In a proton exchange membrane fuel cell (PEMFC), the water removal from the cathode to reactant flow channels is a critical aspect of cell operation. This is an active area of research to understand the transport mechanisms of water. In the available literature, it has been shown that a significant portion of the product water is removed in vapor form by the heat pipe effect through the gas diffusion layer (GDL). The intensity of the heat pipe effect is dependent on the local mean temperature and the through-plane temperature gradient across the GDL. This gradient is spatially affected by the reactant channel-land patterns of the bipolar plate (BPP) and the coolant plate operation. Therefore, the heat pipe effect can have spatial variances depending on the BPP design and cooling method.

In order to show the local temperature and through-plane temperature gradient distribution in a GDL, a numerical approach was taken in this work using a commercially available software package, COMSOL Multiphysics® 4.2a. A repetitive cathode section of the PEMFC was modeled in 3D with domains of a GDL and BPP. In-plane thermal conductivity of the GDL was incorporated by using experimentally obtained values from the available literature. By changing the design and operating conditions of the coolant system, the thermal profile and so, the vapor flux across the GDL were investigated. It was found that the increasing temperature non-uniformity on coolant plates leads to less uniform distribution of vapor flux. This is expected to lead to more condensation of water vapor under the lands.

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