RIB/Channel Effect on Cell Performance Under High Current Density Operation

2010 ◽  
Author(s):  
Yuichiro Tabuchi ◽  
Takeshi Shiomi ◽  
Osamu Aoki ◽  
Norio Kubo ◽  
Kazuhiko Shinohara
Keyword(s):  
Water Transport ◽  
Current Density ◽  
Liquid Water ◽  
Water Distribution ◽  
Numerical Study ◽  
High Current Density ◽  
Cell Performance ◽  
High Current ◽  
Numerical Validation ◽  
The Impact

Heat and water transport in polymer electrolyte membrane fuel cell (PEMFC) has considerable impacts on cell performance under high current density which is desired in PEMFC for automobiles. In this study, the impact of rib/channel, heat and water transport on cell performance under high current density was investigated by experimental evaluation of liquid water distribution and numerical validation. Liquid water distribution between rib and channel is evaluated by Neutron Radiography. In order to neglect the effect of liquid water in channel and the distribution of oxygen and hydrogen concentration distribution along with channel length, the differential cell was used in this study. Experimental results show that liquid water under channel was dramatically changed with Rib/Channel width. From numerical study, it is found that the change of liquid water distribution was strongly affected by temperature distribution between rib and channel. In addition, not only heat transport but also water transport through membrane also significantly affected cell performance under high current density operation. From numerical validation, it is concluded that this effect on cell performance under high current density could be due to the enhancement of back-diffusion of water through membrane.

Analysis of Mass Transport Loss in PEMFC Induced by Rib/Channel Geometry

2011 ◽  
Author(s):  
Yuichiro Tabuchi ◽  
Takeshi Shiomi ◽  
Yosuke Fukuyama ◽  
Osamu Aoki ◽  
Norio Kubo ◽  
...  
Keyword(s):  
Current Density ◽  
Liquid Water ◽  
Water Distribution ◽  
Electrochemical Reaction ◽  
High Current Density ◽  
Cell Performance ◽  
Ohmic Loss ◽  
High Current ◽  
Numerical Validation ◽  
Plane Direction

Key challenges to the acceptance of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) for automobiles are the cost reduction and its improvement in power density for compactness. In order to get the solutions for these issues, further improvement in the cell performance is required with high current density operation. In this study, the impacts of heat and water transport on the cell performance under high current density were investigated by experimental evaluation of liquid water distribution and numerical validation. Liquid water distribution in-plane direction was evaluated by neutron radiography. Furthermore, electrochemical reaction distribution was also evaluated by using inserted metal wires at anode, and then the experimental results were qualitatively validated by the numerical model. The experimental and numerical validation results revealed that significant increase in mass and ohmic loss was induced by temperature, liquid water, and electrochemical reaction distribution in-plane direction.

The Impact of Rib/Channel, Water and Heat Transport on Limiting Current Density

2008 ◽  
Author(s):  
Yuichiro Tabuchi ◽  
Norio Kubo
Keyword(s):  
Heat Transport ◽  
Water Transport ◽  
Current Density ◽  
Liquid Water ◽  
Proton Exchange ◽  
Cell Performance ◽  
Limiting Current ◽  
Promising Alternative ◽  
Limiting Current Density ◽  
The Impact

Proton exchange membrane fuel cells (PEMFCs) are regarded as a promising alternative clean power source for automotive applications. Key to the acceptance of PEMFCs for automobiles are cost reduction and power density for compactness. In order to meet these requirements, further improvement of cell performance is required. In particular, under higher current density operation, water and heat transport in PEMFC have strong effects on cell performance. In this study, the impact of Rib/Channel dimensions, heat and water transport on cell performance under high current density is investigated using the multiphase mixture model (M2 model), and the limiting current density is evaluated using a uniform test cell with 10cm2 active area and 24 straight channels. Limiting current densities were measured under different oxygen concentrations at 70°C and 70% relative humidity at both sides. In order to neglect the effect of liquid water in channels and the distribution of oxygen and hydrogen concentrations along the flow channel, large flow rates were introduced at both sides. Experimental results show a nonlinear relation between oxygen concentration in the channel and limiting current density. Numerically it is found that this nonlinear trend is caused by liquid water in the Rib region. In addition, it is also found that not only liquid water, but also heat transport and water transport through the membrane significantly affect the limiting current density. Finally, it is concluded that the combination analysis using limiting current experiments of uniform cell system and M2 model is very useful for fundamental understanding and for fuel cell design optimization.

The Nature of Flooding and Drying in Polymer Electrolyte Fuel Cells

2005 ◽  
Author(s):  
P. A. Chuang ◽  
A. Turhan ◽  
A. K. Heller ◽  
J. S. Brenizer ◽  
T. A. Trabold ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Current Density ◽  
Liquid Water ◽  
High Current Density ◽  
Liquid Water Content ◽  
Small Mass ◽  
Neutron Imaging ◽  
Small Range ◽  
High Current ◽  
Voltage Loss

Two different 50 cm2 fuel cells operated at high current density (1.3A/cm2–1.5A/cm2) were visualized using neutron imaging, and the liquid water content in the flow channels and diffusion media under the lands and channels was calculated and compared. At high current density with fully humidified inlet flow, a direct comparison between flooded and non-flooded conditions was achieved by increasing the fuel cell temperature over a small range, until voltage loss from flooding was alleviated. Results indicate that a surprisingly small mass of liquid water is responsible for a significant voltage loss. The deleterious effects of flooding are therefore more easily explained with a locally segregated flooded pore model, rather than a homogeneously flooded pore and blockage phenomenon. Anode dryout was similarly observed and quantified, and results indicate that an exceedingly small mass of water is responsible for significant voltage loss, which is consistent with expectations. The results presented help to form a more complete vision of the flooding loss and anode dryout phenomena in PEFCs.

Changes in Mechanical and Microstructural Properties of Magnesium Alloys Resulting from Superimposed High Current Density Pulses

2021 ◽  
Vol 1016 ◽  
pp. 385-391
Author(s):  
Eugen Demler ◽  
Alexander Diedrich ◽  
Andrej Dalinger ◽  
Gregory Gerstein ◽  
Sebastian Herbst ◽  
...  
Keyword(s):  
Magnesium Alloys ◽  
Current Density ◽  
High Current Density ◽  
Sheet Material ◽  
Compressive Load ◽  
Underlying Mechanism ◽  
Coarse Grained ◽  
High Current ◽  
Mechanical And Microstructural Properties ◽  
The Impact

Magnesium alloys are important engineering materials due to their good combination of strength and very low densities. However, the low ductility imposed by the hcp-lattice has thus far limited the application of magnesium alloys as sheet material. The use of the electroplastic effect offers a route to increase formability of magnesium alloys while being more energy efficient than conventional hot forming. The underlying mechanism (s) of this effect have not yet been fully understood. This study investigates the impact of high current density electrical pulses on magnesium alloys. Special consideration was given to the effect of the orientation of the applied electric current relative to the mechanical loading of the specimens. The results show that the mechanical properties of coarse-grained materials are more strongly affected by the current pulses than finer grained material. Applying the current parallel to the compressive load shows a more pronounced softening of the material than pulses applied perpendicular to the mechanical stress. Microstructure investigations revealed the formation of twinning solely in the interior of grains even at stresses below the yield point for both configurations.

The Numerical Study of Geometric Influence of Flow Channel Patterns on Performance of Proton Exchange Membrane Fuel Cells

2012 ◽  
Vol 9 (2) ◽  
Author(s):  
Chiun-Hsun Chen ◽  
Chang-Hsin Chen ◽  
Tang-Yuan Chen
Keyword(s):  
Flow Pattern ◽  
Current Density ◽  
Proton Exchange Membrane ◽  
Numerical Study ◽  
High Current Density ◽  
Proton Exchange ◽  
Bend Angle ◽  
Operating Voltage ◽  
Exchange Membrane ◽  
The Impact

This study numerically investigates how the geometry of flow pattern influences performance of proton exchange membrane fuel cell (PEMFC), and analyzes how these parameters lead to different distributions of model variables. The investigation focuses on the impact of different bend angle and width of serpentine flow channels and tests how they improve the performance. Three-dimensional simulations are carried out with a steady, two-phase, multicomponent and electrochemical model, using CFD-ACE+, the commercial CFD code. Through simulation with various bend angles and widths, the results show that the combination of 60 deg and 120 deg for flow pattern achieves the highest performance at low operating voltage regime, and flow pattern with wider bend width also produces more current at low operating voltages. Plots of current density indicate that high current density locates at the bending areas of the channels. Therefore, the output current densities of each pattern are improved from the change of bend angle and width.

Numerical Simulation of Full-Scale Cell and Stack at Very High Current Density: Influence of Heat and Liquid Water Saturation

2020 ◽  
Vol MA2020-02 (33) ◽  
pp. 2087-2087
Author(s):  
Takayuki Tsukamoto ◽  
Tsutomu Aoki ◽  
Hiroyuki Kanesaka ◽  
Keisuke Komiyama ◽  
Tsutomu Takayama ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Current Density ◽  
Liquid Water ◽  
Water Saturation ◽  
High Current Density ◽  
Full Scale ◽  
High Current ◽  
Very High
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