• Corrosion Science and Technology
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• 제21권2호
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• pp.121-129
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• 2022

A study on water-based epoxy coated on mild steel using the electroplating method was conducted to optimize the process parameters for dry film thickness to achieve superior paint quality at optimal cost in an automotive plant. The regression model was used to adjust various parameters such as electrode voltage, bath temperature, processing time, non-volatile matter, and surface area to optimize the dry film thickness. The average dry film thickness computed using the model was in the range of 15 - 35 ㎛. The error in the computed dry film thickness with reference to the experimentally measured dry film thickness value was - 0.5809%, which was well within the acceptable limits of all paint shop standards. Our study showed that the dry film thickness on mild steel was more sensitive to electrode voltage and bath temperature than processing time. Further, the presence of non-volatile matter was found to have the maximum impact on dry film thickness.

• 대한토목학회논문집
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• 제32권3D호
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• pp.223-229
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• 2012

도로 포장면과 타이어 사이의 마찰 저항을 미끄럼 저항이라고 한다. 미끄럼 저항은 도로 안전에 매우 중요한 요소이며, 다양한 요인이 복합적으로 작용한다. 미끄럼 저항 측정법의 한계를 극복하기 위해 컴퓨터 모델링을 이용한 해석 수행 결과, 속도가 증가하거나 수막두께가 두꺼울수록 미끄럼 저항은 감소하였다. 해석 결과를 이용해 수막두께와 속도에 따라 수막 위를 주행하는 타이어에 발생하는 양력을 계산할 수 있으며, IFI(International Friction Index) 미끄럼 저항 예측모델과 실측 미끄럼 저항과의 차이를 줄이기 위해 양력을 반영한 수정 IFI 미끄럼 저항 예측모델을 개발하였다. 예측모델과 실측 데이터의 상관관계 분석 결과, 기존 IFI 예측모델의 $R^2$는 0.49로, 수정 IFI 예측모델의 $R^2$는 0.64로 나타나 수정 IFI 예측모델이 기존모델에 비해 예측 효과가 우수하였다. 포장면의 상태에 따른 수막두께를 수정 예측모델에 반영할 경우 더욱 정확한 예측모델을 얻을 수 있을 것이다.

• 상하수도학회지
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• 제13권1호
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• pp.72-80
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• 1999

Separation of VOCs(Volatile Organic Compounds) in Water Using Activated Carbon is known to be effective. Activated Carbon has been and will be employed in many water treatment plants. Simplified plug flow homogeneous surface diffusion model(PFHSDM) has been used to predict adsorption of organic matter. Finite Element Method(FEM) was used to analyze the model. Out of water quality control substances, benzene, toluene and tetrachloroethylene were used in the small column test. Film diffusion coefficients and surface diffusion coefficients were obtained from the column test, and were compared with the modeling results. Mc Cune, Williamson, William and Kataoka model, were compared with film diffusion coefficients obtained in the test. McCune model was fitted best for those VOCs used in this experiment. Film diffusion coefficients of VOCs obtained were benzene 0.265 cm/min, toluene 0.348 cm/min and tetrachloroethylene 0.298 cm/min. Surface diffusion coefficients of VOCs obtained were benzene $6.36{\times}10^{-8}cm^2/min$, toluene $3.20{\times}10-8cm2/min$, and tetrachloruethylene $4.94{\times}10^{-8}cm^2/min$.

• Journal of Biosystems Engineering
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• 제15권1호
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• pp.14-22
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• 1990

For efficient use of solar energy in plastic greenhouse, thermal storage system was developed. The system was constructed with the counter-flow type air-water heat exchanger using a thin polyethylene film as a medium of heat exchange parts. Experiments were carried out to investigate the heat exchange rate, optimum water flow rate, overall heat transfer coefficient, and the effectiveness of the counter-flow type air-water heat exchanger with polyethylene film bags. Mathematical model to predict air temperature leaving heat exchanger was developed. The results obtained in the present study are summarized as follows. 1. Heat exchange rate in the counter-flow type air-water heat exchanger with polyethylene film bags was compared to that of polyethylene film. Heat exchange rate was almost identical at air velocity of 0.5m/s on polyethylene film surface. But, heat exchange rate of heat exchanger with polyethylene film bag was $32{\sim}55KJ/m^2$ hr higher than that of polyethylene film at air velocity of 1.0m/s. 2. Considering the formation of uniform water film and the sufficient heat exchange rate of polyethylene film bags, optimum water flow rate in polyethylene film bags was $3.0{\sim}6.0{\ell}/m^2$ min. 3. The overall heat transfer coefficient of polyethylene film bags was found to be $35.0{\sim}130.0KJ/m^2\;hr\;^{\circ}C$ corresponding to the air velocity ranging 0.5 to 4.0 m/s on polyethylene film surface. And the overall heat transfer coefficient showed almost linearly increasing tendency to the variation of air velocity. 4. Mathematical model to predict air temperature leaving the heat exchanger was developed, resulting in a good agreement between the experimental and predicted values. But, the experimental results were a little lower than predicted. 5. Effectiveness of heat exchanger for the experiment was found to be 0.40~0.81 corresponding to the number of transfer units due to the variation of air velocity ranging 0.6 to 1.7 m/s.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.554-557
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• 2011

금속분말을 연료로 하는 연소기 개발에 있어 발생하는 문제점 중에 하나는 알루미나 slag 처리이다. 연소기 내부에 Water film을 형성시킴으로써 금속분말 연소기의 문제점을 해결할 수 있을 것으로 기대한다. 이를 위한 선행연구로 water film의 형성 조건에 대한 실험을 수행하였다. 실험 모델에 대하여 물 분사 속도가 증가할수록 원형 모델에 대한 water fim 각도가 작아져, 약 10 m/s이상에서 완전한 water film이 형성되는 것을 알 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1191-1196
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• 2006

Analysis of drying characteristics has been carried out with one-dimensional model in the dryer using the principle of the refraction of radiation. The dryer is composed of hot water tank, a plastic film conveyer belt, drying material, etc. The model considers the conduction and radiation within the plastic film and drying material. The film is semitransparent to radiation and the drying material is assumed to be semitransparent or opaque to radiation. The results shows that the effect of radiative transfer on the drying rate is relatively large when the thickness of drying material is small and the water temperature is high. When the material is thin, the drying rate by only conduction is also enhanced so that drying time can considerably be reduced.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권2호
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• pp.69-79
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• 2000

Falling film rectification involves simultaneous heat and mass transfer between vapor and solution film. In the present work, the adiabatic rectification process of ammonia-water vapor by the falling solution film on the vertical plate was investigated. The continuity momentum, energy and diffusion equations for the solution film and the vapor mixture were formulated in integral forms and solved numerically, The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer coefficient in each phases were investigated. The stripping of water in vapor mixture occurred near the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer coefficient in falling film.

• 설비공학논문집
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• 제6권4호
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• pp.453-462
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• 1994

An unsteady quasi one-dimensional model of momentum, heat and mass transfer in a falling film of a vertical plate absorber which is cooled by air was developed using the integral method. Energy conservation of the absorber wall is considered in the model. The model can predict absorption rate, film thickness and mean velocity as well as concentration and temperature profiles. Predictions of steady state temperature and concentration profiles for LiBr/water system for constant wall temperature condition are in good agreement with the two-dimensional finite difference method solutions. Effects of operating conditions, such as convective heat transfer coefficient between the cooling air and the absorber wall, cooling air temperature and film thickness at inlet, on absorption rate of water vapor into LiBr/water solution were shown.

• 설비공학논문집
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• 제11권3호
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• pp.414-421
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• 1999

Falling film rectification involves simultaneous heat and mass transfer between vapor and liquid interface. In the present work, the adiabatic rectification process of ammonia-water vapor on the vertical plate was investigated. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. The model could predict the film thickness, the pressure gradient, and the mass transfer rate. The effects of Reynolds number and ammonia concentration of solution and vapor mixture, rectifier length, and the enhancement of mass transfer in each phases were investigated. The stripping of water in vapor mixture occurred new the entrance of ammonia solution, which imposed the proper size of an adiabatic rectifier. Rectifier efficiency increased as film Reynolds number increased and as vapor mixture Reynolds number decreased. The improvement of rectifier efficiency was significant with the enhancement of mass transfer in falling film.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.317-317
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• 2011

Water dissociation on oxide surface has been researched in many fields because of its importance as fundamental phenomenas. MgO(001) is a good model system to understand heterogeneous catalysis, gas sensors, ground-water contaminants, and atmosphere chemistry. Over decades, ultrathin film of MgO on Ag(100) have attracted research activities thanks to its enhanced catalytic property. Correlation of the oxide and the metal, potential screening, charge fluctuation from interface reconstruction makes different energetics of hydroxylation of waters on film. We calculate the water-spliting energetics under the vacuum system.