Isfahan Engineering Research Center

Eşfahān, Iran

Isfahan Engineering Research Center

Eşfahān, Iran

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Asghari S.,Isfahan Engineering Research Center | Mokmeli A.,Isfahan Engineering Research Center | Samavati M.,Isfahan Engineering Research Center
International Journal of Hydrogen Energy | Year: 2010

Electrochemical impedance spectroscopy is a suitable and powerful diagnostic testing method for fuel cells because it is non-destructive and provides useful information about fuel cell performance and its components. This paper presents the diagnostic testing results of a 120 W single cell and a 480 W PEM fuel cell short stack by electrochemical impedance spectroscopy. The effects of clamping torque, non-uniform assembly pressure and operating temperature on the single cell impedance spectrum were studied. Optimal clamping torque of the single cell was determined by inspection of variations of high frequency and mass transport resistances with the clamping torque. The results of the electrochemical impedance analysis show that the non-uniform assembly pressure can deteriorate the fuel cell performance by increasing the ohmic resistance and the mass transport limitation. Break-in procedure of the short stack was monitored and it is indicated that the ohmic resistance as well as the charge transfer resistance decrease to specified values as the break-in process proceeds. The effect of output current on the impedance plots of the short stack was also investigated. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Asghari S.,Isfahan Engineering Research Center | Shahsamandi M.H.,Isfahan Engineering Research Center | Ashraf Khorasani M.R.,Isfahan Engineering Research Center
International Journal of Hydrogen Energy | Year: 2010

End plate is one of the main components of the proton exchange membrane (PEM) fuel cells. The major role of the end plate is providing uniform pressure distribution between various components of the fuel cell (bipolar plates, etc.) and consequently reducing contact resistance between them. In this study a procedure for design of end plate has been developed. At first a suitable material was selected using various criteria. Then a finite element (FE) analysis was accomplished to analyze end plate deflections and get its optimized thickness. After fabricating the end plates, a single cell was assembled and electrochemical impedance spectroscopy (EIS) tests were carried out to ensure their good operation. A 5 kW fuel cell assembled with these end plates was tested at different operating conditions. The test results show an appropriate assembly pressure distribution inside the stack which indicates good performance of the designed end plates. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Mokmeli A.,Isfahan Engineering Research Center | Asghari S.,Isfahan Engineering Research Center
International Journal of Hydrogen Energy | Year: 2010

The anode purge is a crucial process for the fuel cell long time operation because when the hydrogen is supplied in a circulation mode, any impurities present in hydrogen will gradually accumulate which lead to output voltage loss. A mathematical model is proposed for the purge process based on some operational purge parameters. The governing equations are solved and the effect of purge process on the stack working parameters is analyzed. Purge operational parameters are determined in such a way that the minimum pressure fluctuations in the anode compartment and a compromise between the minimum voltage loss and minimum hydrogen waste are achieved. A semi-stable condition is introduced and indicated that the behavior of voltage loss and hydrogen waste at this condition with respect to purge stop time (duration which the purge valve is closed) is semi-logarithmic. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

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