• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.407-410
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• 2006

Selection of flow channel in the separation plate of PEMFC is very important parameter to improve its performance and reduce parasite loss. Flow patterns in the channel have great influence on the transport of hydrogen and all and water generated from electrochemical reaction in diffusion layer In this study, fluid flow in flow channel with parallel and interdigitated patterns are simulated three dimensionally on full flow domain including anode and cathode electrode together. The numerical results show that the fuel cell with interdigitated flow channel represents better performance than that with parallel flow channel due to its strong convective transport across the gas diffusion layer. But the pressure drop in parallel flow channel is much more than that in nterdigitated flow channel. The effect of temperature and stoichiometric number on performance can be calculated and analyzed as well.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.93-98
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• 2008

To investigate the characteristics of water droplet on the gas diffusion layer from both top-view and side-view of the flow channel, a rig test apparatus was designed and fabricated with prism attached plate. This experimental device is used to simulate the growth of single liquid water droplet and its transport process with various air flow velocity and channel height. The contact angle hysteresis and height of water droplet are measured and analyzed. It is found that droplet tends towards to be instable by decreasing channel height, increasing flow velocity or making GDL more hydrophobic. Also, the simplified force balance model matches with experimental data only in a restricted range of operating conditions and shows discrepancy as the air flow velocity and channel height increases.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.3
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• pp.1-8
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• 2008

We present a model for simulating high energy laser heating of metal for ignition of energetic materials. The model considers effect of ablation of steel plate with long laser pulses and continuous lasers of several kilowatts and the thermal response of well-characterized high explosives for ignition. Since there is enough time for the thermal wave to propagate into the target and to create a region of hot spot in the high explosives, electron thermal diffusion of ultra-short (femto- and pico-second) lasing is ignored; instead, heat diffusion of absorbed laser energy in the solid target is modeled with thermal decomposition kinetic models of high explosives. Numerically simulated pulsed-laser heating of solid target and thermal explosion of RDX, TATB, and HMX are compared to experimental results. The experimental and numerical results are in good agreement.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.89-94
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• 2003

For the development of high efficiency and low emission combustion systems, high temperature air combustion technology has been tested by utilizing preheated air over 1100 K and exhaust gas recirculation. In this system, combustion air is diluted with large amount of exhaust gases ($N_2$, $CO_2$), such that the oxygen concentration is relatively low in the reaction zone, leading to low flame temperature. Since, the temperature fluctuations and sound emissions form the flame are small and flame luminosity is low, the combustion mode is expected to be flameless or mild combustion. Experiment was performed to investigate the turbulent flame structure and $NO_X$ emission characteristics in the high temperature air combustion focused on coflowing jet diffusion flames which has a fundamental structure of many practical combustion systems. The effect of turbulence has also been evaluated by installing perforated plate in the oxidizer inlet nozzle. LPG was used as a fuel. Results showed that even though $NO_X$ emission is sensitive to the combustion air temperature, the present high temperature air combustion system produce low $NO_X$ emission because it is operated in low oxygen concentration condition in excess of dilution.

• Journal of the Korean Society of Combustion
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• v.8 no.3
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• pp.15-23
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• 2003

Partial quenching structure of turbulent diffusion flames in a turbulent mixing layer is investigated by the method of flame hole dynamics in order to develop a prediction model for turbulent flame lift off. The essence of flame hole dynamics is derivation of the random walk mapping, from the flame-edge theory, which governs expansion or contraction of flame holes initially created by local quenching events. The numerical simulation for flame hole dynamics is carried out in two stages. First, a direct numerical simulation is performed for constant-density fuel-air channel mixing layer to obtain the turbulent flow and mixing fields, from which a time series of two dimensional scalar dissipation rate array is extracted at a fixed virtual flame surface horizontally extending from the end of split plate to the downstream. Then, the Lagrangian simulation of the flame hole random walk mapping projected to the scalar dissipation rate array yields temporally evolving turbulent extinction process and its statistics on partial quenching characteristics. The statistical results exhibit that the chance of partial quenching is strongly influenced by the crossover scalar dissipation rate while almost unaffected by the iteration number of the mapping that can be regarded as a flame-edge speed.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.78-85
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• 2006

Selection of flow channel in the separation plate of PEMFC is very important parameter to improve its performance and reduce parasite loss. Flow patterns in the channel have great influence on the transport of hydrogen and air and removal of water generated from electrochemical reaction in diffusion layer. In this study. fluid flow in flow channel with parallel and interdigitated patterns are simulated three dimensionally on full flow domain including anode and cathode channel together. The numerical results show that the fuel cell with interdigitated flow channel represents better performance than that with parallel flow channel due to its strong convective transport across the gas diffusion layer. But the pressure drop in parallel flow channel is much more than that in interdigitated flow channel. And effects of temperature and stoichiometric number on performance can be calculated and analyzed as well. Nomenclature.

• Journal of the Korean institute of surface engineering
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• v.46 no.5
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• pp.192-196
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• 2013

Stainless steels (AISI 316L) are carburized by Inductively coupled plasma using $CH_4$ and Ar gas. The ${\gamma}_c$ phase(S-phase) is formed on the surface of stainless steel after carburizing process. The XRD peak of carburized samples is shifted to lower diffracting angle due to lattice expansion. Overall, the thickness of ${\gamma}_c$ phase showed a linear dependence with respect to increasing temperature due to the faster rate of diffusion of carbon. However, at temperatures above 500, the thickness data deviated from the linear trend. It is expected that the deviation was caused from atomic diffusion as well as other reactions that occurred at high temperatures. The interfacial contact resistance (ICR) and corrosion resistance are measured in a simulated proton exchange membrane fuel cell (PEMFC) environment. The ICR value of the carburized samples decreased from 130 $m{\Omega}cm^2$ (AISI 316L) to about 20 $m{\Omega}cm^2$. The sample carburized at 200 showed the best corrosion current density (6 ${\mu}Acm^{-2}$).

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.194-204
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• 2023

Models based on diffusion-limited aggregation (DLA) have been extensively used to explore the mechanisms of dendritic particle aggregation phenomena. The physical and chemical properties of systems in which DLA aggregates emerge are given in their fractal. In this paper, we present a comprehensive study of the growth of electrodeposited copper dendrites in flat plate electrochemical cells from a fractal perspective. The effects of growth time, applied voltage, copper ion concentration, and electrolyte acidity on the morphology and fractal dimension of deposited copper were examined. 'Phase diagram' set out the variety of electrodeposited copper fractal morphology analysed by metallographic microscopy. The box counting method confirms that the electrodeposited dendritic structures manifestly exhibit fractal character. It was found that with the increase of the voltage and copper ion concentration. The fractal copper size becomes larger and its morphology shifts towards a dendritic structure, with the fractal dimension fluctuating around 1.60-1.70. In addition, the morphology of the deposited copper is significantly affected by the acidity of the electrolyte. The increase in acidity from 0.01 to 1.00 mol/L intensifies the hydrogen precipitation side reactions and the overflow path of hydrogen bubbles affects the fractal growth of copper dendrites.

• Fire Science and Engineering
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• v.31 no.3
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• pp.79-87
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• 2017

Sandwich panels which are having the both sides are bonded with a heat insulating material with an iron plate are used as factories, warehouse structures as advantages of convenience in construction at economic efficiency of material cost. However, in a panel structure constructed by continuous joining of sandwich panels, a joint portion where a panel and a panel are connected is generated. The joint part is a part which is easily vulnerable to fire because flames easily flow into the melting and deformation of the iron plate during fire. The flames flowing into the panel induce diffusion of fire by rapid burning, causing damage of human life and property. In this research, we developed a flame spread prevention plate to prevent spreading of sandwich panel. This is an improvement of the workability by the anti-spreading construction method of the existing previous research, it can be applied independently to the connecting part where the panel and the panel are coupled, designed to prevent inflow and spreading of flame did. The actual fire test of the test method of KS F ISO 13784-1 of the sandwich panel specimen was conducted and the burning behavior corresponding to the presence or absence of application of the flame spread prevention plate was grasped at the panel connection part and its effect was measured. Inserting a fire spreading plate into the test result panel connecting part is measured by delaying the flashover, prevention of collapse of the specimen, and temperature rise of the opening, effectively improving the fire safety of the panel structure It was confirmed as a method that can be secured. It is judged that panel structure will contribute to ensuring fire safety by applying the fire spread prevention construction method of various methods ensuring the workability and economy of panel connection vulnerable to fire.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.342-348
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• 2003

Ultrasonic backscattering profiles of the Zr plates(with a thickness of 1.32mm) with/without Be-Zr alloy layer(with a thickness of $100{\mu}m$) were measured at various incidence positions to evaluate the characteristics of Be diffusion layer. Four principal subprofiles were observed in the backward ultrasound radiated from leaky Lamb waves. The angles and the intensities of the subprofile peaks decreased by the stiffening effect of Be layer. Generation and change of the subprofiles were explained by the acoustical property, collective group velocity and leaky factor difference of the plates under consideration. Backward radiation subprofiles turned out to be an useful method for evaluating thin diffusion layers on plates.