engleski

Coolant Induced Variable Temperature Flow Field for Improved Performance of Proton Exchange Membrane Fuel Cells

Coolant induced variable temperature flow field is a novel concept for highly efficient proton exchange membrane fuel cell operation without the requirement for external humidification. The product water generated inside the cell is utilized for internal humidification of the membrane as well as the reactants, while the generated heat is utilized for establishing and maintaining the desired temperature profile along the cell, i.e. variable temperature flow field, by gradually increasing the temperature of the coolant in the cathode downstream direction. The objective of the developed concept is to maintain high membrane water content along the entire flow field without the occurrence of liquid water inside the cell at higher currents, while the concept must be at the same time feasible for stack applications and flexible to enable highly efficient operation under significantly different operating conditions. The concept is investigated via interactive combination of computational fluid dynamics modeling and experimental validation for two membrane- electrode assemblies, one with Nafion® 212 and the other with Nafion® 115 membrane, and additional calculations are also carried out for a five-cell stack with Nafion® 212 membranes. The results of the computational fluid dynamics model are compared with the experimental data and give insight in the membrane water content and membrane water flux by comparing the results of the current density and relative humidity distributions along the cell with high level of mutual agreement. The results of the study indicate that the implementation of the coolant induced variable temperature flow field results in improved performance of the cell, vs. commonly used isothermal operation, by achieving close to 100% relative humidity along the entire flow field without the requirement for external humidification and by minimizing the occurrence of liquid water inside the cell.

Proton exchange membrane fuel cells ; operation without external humidification ; computational fluid dynamics ; variable temperature flow field ; high efficiency

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