本研究設計一應用於重組式甲醇燃料電池的微型蒸發器，旨在提供重組器穩定且氣化完全的燃料來源。為了解決一般重組器會遇到甲醇蒸氣與氧氣混合不均勻之問題，本研究事先將過氧化氫與甲醇進行混合，並探討其混合比例在微型蒸發器產生的沸騰熱傳現象，藉由調整過氧化氫與甲醇混合比例達到參數最佳化。
本微型蒸發器整體大小為2 cm 2 cm，採用前方1/3長度V型結構，提供均勻的流量分佈，並結合漸擴角度0.55°之漸擴流道，後段2/3局部加熱進行測試，比較四種不同工作流體的沸騰現象，分別為99.9%甲醇溶液與三種過氧化氫與甲醇體積比值C為1/2、1/3、1/4的混合溶液，並在0.18 ml/min、0.36 ml/min、0.54 ml/min三種流量下探討流量效應對熱傳性質的影響。
研究結果顯示，隨著流量增加，熱傳遞係數、臨界熱通率、熱傳效率，皆會增加，流量0.54 ml/min時，濃度C=1/3有最高熱傳效率69.1%與熱傳係數2048 W/m2K，其中臨界熱通率增益比例與流量成正比。添加過氧化氫能提升甲醇臨界熱通率，流量0.36 ml/min時臨界熱通率增益達最佳化，濃度C=1/2混合溶液相較於純甲醇溶液，臨界熱通率增益達138%，濃度C=1/2的混合溶液在流量0.54 ml/min時有最高的臨界熱通率196.3 kW/m2。因過氧化氫在高溫時會自行分解出氧氣，在濃度C=1/2的混合溶液，流量0.36 ml/min的情況下，其在加熱功率8W-14W出現週期性壁溫與出入口壓差震盪，雙相不穩定現象嚴重。
關鍵字:蒸發器、過氧化氫、甲醇、微流道、雙相流、重組式甲醇燃料電池

The study investigates the boiling heat transfer and two-phase flow phenomena in a micro-evaporator with local heating for the diverging microchannels only. The micro-evaporator with a dimension of 2cm 2cm is composed of V-shaped micro diffusers for the entrance region to provide uniform flow distribution and parallel diverging channels with diverging angle of 0.55 degrees and 2/3 of the total length. In order to provide uniform mixture of methanol vapor, water vapor and oxygen to the reformer, the present study mixes the 50% hydrogen peroxide and methanol as the working fluid in the micro-evaporator. In the experiment, we compared the boiling heat transfer phenomenon of methanol and three mixtures of 50% hydrogen peroxide and methanol with volume ratio(C) of 1/2, 1/3, 1/4 with three flow rate, 0.18ml/min, 0.36ml/min, and 0.54ml/min.
The experimental results indicate that the addition of hydrogen peroxide can significantly enhance boiling heat transfer as well as the critical heat flux. In the case of C=1/2 and flow rate of 0.54ml/min, the critical heat flux is 196.3 kW/m2. With the increase of the flow rate, critical heat flux, heat transfer coefficient and heat transfer efficiency are promoted. The addition of hydrogen peroxide may also result in severe two phase flow boiling instability, i.e., pressure drop and wall temperature oscillations occurs: this is most severe for the case of C=1/2 and flow rate of 0.36ml/min. Based on the results of this study, the mixture with C=1/3 showing the best heat transfer coefficient may be the optimized working fluid for a micro-evaporator to serve the purpose of this study.

Key words: Hydrogen Peroxide、Evaporator、Microchannel、Two-Phase Flow、Reformed Methanol Fuel Cell

[1] International Energy Outlook 2016, U.S. Energy Information Administration, 2016.
[2] BP Statistical Review of World Energy 2016, BP p.l.c., 2016.
[3] Fuel cells ruel alternative energy options, Energy design resources, 2013.
[4] A. Arico, S. Srinivasan, V. Antonucci, DMFCs: from fundamental aspects to technology development, Fuel cells, 1(2) (2001) 133-161.
[5] J. Morse, R. Upadhye, R. Graff, C. Spadaccini, H. Park, E. Hart, A MEMS-based reformed methanol fuel cell for portable power, Journal of Micromechanics and Microengineering, 17(9) (2007) S237.
[6] 微型燃料電池新選擇——RMFC, in, 經濟部能源局網站, 2006.
[7] 黃鎮江, 燃料電池, 全華科技圖書股份有限公司, 2005.
[8] P.C. Lee, C. Pan, Boiling heat transfer and two-phase flow of water in a single shallow microchannel with a uniform or diverging cross section, Journal of Micromechanics and microengineering, 18(2) (2007) 025005.
[9] C.T. Lu, C. Pan, Stabilization of flow boiling in microchannel heat sinks with a diverging cross-section design, Journal of Micromechanics and microengineering, 18(7) (2008) 075035.
[10] C.T. Lu, C. Pan, A highly stable microchannel heat sink for convective boiling, Journal of Micromechanics and microengineering, 19(5) (2009) 055013.
[11] C.T. Lu, C. Pan, Convective boiling in a parallel microchannel heat sink with a diverging cross section and artificial nucleation sites, Experimental Thermal and Fluid Science, 35(5) (2011) 810-815.
[12] C. Choi, J.S. Shin, D.I. Yu, M.H. Kim, Flow boiling behaviors in hydrophilic and hydrophobic microchannels, Experimental Thermal and Fluid Science, 35(5) (2011) 816-824.
[13] Y. Lim, S. Yu, N. Nguyen, Flow visualization and heat transfer characteristics of gas–liquid two-phase flow in microtube under constant heat flux at wall, International Journal of Heat and Mass Transfer, 56(1) (2013) 350-359.
[14] A. Asthana, I. Zinovik, C. Weinmueller, D. Poulikakos, Significant Nusselt number increase in microchannels with a segmented flow of two immiscible liquids: An experimental study, International Journal of Heat and Mass Transfer, 54(7) (2011) 1456-1464.
[15] P. Lin, B. Fu, C. Pan, Critical heat flux on flow boiling of methanol–water mixtures in a diverging microchannel with artificial cavities, International Journal of Heat and Mass Transfer, 54(15) (2011) 3156-3166.
[16] X. Peng, G. Peterson, Forced convection heat transfer of single-phase binary mixtures through microchannels, Experimental Thermal and fluid science, 12(1) (1996) 98-104.
[17] 林家銘, 過氧化氫不相容性熱分析, 國立雲林科技大學環境與安全衛生工程研究所碩士班, 2006.
[18] M. Bernier, An experimental investigation of heat transfer to hydrogen peroxide in microtubes, Massachusetts Institute of Technology, 2004.
[19] T. Kim, J.S. Hwang, S. Kwon, A MEMS methanol reformer heated by decomposition of hydrogen peroxide, Lab on a Chip, 7(7) (2007) 835-841.
[20] B. Park, S. Kwon, Compact design of oxidative steam reforming of methanol assisted by blending hydrogen peroxide, International Journal of Hydrogen Energy, 40(37) (2015) 12697-12704.
[21] E. Lennon, A. Burke, M. Ocampo, R. Besser, Microscale packed bed reactor for controlled hydrogen peroxide decomposition as a fuel cell oxidant aboard unmanned undersea vehicles, Journal of Power Sources, 195(1) (2010) 299-306.
[22] 傅詩貽, 積體化毛細管與微漸擴流道進料腔之甲醇微型重組器, 國立清華大學工程與系統科學系碩士論文, 2014.
[23] 涂妙華, 入口設計與局部加熱對微型甲醇蒸發器效能之影響, 國立清華大學工程與系統科學系碩士論文, 2015.
[24] 積體電路產業: 黃光微影技術(Photo lithography), in, 科技台灣網, 2012.
[25] Semiconductor Manufacturing: Etch System, in, Hitachi high technologies global.
[26] E. Gulari, J.C. Brown, Catalytic production of hydrogen gas by methanol reforming, Ann Arbor Journal, 1001 (2002) 48109.
[27] 許昶逸, 甲醇雙氧水混合蒸發器應用於後端甲醇重組反應, 國立清華大學工程與系統科學系碩士論文, 2016.
[28] H.-Y. Tang, J. Greenwood, P. Erickson, Modeling of a fixed-bed copper-based catalyst for reforming methanol: Steam and autothermal reformation, International Journal of Hydrogen Energy, 40(25) (2015) 8034-8050.
[29] Hydrogen Peroxide Thermodynamic Properties, in, USP Technologies.
[30] P.A. Giguère, B. Morissette, A. Olmos, O. Knop, HYDROGEN PEROXIDE AND ITS ANALOGUES: VII. CALORIMETRIC PROPERTIES OF THE SYSTEMS H2O–H2O2 AND D2O–D2O2, Canadian Journal of Chemistry, 33(5) (1955) 804-820.
[31] J.P. Holman, Experimental methods for engineers, 2001.