2.6.2 Specifying Model Parameters

You can use the Parameters tab of the Fuel Cell and Electrolysis Models dialog to specify the electrochemistry parameters for the Fuel Cell and Electrolysis Model, reference diffusivities for the reactants, among other model parameters.

Figure 2.6.3: The Parameters Tab of the Fuel Cell and Electrolysis Models Dialog

There are various parameters under Electrochemistry in the Fuel Cell and Electrolysis Models dialog. For both the anode and the cathode, you can also set the following parameters or leave the default values.

• The Ref. Current Density corresponds to $j_{\rm an}^{ref}$ and $j_{\rm cat}^{ref}$, the reference exchange current density from Equation  1.2-3 and Equation  1.2-4.

• The Ref. Concentration corresponds to the reference concentration ( $[H_2]_{\rm ref}$ and $[O_2]_{\rm ref}$) with units of 1 kgmol/m $^3$ (see Equation  1.2-3 and Equation  1.2-4).

• The Concentration Exponent corresponds to $\gamma$, the concentration dependence from Equation  1.2-3.

• The Exchange Coefficient corresponds to $\alpha$, the transfer coefficient from Equation  1.2-3.

• The Open-Circuit Voltage corresponds to $V_{\rm oc}$ in Equation  1.2-8.

• The Specific Leakage Current corresponds to $I_{\rm leak}$ in Equations  1.8-1 through 1.8-6. This is the total amount of transfer current (A $/m^3$) due to fuel oxidant cross-over (leakage through the electrolyte). When this happens, the fuel cell generates less current especially for cases with low values of fuel or air utilization. In addition to the constant value you can specify in the Electrochemistry tab, you can also specify the specific leakage current through the user-defined function Leakge_Current(). For more information, see Section  2.11.

Moreover, the following parameters can also be set here:

• The Reference Diffusivities correspond to $D_{\rm i}^{0}$ from Equation  1.6-1, the species mass diffusivity. These are not be required if the Multicomponent Diffusion option is enabled in the Model tab.

• The Saturation Exponent for Pore Blockage corresponds to $r_{\rm s}$ from Equation  1.6-1 for multiphase PEMFC calculations.