Evaporation dynamics of microbubbles
Evaporation dynamics of microbubbles
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DOI：
10.1016/j.ces.2013.05.026
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发表时间：
2013-09-20
影响因子：
4.7
通讯作者：
Bandulasena, H. C. Hemaka
中科院分区：
文献类型：
--
作者：
Zimmerman, William B.;Al-Mashhadani, Mahmood K. H.;Bandulasena, H. C. Hemaka
直到最近，产生微气泡云还是一个相对昂贵的提议，最小的气泡需要来自饱和成核机制或文丘里效应的高能量密度。由于微泡处理的成本较高，对微泡对物理化学过程的加速效应的探索在很大程度上尚未被研究，特别是那些综合效应。在本文中，主要通过计算模型但得到一些实验证据的支持，探讨了微泡界面上的传热和蒸发之间的权衡。假设这两个过程本质上都是瞬态的，但在短停留时间内，有利于汽化，而在较长停留时间内，显热传递占主导地位，并导致最初汽化液体的再冷凝。该计算模型解决了层厚度有多薄将导致最大绝对汽化，之后随着气泡冷却，显热传递使蒸汽冷凝。该最大汽化层厚度估计为几百微米，最多为几个微泡直径。如果准确估计最大汽化估计和实现它所需的接触时间，则这些是设计汽化系统所需的工程设计特征，以实现以最小传热实现最大程度去除蒸汽。这里提出的建模工作应该考虑到还进行的加湿实验，该实验显示出口空气处于 100% 饱和度，但气体温度随着层高的降低而增加，水温随着层高的降低而降低，所有这些都与计算模型的预测一致。 (C) 2013 爱思唯尔。爱思唯尔有限公司出版。保留所有权利
Until recently, generating clouds of microbubbles was a relatively expensive propositson, with the smallest bubbles requiring high energy density from either the saturation nucleation mechanism or Venturi effect. Due to the expense of processing with microbubbles, exploration of the acceleration effects of microbubbles for physico-chemical processes are largely unstudied, particularly those that are combined effects. In this paper, the trade-off between heat transfer and evaporation on the microbubble interface are explored, largely by computational modelling but supported by some experimental evidence. The hypothesis is that both processes are inherently transient, but that during short residence Limes, vaporization is favoured, while at longer residence Limes, sensible heat transfer dominates and results in re condensation of the initially vaporized liquid. The computational model address how thin a layer thickness will result in the maximum absolute vaporization, after which sensible heat transfer condenses the vapour as the bubble cools. This maximum vaporization layer thickness is estimated to be a few hundred microns, on the order of a few microbubble diameters at most If the maximum vaporization estimate and the contact time necessary to achieve it are accurately estimated, these are engineering design features needed to design a vaporizing system to achieve maximum removal of vapour with minimum heat transfer. The modelling work presented here should be considered in light of the humidification experiments also conducted which showed the exit air at 100% saturation, but increasing gas temperature with decreasing layer height, and decreasing water temperature with decreasing layer height, all of which are consistent with the predictions of the computational model. (C) 2013 Elsevier. Published by Elsevier Ltd. All rights reserved