Parallel Manifold Effects on the Heat and Mass Transfer Characteristics of Metal-Supported Solid Oxide Fuel Cell Stacks

2011 ◽  
Vol 8 (6) ◽  
Author(s):  
Joonguen Park ◽  
Joongmyeon Bae
Keyword(s):  
Mass Transfer ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Heat And Mass Transfer ◽  
Current Density ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Bottom Cell ◽  
Average Current ◽  
The Cross

The metal-supported solid oxide fuel cell (SOFC) was introduced as a new fuel cell design because it provides high mechanical strength and blocks gas leakage. Ordinary SOFCs should be manufactured in a stack because a single cell does not have sufficient capacity for a commercial system. In a stack, heat and mass transfer, which affects the performance, is altered by manifold structures. Therefore, this paper studied three kinds of manifold designs using numerical analyses. Governing equations and electrochemical reaction models were calculated simultaneously to conduct multiphysics simulations. Molecular diffusion and Knudsen diffusion were considered together to predict gas diffusion in a porous medium. Simulation results were compared with experimental data to validate the numerical code. There was a high current density with a high partial pressure of reactant gas on the hydrogen inlet and at the point where the hydrogen channel and the air channel intersected. The average current density of a cross-co flow design was 4890.5 A/m2, which was higher than the other designs used in this study. The average current densities of the cross-counter flow design and the cross flow design were 4689.1 and 4111.8 A/m2, respectively. The maximum pressure was 750 Pa in the air manifold and 32 Pa in the hydrogen manifold. The temperature of the bottom cell was lower than the top cell because the bottom cell had little exothermic heat by low polarization.

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.

Interdigitated Heat/Mass Transfer and Chemical/Electrochemical Reactions in a Planar Type Solid Oxide Fuel Cell

2003 ◽  
Author(s):  
Pei-Wen Li ◽  
Laura Schaefer ◽  
Minking K. Chyu
Keyword(s):  
Mass Transfer ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Heat Mass Transfer ◽  
High Current Density ◽  
Flow Direction ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Operation Conditions

The details of the heat/mass transfer in a planar type solid oxide fuel cell that controls the energy conversion performance are studied by employing a three-dimensional numerical computation for the fields of velocity, gas mass fractions and temperature. The SOFC under investigation is a unit working in a SOFC stack. It has the tri-layer of anode-electrolyte-cathode and interconnects having multiple channels for fuel and air. Two designs of the tri-layer, anode-supported and electrolyte-supported, are studied. Pre-reformed fuel gas with components of H2, H2O, CO, CO2 and CH4 is arranged in cross-flow direction with airflow. Further reforming and shift reaction in fuel channels were considered at chemical equilibrium. It was found that the consumption and production of gas species are different in the different channels. High current density was located in the upstream area of fuel channels. The operation conditions of current density affected the temperature level significantly.

Performance Metrics for Solid Oxide Fuel Cell Cross-Section Design

2009 ◽  
Author(s):  
George J. Nelson ◽  
Comas Haynes ◽  
William Wepfer
Keyword(s):  
Fuel Cell ◽  
Partial Pressure ◽  
Solid Oxide Fuel Cell ◽  
Correction Factor ◽  
Current Density ◽  
Performance Metrics ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Pressure Distributions ◽  
Button Cell

Analytical models have been developed to describe the partial pressure distributions of reactants within solid oxide fuel cell (SOFC) electrodes and introduce the concept of a reactant depletion current density. These existing analytical expressions for two-dimensional reactant partial pressure distributions and the reactant depletion current density are presented in non-dimensional form. Performance metrics for SOFC electrodes are developed including a correction factor that can be applied to button-cell predictions of pressure distribution and two forms of dimensionless reactant depletion current density. Performance predictions based on these metrics are compared to numerical predictions of partial pressure and depletion current density based on a finite element solution of the dusty-gas model (DGM) within SOFC electrodes. It is shown that the pressure correction factor developed provides a reasonable prediction of interconnect geometry effects. Thus, it is presented as a modeling tool that can be applied to translate component level fidelity to cell and stack level models. The depletion current density metrics developed are used to present basic design maps for SOFC unit cell cross-sections. These dimensionless forms of the depletion current density quantify the influence of sheet resistance effects on reactant depletion and can predict the deviation from the limiting current behavior predicted using a button-cell model.

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