• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.625-632
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• 2012

The objective of this paper is to demonstrate the cathode channel flooding effects at different stoichiometries in proton exchange membrane (PEM) fuel cells by using visualization techniques. The phenomena of liquid water formation and removal caused by current variations were also examined experimentally. Tests were conducted at cathode stoichiometries of 1.5 and 2.0, and the anode stoichiometry was fixed at 1.5. It is found that at an air-side stoichiometry of 2.0, liquid water begins to form and the flooding occurs faster than at an air-side stoichiometry of 1.5. Also, when the air-side stoichiometry of 1.5 is maintained, the dry-out phenomena is observed in the dry-out area 7.8 A following the field of flooding. Thus, a stoichiometry of 1.5 produced better performance in terms of membrane electrode assembly (MEA) durability and hydrogen ion conductivity than did a stoichiometry of 2.0, in which dry-out occurs beyond 8A.

• 한국전기화학회:학술대회논문집
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• 2005.04a
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• pp.62-62
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• 2005

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.539-542
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• 2007

The transient response of PEMFC (proton exchange membrane fuel cell) is important criteria in the application of PEM fuel cell to real automotive system. In this work, using a transparent unit PEM fuel cell, the transient response and cathode flooding during load change are investigated. The cell voltage is acquired according to the current density change($0.3Acm^2$ to $0.6A/cm^2$) under various stoichiometry conditions and different flooding intensities, Also the cathode gas channel images are obtained by CCD imaging system simultaneously. The different level of undershoots appeared at the moment of load changes under different cathode stoichiometries and flooding intensities. The correlation of the dynamic behavior with stoichiometry and cathode flooding is induced from the results of these experiments.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.95.2-95.2
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• 2005

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.1
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• pp.35-41
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• 2010

Water management is an important issue of PEM fuel cell operation. Water is the product of the electrochemical reactions inside fuel cell. If liquid water accumulation becomes excessive in a fuel cell, water columns will clog the gas flow channel. This condition is referred to as flooding. A number of researchers have examined the water removal methods in order to improve the performance. In this paper, a new water removal method that investigates the use of vibro-acoutic methods is presented. Piezo-actuators which are devices to generate the flexural wave are attached at the end of a cathode bipolar plate. Flexural wave is used to impart energy to resting droplets and thus cause movement of the droplets in the direction of the traveling wave.

• New & Renewable Energy
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• v.3 no.2 s.10
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• pp.24-30
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• 2007

The transient response of PEMFC (proton exchange membrane fuel cell) is important criteria in the application of PEM fuel cell to real automotive system. In this work, using a transparent unit PEM fuel cell, the transient response and cathode flooding during load change are investigated. The cell voltage is acquired according to the current density change($0.3Acm^2$ to $0.6A/cm^2$) under various stoichiometry conditions and different flooding intensities, Also the cathode gas channel images are obtained by CCD imaging system simultaneously. The different level of undershoots appeared at the moment of load changes under different cathode stoichiometries and flooding intensities. It takes about 1s that the product water comes up onto the flow channel so that oxygen supply is temporarily blocked which causes voltage loss in that "undershoot". The correlation of the dynamic behavior with stoichiometry and cathode flooding is induced from the results of these experiments.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.5
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• pp.390-396
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• 2009

The flooding, especially in channel, is one of the critical issue to put proton exchange membrane fuel cell (PEMFC) to practical use. In this paper, channel flooding was investigated the pressure difference at cathode channel outlet. A ratio of pressure difference changes to 25, 50% as its variation rate. The pressure variable rate is reflected in dimensionless number FN. As a result, modified dimensionless number $FN^*$ correctly predicted the channel flooding. This study analyzes that a variety of pressure difference is how to affect flooding at the cathode of the PEMFC.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.326-329
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• 2005

Proton exchange membrane (PEM) should be sufficiently hydrated with proper water management to maintain a good ionic conductivity and performance of a PEM fuel cell. However. cathode flooding resulting from excess water can impede the transport of reactants and hence deteriorate the fuel cell performance. For the PEM fuel cell to be commercially viable as vehicle or portable applications, the flooding on the cathode side should be minimized during the fuel cell operation. In this study, visualization technique was applied to understand the cathode flooding phenomena on the cathode side of a PEM fuel cell. To this end. a transparent PEM unit fuel cell wi th an act ive area of $25cm^2$ was designed and manufactured to allow for the visualization of cathode channel with performance characteristics. Two-phase flow resulting from the electro-chemical reaction of fuel cell was investigated experimentally. The images photographed by CCD camera with cell operating temperatures $(30\~50^{\circ}C)$ were presented. Results indicated that the flooding on the cathode side first occurs near the exit of cathode channel. As the operating temperature of fuel cell increases. it was found that liquid water droplets tend to evaporate easily and it can have an influence on lowering the flooding level. It is expected that this study can effectively contribute to the detailed researches on modeling water transport of an operating PEM fuel cell including two-phase flow phenomena.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.101-104
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• 2006

Water management is considered to be one of the main issues to be addressed for the performance improvement of proton exchange membrane (PEM) fuel cell. For good water management, the detailed information on the water distribution inside an operating PEM fuel cell should be available to main an adequate level of hydration in the PEM While avoiding performance decline due to liquid rater flooding. For the PEM fuel cell to be commercially viable as vehicle applications, the flooding on the cathode side should be minimized during the fuel ceil operation. In this study to investigate cathode flooding and its relation with temperature distribution in flow channels, visualization study was performed on the cathode side of a PEM fuel cell. For the direct visualization of temperature field and water transport in cathode flow channels, a transparent cell was designed and manufactured using quartz window. Water transport and its two-phase flow characteristics in flow channels were investigated experimentally. Also, the visualization of temperature distribution In cathode flow channels was made by using IR camera. Results indicated that the temperature rise near the exit of cathode flow channel was found. It is found that this area corresponds to the flooding area from both temperature and flooding visualization results It is expected that this study can effectively contribute to get the detailed data on water transport linked with heat management during the operation of a PEM fuel cell

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.476-483
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• 2012

Proper water management is crucial for the efficient operation of polymer electrolyte membrane (PEM) fuel cell. Especially, for automotive applications, A novel water management that can avoid both membrane dry-out and flooding is a very important task to achieve good performance and efficiency of PEM fuel cells. The aim of this study is to investigate the liquid water behavior on the gas diffusion layer (GDL) surface and in the cathode flow channel of a PEM unit fuel cell under flooding conditions. For this purpose, a transparent unit fuel cell is devised and fabricated by modifying the conventional PEM fuel cell design. The results of water droplet behavior under flooding conditions are mainly presented. The water distributions in the cathode flow channels with cell operating voltage are also compared and analyzed. Through this work, it is expected that the data obtained from this fundamental study can be effectively used to establish the basic water management strategy in terms of water removal from the flow channels in a PEM fuel cell stack.