Start-up and steady-state operation of a passive vapor-feed direct methanol fuel cell fed with pure methanol

A transient, two-dimensional, two-phase, multi-component, non-isothermal model is developed to investigate the start-up and steady-state characteristics of a fully passive, vapor-feed direct methanol fuel cell fed with pure methanol. The model considers the species, heat, charge and electrolyte-dissolved water transport in a single computational domain. During the steady-state operation, methanol loss due to evaporation from the cell to the ambient decreases with an increasing current density. Both the scale analysis and the predictions from the full numerical model reveal that the transient response time depends primarily on the cell load. At high current densities, mass consumption in the anode catalyst layer becomes dominant in the cell transient response time, whereas for the lower current densities, both the diffusive liquid transport in the anode and the mass consumption in the anode catalyst layers are predominant.

► The start-up of a vapor-feed DMFC fed with pure methanol is numerically studied.
► Scale analysis: “the transient response time is primarily a function of cell load.”
► Numerical predictions agree well with the scale analysis.
► Dominant transport mechanisms for the transient response time are addressed.