Detection of liquid water in the flow channels of PEM fuel cell using an optical sensor

•A method for liquid water detection using an optical temperature sensor was successfully developed.•A method of quantifying the detected liquid was developed by an observed time fraction value.•A relationship between local liquid water formation and temperature was also observed.

An optical sensor was developed with the capability of detecting liquid water in the flow channels of a proton exchange membrane fuel cell (PEMFC) as well as simultaneously measuring temperature. This work is an extension of previous research in which an optical temperature sensor was developed for measuring the in situ temperature of PEM fuel cells based on the principles of phosphor thermometry. The optical sensor was installed in the cathode flow channel of a 5 cm2 proton exchange membrane fuel cell. The fuel cell was tested under both dry and humid conditions. Liquid water formation in the flow channels was quantitatively measured from the experimental data. An observed time fraction value was estimated for characterizing flow channel flooding. The observed time fraction of liquid water in the flow channel was found to be closely related to the relative humidity of reactants and the operating current of the fuel cell.