In-Plane Microstructure of Gas Diffusion Layers With Different Properties for PEFC

2013 ◽  
Vol 11 (2) ◽  
Author(s):  
Mehdi Mortazavi ◽  
Kazuya Tajiri
Keyword(s):  
Contact Angle ◽  
Fuel Cell ◽  
Pore Diameter ◽  
Gas Transport ◽  
Gas Permeability ◽  
Transport Phenomena ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Carbon Paper ◽  
The Mean

The gas diffusion layer (GDL) is undoubtedly one of the most complicated components used in a polymer electrolyte fuel cell (PEFC) in terms of liquid and gas transport phenomena. An appropriate fuel cell design seeks a fundamental study of this tortuous porous component. Currently, porosity and gas permeability have been known as some of the key parameters affecting liquid and gas transport through the GDL. Although these are dominant parameters defining mass transport through porous layers, there are still many other factors affecting the transport phenomena and overall cell performance. In this work, the microstructural properties of Toray carbon papers with different thicknesses and for polytetrafluoroethylene (PTFE) treated and untreated cases have been studied based on scanning electron microscopy (SEM) image analysis. The water droplet contact angle, as a dominant macroscale property, along with the mean pore diameter, pore diameter distribution, and pore roundness distribution, as important microscale properties, have been studied. It was observed that the mean pore diameter of Toray carbon paper does not change with its thickness and PTFE content. Mean pore diameter for Toray carbon papers was calculated to be around 26μm, regardless of their thicknesses and PTFE content. It was also observed that the droplet contact angle on the GDL surface does not vary with the GDL thickness. The average contact angle for the 10 wt. % PTFE treated GDLs of different thicknesses was measured at about 150 deg. Finally, the heterogeneous in-plane PTFE distribution on the GDL surface was observed to have no effect on the mean pore diameter of GDLs.

In-Plane Microstructure of Gas Diffusion Layers With Different Properties for PEFC

2013 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Kazuya Tajiri
Keyword(s):  
Contact Angle ◽  
Fuel Cell ◽  
Pore Diameter ◽  
Gas Transport ◽  
Gas Permeability ◽  
Transport Phenomena ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Diameter Distribution ◽  
Carbon Paper

Gas diffusion layer (GDL) is undoubtedly one of the most complicated components used in a polymer electrolyte fuel cell (PEFC) in terms of liquid and gas transport phenomena. An appropriate fuel cell design seeks a fundamental study of this tortuous porous component. Currently, porosity and gas permeability have been known as some of the key parameters affecting liquid and gas transport through GDL. Although these are dominant parameters defining mass transport through porous layers, there are still many other factors affecting transport phenomena as well as overall cell performance. In this work, microstructural properties of Toray carbon papers with different thicknesses and for polytetrafluoroethylene (PTFE) treated and untreated cases have been studied based on scanning electron microscopy (SEM) image analysis. Water droplet contact angle as a dominant macroscale property as well as mean pore diameter, pore diameter distribution, and pore roundness distribution as important microscale properties have been studied. It was observed that the mean pore diameter of Toray carbon paper does not change with its thickness and PTFE content. Mean pore diameter for Toray carbon papers was calculated to be around 26μm regardless of their thicknesses and PTFE content. It was also observed that droplet contact angle on GDL surface does not vary with GDL thickness. The average contact angle for 10 wt.% PTFE treated GDLs of different thicknesses was measured about 150°. Finally, the heterogeneous in-plane PTFE distribution on the GDL surface was observed to have no effect on mean pore diameter of GDLs.

scholarly journals Transport Parameter Correlations for Digitally Created PEFC Gas Diffusion Layers by Using OpenPNM

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1141
Author(s):  
Ángel Encalada-Dávila ◽  
Mayken Espinoza-Andaluz ◽  
Julio Barzola-Monteses ◽  
Shian Li ◽  
Martin Andersson
Keyword(s):  
Fuel Cell ◽  
Energy Conversion ◽  
Transport Phenomena ◽  
Electrical Energy ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Carbon Paper ◽  
Transport Parameter ◽  
Transport Parameters ◽  
Depth Analysis

A polymer electrolyte fuel cell (PEFC) is an electrochemical device that converts chemical energy into electrical energy and heat. The energy conversion is simple; however, the multiphysics phenomena involved in the energy conversion process must be analyzed in detail. The gas diffusion layer (GDL) provides a diffusion media for reactant gases and gives mechanical support to the fuel cell. It is a complex medium whose properties impact the fuel cell’s efficiency. Therefore, an in-depth analysis is required to improve its mechanical and physical properties. In the current study, several transport phenomena through three-dimensional digitally created GDLs have been analyzed. Once the porous microstructure is generated and the transport phenomena are mimicked, transport parameters related to the fluid flow and mass diffusion are computed. The GDLs are approximated to the carbon paper represented as a grouped package of carbon fibers. Several correlations, based on the fiber diameter, to predict their transport properties are proposed. The digitally created GDLs and the transport phenomena have been modeled using the open-source library named Open Pore Network Modeling (OpenPNM). The proposed correlations show a good fit with the obtained data with an R-square of approximately 0.98.

An X-Ray Tomography Based Lattice Boltzmann Simulation Study on Gas Diffusion Layers of Polymer Electrolyte Fuel Cells

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
Pratap Rama ◽  
Yu Liu ◽  
Rui Chen ◽  
Hossein Ostadi ◽  
Kyle Jiang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Lattice Boltzmann ◽  
Gas Diffusion ◽  
Transport Processes ◽  
Polymer Electrolyte Fuel Cell ◽  
Absolute Permeability ◽  
Carbon Paper ◽  
X Ray ◽  
Microscale Transport

This work reports a feasibility study into the combined full morphological reconstruction of fuel cell structures using X-ray computed micro- and nanotomography and lattice Boltzmann modeling to simulate fluid flow at pore scale in porous materials. This work provides a description of how the two techniques have been adapted to simulate gas movement through a carbon paper gas diffusion layer (GDL). The validation work demonstrates that the difference between the simulated and measured absolute permeability of air is 3%. The current study elucidates the potential to enable improvements in GDL design, material composition, and cell design to be realized through a greater understanding of the nano- and microscale transport processes occurring within the polymer electrolyte fuel cell.

Thermal Contact Resistance Measurements of Compressed PEFC Gas Diffusion Media

2016 ◽  
Vol 13 (4) ◽  
Author(s):  
Adam S. Hollinger ◽  
Stefan T. Thynell
Keyword(s):  
Fuel Cell ◽  
Contact Resistance ◽  
Pressure Range ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Gas Diffusion ◽  
Temperature Gradients ◽  
Polymer Electrolyte Fuel Cell ◽  
Carbon Paper ◽  
Carbon Cloth

Localized temperature gradients in a polymer electrolyte fuel cell (PEFC) are known to decrease the durability of the polymer membrane. The most important factor in controlling these temperature gradients is the thermal contact resistance at the interface of the gas diffusion layer (GDL) and the bipolar plate. Here, we present thermal contact resistance measurements of carbon paper and carbon cloth GDLs over a pressure range of 0.7–14.5 MPa. Contact resistances are highly dependent upon the clamping pressure applied to a fuel cell, and in the present work, contact resistances vary from 3.5 × 10−4 to 2.0 × 10−5 m2 K/W, decreasing nonlinearly over the pressure range for each material tested. The contact resistances of carbon cloth GDLs are two to four times higher than contact resistances of carbon paper GDLs throughout the range of pressures tested. The data presented here also show that the thermal resistance of the sample is negligible in comparison to the thermal contact resistance. Controlling temperature gradients in a fuel cell is desirable, and the measurements presented here can be used to more accurately predict temperature distribution in a polymer electrolyte fuel cell.

Effects of Assembly Pressure on the Gas Diffusion Layer and Performance of a PEM Fuel Cell

2011 ◽  
Vol 110-116 ◽  
pp. 48-52 ◽  
Author(s):  
Hao Ming Chang ◽  
Min Hsing Chang
Keyword(s):  
Fuel Cell ◽  
Diffusion Layer ◽  
Gas Permeability ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Cell Performance ◽  
Carbon Paper ◽  
Membrane Electrode ◽  
Clamping Pressure

Assembly pressure plays an important role in the factors affecting the performance of a PEM fuel cell. An insufficient clamping pressure may cause large contact resistance and thus lower the cell performance. On the other hand, over-clamping may reduce the porosity and permeability of the gas diffusion layer (GDL) and also result in poor cell performance. Therefore, it is very important to determine the proper assembly pressure for obtaining optimal performance. In this study, we design a special test fixture to evaluate the effect of assembly pressure on the performance of a PEM fuel cell. Without disassembling the fuel cell, the clamping pressure can be adjusted in situ to measure the cell performance directly and precisely. The unique single cell design eliminates the influence of gasket around the membrane electrode assembly (MEA) and makes it possible to estimate the compression effect of GDL independently. Three different types of carbon paper are used in the experiments as the GDLs. The variations of water contact angle, gas permeability, and in-plane electrical resistivity with the assembly pressure are also measured to explore the effects of assembly pressure on these physical properties. The results show that an optimal assembly pressure is always observed in each case, indicating an adequate compression on GDL is quite necessary for fuel cells.

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.

Pore Structure Modeling of Flow in Gas Diffusion Layers of Proton Exchange Membrane Fuel Cells

2010 ◽  
Author(s):  
Zhongying Shi ◽  
Xia Wang
Keyword(s):  
Fuel Cell ◽  
Pore Structure ◽  
Proton Exchange Membrane ◽  
Cell Model ◽  
Transport Phenomena ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Structure Model ◽  
Exchange Membrane

The gas diffusion layer (GDL) in a proton exchange membrane (PEM) fuel cell has a porous structure with anisotropic and non-homogenous properties. The objective of this research is to develop a PEM fuel cell model where transport phenomena in the GDL are simulated based on GDL’s pore structure. The GDL pore structure was obtained by using a scanning electron microscope (SEM). GDL’s cross-section view instead of surface view was scanned under the SEM. The SEM image was then processed using an image processing tool to obtain a two dimensional computational domain. This pore structure model was then coupled with an electrochemical model to predict the overall fuel cell performance. The transport phenomena in the GDL were simulated by solving the Navier-Stokes equation directly in the GDL pore structure. By comparing with the testing data, the fuel cell model predicted a reasonable fuel cell polarization curve. The pore structure model was further used to calculate the GDL permeability. The numerically predicted permeability was close to the value published in the literature. A future application of the current pore structure model is to predict GDL thermal and electric related properties.

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