| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 100 === Fuel cells operated at high temperature provide two main advantages as compared with their low-temperature counterparts: no water management problem and high carbon monoxide poison resistance at the anode. In this study, a two-dimensional model was developed to study the performance of fuel cell operated at temperature in the ranges of 120 to 190℃ using phosphoric acid doped polyberzimidazole (PBI) membrane. Coupled mass conservation, fluid flow, species transport, and charge conservation were solved numerically. An agglomerate model was used to describe the detail electrochemical reaction inside the catalyst layer. All the major transport phenomena were taken into account. Effects of the operation parameters such as temperature, reference current density, acid doping level, water content in acid solution, effective agglomerate surface area, agglomerate size, and volumetric heat transfer coefficient between solid and gaseous phases on the fuel cell performance in terms of current-density and current power output curves were examined in detail.
Based on the simulated results, it was found that better fuel cell performance can be obtained using high doping level of the acid solution, high effective agglomerate surface area and high anode reference current density. However, the concentration polarization on the cell output becomes more effective under these circumstances. The results also indicated that increasing the heat transfer between the solid and gas phases can improve cell output which suggested that the cell operated with high reactant flow rates would be preferred. In contrast to these parameters, water content in the acid solution and agglomerate size produce insignificant effect on the cell performance.
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