• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2378-2383
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• 2007

Direct Numerical Simulation was carried out to predict mass transfer in turbulent flow around a rotating stepped cylinder. This investigation is a follow-up study of Nesic et al. [Corrosion, Vol. 56, No. 10, pp. 1005 - 1014] The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. Two cases were considered; Sc=1 and 10 both at Re=335. Here, Sc and Re stand for Schmidt number and Reynolds number, respectively, based on the step height and the surface speed of the cylinder upstream the step. Main focus was placed on the correlation between turbulent fluctuation and concentration field. The spatio-temporal evolution of concentration field is discussed. The numerical results are qualitatively compared with those of the experiment conducted with the same flow configuration.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.8 no.2
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• pp.60-72
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• 2002

포장된 복합비타민의 보관수명을 예측하기 위한 수학모델을 수치해석의 방법 중 finite difference method을 이용한 컴퓨터 프로그램을 개발하였다. 이 컴퓨터 프로그램에는 포장재료의 수분확산계수와 용해도를 비롯한 식품의 수분확산계수 등 다양한 인자들을 포함하고 있다. 포장재료를 통과하는 수분의 물질전달은 G.A.B water sorption isotherm을 기본으로 했다. 본 연구에서는 비정상상태에서의 물질전달로 기본 수학모델링을 구하였다. 본 수학모델과 프로그램의 결과는 실험치와 비교하지 않았고 대신 특정한 경우를 가상하여 이에 존재하는 analytical solutions를 실제로 구하여 본 수학모델과 컴퓨터 프로그램의 신뢰도 측정을 하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.79-88
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• 1997

An analysis of unsteady heat and mass transfer in the Modified Chemical Vapor Deposition has been carried out including the effects of chemical reaction and variable properties. It was found that commonly used quasi-steady state assumption could be used to predict overall efficiency of deposition, however, the assumption would not provide detailed deposition profile. The present unsteady calculations of wall temperature profile and deposition profile have been compared with the existing experimental data and were in good agreement. The effects of variable torch speed were studied. Linearly varying torch speed case until time=120s resulted in much shorter tapered entry than the constant torch speed case.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.3
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• pp.294-302
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• 1998

The charateristics of the convective mass transfer in horizontal rectangular enclosure with horizontal concentration gradients are analyzed. The effect of Grashof number(Gr) and aspect ratio(L/H) is investigated numerically using the control-volume method. Numerical results are obtained for Grashof numbers between $10^4$ and $10^6$ aspect ratios from 1 to 100 and results are compared with existing andlytical results. It is found that there exists a well defined aspect ratio for which the mean Sherwood number is maximum and the core flow changes from parallel to non-parallel at $Gr^2{Sc^2}(A^{-3}}{\geq}{10^5}$ and in the Ralongrightarrow0 regime the numerical results agreed very well with correlation derived from analytical results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1201-1212
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• 1999

A numerical analysis is performed to predict the thermal response and ablation rate for charring or non-charring material which is designed to be used as thermal protection system (TPS). The numerical program composed of in-depth energy balance equation and the aerotherm chemical equilibrium (ACE) program. The ACE program calculates various thermochemical state from ablation products. The developed numerical program is verified by comparing the reported results from literature. The sensitivity tests for input parameters are performed. The thermal behavior of ablating material is mainly affected by density of ablating material, convective heat transfer coefficient and recovery enthalpy of flow field.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.431-439
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• 1999

A generator-GAX combined rectification system of an ammonia absorption heat pump was investigated to get the optimum design values. The mass and heat transfer phenomena of the rectification system were analysed. The number of column plates, equilibrium temperature of solution on each plate and flow rates of solution and vapor generated were predicted. The characteristics of mass and heat transfer of the generator-GAX combined rectification system, i.e. concentration difference of leaving solution and vapor on each column plate, were found to be mainly governed by the pressure of generator, reflex ratio and temperature difference of analyser coolant. The number of rectification column plates for each different pressure in generator was obtained. The optimum locations for installing the feeder from solution-cooled absorber and GAX desorber in generator were predicted. The improvement of COP was followed by the increase of the rectifier efficiency and the number of column plate, and the decrease of reflex ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.870-877
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• 2008

Numerical analysis is applied to model Pt-catalyzed reaction in a micro-scale combustor fueled by butane. The reaction constants of catalytic oxidation are determined from plug flow model with the experimental data. Orders of magnitude between the chemical reaction rate and the mass transfer rate are carefully compared to reveal which mechanism plays a dominant role in the total fuel conversion rate. For various conditions of fuel flow rate and surface temperature, the profiles of Sherwood number are investigated to study the characteristics of the mass transport phenomena in the micro-tube combustor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1756-1765
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• 2001

The heat and mass transfer process between the falling liquid desiccant(TEG) film and the air in counter flow at the dehumidifier of desiccant cooling system were investigated. The governing equations with appropriate boundary and interfacial conditions describing the physical problems were solved by numerical analysis. As a result, the effects of the design parameters and the outside air conditions on the rates of dehumidification and sensible cooling were discussed. The results of the dehumidification and sensible cooling rates were compared with those of the cross flow at the same conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.366-374
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• 2014

Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.4
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• pp.80-86
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• 2012

This study is for figuring out a possibility of realization of the thermal protection system(TPS) for temporary use under high temperature condition and improving a design of the future TPS. On this purpose, environmental condition of the system has been simplified: the boundary conditions consist of a internally heating surface and a externally heated surface which is simulating the external high temperature condition. Configuration of the system is simplified as a hexahedon. Melting characteristics of the phase change material(PCM) and air temperature variation of TPS with or without connector have been numerically analyzed and compared. As a result of numerical analysis, the heat from the internally heated surface could not be effectively transferred. Therefore, temperature of inner space has been increased.