Abstract
Heat transport is an important, though often neglected function of gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells. Thermal conductivity is a key property, especially in partially water saturated GDLs and when the phase change of water is considered, such as required for evaporative cooling applications. Continuum models require effective transport properties as input, which in this work were determined for different types of dry and partially saturated commercial GDLs (Toray 060 and 120, Freudenberg H23). Three-dimensional microstructures and phase distributions were recorded using X-ray tomographic microscopy, digitalized and used in direct pore-level simulations. The governing energy conservation equation was solved in the three phases (gas, liquid, solid) with interfacial heat transfer between the phases to determine the effective thermal conductivity. Correlations for through-plane effective thermal conductivity in the different GDL types as a function of saturation are provided. An energy sink term, accounting for the evaporation of water, was added, enabling a quantification of the effective conductive heat transfer in GDLs with evaporative cooling. The water distribution (clustered or layered) in the GDLs was found to be a key factor for the thermal conduction and evaporative cooling ability.
Highlights
IntroductionThe heat transport properties of these porous materials largely depend on their morphology [2] and, when considering phase change in partially saturated structures, the water distribution [3]
Polymer electrolyte membrane fuel cells (PEMFCs) are a promising technology to address challenges of a future ce AcPreprint submitted to (***)January 5, 2022 https://mc04.manuscriptcentral.com/jes-ecs for the porous gas diffusion layer (GDL) materials connecting the source of heat in the cathode catalyst layer to the cri pt solid cell structure of the bipolar plates
Dry and partially saturated commercial GDLs (Toray 060 and 120, Freudenberg H2315I6) used in PEMFCs were analyzed for their conductive heat transfer and characterized by the calculation of effective thermal conductivities
Summary
The heat transport properties of these porous materials largely depend on their morphology [2] and, when considering phase change in partially saturated structures, the water distribution [3]. The effective thermal conductivity is a measure of the contribution of each phase to the thermal conductivity of the GDL. This property is highly sensitive to the material and distribution of different phases in the GDL. A number of studies report on approaches to experimentally measure the effective thermal conductivity of dry us GDLs [4], [5], [6], [7], [8], [9], [10], [11]. Ramousse et al [4] experimentally measured the through-plane thermal
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