(Received 9 December 2014; accepted 9 March 2015)
Published Online: 2015
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The electrochemical impedance spectroscopy (EIS) method is an authoritative, prompt, and precise non-destructive practice. EIS is often used to understand the interfacial manners in electrochemical systems and for performance optimization, failure mode diagnosis, revealing dynamic properties, and for obtaining information on individual losses in solid oxide fuel cells (SOFCs) with measuring the current response of a fuel cell to a small sinusoidal perturbation in voltage. The difference in frequency response makes it possible to distinguish procedures and mechanisms in the electrochemical phenomenon that are happening at electrode shells. The purpose of the current study was to present modeling and simulation of the transient impedance of SOFC anodes caused by gas-phase transport processes with thermal radiation effects when a periodic variation of over potential is imposed. This model fully coupled electrochemical kinetics with gas phase diffusion. The electrochemistry at the anode was modeled using the Butler–Volmer equation, and the gas diffusion model was based on the species equations of Maxwell–Stefan. SOFCs are energy conversion devices that produce electricity and heat directly from fuel by electrochemical reaction. For evaluating the performance of SOFCs, efforts were devoted to developing numerical analysis tools capable of investigating the transport and electrochemical phenomena within the passageways of fuel cells. A simulation study was also carried out by changing parameters, such as temperature and the cell dimensions, and the results were discussed. The diameter of the impedance semicircle in Nyquist plot changes with flow field properties; hence the gas phase transport curb acting as a significant character in SOFC performance. This impedance feature is related to concentration polarization. The results were in qualitatively good agreement with experimental data. Finally, results showed that the considered thermal radiation effects increase the gas diffusion capacitance and decrease the pressure, density, H2 concentrations, and cell current.
Abdollahzadeh Jamalabadi, M. Y.
Chabahar Maritime Univ., Chabahar,
Stock #: MPC20140062