• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1552-1557
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• 2004

This paper introduced about characteristics on the non-steady heat transfer of STS 304 hollow cylinder, In the non-steady state, the specific heat and conductivity are depended on the temperature variations, and these properties affect to the governing equation on heat conduction. But the most of numerical analysis on heat conduction is assumed to constant properties which is conductivity and specific heat. Assuming that conduction is assumed to constant properties which is conductivity and specific heat. Assuming that the properties are reacted sensitively, the numerical results can have the difference of between constant properties with non-constant properties. The main parameters are specific heat and conductivity. The temperature distributions of the STS 304 hollow cylinder became in steady state after 4 minutes in case of the constant properties. As the conductivity in varied with temperature, the temperature distributions became in steady state after 15 minutes. Therefore, a numerical analysis of the non steady state heat transfer will has to apply that conductivity varied with temperature.

• 동력기계공학회지
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• 제8권2호
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• pp.39-44
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• 2004

The effects of the STS 304 hollow cylinder property variations on the non-steady heat conduction are considered in this paper. In the non steady state, the specific heat and conductivity are depended on the temperature variations, and these properties affect to the governing equation on heat conduction. But the most of numerical analysis on heat conduction is assumed to constant properties which is conductivity and specific heat. Assuming that the properties are reacted sensitively, the numerical results can have the difference of between constant properties with non constant properties. The main parameters are specific heat and conductivity. The temperature distributions of the STS 304 hollow cylinder became in steady state after 4 minutes in case of the constant properties. As the conductivity is varied with temperature, the temperature distributions became in steady state after 15 minutes. Therefore, a numerical analysis of the non steady state heat transfer is so important in case of varying temperature.

• 한국정밀공학회지
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• 제10권2호
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• pp.30-39
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• 1993

The study is concerned with the thermo-viscoplastic finite element analysis of nonisothermal hot container extrusion through conical dies. The problem is treated as a non-steady state incorporating the nonisothermal heat transfer analysis. The analysis of temperature distribution includes heat transfer though the boundary surface including conduction, convection and radiation. The analysis of heat transfer is decoupled with the analysis of deformation and the material interaction is considered through iteration procedure. The effect of important process parameters including die angle and extrusion ratio in the process is investigated. Due to the geometric feature for the container extrusion through conical dies, automatic remeshing is mandatory. Automatic remeshing is achieved by introducing the modular remeshing technique.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.172-175
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• 2003

Run-Out-Table is the region between EDT and CT. Hot killed strip is cooled by air and water in ROT. In this procedure, phase transformation and shape deformation occur due to temperature drop. Because of un-ideal cooling condition, deformation of strip and non-uniform phase distribution come into existence. This phenomenon affects the strip property and lead th the existence of residual stress. And it exerts effects on the Coiling process, Coil Cooling process, and Un-coiling process. Through these process, the residual stresses of strip are more larger and unbalance of these stresses become more severe. Finite element (FE) based models for the analysises of non-steady state heat transfer and elastoplastic deformation are described in this investigation. The analysises of thermodynamics and phase transformation kinetics are suggested also. Using the ROT simulation result coiling process and coil cooling process simulations are carried out.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.831-838
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• 2004

A fluid-solid conjugate solver has been newly developed and applied to an actual engine disk system. Most of the currently available conjugate solvers lack the special thermal modeling for turbomachinery disk system applications. In the present new code, these special models are implemented to expand the applicability of the conjugate method and to reduce the required computational resources. Most of the conjugate analysis work so far are limited to the axisymmetric framework. However, the actual disk system includes several non-axisymmetric components which inevitably affect the local heat transfer phenomena. Also the previous work devoted to this area usually concentrate their efforts on the steady-state thermal field, although the one in the transient condition is more critical to the engine components. This paper presents full 3D conjugate analysis of a single stage high pressure turbine rotor-stator disk system to assess the three-dimensional effects (Fig. 1). The analysis is carried out not only in the steady-state but also in the engine accelerating transient condition. The predicted temperatures shows good agreement with measured data.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권3호
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• pp.245-256
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• 2014

This work is focused on the boundary layer and heat transfer characteristics of hydromagnetic flow over a stretching sheet with variable thickness. Steady, two dimensional, nonlinear, laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness and power law velocity in the presence of variable magnetic field and variable temperature is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-Swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and the effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.

• 소성∙가공
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• 제12권4호
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• pp.302-307
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• 2003

Hot rolled strip is cooled by air and water in Run-Out-Table. In this process, phase transformation and shape deformation occurs due to temperature drop. Because of un-ideal cooling condition of ROT, irregular shape deformation and phase transformation arise in the strip. which affect the strip property and lead to the residual stress of strip. And these exert effects on the following processes, coiling process, coil cooling process, and re-coiling process. Through these processes, the residual stress becomes higher and severe. For the prediction of residual stress distribution and shape deformation of final product, Finite element(FE) based model was used. It consists of non-steady state heat transfer analysis, elasto-plastic analysis. thermodynamic analysis and phase transformation kinetics. Successive FEM simulation were applied from ROT process to coil cooling process. In each process simulation, previous process simulation results were used for the next process simulation. The simulation results were matched well with the experimental results.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1860-1873
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• 2022

Nuclear thermal-hydraulic system analysis codes have been developed to comprehensively model nuclear reactor systems to evaluate the safety of a nuclear reactor system. For analyzing complex systems with finite computational resources, system codes usually solve simplified fluid equations for coarsely discretized control volumes with one-dimensional assumptions and replace source terms in the governing equations with constitutive relations. Wall boiling heat transfer models are regarded as essential models in nuclear safety evaluation among many constitutive relations. The wall boiling heat transfer models of two widely used nuclear system codes, RELAP5 and TRACE, are analyzed in this study. It is first described how wall heat transfer models are composed in the two codes. By utilizing the same method described in Part 1 paper, heat fluxes from the two codes are compared under the same thermal-hydraulic conditions. The significant factors for the differences are identified as well as at which conditions the non-negligible difference occurs. Steady-state simulations with both codes are also conducted to confirm how the difference in wall heat transfer models impacts the simulation results.

• 한국초전도ㆍ저온공학회논문지
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• 제22권3호
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• pp.25-30
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• 2020

The diminishing of heat leak into cryogenic vessels can prolong the storage time of cryogenic liquid. With the storage of cryogenic liquid reducing, the heat leak decreases, while the actual storage time increases. Regarding to the theoretical analysis, the obtained results seems to be constructive for the cryogenic insulation system applications. This study presents a predictive assessment of heat leak occurring in non-vacuum tanks with a single layer of insulation. A Radial steady-state heat transfer, based on heat conduction equation, is taken into consideration. Graphical results show the thermal performance of the insulation used, they also allow us to choose the appropriate insulation thickness according to the shape and diameter of the storage tank.

• 태양에너지
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• 제19권1호
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• pp.67-75
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• 1999

The effect of radiation heat transfer was investigated under various operating conditions in a circular tube with circumferential fins and circular disks. Using a finite volume technique(FVM) for steady laminar flow, the governing equations were derived in order to simulate the flow and temperature fields. In addition, the P-1 approximation and the Weighted Sum of Gray Gas Model(WSGGM) were used for the radiation transport equation(RTE). From the results, radiation heat transfer was significant compared to convection heat transfer. These results will be applied to the design of the heat exchanger for a condensing bolier, which were developed for domestic heating.