• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.561-564
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• 2006

Because of new requirements related to the employment of SMT(Surface Mounting Technology) manufacturing and the diversity of components on high density PCB(printed circuit boards), Thermal control of the reflow process is required in oder to achieve acceptable yields and reliability of SMT assemblies. Accurate control of the temperature distribution during the reflow process is one of the major requirements, especially in lead-free assembly. This study has been performed for reflow process using the commercial CFD tool(Fluent) for predicting flow and temperature distributions. There was flow recirculation region that had a weak point in the temperature uniformity. Porous plate was installed to prevent and minimize flow recirculation region for acquiring uniform temperature in oven. This paper provided design concept from CFD results of the steady state temperature distribution and flow field inside a reflow oven.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.585-590
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• 2003

The distributions of mass flow rate and pressure are major factors to deside the performance of a proton exchange membrane fuel cell (PEMFC). These factors are affected by channel configuration of air plate. In this paper. structural analysis is performed to investigate deformation of porous media. Two kind of models are suggest for flow analyses. Deformed porous media and undeformed porous media are considered for air plate model. The Numerical flow analysis results with deformed porous media and undeformed porous media had some discrepancy in pressure distribution. The pressure and velocity in a working condition are numerically calculated to predict the performance of the air plates. Distributions of the parameters in the PEMFC are analyzed numerically under steady-state conditions.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.200-204
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• 1986

Particle size distribution in a Continuous Mixed Suspension Mixed Crystal Removal (CMSMPR) crystallizer has been analyzed using the Population Balance (PB) model. This method presents difficulties when the growth rate of crystal depends on the crystal size. Recent studies indicate that in many cases the growth rate is dependent on size when the crystal sizes are small. In this study, a Residence Time Distribution(RTD) model was proposed to take the size dependence into account together with an appropriate numerical scheme. When compared with the approximate results based on PB model, RTD model results showed improvements also a nucleation effect which is normally unimportant for steady state analysis. Start-up data for NaCl-Water-Ethanol system was compared with computed values.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1619-1625
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• 2007

This paper deals with the heat transfer characteristics due to a fire of train standing at under-ground station. In order to analyze the fluid characteristics at under-ground station, the governing equation was assumed to be steady-state, incompressible and turbulent fluid model. The commercial Fluent ver. 6.0 was used to solve the above numerical problem. Through the numerical analysis, fluid path-line, temperature distribution and $CO_2$ density distribution are demonstrated for three kinds of cases. As a conclusion of the study, a scenario for operation of ventilation fan in a fire is proposed.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.159-168
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• 1997

본 연구는 Moss형 LNG선박의 방열구조에서 LNG탱크에 침입하는 열량과 선체의 온도분포를 예측하고, 운항 중 LNG탱크를 Cooling down(예냉)하는 경우 발생하는 비정상상태에서 LNG탱크에 발생하는 국부적인 열응력을 검토할 수 있는 비정상 온도분포해석과 LNG증발량을 검토하였다. 특히 운항 중인 선박을 대상으로 일반적인 수치계산시에 필요한 각종 입력절차를 간소화 하고 경계조건 선정시에 비 전문가도 쉽게 이용할 수 있는 전산프로그램을 개발하였다. Moss형 LNG탱크의 예냉작업에 필요한 최적의 냉매량과 예냉조건을 비정상상태에서 해석한 것은 설계자 및 선박 운항자에게 유용하게 이용될 것이다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.19-23
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• 2014

This paper describes the electron transport characteristics in $SF_6$-He gas calculated E/N values 0.1~700[Td] by the Monte Carlo simulation and Boltzmann equation method using a set of electron collision cross sections determined by the authors and the values of electron swarm parameters obtained by TOF method. This study gained the values of the electron swarm parameters such as the electron drift velocity, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients for $SF_6$-He gas at a range of E/N. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.237-238
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• 2015

This paper analyzed the impact of Voltage Sourced Converter High Voltage Direct Current(VSC HVDC) connected an offshore wind power on the Jeju Island electrical power system. Wind power output fluctuates with the changing of wind speed. By changing wind power output occupancy into 100%, 60%, 10% respectively, we can understand the bus voltage distribution controlled by VSC HVDC. PSS/E is used to analyze steady-state simulation results which show effectiveness of the VSC HVDC for Jeju Island power system.

• Journal of Mechanical Science and Technology
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• v.19 no.10
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• pp.1950-1956
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• 2005

An analysis has been carried out to investigate the effect of the reflectivity on the temperature distribution of a glass panel by infrared radiant heating. Halogen lamps are used to heat the panel, located near the top and bottom of the rectangular chamber. The thermal energy is transferred from the lamps to the panel only by radiation and it is considered by using view factor. The conductive transfer is limited inside the panel. The results show that the uniformity of the temperature distribution of the panel is improved and, at the same time, the time for heating increases as the wall reflectivity increases. The temperature difference between the center and the corner reaches a maximum in the early stage of the heating process and then decreases until it reaches a uniform steady-state value.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.800-808
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• 1998

In this study the thermal stress distribution and deformantion characteristics resulting from the nonuniform temperature fields of the cylinder block of a light 3-cylinder 4-stroke gasoline engine were analyzed using the 3-dimensional finite element method. The temperature distributions req-uisite for the thermoelastic behavior alalysis were obtained from the steady-state heat conduction analysis performed on the basis of experimental data. in order to examine the effect of a ceramic material the cylinder liner was replaced by the silicon nitride($Si_{3}N_{4}$) and its thermal behaviors were compared with those of the original block.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.272-275
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• 1997

Noninvasive multifrequency microwave radiometry using coaxial waveguide antenna has been investigated for a homogeneous and our layer human body model. We derived finite-difference time-domain(FDTD) algorithm and equation of MUR and generalized perfectly matched layer(GPML) absorbing boundary conditions(ABCs) in cylindrical coordination. The coupling between coaxial waveguide antenna and a biological object was analyzed by use of the FDTD method using MUR and GPML ABCs to obtain the absorbed power patterns in the media. The specific absorption rates(SAR) distribution which was corresponding to the temperature distribution was calculated in each region by use of the steady-state response in FDTD method. The SAR patterns of FDTD method using MUR ABCs was compared with those of FDTD method using GPML ABCs.