Unified icing theory based on phase transition of supercooled water on a substrate
Unified icing theory based on phase transition of supercooled water on a substrate
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DOI：
10.1016/j.ijheatmasstransfer.2018.03.028
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发表时间：
2018-08-01
影响因子：
5.2
通讯作者：
Liu, Hong
中科院分区：
文献类型：
--
作者：
Kong, Weiliang;Liu, Hong
由于缺乏对结冰的了解，我们无法预测结冰和防冰研究中典型的结冰特性的影响。为了理解基片上结冰的物理过程，必须探索基片上结冰的图案形成和尖端形状。本文通过一系列实验，研究了不同导热系数和表面能条件下，冰在不同基板上的形态、速度和尖端形状。实验结果表明，随着过冷度和导热系数的增加，基板上的冰由单针状的树枝状向光滑的冰膜演化。相反，对于自由结冰，相同的演变过程可以在比衬底结冰更高的过冷度下完成。在亲水性和有机玻璃表面的实验结果表明，在约271.6 K时，冰的速度和冰粒数急剧下降，而冰尖形状没有明显变化，而对于自由结冰则没有发现这种现象。此外，还对基片结冰的相变进行了理论分析。结果表明，与自由冰相比，衬底表面能使亚稳立方冰的尺寸增大，冰尖温度降低1.5K，从而导致冰的速度和Peclet数减小。与自由结冰相比，在较低过冷度条件下，基材的导热降低了结冰方向的热流密度，导致了基材结冰的绝对稳定性。通过对自由结冰和衬底结冰的比较，提出了描述平衡结冰模式、非平衡生长状态以及相应的生长方程的统一结冰理论。利用该理论可以很好地预测不同过冷度、不同导热系数和不同表面能条件下的结冰速度和结冰形态，以及自由结冰的结果。(C)2018爱思唯尔有限公司。保留所有权利。
Lack of knowledge on substrate icing hinders us from predicting the effects of typical substrate properties in icing and anti-icing research. The pattern formation and tip shape of icing on a substrate must be explored to understanding the physics of icing on a substrate. In this paper, the pattern, velocity and tip shape of ice on substrates with different thermal conductivities and surface energies are evaluated in a series of experiments. Experimental results show that as supercooling and thermal conductivity increase, the ice on substrate evolves from a single-needle dendrite to a smooth ice film. In contrast, for free icing the same evolution process can be completed at a higher supercooling than substrate icing. Experimental results on hydrophilic and Plexiglas surfaces demonstrate an abruptly decrease of velocity and Peclet number of ice occurs at approximately 271.6 K, whereas the tip shape of ice does not change obviously; while for free icing this phenomenon is not found. Furthermore, a theoretical analysis on phase transition of substrate icing is performed. It shows that the surface energy of substrates can increase the size of metastable cubic ice and reduce the temperature on the ice tip by 1.5 K compared to free ice, thereby causing the decrease in the velocity and Peclet number of ice. Also the heat conduction of substrates decrease the heat flux in ice growth direction and lead to absolute stability of substrate icing in lower supercooling compared to free icing. In terms of the comparison between free icing and substrate icing, a unified icing theory is proposed to describe the equilibrium icing mode, the nonequilibrium growth state, and the corresponding growth equations. Using this theory, the velocity and pattern of substrate icing with different supercooling, thermal conductivity, and surface energy can be predicted well, as well as these results of free icing. (C) 2018 Elsevier Ltd. All rights reserved.