透過您的圖書館登入
IP:54.234.136.147
  • 學位論文

一種估算直接甲醇燃料電池之甲醇濃度之方法

A Method of Evaluating Concentration of Methanol for the Direct Methanol Fuel Cell

指導教授 : 蘇春熺

摘要


本研究主要估算直接甲醇燃料電池(DMFC)之甲醇濃度,陽極流道為蛇形流道,藉由排水集氣法蒐集反應過程中之二氧化碳(CO2)氣泡體積,利用氧化反應之電化學式來估算甲醇濃度,並透過拉曼光譜及紫外光-可見光(UV-Vis)光譜檢測驗證估算甲醇濃度之準確性。由於在蒐集CO2氣泡過程中,氣泡可能會溶解於甲醇水溶液中,因此,利用最小平方法以曲面擬合方式找出不同溫度及壓力下,CO2氣泡在不同甲醇濃度之甲醇水溶液中溶解度之曲面方程式,藉由此方程式得知溶解於甲醇水溶液中之CO2氣泡體積。除此之外,本研究之DMFC是以螺栓將電池組裝起來,因此,電池結構可能會因為螺栓壓力而造成變形,導致在蒐集氣泡過程中,氣泡可能會由電池結構縫隙排出而造成誤差,所以,本研究藉由有限元素分析以暫態方式模擬八支螺栓鎖緊順序對電池結構之影響,並將流道處溫度提升到50 ℃,觀察電池變形量是否有增加。藉由LabVIEWTM建立人機介面即時估算DMFC反應過程中之CO2氣泡產生量、甲醇水溶液濃度及電池溫度,並判斷CO2產生量是否會影響膜電極組(MEA)之反應面積而以幫浦排出來維持電池輸出功率。 由驗證甲醇濃度之實驗結果顯示,拉曼及UV-Vis光譜估算甲醇濃度較為準確。另外,由於在蒐集氣泡過程中存在溶解度及電池結構變形等因素,可能會導致藉由排水集氣法蒐集CO2氣泡來估算甲醇濃度之準確性較差。由模擬結果顯示,當溫度增加至50 ℃時,不鏽鋼集電板、鐵氟龍墊片和MEA接觸面之變形量則有增加的趨勢,最大變形量為0.01 mm,這可能會影響實驗準確性。在判斷CO2氣泡之體積是否會影響MEA之反應面積的實驗結果顯示,有即時排出氣泡之電池輸出功率則非常穩定,輸出之功率密度在4.9 mW•cm-2,並且功率變動的幅度不超過5 %。

並列摘要


This study mainly aims to evaluate methanol concentration of direct methanol fuel cell (DMFC), and anode flow channel is serpentine, to acquire carbon dioxide (CO2) bubbles volume during the reaction by collection of gases over water, and to evaluate methanol concentration by electrochemical formula of oxidation reaction, and verifies the accuracy of methanol concentration by Raman spectrum and UV-Vis spectrum. CO2 bubbles may dissolve in methanol solution during the gathering process of them; thus, the surface equation of solubility of CO2 bubbles in methanol solution of different concentration is found by least squares to surface fitting in different temperature and pressure and the CO2 bubbles volume that dissolved in the methanol solution is obtained by this equation. In addition, the DMFC is fabricated by bolts in this study, so that the pressure of bolts may lead to deformation of the fuel cell structure may make CO2 bubbles discharge from the chink of the cell structure during the gathering process of them to cause the inaccuracy. Consequently, the transient method of finite element analysis is used to simulate the effect of the order of eight bolts locked on the structure of the cell and whether the deformation extent of the cell increases is observed when the temperature at the flow raises to 50 ℃. Moreover, the man-machine interface, which is established by LabVIEWTM, immediately evaluates output of bubbles, concentration of methanol solution, and the temperature of the cell during the reaction in the DMFC. And whether or not the reaction area of the membrane electrode assembly (MEA) is affected by the output of CO2 is determined and output power of the cell is maintained by the discharge of pump. The research result of verifying concentration of methanol shows that the methanol concentration, which is evaluated by Raman spectrum and UV-Vis spectrum, is more accurate. In addition, solubility and deformation of the structure of the cell during gathering bubbles cause the less accuracy of evaluating concentration of methanol by Collection of gases over water. Simulation result shows that when the temperature increases to 50 ℃, the deformation content of contact surfaces of the stainless steel collector plate, Teflon gasket, and MEA tends upward. And the maximum deformation content, 0.01 mm, may make CO2 bubbles discharge from the chink of the cell structure during the gathering process of them to affect the experimental accuracy. The experimental result of determining whether or not the volume of CO2 bubbles will affect the reaction area of the MEA shows that the cell, which discharges bubbles in time, has stable output power density, 4.9 mW•cm-2, and the range of power variation is no more than 5 %.

參考文獻


[6] 黃士益,以步階電壓負載測試法分析直接甲醇燃料電池之研究,碩士論文,國立台北科技大學機電整合研究所,台北,2009。
[53] 郭書榕,具有不同電極結構之直接甲醇燃料電池的交流阻抗量測研究,碩士論文,國立台北科技大學機電整合研究所,2009。
[44] 蘇文,膝關節局部表面重建研究,碩士論文,國立中央大學機械工程學系,2008。
[16] 黃振宏,Nafion溶液成膜的物理性質與形態學研究,碩士論文,元智大學化學工程學系,桃園,2003。
[49] 徐志豪,陽極電極壓力對直接甲醇燃料電池之性能影響,碩士論文,國立臺北科技大學機電整合研究所,台北,2010。

延伸閱讀