Estimation of the effective water diffusion coefficient in Nafion® membrane by water balance measurements

Abstract

AbstractParameters estimation is important in fuel cell modelling and it remains a challenging task to predict. One of the most discussed parameters is the water diffusion coefficient in Nafion® membrane, which has a huge variation (10−9 and 10−5 cm2 s−1), based upon the viewpoints of different authors. In this article, the estimation of the effective water diffusion coefficient through water balance method is presented and the effects of relative humidity gradient and cell temperature are explained. The membrane used in this work is Nafion® NRE 211 tested at a temperature of 60°C and 70°C with air flows. The value of water flux passing through the membrane is used to calculate the effective diffusion coefficient. A value in the range of 1 × 10−7 to 4 × 10−7 cm2 s−1 is reported and it shows that the water balance method can be applied easily to measure an effective membrane water diffusion coefficient.