A Numerical Investigation Into the Use of Patterned Electrodes in a Segmented-in-Series Tubular SOFC

2008 ◽  
Author(s):  
B. A. Haberman ◽  
G. Bortuzzo ◽  
A. J. Marquis
Keyword(s):  
Current Flow ◽  
Ionic Current ◽  
Current Collector ◽  
Computer Code ◽  
Flow Path ◽  
High Conductivity ◽  
Cell Performance ◽  
Additional Layer ◽  
Ceramic Support ◽  
In Series

A typical segmented-in-series tubular SOFC consists of flattened ceramic support tubes with rows of electrochemical cells fabricated on their outer surfaces and connected in series along their length. In this design, the electrical resistance of the long current flow path is minimised by using high conductivity electrodes. Therefore the resistance of the cathode, which typically has a low electrical conductivity, is reduced by fabricating an additional high conductivity current collector layer. This study is concerned with investigating the design of this additional layer using the newly developed SOHAB multi-physics computer code. Initial simulations identified the optimum thickness of a uniform current collector with respect to cell performance and component cost. However, it was found that this uniform layer causes ionic current to concentrate near the edges of the electrolyte, potentially enhancing cell degradation. Further simulations investigated whether a patterned current collector could be designed to control the current flow within the cell and reduce this detrimental effect. It was found that, for an identical thickness collector layer, a patterned design could reduce spatial variations of ionic current by a factor of over two with a negligible effect on cell performance. Therefore, patterned current collectors represent a means to control the current flow path within a segmented-in-series cell and further improve its performance.

A Numerical Investigation Into the Interaction Between Current Flow and Fuel Consumption in a Segmented-in-Series Tubular SOFC

2009 ◽  
Vol 6 (3) ◽  
Author(s):  
B. A. Haberman ◽  
A. J. Marquis
Keyword(s):  
Density Distribution ◽  
Fuel Consumption ◽  
Current Density ◽  
Current Flow ◽  
Flow Direction ◽  
Ionic Current ◽  
Leading Edge ◽  
Current Density Distribution ◽  
Fuel Flow ◽  
In Series

A typical segmented-in-series tubular solid oxide fuel cell (SOFC) consists of flattened ceramic support tubes with rows of electrochemical cells fabricated on their outer surfaces connected in series. It is desirable to design this type of SOFC to operate with a uniform electrolyte current density distribution to make the most efficient use of the available space and possibly to help minimize the onset of cell component degradation. Predicting the electrolyte current density distribution requires an understanding of the many physical and electrochemical processes occurring, and these are simulated using the newly developed SOHAB multiphysics computer code. Of particular interest is the interaction between the current flow within the cells and the consumption of fuel from an adjacent internal gas supply channel. Initial simulations showed that in the absence of fuel consumption, ionic current tends to concentrate near the leading edge of each electrolyte. Further simulations that included fuel consumption showed that the choice of fuel flow direction can have a strong effect on the current flow distribution. The electrolyte current density distribution is biased toward the upstream fuel flow direction because ionic current preferentially flows in regions rich in fuel. Thus the correct choice of fuel flow direction can lead to more uniform electrolyte current density distributions, and hence it is an important design consideration for tubular segmented-in-series SOFCs. Overall, it was found that the choice of fuel flow direction has a negligible effect on the output voltage of the fuel cells.

scholarly journals Developing the Flow Path For the K-1250-6.9/25 Turbine Unit Using the Optimal Design Methods

2021 ◽  
pp. 15-18
Author(s):  
Ihor Palkov ◽  
Sergii Palkov ◽  
Oleh Ishchenko ◽  
Olena Avdieieva
Keyword(s):  
Numerical Experiment ◽  
Cross Sections ◽  
Turbine Unit ◽  
Current Flow ◽  
Three Dimensional ◽  
Flow Path ◽  
Three Dimensional Model ◽  
Flow Paths ◽  
Intermediate Pressure ◽  
Blade System

The paper considers the main principles that are used to develop the flow paths (FP) of the high-pressure cylinders (HPC), intermediate-pressure cylinders (IPC), and low-pressure cylinders (LPC) for the K-1250-6.9/25 turbine unit. It describes approaches to the numerical experiment when designing flow paths, the advantage of which is lower labor, time and financial costs and higher informativeness compared to the physical experiment on flow paths. When designing the flow paths of high- and intermediate-pressure cylinders (HIPC), the numerical experiment is performed using the three-dimensional viscous-flow method. For this purpose, a three-dimensional model of the blade system in the flow path is built, which consists of a large number of finite volumes (elements) in the shape of hexagons, in each of which the integration of the equations of gas dynamics is performed. When developing LPC, the method of parameterization and analytical profiling of the blade crown sections is used, where the profiles are described by the curves of the fourth and fifth orders with the condition of providing the minimum value of the maximum curvature and monotonicity of variation of the three-dimensional blade geometry along height. This method allows obtaining the optimal profiles of the cross sections of the blades, which correspond to the current flow lines to the fullest extent, and minimizing the profile energy losses when the flow flows around the blades.

Ionic current flow through ZnO nanotubes

2009 ◽  
Vol 20 (50) ◽  
pp. 505504 ◽  
Author(s):  
Safaa Al-Hilli ◽  
M Willander
Keyword(s):  
Current Flow ◽  
Ionic Current ◽  
Zno Nanotubes ◽  
Flow Through

scholarly journals Contact resistivity and current flow path at metal/graphene contact

2010 ◽  
Vol 97 (14) ◽  
pp. 143514 ◽  
Author(s):  
K. Nagashio ◽  
T. Nishimura ◽  
K. Kita ◽  
A. Toriumi
Keyword(s):  
Current Flow ◽  
Flow Path ◽  
Contact Resistivity

A Microfabricated Device for the Characterization of Biological Entities

2001 ◽  
Vol 679 ◽  
Author(s):  
H. Chang ◽  
A. Ikram ◽  
M. Young ◽  
F. Kosari ◽  
G. Vasmatzis ◽  
...  
Keyword(s):  
Current Flow ◽  
Ionic Current ◽  
Listeria Innocua ◽  
Test Case ◽  
Micro Machining ◽  
Initial Test ◽  
Buffer Solutions ◽  
Effective Mobility ◽  
Biological Entities

ABSTRACTA micro-fabricated pore is constructed and tested so that it can be used to characterize biological entities. The pore is prepared by bulk micro-machining of a silicon wafer. An oxide coated silicon diaphragm with the pore is placed between two chambers containing ionic buffer solutions to mimic a bilayer system. If a voltage is applied across the pore, electrophoretic passage of charged entities can be electrically detected through changes in the ionic current flow. When the entities traverse the pore, the ionic current is blocked and a decrease in the current can be observed. As an initial test case, negatively charged polystyrene beads which were 2.38μm in diameter, were electrophoretically driven across the pore. Then the bacteriumListeria innocua, suspended in Tris-glycine buffer, was also electrophoretically driven through the pore and its effective mobility was extracted. The device can also be used to study the interactions between organisms and the micro-fabricated surfaces. Work is continuing to scale the pore to the sub-100A range to be used for characterization and possible sequencing of single molecules such as DNA.

Prediction of Flow and Erosion in Power Utility Boilers and Comparison With Measurement

1997 ◽  
Vol 119 (3) ◽  
pp. 709-716 ◽  
Author(s):  
J. Y. Tu ◽  
C. A. J. Fletcher ◽  
M. Behnia ◽  
J. A. Reizes ◽  
D. Owens ◽  
...  
Keyword(s):  
Fly Ash ◽  
Flow Velocity ◽  
Flue Gas ◽  
Computer Code ◽  
Flow Path ◽  
Front Wall ◽  
Rear Wall ◽  
Power Utility ◽  
Utility Boilers ◽  
Power Utility Boilers

Multidimensional simulations of both flue gas and fly ash (solid particle) flows with application to erosion prediction in the economisers of coal-fired power utility boilers are reported. A computer code specifically designed for power utility boilers, DS4PUB (Design Software for Power Utility Boilers), was used for the calculations. The major area of erosion often occurs at the economizer of the boiler and depends on the particulate velocity and concentration so that computational results include the economizer inlet distribution of the mean flue gas and particulate velocities, and fly ash concentration. The computer code was validated by comparisons with previously available experimental data and recently performed measurements for flue gas flow velocity, dust burden, and erosion rates at the inlet of economizers in large operating power stations. The results of the multidimensional simulations agreed reasonably well with the experimental measurements. An important finding of this study is that the transverse location of maximum erosion in the economizer tube bank strongly depends on the upstream geometric design of the boiler. For boilers with a shorter turning flow path, the maximum erosion is found to be close to the rear wall of the economizer because both the maximum particulate velocity and concentration occur in this region. For configurations with a long flow path, which includes a splitter plate, the maximum erosion region was found to be closer to the front wall of the economizer, mainly due to the high flow velocity in this region. A relatively high erosion area close to the side and rear wall was also found because of the high concentration of large fly ash particles in this area. Interesting feature of fly ash flow in multidimensional complex boiler geometries such as concentration distributions for different fly ash particle sizes are also discussed.

Effects of Anode Serpentine Flow Fields on the Performance of μ-DMFC

2013 ◽  
Vol 562-565 ◽  
pp. 608-613
Author(s):  
Shuo Fang ◽  
Yu Feng Zhang ◽  
Wen Ting Fu ◽  
Xiao Wei Liu
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Simulation Analysis ◽  
Current Collector ◽  
Flow Fields ◽  
Cell Performance ◽  
Theory Analysis ◽  
Transfer Characteristics ◽  
Pressure Distributions ◽  
Serpentine Flow Field

This paper dedicated to the investigations of anode mass transfer characteristics of single serpentine, double serpentine, triple serpentine and quadruple serpentine flow fields to choose the best flow field structure. In this paper, the structure sizes of anode different serpentine flow fields have been designed to make the same duty cycle based on the theory analysis. Then a multi-physics 3D model has been established and simulated to analyze and compare mass transfer characteristics of every serpentine flow fields including pressure distributions, velocity distributions and concentration distributions. The current collector plates containing different serpentine flow fields have been made by micromachining. To verify the simulation analysis, the μ-DMFCs with different serpentine flow fields have been packaged and tested. Compared with the simulations, the experiment results come up with the conclusion that the performance of μ-DMFC with double serpentine flow field is a bit higher than those with others. In conclusion, though the cell performance with double serpentine flow field is a bit higher than that with others, its fabrication process is so complicated and the improvement of the performance is not obvious. It is concluded that increasing the serpentine channels of anode flow field doesn’t have many benefits on the cell performance.

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