Simulation-Assisted Determination of the Start-Up Time of a Polymer Electrolyte Fuel Cell

Fuel starvation is a major cause of anode corrosion in low temperature polymer electrolyte fuel cells. The fuel cell start-up is a critical step, as hydrogen may not yet be evenly distributed in the active area, leading to local starvation. The present work investigates the hydrogen distribution and risk for starvation during start-up and after nitrogen purge by extending an existing computational fluid dynamic model to capture transient behavior. The results of the numerical model are compared with detailed experimental analysis on a 25 cm2 triple serpentine flow field with good agreement in all aspects and a required time step size of 1 s. This is two to three orders of magnitude larger than the time steps used by other works, resulting in reasonably quick calculation times (e.g., 3 min calculation time for 1 s of experimental testing time using a 2 million element mesh).

Design and Simulation of Air-Breathing Micro Direct Methanol Fuel Cells with Different Anode Flow Fields

The design of the anode flow field is critical for yielding better performance of micro direct methanol fuel cells (µDMFCs). In this work, the effect of different flow fields on cell performance was investigated by the simulation method. Compared with grid, parallel and double-serpentine flow fields, a single-serpentine flow field can better improve the mass transfer efficiency of methanol and the emission efficiency of the carbon dioxide by-product. The opening ratio and channel length also have important effects on the cell performance. The cells were manufactured using silicon-based micro-electro-mechanical system (MEMS) technologies and tested to verify the simulation results. The experimental results show that the single-serpentine flow field represents a higher peak power density (16.83 mWcm−2) than other flow fields. Moreover, the results show that an open ratio of 47.3% and a channel length of 63.5 mm are the optimal parameters for the single-serpentine flow field.