Phase change heat transfer allows high heat transfer rates associated with small temperature variations. Given that this technique is employed in several energy and industry applications, such as automotive air-conditioning evaporators, pulsating heat pipes are used for aerospace thermal management and in semiconductor-manufacturing heat exchangers. Although phase change heat transfer has served mankind for more than two millennia, little progress has been made in the last 40 years regarding the basic performance of phase change heat transfer surfaces. However, laser texturing is expected to change this scenario through wettability modification of heat exchanger surfaces, which can lead to heat transfer improvement. In this context, surface texturing of electrolytic copper (a material commonly employed in phase change heat transfer applications) was performed using a nanosecond pulsed fiber laser source associated to a galvanometric scanner. A design of experiments was performed in order to correlate the parameters’ pulse overlapping, laser power, number of scanning repetitions, and pulse duration to their respective machining features. Machining depth and width were evaluated, as well as the surface integrity of the processed region. These analyses were performed by means of white light interferometry, optical microscopy, and scanning electron microscopy. The surface integrity analysis is especially important, since there is a lack of information regarding texturing effects on surface properties, as most studies focus almost exclusively on surface topography and not on the thermal effects that laser texturing can promote to the substrate material. After comprehending the parameter effects on the machining features, surface textures were manufactured and evaluated in order to define their effect over surface wettability, which influences the heat transfer performance. Copper oxide present on the laser generated textures granted them hydrophilicity so that most of the tested textures achieved contact angles of 0°. A cleaning process with H2SO4 was proposed to remove this oxide and decrease the wettability, also allowing hydrophobic surfaces with a contact angle up to 180° to be obtained.

中文翻译：

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应用于相变传热的激光纹理化铜表面润湿性改性

相变传热允许与小的温度变化相关的高传热速率。鉴于该技术用于多种能源和工业应用，例如汽车空调蒸发器，脉动热管用于航空航天热管理和半导体制造热交换器。尽管相变传热已经为人类服务了两千年多，但在过去的 40 年里，相变传热表面的基本性能却几乎没有取得任何进展。然而，激光纹理有望通过换热器表面的润湿性改性来改变这种情况，从而改善传热。在这种情况下，电解铜（一种常用于相变传热应用的材料）的表面纹理是使用与电流扫描仪相关联的纳秒脉冲光纤激光源进行的。进行了实验设计，以便将参数的脉冲重叠、激光功率、扫描重复次数和脉冲持续时间与其各自的加工特征相关联。评估加工深度和宽度，以及加工区域的表面完整性。这些分析是通过白光干涉测量法、光学显微镜和扫描电子显微镜进行的。表面完整性分析尤其重要，因为缺乏有关表面特性的纹理效应的信息，因为大多数研究几乎只关注表面形貌，而不是激光纹理对基材的热效应。在了解参数对加工特征的影响后，制造和评估表面纹理，以定义它们对影响传热性能的表面润湿性的影响。存在于激光生成纹理上的氧化铜赋予它们亲水性，因此大多数测试纹理实现了 0° 的接触角。建议使用 H2SO4 进行清洁过程以去除这种氧化物并降低润湿性，同时还可以获得接触角高达 180° 的疏水表面。制造和评估表面纹理以定义它们对影响传热性能的表面润湿性的影响。存在于激光生成纹理上的氧化铜赋予它们亲水性，因此大多数测试纹理实现了 0° 的接触角。建议使用 H2SO4 进行清洁过程以去除这种氧化物并降低润湿性，同时还可以获得接触角高达 180° 的疏水表面。制造和评估表面纹理以定义它们对影响传热性能的表面润湿性的影响。存在于激光生成纹理上的氧化铜赋予它们亲水性，因此大多数测试纹理实现了 0° 的接触角。建议使用 H2SO4 进行清洁过程以去除这种氧化物并降低润湿性，同时还可以获得接触角高达 180° 的疏水表面。