• 한국유체기계학회 논문집
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• 제15권1호
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• pp.64-69
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• 2012

Currently axial flow compressor is used primarily in a large power generation gas turbine. In this paper,the main factors to be considered when designing a axial flow compressor were compared to those of a small power generation gas turbine(DGT-5). The main design parameters was examined in the aspect ratio, solidity, as well as reaction, diffusion factor, incidence angle, etc. The results in case of a small compressor are showed a regular pattern but there were not found any specific design patterns for a large class compressor.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.553-554
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• 2006

This paper presents the effects of different operating parameters on the performance of a proton exchange membrane (PEM) fuel cell by a three-dimensional computational fluid dynamics (CFD) model. The effects of different operating parameters on the performance of PEM fuel cell studied using pure hydrogen on the anode side and air on the cathode side. The various parameters are temperatures, pressures, humidification of the gas steams and various combinations of these parameters. In addition, geometrical and material parameters such as the gas diffusion layer (GDL) thickness and porosity as well as the ratio between the channel width and the land area were investigated.

• 대한기계학회논문집
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• 제16권6호
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• pp.1171-1178
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• 1992

본 연구에서는 직접접촉식 열교환기를 이용한 실험을 통하여 열교환기 설계에 가장 중요한 열교환기 단위 체적당 총괄 열전달 계수를 시스템의 작동조건에 따라 구 하여 실제 설계자료로 이용하는 데 그 목적이 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제13권2호
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• pp.64-77
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• 1989

In this study, the experiments were carried out for the purpose of establishment of aluminium cementation to steel surface by diffusible heat treatment after making the coated film onto the substrate by arc spray method. Also, the microstructure and mechanical properties of the cementation layer produced by this study were inspected for various heat treatment and spraying conditions. Main results obtained are as follow ; 1. The coating film characteristics which have excellent errosion-resistance, high temperature oxidation-resistance are obtained by aluminium penetration heat treatment after making the sprayed aluminum coating film onto the steel substrate. 2. Aluminium diffusion penetration takes place at higher temperature than 660.deg.C, and the more heat treatment time and the higher heat treatment temperature adopted, the deeper diffusion layer obtained. 3. Insert gas arc spraying using argon gas as the carrier gas higher improvement of mechanical property than that of compressed air environment. 4. The coating film characteristics appeared to be improvement of adhesive property, porosity plugging effect by heat treatment in air environment.

• 설비공학논문집
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• 제25권2호
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• pp.64-69
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• 2013

The structure of pore network of gas diffusion layers (GDLs) in PEMFCs plays a critical role in determining the transport phenomena of reaction gas as well as generated water. In addition, the interactive characteristics between water and surface of pore are no less important than the structural characteristics of pore network. In this study, porometric investigation is conducted for two kinds of GDL using method of standard porosimetry which enable to distinguish hydrophobic pores from hydrophilic pores of GDLs. The porosity of TGPH-120 decreases by 6% by adding 30 wt.% of PTFE, but the porosity of hydrophilic pores decreases by 12%. The relation of $p_c-S_{nw}$ varies with the addition of PTFE, especially at low $p_c$.

• 한국포장학회지
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• 제19권2호
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• pp.61-65
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• 2013

Modified atmosphere (MA) of reduced $O_2$ and elevated $CO_2$ concentrations has been used for keeping the quality of fresh produce and extending the shelf life. As a way to attain the beneficial MA package around the produce, a gas diffusion tube or perforation can be attached onto the container and controlled on real time in its opening/closing responding to $O_2$ and $CO_2$ concentrations measured by gas sensors. The timely-controlled opening of the gas diffusion tube can work in harmony with the produce respiration and help to create the desired MA. By use of the mathematical modeling, the effect of tube dimension on the controlled container atmosphere was figured out in this study. Spinach and king oyster mushroom were used as typical commodities for designing the model container system (0.35 and 0.9 kg in 13 L, respectively) because of their respiration characteristics and the optimal MA condition ($O_2$ 7~10%/$CO_2$ 5~10% for spinach; $O_2$ 2~5%/$CO_2$ 10~15% for mushroom). With a control logic for the gas composition to stay as close as possible to optimum MA window without invading injurious low $O_2$ and/or high $CO_2$ concentrations, the atmosphere of the sensor-controlled container could stay at its lower $O_2$ boundary or upper $CO_2$ limit under certain tube dimensional conditions. There were found to be the ranges of the tube diameter and length allowing the beneficial MA. The desired range of the tube dimension for spinach consisted of combinations of larger diameter and shorter length in the window of 0.3~2 cm diameter and 0.2~10 cm length. Similarly, that for king oyster mushroom was combinations of larger diameter and shorter length in the window of 0.9~2 cm diameter and 0.2~3 cm in length. Clear picture on generally affordable tube dimension range may be formulated by further study on a wide variety of commodity and pack conditions.

• Korean Chemical Engineering Research
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• 제50권3호
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• pp.556-561
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• 2012

본 연구에서는 고분자형 연료전지(PEMFC) 내의 기체확산층(GDL)에서의 물질 거동 전산해석을 통하여 GDL 물성이 전지성능에 미치는 영향을 알아보았다. GDL 내에서 기상의 산소와 액상의 물의 거동을 계산하기 위하여 multi-phase mixture($M^2$) 모델을 사용하였다. GDL의 접촉각, 기공도, 기체투과도, 두께에 변화를 주며 계산을 실시하여 GDL 내에서의 물질 거동의 변화를 확인 하였고, GDL 물성이 전지성능에 미치는 영향을 파악하였다. 전산해석 결과, GDL의 접촉각과 기공도가 커지고, 두께가 얇아짐에 따라 물질전달 저항이 감소하여 GDL과 촉매층 사이의 계면에서의 물포화도가 낮아지고 산소농도는 증가하여 전지성능이 향상되는 것을 확인하였다.

• 대한기계학회논문집B
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• 제28권2호
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• pp.146-153
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• 2004

A Promising new approach to achieve low pollutant emissions and improvement of flame stability is tested experimentally using a cyclone jet hybrid combustor employing both premixed and diffusion combustion mode. Three kinds of nozzle are tested for mixing enhancement of fuel and air. The LNG (Liquified Natural Gas) is used as a fuel. The combustor is operated by two methods. One is DC (Diffusion Combustion) mode generated swirl flow by air as general swirl combustor, and the other is HC (Hybrid Combustion) mode. The HC mode consists of diffusion jet flame of axial direction and premixed cyclone flame of tangential direction in order to stabilized the diffusion jet flame. The results showed that the flame stability of HC mode is significantly enhanced than that of DC mode through the change of mixing characteristics by modifications of fuel nozzle. In addition, the reductions of CO and NOx emission in HC mode, as compared with that for the DC mode, is large than about 50% in stable region. Also, even using the low calorific fuel as $CO_2$-blended gas, it is identified that the cyclone jet hybrid combustor has the high performance of flame stability.

• 공업화학
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• 제25권2호
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• pp.147-151
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• 2014

많은 고분자 공정에서 고분자에서의 유기 용매와 같은 저분자 물질의 확산은 중요하다. 고분자에서의 저분자 물질의 이동은 중합 반응기의 효율성과 제조된 고분자의 특성을 결정한다. 공정을 설계하고 최적화하는데 중요한 물성값은 고분자/용매 상호확산 계수이다. 용매의 농도가 매우 낮은 무한희석 상태에서의 고분자/용매 계의 무한확산계수를 측정하기 위해서 capillary column inverse gas chromatography (CCIGC) 기법이 흔히 사용된다. 이 기법을 사용하면 비교적 짧은 시간에 확산계수와 분배계수를 측정하는 것이 가능하다. 본 연구에서는 CCIGC 기법을 사용해서 styrene/butadiene/styrene (SBS) 블록 공중합체에서 환형 구조를 가지는 용매의 확산계수와 분배계수를 다양한 온도 범위에서 측정하였다.

• 전기화학회지
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• 제8권2호
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• pp.106-114
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• 2005

This article covers the theoretical ac-impedance models for the analysis of oxygen reduction on the porous cathode electrode f3r solid oxide fuel cell (SOFC). Firstly, ac-impedance models were explained on the basis of the mechanism of oxygen reduction, which were classified into the rate-determining steps; (i) adsorption of oxygen atom on the electrode surface, (ii) diffusion of adsorbed oxygen atom along the electrode surface towards the three-phase (electrode/electrolyte/gas) boundaries, (iii) surface diffusion of adsorbed oxygen atom m ixed with the adsorption reaction of oxygen atom on the electrode surface and (iv) diffusion of oxygen vacancy through the electrode coupled with the charge transfer reaction at the electrode/gas interface. In each section for ac-impedance model, the representative impedance plots and the interpretation of important parameters attributed to the oxygen reduction reaction were explained. Finally, we discussed in detail the applications of the proposed theoretical ac-impedance models to the real electrode of SOFC system.