• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
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• pp.113-116
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• 1998

A numerical study was performed on the fluid flow in the melt of the cold model for Czochralski growth system. The fluid flow in the melt of Woods metal with crucible diameter of 20cm was calculated using a three dimensional finite difference method. Since the crucible size is large, fully turbulent model as well as laminar model was used in the calculation. The effects of crucible rotation rate, crystal rotation rate and wall temperature difference on the velocity and temperature distribution were also investigated. For the purpose of verifying the results of calculation, a cold model experiment using Woods metal was also conducted and the velocity distribution in the melt of the model was measured.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.183-189
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• 2004

The flow and the heat transfer about the cross-flow fin-tube heat exchanger in an out-door unit of a heat pump system has been numerically Investigated. Using the general purpose analysis code, FLUENT, the Navier-Stokes equations and the energy equation are solved for the three dimensional computation domain that encompasses multiple rows of the fin-tube. The temperature on the fin and tube surface is assumed constant but compensated later through the fin efficiency when predicting the heat-transfer rate. The contact resistance is also taken into consideration. The flow and temperature fields for a wide range of inlet velocity and fin-tube arrangements are examined and the results are presented in the paper. The details of the flow are very well captured and the heat transfer rate for a range of inlet velocity is in excellent agreement with the measured data. The flow solution provides the effective permeability and the inertial resistance factor of the heat exchanger if the exchanger were to be approximated by the porous medium. This information is essential in carrying out the global flow field calculation which, in turn, provides the inlet velocity lot the microscopic temperature-field calculation of the heat exchanger unit.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.232-238
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• 2009

The objective of this study is to investigate the suitable design for a domestic CWP pump, which is used in cooling-water intakes for the unit 3 and 4 of Yeonggwang nuclear power plant. All the simulations are performed, using CFD method with a commercial code STAR-CCM+ version 3.02. After modeling a present design of the pump, the flow around the rotating blade was calculated by using quasi-static method and sliding mesh method with the almost same condition as an actual state. Based on fundamental simulations with various depth of sea water, the reference pressure for the boundary condition of the present study was decided. To verify the reliability of the calculation results, the suction flow rate of the data was compared with that of the experimental data. As a result of this comparison, it is confirmed that two results are fairly consistent. For the improvement of the suction flow rate, computational analysis was done by changing a flow channel and blade shapes. It is shown that the suction flow rate of the new pump was improved.

• 한국전산유체공학회지
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• 제14권3호
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• pp.69-75
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• 2009

The objective of this study is to investigate the suitable design for a domestic Circulating water pump(CWP), which is used in cooling-water intakes for the unit 3 and 4 of Yeonggwang nuclear power plant. All the simulations are performed, using CFD method with a commercial code STAR-CCM+ version 3.02. After modeling a present design of the pump, the flow around the rotating blade was calculated by using quasi-static method and sliding mesh method with the almost same condition as an actual state. Based on fundamental simulations with various depth of sea water, the reference pressure for the boundary condition of the present study was decided. To verify the reliability of the calculation results, the suction flow rate of the data was compared with that of the experimental data. As a result of this comparison, it is confirmed that two results are fairly consistent. For the improvement of the suction flow rate, computational analysis was done by changing a flow channel and blade shapes. It is shown that the suction flow rate of the new pump was improved.

• 한국자동차공학회논문집
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• 제7권6호
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• pp.1-7
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• 1999

In this study, the prediction method of coolant flow rates has been developed and applied to an engine and vehicle cooling system. The flow rate passing through each component of the system is very important parameter to evaluate the heat transfer process form the combustion gas to the coolant and the heat rejection process form the radiator /heater to the ambient air. However, the present study reveals that the measurement using the flowmeter fails to give practical flow rates due to its additive resistance. In contrast, the present method which uses the parallel and serial relationship of flow resistance proved to be a good tool to predict the real flow rates. It can be also used to design the cooling system in the incipient stage of engine/vehicle development . The procedure was coded to the computer program so as to use it flexibly and, in the future, to expand it into an independent design tool of the whole cooling system including the heat release and rejection.

• 한국표면공학회지
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• 제23권3호
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• pp.160-166
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• 1990

The effects of the variation of proedd varibles on the flow patterns and effects of the flow patterns on the deposition rate and uniformity in the Si-epitaxy CVD with SiH4 as the source of Si were studied through the calculation by use of control volume method. The reslts showed that the natural convection was undesirable to the uniformity of deposition rate, whose effects were decreased with the dercrese with the decrese of the pressure in the reactoor and with the increase of the flow rate. However. the excessive increase of flow rate caused the movement of the unreacted gas to the substrate. Therefore it resulted in the non-uniform depositions. The rotation of substrate was apperared to improve the uniformity. The resulte of this study could used in CVD process to design the reator and to find the optimum conditions of the process variables.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1407-1412
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• 2004

Impedance calculations of electric railway traction systems is essential to define characteristics and to design it. The self impedance is defined voltage drop rate per unit length, the mutual impedance is represented as a voltage induced to transmission line from transmission line. The self and the mutual impedance are influenced by ground return currents. The earth is considered as a semi-infinitely extended non-ideal conductor. The current of transmission line produces earth current induced magnetically and it flow through a path having minimum impedance. Carson proposed the impedance calculation formula using wave equations and magnetic field equations. Though the formula have an improper equation, that is still used as a standard impedance calculation method. This paper introduced an impedance calculation method that the complex depth of earth return method assumes that the current in conductor returns through an imagined earth depth path located directly under original conductor at a depth of. In this paper, we showed that this proposed method has a closed form and is easier than Carson's.

• 한국분무공학회지
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• 제27권4호
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• pp.181-187
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• 2022

For carbon neutrality, direct-injection hydrogen engines are attracting attention as a future power source. It is essential to estimate the transient injection rate of hydrogen for the optimization of hydrogen injection in direct injection engines. However, conventional injection rate measurement techniques for liquid fuels based on the injection-induced fuel pressure change in a test section are difficult to be applied to gaseous fuels due to the compressibility of the gas and the sealing issue of the components. In this study, a momentum flux measurement technique is introduced to obtain the transient injection rate of gaseous fuels using a force sensor. The injection rate calculation models associated with the momentum flux measurement technique are presented first. Then, the volumetric injection rates are estimated based on the momentum flux data and the calculation models and compared with those measured by a volumetric flow rate meter. The results showed that the momentum flux measurement can detect the injection start and end timings and the transient and steady regimes of the fuel injection. However, the estimated volumetric injection rates showed a large difference from the measured injection rates. An alternative method is suggested that corrects the estimated injection rate results based on the measured mean volumetric flow rates.

• 한국통신학회논문지
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• 제33권12B호
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• pp.1097-1102
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• 2008

An effective method for calculating delay bounds of flows through flow aggregations and deaggregations is given. Based on this calculation, it is suggested a simple criteria for flow aggregation whether the aggregation will induce an increased delay bound. The criteria is evaluated in a few realistic scenarios.

• 한국산학기술학회논문지
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• 제10권10호
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• pp.2589-2595
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• 2009

본 연구에서는 장하분배법(Load Distribution Method) 및 등가회로법(Equivalent Circuit Method)을 이용하여 액체금속이송을 위한 전자기펌프를 설계하고 제작하였다. 제작된 전자기펌프의 구동전력과 이에 상응하는 액체의 유량관계를 구하였다. 액체금속유동에 가하는 전자기 힘(Lorentz force)의 크기에 따른 유속과 유량을 수치해석기법을 이용하여 계산하였다. 수치해석결과를 상용코드인 FLUENT를 이용하여 계산한 결과와 비교하고 분석하였다. 다양한 전자기력의 크기에 대한 액체금속(우드메탈)의 평균속도에 대한 결과는 FLUENT의 결과와 5%이내의 오차 내에서 잘 일치하였다.