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Effects of Droplet Diameter and Fluid Properties on the Leidenfrost Temperature of Polished and Micro/Nanostructured Surfaces

机译:液滴直径和流体性质对抛光和微/纳米结构表面的莱顿弗罗斯特温度的影响

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An experimental investigation of the effects of droplet diameters and fluid properties on the Leidenfrost temperature of polished and nanolmicrostructured surfaces has been carried out. Leidenfrost experiments were conducted on a stainless steel 304 polished surface and a stainless steel surface which was processed by a femtosecond laser to form above surface growth (ASG) nanolmicrostructures. Surface preparation resulted in a root mean square roughness (R_(rms)) of 4.8 μm and 0.04 μm on the laser processed and polished surfaces, respectively. To determine the Leidenfrost temperatures, the droplet lifetime method was employed using deionized (DI) water and HFE 7300DL. A precision dropper was used to vary the size of DI water droplets from 1.5 to 4 mm. The Leidenfrost temperature was shown to display increases as high as 100℃ on the processed surface over the range of droplet sizes, as opposed to a 40 ℃ increase on the polished surface. Average increases of the Leidenfrost temperature between polished and processed samples were as high as 200℃. The experiment was repeated with HFE 7300DL; however, with no noticeable changes of the Leidenfrost temperatures with droplet size whether on the polished or the processed surface. The difference in the Leidenfrost behavior between DI water and HFE 7300DL and among the various droplet sizes can be attributed to the nature of the force balance and flow hydrodynamics at a temperature slightly below the Leidenfrost point (LFP).
机译:对液滴直径和流体性质对抛光和纳米微结构表面的莱顿弗罗斯特温度的影响进行了实验研究。在不锈钢304抛光表面和不锈钢表面上进行Leidenfrost实验,该表面经过飞秒激光处理以形成表面以上生长(ASG)纳米微结构。表面处理在激光加工和抛光表面上的均方根粗糙度(R_(rms))分别为4.8μm和0.04μm。为了确定莱顿弗罗斯特的温度,使用了去离子(DI)水和HFE 7300DL的液滴寿命方法。使用精密滴管将DI水滴的大小从1.5毫米更改为4毫米。莱顿弗罗斯特的温度在整个液滴尺寸范围内显示出在加工表面上高达100℃的升高,而在抛光表面上则升高40℃。抛光样品和加工样品之间的莱顿弗罗斯特温度平均升高高达200℃。使用HFE 7300DL重复该实验;但是,无论是在抛光表面还是在处理过的表面上,莱顿弗罗斯特温度都不会随液滴大小而发生明显变化。去离子水和HFE 7300DL之间以及各种液滴尺寸之间的莱顿弗罗斯特行为的差异可以归因于力平衡的性质和在略低于莱顿弗罗斯特点(LFP)的温度下的流动流体动力学。

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