Design and Performance Test of a Water-Cooled PEMFC Stack
| Autor: | Wei-FengHong, 洪偉峰 |
|---|---|
| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 There are several technical obstructions to overcome for the commercialization of PEMFCs. One of the most critical issues is the water and thermal management which has been considered a key factor to an uniform electrochemical reaction and a proper water content in the MEA. There is a considerable amount of heat while operating a stack, especially at a high current density. The waste heat could lead to dehydration of the MEA locally or globally if an improper thermal management. In this work, a 5-cell liquid-cooled PEMFC stack was designed and developed. In the beginning process of stack design, ANSYS CFX simulation is adopted. Our primary mission focuses on the investigation of stack characteristics, including stack performance and impedance analysis in terms of gas stoichiometric ratio, gas humidification, cooling water temperatures and cooling water flow rates, A cooling plate pattern with the best temperature distribution is selected according to our simulate qualitative analysis. The experiment results show that increasing the cooling water temperature significantly raising the stack performance due to an increase of the rate of electrochemical reaction. The 5-cell water-cooled PEMFC stack exhibited the best performance at a water flow rate of 2 L/min, a water temperature of 65 oC, an air stoichiometric ratio of 2.5 and a hydrogen stoichiometric ratio of 1.5. The outside temperature distribution of the stack and the temperature difference between inlet and outlet water change as the output load changes. At a water flow rate of 1 L/min, a higher temperature was observed at a position close to the 3rd and 4th cells. At this condition, the temperature difference between inlet and outlet water is about 6 oC. However, the area affected by the local high temperature can be reduced effectively by increasing the water flow rate. Increasing the stack temperature increases the Ohmic resistance, but decreases the sum of charge transfer resistance and mass transfer resistance. In addition, the phenomenon of resistance raise becomes less significant for ROhm but more significant for Rct+Rmt at a higher current. This can be attributed to more amount of generated water. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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