García-Salaberri , Pablo A.Lang, Jack ToddChang , Hung-MingFiras, NausirShazhad, HasanZenyuk, Iryna V.2025-05-192025-05-192025-07Pablo A. García-Salaberri, Jack Todd Lang, Hung-Ming Chang, Nausir Firas, Hasan Shazhad, Iryna V. Zenyuk, Examining the mass transport resistance of porous transport layers at the rib/channel scale in polymer electrolyte membrane water electrolyzers: Modeling and design, International Journal of Heat and Mass Transfer, Volume 244, 2025, 126889, ISSN 0017-9310, https://doi.org/10.1016/j.ijheatmasstransfer.2025.1268891879-2189 (online)0017-9310 (print)https://hdl.handle.net/10115/86338This work was supported by project TED2021-131620B-C21 of the Spanish Agencia Estatal de Investigación. X-ray computed tomography experiments were performed at the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. Beamline 8.3.2 was used with the assistance of Dr. Dilworth Parkinson.The porous transport layer (PTL) plays a relevant role in the efficiency of polymer electrolyte membrane water electrolyzers (PEMWE). Extraction of good design guidelines for this porous component is necessary for efficient water/oxygen transport. In this regard, numerical modeling provides a versatile tool to examine large parameter set and determine optimal PTL conditions to be verified experimentally. Here, a hybrid model is presented to analyze two-phase transport of oxygen and water in the anode PTL of a PEMWE. Oxygen capillary transport is modeled with a multi-cluster invasion-percolation algorithm, while water convective transport is modeled with a continuum formulation that incorporates the blockage of gas saturation. The model is validated against in-operando X-ray computed tomography data of the oxygen saturation distribution at the rib/channel scale. Subsequently, a comprehensive parametric analysis is presented, considering the following variables: (𝑖) PTL slenderness ratio, (𝑖𝑖) flow-field open area fraction, (𝑖𝑖𝑖) PTL isotropy, (𝑖𝑣) PTL average pore radius, and (𝑣) PTL pore-size heterogeneity. Among other conclusions, the results show that the water transport resistance under the rib can lead to non-negligible mass transport losses at high current density. Water transport from the channel to the catalyst layer can be promoted by: (𝑖) the use of PTLs with a slenderness ratio, defined as the PTL thickness to rib half-width ratio, around 0.5, (𝑖𝑖) the increase of the flow-field open area fraction, (𝑖𝑖𝑖) the design of highly anisotropic PTLs with a relatively large pore radius between 𝑟𝑝 ∼ 10 − 40 μm, and (𝑖𝑣) increasing the homogeneity of the PTL microstructureenAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/PTLDesignModelingMass transportPore networkPEMWEArticlehttps://doi.org/10.1016/j.ijheatmasstransfer.2025.126889info:eu-repo/semantics/openAccess