Date of download: 10/13/2017 Copyright © ASME. All rights reserved. From: A Nonisothermal PEM Fuel Cell Model Including Two Water Transport Mechanisms in the Membrane J. Fuel Cell Sci. Technol. 2008;5(1):011007-011007-16. doi:10.1115/1.2822884 Figure Legend: Layer assembly of a PEM fuel cell. Five layers of a PEM fuel cell are modeled: cathodic GDL, anodic GDL, cathodic CL, anodic CL, and membrane. The two gas channels are taken into account as boundary conditions into the model.

Date of download: 10/13/2017 Copyright © ASME. All rights reserved. From: A Nonisothermal PEM Fuel Cell Model Including Two Water Transport Mechanisms in the Membrane J. Fuel Cell Sci. Technol. 2008;5(1):011007-011007-16. doi:10.1115/1.2822884 Figure Legend: Plot of the capillary pressure as a function of the liquid water saturation pc(sw) according to the Brooks–Corey model. The GDLs are hydrophobic, and therefore the capillary pressure is negative. The intersection point with the y axis denotes the threshold pressure pd.

Date of download: 10/13/2017 Copyright © ASME. All rights reserved. From: A Nonisothermal PEM Fuel Cell Model Including Two Water Transport Mechanisms in the Membrane J. Fuel Cell Sci. Technol. 2008;5(1):011007-011007-16. doi:10.1115/1.2822884 Figure Legend: The two transport modes of water in the membrane are illustrated . (1) For λ⩽2, the membrane is nearly impermeable for water. (2) Vapor equilibrated transport mode: For 0⩽λ⩽14, a network of inverted micelles (drawn as circles) arises around the sulfonic acid groups of Nafion. Water molecules can be transported through this network by building H3O+ ions together with protons. This transport of hydrated protons through the membrane is described by the Grotthus mechanism and can be modeled macroscopically like a diffusion . (3) Liquid equilibrated transport mode: For 14⩽λ⩽22, more and more connections between the micelles are expanded to channels, which are filled with liquid water. A coherent liquid phase with well-defined hydraulic pressure is formed. The fraction of already expanded channels in a considered volume is labeled with S.

Date of download: 10/13/2017 Copyright © ASME. All rights reserved. From: A Nonisothermal PEM Fuel Cell Model Including Two Water Transport Mechanisms in the Membrane J. Fuel Cell Sci. Technol. 2008;5(1):011007-011007-16. doi:10.1115/1.2822884 Figure Legend: Coupling diagram of the PEM fuel cell model. The transport mechanisms and the solution variables (state variables) of the corresponding PDEs are written in the boxes. Each arrow indicates a coupling between two PDEs, the coupling state variables that are contained in the PDEs are noted at the arrows.

Date of download: 10/13/2017 Copyright © ASME. All rights reserved. From: A Nonisothermal PEM Fuel Cell Model Including Two Water Transport Mechanisms in the Membrane J. Fuel Cell Sci. Technol. 2008;5(1):011007-011007-16. doi:10.1115/1.2822884 Figure Legend: The model domain is shown. R1–R4 indicate boundaries between subdomains. The solid lines correspond to the outer boundaries RI–RIII.

Date of download: 10/13/2017 Copyright © ASME. All rights reserved. From: A Nonisothermal PEM Fuel Cell Model Including Two Water Transport Mechanisms in the Membrane J. Fuel Cell Sci. Technol. 2008;5(1):011007-011007-16. doi:10.1115/1.2822884 Figure Legend: The grid geometry used for simulations. The figure shows the five layers of the fuel cell.