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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Nucleate boiling on ultra-smooth surfaces: Explosive incipience and homogeneous density of nucleation sites
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Nucleate boiling on ultra-smooth surfaces: Explosive incipience and homogeneous density of nucleation sites

机译：在超光滑的表面上核心煮沸：爆炸性兴趣和均匀密度的成核位置

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摘要

Pool boiling heat transfer characteristics in saturation conditions are investigated on rough and ultra-smooth surfaces of several aluminum samples, acetone being the working fluid. The topography of the surfaces is analyzed with a confocal microscope: the samples are methodically scanned in order to record the height or the depth of each point of the surface with respect to its mean altitude. This analysis enables to characterize both the mean roughness of the sample but also the presence of significant imperfections due to the polishing process. Depending on the characteristics of the surfaces, different types of boiling incipience - from gradual to explosive - are observed using a high speed camera.. When the heat flux is gradually decreased following boiling incipience on an ultra-smooth surface, nucleate boiling subsists for very small heat fluxes, leading to a homogeneous distribution of very small bubbles on the entire surface. On the contrary, in the same conditions, rough surfaces or ultra-smooth surfaces with imperfections are not able to sustain nucleation: for decreasing heat fluxes, a decreasing number of dispersed nucleation sites producing large bubbles is observed, before the full extinction of the boiling process for a heat flux much higher than with the ultra-smooth surface. For increasing heat fluxes, the results show that ultra-smooth surfaces with a small number of imperfections deliver the best thermal performance. (C) 2017 Elsevier Inc. All rights reserved.
机译：在几个铝样品的粗糙和超光滑表面上研究了饱和度条件下的池沸腾的传热特性，丙酮是工作流体。用共聚焦显微镜分析表面的地形：有条定地扫描样品，以便以相对于其平均高度记录表面的每个点的高度或深度。该分析使得能够表征样品的平均粗糙度，但也具有由于抛光过程而存在显着的缺陷。根据表面的特点，使用高速摄像机观察到不同类型的沸腾兴奋剂 - 从逐渐到爆炸 - 使用高速相机。在超光滑的表面上煮沸的兴奋剂后，热通量逐渐减少，核心沸腾的血管沸腾小热量通量，导致整个表面上非常小气泡的均匀分布。相反，在相同的条件下，具有缺陷的粗糙表面或超光滑表面不能维持成核：用于减少热量，在沸腾的全部灭绝之前，观察到产生大气泡的分散成核点的数量减少热通量的方法远高于超光滑表面。为了增加热量通量，结果表明，具有少量缺陷的超光滑表面可提供最佳的热性能。 （c）2017年Elsevier Inc.保留所有权利。

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