• Journal of Electrochemical Science and Technology
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• v.10 no.4
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• pp.345-360
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• 2019

Polymer Electrolyte Membrane Fuel Cells (PEMFC) is one of the leading advanced energy conversion technology for the use in transport. It generates water droplets through the catalytic processes and dispenses the water through the gas-flowed microchannels. The droplets in the dispensing microchannel experience g-forces from different directions during the operation in transport. Therefore, this paper reviews the computational modelling topics of droplet dynamics behaviour specifically for three categories, i.e. (i) the droplet sliding down a surface, (ii) the droplet moving in a gas-flowed microchannel, and (iii) the droplet jumping upon coalescence on superhydrophobic surface; in particular for the parameters like hydrophobicity surfaces, droplet sizes, numerical methods, channel sizes, wall conditions, popular references and boundary conditions.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.4
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• pp.386-392
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• 2014

The effective water management in a polymer electrolyte membrane fuel cell (PEMFC) is one of the key strategies for improving cell performance and durability. In this work, an ex situ measurement was carried out to understand the water droplet behavior on the surface of gas diffusion layer (GDL) as a fundamental study for establishing novel water management. For that purpose, simplified cell including one rib and two flow channels was designed and fabricated. Using this ex situ device, the water droplet emergence through the GDL of the PEMFC was emulated to understand liquid water transport through the porous diffusion medium. Through the visualization experiment, the emergence and growth of water droplets at the channel/GDL interface are mainly observed with the surface characteristics of GDL (SGL 10BA, 24BA) and rib when the liquid water passes through the GDL and is expelled to the flow channel. It is expected that the results obtained from this study can contribute to the better understanding on the water droplet behavior (emergence and removal) in the flow channels of PEMFC.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.217-223
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• 2016

In this paper, the movement of a liquid metal droplet in a channel by continuous electrowetting effect is analyzed. The channel is fabricated using two glass substrates and silicone rubber as spacers, and a mercury droplet and dilute sulfuric acid are added into the channel. The droplet is moved according to voltage applied at both ends of the channel through an electrolyte. According to the shape of the droplet and the applied voltage, the velocity of the droplet is changed. The velocity is proportional to the applied voltage and inversely proportional to the length of the droplet, both theoretically and experimentally. Contact angle hysteresis and a meniscus change were also found in the moving state. This implies the existence of a threshold in movement by Laplace pressure difference. The experiment indicated that the sliding angle was inversely proportional to the width of the droplet but that the voltage threshold was proportional to the width.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.76-83
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• 2013

Polymer electrolyte membrane fuel cells (PEMFCs) are regarded as a promising alternative to replace the existing automotive power sources. To get high performance and long-term durability for PEMFC systems, novel water management is essential. To this end, a comprehensive understanding of dynamics of the liquid water droplets within an operating PEMFC plays an important role. In this work, direct visualization of dynamic behaviors of the water droplet in the ex situ unit flow channel of a PEMFC including gas diffusion layer (GDL) is carried out as one of the fundamental studies for novel water management. Water droplet dynamics such as the movement and growth of liquid water droplets are mainly presented. Effects of GDL characteristics and inlet air flow rate on the water droplet transport and its removal from the flow channel are also discussed. The data obtained in this study can contribute to build up the fundamental operating strategy including balanced water removal capacity for automotive PEMFC systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.325-326
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• 2012

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.379-382
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• 2006

We are investigating the effect of particle on electrowetting, and this paper reports the experimental results obtained until now. The experiment was performed for different particle sizes, electrolyte concentration, and AC frequencies. The problem is quite complicated by various factors, such as the existence of surfactant in suspension and sedimentation of particles. We could not draw a concrete conclusion on the effect of particles, and it needs further investigations. We also report interesting phenomena observed during the experiment. It includes the droplet generation at the edge of a droplet, pseudo-bistability of electrowetting, flow generation inside a droplet, and the chain formation of particles inside a droplet.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.82-88
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• 2008

This paper describes the influence of the bridge formed between electrodes by electrolyte for tracking process. Electrolytes is made by IEC(International Electrotechnical Commission) 60589, NaCl added to deionized water as each 1, 3, 5[wt%]. The used test equipment is made according to KS(Korean Industrial Standard) C IEC 00112. It is investigated voltage, current, value of resistance and thermal image when bridge formed between electrodes on tracking process. As a result, as conductivity of electrolyte gets bigger as Joule's heat on bridge also gets bigger. But It is not over electrolyte's boiling point due to evaporation heat of electrolyte. However as conductivity of electrolyte gets bigger as the necessary time of dry band gets shorter. So dry band is existed more long time between ahead of droplet to next droplet and discharge chance at dry band gets much. Therefore tracking process gets faster.

• Electrical & Electronic Materials
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• v.1 no.1
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• pp.70-77
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• 1988

This paper describes the influence of the electrode materials, moisture content, electrolyte density, temperature, surface state, ion absorbent on the C.T.I of phenolic resin by the I.E,C, 112 method. C.T.I are increased for electrode materials with low hydrogen overvoltage and high soluble point. Increusing moisture content of samples increased by logarithmical on the droplet number to tracking breakdown. Increasing electrolyte temperature region above 70-80(.deg.C) decreased hydrogen over-voltage, following the density changes are decreased by C.T.I=1/aD$^{2}$-bD+C.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.491-492
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• 2012

• 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.