目的 聚焦铜基表面沸腾传热效率提升难题,通过超亲/疏水改性结合微柱结构设计,突破传统平面铜基表面传热局限,探究改性表面沸腾传热特性,为重力热管等设备性能强化提供支撑。方法 设计并制备平面与微柱结构两类铜基表面,运用氧化及化学处理,构建了多元润湿性表面。搭建可视化池沸腾试验平台,实时监测不同结构与润湿性表面在沸腾过程中的临界热流密度（CHF）、换热系数（HTC）等核心参数;将优化后的改性表面集成于重力热管,设置多种工况,测试热管热阻动态变化,全面解析表面改性对热管传热性能的影响机制。结果 微柱结构对沸腾传热的强化效应显著,其临界热流密度较原始平面提升12.5%,最大换热系数增幅达83.5%。润湿性与结构协同作用呈现差异化规律：疏水平面临界热流密度较原始平面提升23.7%;超亲水微柱表面临界热流密度较原始微柱进一步提升28.5%,最大换热系数提升193.6%。在重力热管应用中,充液率4%和12%条件下,改性表面使热管蒸发段热阻最大降幅达40.7%,显著拓宽热管高效传热区间。结论 微柱结构与超亲水润湿性协同可强化沸腾传热,降低重力热管蒸发段热阻并提升传热能力。本研究为高热流场景中重力热管的应用提供了试验与理论支撑,后续可深化多元结构及润湿性梯度调控研究以拓展技术边界。
Abstract
This study integrates superhydrophilic/superhydrophobic modification with micro-pillar structure design in an innovative way to address the limitations of conventional flat copper surfaces in boiling heat transfer, and systematically explores the enhanced effect of this combined strategy on boiling performance and its application in gravity heat pipes.
Two types of copper-based surfaces, flat structure and micro-pillar structure, were fabricated, each with dimensions of 30 mm×30 mm×3 mm. The micro-pillar surface had uniformly distributed pillars. Each individual pillar had a height of 80 μm and a width of 100 μm, and the gap between adjacent pillars was 60 μm. Oxidation and chemical treatments were applied to achieve diverse wettability: For superhydrophilic surfaces (both flat and micro-pillar), copper substrates were immersed in an etching solution containing 2.5 mol/L potassium hydroxide (KOH) and 0.065 mol/L potassium persulfate (K2S2O8) at 70 ℃ for 30 minutes, followed by heating at 180 ℃ for another 30 minutes to form a hydrophilic oxide layer. For superhydrophobic surfaces (both flat and micro-pillar), the pre-prepared superhydrophilic surfaces were soaked in a 0.002 5 mol/L C18H38S solution at 70 ℃ for 30 minutes, then cleaned with ethanol to remove residues and air-dried to form a hydrophobic film. A total of six surfaces with different structure-wettability combinations were obtained, and their static contact angles were measured with a Data Physics-OCA30 contact angle meter according to the sessile drop method to confirm successful wettability adjustment.
A visualized pool boiling test platform consisting of three core modules was constructed. The heat source module included a portable power supply and a 30 mm×30 mm heating block to control heat flux, with thermal conductive grease and insulation materials used to minimize heat loss. The temperature module employed six K-type thermocouples: two were used to measure the average surface temperature, two were embedded in the heating block 3 mm vertically from the surface thermocouples, and two were used to monitor the temperature of saturated deionized water. The image module included a quartz glass dish (forming a boiling chamber with the test surface), a high-speed camera (608×500 pixels resolution, 500 frames per second frame rate), an LED light source for uniform illumination, and Viewer software for capturing bubble dynamics. Heat flux (q) was calculated via Fourier's law, wall temperature (Tw) via surface temperature correction, wall superheat (ΔT) as the difference between Tw and saturated water temperature, and heat transfer coefficient (HTC, h) as the ratio of q to ΔT. At a fixed heat flux of 1 350 kW/m2, bubble behaviors (detachment diameter, frequency, nucleation site density) were analyzed with image processing software.
The superhydrophilic micro-pillar surface (with optimal boiling performance) was integrated into gravity heat pipes (evaporator: 30 mm, adiabatic section: 40 mm, condensation section: 30 mm in axial length). A heat pipe test system was built, with deionized water as the working fluid, testing under 4%/12% filling ratios and 15 W/30 W/45 W/60 W heating powers, and cooling the condensation section with a 4-5 ℃ cold air jet. Thermal resistance (R) was calculated as the ratio of the evaporation-condensation temperature difference to heating power.
Results showed that compared with the original flat surface, the original micro-pillar surface increased critical heat flux (CHF) by 12.5% and maximum heat transfer coefficient (HTC) by 83.5%; the hydrophobic flat surface improved CHF by 23.7% relative to the original flat surface; the superhydrophilic micro-pillar surface further enhanced CHF by 28.5% and maximum HTC by 193.6% compared with the original micro-pillar surface, attributed to moderate bubble size (average 2.1 mm) and high detachment frequency (≈25 Hz). In gravity heat pipes, the modified surface reduced evaporator thermal resistance by up to 40.7% (20.2% at 4% filling ratio, 24.9% at 12% filling ratio vs. conventional heat pipes).
This study reveals a new synergistic mechanism: micro-pillar structures increase nucleation sites and the heat transfer area, while superhydrophilicity accelerates liquid replenishment after bubble detachment, jointly optimizing bubble dynamics. This combined modification strategy provides a novel approach for enhancing boiling heat transfer and improving gravity heat pipe performance in high-heat-flux scenarios.
关键词
润湿性 /
表面改性 /
池沸腾 /
沸腾传热 /
微柱结构 /
重力热管
Key words
wetability /
surface modification /
pool boiling /
boiling heat transfer /
micro-pillar structure /
gravity heat pipe
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基金
国家自然科学基金（51905275）; 江苏省基础研究计划（自然科学基金）（BK20190752）
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