• 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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• 2007.11a
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• pp.23-26
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• 2007

Liquid water in flow channel is an important factor that limits the steady and transient performance of PEM fuel cells. A computational fluid dynamics study based on the volume-of-fluid (VOF) multi-phase model is conducted to understand the transport behavior of liquid water in flow channel. The liquid water transport in $180^{\circ}$ bends is investigated and the effect of chamfering is discussed. The effect of wall adhesion is also considered by varying the contact angle of channel surfaces. The result of this study is believed to provide a useful guideline for design optimization of flow patterns or channel configurations of PEM fuel cells.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.9-14
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• 2008

The effects of baffles in PEM fuel cell with parallel flow channel has been simulated by using conmmercial program. The simulation has been conducted through the channel and there are four different heights of baffles, No Baffle($H_b$=0), Partially Blocked Baffle(0.25, 0.5, 0.75), Fully Blocked Baffle(1) conditions. The result shows that current density changes while placing a baffle at the various positions along the channel. Current density with a single baffle is higher than that without baffle and current density using Fully Blocked Baffle(FBB) is much higher than current density using Partially Blocked Baffle(PBB). When the baffle is closer to outlet of the channel, current density increases. It is found that pressure is related to current density. If the pressure is higher, the better performance will be expected.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1314-1321
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• 2019

In case of multiple failure scenario, such as LOCA with ECCS failure, the decay heat continues to raise the reactor core temperature, eventually leading to the core voiding. In such scenario the convective heat transfer becomes poor and the majority of the heat transfer from fuel bundle takes place by radiation mode. During this abnormal working condition, if the channel pressure is less than 1 MPa, the PT sags and come in contact with the CT. This results in high rate of heat transfer from contact location to moderator. The present paper aims to capture the temperature profile over a simulated nuclear channel during such scenario at a steady state temperature of $600^{\circ}C$ (Centre pin) at two different configurations of PT i.e. PT concentric with CT and PT contact with CT. The results showed that the bottom nodes of all the components (Fuel bundle, PT and CT) of the simulated channel was greatly influenced by the PT/CT contact. Moreover, higher temperature were observed at top nodes of the PT and outer pins of the fuel bundle. However, no significant variation in temperatures were obtained in fuel bundle and CT in concentric condition.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.6
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• pp.554-559
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• 2015

Single cell of PEMFC (polymer electrolyte membrane fuel cell) is composed of bipolar plates, gasket, GDL and the MEA. Bipolar plate's function is the collecting electricity, helping oxygen/hydrogen gas diffuse evenly and draining the water and heat. In this work, we have conducted experiments to low contact resistance and improve the performance of a $25cm^2$ single cell by using metal forms. We have following experimental cases: 1) Conventional graphite serpentine channel bipolar plate; 2) Channel-less bipolar plate with nickel(Ni) based metal foam which coated by various materials. We focused the difference in contact resistance and performance of the single cell with metal foam depending on various coating materials. The experimental results show the similar performance of single cells between with serpentine channel bipolar plates and with channel-less bipolar plate using metal foams. In addition, single cell with metal foam shows potential to higher performance than conventional channel.

• Journal of the Korea Safety Management & Science
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• v.20 no.4
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• pp.7-13
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• 2018

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.550-556
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• 2022

In this study, the flow uniformity was analyzed by performing numerical analysis on the 1 kWe internal manifold type solid oxide fuel cell stack according to the channel height of the separator. Also, it was examined by varying the fuel utilization rate and oxygen utilization rate. From the calculation results, we found that as the channel height of the separator decreased, the pressure drop increased exponentially. In addition, it was found that as the channel height of the separator decreased, the gas flow resistance inside the unit cell increased, and the flow resistance increased the pressure drop, thereby improving the flow uniformity inside the stack. Finally, the calculation results showed that as the fuel and oxygen utilization increased, the flow uniformity also improved.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.74-82
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• 2012

Proton exchange membrane fuel cell performance is changed by the complicated physical phenomenon. In this study, water discharge performance of proton exchange membrane fuel cell were performed numerically to compare serpentine channel flow fields of 5-pass 4-turn serpentine and 25 $cm^2$ reaction surface between with and without sub-channel at the rib. Through the supplement of sub channel flow field, it is shown from the results that water removal characteristic inside channel improves because the flow direction of under-rib convection is changed into the sub channel. Reacting gases supplied from entrance disperse into sub channel flow field and electrochemical reaction occurs uniformly over the reaction surface. The results obtained that total current density distributions become uniform because residence time of reacting gases traveling to sub-channel flow field is longer than to main channel.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.1982-1990
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• 2022

The purpose of this study was to verify the possibility of fuel rod pattern analysis in a fresh fuel assembly using the Yonsei single-photon emission computed tomography (YSECT) system. The YSECT system consisted of three main parts: four trapezoidal-shaped bismuth germanate scintillator-based 64-channel detectors, a semiconductor-based multi-channel data acquisition system, and a rotary stage. In order to assess the performance of the prototype YSECT, tomographic images were obtained for three representative fuel rod patterns in the 6 × 6 array using two representative image-reconstruction algorithms. The fuel-rod patterns were then assessed using an in-house fuel rod pattern analysis algorithm. In the experimental results, the single-directional projection images for those three fuel-rod patterns well discriminated each fuel-rod location, showing a Gaussian-peak-shaped projection for a single 10 mm-diameter fuel rod with 12.1 mm full-width at half maximum. Finally, we successfully verified the possibility of the fuel rod pattern analysis for all three patterns of fresh fuel rods with the tomographic images obtained by the rotational YSECT system.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.6
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• pp.492-498
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• 2009

Six sigma methode was applied for optimization of flow field design of a proton exchange membrane fuel cell (PEMFC). The optimization between number of channel and channel/rib width was suggested in this paper with six sigma method. With the help of six sigma design of experiment (DOE) the number of experiments may be reduced dramatically. The fuel cell channel design optimization with results of these experiments with a 100 $cm^2$ serpentine flow field indicates a optimization data for a given constant operating conditions.