Modeling mass and heat transfer in membrane humidifiers for polymer electrolyte membrane fuel cells

Water management is essential for the performance and durability of fuel cells in automotive applications. External membrane humidification is the preferred method for this task, as no additional energy or water supply is required. Accurate models of the water transport through the semipermeable membrane can support the design and operation of humidifiers. In this work, an analytical model is proposed that accounts for coupled mass and heat transfer, gas boundary layers, developing flows, and membrane properties at typical operating conditions. The model is validated against experimental data measured with pure Nafion (R) membranes and an experimental composite membrane. The operating conditions cover a range from 40 to 90 % for the relative humidity, from 1.5 to 2.5 bar for the pressure, and from 340 to 360 K for the temperature. Almost all of the predicted data is within +/- 30 % of the experimental values without the need for any fitting parameters. An analysis of the mass transfer resistances reveals that the membrane and boundary layer resistances both contribute significantly to the total resistance.