Flow-through diffusion cells, cross-section

Figure 2.1 Cross-section of flow-through diffusion cell.

The 50 cathode cell has overall dimensions of approximately 180 x 60 x 50 cm with a cross-sectional area for flow of c. 1530 cm it has provision for an air-sparging system to improve mixing and promote turbulence within the electrolyte. A porous filter plate is built into the cell at the inlet in order to diffuse liquid flow through the cell to prevent localized metal accumulation on the cathodes which could lead to short circuiting. When the foam cathodes are fully loaded, they are replaced with fresh ones. In single pass operations, the cathodes nearest the inlet require most frequent replacement. The RETEC-50 cell is primarily aimed at electroplating wastes and typically operates at 400-500 A and from -2 to -6V. 

To study the effects of molecular diffusion and formation/destabilization of reaction fronts it is advised to rely on small flow-through chambers such as capillaries or cells of sheet-type cross-section [68]. These micro reactors simply provide the small-scale environment needed for such laboratory investigations. 

Springer and others were the first to use detailed, experimentally derived diffusion and electroosmotic drag coefficients of water in Nafion in a model for steady-state water profile and the resulting protonic conductivity in the membrane of an operating PEFC [87]. The distribution of water in a PEFC at steady, state (at constant current and reactant/water fluxes) was calculated in this model by considering water flow through five regions of unit cross-sectional area within the fuel cell two inlet... 

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