• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2034-2041
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• 2003

This study introduced a lattice Boltzmann computational scheme capable of modeling thermo hydrodynamic flows with simpler equilibrium particle distribution function compared with other models. The equilibrium particle distribution function is the local Maxwelian equilibrium function in this model, with all the constants uniquely determined. The characteristics of the proposed model is verified by calculation of the sound speeds, and the shock tube problem. In the lattice Boltzmann method, a thermal fluid or compressible fluid model simulates the reflection of a weak shock wave colliding with a sharp wedge having various angles $\theta$$\sub$w/. Theoretical results using LBM are satisfactory compared with the experimental result or the TVD.

• Advances in aircraft and spacecraft science
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• v.2 no.2
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• pp.109-124
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• 2015

This paper deals with the aerodynamic and aerothermodynamic trade-off analysis of a hypersonic flying test bed. Such vehicle will have to be launched with an expendable launcher and shall re-enter the Earth atmosphere allowing to perform several experiments on critical re-entry phenomena. The demonstrator under study is a re-entry space glider characterized by a relatively simple vehicle architecture able to validate hypersonic aerothermodynamic design database and passenger experiments, including thermal shield and hot structures. A summary review of the aerodynamic characteristics of two flying test bed concepts, compliant with a phase-A design level, has been provided hereinafter. Several design results, based both on engineering approach and computational fluid dynamics, are reported and discussed in the paper.

• Journal of the Korean Solar Energy Society
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• v.37 no.6
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• pp.93-102
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• 2017

Interpretation of relevance between long-wave radiation and meteorological elements is recognized as an essential element for understanding the underlying mechanism of urban thermal environment formation. In this study, we analyzed relation between three elements : long-wave radiation, temperature, and lower-middle class cloudiness. The correlation was analyzed through field observations. The results are as follows. (1) Temperatures and long-wave radiation increased from January to March. This phenomenon has been confirmed in urban and suburban areas. (2) Long-wave radiations showed a tendency to increase clearly with increasing cloudiness.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.398-407
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• 2002

An experimental and analytical study was made on the heat transfer characteristics of one small (150 W), two medium (60 and 1,500 W, respectively) and two large (7,500and 100,000 W) two-phase loop thermosyphons (TLT), and the results from the experiments were used to see if a computer simulation code alone for such TLT heat transfer systems would give any meaningful quantitative results without being accompanied with some benchmark experimental verification. Two simulation methods were used for the analysis of the systems, i.e., the lumped and the sectorial thermal resistance methods. The study clearly shows that the computer simulation for the three TLTs can predict the most cases of the affecting parameters involved, provided that correct empirical correlations are used. To do so, however, the interior temperature distribution had to be verified by experiment.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1326-1331
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• 2009

Drying process in the cylindrical thin film layer of sludge with the thickness less than a few millimeters has been investigated. Thin film drying is specially designed and used to dry the viscous materials like sewage sludge. The thin film layer of sludge is dried on the metallic cylindrical surface through which thermal energy is supplied to the layer during drying. The wall temperature is assumed to be constant during drying in the present study for the simplification. In order to solve the equations, the mass transfer rate on the drying surface should be determined. The mass flux of evaporated water vapor on the surface is estimated with the formulation given in the literature. The effect of some physical parameters on drying has been examined to figure out the drying characteristics of the sludge layer.

• Transactions of Materials Processing
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• v.21 no.6
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• pp.378-383
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• 2012

Laser forming is an advanced process in sheet metal forming in which a laser heat source is used to shape the metal sheet. This is a new manufacturing technique that forms the metal sheet only by a thermal stress. Analyses of the temperature and stress fields are very important to identify the deformation mechanism in laser forming. In this paper, temperature distributions and deformation behaviors of DP980 steel sheets are investigated numerically and experimentally. FE simulations are first conducted to evaluate the response of a square sheet in bending. The effects of process parameters such as laser power and scanning speed are then analyzed numerically and experimentally. It is observed that experimental and numerical results are in good agreement. These results provide a relationship between the line energy and the angles for laser bending of DP980 steel sheets.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.661-662
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• 2008

In this paper a novel bearingless switched reluctance motor (BLSRM) with hybrid stator poles is proposed. The operating principle of the proposed motor is presented. Further one prototype motor is designed and manufactured. Compared with existing BLSRM, it has many advantages such as lower number of switches and cost, simpler control algorithm, lower thermal load. Meanwhile through finite element method (FEM) characteristics of the proposed structure such as inductance, torque and radial force can be obtained. According to the FEM results, the above advantages of the proposed structure can be verified.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.2
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• pp.107-112
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• 2014

To cope with the ever increasing electric power demands in metropolitan areas, a greater underground cable transmission capacity is required. In general, it must be determined whether the temperature in the tunnel maintains the maximum allowable temperature. In order to improve this point, it is used to the loss factor. But, for economic cooling, it is problem to use such loss factor in this country. In this study, based on the load factor in this country, technique for calculating the loss factor has been presents. The suggested method has been tested in a sample section using the computer and the results have shown the usefullness of the suggested method.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1130-1131
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• 2015

팰릿 형태의 XLPE (Cross-Linking Polyethylene)를 Hot Press로 시험편을 제작하여 열분석 데이터 처리장치를 이용하여 시차 주사 열량법 (differential scanning calorimetry, DSC)과 열 중량 분석 (Thermo gravimetric analysis, TGA) 등으로 열적 특성을 분석하였다. 분석 결과, XLPE의 전이온도 피크는 $61^{\circ}C$, 용융온도에 해당하는 피크는 $102^{\circ}C$에서 나타났으며 XLPE의 TG 분석 결과 $470^{\circ}C$ 근처에서 한 번의 급격한 열중량 감소를 보였으며 $800^{\circ}C$까지 측정 후 잔류물은 완전 분해되어 거의 존재하지 않았음을 알 수 있었다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.10a
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• pp.60-63
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• 1995

The behavior of the work materials in the chip-tool interface in extremely high strain rates and temperatures is more that of viscous liquids than that of normal solid metals. In these circumstances the principles of fluid mechanics can be invoked to describe the metal flow in the neighborhood of the cutting edge. In the present paper an Eulerian finite element model is presented that simulates metal flow in the vicinity of the cutting edge when machining a low carbon steel with carbide cutting tool. The work material is assumed to obey visco-plastic (Bingham solid) constitutive law and Von Mises criterion. Heat generation is included in the model, assuming adiabatic conditions within each element. the mechanical and thermal properties of the work material are accepted to vary with the temperature. The model is based on the virtual work-stream function formulation, emphasis is given on analyzing the formation of the stagnant metal zone ahead of the cutting edge. The model predicts flow field characteristics such as material velocity effective stress and strain-rate distributions as well as built-up layer configuration