiling (below 250 kW/m²), the heat transfer efficiency increased by 20%, and the heat transfer was comparable to that of the hydrophilic porous structure. Bubble dynamics were observed using a high-speed camera. The results demonstrate that the bubble nucleation sites mainly occur in the hydrophobic region and this is attributed to a decrease in the energy barrier for nucleation. The bubble dynamic statistics revealed that the product of the diameter of the bubble and the bubble escape frequency are similar for composite surfaces and hydrophilic porous surfaces, which is consistent with Zuber’s conclusion. The synergistic effect of the hydrophilic-hydrophobic partitioned porous structure can promote nucleation in the hydrophobic region and retain capillary suction for liquid reflux in the hydrophilic region to enhance boiling heat transfer. This work enables the large-scale deployment of heat exchanger surface processing technology because of its low cost, availability, and reliability.

中文翻译：

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亲水-疏水多孔结构增强核池沸腾传热的协同效应

摘要

沸腾是一种有效的传热模式，在使用高热通量系统方面具有重要的应用。然而，单一的可润湿沸腾表面并不适合低成核过热度和高临界热通量的双重要求。在这里，我们提出了一种亲水复合材料和功能性亲水-疏水分区多孔结构，可通过双烧结工艺显着提高沸腾传热性能。核态沸腾开始的过热度要求从单一亲水多孔结构上的2℃降低到亲水-疏水多孔结构上的1℃，沸腾初期临界热通量降低了3.3%（低于250℃）。 kW/m ²），传热效率提高20%，传热效果与亲水多孔结构相当。使用高速相机观察气泡动力学。结果表明，气泡成核位点主要发生在疏水区域，这归因于成核能垒的降低。气泡动态统计表明，复合材料表面和亲水性多孔表面的气泡直径与气泡逃逸频率的乘积相似，这与Zuber的结论一致。亲水-疏水分区多孔结构的协同效应可以促进疏水区的成核，并在亲水区保留液体回流的毛细管吸力，从而增强沸腾传热。这项工作因其低成本、可用性和可靠性而使得换热器表面处理技术得以大规模部署。