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首页> 外文会议>American Society of Mechanical Engineers(ASME) Summer Heat Transfer Conference(HT2005) vol.2; 20050717-22; San Francisco,CA(UA) >HETEROGENEOUS NUCLEATION WITH ARTIFICIAL CAVITIES
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HETEROGENEOUS NUCLEATION WITH ARTIFICIAL CAVITIES

机译：人造腔的异质成核

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摘要

Bubble incipience in artificial cavities manufactured from silicon has been studied using gas nucleation and pool boiling. Moderately wetting water and highly wetting ethanol have both been used as the bulk fluid with cylindrical cavities, as well as those with a triangle, square, and rectangle shape cross section. Nominal cavity sizes range from 8 to 60 μm. The incipience conditions observed for water using both gas nucleation and pool boiling suggest that bubble initiation originates from a concave meniscus. Cornwell's contact angle hysteresis theory for vapor trapping cavities is used to explain the gas nucleation results. The pool boiling results are more difficult to explain. Using ethanol, cavities appeared to be completely flooded and were not activated using either gas nucleation or pool boiling. Using water and gas nucleation cavities were almost always activated, provided the incipience criterion was satisfied; in contrast cavities in pool boiling with water activated with different superheats during different experiments. The difference in incipience behavior between gas nucleation and pool boiling with water is explained based on vapor trapping and thermal suppression considerations. Based on limited experimental results, it appears that the backpressure does not influence gas bubble incipience, provided the pressure difference is the same. The experimental results presented affirm the theory of heterogeneous nucleation from vapor trapping cavities provided contact angle hysteresis and vapor trapping are fully accounted for. However, the results also suggest that the theoretical considerations required for a deterministic model for incipience from vapor trapping cavities during boiling is more complex than previously hypothesized.
机译：已经使用气体成核和熔池沸腾研究了由硅制成的人造腔中的气泡开始。中度湿润的水和高度湿润的乙醇都已被用作具有圆柱形空腔以及具有三角形，正方形和矩形横截面的本体流体。标称腔尺寸范围为8至60μm。使用气体成核和熔池沸腾观察到的水的初始条件表明，气泡的产生起源于凹弯月面。用Cornwell的气相捕集腔的接触角滞后理论来解释气体成核的结果。池沸腾的结果更难以解释。使用乙醇，腔似乎被完全淹没，并且没有通过气体成核或池沸腾而被激活。只要满足初始标准，使用水和气体成核腔几乎总是被激活。相比之下，在不同的实验中，以不同的过热度活化的水在池中沸腾的腔体。基于蒸汽捕集和热抑制的考虑，解释了气体成核和水与池沸腾之间的初始行为差异。根据有限的实验结果，如果压差相同，则看来背压不会影响气泡的产生。提出的实验结果肯定了在充分考虑了接触角滞后和蒸气捕集的情况下，蒸气捕集腔的异相成核理论。但是，结果还表明，确定性模型在沸腾过程中因蒸气陷获腔而产生的初潮所需的理论考虑要比先前的假设更为复杂。

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