(173e) Effect of Flow Characteristics and Temperature on Performance and Efficiency of a Direct Methanol Fuel Cell Stack

A direct methanol fuel cell(DMFC)system consisting of 40 single cells is assembled to study the influence of the transport phenomena on power output and stack efficiency. Concentration, temperature and flow rate of methanol which determine the stack efficiency have been investigated. The flow rate, pressure and temperature of air pumped into the cathode greatly influence the electrochemistry reaction and transport phenomena which include the mass transfer and momentum transfer. The relationships between reaction and these phenomena are studied and discussed in details. The stack efficiency is calculated by measuring the CO2 amounts at the anode and cathode outlets. In addition, equivalent ?carbon-flow current? is defined. Based on the experimental study and analysis, the following conclusions have been drawn. The methanol crossover and the interior circuit in the stack contribute to fuel loss and low efficiency. Low fuel flow-rates and low methanol concentrations provide high fuel efficiencies. However, the poor mass transport limits achieving useful power densities and high fuel efficiencies.

Keywords: direct methanol fuel cells (DMFC), balance of plant, transport phenomena, operation efficiency.