Bruggeman correction

The effective diffusion coefficients between the species and porous medium are assumed to follow the same scaling for appropriate reference values DiM- An alternative to the above correction that avoids the use of the tortuosity is the Bruggeman correction [22]... 

Here, we have also introduced the Bruggeman correction, Eq. (4.7). 

The threshold porosity so in the Bruggeman correction is defined by specifying a minimum water content X m with sq = e(X , ). Here X in is the minimum amount of water that must be sorbed by the membrane for the pore liquid phase to be sufficiently well connected to allow for transport through the membrane. Examining the conductivity data in Figure 4.1, it is clear that Xmin should lie somewhere between 1.5 and 2, since this is the approximate range where the conductivity bounds intersect the x-axis. 

In the catalyst layer, the effective proton conductivity of the polymer electrolyte and the effective diffusion coefficient in the pores of the catalyst layer depend on the catalyst layer structure. These properties, and were given using the Bruggeman correction factor as follows ... 

The effective species diffusivity (Df ) and eleetrical conductivity (/c ) are subject to a Bruggeman correction (Bruggeman, 1935) to aecount for the gas-induced reduction of these properties ... 

Based on the Bruggeman correction for tortuosity, the effective ionic conductivity,... 

The effective solid phase conductivity, is related to the respective active material volume fractions, eg, in the anode and cathode electrodes, which is expressed in terms of Bruggeman correction for tortuosity and often with a value... 

The second term on the right side accounts for concentration overpotential. In porous media, the conductivity is corrected by the Bruggeman relation, k= where Koo is the conductivity of the bulk electrolyte. 

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