• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.62-70
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• 2004

Interaction between fluid flow and thermal radiation has received considerable attention due to its numerous applications in engineering field. In this case the thermofluid properties of radiating fluid vary with the variation of temperature field caused by absorption and emission of radiant heat. To analyze the radiation heat transfer in radiating fluid, the simultaneous solution of the radiative transfer equation (RTE) and the fluid dynamics equations is required. This means that the numerical procedure used for the RTE must be computationally efficient to permit its inclusion in the other submodels, and must be compatible with the other transport equations. The finite volume method (FVM) and the discrete ordinates method (DOM) are usually employed to simulate radiation problems in generalized coordinates. These two representative methods are examined and compared, especially in view of the numerical integration of the radiation intensity over solid angle. The FVM shows better accuracy than the DOM owing to less constraints of the selection of control angle.

• 설비공학논문집
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• 제7권2호
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• pp.266-275
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• 1995

A numerical investigation on the conduction-natural convection-surface radiation conjugate heat transfer in the enclosure having substrate and chips has been performed. A 2-dimensional simulation model is developed by considering heat transfer by conduction, convection and radiation. The solutions to the equation of radiative transfer are obtained by the discrete ordinates method using S-4 quadrature. The effects of Rayleigh number and the substrate-fluid thermal conductivity ratio on the cooling of chip are analyzed. The result shows that radiation is the dominant heat transfer mode in the enclosure.

• 한국환경과학회지
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• 제4권3호
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• pp.197-206
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• 1995

Surface heat balance of the northern sea of Cheju Island for summer in 1993 and 1994 is analyzed using the observation data obtained by Marine Research Institute, Cheju National University. Each flux elements at the sea surface is derived from the marine meteorological reports with application of an aerodynamical bulk method for the turbulent heat fluxes, and empirical formulae for the long-wave radiation heat fluxes. The flux divergence of oceanic heat transport and the rate of heat storage in the ocean are estimated as residual. The features of the surface heat balance are mainly decided by the solar radiation flux and the latent heat flux for 199B. But the Bowen Ratios were large for 1993. This means that the sensible heat fluxes were nearly equal to the latent heat fluxes for 1993. In this period, mean flux divergence of oceanic heat transport is about 130 W/$m^2$.

• 방사선산업학회지
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• 제18권3호
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• pp.227-233
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• 2024

Polyolefins (PO) are used in various industrial fields due to their excellent mechanical properties, processability, and chemical resistance. However, they have low flame retardancy, and when exposed to high temperatures, there are problem that mechanical properties deteriorate due to oxidation. In this study, we developed PO/metal hydroxide composites that exhibit excellent mechanical strength, heat resistance, and flame retardancy by using antioxidants and radiation crosslinking technology. To improve mechanical strength, heat resistance, and flame retardancy, PO/metal hydroxide/antioxidant composites were prepared and irradiated with an electron beam. Specifically, at temperatures above 200℃, the PO/metal hydroxide composites with primary and secondary antioxidants added and irradiated with a 100 kGy electron beam exhibited excellent thermal stability with a thermal shrinkage rate of less than 3%. In addition, the flame retardancy of the PO/metal hydroxide/antioxidant composites was improved due to enhanced thermal stability from electron beam irradiation and reduced thermal decomposition rate from the antioxidants. These results indicate that radiation crosslinking and antioxidants are effective method to simultaneously achieve mechanical properties, heat resistance, and flame retardancy.

• Journal of Mechanical Science and Technology
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• 제14권12호
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• pp.1403-1411
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• 2000

Heat losses from the receivers for a dish-type solar energy collecting system constructed at Korea Institute of Energy Research are analyzed. The Stine and McDonald's model is used to estimate the convection loss. The Net Radiation method and the Monte-Carlo method are used to calculate the radiation heat transfer rate from the inside surface of the receiver to the surroundings. Two different receivers are suggested here and the performances of the receivers are estimated and compared with each other based on the prediction of the amount of heat losses from the receivers. The effects of the receiver shape and the radiation properties of the surface on the thermal performance are investigated. The performance of Receiver I is better than that of Receiver II, and the amount of solar irradiation that is not captured by the captured by the receiver after being reflected by the concentrator becomes significant if the temperature of the working fluid is low.

• 대한기계학회논문집B
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• 제35권5호
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• pp.467-472
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• 2011

본 연구는 LED 조명기구와 같은 원형 모양에 적합한 원형 히트싱크의 주위의 열유동을 실험 및 해석적으로 분석하였다. 기존 복사 열전달을 고려하지 않은 상관식을 이용하여, 추가적으로 복사 열전달을 해석적으로 계산하였다. 본 해석 모델의 타당성을 실험적으로 확인하였다. 이 모델을 바탕으로 휜의 형상 및 열유속을 인자로 하여 히트싱크 평균 온도의 변화를 살펴보았다. 그 결과 열전달 성능을 최대로 할 수 있는 최적 휜의 길이가 존재하였고, 방사율이 클수록 형상 인자의 변화가 복사 열전달 변화에 미치는 영향이 상대적으로 감소하였다.

• 한국산학기술학회논문지
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• 제9권6호
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• pp.1565-1568
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• 2008

본 논문은 LED조명기구의 상용화에 문제가 되고 있는 방열설계에 관한 논문으로서, CF-design을 이용한 방열해석을 통하여 문제해결의 방법을 제시한다. 해석 결과 시뮬레이션 값과 시작품 제작 후 측정 온도와의 차이가 6[$^{\circ}C$]이하로 도출되었으며 주어진 제 요소들을 잘 활용하면 실제작품의 목표치에 근접하는 결과를 얻을 수 있다.

• 한국태양에너지학회 논문집
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• 제34권1호
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• pp.39-47
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• 2014

Solar applications analysis and building energy performance depend on the quality of the solar resource data available. Unfortunately, most of the weather stations do not measure solar radiation data in Korea, as a reason many researchers have studied different solar radiation estimation models and suggested to apply them to various locations in Korea. In addition, they also studied the impact of hourly global solar radiation on energy performance of an office building by comparing the simulated building energy consumptions using four different weather files, one using measured, and three estimated solar radiation from different models, which are Cloud-cover Radiation Model (CRM), Zhang and Huang Model (ZHM), and Meteorological Radiation Model (MRM), and concluded that there was some impact on energy performance of the building due to the using different solar radiation models. However, the result cannot be applied to all other buildings since the simulated office building for that study only used limited building characteristics such as using fixed values of solar heat gain coefficient (SHGC) and window-to-wall ratio (WWR), which are significant parameters related to solar radiation that affect to the building energy consumptions. Therefore, there is a need to identify how the building energy consumption will be changed by varying these building parameters. In this study, the impact of one measured and three estimated global solar radiation on energy performance of the office building was conducted taking account of SHGC and WWR. As a result, it was identified that the impact of four different solar radiation data on energy performance of the office building was evident regardless SHGC and WWR changes, and concluded that the most suitable solar models was changed from the CRM/ZHM to the MRM as SHGC and WWR increases.

• 한국가시화정보학회지
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• 제13권3호
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• pp.24-28
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• 2015

The temperature of the wafer batch in the furnace was calculated and its visualized temperature field was analyzed. The main heat transfer mechanisms from the heater wall to the wafers were radiation and conduction, and the finite difference method was used to analyze the complex heat transfer including those two mechanisms. The visualized temperature field shows that the direction of the heat flux in the wafer batch varies during the heating process, and the heat in the wafer batch diffuses faster by conduction within the wafer than by radiation between the wafers, in the condition of the constant temperature at the heater wall and cap.

• 대한기계학회논문집
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• 제17권10호
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• pp.2582-2589
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• 1993

Transient heat transfer characteristics of cooling of a spherical body were investigated in the radiatively active spherical medium. Initially the spherical body and the medium were maintained at their constant temperatures. Then heat transfer begins from spherical body t medium. The heat transfer mode inside the spherical body is just conduction. But heat is transferred by both conduction and radiation inside the medium. All thermodynamic properties were held constant in time. Spherical symmetry is assumed. DOM was adopted to solve RTE. The effect of characteries-tic optical thickness, conduction to radiation parameters, and solid surface emissivity has been studied.