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Limitations of Matching Condensing Film Profile on a Micro Fin with the Groove: Critical Effect of Disjoining Pressure
Nanoscale and Microscale Thermophysical Engineering ( IF 4.1 ) Pub Date : 2019-06-25 , DOI: 10.1080/15567265.2019.1633712
Mobin Alipour 1, 2 , Zafer Dursunkaya 3
Affiliation  

ABSTRACT Condensation on a fin top terminating with a groove involves several simultaneous phenomena including vapor–liquid boundaries whose shapes are unknown a priori, fluid flow due to capillary and disjoining pressure gradients, and condensation over thin films. This problem occurs in grooved heat pipes, where the condensation is predominantly present on fin tops due to the thinner liquid film – having a lower thermal resistance compared to inside the groove where the fluid is substantially thicker. Majority of the studies in the literature assume an approximate profile for the liquid film surface and apply an integral balance for conservation laws, accounting for the effect of the capillary pressure only. In addition, this approximate profile is matched with the liquid profile inside the groove, which serves as a boundary condition. Although intuitive, validity of the matching is not straightforward, and its limitations have never been discussed in the literature, despite the presence of experimental findings to the contrary. In the current study, the effect of disjoining pressure and matching conditions with the groove is investigated using a comprehensive model. The results suggest that for small temperature differences and small slopes, the effect of disjoining pressure is non-negligible, and beyond limiting values of edge angles, the effect of disjoining pressure precludes solutions where the fin top film matches the groove in a smooth transition.

中文翻译:

在带凹槽的微翅片上匹配冷凝膜轮廓的局限性:分离压力的临界影响

摘要 以凹槽终止的翅片顶部的冷凝涉及多种同时发生的现象,包括形状未知的汽液边界、由于毛细管和分离压力梯度引起的流体流动以及薄膜上的冷凝。这个问题发生在带槽的热管中,由于较薄的液膜,冷凝主要出现在翅片顶部 - 与流体较厚的槽内相比,其热阻较低。文献中的大多数研究都假设了液膜表面的近似轮廓,并应用了守恒定律的积分平衡,仅考虑了毛细管压力的影响。此外,该近似轮廓与凹槽内的液体轮廓相匹配,作为边界条件。尽管直观,但匹配的有效性并不简单,尽管存在相反的实验结果,但文献中从未讨论过其局限性。在当前的研究中,使用综合模型研究了分离压力和与凹槽匹配条件的影响。结果表明,对于小温差和小斜率,分离压力的影响是不可忽略的,并且超出边缘角的极限值,分离压力的影响排除了鳍顶膜与凹槽以平滑过渡相匹配的解决方案。使用综合模型研究分离压力和与凹槽匹配条件的影响。结果表明,对于小温差和小斜率,分离压力的影响是不可忽略的,并且超出边缘角的极限值,分离压力的影响排除了鳍顶膜与凹槽以平滑过渡相匹配的解决方案。使用综合模型研究分离压力和与凹槽匹配条件的影响。结果表明,对于小温差和小斜率,分离压力的影响是不可忽略的,并且超出边缘角的极限值,分离压力的影响排除了鳍顶膜与凹槽以平滑过渡相匹配的解决方案。
更新日期:2019-06-25
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