Investigation of Water Transport Within a Proton Exchange Membrane Fuel Cell by Diffusion Layer Saturation Analysis

Abstract

Diffusion layer saturation analysis (DLSA) is introduced in order to further investigate water transport within the cell. The analysis relies on two separate experimental processes. First, an ex-situ investigation of the relative humidity of the gas streams and their resulting pressure drop is performed. Next, multiple variables of the cathode and anode gas streams are manipulated in-situ to create an evaporative driving force to remove water out of the porous layers. Multiple gas stream settings are investigated as well as the temperature set point of the cell. The ex-situ pressure drop data is used to infer how much water is being removed from the system and to begin to estimate an overall water balance. Multiple cathode and anode GDL configurations are tested in order to further investigate initial saturation conditions of the GDLs. By coupling the voltage results to the calculated water removed from the system, it can be seen which configurations had low initial voltage due to GDL oversaturation. The potential for DLSA both as a diagnostic tool and an investigative technique into multiphase flow in the porous layer is demonstrated.

Quantifying Cathode Water Transport via Anode Relative Humidity Measurements in a Polymer Electrolyte Membrane Fuel Cell

“…The flow rate was systematically increased every two minutes, the time period required for the voltage to reach a steady state, by increasing the anode stoichiometry set point. The duration of each set point was also consistent with the previously established protocol [33,34]. The test started with the standard anode stoichiometry set point of 1.5, and the first flow rate increase was to a stoichiometric value of two.…”

“…Some efforts have been made to determine 'flooding' conditions in realistic fuel cells without the need for advanced techniques. One such protocol, Anode Water Removal (AWR), was previously shown to qualitatively identify poor cell performance due to cathode GDL flooding [33,34]. This method relies on the manipulation of an evaporative gradient created by running the fuel cell with a dry anode stream at systematically increasing flow rates.…”