• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.5
• /
• pp.148-156
• /
• 2001

Computational Fluid Dynamics (CFD) analysis was carried out to investigate exhaust gas flow and acoustic characteristics in the exhaust system of a passenger car. Transient 3-dimensional flow field in the front and rear mufflers was simulated by CFD and far-field sound pressure was modeled by a simple monopole source method. Engine performance simulation was also performed to obtain the boundary condition of instantaneous fluid flow variation at the inlet of the exhaust system. Detailed exhaust gas flow characteristics such as velocity and pressure distribution inside the mufflers were presented and the pulsating pressure amplitude was compared at several positions in the exhaust system to deduce sound pressure level. The present method of the acoustic analysis coupled with CFD techniques would be very effective for the prediction of sound noise from vehicle exhaust systems although the effects of the inlet boundary condition and heat transfer on the accuracy of the prediction have to be validated through further studies.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.5
• /
• pp.62-74
• /
• 2001

In this study, the prediction of performances and emissions of the gasoline engine of a light passenger car has been accomplished. The method of characteristics including friction, heat transfer, area change and entropy gradients was used to analyze the flow in the intake and exhaust systems. For in-cylinder calculation, the single-zone model was adopted for the periods of the intake, exhaust, compression and the expansion of the burnt gas and the 2-zone expansion model was applied to the period of combustion process. The simulation program was verified by comparison with the experimental values both for the naturally aspirated engine and the turbocharged engine showing good agreements. Using the simulation program, multi-valve system and turbocharging were examined as a means of increasing engine Performances.

• Journal of the Korean Solar Energy Society
• /
• v.24 no.1
• /
• pp.21-27
• /
• 2004

Near Infrared Ray (NIR) are primarily of interest to the high energy physicist. It is the intermediate portion of the spectrum, which extends from approximately 0.8 to 1.5 ${\mu}m$ and include a portion of the all of infrared, that is thermal radiation and is pertinent to heat transfer. It is important to study that temperature distribution of the drying materials by surface encompasses a range of NIR wave lengths. This study is to investigate the characteristics of NIR dryer by experimental results. it was made a comparison with various textiles, velocity ratio and distance of lamp and textiles. In case of spongy type textile the drying performance is the superior of all. The 0.15m distance drying effect of improvement 30% more than 0.26m distance between lamp and textiles. As the contained water increases, the drying speed for textile can be increased.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.49-53
• /
• 2005

This paper presents a multi-scale hybrid simulation for the design of a catalytic multi-tubular reactor with high performance. The multi-tubular reactor consists of shell and a large number of tubes in which various catalytic chemical reactions occur. To consider fluid dynamics in the shell-side and kinetics in the tube-side at the same time, commercial CFD package and process simulation tool are coupled. This hybrid approach allowed us to predict many kinds of meaningful results such as tube center temperature profile, heat transfer coefficients on the tube wall, temperature rise of cooling medium, pressure drop through shell and tube side, concentration profile of each chemical species along the tube, and so on., and to achieve the optimal reactor design.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.3
• /
• pp.110-118
• /
• 1995

The filling phase analysis of the injection molding process for thermoplastics was applied to predict pressure, themperature and shear stress in the test mold, and the results were compared with the experiment using 30% glass fiber added ABS resin. The finite difference method was used in the analysis considering the effects of heat transfer between molten polymer and mold wall, and also frictional heating by shear flow. The analysis results were considered as a method to improve the quality and the productivity of injection molding process. Using the analysis results, the molding factors such as mold-ability of polymers, performance of injection molding machine, positioning of gate and dimendsioning of runner in the injection molding process can be estimated at the design stage of mold for good quality and productivity.

• Vacuum Magazine
• /
• v.3 no.1
• /
• pp.16-21
• /
• 2016

FinFETs are able to be scaled down to 22 nm and beyond while suppressing effectively short channel effect, and have superior performance compared to 2-dimensional (2-D) MOSFETs. Bulk FinFETs are built on bulk Si wafers which have less defect density and lower cost than SOI(Silicon-On-Insulator) wafers. In contrast to SOI FinFETs, bulk FinFETs have no floating body effect and better heat transfer rate to the substrate while keeping nearly the same scalability. The bulk FinFET has been developed at 14 nm technology node, and applied in mass production of AP and CPU since 2015. In the development of the bulk FinFETs at 10 nm and beyond, self-heating effects (SHE) is becoming important. Accurate control of device geometry and threshold voltage between devices is also important. The random telegraph noise (RTN) would be problematic in scaled FinFET which has narrow fin width and small fin height.

• Journal of Energy Engineering
• /
• v.6 no.2
• /
• pp.152-161
• /
• 1997

Blending various coals during the coke making process affects the quality of coke as well as the total energy required for the process. The mathematical model based on Merrick's work developed to predict the effect of blending coals on coke making process. The Crank-Nicholson method was used to solve the model equation to predict temperature distributions, a coking time, and a total energy required during the process. The developed model successfully applied to Kwang-Yang Steel Company's coke oven to validate the model performance. It is hoped that the model can serve as a guidelines on how to blend coals during the process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.4
• /
• pp.252-261
• /
• 2001

Room air flow and temperature distribution was numerically investigated where a PAC(personal air conditioning) system was installed. The calculated results were compared with those from experiments. The effects of the important operation parameters such as the air flow rate, velocity, and temperature at the diffuser on the thermal performance of the system were studied. The possibility of energy saving using the PAC system was verified from the results, It was shown that the warm air from the diffuser could not spread over the whole task area if the inlet temperature was too high.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.6
• /
• pp.674-682
• /
• 1998

In this study, thin film evaporation of water on low-fin tubes were experimentally investigated. Five low-fin tubes with different fin spacing and fin height were tested. Test range covered 0.146kg/ms $\leq$$\Gamma$$\leq$0.219kg/ms and 10㎾/$\m^2$$\leq$q $\leq$70㎾/$\m^2$. Saturation temperature was loot. Compared with the plain tube, low fin tubes enhanced the water film evaporation from 60% to 100%. Tubes with fin spacing smaller than 2mm and fin height higher than 1mm performed better than tubes with other fin configuration. However, when fin spacing was too small at high film flow or fin height was too high at low film flow, the performance decreased. The heat transfer coefficient slightly increased as the flow rate increased. Correlations are developed based on present data.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.10a
• /
• pp.207-208
• /
• 2003

Increasing interest in indoor air quality (IAQ) control has been found because of its serious effect on human health. To evaluate IAQ, thermal comfort in terms of temperature and velocity distributions of indoor air has to be analyzed in detail. Choice of location for installation of air-conditioner in a building will affect the performance of cooling effect and thermal comfort on the occupants, which in turn will affect the indoor air quality (IAQ) of the building. In this paper, we present a discussion on the proper location of the air-conditioner in order to obtain good thermal comfort for occupant of a typical bedroom in Macao. A set of carefully designed numerical experiments is run with the Computational Fluid Dynamics (CFD) software FLOVENT 3.2 [1]. Reynolds averaged Navier-Stokes equations are solved with finite volume technique and turbulence effects upon the mean flow characteristics is modeled with the k - & model. Assumption of steady state environment is made and only convective and conductive heat transfer from the occupant and air-conditioner are being concerned.