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Feeding vaporized methanol to the direct methanol fuel cell (DMFC) helps reduce the effects of methanol crossover (MCO) and facilitates the use of high-concentration or neat methanol so as to enhance the energy density of the fuel cell system. This paper reports a novel system design coupling a catalytic combustor with a vapor-feed air-breathing DMFC. The combustor functions as an assistant heat provider to help transform the liquid methanol into vapor phase. The feasibility of this method is experimentally validated. Compared with the traditional electric heating mode, the operation based on this catalytic combustor results in a higher cell performance. Results indicate that the values of methanol concentration and methanol vapor chamber (MVC) temperature both have direct effects on the cell performance, which should be well optimized. As for the operation of the catalytic combustor, it is necessary to optimize the number of capillary wicks and also catalyst loading. In order to fast trigger the combustion reaction, an optimal oxygen feed rate (OFR) must be used. The required amount of oxygen to sustain the reaction can be far lower than that for methanol ignition in the starting stage.

Direct methanol fuel cells are a potential candidate to replace traditional power sources for portable applications. The flow field design, manufacture, and optimization are of great significance to the cell performance. When the scale of flow channels decreases to the level of submillimeter‐scale, it is favourable to the reactant and product management. This paper focuses on the effectiveness of using a multi‐tooth planing technique to create submillimeter‐scale parallel channels in a graphite sheet. Besides the structural parameters of flow channels, a series of operating parameters are experimentally investigated, including methanol concentration, methanol feed rate, oxygen feed rate, cathode backpressure, and environmental temperature. Results indicate that the prepared channels promote a higher cell performance than the traditional design with a larger scale. It is beneficial to both the anode and cathode performances, but it has a more prominent effect at the anode. The methanol concentration of 4 mol/L yields the best performance. Using a relatively lower methanol feed rate below 0.5 mL/min has a more obvious effect on the fuel cell. The cell performance is insensitive to the change of cathode oxygen feed rate and backpressure especially when the oxygen can be sufficiently supplied. In this case we can use lower levels of oxygen feed rate and cathode backpressure. The cell temperatures and influence of environmental temperature are also discussed.

Abstract-Visualization study of two-phase flow in serpentine anode flow field of a liquid-feed direct methanol fuel cell (DMFC) was performed, and also the internal temperature characteristics of the flow in the DMFC have been studied in order to investigate the effect of important operating parameters. The results show that the two-phase flow behavior in the serpentine anode flow field with different flow rate of methanol solution is similar to each other. It was a similar periodical repetition of a process of bubble formation, detachment and coalescence to gas slug in the serpentine flow field. The flow rate of methanol solution can influence the mass transport of methanol and the internal temperature in the flow channel. On one hand, an increase in flow rate will lead to an increase in the gas bubble removal rate, which can increase the fuel cell performance. On the other hand, the increased flow rate of methanol solution will also take more heat of reaction away and reduce the temperature in the flow channel, which will degrade the fuel cell performance.