Dynamic Wetting of Droplet Surface on Supercool Effect
| Autor: | YANG, ZHI-HAN, 楊智涵 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 The purpose of this research is to investigate the effect of dynamic wetting on the hydrophobic and hydrophilic surfaces while the surface temperature was heated from room temperature to the supercooled temperature. The surface tends to absorb water strongly when surface reaches supercooled. However, the hydrophobicity has been proven to have ice-resistant and water-resistant properties. Therefore, these two effects of hydrophobic (non-wetting) surface and supercooled (cold) surface are repellent. However, the hydrophilic (wetting) surface can help the Supercool effect, and these two effects are attracting. The experimental observation shows that droplet impacted on the surfaces with the change of the contact diameter of the droplet spreading and the droplet bounced on the non-wetting surface. The aim of this study focus on the supercool effect with different surface wettabilities. The supercool surfaces with different wetting conditions were tested, with the control variables of temperature level and impact velocity (Weber numbers). At the hydrophilic surface, the results show that the lower temperature had the larger maximum contact diameter of droplets spreading. At the case of wetting surface with the lower Weber number, the maximum contact diameter at -16 °C are 1.5 times larger than at room temperature. The supercool effect helps the droplet spread on hydrophilic surface. However, on the case of non-wetting surface, the difference in droplet contact diameter between -20 °C and 25 °C is small. Because the droplets after impacting will bounce on the super-hydrophobic surface. The dynamic of droplets impacting are totally different on these two cases. Through the energy balance, the potential energy could transfer to the kinematic energy of spreading and bounce after the droplets impacting. This study will finally discuss the energy distribution on the cold effect and wettability effect during the dynamic wetting of the droplets. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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