Dynamics of microscale droplets impinging onto hot surfaces with oxide layers

微尺度液滴撞击具有氧化层的热表面的动力学

基本信息

批准号：
18J11928
负责人：
WANG Zhenying
金额：
$ 1.22万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for JSPS Fellows
财政年份：
2018
资助国家：
日本
起止时间：
2018-04-25 至 2020-03-31
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18J11928/
关键词：
lubrication model vapor absorption droplet liquid desiccant solutal Marangoni capillary flow droplet dynamics wetting and spreading phase change

项目摘要

First,the effect of substrate conductivity on the vapor absorption into hygroscopic liquid desiccant droplets is investigated experimentally. Results indicate that substrate conductivity plays a crucial role in the transient heat transfer process. As a result of the thermal effect, droplets on copper substrates show a slightly higher rate of vapor absorption than those on low-thermal conductivity PTFE substrates. Further analyses by decomposing the variation of water vapor pressure indicate that, compared to the influence of temperature change, the water vapor pressure at the droplet surface is greatly affected by the change of solute concentration during vapor absorption, and therefore the rate of vapor absorption.Second, a lubrication-type model is developed to simulate the evaporation and vapor absorption process of hygroscopic ionic solution droplet. The investigation makes it possible to fully elucidate the governing mechanisms of droplet motions with both positive and negative interfacial mass fluxes. We elucidate that, along with interfacial phase change, the capillary effect, the thermal Marangoni effect and the solutal Marangoni effect interact with each other, and lead to the time-varying behaviors of hygroscopic solution droplets that differ from evaporating volatile droplets. The conclusions provide reasonable explanations for the spreading and contracting phenomena along with vapor absorption, and for the dendritic structures at the periphery of evaporating aqueous solution droplets in the existing literature.

首先，实验研究了底物电导率对蒸气吸收到吸湿性液体干燥液滴中的影响。结果表明，底物电导率在瞬态传热过程中起着至关重要的作用。由于热效应的结果，铜底物上的液滴显示出比低热电导率PTFE底物的蒸气吸收率略高。 Further analyses by decomposing the variation of water vapor pressure indicate that, compared to the influence of temperature change, the water vapor pressure at the droplet surface is greatly affected by the change of solute concentration during vapor absorption, and therefore the rate of vapor absorption.Second, a lubrication-type model is developed to simulate the evaporation and vapor absorption process of hygroscopic ionic solution droplet.该研究使得有可能完全阐明液滴运动的管理机制，并具有正界面质量通量。我们阐明了这一点，随着界面变化，毛细管效应，热马龙尼效应和溶质马龙诺效应相互相互作用，并导致与蒸发挥发性液滴不同的吸湿溶液液滴的时变行为。结论为扩散和收缩现象以及蒸气吸收提供了合理的解释，以及在现有文献中蒸发水溶液液滴的外围的树突结构。