Simultaneous direct visualisation of liquid water in the cathode and anode serpentine flow channels of proton exchange membrane (PEM) fuel cells

Abstract

Water flooding is detrimental to the performance of the proton exchange membrane fuel cell (PEMFC) and therefore it has to be addressed. To better understand how liquid water affects the fuel cell performance, direct visualisation of liquid water in the flow channels of a transparent PEMFC is performed under different operating conditions. Two high-resolution digital cameras were simultaneously used for recording and capturing the images at the anode and cathode flow channels. A new parameter extracted from the captured images, namely the wetted bend ratio, has been introduced as an indicator of the amount of liquid water present at the flow channel. This parameter, along with another previously used parameter (wetted area ratio), has been used to explain the variation in the fuel cell performance as the operating conditions of flow rates, operating pressure and relative humidity change. The results have shown that, except for hydrogen flow rate, the wetted bend ratio strongly linked to the operating condition of the fuel cell; namely: the wetted bend ratio was found to increase with decreasing air flow rate, increasing operating pressure and increasing relative humidity. Also, the status of liquid water at the anode was found to be similar to that at the cathode for most of the cases and therefore the water dynamics at the anode side can also be used to explain the relationships between the fuel cell performance and the investigated operating conditions.