• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3125-3134
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• 2010

Three-way catalyst durability in the Korea requires 5 years/80,000km in 1988 but require 10 years/120,000km after 2002. Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but don't satisfy thermal durability. Three-way catalyst maintains high temperature in interior domain but maintain low temperature on outside surface. This study evaluated thermal durability of three-way catalyst by thermal flow and structure analysis and the procedure is as followings. Thermal flow parameters ranges were determined by vehicle test and basic thermal flow analysis. Response surface for rear catalyst temperature was constructed using the design of experiment (DOE) for thermal flow parameters. Thermal flow parameters for rear catalyst temperature in vehicles examination were predicted by desirability function. Temperature distribution of three-way catalyst was estimated by thermal flow analysis for predicted thermal flow parameters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.81-85
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• 2007

A safety valve is used for protecting the pressure vessel and facilities by discharging the operating fluid into the valve from the accident when the pressure is over the designated value. The fluid is sulfurous acid and nitric acid. etc. in the semi-conductor assembly line. Thus the valve elements material must be acid resistance. Teflon, which is used generally as inner parts of a valve, tends to easily sticks to sliding surface by thermal expansion under high temperature. Some studies are performed to change teflon to another material and shape to have a better fluidity under the condition. The analysis of the thermal expansion is conducted by commercial FEM software to improve the problems. Boundary conditions were temperature and load in this study. From the analysis, the thermal expansion of stainless steel is verified to be lower than that of teflon under high temperature. Thus coupled teflon/stainless steel-made valve is applied to assembly line without danger due to thermal expansion.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.16-23
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• 2005

The objective of this research is to estimate two dimensional ablating and charring of heat shield materials in severe aero-thermal heat transfer. This estimation requires an accurate and rapid technique for its serious heat transfer with a moving boundary. Aerodynamic heating is obtained by an explicit relation which is a function of Mach number and air condition, while a fully implicit method is used for heat transfer calculations. Moving boundary is captured by FLIAR method which is a subgroup of VOF. Thickness of ablating and charring of heat shield, temperature of the moving surface and rate of radiation heat are calculated and compared with references. The results are in good agreement with other calculations.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.282-289
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• 2000

Direct numerical solution for flow and heat transfer for Benard convection with a body is obtained using an accurate and efficient Fourier-Chebyshev collocation and multi-domain method. The flow and temperature fields are obtained fur different Rayleigh numbers and thermal boundary conditions of body. The body has adiabatic and constant temperature conditions. The existence of a body gives different flow and heat transfer fields in the system, compared to pure Benard convection. The flow and temperature fields are also affected by the thermal boundary condition of a body.

• Nuclear Engineering and Technology
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• v.30 no.6
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• pp.609-616
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• 1998

Cast duplex stainless steels are extensively used for primary pressure boundary components. These components are, however, embrittled due to the precipitation of $\alpha$' phase by spinodal decomposition and other processes when exposed to reactor operating temperature for a design lifetime or life extension conditions. This report presents a procedure for estimating the current condition and the residual life of safety-related stainless steel components by using ANL database and correlations. The database of Charpy impact energy suggests that CF-8M grade is the most susceptible to thermal aging and CF-3 grade is the least. Thus, the integrity of CF-8M alleys may be degraded seriously and the degree of deterioration may exceed acceptance limit after several years of service in the nuclear reactors.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.60-66
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• 2015

Molten zone shape of pulse laser welding is affected by welding conditions such as beam power, beam speed, irradiation time, pulse frequency, etc. and is divided into conduction type and keyhole type. It is necessary to design heat source model for irradiation of laser beam in the pulse laser welding. Shape variables and the maximum energy density value of the heat source model are different depending on the molten zone shape. In this paper, pulse laser welding simulation for joining of cylindrical part and circular cover was carried out. The heat source model for pulse laser beam with circular path was applied to the heat input boundary condition, radiative and conductive heat transfer were considered for the thermal boundary condition. For each phase, thermal and mechanical properties according to temperature were also applied to analysis. Analytical results were in good agreement with the molten zone size of specimen under the same welding conditions. So, the reliability of the welding simulation was verified. Finally, the improvements for reducing residual deformation after cover welding could be reviewed analytically.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.11
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• pp.613-620
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• 2009

The thermal stresses of a ceramic heat exchanger were analyzed numerically since the ceramic material is good in heat resistance but weak in the thermal stress. The analysis of thermal stress was conducted in the ceramic core with two boundary conditions depending on bolt jointing. The thermal stresses were computed by applying temperature and pressure distributions obtained from the numerical results of conjugate heat transfer to ANSYS WORKRBENCH. When number of bolt joining halls was reduced from $8\times2$ to $4\times2$, the maximum principal stresses decrease by 47.6~50.5% and increase in safety factors by 2.18~2.5 for ultimate tensile strength. Thus, it can be said that bolt joining halls should be minimized in ceramic heat exchanger to be efficient in reducing thermal stress. In addition, the width of particular gas flow passages were revised from 52 mm to 42 mm to reduce maximum thermal stresses since certain passages experienced high thermal stresses. From the revision, safety factors were increased by 13.8~14.1% for the boundary condition of $4\times2$ bolt joining halls. Therefore, it is suggested that thermal stress can be reduced by changing local geometry of a ceramic heat exchanger.

• Tribology and Lubricants
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• v.34 no.6
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• pp.247-253
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• 2018

Temperature rise due to viscous shear of the lubricating oil generates hydrodynamic pressure, even if the lubricating surfaces are parallel. This effect, known as the thermal wedge effect, varies significantly with film-temperature boundary conditions. The bearing conducts a part of the heat generated; hence, the oil temperature varies with the thermal conductivity of the bearing. In this study, we analyze the effect of thermal conductivity on the thermohydrodynamic (THD) lubrication of parallel slider bearings. We numerically analyze the continuity equation, Navier-Stokes equation, energy equation including the temperature-viscosity and temperature-density relations for lubricants, and the heat conduction equation for bearing by creating a 2D model of the micro-bearing using the commercial computational fluid dynamics (CFD) code FLUENT. We then compare the variation in temperature, viscosity, and pressure distributions with the thermal conductivity. The results demonstrate that the thermal conductivity has a significant influence on THD lubrication characteristics of parallel slider bearings. The lower the thermal conductivity, the greater the pressure generation due to the thermal wedge effect resulting in a higher load-carrying capacity and smaller frictional force. The present results can function as the basic data for optimum bearing design; however, the applicability requires further studies on various operating conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.3
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• pp.157-166
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• 2009

The pulverized coal combustion behavior in the coal fired utility boiler has been investigated with the CFD and process analysis techniques. The used commercial software were CFX and PROATES, and these were coupled each other to get more reliable boundary condition set-up, resulting in more reliable solution. For two cases which were the actual operation condition of A power plant, the calculated values from the coupled CFD and process analysis for thermal energy system were compared with the plant data, and the good agreements were obtained for Case 1 and 2. The calculated temperature distributions on the surface of heat exchangers were compared with the plant data for the steam temperatures across heat exchangers, and these explained the actual operating situation very well. The temperature deviation across the final superheater tube, which was believed to be the main cause of the frequent tube failure, were also explained very well with the calculated distributions of gas temperature and radiation on the plane of the final superheater.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.635-640
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• 1996

A thermo-elastic system in the production machine has highly nonlinear dynamic characteristics. In general, the finite element method is utilized for accurate analysis. However, it requires large computing time. Thus, thermo-elastic systems are usuallymodeled as electric and fluid system using lumped para,eter. In this paper. we propose the bondgraph model and transient simulation methodology of thermo-elastic system in consideration of various boundary and joint contact conditions. Consequently, the proposed method ensures a possibility of its on-line compensation about undesirable phenomena by using real time estimate process and electronic cooling device for thermal appropriate behavior. Thermo-elastic model consisting of bush and shaft including contact condition is presented.