石墨烯具有較強的附著性及較低的表面能，可在極薄（數奈米）的厚度下有效改變液-固接觸特性，克服了無法長時間運作的缺點，而且不致造成過大之熱阻，可望發展適用於沸騰及凝結熱增強。但由於石墨烯應用於兩相熱傳的時間尚短，很多機制尚未十分清楚，本計畫延續前一期計畫之研究，利用功能化石墨烯改變熱傳表面特性，以微觀尺度上汽泡成長及凝結液滴成核觀察，以及巨觀上池沸騰和鰭管外凝結熱傳性能之量測，了解液-固接觸角對沸騰及凝結熱傳性能之影響，並據而推導出包含接觸角參數之沸騰及凝結熱傳經驗式。整體計畫執行期限為三年，預定完成工作項目如下： A1. 各種表面成核孔穴數量及形狀觀察 A2. 單一汽泡成長動態微觀分析 A3. 不同表面張力流體在不同表面能加熱表面上之池沸騰熱傳性能量測 A4. 汽泡成長動態觀察及其與熱傳性能關聯分析 B1. 不同表面凝結液滴成核觀察 B2. 不同表面張力流體在不同表面能鰭管上之凝結熱傳性能量測 B3. 鰭片間凝結液聚集觀察分析 B4. 鰭片間凝結液動力平衡及凝結液滴落流動穩定分析 ;Graphene has been applied for enhancing boiling heat transfer due to the fact of the extremely lower interfacial thermal resistance due to it atomic layer thickness, and the ease of adjusting the surface morphology and wettability that favorable to catalyze the vaporization on fluid/graphene interface. There are very few reports in the past years regarding the two-phase heat transfer on graphene coating surfaces. Most the detail mechanism on heat transfer enhancement is still not completely clear. This project will continue our previous related research project on the pool boiling and condensation heat transfer by applying graphene coatings. It is aimed to thoroughly understand the detailed mechanism of bubble generation and condensate drop formation on functionalized graphene coatings. This is a three-year period project. The following work packages are expected to be completed.A1. Cavities size and shape observation on functionalized graphene coating surfaces.A2. Micro scope observation of single bubble generation on functionalized graphene coating surfaces.A3. Pool boiling heat transfer performance measurement of fluids with various surface on different coating surfaces.A4. Theoretical derivation on the relation between bubble dynamics and heattransfer performance.B1. Micro scope observation of droplet formation on functionalized graphene coating surfaces.B2. Condensation heat transfer performance measurement of fluids with various surface on fin tubes with different coatings.B3. Condensate flow observation and dynamic analysis.B4. Dynamic balance analysis on the condensation flow instabilities under the effect of graphene coatings.
