• 대한기계학회논문집B
• /
• 제23권1호
• /
• pp.104-113
• /
• 1999

A hybrid spatial differencing scheme for the discrete ordinates method is proposed to predict radiative heat transfer in two-dimensional rectangular enclosures. Since this scheme takes the advantages of the diamond scheme and step scheme and includes the characteristics of medium, more accurate and stable results can be obtained. In its development several spatial differencing schemes are examined to address the effect of numerical smearing (or false scattering). Predictions from the proposed hybrid scheme are compared to those of other schemes for transparent, purely absorbing, purely scattering, or absorbing-emitting-isotropically scattering media. It is found that the proposed scheme predicts stable and less smeared results than others.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집B
• /
• pp.347-352
• /
• 2000

In the present study, DOM and FVM have been used to analyze the radiative heat transfer in an axisymmetric cylindrical enclosure with obstacles. Heat flux distributions on the wall of enclosure form DOM and FVM are compared to those from simplified zone analysis for a nonparticipating medium. The comparison of DOM and FVM is also presented. Results show that there is a good agreement between FVM and simplified zone analysis. In addition, the effect of the thickness of the obstacle on the results is considered. Heat flux distribution on the surface of the obstacle is also presented.

• 대한기계학회논문집B
• /
• 제27권6호
• /
• pp.796-803
• /
• 2003

The discrete ordinates interpolation method (DOIM) has shown good accuracy and versatile applicability for the radiation $problems^{(1,2)}$. The DOIM is a nonconservative method in that the intensity and temperature are computed only at grid points without considering control volumes. However, when the DOIM is used together with a finite volume algorithm such as $SIMPLER^{(3)}$, intensities at the control surfaces need to be calculated. For this reason, a 'quadratic' and a 'decoration' schemes are proposed and examined. They are applied to two kinds of radiation problem in one-dimensional geometries. In one problem, the intensity and temperature are calculated while the radiative heat source is given, and in the other, the intensity and the radiative heat source are computed with a given temperature field. The quadratic and the decoration schemes show very successful results. The quadratic scheme gives especially accurate results so that further decoration may not be needed. It is recommended that the quadratic and the decoration schemes may be used together, or, one of them may be applied for control volume radiative energy balance.

• 대한기계학회논문집B
• /
• 제24권6호
• /
• pp.814-821
• /
• 2000

The Discrete Ordinates Interpolation Method (DOIM) is tested in three-dimensional enclosures. The radiative transfer equation (RTE) is solved for a linear source term and the DOIM is formulated for a gray medium. Several interpolation methods can be applied to the DOIM scheme. Among them, the interpolation method applicable to an unstructured grid system is discussed. In a regular hexahedron enclosure, radiative wall heat fluxes are calculated and compared with exact solutions. The enclosure has an absorbing, emitting and nonscattering medium and a constant temperature distribution. These results are obtained with varying optical depths (xD = 0.1, 1.0, 10.0). Also, the same calculations are performed in an irregular hexahedron enclosure. The DOIM is applied to an unstructured grid system as well as a structured grid system for the same regular hexahedron enclosure. They are compared with the exact solutions and the computational efficiencies are discussed. When compared with the analytic solutions, results of the DOIM are in good agreement for three-dimensional enclosures. Furthermore, the DOIM can be easily applied to the unstructured grid system, which proves the reliability and versatility of the DOIM.

• 설비공학논문집
• /
• 제10권1호
• /
• pp.95-107
• /
• 1998

Natural convection and radiation heat transfer in a square enclosure containing absorbing, emitting, and isotopically scattering(participating) media is studied numerically using the finite volume method. Various numerical methods are employed to analyze the radiative heat transfer. However, it is very difficult to choose the proper method. In present study, a finite volume method(FVM) and a discrete ordinates method(DOM) are compared in rectangular enclosure. The SIMPLER algorithm is used to solve the momentum and energy equations. Thermal and flow characteristics are investigated according to the variation of radiation parameters such as optical thickness and scattering albedo. The result shows that the accuracy and the computing time of FVM are better than those of DOM in regular geometry.

• 설비공학논문집
• /
• 제7권2호
• /
• pp.266-275
• /
• 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.

• 설비공학논문집
• /
• 제7권3호
• /
• pp.461-472
• /
• 1995

The interaction of laminar mixed convection and surface radiation in a two-dimensional channel with an array of rectangular blocks is analyzed numerically. Three blocks are maintained at high temperature and the other bottom and top horizontal walls are insulated. Discrete ordinate method(DOM) is introduced to analyze the radiative heat transfer. The effects of the variations of Reynolds number and channel specifications on the heat transfer characteristics are investigated. The average Nusselt numbers along the block surfaces are correlated and presented in terms of Reynolds number and dimensionless geometric parameters such as the block spacing, height and channel spacing. For the conditions considered in this study, average Nusselt numbers along the block surfaces are strongly influenced by the channel spacing and Reynolds number but weakly influenced by the block spacing and block height.

• 대한기계학회논문집
• /
• 제19권12호
• /
• pp.3329-3343
• /
• 1995

The interaction of mixed convection and surface radiation in a printed circuit board(PCB) is investigated numerically. The electronic equipment is modeled by a two-dimensional channel with three hot blocks. In order to calculate the turbulent flow characteristics, the low Reynolds number k-.epsilon. model which is proposed by Launder and Sharma is applied. The S-4 approximation is used to solve the radiative transfer equation. The effects of the Reynolds number and geometric configuration variation of PCB on the flow and heat transfer characteristics are analyzed. As the results of this study, it is found that the thermal boundary layer occured at adiabatic wall in case with thermal radiation included, and the effect of radiation is also found to be insignificant for high Reynolds numbers. It is found, as well, that the heat transfer increases as the Reynolds number and block space increase and the channel height decreases and the heat transfer of vertical channel is greater than that of horizontal channel.

• 대한기계학회논문집B
• /
• 제20권10호
• /
• pp.3344-3354
• /
• 1996

An experimental and numerical study on the three-dimensional natural convection-radiation conjugate heat transfer in the enclosure with heat generating chip has been performed. A 3-dimensional simulation model is developed by considering heat transfer phenomena by conduction-convection and radiation. Radiative transfer was analyzed with the discrete ordinates method. Experiments are conducted in order to validate the numerical model. Comparisons with the experimental data show that good agreement is obtained when the radiation effect is considered. The effects of the thermal conductivity of the substrate and power level on heat transfer are investigated. It is shown that radiation is the dominant heat transfer mode and the conductivity of the substrate has important effects on the heat transfer in the enclosure.

• 전기화학회지
• /
• 제7권4호
• /
• pp.206-210
• /
• 2004

금속산화물 $(TiO_2,\;RuO_2,\;PbO_2,\;Ni(OH)_2)$과 Prussian blue (PB)를 각각 탄소반죽에 혼합한 후 스크린 프린팅 기법으로 6종의 탄소반죽 전극들을 제작하였다. 제작된 탄소반죽 전극들로 전자혀 시스템을 제작하여 다양한 음료수와 식품에 대한 감응을 0.1M carbonate buffer, pH 9.6완충 용액에 묽힌 후 대시간전류법의 방법으로 측정하였다 얻어진 자료를 주성분 분석법 (principal component analysis; PCA)으로 처리한 후 식음료의 맛을 평가할 수 있도록 2차원 좌표계에 표시하였으며, 그 결과 본 실험에서 제작한 시스템 및 분석법은 다양한 식음료의 종류를 뚜렷이 구분해 낼 수 있음을 확인하였다.