Direct Measurement of the Local Current Density Under Land-Channel Areas With Partially-Catalyzed MEAs

2012 ◽  
Author(s):  
Shan Jia ◽  
Hongtan Liu
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Cell Voltage ◽  
Current Density Distribution ◽  
Cathode Side ◽  
High Cell ◽  
Land Area ◽  
Local Current Density ◽  
Local Current ◽  
Voltage Region

In a PEM fuel cell, local current density can vary drastically under the land and channel areas. The non-uniform current density distribution not only affects the overall performance of the fuel cell, but also leads to the local temperature and concentration differentiation on the MEA, which can cause problems such as membrane dehydration and catalyst degradations at certain locations. In order to investigate the local current performance, the objective of this work is to directly measure the local current density variations across the land and channel at the cathode in a PEM fuel cell with partially-catalyzed MEAs. First, the cathode flow plate is specially designed with a single-serpentine channel structure, and the gas diffusion electrode at cathode side is cut to fit this flow field size (5.0cm×1.3cm). Then five different partially-catalyzed MEAs with 1mm width corresponding to different locations from the middle of the gas channel to the middle of the land area are made. Fuel cells with each of the partially-catalyzed MEAs have been tested and the results provide the lateral current density distribution across the channel and the land areas. In the high cell voltage region, local current density is highest under the center of the land area and decreases toward the center of the channel area; while in the low cell voltage region local current density is highest under the middle of the channel area and decrease toward the center of the land area. Different flow rates are tested at the cathode side of the cell to study their effects on the local current density performance along the land-channel direction. And the results show that the flow rate barely has the effect on the current at the high cell voltage region, while it plays a significant role at the low voltage region due to the mass transport effect.

Experimental Investigation of the Propagation of Local Current Density Variations to Adjacent Cells in PEFC Stacks

2005 ◽  
Author(s):  
Marco Santis ◽  
Stefan A. Freunberger ◽  
Matthias Papra ◽  
Felix N. Bu¨chi
Keyword(s):  
Density Distribution ◽  
Working Conditions ◽  
Current Density ◽  
Cell Voltage ◽  
Current Density Distribution ◽  
Polymer Electrolyte Fuel Cell ◽  
Adjacent Cell ◽  
Fuel Cell Stack ◽  
Local Current Density ◽  
Local Current

The propagation of single cell performance losses to adjacent cells in a polymer electrolyte fuel cell stack is studied by means of local current density measurements in a two cell stack. In this stack, the working conditions of adjacent cells can be controlled independently in order to deliberately change the performance of one cell (inducing cell) and study the coupling effects to the adjacent cell (response cell), while keeping the working conditions of the later one unchanged. The experiments have shown that changes in the current density distribution caused by lowering of the air stoichiometry in the inducing cell cause changes in the current density distribution of the response cell in the order of 60% of the change of the inducing cell, even when the air stoichiometry of the response cell is kept constant. The losses in cell voltage of the inducing cell cause losses in cell voltage of the response cell in a magnitude between 30 and 50%.

Effects of Operating Parameters on the Current Density Distribution in Proton Exchange Membrane Fuel Cells

2006 ◽  
Vol 3 (4) ◽  
pp. 464-476 ◽  
Author(s):  
Y. Zhang ◽  
A. Mawardi ◽  
R. Pitchumani
Keyword(s):  
Fuel Cell ◽  
Density Distribution ◽  
Current Density ◽  
Proton Exchange Membrane ◽  
Current Density Distribution ◽  
Pem Fuel Cell ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Local Current Density ◽  
Local Current

During the operation of a proton exchange membrane (PEM) fuel cell, significant variation of the local current density could exist across the cell causing sharp temperature and stress gradients in certain points, and affecting the water management, all of which severely impact the cell performance and reliability. The variation of local current density is a critical issue in the performance of PEM fuel cell, and is influenced by the operating conditions. This article presents a model-assisted parametric design with the objective of determining the operating conditions which maximize the fuel cell performance while maintaining a level of uniformity in the current density distribution. A comprehensive two-dimensional model is adopted to simulate the species transport and electrochemical phenomena in a PEM fuel cell. Numerical simulations are performed for over a wide range of operating conditions to analyze the effects of various operating parameters on the variation of local current density of the fuel cell, and to develop design windows which serve as guideline in the design for maximum power density, minimum reactant stoichiometry, and uniform current density distribution.

The Effects of Feeding Configurations to Water Flooding and General Performance of a Proton Exchange Membrane Fuel Cell

2005 ◽  
Author(s):  
A. B. Mahmud Hasan ◽  
S. M. Guo ◽  
S. V. Ekkad
Keyword(s):  
Fuel Cell ◽  
Power Density ◽  
Current Density ◽  
Proton Exchange Membrane ◽  
Cell Voltage ◽  
Bipolar Plate ◽  
Proton Exchange ◽  
Water Flooding ◽  
Cathode Side ◽  
Exchange Membrane

The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) using different feeding configurations has been studied. Three bipolar plates, namely serpentine, straight channel and interdigitated designs, were arranged in different combinations for the PEMFC anode and cathode sides. Nine combinations in total were tested under different flow rates, working temperatures and loadings. The cell voltage versus current density and the cell power density versus current density curves were obtained. After operating the PEMFC under high current densities, the cell was split and the water flooding in the feeding channels was visually inspected. Experimental results showed that for different feeding configurations, interdigitated bipolar plate in anode side and serpentine bipolar plate in cathode side had the best performance in terms of cell voltage-current density curve, power density output rate, percentage of flooded area in the feeding channels, the pattern of flooding and the fuel utilization rate.

Modeling PEMFC With FLUENT: Numerical Performance and Validations With Experimental Data

2005 ◽  
Author(s):  
Shaoping Li ◽  
Jing Cao ◽  
William Wangard ◽  
Ulrich Becker
Keyword(s):  
Experimental Data ◽  
Fuel Cell ◽  
Current Density ◽  
Mass Fraction ◽  
Polarization Curves ◽  
Local Current Density ◽  
Density Distributions ◽  
Local Current ◽  
Numerical Performance ◽  
Good Agreement

A 3-dimensional, two-phase Computational Fluid Dynamics (CFD) model for PEMFC simulations has been developed and implemented in FLUENT, a general-purpose commercial software package with multi-physics capabilities. The model formulation was given in details in the previous ASME fuel cell conference, together with in-situ distributions of current densities and species concentrations computed for a simple geometry. In this paper, numerical performance of this model in terms of computing time and parallel efficiency are assessed through the computation of a relatively larger-size fuel cell (50 cm2) with serpentine channels. The convergence history and parallel performance data show that the Fluent’s PEMFC model is numerically robust and efficient. In addition to the numerical performance, the physical validity of the model is tested through comparisons with experimental data of polarization curves and local current density distributions from the most recent work of Mench et al [1]. Comparisons with the data show good agreement in the overall polarization curves and reasonably good agreement in local current density distributions too. The comma-shaped local polarization curves seen in the experiments are qualitatively correctly captured. Moreover, our computations show that hydrogen mass fraction and molar concentration can both increase along the anode flow channel, despite that hydrogen is being depleted in the anodic electrochemical reaction. The reason for this to happen is that the osmotic drag moves the water from anode to cathode at a much faster rate than the hydrogen depletion rate. An analytical derivation that reveals the relationship between species molar concentration and mass fraction is also given.

Analysis of Single PEM Fuel Cell Performances Based on Current Density Distribution Measurement

2005 ◽  
Vol 3 (3) ◽  
pp. 351-357 ◽  
Author(s):  
P. C. Ghosh ◽  
T. Wüster ◽  
H. Dohle ◽  
N. Kimiaie ◽  
J. Mergel ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Density Distribution ◽  
Current Density ◽  
Operating Temperature ◽  
Current Density Distribution ◽  
Polymer Electrolyte Fuel Cells ◽  
Operating Conditions ◽  
Cathode Side ◽  
Gas Pressures

A new in situ measurement method of mapping the current density distribution in polymer electrolyte fuel cells (PEFC) is used to analyze the performance of a fuel cell under different operating conditions. The present method is useful in investigating the current density distribution in a single cell as well as a stack, which carries the information about the local reactant activity over the electrode area. It was found that the current density close to the gas inlets is strongly influenced by the reactants' relative humidity. The performance close to the gas outlets is greatly influenced by the inlet gas pressures and the stoichiometry factors of the reactant gases, mainly on the cathode side. It was also observed that the performance of the fuel cell drops with the increase in operating temperature if the reactant gases are not sufficiently humidified.

Numerical Prediction of Local Temperature and Current Density in a PEM Fuel Cell

2000 ◽  
Author(s):  
S. Shimpalee ◽  
S. Dutta ◽  
J. W. Van Zee
Keyword(s):  
Fuel Cell ◽  
Phase Change ◽  
Temperature Change ◽  
Heat Generation ◽  
Current Density ◽  
Pem Fuel Cells ◽  
Water Evaporation ◽  
Fuel Cell Performance ◽  
Local Current Density ◽  
Local Current

Abstract The heat generation inside polymer electrolyte membrane (PEM) fuel cells affects fuel cell performance significantly. A numerical model for three-dimensional single fuel cell is developed by including the energy equation and the phase change aspects. A control volume approach is used and source terms for species transport equations, heat generation, and phase change model are introduced to incorporate the coupled flow physics in commercial flow solvers. Details of local current density distribution and temperature profiles are obtained and predictions from this model are compared with previous conclusions. The results reveal that the water evaporation and condensation generated by temperature change in fuel cell control humidity of the membrane and vary the local current density value. Further, the temperature distributions are dependent on the amount of heat generation created by electrical losses and water phase change. The predictions also present that the performance of the fuel cell relies not only on the inlet humidity condition but also on the temperature change inside the fuel cell.

A Thermo-Fluid/Electrochemical Model for Micro-SOFC

2005 ◽  
Author(s):  
Yan Ji ◽  
J. N. Chung ◽  
Kun Yuan
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Electrical Potential ◽  
Concentration Field ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Concentration Difference ◽  
Local Current Density ◽  
Local Current

In this paper, a three dimensional thermo-fluid/electro-chemical model is proposed to simulate the heat and mass transfer phenomena in a micro-geometry co-flow solid oxide fuel cell. Governing equation of mass, momentum and energy conservation are simultaneously solved. A network circuit is applied to simulate the electrical potential, ohmic losses and activation polarization. Cyclic boundary conditions are imposed at the top and bottom of the model domains, while the lateral walls were assumed adiabatic and insulation. A parametric study examines the effect of micro-channel on the temperature field, concentration field, local current density and power density. Results demonstrate that microchannels can reduce temperature or concentration difference between reaction locations and stream. The local current density is much more uniform and output voltage is also improved. Numerical simulation will be expected to help optimize the design of a micro solid oxide fuel cell.

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