• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.1
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• pp.1-9
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• 1992

Radiation heat transfer was calculated for initial stage of crystal growth in Czochralski crystal growth system. View factors among surface elements were calculated for the estimation of heat evolution and all the surfaces were assumed to be diffuse-gray. The values of view factors were greatly different along the position of surface elements. The dissipated amounts of heat flux from the melt surface were 3.6 times larger than those from the crystal surface at the initial stage of crystal growth and this amounts were greater when the surface elements were not considered. The trijunction part of the crystal was greatly affected by the melt surface near the crystal. Consequently radiation heat transfer between surface elements must be considered in order to correctly simulate the initial crystal growth.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1381-1389
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• 1988

The heat transfer by simultaneous conduction, convection and radiation between flame and fuel surface in a thermally radiating medium is investigated theoretically. The flame and fuel surface are assumed to be diffuse, gray, infinite, isothermal, parallel surfaces separated by a finite distance. The space between the plates is supposed is formulated exactly in terms of simultaneous interior-differential equations. The numerical results reveal the effect of the system parameters on the heat transfer characteristics and the temperature distributions. The numerical results reveal that the optically thick radiating medium has a blocking effect on the total beat transfer. The temperature distributions are observed to be convex upward for an optically thick radiating medium as the alberto decreases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.331-344
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• 1987

A numerical analysis has been conducted on the interaction of the thermal radiation and natural convection in a rectangular enclosure filled with a gray fluid. P-1 approximation is adopted for the radiative transfer and its application limit is examined. Considered are the Stark number effect, the optical thickness effect and the wall emissivity effect on the flow and heat transfer characteristics. As the Stark number increase or the optical thickness decreases, the boundary layer thickness and the flow velocity increase. Transition to turbulence is retarded with the increase of the radiation effect. When the optical thickness is one, the radiation effect is negligible for the Stark numbers larger than 10.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.256-260
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• 2014

This study was carried on the phenomena in reactivity with the clay surface according to the thickness of the cobalt component coating. In the coated specimen, it was observed that the cobalt component was spreaded to diffuse with a constant thickness from the surface of it and the diffusion layer at the white porcelain soil was more increased with the increase of the amount of cobalt sulfate than at the celadon porcelain one. It was evaluated that the color of the surface on the coated specimen at the white porcelain soil was changed from grayish blue to blue and the $L^*$ value was decreased from 51.78 to 37.61 and also in the case of the coated specimen in celadon porcelain soil, $L^*$ value was from 53.91 to 38.93 and the color was from dark olive gray to dark gray. The physical properties of the specimen were characterized by X-ray diffraction, Scanning electron microscope, Dilatometer, TG-DTA, UV-vis spectrophotometer and HRDPM.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.5
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• pp.543-552
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• 2003

The effects of a directionally emitting and reflecting dielectric surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The emissivity and reflectivity of opaque and gray wall vary with direction. Combined effect of conductive and radiative heat transfer is analyzed using finite difference and the direct discrete-ordinates method. The parameters under study are conduction to radiation parameter, optical depth, refractive index ratio. The results with directional and diffuse properties deviate each other when the conduction to radiation parameter is less than around 0.01. The wall heat flux differs fur optical thickness less than around 0.1. However, the medium temperature profiles differ for optical thickness greater than around 1. Deviations from diffuse property calculations are larger for hot wall with directional property than cold wall with directional property. As n increases from 1.5, the trend changes are observed fur refractive index ratio about n=6.10

• Korean Journal of Veterinary Research
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• v.24 no.2
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• pp.195-199
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• 1984

The present observations were focussed mainly on the macroscopic and histopathological observation to polyps encountered on the stomach of 4-month-old pig, small intestine of 3-month-old pig and cecum of 9-month-old dog. The results were summarized as follows; 1. The polyps were gray or pink hemispherical shapes attached by the broad base to the gastrointestinal walls and were 3 to 8 mm in diameter and diffuse appearance. The surfaces of polyps were flat or indented and were ulcerated in some large polyps. 2. In histopathological findings, the polyps were nodules composed of lymphoid follicles, which were characterized by the differentiation and proliferation of the lymphoid cells in the lamina propria or submucosa of the gastrointestinal tract. The lymphoid nodules have the thin septa and thick capsules of the connective tissues, also comprised more numerous and larger sinus-like-blood vessels and more diffuse lymphoid cells in the peripheral zones than those in the central zones of nodules. In addition, the external surface of the polyps bulged toward the intestinal lumen were covered with the abnormal epithelium, or the degenerative and necrotic lymphocyte aggregates. 3. These polyps were considered as lymphoid polyps caused by the hyperplasia of the lymhoid follicles.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.2
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• pp.197-203
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• 2014

In this paper, the effect of unsteady radiation on the horizontal fin of an external fuel tank by flame of a flying flare was analysed to see the temperature increase of the fin and the thermal impact on the fin. Radiation between two surfaces was calculated using the concept of radiation resistance of surface and space including radiation, irradiation and shape factor for two flying trajectories of a flare, maximum temperature of 2200 K, emissivity of 0.95, flying velocity of 30 m/s, and thermal surface area of $0.01m^2$. The result shows that the temperature increase of the fin is 0.236 K, and the thermal effect on the fin is ignorable. And it was found that temperature is increased a little because small amount of heat energy can be radiated due to the short exposure time to the heat source.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1451-1458
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• 2001

The effects of a specularly reflecting surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The walls are opaque, and black or gray. The walls emit diffusely but reflect diffusely or speculary. Heat is transferred by the combined effect of conduction and radiation. The radiative heat transfer is analyzed using direct discrete-ordinates method. The parameters under study are conduction, to radiation parameter, optical depth, wall emissivity, and reflection characteristics. The specular reflection and diffuse reflection show sizeable differences when the conduction to radiation parameter is less than around 0.01. The differences appear only either on the side wall heat flux or on the medium temperature profiles for the range of this study. The differences on the side wall heat flux are observed for optical thickness less than around 0.1 However the differences on the medium temperate profiles are found for optical thickness greater than around 1. The difference increase with increasing reflectance. The specular reflection increases the well heat flux gradient along the side wall.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1621-1628
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• 1990

Numerical solutions are presented for the heat transfer from radiating and convecting fins. Consideration is given to thin, annular fins attached to a tube surface for which the temperature is constant. Fin to fin, fin to base, and fin to environment radiative interactions are considered. It is assumed that the radiating surface is diffuse-gray, the environment is black, and the surrounding fluid is transparent. The radiation terms are formulated by using Poljak's net-radiation methoad. The mathematical description of the simultaneously heat transport by conduction, convection, and radiation leads to a nonlinear integro-differential equation. This has been solved for a wide range of the pertinent physical parameters by using finite difference method and iteration method based on the Newton-Raphson technique. The temperature distributions, heat transfer rates, fin efficiencies, and fin effectivenesses are presented in dimensionless form. The results definitely indicate that the use of fins leads to a significant increase in heat transfer compared with the unfinned tube.