• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.181-187
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• 2000

This study is object to structural analysis comparison of continuous casting mold. A two-dimensional finite element model was developed to compute the temperature distribution, thermal stress and thermal strain behavior for continuous casting mold. For structural analysis using thermal analysis result from ANSYS. In other to structural analysis of continuous casting mold, many variables such as casting speed, cooling condition, film coefficient, convection and load condition are considered.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2999-3007
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• 1994

The unsteady numerical simulations have been presented for the laminar natural convection in a partially open compartment. Computations were performed within the domain of the compartment in order to show the thermal radiation and the partially opening effects on the flow fields and heat transfer characteristics. The results were shown for different Planck numbers(0.05~5) and opening ratios(0.25~0.75) being fixed with Ra=$10^5$ and Pr=0.71. Considering the flow which is buoyancy driven from the heated wall, and the buoyancy is not much affected by the further outside region from the opening, the numerical computations have been performed without an outer region by the particular boundary treatments on the flow velocity and temperature at the different partial openings. The confined numerical domain reduced the CPU time and the memory of computer. P-1 approximation of radiative transfer equation was employed with Marshak type boundary conditions along with the pseudo-black body approximation at the partial openings. The numerical results clearly show that the natural convective flow and heat transfer are much affected by increase of thermal radiation particularly from the initial state. When thermal radiation is not much affecting the flow ($PL{\le}1$), it was found that thermal radiation effects are almost negligible.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.792-793
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• 2008

This paper deals with the temperature calculation using equivalent thermal network for surface mounted permanent magnet synchronous motor(SPMSM) under the steady-state condition. In the equivalent thermal network, heat sources are generated from copper loss and iron loss. Heat transfer consists of conduction, convection and radiation. However, radiation is neglected in this paper because its effect is much smaller than others. Although the heat transfer coefficient in conduction use material property, heat transfer coefficient in convection is difficult to measure due to the atmosphere and ambient condition. Temperatures of each region in SPMSM are measured by thermocouple in operating condition and the thermal resistances of convection are calculated by kirchhoff's current law(KCL) and experimental result. In order to verify the validation and reliability of the proposed equivalent thermal network, temperature which is calculated other load condition is compared with experimental results. Accordingly, temperatures of each region in other SPMSMs will be easily predicted by the proposed equivalent thermal network.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.211-216
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• 2001

Flow motion and variation of thermal field around a bubble which attached at the upper cooled solid wall in a $B\dot{e}nard$ convection flow is studied experimentally using thermo-sensitive liquid-crystal tracers and image processing for flow visualization and analysis. The air is injected gradually by $0.1m\ell$ to make the bubble. As the growing of the bubble in a $B\dot{e}nard$ convection flow, the variation of temperature field and surface tension along the bubble, which in turn cause to change the thermal field patterns and the flow direction and patterns. 6 cells flow pattern is transformed into diverse flow pattern. At the large size of a bubble, it's only conduction mechanism under the region of the bubble because of low Ra number 1137, but the convection flow both sides of the bubble leads to another convection flow in the bubble influence area which has been remained stable stagnation.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.428-437
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• 2019

Analytical thermal models based on average convection heat transfer are frequently used for the design and selection of forced air-cooled plate fin heat sinks. In this paper, a convection heat transfer model within a ±10% margin of error was presented through experimental investigation. Five types of heat sinks with inlet widths of 1.7-6.8 mm were tested at 50-160 W heat sources to derive and verify the model. Causes of error between the experiment and analytical thermal model were analyzed and listed to design the heat sink. Using proposed method and the lists to be considered in the paper, a quick and accurate heat sink design of the power-conversion system is expected.

• 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.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1053-1057
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• 2004

This paper presents the adjoint variable design sensitivity analysis for thermal systems considering both conduction and convection heat transfer. Both nodal temperature and total heat flow are considered to be objective functions and design sensitivity formulas are derived for each case. For the case of convection heat transfer, the adjoint analysis is carefully proceeded to obtain a precise result. A topology optimization example is examined for a simple planar square plate in order to design a heat exchanger as verification.

• Journal of Ocean Engineering and Technology
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• v.13 no.1 s.31
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• pp.121-129
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• 1999

Double-diffusive convection with verical temperature and concentration gradients in thermally stratified fluids has been investigated experimentally using an electrochemical technique. Cupric sulfuric-sulffuric acid solution confined between two horizontal copper electrodes was used. The change of thermal and solutal buoyance has no influence on the range of voltage for the limiting current. Due to Soret effect, the onset time of natural convection is delayed as the stabilizing thermal buoyancy decreases. Also it is found that the shrinkage of the unstabilizing solutal buoyancy makes the onset of natural convection retard. Multi-layered convective phenomena do not appear because cupric sulfate-sulfuric acid solution is thermally stratified, and heat diffuses faster than cupric sulfate solfate solution.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1080-1085
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• 2004

The physical model considered here is a horizontal layer of fluid heated below and cold above with heat-generating conducting body placed at the center of the layer. The dimensionless thermal conductivities of body considered in the present study are 0.01, 1 and 150. The dimensionless temperature difference ratios considered are 0.25, 2.5 and 25. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for variety of Rayleigh number from $10^{3}$ to $10^{6}$. Multi-domain technique is used to handle square-shaped heat-generating conducting body. The results for the case of conducting body with heat generation are also compared to those without heat generation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2069-2078
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• 1993

The buoyancy-driven turbulent thermal convection is predicted using an anisotropic hybrid turbulence model, which is incorporated with a low Reynolds k-.epsilon. turbulence model and an anisotropic buoyant part of algebraic stress model(ASM). The numerical predictions are compared with the Davidson's model,(1) the full ASM and the experimental results of Cheesewright et al.(2) All the models are shown to predict good agreements with the experiments for the averaged turbulence quantities. It is found that the effect of an anisotropic part on the Reynolds stress and the turbulent heat fluxes is substantial. In this study, the present hybrid model gives a fairly reasonable prediction in terms of the computational accuracy, convergence and stability. The contribution of an anisotropic buoyant part to turbulent heat fluxes are also scrutinized over the range of Rayleigh numbers $(4.79{\times}10^{10}{\le}Ra{\le}7.46{\times}10^{10}).$