2.3 Fuel Cell Stack
Leela manohar et al. [13] studied the influences of gas pressure and flow rate parameters on fuel cell performance. The fuel cell was operated at various pressure and flow rates that were regulated by mass flow controllers placed upstream of the stack. In this study, four types of control factors considered were: pressures of the fuel and oxidant and the flow rates of the fuel and oxidant to select optimize condition for fuel cell operation. Each factor has two levels, leading to a full factorial design requiring 24 experiments leading to a 16 experiments and fractional factorial experiments, 24-1, leading to 8 experiments. The experimental data collected were analysed by statistical sensitivity analysis by checking the …show more content…
[15] developed a model to an isothermal, steady state, two-dimensional PEM fuel cell. Their results showed that the length of the gas flow channel has a significant effect on the current production of the PEM fuel cell, with a longer channel length having a lower performance relative to a shorter channel length. This lower performance was caused by a grater variation in water content within the longer channel length. Shyam Prasad and S. Jayanti et al. [16] studied the serpentine flow fields that have long been used in PEM fuel cell for effective transportation of reactants from the flow field to the reaction sites. It was observed in literature that localized flooding near the U-bend region of serpentine flow fields occurs at high current densities. This was attributed to the boundary layer separation and recirculation of flow in the U-bend. It was established using CFD simulations that it was attributed due to lower channel-to-channel cross flow in the electrodes between consecutive serpentine channel rather than to the flow field in the gas distribution channel. Xianguo Li et al. [17] developed a design procedure for flow channels on bipolar plates that can be effectively remove water …show more content…
It is noted that the above studies were performed without conducting a complete exergy analysis of the fuel cell efficiency taking into consideration all the variations of the fuel cell’s operational conditions, such as the operating pressure and temperature, cell voltage and air stoichiometric ratio in the electrochemical process. Furthermore, these analyses did not discuss the details of physical and chemical exergies of the reactants, which are oxygen and hydrogen, and products, which are water and air even though they did not determined the trends of the physical exergies of the reactants and the products against the variable operating temperature and pressure of fuel cell. Therefore, there is a strong need for conducting an exergy analysis which takes into account all the operational aspects of a fuel cell as well as the trends of the physical exergy of each reacting and producing element in the electrochemical process.
The objective of the present study is to perform an exergy analysis on a PEM fuel cell. This analysis consider both the physical and chemical exergies of all the reactants and the products if the electrochemical process of the fuel cell at various operational conditions, which are the cell operating temperature and pressure, and membrane