In polymer electrolyte membrane fuel cell (PEMFC) systems, effective water management is key to enhancing both efficiency and lifespan of the system. The necessity of keeping the system optimally hydrated to improve proton conductivity, while avoiding the issue of water flooding, emphasizes the crucial role of humidification technologies. In this study, the permeation characteristics of polysulfone hollow fiber membranes for transferring water vapor from moist air were experimentally and theoretically investigated. Experiments were conducted to assess the effect of operating conditions (e.g., inlet temperature, relative humidity, and temperature differences) on the performance of the humidifier under various feed flow rates using the membrane humidifier module in a hydrogen fuel cell vehicle. Additionally, detailed theoretical analyses were undertaken to comprehend the permeation phenomena of air through the membrane, which were correlated with experimental data to validate the model (relative error of <5%). The developed model incorporates transport equations for species, mass, momentum, and energy balances across both bulk streams, taking into consideration the heat and concentration boundary layer near the membrane. Furthermore, it introduces a new dual-mode sorption model that incorporates temperature dependence into the solution-diffusion mechanism across the membrane. The performance of the humidifier in two different flow configurations, counter and parallel-flow, was compared to illustrate the spatial variations in heat and mass transfer rates. To investigate the dynamic behavior of the PEMFC system, a system model integrating of a lumped dynamic model of an air compressor, a one-dimensional dynamic model of an intercooler (i.e., heat exchanger), and a one-dimensional dynamic model of a PEMFC stack was developed, as well as a dynamic model of a membrane humidifier. To maximize stack power in a PEMFC system, using a Pareto chart and response surface methodology, the degree of influence of valuables of the membrane humidifier was determined, and optimal operating points and geometric designs of the humidifier for enhanced efficiency and PEMFC stack performance were systematically identified.
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