The Thickness of the Liquid Microlayer Between a Cap-Shaped Sliding Bubble and a Heated Wall: Experimental Measurements
The Thickness of the Liquid Microlayer Between a Cap-Shaped Sliding Bubble and a Heated Wall: Experimental Measurements
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DOI：
10.1115/1.2241858
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发表时间：
2006-09
影响因子：
--
通讯作者：
Xin Li;D. K. Hollingsworth;L. Witte
中科院分区：
文献类型：
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作者：
Xin Li;D. K. Hollingsworth;L. Witte
发展了一种基于激光的测量方法，用于测量帽状滑动气泡和倾斜加热壁间的液体微层厚度。众所周知，滑动的蒸汽泡会沿着它们滑动的表面产生高的换热系数。这一过程的细节仍不清楚，取决于气泡和表面之间形成的微层的演变。过去的实验使用均匀产热表面上的热传递测量来通过能量平衡来推断微层厚度。这些研究已经为制冷剂和水提供了20-100μm的测量结果，但它们尚未得到不依赖于第一定律封闭的直接测量的证实。本文给出的结果是由基于反射率的光纤激光探头直接测量的微层厚度。给出了探头的结构和校准的详细情况。报道了饱和FC-87和与水平线成2°至15°倾斜的均匀温度面的数据。将毫米大小的FC-87蒸汽球形气泡注入到均匀加热的铝板的下端附近。激光探头产生的帽状气泡的微层厚度为22-55μm。气泡雷诺数从600到4800，弗劳德数从0.9到1.7，韦伯数从2.6到47。帽状气泡上方的微层厚度与倾角和气泡形状因子有关。成功的关联表明，这个数据集可以用来验证微层动力学详细模型的结果。
A laser-based method has been developed to measure the thickness of the liquid microlayer between a cap-shaped sliding bubble and an inclined heated wall. Sliding vapor bubbles are known to create high heat transfer coefficients along the surfaces against which they slide. The details of this process remain unclear and depend on the evolution of the microlayer that forms between the bubble and the surface. Past experiments have used heat transfer measurements on uniform-heat-generation surfaces to infer the microlayer thickness through an energy balance. These studies have produced measurements of 20–100 μm for refrigerants and for water, but they have yet to be confirmed by a direct measurement that does not depend on a first-law closure. The results presented here are direct measurements of the microlayer thickness made from a reflectance-based fiber-optic laser probe. Details of the construction and calibration of the probe are presented. Data for saturated FC-87 and a uniform-temperature surface inclined at 2 deg to 15 deg from the horizontal are reported. Millimeter-sized spherical bubbles of FC-87 vapor were injected near the lower end of a uniformly heated aluminum plate. The laser probe yielded microlayer thicknesses of 22–55 μm for cap-shaped bubbles. Bubble Reynolds numbers range from 600 to 4800, Froude numbers from 0.9 to 1.7, and Weber numbers from 2.6 to 47. The microlayer thickness above cap-shaped bubbles was correlated to a function of inclination angle and a bubble shape factor. The successful correlation suggests that this data set can be used to validate the results of detailed models of the microlayer dynamics.