• 설비공학논문집
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• 제3권3호
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• pp.197-205
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• 1991

A numerical study has been performed to investigate two dimensional natural convection heat transfer in a rectangular enclosure with heat sources of constant temperature at the bottom. Calculations were made for various dimensionless heat source lengths, W/L=0.1-0.5, and positions of heat sources at $Gr=2.57{\times}10^6$, Pr=0.71 and Ks/Kf=28.98. For various positions of heat sources, the maximum local Nusselt numbers generally show X=0.81-0.85 at the bottom and X=0.23 at the top. For various dimensionless heat source lengths, the maximum local Nusselt numbers at the bottom show W/L=0.4 for one heat source, W/L=0.2 for two heat sources with fixed centers, W/L=0.5 for two heat sources with moved centers. Finally the maximum heat transfer at the bottom exhibits in condition of W/L=0.4 for two heat sources with moved centers.

• 설비공학논문집
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• 제10권1호
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• pp.95-107
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• 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.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1595-1607
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• 1997

The natural convection of a horizontal layer heated from below in a three-dimensional rectangular enclosure was dealt with both numerically and experimentally. The aspect ratios are 1:2:3.5 and Boussinesq fluid is water with the Prandtl number of 5.0. This experimental study showed how to measure the variation of temperature field in a 3-D rectangular enclosure with small aspect ratios by using TLC(Thermochromic Liquid Crystal) and color capturing technique. The experimental temperature field had periodic characteristics of 75 sec at Ra=2.37*10$^{5}$ . But the numerical convection flow had periodic characteristics of 79 sec at the same Rayleigh number. In three dimensional computation it was found that the convection roll structure bifurcated from four rolls to two rolls as the Rayleigh number is increased.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.925-931
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• 2016

In this study, laminar natural circulation and heat transfer in a tall rectangular enclosure with disconnected vertical partitions inside were investigated. Analytical expressions were developed to predict the circulation flow rate and the average Nusselt number in a partially partitioned enclosure with isothermal side walls at different temperatures and insulated top and bottom walls. The proposed formulas are then validated against numerical results for modified Rayleigh numbers of up to $10^6$. The impacts of the governing parameters are also examined along with a discussion of the heat transfer regimes.

• 대한설비공학회지:설비저널
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• 제16권2호
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• pp.204-215
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• 1987

Laminar natural convective heat transfer within a two-dimensional rectangular enclosure with horizontal conducting walls and partitions was investigated by numerical analysis and experiment. The enclosure consists of two isothermal vertical walls and two adiabatic horizontal walls. This combined heat transfer problem of conduction and natural convection was solved using finite difference method with SIMPLE algorithm, and temperature distribu-tions in the air filled enclosure was obtained using Mach-Zehnder interferometer. Good agree-ment was obtained between the predicted and measured results. The effect of geometric parameters and thermal properties on heat transfer was studied far Grashof numbers in range, $1\times10^4\;{\leqslant}\;G^r\;{\leqslant}\;6.4\times10^5.$ It was found that both velocity and temperature fields were in-fluenced significantly by thermal conductivity of the conducting walls and the partitions, and by geometry of partitions.

• 대한기계학회논문집
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• 제10권2호
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• pp.247-256
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• 1986

본 연구에서는 종횡비가 0.2인 직각 밀폐용기내에서 소금물을 시험유체로 하여 양단의 온도 및 농도차가 수평방향으로 가해지는 경우(CASE 1,2) 밀폐용기내 에서의 유동현상과 열전달 특성을 온도 및 농도분포, 흐름의 가시화를 통해 실험적 으로 관찰, 조사하였다

• 대한기계학회논문집
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• 제13권6호
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• pp.1330-1338
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• 1989

본 연구에서는 직각밀폐용기의 수평경계면이 단열인 경우뿐만 아니라 등온 조건을 갖는 경우에 대해 실험적으로 연구하여 경계조건의 변화가 직각밀폐용기내 흐름 및 열전달에 미치는 영향, 특히 등온조건을 갖는 경우 수직 온도차에 따르는 안정온도 구배효과로 예상되는 흐름의 억제, 지연효과를 작종 물리적 변수들의 영향과 함께 세밀히 조사하였다.

• 설비공학논문집
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• 제5권4호
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• pp.249-256
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• 1993

Numerical method is applied to predict the time variation behavior of flammable mixture formation in a two dimensional enclosure from the beginning of gas leak. Additionally experimental method is used to consider qualitative aspects. Characteristics of flammable mixture formation such as distribution of flow and fuel mass fraction at various locations in the enclosure are determined for the following parameters: the various locations of leak at the bottom and aspect ratio of the enclosure. In the case of gas leak with small leak velocity from the bottom of enclosure gravitational force affects the formation of flammable mixture. Aspect ratio of the enclosure also affects the formation of flammable mixture. The volume of the region of recirculating flow is dominant factor affecting the formation mixture.

• 소음진동
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• 제7권3호
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• pp.457-466
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• 1997

The experimental and analytical study was conducted to determine the noise transmission characteristics of acoustically loaded steel plate of rectangular enclosure and to investigate the sound radiation characteristics through out the enclosure. The vibrations of acoustically loaded plate give rise to sound radiations and generate the reverberant space that the sound field exists very close to a vibrating plate. Acoustic transmission loss is measured from the incident intensity into the plate and the transmitted intensity through out the plate. Sound radiation patterns are measured from both acoustic intensity technique and surface intensity technique. Those resultant patterns and vibrational modes are vital in understanding the relations between vibration and noise in the near field out of vibrating plate.

• 설비공학논문집
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• 제9권3호
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• pp.268-275
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• 1997

Using the film-based particle image velocimetry, natural convective flows have been measured quantitatively in a rectangular enclosure with a heater located on the bottom surface. The success rate of the present interrogation method has been obtained as a function of the number of particle pairs and the distance between the particle pairs. The influence of the diffraction halo at the center have been effectively eliminated by rotating-subtracting the original Fourier-transformed image. By utilizing the coded multiple pulsed illumination with two different time intervals, the minimum measurable velocity have been improved. The results of the velocity distributions and the heat transfer correlations have been obtained for different locations of heater in the enclosure.