Abstract This study investigates critical heat flux (CHF) enhancement in pool boiling of FC-72 under saturated and subcooled conditions using laser-textured stainless-steel surfaces in combination with a hydrophobic coating. Multiple types of surfaces with capillary-length-spaced circular spots of different diameters are prepared with the spots being either untreated, hydrophobized or laser pretreated and hydrophobized. Pool boiling measurements are performed at atmospheric pressure on electrically heated ribbons. The CHF versus subcooling behavior is modeled using an established linear equation, while a modification into a second-degree polynomial is also tested to better account for nonlinear behavior of some surfaces. All developed surfaces are found to increase the CHF with enhancements ranging from 36 to 73% at saturation and 34–65% at 12 K of subcooling. Surfaces with mixed regions of low and high wettability generally exhibited the highest CHF enhancement at a 31% coverage with low wettability areas. Samples with laser-pretreated and hydrophobized spots exhibited the highest overall performance at saturation but a less steep trend of CHF versus liquid subcooling increase and CHF increase with increased superhydrophobic area ratio, indicating a different enhancement mechanism with hydrophobized microcavities presumably serving as preferential nucleation sites. Modeling of the CHF versus subcooling trend showed that (i) a second-degree polynomial equation is more appropriate for some surface types and (ii) the obtained constants differ significantly from surface to surface. Evaluation of a universal model based on all datapoints obtained within this study showed inadequate performance with error margins of ±13.5%. Consequently, the use of individual models for each type of enhanced surfaces with an overall accuracy of ±5.9% is recommended.

中文翻译：

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FC-72 池沸腾中激光织构不锈钢带状加热器的过冷临界热通量

摘要 本研究使用激光纹理不锈钢表面结合疏水涂层，研究了在饱和和过冷条件下 FC-72 池沸腾的临界热通量 (CHF) 增强。制备具有不同直径的毛细管长度间隔圆形斑点的多种类型的表面，这些斑点未经处理、疏水化或激光预处理和疏水化。池沸腾测量是在大气压下在电加热带上进行的。CHF 与过冷行为使用既定的线性方程建模，同时还测试了对二次多项式的修改，以更好地说明某些表面的非线性行为。发现所有开发的表面都增加了 CHF，在饱和时增加了 36% 到 73%，在 12 K 过冷度下增加了 34-65%。具有低润湿性和高润湿性混合区域的表面通常在低润湿性区域的覆盖率为 31% 时表现出最高的 CHF 增强。具有激光预处理和疏水化斑点的样品在饱和时表现出最高的整体性能，但 CHF 相对于液体过冷增加和 CHF 随超疏水面积比增加而增加的趋势不太陡峭，这表明疏水化微腔可能作为优先成核位点的不同增强机制。CHF 与过冷趋势的建模表明 (i) 二次多项式方程更适合某些表面类型，并且 (ii) 获得的常数因表面而异。基于本研究中获得的所有数据点对通用模型的评估显示性能不足，误差幅度为 ±13.5%。因此，建议对每种类型的增强表面使用单独的模型，整体精度为 ±5.9%。