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姓名 謝献慶(Hsien-Ching Hsieh) 查詢紙本館藏 畢業系所 能源工程研究所 論文名稱 石墨烯塗佈銅管外凝結熱傳性能研究 相關論文 檔案 [Endnote RIS 格式]
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摘要(中) 本研究使用化學氣相層積法(CVD)，將石墨烯塗佈至純銅圓管表面上，使石墨烯表面產生疏水性的物理現象，並將其測試銅管置於本實驗室設計之可視化冷凝實驗系統中，透過觀察與量測工作流體R245fa 與R141b 之管外冷凝熱傳係數以及石墨烯表面的是否能產生滴狀凝結之物理現象，並比較石墨烯表面與一般銅表面管外冷凝熱傳係數之差異。
在接觸角量測結果上，去離子水在石墨烯表面接觸角有9∘的提升對於一般銅表面上，而石墨烯測試銅管在拉曼光譜儀之測量結果，在實驗前與實驗後皆有石墨烯特徵訊號，證明所選擇之工作冷媒並未與石墨烯表面產生化學反應。
而在管外冷凝熱傳係數上，一般銅管與石墨烯銅管外冷凝熱傳係數非常接近，主要原因為R141b 冷媒液體在巨觀情況下並無法呈現疏水性的液滴在石墨烯表面上，以及R245fa 冷媒在分子結構上較為對稱，使其流體極性較低與非極性的石墨烯表面產生相似相溶之化學現象，使其無法產生滴狀冷凝在石墨烯塗佈表面上。摘要(英) Condensation, a two-phase heat transfer processes, is commonly utilized in industrial systems. Water vapor condensation has been studied by several researchers and different technique has been proposed to enhance condensation heat transfer. Functionalized surfaces can enhance condensation heat transfer by means of transferring heat with dropwise condensation due to hydrophobic coatings. Many studies have investigated outside water condensation heat transfer of functionalized surface.
However, there are several applications which use refrigerant with low boiling temperature instead of water such as waste heat recovery technologies with low thermal efficiency and high capital cost. Enhancing condensation heat transfer of refrigerant can considerably increase and decrease the thermal efficiency and capital cost of these systems respectively.
Due to the lack of study on outside refrigerants condensation of heat transfer with functionalized surface, this study focuses on the effect of graphene-coated copper tube on the performance of outside condensation heat transfer. The graphene was in-situ grown cooper tube surface by chemical vapor deposition (CVD) method. In this research two different refrigerant R245fa and R141b are used. Moreover, the heat transfer efficiency of outside condensation for graphene coated and uncoated copper tubes are investigated and compared.
The contact angle of deionized water (DI-water) and R141b droplet on pristine and graphene-coated copper plate are measured. The droplet contact angle on graphene-coated and uncoated copper plate are measured to be 88.3o (DI-water)/ 23.6 o(R141b) and 79.8o(DI-water)/ 15.7 o (R141b) ,respectively.
The experimental observation and results show no drop-wise condensation and heat transfer enhancement for R245fa and R141b on graphene-coated copper tube when compare to that of uncoated tube. The results show that the experimental heat transfer coefficient at low subcooled wall temperature has no significance difference (5 %) with Nusselt correlation but at high subcooled wall temperature the difference increases to 23%. The difference of experimental data with Nusselt correlation at high wall subcooled temperature is because of the effect of vapor shear which is not considered in Nusslet correlation.
R245fa is a symmetric polarized molecular, thus lower the degree of dipole. Based on the principle of like-dissolves-like, the graphene is a non-dipole molecular, leading to hydrophilic surface when it was subjected to the contact from R245fa molecular. From the contact angle measurement by real-time macroscopy, it was found out the R141b exhibit hydrophilic type droplets on graphene surface, which was consistent with the observed phenomenon of R141b testing in chamber.關鍵字(中) ★ 石墨烯
★ 管外凝結
★ 熱傳增強
★ 滴狀冷凝
★ R245fa
★ R141b關鍵字(英) ★ Graphene
★ Outside condensation
★ Heat transfer enhancement
★ Dropwise Condensation
★ R245fa
★ R141b論文目次 摘要......................................................I
Abstract..................................................I
目 錄...................................................IV
表目錄..................................................VII
圖目錄.................................................VIII
符號說明................................................XII
第一章 前言...............................................1
1.1 研究背景與動機........................................5
1.2 研究目的..............................................6
第二章 文獻回顧...........................................7
2.1 石墨烯................................................7
2.2 化學氣相沉積法........................................9
2.3 凝結熱傳機構.........................................11
2.4 石墨烯表面鍍層對滴狀冷凝之影響.......................14
2.5 結語.................................................18
第三章 實驗方法..........................................34
3.1 石墨烯製程方法.......................................34
3.2 實驗系統.............................................35
3.2.1 還路系統.........................................35
3.2.2 加熱系統.........................................35
3.2.3 冷卻水系統.......................................36
3.2.4 測試腔體.........................................36
3.3 實驗參數.............................................37
3.4 實驗數據擷取系統.....................................44
3.4.1 溫度量測.........................................44
3.4.2 壓力量測.........................................45
3.4.3 流量量測.........................................45
3.4.4 量測項目擷取.....................................45
3.4.5 冷凝液滴成長影像擷取.............................46
3.4.6 接觸角量測儀與拉曼光譜檢測裝置與原理.............46
3.5 實驗方法.............................................51
3.5.1 系統測漏.........................................51
3.5.2 系統不凝結氣體排除...............................51
3.5.3 系統內冷媒填充...................................52
3.5.4 實驗操作步驟.....................................53
3.6 實驗數據換算.........................................56
3.6.1 冷媒熱力物理性質.................................56
3.6.2 測試銅管內熱傳量計算.............................56
3.6.3 冷卻水熱傳量計算.................................58
3.6.4 冷凝熱傳係數與銅管表面過冷溫度計算...............60
第四章 實驗結果與討論....................................63
4.1 石墨烯表面拉曼光譜檢測與冷媒接觸角之量測.............63
4.2 一般銅管外冷凝熱傳係數...............................80
4.3 石墨烯表面與一般銅管表面冷凝熱傳係數之比較...........83
第五章 結論..............................................90
參考文獻.................................................92
附錄 A 實驗誤差分析.......................................94
附錄 B 各儀器校正曲線.....................................97參考文獻 [1] S. Vemuri, K.J. Kim, B.D. Wood, S. Govindaraju, T.W. Bell . “ Long term testing for dropwise condensation using self-assembled monolayer coatings of n-octadecyl mercaptan . ”Applied Thermal Engineering, 26, 421–429, 2006
[2] D.J. Preston, D.L. Mafra, N. Miljkovic, J. Kong, E.N. Wang.“ Scalable Graphene Coatings for Enhanced Condensation Heat Transfer”, Nano Letter., 15, 2902−2909, 2015
[3] Graphene mining webpage. “Understanding the Advantages and Challenges of Graphene Oxide Using Thermodynamics”, 2013
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[8] A.T. Paxson, J.L. Yagüe, K.K. Gleason, K.K. Varanasi, “ Stable Dropwise Condensation for Enhancing Heat Transfer via the Initiated Chemical Vapor Deposition (iCVD) of Grafted Polymer Films. ”, Advanced Materials, 26, 2013
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[12] A.C. Ferrari, “Raman spectroscopy of graphene and graphite: Disorder, electron–phonon coupling, doping and nonadiabatic effects” , Solid State Communications, 143, 47–57, 2007
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[14] F.P. Incropera and D.P. DeWitt, “Fundamentals of Heat Mass Transfer”, 4th ed., John Wiley & Sons, New York, 1996
[15] C.W. Meyer, G. Morrlson, “Dipole Moments of Seven Refrigerants”, Journal of Chemlcal and Englneerlng Data, Vol. 36, No. 4, 1991,指導教授 楊建裕(Chien-Yuh Yang) 審核日期 2016-12-27 推文 plurk
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