Performance evaluation of dead-end anode fuel cell: Effects of purging and cooling

  • Alberto Gomez

Student thesis: Master's Thesis

Abstract

The performance of a dead-end anode polymer electrolyte membrane fuel cell (PEMFC) stack is dependent on water and gas management. This thesis aims at an experimental and numerical evaluation of the influence of the key operating parameters on the transient response of a dead-end anode PEMFC stack so as to determine the optimum purging strategy when the fuel cell is subjected to load changing conditions. Water accumulation in the anode and nitrogen crossover from the cathode to the anode lead to performance deterioration over time. The accumulated water and nitrogen need to be removed effectively by purging method to ensure good and stable stack performance. Thus, the careful selection of the operating parameters – inlet humidification, stoichiometry, and operating current – is the key factor for ensuring efficient water and gas management. These parameters are crucial in the dynamic behavior of the PEM fuel cell stack required for successful operation of fuel cell vehicle. Maintaining fast time response whilst keeping stable and high stack performance is important, especially during acceleration and deceleration. Therefore, the transient response of dead-end anode PEM fuel cell stack under real European driving cycle together with the effect of purging factors was evaluated. The experiments were carried out on a stack with 24 cells and an active catalyst area of 300 cm2. By employing a validated transient two phase numerical model of a dead-end anode PEMFC, numerical simulations were performed to yield a better and deeper understanding of local distribution of water and species, i.e., water vapor, hydrogen, nitrogen and oxygen. The results suggest that the performance deterioration over time is closely related to the choice of the operating conditions. They reveal that the anode and cathode inlet conditions become limiting factors for the stack performance. Liquid accumulation at the anode is found to be strongly related to the inlet humidification as well as to the water transportation across the membrane, whereas the cathode stoichiometry affects the nitrogen crossover. On the other hand, the effect of purging frequencies, purging period, coolant flow rate together with the effect of cathode stoichiometry for optimum performance of the fuel cell vehicle are examined with regard to the transient driving cycle performance.
Date of AwardMay 2014
Original languageAmerican English
SupervisorTariq Shamim (Supervisor)

Keywords

  • Fuel Cells; Ion-Permeable Membranes; Transient Performance.

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