Effect of the surface roughness and oxidation layer on the dynamic behavior of micrometric single water droplets impacting onto heated surfaces
Effect of the surface roughness and oxidation layer on the dynamic behavior of micrometric single water droplets impacting onto heated surfaces
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DOI：
10.1016/j.ijthermalsci.2013.03.004
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发表时间：
2013-08
影响因子：
4.5
通讯作者：
E. Negeed;S. Hidaka;M. Kohno;Y. Takata
中科院分区：
文献类型：
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作者：
E. Negeed;S. Hidaka;M. Kohno;Y. Takata
本文研究了表面粗糙度振幅和表面氧化层厚度对微米单水滴在高温下与表面碰撞时动态行为的影响。不锈钢级304 （sus304）表面不同幅度的表面粗糙度；Ra=0.04、2、4、6、8和10 μm。每个传热面被加热到不同的温度；1108, 1158和1198K，以控制热表面的氧化层厚度。单个水滴从微射流分配器的针头中喷射出来，水滴的大小和速度是独立控制的。用高速摄像机观察了液滴与热表面碰撞过程中的行为。通过对实验结果的分析，研究了表面粗糙度振幅、氧化层厚度、液滴韦伯数和表面过热度对固液热接触时间和液滴最大扩散直径的影响。推导了单个液滴撞击受热表面时的水动力特性与影响参数之间的经验关联关系。此外，将现有结果与其他研究者的结果进行了比较，显示了氧化层厚度和表面粗糙度幅度对水滴在加热表面上的冲击行为的影响。
The present research study investigates the effects of surface roughness amplitude and surface oxide layer thickness on the dynamic behavior of micrometric single water droplets during collision with surfaces at high temperature. Stainless steel-grade 304 (SUS 304) surfaces of different amplitudes of surface roughness; Ra=0.04, 2, 4, 6, 8 and 10 μm, have been considered. Each heat transfer surface was heated up to different temperatures; 1108, 1158 and 1198K, to control the oxide layer thickness over the hot surface. An individual water droplet is ejected from a needle of the micro jet dispenser where the droplet's size and its velocity were controlled independently. The behavior of droplet during the collision with hot surface was observed with a high-speed camera. By analyzing the experimental results, the effects of the surface roughness amplitude, oxide layer thickness, droplet Weber number, and surface superheat on the hot solid–liquid contact time, and on the maximum droplet spread diameter were investigated. Empirical correlations have been deduced describing the relationship between the hydrodynamic characteristics of an individual droplet impinging on a heated surface and concealing the affecting parameters in such process. Also, the comparison between the current results and the results due to other investigators shows the effects of oxide layer thickness and surface roughness amplitude on the impact behavior of water droplet onto the heated surfaces.