Effective transport properties for polymer electrolyte membrane fuel cells – With a focus on the gas diffusion layer

Microstructure-property relationships in a gas diffusion layer (GDL) for Polymer Electrolyte Fuel Cells, Part I: effect of compression and anisotropy of dry GDL

“…0.521, through-plane: 0.785) for GDL type materials [5]. However, the comparison with experimental data indicates that Eqs.…”

“…In this context we are discussing in the introduction the limitations of conventional expressions for diffusivity in GDL, however bearing in mind that similar limitations can also be identified for most conventional descriptions of permeability. For an extended review of all relevant effective properties in the GDL we refer to Zamel and Li [5].…”

“…(2) and (3) using standard values for the fitting parameters both tend to overestimate the true effective diffusivity of the specific GDL materials [8]. As discussed by Zamel and Li [5], these differences arise because the expressions and the fitting parameters were deduced empirically for microstructures, which are not representative for the specific GDL of interest. A further limitation comes from the fact that these expressions only consider bulk porosity but they ignore microstructure details such as pore size distributions, bottleneck dimensions and/or variation of tortuous path lengths.…”

“…(1) (g(S)), which describes microstructure limitations due to the presence of water in partially saturated GDL. Most frequently used expressions are the Mualem-and Burdine-functions as well as the Van Genuchten and Brooks-Corey relationships [4,5,10,11]. These functions are capable to describe basic trends of diffusivity with saturation (S) and with capillary pressure (P c ), but also these relationships need to be fitted with experimental data in order to predict the transport properties of a specific GDL accurately.…”

The effects of compression on single and multiphase flow in a model polymer electrolyte membrane fuel cell gas diffusion layer

“…Figure 2 shows the unit cell with characteristic lengths. The change in important parameters are also summarised in Table 2, where ǫ is the porosity which can easily be calculated from the geometry and t is the tortuosity which is commonly related to the porosity through Archie's Law: t = ǫ −n where n is typically taken to be 0.5 when applying Brüggemann's correction to various transport properties [25].…”