Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com 2D Convective and Diffusive Fluid Flow in Porous Reaction Regions and Flow Chambers without a Separator Membrane A Finite Element Analysis (FEA) Numerical Model Craig E. Nelson - Consultant Engineer

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Purpose of the Computational Fluid Dynamic Experiment : Investigate convecting and diffusing fluid flow in the presence of homogeneously reacting porous bounding regions..

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Model Assumptions for Computational Fluid Dynamic Experiment : 1.Fluid has a single phase - liquid 2.The Liquid is water plus low concentration reactant 1 and reactant 2 3.Homogeneous chemical reactions, in porous regions bounding the flow regions, “consume” reactants with equal and very fast reaction rates.

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Reactant 1 Reactant 2 Geometry for “inside out” flow with laminar flow reactant cross- over prevention

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Typical Pressure Distribution

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Typical Horizontally Directed Velocity Distribution

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com To perform the numerical experiment, we vary the inlet port pressure from essentially zero up to some relatively high value. We then observe the resultant reactant concentration distribution within the different parts of the solution domain.

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Order of magnitude: 1e-3 Order of magnitude: 50e-3

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Order of magnitude: 75e-3 Order of magnitude: 1e-3

Nelson Research, Inc – N. 88 th St. Seattle, WA USA aol.com Summary of Results for Computational Experiment: 1.When flow is stagnant not much reactant crossover will occur because MeOH transport is by diffusion only … a relatively slow process. 2.Intermediate flow rates result in the highest reactant cross-over rates 3.A relatively high flow velocity will prevent most reactant crossover from occurring. The crossover that does occur will happen through diffusion across the channel to the cathode.