Effect of stoichiometry ratio on direct methanol fuel cell performance

A three-dimensional CFD simulation of direct methanol fuel cell (DMFC) is presented. The governing equations include conservations of mass, momentum, energy and species as well as electrochemical reactions kinetics. Proper source terms are added in porous medium and the Darcy’s equation is considered in catalyst and gas diffusion layers (GDL). Flow is assumed to be laminar, steady and fully developed at channel exit and the walls are adiabatic. An in-house CFD code based on the SIMPLE algorithm is developed to solve the governing equations. The power law and central difference algorithms are used for the discretization of convective and diffusive terms, respectively. A smooth and orthogonal grid with proper stretch is implemented. The simulation results are validated against available experimental data. A series of case studies are conducted to investigate effects of stoichiometry ratio at different operating pressures and temperatures on the polarization curve. It is concluded that increasing the anode inlet stoichiometry ratio from 1.5 to 2 causes an increase of current density at low cell voltage.

Keywords:

Direct Methanol Fuel Cell , CFD , Polarization Curve Vapor Feed , Stoichiometry