Tree network channels as fluid distributors constructing double-staircase polymer electrolyte fuel cells

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In this article, constructal tree-like channel networks are introduced as a fuel cell fluid distribution concept, which also optimizes the shape of polymer electrolyte fuel cells. This concept is the main contribution of the article. To perform quantitative calculations based on this concept, a one-dimensional model, accounting for oxygen consumption in the feed channel, oxygen mass transfer between the channel and the backing layer, and oxygen mass transfer through the backing layer to the catalyst layer, is used to predict the polarization curve of a so-constructed polymer electrolyte fuel cell. Pressure drop and pumping power required for the fluid circulation is estimated. Multiobjective genetic search is performed to maximize the net power density with respect to constructal parameters and operating conditions, leading to the optimized tree network. It is found that the use of tree networks instead of the traditional, nonbifurcating serpentine channels in rectangular systems can provide substantially improved cell performance due their intrinsic advantage with respect to both mass transfer and pressure drop. The resulting "double-staircase" shape of the fuel cells differs from the traditional rectangular shape while maintaining simplicity, and it is determined based on the functionality of the flow distribution system. ©2004 American Institute of Physics.