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

• Main Authors: Chih-Kai Tsao, 曹智凱
• Other Authors: 蘇春熺
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/6zksj4

碩士 === 國立臺北科技大學 === 製造科技研究所 === 99 === 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 %.