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A Numerical Study of the Flow Characteristics and Separation Efficiency of a Hydrocyclone
임익태,곽규동,김세민,박영기 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11
In this study, mixture flow of sand and water within a hydrocyclone was investigated using the Eulerian-Eulerian model based on a Computational Fluid Dynamics (CFD) technique. Experiments were also performed to validate the numerical analyses results. In Eulerian-Eulerian analyses, both solid and liquid phases are regarded as continua. Accordingly, conservation equations, such as continuity and momentum equations, are applied to each phase of sand and water. In this study, the RNG k-ε model was used as a turbulence model. The results of the computational analysis were compared with those obtained experimentally. The CFD and experimental results were largely consistent with each other. The accuracy of the analysis model was compared with the experiment, and the effects of inlet volume fraction of solid and inlet velocity of the mixture on separation efficiency were examined. Separation efficiency decreased as inlet velocity increased. In addition, separation efficiency was high when solid concentration was low (3%), but there was no relationship between concentration and separation efficiency when the solid concentration was above 6%.
임익태,김우승,Im, lk-Tae,Kim, Woo-Seung 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.8
An algorithm for modeling the filling of metal into a mold and solidification has been developed. This algorithm uses the implicit VOF method for a filling and a general implicit source-based method for solidification. The model for simultaneous filling and solidification is applied to the two-dimensional filling and solidification of a square cavity. The effects of the wall temperature and gate position on the solidification are examined. The mixed natural convection flow and residual flow resulting from the completion of a filling are included in this study to investigate the coupled effects of the filling and natural convection on solidification. Two different filling configurations (assisting flow and opposite flow due to the gate position) are analysed to study the effects of residual flow on solidification. The results clearly show the necessity to carry out a coupled filling and solidification analysis including the effect of natural convection.
임익태,김우승,Im, Ik-Tae,Kim, U-Seung 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.1
The mold filling process has been a central issue in the development of numerical methods to solve the casting processes. A mold filling which is inherently transient free surface fluid flow, is important because the quality of casting highly depends on such phenomenon, Most of the existing numerical schemes to solve mold filling process have severe limitations in time step restrictions or Courant criteria since explicit time integration is used. Therefore, a large computation time is required to analyze casting processes. In this study, the well known SOLA-VOF method has been modified implicitly to simulate the mold filling process. Solutions to example filling problems show that the proposed method is more efficient in computation time than the original SOLA -VOF method.
MOCVD에 의한 InGaAs, InGaP 및 InGaAsP필름의 성장 및 조성변화에 대한 수치해석 연구
임익태,김동석,김우승,Im, Ik-Tae,Kim, Dong-Suk,Kim, Woo-Seung 한국반도체디스플레이기술학회 2005 반도체디스플레이기술학회지 Vol.4 No.1
Metaloganic chemical vapor deposition, also known as metalorganic vapor phase epitaxy has become one of the main techniques for growing thin, high purity films for compound semiconductors such as GaAs, InP, and InGaAsP. In this study, the distribution of growth rate and composition of InGaAsP, InGaP, and InGaAs films are studied using computational method. The influences of process parameters such as pressure, temperature and precursors' partial pressure on the growth rate and composition distributions are analyzed. The film growth rate is increased in the upstream part according to the increase of temperature but not in the downstream part. The Ga composition in InGaAsP film shows an asymptotic behavior for temperature variation but As composition varies significantly within the temperature range considered in the present study. The overall film growth rates of InGaP, InGaAs and InGaAsP are decreased with increasing the Ga/In ratios of the source gases. Pressure variation does not seem to be a significant parameter to the film growth. Film growth characteristics of tertiary films such as InGaP and InGaAs show similar trends to the quaternary film, InGaAsP.
임익태,박찬우,김광선 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.12
Vertical sputtering systems are key equipment in the manufacture of liquid crystal display (LCD) panels. During the sputtering process for LCD panels, a glass plate is transported between chambers for various processes, such as deposition of chemicals on the surface. The minimization of surface scratches and damage to the glass, the rate of consumption of gas, and the stability of the floating glass-plate are key considerations in the design of a gas pad. To develop new, non-contact systems of transportation for large, thin glass plates, various shapes of the nozzle of a gas pad unit were considered in this study. In the proposed nozzle design, negative pressure was used to suppress undesirable fluctuations of the glass plate. After the nozzle’s shape was varied through numerical simulations in two dimensions, we determined the optimal shape, after which three-dimensional analyses were carried out to verify the results from the two-dimensional analyses. The rate of heat transfer from the glass plate, as a result of the gas jet, was also investigated. The average Nusselt number at the glass surface varied from 22.7 to 26.6 depending on the turbulence model, while the value from the correlation for the jet array was 23.5. It was found that the well-established correlation equation of the Nusselt number for the circular jet array can be applied to the cooling of the glass plates.
Micro machining of an STS 304 bar by magnetic abrasive finishing
임익태,문상돈,오성모 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.7
A magnetic abrasive finishing process is a method of non-traditional precision machining in which the finishing process is completed using magnetic force and magnetic abrasives. In this research, a STS 304 cylindrical workpiece was finished using a magnetic abrasive finishing process at 30,000 rpm, and the roughness, roundness, and changes in the micro-diameter were investigated. The study showed that it is possible to control the micro-diameter and weight of the STS 304 cylindrical workpiece by using a near linear approach. Surface roughness as fine as 0.06 ㎛ (Ry) and roundness as fine as 0.12 ㎛ (LZS) were achievable by using a diamond paste with 1 ㎛ particles. Vibrational motion applied to the workpiece improved the surface roughness. The improvement of the surface roughness was achieved because the vibrational motion effectively removes unevenness in the rotational direction and the direction orthogonal to it.
A Study on the Dielctric Properties of the PTC BaTiO3 Ceramic Thin Films
임익태,소병문 한국반도체디스플레이기술학회 2012 반도체디스플레이기술학회지 Vol.11 No.3
The films were deposited at evaporator system and were annealed at heat treatment. The films had a dense microstructure with fine grains. The electrical properties of the films were dramatically controlled with annealing. Samples Preparation were analyzed in term of positive temperature coefficient of Resistivity Samples were made in the substrate tempera-true of 400oC deposition time of 10 hours, and forward power of 210watt. R-T(resistivity-temperature) Characteristics of the samples were investigated as a function of the substrate type and the ambient temperature. The resistivity of the thin film specimens was compared with that of the bulk type specimens. By using RF/DC magnetron sputtering system, we obtained lower resistivity in the thermistor with thin BaTiO3 film than that in the bulk type thermistor.