On Microstructural Analysis of Porous Media Existing in Fuel Cells Using the Lattice Boltzmann Method

University dissertation from Department of Energy Sciences

Abstract: This Licentiate thesis aims to gain understanding related to the fluid behavior in porous media existent in fuel cells (FCs) at microscale. In order to achieve this; the widely used methodology for solving problems in porous media has been applied, the Lattice Boltzmann Method (LBM). LBM presents several advantages to solve problems where the microstructural architecture is complex. The introductory part presents the scope of the thesis and the different parts include in the document. Different characteristics of the FCs are given, as well as the parts where the porous media are found within the FCs are presented. The mechanism of energy conversion for two selected kind of FCs is explained, and the simplified electrochemical reactions involved in such conversion are presented. The second part of the thesis corresponds to the LBM explanation and the solution of several physical problems. The simulations are carried out at different Re in order to prove the ability of LBM for solving problems at different regimes, and to get knowledge about the boundary conditions implemented. The simulation results performed in this part are basically at macroscale. Momentum equation and energy equation form part of the results obtained using the LBM. All the simulations are validated with corresponding previous studies, which show a relatively high accuracy of the method. Finally, the simulation results of the fluid behavior in porous media are presented. Both, randomly generated and a reconstructed porous domain from a real image are analyzed. Microstructure parameters such as porosity, gas-phase tortuosity and permeability are obtained after using the LBM. The results obtained are compared with previous studies, and the posibble future work is detailed in the last chapter.

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