Proton transport resistance correlated to liquid water content of gas diffusion layers

2012 ◽  
Vol 209 ◽  
pp. 147-151 ◽  
Author(s):  
Jon P. Owejan ◽  
Jeffrey J. Gagliardo ◽  
Robert C. Reid ◽  
Thomas A. Trabold
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Proton Transport ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Gas Diffusion Layers ◽  
Diffusion Layers

scholarly journals Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2967
Author(s):  
Adrian Mularczyk ◽  
Andreas Michalski ◽  
Michael Striednig ◽  
Robert Herrendörfer ◽  
Thomas J. Schmidt ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Liquid Water ◽  
Evaporative Cooling ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Ex Situ ◽  
Water Evaporation ◽  
Evaporative Water ◽  
Gas Diffusion Layers ◽  
Diffusion Layers

Facilitating the proper handling of water is one of the main challenges to overcome when trying to improve fuel cell performance. Specifically, enhanced removal of liquid water from the porous gas diffusion layers (GDLs) holds a lot of potential, but has proven to be non-trivial. A main contributor to this removal process is the gaseous transport of water following evaporation inside the GDL or catalyst layer domain. Vapor transport is desired over liquid removal, as the liquid water takes up pore space otherwise available for reactant gas supply to the catalytically active sites and opens up the possibility to remove the waste heat of the cell by evaporative cooling concepts. To better understand evaporative water removal from fuel cells and facilitate the evaporative cooling concept developed at the Paul Scherrer Institute, the effect of gas speed (0.5–10 m/s), temperature (30–60 °C), and evaporation domain (0.8–10 mm) on the evaporation rate of water from a GDL (TGP-H-120, 10 wt% PTFE) has been investigated using an ex situ approach, combined with X-ray tomographic microscopy. An along-the-channel model showed good agreement with the measured values and was used to extrapolate the differential approach to larger domains and to investigate parameter variations that were not covered experimentally.

Comparison of Water Thickness Profiles of Compressed PEMFC GDLs

2011 ◽  
Author(s):  
Pradyumna Challa ◽  
James Hinebaugh ◽  
A. Bazylak
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Water Distribution ◽  
Polymer Electrolyte Membrane ◽  
Water Injection ◽  
Liquid Water Content ◽  
Gas Diffusion ◽  
Injection Rate ◽  
Water Levels ◽  
Ex Situ

In this paper, through-plane liquid water distribution is analyzed for two polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs). The experiments were conducted in an ex situ flow field apparatus with 1 mm square channels at two distinct flow rates to mimic water production rates of 0.2 and 1.5 A/cm2 in a PEMFC. Synchrotron radiography, which involves high intensity monochromatic X-ray beams, was used to obtain images with a spatial and temporal resolution of 20–25 μm and 0.9 s, respectively. Freudenberg H2315 I6 exhibited significantly higher amounts of water than Toray TGP-H-090 at the instance of breakthrough, where breakthrough describes the event in which liquid water reaches the flow fields. While Freudenberg H2315 I6 exhibited a significant overall decrease in liquid water content throughout the GDL shortly after breakthrough, Toray TGP-H-090 appeared to retain breakthrough water-levels post-breakthrough. It was also observed that the amount of liquid water content in Toray TGP-H-090 (10%.wt PTFE) decreased significantly when the liquid water injection rate increased from 1 μL/min to 8 μL/min.

Development of a Method for Determining the Two-Phase Relative Permeability Relationships in the Gas Diffusion Layers of PEM Fuel Cells

2009 ◽  
Author(s):  
J. D. Sole ◽  
M. W. Ellis
Keyword(s):  
Fuel Cells ◽  
Carbon Fiber ◽  
Linear Function ◽  
Relative Permeability ◽  
Liquid Water ◽  
Gas Diffusion ◽  
Pressure Differential ◽  
Gas Diffusion Layers ◽  
Diffusion Layers ◽  
Pneumatic Cylinders

A new method is demonstrated for the simultaneous determination of both the liquid phase relative permeability and the gas phase relative permeability as a function of compression in thin porous materials such as those used as gas diffusion layers (GDLs) in proton exchange membrane fuel cells (PEMFCs). In this method, multiple layers of the material of interest are inserted into the test section and the desired compression is achieved via pneumatic cylinders. The compression of the sample is maintained while both liquid and gas are forced through the medium at a known rate until a steady pressure differential across the compressed medium is achieved. Upon achieving a steady pressure differential, the pneumatic cylinders are retracted and the center layer of the sample material is released and suspended from an analytical balance. The mass measurement yields the liquid saturation of the material, while the flow rate of each component and the common pressure drop are used to determine the relative permeability of each phase. The process is repeated at different flow rates until the dependence of the relative permeability on saturation is established. The relative permeability of liquid water in GDL materials has long been assumed to follow a cubic relationship with saturation similar to what has been observed in packed sand. However, it is shown in this work for a variety of macroporous GDL materials including both carbon fiber paper and carbon fiber cloth, that the relative permeability function is actually a linear function of liquid water saturation. The slope of the linear function is highly dependent on the substrate type, the level of wetproofing that has been applied to the substrate, and the compression of the material. Results are presented for carbon paper and carbon cloth materials that are untreated (no wetproofing) and that have been treated with a wetproofing agent to a level of 20 wt%.

scholarly journals Detachment of Liquid-Water Droplets from Gas-Diffusion Layers

2019 ◽  
Vol 41 (1) ◽  
pp. 459-468 ◽  
Author(s):  
Prodip K. Das ◽  
Adam Grippin ◽  
Adam Z. Weber
Keyword(s):  
Liquid Water ◽  
Gas Diffusion ◽  
Water Droplets ◽  
Gas Diffusion Layers ◽  
Diffusion Layers
Sign in / Sign up

Export Citation Format

Share Document