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標題: | 異質濕潤性圖案之濕潤性差異於紅銅圓管對池沸騰熱傳性能之影響 Effects of Difference in Wettability Level of Biphilic Patterns on Copper Tubes in Pool Boiling Heat Transfer |
作者: | Zong-Xun Jiang 江宗勳 |
指導教授: | 陳炳煇(Ping-Hei Chen) |
關鍵字: | 池沸騰,表面濕潤性,異質濕潤性表面,溶膠凝膠法,皮秒雷射,氣泡動態, Pool boiling,Surface wettability,Biphilic surface,Sol-gel,Picosecond laser,Bubble dynamics, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 本論文研究了超親水基底上不同濕潤性之方型圖案於紅銅圓管表面對池沸騰熱傳性能之影響。異質濕潤性表面以二氧化矽奈米塗層與低表面能溶液搭配皮秒雷射系統進行製造,共有四種不同接觸角之圖案(CA=0°–150°)在本研究中進行熱傳效能與氣泡動態之分析;2 × 2 mm2之方型圖案在圓柱表面上平均分布,且間距與數量固定在2 mm與90個。在池沸騰熱傳實驗中,去離子水為工作流體並在飽和溫度下進行實驗,且所有實驗均在大氣環境下進行操作。實驗結果顯示,最高熱通量達到了418 kW/m2,在此熱通量下擁有疏水圖案(CA=120°)之異質濕潤性表面表現出最佳之熱傳性能,與均質之純銅試塊相比,熱傳係數增強比率達到了1.16;另一方面,擁有超疏水圖案(CA=150°)之異質濕潤性表面則表現出最差之熱傳性能,熱傳係數增強比率降低至0.83。造成此種效能差異之主要原因為不同濕潤性之圖案有截然不同之氣泡行為,進而導致各個異質濕潤性表面有不同的二相熱傳表現。為了深入研究各表面之氣泡動態,本研究也透過高速攝影機研究了三個不同熱通量下各表面之成核數量、氣泡分離尺寸與氣泡分離頻率。 This study experimentally investigated pool boiling heat transfer on copper tubes for superhydrophilic surfaces with square patterns of different wettability levels. Silica-based coating, low-energy solution and the picosecond (ps) laser system were combined to fabricate the biphilic samples with different wettable patterns. The contact angle values of four types of patterns were in the range 0°–150°. The size, pitch and number of the square pattern were fixed at 2 × 2 mm2, 2 mm and 90, respectively. Deionized (DI) water was used as a working fluid. The boiling experiments were conducted under ambient conditions up to a maximum heat flux regime of 418 kW/m2 and a saturated working fluid. Compared with the homogeneous plain copper surface, the heat transfer coefficient of the biphilic surface with hydrophobic patterns was enhanced up to 1.16, whereas that with superhydrophobic patterns decreased to 0.83 at the highest evaluated heat flux (418 kW/m2) because surface wettability led to different bubble dynamics and two-phase heat transfer behaviors. Bubble dynamics, namely the nucleation sites, bubble departure diameter, and frequency on different samples, were analyzed through high-speed imaging at three intervals of heat flux. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/55217 |
DOI: | 10.6342/NTU202002127 |
全文授權: | 有償授權 |
顯示於系所單位: | 機械工程學系 |
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