Performance evaluation of a direct methanol fuel cell: combination of three-dimensional computational fluid dynamic modelling and one-dimensional diffusion layer mathematical modelling

In this study, to define the distribution of CO2 and methanol concentration in the anode channel, three-dimensional (3D) two-phase homogeneous computational fluid dynamics (CFD) modelling for the anode channel and one-dimensional (1D) two-phase mathematical modelling for the porous media have been considered. In the anode channel, two flow configurations, single-serpentine flow field (SSFF), and parallel flow field (PFF) were studied. Here also, the effects of inlet mass flowrate, flow configurations, inlet temperature of aqueous solution, and inlet feed concentration on the CO2 concentration in the anode channel and cell performance have been investigated. To define the interface boundary conditions between the channel and diffuser layers, the CFD modelling of the anode channel was coupled with the mathematical modelling in the porous media. The results show that the corner of the channel rib is the proper site for coalescence of CO2 gas bubbles. The finer distribution of methanol concentration and less number of gas bubbles at the SSFF configuration have been observed. This leads to a better performance of the cell in the SSFF configuration relative to the PFF configuration. With increase of the mass flowrate, the molar concentration of CO2 (gas bubbles) reduces and the cell performance improves. With increase in the temperature of aqueous methanol solution, cell performance will improve. The main reasons should be attributed to the enhanced activity of the catalyst and increase of diffusion coefficient of the methanol solution. The CO2 gas bubbles will emerge more at higher temperatures, but it is clear that the effect of enhanced activity of the catalyst and increase of the diffusion coefficient of the methanol surmounts that of numerous CO2 gas bubbles, thus leading to the improvement of the cell performance.