Visual study of CO2 bubble behavior in anode flow field of direct methanol fuel cell at ambient temperature

Abstract

This paper reports on a visual study of the CO2 bubble behavior in the anode flow field of a transparent Direct Methanol Fuel Cell (DMFC) with interdigitated flow field (IFF), working at ambient temperature. In the IFF, the quantity of CO2 bubbles increased with the increase of current densities. At low current densities, bubble flow appeared in the anode flow field and channel-blocking phenomenon caused by CO2 gas bubbles was found in the inlet channels; at moderate current densities, a number of gas slugs formed, and then bubbly flow and slug flow coexisted in the flow field; at high current densities, channel-blocking phenomenon also appeared in outlet channels. As the methanol flow rates increased, the amount of the CO2 bubbles decreased, enhancing the mass transport process of methanol and hence, improved the limiting current. However, higher methanol flow rate led to an increase of methanol crossover and to take away more heat. This eventually, resulted in a deterioration of cell performance.