• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.528-533
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• 1988

The assignment of boundary conditions for the piston thermal loading analysis in internal combustion engine has been tested using the thermal circuit method with an engine simulation program. In an attempt to examine the accuracy of the employed boundary condition, another thermal boundary condition has been sought for through the electrolytic tank analogue method. Comparison of calculated temperature distributions obtained from these two boundary conditions with measured temperature values reveals that the electrolytic tank analogue method gives excellent agreement. However, the thermal circuit method has been found to be reasonable for practical applications, if modified partially.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.6
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• pp.31-36
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• 2005

Use of the high frequency motor spindles are increasing for the high speed machine tools recently. The important problem in the high speed spindles is to reduce and minimize the thermal effect by the motor and ball hearings. Thermal characteristics according to the bearing preload and spindle cooling are studied for the spindle with the oil mist lubrication and high frequency motor. Temperature distribution and thermal displacement according to the spindle speed, preload and flow rate are measured. Temperature distribution and thermal displacement of the high speed spindle system can be estimated reasonably by using the three dimensional model through the finite element method. The results of analysis are compared with the measured data. This study supports thermal optimization and find out more effective cooling condition. This paper show that the suitable preload and spindle cooling are very effective to minimize the thermal effect by the motor and ball bearings.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.30-33
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• 1994

This paper studies on the effect of DSC(Differential Scanning Calorimeter) analysis condition on the glass transition temperature of silica filled epoxy network polymer used for ultra-high voltage apparatus. The effects of temperature scanning rate specimen size and gas flow rate on measured glass transition temperature have been studied in order to select optimum thermal analysis condition.

• Fire Protection Technology
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• s.10
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• pp.9-12
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• 1991

As the present idustry is devolping rapidly, automatic sprinklers continue to play a key role in modern fire protection. But the technical basis and methods of measurement of the thermal response of sprinklers are not studying in our country. Therefore, the purpose of this paper is to analyze the thermal response characteristics and condition parameters of automatic sprinkler head.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.84-89
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• 2000

Friction welding of titanium and aluminium is numerically modeled by the axisymmetric thermal elastic-plastic analysis. In titanium/aluminium friction welding, heat transfers into the titanium substrate to a distance of z=10(mm) on the side of the bondline and into the whole region of the aluminium substrate having the large thermal conductivity. Adjacent to the bondline, $^{\sigma}r\;and\;^{\sigma\theta}$ are tensile in the substrate whose thermal shrinkage is large, and are compressive in the substrate whose thermal shrinkage is small. $\sigma_z$ along the radial direction is large tensile at the periphery of the component. Plastic strain occurs only close to the bondline in the aluminium substrate. In the components of plastic strain, $\varepsilon^p_r\;and\;\varepsilon^p_{\theta}$ have positive values and $\varepsilon^p_r$ has large negative value. However, $\varepsilon^p_r$ is produced not because of the severity of the mechanical restraint condition, but on purpose to satisfy the condition of the volume constant. A plastic work is proposed as a measure to evaluate the mechanical severity. The plastic work is larger in the aluminium substrate than that in the titanium substrate. The mechanical condition is severer in the aluminium substrate.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.119-126
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• 2022

A growing number of gas-insulated transformers in underground power substations in urban areas are approaching 20 years of operation, the time when failures begin to occur. It is thus essential to prevent failure through accurate condition diagnosis of the given facility. Various solid insulation materials exist inside of the transformers, and the generated decomposition gas may differ for each gas-insulated equipment. In this study, a simulation system was designed to analyze the deterioration characteristics of SF₆ decomposition gas and insulation materials under the conditions of partial discharge and thermal fault for diagnosis of gas-insulated transformers. Degradation characteristics of the insulation materials was determined using an automatic viscometer and FT-IR. The analysis results showed that the pattern of decomposition gas generation under partial discharge and thermal fault was different. In particular, acetaldehyde was detected under a thermal fault in all types of insulation, but not under partial discharge or an arc condition. In addition, in the case of insulation materials, deterioration of the insulation itself rapidly progressed as the experimental temperature increased. It was confirmed that it was possible to diagnose the internal discharge or thermal fault occurrence of the transformer through the ratio and type of decomposition gas generated in the gas-insulated transformer.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1247-1252
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• 2004

The present paper is devoted to the modeling method based on an averaging approach for thermal analysis of microchannel heat sinks subjected to the uniform wall temperature condition. Solutions for velocity and temperature distributions are presented using the averaging approach. When the aspect ratio of the microchannel is higher than 1, these solutions accurately evaluate thermal resistances of heat sinks. Asymptotic solutions for velocity and temperature distributions at the high-aspect-ratio limit are alsopresented by using the scale analysis. Asymptotic solutions are simple, but shown to predict thermal resistances accurately when the aspect ratio is higher than 10. The effects of the aspect ratio and the porosity on the friction factor and the Nusselt number are presented. Characteristics of the thermal resistance of microchannel heat sinks are also discussed.

• Fire Science and Engineering
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• v.9 no.1
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• pp.20-29
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• 1995

The sprinkler head is a component of the sprinkler system intended to discharge water for automatic detection and extinguishment of fires. On this study, thermal characteristic values affecting the sensitivity of the fusible alloy type sprinkler head were obtained and analyzed under heated air stream condition which had constant temperature and velocity. The experiment was carried out under the forced convection condition with both the conductive heat loss considered and neglected. The thermal characteristic values of the sprinkler head were obtained in accordance with the material and shape of the heat responsive element and the conditions of the main body.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.136-139
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• 2004

The domestic concrete standard specification(l999) reports roughly about heat transfer analysis and thermal stress analysis for mass concrete. Engineers cannot but choice after all numerical method such FEM, FDM to escape review. It seems to us that the specification is room for reconsideration because above methods are vary expensive and without popularity. This study suggests thermal distributed function in mass concrete. The function consists of two independent variables, curing time and depth. It's results have been tested a sensitivity for unit cement content, form condition, curing condition, and shape(depth, width). Results of the function are made a comparison with analytical values of MIDAS/CIVIL and a few measurement values. The researchers could meet with coherent and good results for variable cases.

• Journal of ILASS-Korea
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• v.15 no.2
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• pp.94-99
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• 2010

The object of this investigation is to study the thermal properties and spray characteristics of kerosene fuel in high temperature and pressure conditions. In order to investigate the thermal properties and spray characteristics, KIVA3 and SUPERTRAPP have been used at the same time. The thermal properties of kerosene has been calculated in high temperature and pressure condition using SUPERTRAPP. The study of spray characteristics has been conducted at both original properties of KIVA3 and calculated properties. The evaporation rate was increased in proportion to pressure when the calculated properties were used. However, the effect of pressure was not shown in the case of using original properties. So the calculated properties are more effective than original properties in high temperature and high pressure condition.