An Investigation Into the Impact of the Performance Efficiency of PEM Fuel Cells From Coupling Channel Dimensions With Flow Configurations

2006 ◽  
Author(s):  
Manish Jindal ◽  
Mark Archambault
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Mass Flow ◽  
Current Density ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Average Current Density ◽  
Average Current ◽  
Flow Directions ◽  
Relative Flow

Proton Exchange Membrane fuel cells are receiving a great deal of attention due to their low-temperature characteristics and environmental friendliness. Significant research has been conducted towards understanding and perfecting these devices so as to realize their potential to produce power with maximum efficiency and minimum cost. While much work has been done to refine the electrochemical and mass transport models describing the physics of the cell in the vicinity of the catalyst and membrane layers, comparatively little attention has been paid to the fluid dynamics phenomena within the cell and how it impacts the efficiency and performance of the device. The purpose of this work is to combine a subset of previously reported results and determine whether they can be incorporated into a single PEM fuel cell to further increase the performance above and beyond the increase obtained by implementing them separately. Several three-dimensional models with varying channel shapes, relative flow directions, and operating conditions were developed. Various inlet flow distributions were imposed to evaluate the most efficient fuel cell configuration. Results show that there are only minor differences in the average current density of the fuel cell with changes in the channel cross-sectional shape. Moreover, there is little impact on performance with variations in the relative flow directions of the inlet gases. While only slight increases in fuel cell performance were observed with most mass flow rate distributions across the channels, alternating high and low mass flow rates in adjacent channels provided almost a 3% increase in average current density over a uniform profile.

Current Distribution in a Polymer Electrolyte Membrane Fuel Cell Under Flooding Conditions

2009 ◽  
Author(s):  
A. Jamekhorshid ◽  
G. Karimi ◽  
X. Li
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Current Distribution ◽  
Current Density ◽  
Polymer Electrolyte Membrane ◽  
Operating Conditions ◽  
Average Current Density ◽  
Electrolyte Membrane ◽  
Wide Range ◽  
Average Current

Non-uniform current distribution in polymer electrolyte membrane fuel cells results in local over-heating, accelerated ageing, and lower power output than expected. This issue is very critical when fuel cell experiences water flooding. In this work, the performance of a PEM fuel cell is investigated under cathode flooding conditions. A partially flooded GDL model is proposed to study local current density distributions along flow fields over a wide range of cell operating conditions. The model results show as cathode inlet humidity and/or cell pressure increase the average current density for the unflooded portions of the cell increases but the system becomes more sensitive to flooding. Operating the cell at higher temperatures would lead to higher average current densities and the chance of system being flooded is reduced. In addition, higher cathode stoichiometries prevent system flooding but the average current density remains almost constant.

Modeling, parametric analysis and optimization of an anode-supported planar solid oxide fuel cell

2015 ◽  
Vol 229 (17) ◽  
pp. 3125-3140 ◽  
Author(s):  
Mehdi Borji ◽  
Kazem Atashkari ◽  
Nader Nariman-zadeh ◽  
Mehdi Masoumpour
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Temperature Difference ◽  
Current Density ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Multi Objective Optimization ◽  
Average Current Density ◽  
Multi Objective ◽  
Average Current

Solid oxide fuel cell is a promising tool for distributed power generation systems. This type of power system will experience different conditions during its operating life. The present study aims to simulate mathematically a direct internal reforming planar type anode supported solid oxide fuel cell considering mass and energy conservation equations along with a complete electrochemical model. Two main reactions, namely water–gas shift reaction and methane steam reforming reaction, are considered as two dominant reactions occurring in a fuel cell. Such a model may be employed to examine the effect of different operating conditions on main solid oxide fuel cell parameters, such as temperature gradients, power, and efficiency. Furthermore, using such mathematical model, a multi-objective optimization procedure can be applied to determine maximum cell efficiency and output power under constraints such as the allowable temperature difference and limited operating potential. The selected design variables are air ratio, fuel utilization, average current density, steam to carbon ratio, and pre-reforming rate of methane. It has been revealed that any increase in pre-reforming rate of methane and steam to carbon ratio of the entering fuel will lead to efficiency penalty and more uniform temperature distribution along the cell. In addition, the more average current density increases, the less electric efficiency is achieved, and on the other hand, the more temperature difference along the cell is seen. Besides, it is shown that some interesting and important relationships as useful optimal design principles involved in the performance of solid oxide fuel cells can be discovered by Pareto based multi-objective optimization of the mathematically obtained model representing their electric performance. Such important optimal principles would not have been obtained without the use of both mathematical modeling and the Pareto optimization approach.

Analysis of Water Morphology in the Active Area and Channel-to-Manifold Transitions of a PEM Fuel Cell

2014 ◽  
Author(s):  
Daniel J. Fenton ◽  
Jeffrey J. Gagliardo ◽  
Thomas A. Trabold
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Flow Field ◽  
Current Density ◽  
Liquid Water ◽  
Pem Fuel Cells ◽  
Operating Conditions ◽  
Active Area ◽  
Water Volume ◽  
Crossover Point

To achieve optimal performance of proton exchange membrane (PEM) fuel cells, effective water management is crucial. Cells need to be fabricated to operate over wide ranges of current density and cell temperature. To investigate these design and operational conditions, the present experiment utilized neutron radiography for measurement of in-situ water volumes of operating PEM fuel cells under varying operating conditions. Fuel cell performance was found to be generally inversely correlated to liquid water volume in the active area. High water concentrations restrict narrow flow field channels, limiting the reactant flow, and causing the development of performance-reducing liquid water blockages (slugs). The analysis was performed both quantitatively and qualitatively to compare the overall liquid water volume within the cell to the flow field geometry. The neutron image analysis results revealed interesting trends related to water volume as a function of time. At temperatures greater than 25°C, the total liquid water volume at start-up in the active area was the lowest at 1.5 A/cm2. At 25°C, 0.1 A/cm2 performed with the least amount of liquid water accumulation. However, as the reaction progressed at temperatures above 25°C, there was a crossover point where 0.1 A/cm2 accumulated less water than 1.5 A/cm2. The higher the temperature, the longer the time required to reach this crossover point. Results from the current density analysis showed a minimization of water slugs at 1.5 A/cm2, while the temperature analysis showed unexpectedly that, independent of current density, the condition with lowest water volume was always 35°C.

scholarly journals Measurement of polarization curve and development of a unique semi empirical model for description of PEMFC and DMFC performances

2011 ◽  
Vol 17 (2) ◽  
pp. 207-214 ◽  
Author(s):  
T. Selyari ◽  
A.A. Ghoreyshi ◽  
M. Shakeri ◽  
G.D. Najafpour ◽  
T. Jafary
Keyword(s):  
Experimental Data ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Current Density ◽  
Power Output ◽  
Cell Voltage ◽  
Operating Conditions ◽  
Cell Performance ◽  
Oxygen Stoichiometry ◽  
Semi Empirical

In this study, a single polymer electrolyte membrane fuel cell (PEMFC) in H2/O2 form with an effective dimension of 5?5 cm as well as a single direct methanol fuel cell (DMFC) with a dimension of 10?10 cm were fabricated. In an existing test station, the voltage-current density performances of the fabricated PEMFC and DMFC were examined under various operating conditions. As was expected DMFC showed a lower electrical performance which can be attributed to the slower methanol oxidation rate in comparison to the hydrogen oxidation. The results obtained from the cell operation indicated that the temperature has a great effect on the cell performance. At 60?C, the best power output was obtained for PEMFC. There was a drop in the cell voltage beyond 60?C which can be attributed to the reduction of water content inside the membrane. For DMFC, maximum power output was resulted at 64oC. Increasing oxygen stoichiometry and total cell pressure had a marginal effect on the cell performance. The results also revealed that the cell performance improved by increasing pressure differences between anode and cathode. A unified semi-empirical thermodynamic based model was developed to describe the cell voltage as a function of current density for both kinds of fuel cells. The model equation parameters were obtained through a nonlinear fit to the experimental data. There was a good agreement between the experimental data and the model predicted cell performance for both types of fuel cells.

A Comprehensive Analysis Procedure for Predicting the Performance of a Molten Carbonate Fuel Cell

2008 ◽  
Author(s):  
D. H. Choi ◽  
H. S. Kim
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Cell Voltage ◽  
Unit Cell ◽  
Molten Carbonate Fuel Cell ◽  
Molten Carbonate ◽  
Average Current Density ◽  
Local Current ◽  
Average Current ◽  
Carbonate Fuel Cell

A three-dimensional numerical procedure to predict the performance of a molten carbonate fuel cell has been developed. The Navier-Stokes, energy, and species equations are solved to obtain the velocity, temperature, pressure, and concentration distributions in the cathode/ anode channel. The channel with the trapezoidal supports is approximated by an anisotropic porous medium, of which the effective permeability and conductivity are obtained by separate 3D FVM calculations. For a given average current density, the local current density, which is directly related to the rate of chemical reaction and heat generation on the reaction surface, and the cell voltage are determined to satisfy the electrochemical relations at the electrode surface. The process is iterative and the solution is assumed to have converged when the cell voltage and the local current density fall within the specified convergence limits. The unit cell characteristics, such as current-density distribution, and average current density vs. cell voltage are presented and discussed. Once the relation between the flow rate and the pressure loss in a unit cell are known, the mass flow to each cell of a MCFC stack is estimated by coupling the manifold flow and the flow within the unit cell. The stack performance is then calculated by integrating the individual cell performance using this information.

scholarly journals Modelling of Humidity Dynamics for Open-Cathode Proton Exchange Membrane Fuel Cell

2021 ◽  
Vol 12 (3) ◽  
pp. 106
Author(s):  
Fengxiang Chen ◽  
Liming Zhang ◽  
Jieran Jiao
Keyword(s):  
Fuel Cell ◽  
Mass Flow ◽  
Proton Exchange Membrane ◽  
Flow Model ◽  
Transport Theory ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Output Performance ◽  
Exchange Membrane

The durability and output performance of a fuel cell is highly influenced by the internal humidity, while in most developed models of open-cathode proton exchange membrane fuel cells (OC-PEMFC) the internal water content is viewed as a fixed value. Based on mass and energy conservation law, mass transport theory and electrochemistry principles, the model of humidity dynamics for OC-PEMFC is established in Simulink® environment, including the electrochemical model, mass flow model and thermal model. In the mass flow model, the water retention property and oxygen transfer characteristics of the gas diffusion layer is modelled. The simulation indicates that the internal humidity of OC-PEMFC varies with stack temperature and operating conditions, which has a significant influence on stack efficiency and output performance. In order to maintain a good internal humidity state during operation, this model can be used to determine the optimal stack temperature and for the design of a proper control strategy.

The efficient use of stabilizing materials in superconducting solenoids

1969 ◽  
Vol 47 (13) ◽  
pp. 1401-1407 ◽  
Author(s):  
Richard Stevenson
Keyword(s):  
Current Density ◽  
Transient Heat Conduction ◽  
Point Of View ◽  
Average Current Density ◽  
Initial Current ◽  
Current Sharing ◽  
Purity Aluminium ◽  
High Purity Aluminium ◽  
Average Current ◽  
Composite Conductor

The problem of stability of superconducting solenoids is considered from a thermal point of view. The transient heat conduction equation for a superconducting tape clad with normal material and operated in a current sharing mode is studied, and a solution for the temperature distribution is obtained. The composite conductor is considered stable if its final temperature in the current sharing mode corresponds to the critical temperature for the initial current density in the superconductor. Using this criterion, the operating point of the superconductor and its stabilizing cladding thickness can be chosen to give a maximum average current density in the composite conductor at any field. Calculations are given for Nb3Sn tape clad with OFHC copper and with high purity aluminium.

The Resistive Properties of Proton Exchange Membrane Fuel Cells With Stainless Steel Bipolar Plates

2010 ◽  
Vol 7 (4) ◽  
Author(s):  
Shuo-Jen Lee ◽  
Kung-Ting Yang ◽  
Yu-Ming Lee ◽  
Chi-Yuan Lee
Keyword(s):  
Stainless Steel ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Single Cells ◽  
Operating Conditions ◽  
Pure Oxygen ◽  
Bipolar Plates ◽  
Transfer Resistance ◽  
Treated Cell ◽  
Ohmic Resistance

In this research, electrochemical impedance spectroscopy is employed to monitor the resistance of a fuel cell during operation with different operating conditions and different materials for the bipolar plates. The operating condition variables are cell humidity, pure oxygen or air as oxidizer, and current density. Three groups of single cells were tested: a graphite cell, a stainless steel cell (treated and original), and a thin, small, treated stainless steel cell. A treated cell here means using an electrochemical treatment to improve bipolar plate anticorrosion capability. From the results, the ohmic resistance of a fully humidified treated stainless steel fuel cell is 0.28 Ω cm2. Under the same operating conditions, the ohmic resistance of the graphite and the original fuel cell are each 0.1 Ω cm2 and that of the small treated cell is 0.3 Ω cm2. Cell humidity has a greater influence on resistance than does the choice of oxidizer; furthermore, resistance variation due to humidity effects is more serious with air support. From the above results, fuel cells fundamental phenomenon such as ohmic resistance, charge transfer resistance, and mass transport resistance under different operating conditions could be evaluated.

scholarly journals The study of Zn–Co alloy coatings electrochemically deposited by pulse current

2012 ◽  
Vol 66 (5) ◽  
pp. 749-757 ◽  
Author(s):  
Jelena Bajat ◽  
Miodrag Maksimovic ◽  
Milorad Tomic ◽  
Miomir Pavlovic
Keyword(s):  
Surface Roughness ◽  
Current Efficiency ◽  
Direct Current ◽  
Current Density ◽  
Pulse Current ◽  
Pulse Plating ◽  
Cathodic Current ◽  
Average Current Density ◽  
Corrosion Stability ◽  
Average Current

The electrochemical deposition by pulse current of Zn-Co alloy coatings on steel was examined, with the aim to find out whether pulse plating could produce alloys that could offer a better corrosion protection. The influence of on-time and the average current density on the cathodic current efficiency, coating morphology, surface roughness and corrosion stability in 3% NaCl was examined. At the same Ton/Toff ratio the current efficiency was insignificantly smaller for deposition at higher average current density. It was shown that, depending on the on-time, pulse plating could produce more homogenous alloy coatings with finer morphology, as compared to deposits obtained by direct current. The surface roughness was the greatest for Zn-Co alloy coatings deposited with direct current, as compared with alloy coatings deposited with pulse current, for both examined average current densities. It was also shown that Zn-Co alloy coatings deposited by pulse current could increase the corrosion stability of Zn-Co alloy coatings on steel. Namely, alloy coatings deposited with pulse current showed higher corrosion stability, as compared with alloy coatings deposited with direct current, for almost all examined cathodic times, Ton. Alloy coatings deposited at higher average current density showed greater corrosion stability as compared with coatings deposited by pulse current at smaller average current density. It was shown that deposits obtained with pulse current and cathodic time of 10 ms had the poorest corrosion stability, for both investigated average deposition current density. Among all investigated alloy coatings the highest corrosion stability was obtained for Zn-Co alloy coatings deposited with pulsed current at higher average current density (jav = 4 A dm-2).

scholarly journals Electrochemical Performance Improvement of the Catalyst of the Methanol Micro-Fuel Cell Using Carbon Nanotubes

2019 ◽  
Author(s):  
Mohammad Kazemi Nasrabadi ◽  
Amir Ebrahimi-Moghadam ◽  
Mohammad Hosein Ahmadi ◽  
Ravinder Kumar ◽  
Narjes Nabipour
Keyword(s):  
Carbon Nanotubes ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Carbon Black ◽  
Oxidation Reaction ◽  
High Energy ◽  
Proton Exchange ◽  
Operating Conditions ◽  
High Energy Density ◽  
Methanol Oxidation Reaction

Due to low working temperature, high energy density and low pollution, proton exchange fuel cells have been investigated under different operating conditions in different applications. Using platinum catalysts in methanol fuel cells leads to increasing the cost of this kind of fuel cell which is considered as a barrier to the commercialism of this technology. For this reason, a lot of efforts have been made to reduce the loading of the catalyst required on different supports. In this study, carbon black (CB) and carbon nanotubes (CNT) have been used as catalyst supports of the fuel cell as well as using the double-metal combination of platinum-ruthenium (PtRu) as anode electrode catalyst and platinum (Pt) as cathode electrode catalyst. The performance of these two types of electro-catalyst in the oxidation reaction of methanol has been compared based on electrochemical tests. Results showed that the carbon nanotubes increase the performance of the micro-fuel cell by 37% at maximum power density, compared to the carbon black. Based on thee-electrode tests of chronoamperometry and voltammetry, it was found that the oxidation onset potential of methanol for CNT has been around 20% less than CB, leading to the kinetic improvement of the oxidation reaction. The current density of methanol oxidation reaction increased up to 62% in CNT sample compared to CB supported one, therefore the active electrochemical surface area of the catalyst has been increased up to 90% by using CNT compared to CB which shows the significant rise of the electrocatalytic activity in CNT supported catalyst. Moreover, the resistance of the CNT supported sample to poisonous intermediate species has been found 3% more than CB supported one. According to the chronoamperometry test results, it was concluded that the performance and sustainability of the CNT electro-catalyst show remarkable improvement compared to CB electro-catalyst in the long term.

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