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.

A Study of Transport Geometry on Heat/Mass Transfer and Polarization of a Solid Oxide Fuel Cell

2006 ◽  
Author(s):  
Yan Ji ◽  
J. N. Chung ◽  
Kun Yuan
Keyword(s):  
Mass Transfer ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Heat Mass Transfer ◽  
Three Dimensional ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Transfer Coefficients ◽  
Cell Efficiency ◽  
Current Path

The main objective of this paper is to examine the effects of transport geometry on the efficiency of an electrolyte-supported solid oxide fuel cell. A three-dimensional thermo-fluid-electrochemical model is developed to the influences of channel dimensions, rib width and electrolyte thickness on the temperature, mass transfer coefficients, species concentration, local current density and power density. Results demonstrate that decreasing the height of flow channels can significantly lower the average solid temperature and improve the cell efficiency due to higher heat/mass transfer coefficient between the channel wall and flow stream, and a shorter current path. However, this improvement is limited for the smallest channel. The cell with a thicker rib width and a thinner electrolyte layer has higher efficiency and lower average temperature. Numerical simulation will be expected to help optimize the design of a solid oxide fuel cell.

Numerical Analysis of Heat/Mass Transfer and Electrochemical Reaction in an Anode-Supported Flat-Tube Solid Oxide Fuel Cell

2006 ◽  
Author(s):  
Masayuki Suzuki ◽  
Naoki Shikazono ◽  
Koji Fukagata ◽  
Nobuhide Kasagi
Keyword(s):  
Mass Transfer ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Electrochemical Reaction ◽  
Cell Model ◽  
Flow Direction ◽  
Three Dimensional ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Flat Tube

Three-dimensional heat and mass transfer and electrochemical reaction in an anode-supported flat-tube solid oxide fuel cell (FT-SOFC) are studied. Transport and reaction phenomena mainly change in the streamwise direction. Exceptionally, hydrogen and water vapor have large concentration gradients also in the cross section perpendicular to the flow direction, because of the insufficient mass diffusion in the porous anode. Based on these results, we develop a simplified one-dimensional cell model. The distributions of temperature, current, and overpotential predicted by this model show good agreement with those obtained by the full three-dimensional simulation. We also investigate the effects of pore size, porosity and configuration of the anode on the cell performance. Extensive parametric studies reveal that, for a fixed three-phase boundary (TPB) length, rough material grains are preferable to obtain higher output voltage. In addition, when the cell has a thin anode with narrow ribs, drastic increase in the volumetric power density can be achieved with small voltage drop.

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.

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.

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.

Optimization of the Anode Current Collector Layer Thickness for the Cathode-Supported Solid Oxide Fuel Cell

2013 ◽  
Vol 712-715 ◽  
pp. 1325-1329 ◽  
Author(s):  
Wei Kong ◽  
Shi Chuan Su ◽  
Xiang Gao ◽  
Dong Hui Zhang ◽  
Zi Dong Yu
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Layer Thickness ◽  
Current Density ◽  
High Performance ◽  
Current Collector ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Anode Current ◽  
Output Current

The influence of anode current collector layer (ACCL) thickness is studied for different ACCL porosity and different pitch width. The results shows conclusively that the output current density depends strongly on the ACCL thickness and a suitable choice of the ACCL thickness is very important for the high performance of a SOFC stack. Furthermore, the optimal ACCL thickness is found to be dependent linearly on the pitch width and the parameters for the linearity are given.

Numerical Modeling of a Disk Shape Planar SOFC

2004 ◽  
Author(s):  
Zheng Dang ◽  
Hiroshi Iwai ◽  
Kenjiro Suzuki
Keyword(s):  
Mass Transfer ◽  
Numerical Modeling ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Thermal Management ◽  
Effective Means ◽  
Solid Oxide ◽  
Potential Fields ◽  
Oxide Fuel ◽  
Electrochemical Processes

In this study, numerical modeling of air and fuel flows, electrochemical processes, heat and mass transfer and electric potential fields and related electric current has been attempted for a disk shape planar solid oxide fuel cell (SOFC). This is the extension of the previous similar works on a tubular type solid oxide fuel cell, Nishino et al. (2003) and Li and Suzuki (2004). Numerical model to be established can be used as an effective means to simulate the phenomena in the cell. Such information can be used in the optimum design and thermal management of SOFC.

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