When Can the Oxygen Transport Loss Be Ignored

Equation 4.167 in the dimensional form reveals that the effect of oxygen transport on the polarization curve is minimal, if the cell current density is much less than the 

The same condition was obtained in the section Low Cell Current (fo -C 1), Equation 4.85. This result is confirmed by direct numerical solution of the system (4.53) through (4.55) (Kulikovsky, 2009b). 

In the range ofe 0.1-0.5,Equation4.170 is the best approximation for the CCL polarization curve. For e 0.1, the effect of oxygen diffusion can be completely ignored and either of Equation 4.128 or 4.141 can be used. 

It is insightful to estimate the parameter e for the CCL of a PEFC and for the ACL of a DMFC. For this estimate, the oxygen transport loss in the GDL is ignored. With Cl 7.4 10 mol cm (oxygen concentration in air) and the characteristic for PEFC value of D from Table 5.9, one finds — cm . For DMFC, with the 

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