Abstract

An experimental investigation has been carried out regarding the effect of microstructural parameters of capillary porous coatings produced by directed plasma spraying on the heat transfer and critical heat fluxes during boiling of nitrogen at steady-state heat generation on horizontally-oriented tubular heaters of 3 and 16 mm in diameter. For both the tube diameters, the highest increase in the critical heat flux by a factor of 1.8 as compared with smooth heaters is observed for coatings with the highest porosity. The maximum heat transfer coefficients were observed in three-dimensional capillary-porous (TCP) coatings with large channel widths. Those were more than 3.5 times as high as the heat transfer coefficients on a smooth heater at low heat fluxes. The influence of the thickness of residual layer of microstructured capillary-porous coatings on the heat transfer during nucleate boiling has been shown. Based on the data of high-speed video recording, it has been shown that enhancement of heat transfer during boiling on structured capillary-porous surfaces is not associated with increase in the nucleation site density, but is caused by enhancement of liquid inlet and vapor phase removal in the macrolayer between the ridges of the coating.

中文翻译：

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不同厚度的毛细多孔涂层表面氮池沸腾过程中的传热特征

摘要

已经进行了关于在3和16的卧式管状加热器上以定向等离子喷涂生产的毛细管多孔涂层的微观结构参数对稳态沸腾状态下氮气沸腾期间传热和临界热通量的影响的实验研究直径毫米。对于两种管径，对于孔隙率最高的涂层，与光滑加热器相比，临界热通量的最高增长幅度为1.8倍。在具有大通道宽度的三维毛细孔（TCP）涂层中观察到最大传热系数。它们是低热通量下光滑加热器上传热系数的3.5倍以上。已经显示了微结构毛细管多孔涂层的残留层的厚度对成核沸腾过程中的热传递的影响。根据高速视频记录的数据，已表明，在结构化的毛细孔表面上沸腾期间传热的增强与成核位点密度的增加无关，而是由液体入口和气相的增加引起的在涂层的脊之间的大分子层中去除。