Graduated Resistance to Gas Flow Through a GDL in an Unconventional PEM Stack

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Terry B. Caston ◽  
Kanthi L. Bhamidipati ◽  
Haley Carney ◽  
Tequila A. L. Harris
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Gas Flow ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Carbon Cloth ◽  
Oxygen Utilization ◽  
Average Current Density ◽  
Reactant Distribution

The goal of this study is to design a gas diffusion layer (GDL) for a polymer electrolyte membrane (PEM) fuel cell with a graduated permeability and thereby graduating the resistance to flow throughout the GDL. It has been shown that in using conventional materials, the GDL exhibits a higher resistance in the through-plane direction due to the orientation of the small carbon fibers that make up the carbon paper or carbon cloth. In this study, a GDL is designed for an unconventional PEM fuel cell stack where the reactant gases are supplied through the side of the GDL rather than through flow field channels machined into a bipolar plate. The effects of changing in-plane permeability, through-plane permeability, GDL thickness, and oxygen utilization on the expected current density distribution at the catalyst layer are studied. Three different thicknesses and three different utilizations are investigated. It has been found that a thinner GDL with a lower utilization yields a higher current density on the electrode. A quantitative metric to measure uniformity of reactant distribution and the ratio of the standard deviation of the current density to the average current density was introduced, and it was found that while the uniformity of the reactant distribution is independent of thickness of the GDL, it is inversely proportional to utilization.

Graduated Flow Resistance Through a GDL in a Novel PEM Stack

2009 ◽  
Author(s):  
Terry B. Caston ◽  
Kanthi L. Bhamidipati ◽  
Haley Carney ◽  
Tequila A. L. Harris
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte Membrane ◽  
Catalyst Layer ◽  
Current Density Distribution ◽  
Pem Fuel Cell ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Carbon Cloth ◽  
Electrolyte Membrane

The goal of this study is to design a gas diffusion layer (GDL) for a polymer electrolyte membrane (PEM) fuel cell with a graduated permeability, and therefore a graduated resistance to flow throughout the GDL. It has been shown that using conventional materials the GDL exhibits a higher resistance in the through-plane direction due to the orientation of the small carbon fibers that make up the carbon paper or carbon cloth. In this study, a GDL is designed for an unconventional PEM fuel cell stack, where the reactant gases are supplied through the side of the GDL rather than through flow field channels, which are machined into a bipolar plate. The effects of changing in-plane permeability, through-plane permeability, and thickness of the GDL on the expected current density distribution at the catalyst layer are studied. Three different thicknesses are investigated, and it is found that as GDL thickness increases, more uniform reactant distribution over the face of the GDL is obtained. Results also show that it is necessary to design a GDL with a much higher in-plane resistance than through-plane resistance for the unconventional PEM stack studied.

Heat and Mass Transport Analysis of Polymer Electrolyte Membrane Fuel Cell With Bipolar Plates

2009 ◽  
Author(s):  
Pavan Kumar Konnepati ◽  
Pradip Majumdar
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Current Density ◽  
Gas Flow ◽  
Polymer Electrolyte Membrane ◽  
Pem Fuel Cell ◽  
Bipolar Plate ◽  
Gas Diffusion ◽  
Limiting Current ◽  
Electrolyte Membrane

Fuel cells convert chemical energy of fuels into electricity directly. Their higher efficiency and low emissions made them prime candidates for next generation power requirements. The Polymer Electrolyte Membrane (PEM) fuel cell has gained attention of both transportation and stationary power generation industries. In this study a three-dimensional computational model for the simulation of Polymer Electrolyte Membrane (PEM) fuel cell unit cell is developed to understand the complex internal mechanisms, and evaluate the effects of bipolar plate designs on the cell performance. The model includes combined heat and mass transfer processes due to convection and diffusion in the gas flow channels of bi-polar plates as well in the gas diffusion layers of the electrodes, and associated electrochemical reactions in a tri-layer PEM fuel cell. Simulation is carried out with straight parallel channels for operating current density in the range from 0.5–1.5 A/cm2 showed significant insight details of PEM fuel cell in terms of distribution of reactant gases, and heat and water transport across the cell. A significantly high variation in gas concentration across the electrode–membrane interfaces and along the channel length is noticed, requiring higher stoichiometric ratios to increase the limiting current density.

A 5-cm2 PEM Fuel Cell Gas Diffusion Layer Experimental Study and Scanning Electron Microscopy Visualization

2019 ◽  
Author(s):  
Jose Montoya Segnini ◽  
Gerardo Carbajal
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fuel Cell ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Carbon Paper ◽  
Carbon Cloth ◽  
Gas Diffusion Layers ◽  
Diffusion Layers ◽  
Scanning Electron

Abstract The present experimental study aims to determine the effect of two different gas diffusion layers in the performance of a 5-cm2 proton exchange membrane (PEM) fuel cell. The gas diffusion layers consisted of a carbon cloth gas diffusion (GDL-CT) and a non-woven carbon paper (Sigracet 25 BC, Sigracet 29, and BC Sigracet 35 BC). The effect of the GDL parameters on the fuel cell performance was evaluated by the polarization curve. Based on the polarization curve results, it was confirmed that the carbon cloth gas diffusion layer had a better performance than the non-woven carbon. Different temperatures, hydrogen flow rates and inlet pressures were tested. Images from the scanning electron microscopy were obtained to visualize the internal structure of a carbon paper GDL and a carbon cloth GDL; it was observed different surface structures between them.

Experimental Evaluation of Air Flow Effect in Gas Diffusion Layer on PEM Fuel Cell Performance

2008 ◽  
Author(s):  
Yutaka Tabe ◽  
Daisuke Yoshida ◽  
Kazushige Kikuta ◽  
Takemi Chikahisa ◽  
Masaya Kozakai
Keyword(s):  
Fuel Cell ◽  
Diffusion Layer ◽  
Current Density ◽  
Gas Diffusion Layer ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Cell Performance ◽  
Stable Operation ◽  
Local Pressure ◽  
The Cross

This paper investigated the effects of gas and liquid water flow on the performance of a polymer electrolyte membrane (PEM) fuel cell using cells to allow direct observation of the phenomena in the cell and measurements of the local current density and the local pressure loss. The experimental results to compare the separator type indicated the effect of cross-over flow in the gas diffusion layer (GDL) under the lands of serpentine separators on cell performance and the potential of straight channel separator to achieve a relatively-uniform current density distribution. To evaluate the cross-over flow under the land of serpentine separators, a simple circuit model of the gas flow was developed. This analysis showed that slight variations in oxygen concentration caused by the cross-over flow under the land affect the local and overall current density distributions. It was also shown that the establishment of gas paths in the deep layer of GDL by the channels filled with condensed water is effective for stable operation at low flow rates of air in the straight channels.

Predicting the Effect of Gas-Flow Channel Spacing on Current Density in PEM Fuel Cells

1999 ◽  
Author(s):  
Hamid Naseri-Neshat ◽  
Sirivatch Shimpalee ◽  
Sandip Dutta ◽  
Woo-kum Lee ◽  
J. W. Van Zee
Keyword(s):  
Fuel Cell ◽  
Cross Sections ◽  
Diffusion Layer ◽  
Current Density ◽  
Gas Flow ◽  
Channel Model ◽  
Three Dimensional ◽  
Pem Fuel Cell ◽  
Flow Channel ◽  
Straight Channel

Abstract The effects of change in diffusion layer width for constant diffusion layer thickness and constant gas-flow channel width are investigated with a straight channel model of a Proton Exchange Membrane (PEM) fuel cell. A three-dimensional 10-cm long straight channel model of the PEM fuel cell is presented. The geometrical model includes diffusion layers on both the anode and cathode sides and the numerical model couples three-dimensional Navier-Stokes flow with electro-chemical reactions occurring in the fuel cell. Contours of the current density, anode water vapor concentration, anode water activity, water molecules per proton flux, and secondary flow velocity vectors at different cross sections are presented for the two diffusion layer widths. For the particular conditions and properties used for this study, the results show a marked difference between the base case (0.16-cm) and the wide (0.72-cm) diffusion layer. The current density is quite uniform at different axial cross sections and cross-flow sections for the 0.16-cm wide diffusion layer. However, for the 0.72-cm wide diffusion layer, the current density decreases more significantly in the axial direction near the edges of the diffusion layer. Numerical predictions of the water transport between cathode and anode across the width of the MEA show the delicate balance of diffusion and electro-osmosis and their effect on the current distribution along channel.

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.

Numerical Modeling and Experimental Analysis of Air-Droplet Interaction in the Channel of a PEM Fuel Cell

2009 ◽  
Author(s):  
Angelo Esposito ◽  
Aaron Motello ◽  
Cesare Pianese ◽  
Yann G. Guezennec
Keyword(s):  
Fuel Cell ◽  
Water Transport ◽  
Gas Flow ◽  
Air Flow ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Mean Value ◽  
Computational Time ◽  
Droplet Growth ◽  
Experimental Apparatus

An accurate low order model (MVM, Mean Value Model) that captures the main water transport mechanisms through the components of a PEM Fuel Cell was developed. Fast simulation time was achieved through a lumped approach in modeling space-dependent phenomena. Evaporation and capillarity were assumed to be the predominant mechanisms of water flow through the gas diffusion media. The model innovative features are not only to simulate the water transport inside the porous media with relative simplicity but also to simulate the water transport at the interface between gas diffusion layer and gas flow channel. In order to preserve a light computational burden, the complex air flow–droplets interaction was modeled with several simplifying assumption and with the support of measured data. The physics that characterizes the single droplet-air flow interaction was analyzed with an experimental apparatus constructed to study the droplet growth and detachment process. Furthermore, the experimental findings were exploited to feed the numerical model with the missing theoretical information and empirical sub-models to guarantee accuracy. Thanks to the fast computational time of the mean value approach followed, the model is suitable for fuel cell design and optimization as well as diagnosis and control strategies development studies.

In-Situ and Ex-Situ Investigation of Lateral Current Density Variations in a PEM Fuel Cell With Serpentine Flow Field

2009 ◽  
Author(s):  
Andrew Higier ◽  
Hongtan Liu
Keyword(s):  
Fuel Cell ◽  
Flow Field ◽  
Contact Resistance ◽  
Current Density ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Ex Situ ◽  
Serpentine Flow Field

One of the most common types of flow field designs used in proton exchange membrane (PEM) fuel cell is the serpentine flow field. It is used for its simplicity of design, its effectiveness in distributing reactants and its water removal capabilities. The knowledge about where current density is higher, under the land or the channel, is critical for flow field design and optimization. Yet, no direct measurement data are available for serpentine flow fields. In this study a fuel cell with a single channel serpentine flow field is used to separately measure the current density under the land and channel on the cathode. In this manner, a systematic study is conducted under a wide variety of conditions and a series of comparisons are made between land and channel current density. Results show that under most operating conditions, current density is higher under the land than that under the channel. However, at low voltage, a rapid drop off in current density occurs under the land due to concentration losses. In order to investigate the cause of the variations of current density under the land and channel and series of ex-situ and in-situ experiments were conducted. In the ex-situ portion of the study, the contact resistance between the gas diffusion electrode (GDE) and the graphite flow plate were measured using an ex-situ impedance spectroscopy technique. The values of the contact resistance under the channel were found to be larger than that under the land. This implies that the contact resistance under the land and channel vary greatly, likely due to variations in compression under different section of the flow field. These variations in turn cause current density variations under the land and channel.

Modeling a Two-Phase Control-Oriented Transient Model of a Single PEM Fuel Cell

2010 ◽  
Author(s):  
Jinglin He ◽  
Song-Yul Choe
Keyword(s):  
Fuel Cell ◽  
Liquid Water ◽  
Gas Flow ◽  
Pem Fuel Cell ◽  
Gas Diffusion ◽  
Water Dynamics ◽  
Two Phase ◽  
Transient Model ◽  
Flow Channels ◽  
Water Amount

This paper proposed a 1D non-isothermal control-oriented transient model of PEM fuel cell unit considering the two-phase water dynamics in gas flow channel, gas diffusion layer, catalyst layer and membrane. It is known that the accumulated liquid water in the gas flow channels can block the transport path in the gas diffusion layer for the reactant gases and degrade the performance of the fuel cell, while the proper water amount in the gas flow channels and other layers can help to maintain high proton conductivity in the membrane. The I-V curve and the change of gas concentrations, liquid water amount and temperature at specific operating conditions are obtained by sweeping the current of fuel cell. The voltage, gas concentration, temperature and water dynamic changes are investigated by applying the step change of the load current. The fuel cell performance affected by temperature and water dynamics is studied by the analysis of the simulation result.

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