Air Bubble Entrapment for Water Drop Impinging on Graphite and Polycarbonate Surfaces

• Main Authors: Ren-jing Wang, 王任群
• Other Authors: Shi-yow Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/89751884527448050388

碩士 === 國立臺灣科技大學 === 化學工程系 === 102 === The phenomenon of bubble entrapment was studied for water drop impinging on graphite and polycarbonate substrates in this work. Four graphite substrates with advancing contact angle (90, 120, 140 and 160o and eight PC substrates with roughness, 15<Rg <1159 nm, were used in this study. Two high speed CD cameras with 6770 fps were utilized for studying the relaxation of drop morphology: one for side view and the other for top view images. In the water drop impinging on graphite experiment, droplet size (1.93≤D0≤4.90 mm) and impact velocity (0.11≤Vi≤0.74 m/s) were adjusted. Bubble entrapment occurred more frequently for a more hydrophobic graphite surface. At a fixed drop size, bubble entrapment takes place only in a limited range of impact velocity. In the experiment of water drop impinging on PC substrate, drop size (2.13≤D0≤3.87 mm) and impact velocities (0.14≤Vi≤0.59 m/s) were also adjusted. Bubble entrapment took place more frequently on a rough PC substrate. At a fixed drop size, bubble entrapment was observed in one or two ranges of impact velocity. The two-range of bubble entrapment occurred more on the rough PC substrates. Beside, three new bubble formation mechanisms were observed in the water-PC substrate system.