Diffusion-Reaction-Conduction Processes in Porous Electrodes: The Electrolyte Wedge Problem

This work studies mathematical issues associated with steady-state modelling of diffusion-reaction-conduction processes in an electrolyte wedge (meniscus corner) of a current-producing porous electrode. The discussion is applicable to various electrodes where the rate-determining reaction occurs at the electrolyte-solid interface; molten carbonate fuel cell cathodes are used as a specific example. New modelling in terms of component potentials (linear combinations of electrochemical potentials) is shown to be consistent with tradition concentration modelling. The current density is proved to be finite, and asymptotic expressions for both current density and total current are derived for sufficiently small contact angles. Finally, numerical and asymptotic examples are presented to illustrate the strengths and weaknesses of these expressions

Laboratory and theoretical studies of baroclinic processes

An understanding is being developed for processes which may be important in the atmosphere, and the definition and analysis of baroclinic experiments utilizing the geophysical fluid flow cells (GFFC) apparatus in microgravity space flights. Included are studies using numerical codes, theoretical models, and terrestrial laboratory experiments. The numerical modeling is performed in three stages: calculation of steady axisymmetric flow, calculation of fastest-growing linear eigenmodes, and nonlinear effects (first, wave-mean flow interactions, then wave-wave interactions). The code can accommodate cylindrical, spherical, or channel geometry. It uses finite differences in the vertical and meridional directions, and is spectral in the azimuthal. The theoretical work was mostly in the area of effects of topography upon the baroclinic instability problem. The laboratory experiments are performed in a cylindrical annulus which has a temperture gradient imposed upon the lower surface and an approximately isothermal outer wall, with the upper and inner surfaces being nominally thermally insulating

Analysis for a Molten Carbonate Fuel Cell

In this paper we analyze a planar model for a molten carbonate electrode of a fuel cell. The model consists of two coupled second-order ordinary differential equations, one for the concentration of the reactant gas and one for the potential. Restricting ourselves to the case of a positive reaction order in the Butler-Volmer equation, we consider existence, uniqueness, various monotonicity properties, and an explicit approximate solution for the model. We also present an iteration scheme to obtain solutions, and we conclude with a few numerical examples. 1 Introduction. Fuel Cells convert chemical energy in gases such as H 2 , CH 4 and O 2 into electrical energy through electrochemical reactions. These cells tend to be highly efficient and are thus attractive ecological alternatives for generating electrical power. The electrodes in a typical fuel cell (the anode and the cathode) have a porous structure to obtain a large reactive area per unit of geometric area and hence a high current..