Study on heat and mass transport in polymer electrolyte fuel cell and optimization of fuel cell electric vehicle systems

摘要

The paper presents an overview of the author's doctoral thesis on polymer electrolyte fuel cell for vehicle use. The work concentrates on heat and mass transport in the fuel cell, together with vehicle system analysis. In the experiment several types of cells with the membrane size of 100mm square were assembled, and measurement was made on the basic effect of humidification, temperature, and thickness of the separators. Numerical simulation model was also developed and applied for the analysis of the current density and temperature distribution in the membrane. The major conclusions obtained in the research are as follow: (1) if low temperatures and low current densities are selected, dry system without humidifier is possible commercially; (2) it is difficult to start up a fuel cell at low temperature as -20°C, but increased flow rate and heating of supplied air for cathode gas is effective for warming up without frosting of the water; (3) concerning the direction of gases in a fuel cell, co-flow is superior to cross-flow in the performance of fuel cell due to more uniform distribution of current density and temperature in the membrane; (4) separator thickness with 0.6mm was examined and it showed significant increase in power density for unit volume of cell stack, although the maximum power for unit area of membrane were deteriorated in some extent.