• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.427-432
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• 2020

In this study, a multi-zone furnace analysis method that couples a 1D energy and mass balance calculation with a 3D radiative heat transfer calculation is tested in order to verify its reliability. The calculated results for a domestic 500 MW capacity coal-fired boiler furnace were compared with the design data of the boiler manufacturer and CFD analysis, and a good agreement was achieved. Although this calculation method is less sophisticated than the CFD furnace analysis, it has an advantage in terms of calculation time while being able to provide the furnace behavior according to the fuel characteristics and operational variable changes. Therefore, it is expected to be useful for boiler operation diagnosis and daily fuel/operation planning.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.461-472
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• 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.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.20-26
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• 2019

This study was conducted on cooling systems in which, for the first time at home and abroad, cold water panels are embedded in the walls of small buildings for radiant cooling by heat absorption with cold water. In summer, cold water is circulated through cold water (chiller) circulation tubes embedded in three walls (two side walls and one rear wall) of a building to implement radiant cooling by the coldness of the water. From the results of this study, the experimental and theoretical natural convection heat transfer coefficients were relatively well-matched over the entire experimental range, thereby verifying the reliability of the experimental results. The surface temperature reduction rate of the walls in which cold water panels are embedded was large whereas that of the walls where no cold water panels are embedded was very small.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.640-647
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• 2014

Infrared signature of aircraft exhaust plume is the critical factor for aircraft survivability. To improve the military aircraft survivability, the accurate prediction of infrared signature for the propulsion system is needed. The numerical analysis of thermal fluid field for nozzle inflow, free stream flow, and plume region is conducted by using the in-house code. Weighted Sum of Gray Gases Model based on Narrow Band with regrouping is adopted to calculate the spectral infrared signature emitted from aircraft exhaust plume. The accuracy and reliability of the developed code are validated in the one-dimensional band model. It is found that the infrared radiant intensity is relatively more strong in the plume through the analysis, the results show the different characteristic of the spectral infrared signature along the temperature, the partial pressure, and the species distribution. The continuous spectral radiant intensity is shown near the nozzle exit due to the emission from the nozzle wall.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.497-508
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• 2013

This paper introduces a numerical model which can evaluate the fire-resistant capacity of reinforced concrete members. On the basis of the transient heat transfer considering the heat conduction, convection and radiation, time-dependent temperature distribution across a section is determined. A layered fiber section method is adopted to consider non-linear material properties depending on the temperature and varying with the position of a fiber. Furthermore, effects of non-mechanical strains of each fiber like thermal expansion, transient strain and creep strain are reflected on the non-linear structural analysis to take into account the extreme temperature variation induced by the fire. Analysis results by the numerical model are compared with experimental data from the standard fire tests to validate an exactness of the introduced numerical model. Also, time-dependent changes in the resisting capacities of reinforced concrete members exposed to fire are investigated through the analyses and, the resisting capacities evaluated are compared with those determined by the design code.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.126-132
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• 2016

This study numerically investigates the characteristics of chemical reactions and thermal deformation in a steam reformer. These phenomena are significantly affected by the high-temperature burner gas and the process gas conditions. Because the high temperature of the burner gas ranges from 800 to 1000 K, the reformer tubes undergo substantial thermal deformation, eventually resulting in structural failure. Thus, it is necessary to understand the characteristics of the reaction and thermal deformation under the operating conditions to evaluate the reformer tubes for sustainable, stable operation. Extensive numerical simulations were carried out using commercial CFD code (ANSYS FLUENT/MECHANICA Ver. 13.0) while considering three-dimensional turbulent flows and combined heat transfer including conduction, convection, and radiation. Structural analysis considering conjugated heat transfer between solid tubes and fluid flows was conducted using the Fluid-Solid Interaction (FSI) method. The results show that when the injection temperature of the process gas and burner gas decreased, the hydrogen production rate decreased significantly, and thermal deformation decreased by at least 15 to 20%.

• Journal of Bio-Environment Control
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• v.32 no.1
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• pp.48-56
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• 2023

High-pressure sodium (HPS) lamps have been widely used as a useful supplemental light source to emit sufficient photosynthetically active radiation and provide a radiant heat, which contribute the heat requirement in greenhouses. The objective of this study to analyze the thermal characteristics of HPS lamp and thermal behavior in supplemented greenhouse, and evaluate the performance of a horizontal leaf temperature of sweet pepper plants using computational fluid dynamics (CFD) simulation. We simulated horizontal leaf temperature on upper canopy according to three growth stage scenarios, which represented 1.0, 1.6, and 2.2 plant height, respectively. We also measured vertical leaf and air temperature accompanied by heat generation of HPS lamps. There was large leaf to air temperature differential due to non-uniformity in temperature. In our numerical calculation, thermal energy of HPS lamps contributed of 50.1% the total heat requirement on Dec. 2022. The CFD model was validated by comparing measured and simulated data at the same operating condition. Mean absolute error and root mean square error were below 0.5, which means the CFD simulation values were highly accurate. Our result about vertical leaf and air temperature can be used in decision making for efficient thermal energy management and crop growth.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.54-63
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• 2004

The inner surface temperatures of the KSR-III Sounding Rocket launched at 29th November 2002 were measured in the flight test, and the aerodynamic heating rate and outer surface temperature were calculated. The used program is the MINIVER code, which calculate the boundary layer equation based on the theoretical analysis, and its calculation is simulated on the flight time histories. The analysis considered the inner surface heat transfer with one dimensional solid heat conduction. The results showed that the major interior heat transfer is the radiation heat transfer, and the maximum outer surface temperature due to aerodynamic heating reached to $223^{\circ}C$ at fin and the maximum heating rate is about $133kW/m^2$ at nose cap. The whole analysis proved that the surface temperature remained below the allowable temperature, and the KSR-III thermal design satisfies the thermal environmental conditions.

• Journal of the korean Society of Automotive Engineers
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• v.6 no.2
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• pp.14-19
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• 1984

종래에 많이 사용된 각양의 계측 방법을 일일이 설명하는 것은 본 해설의 목적이 아니기 때문에 개략적으로 분류하여 설명하면 다음과 같다. 1) 시간 평균유속은 주로 프로브(probe)를 경유하여 동압과 정압의 측정에 의하여 수행되어 왔다. 연소반응이 있으면 밀도의 변화가 있게 되는데 밀도는 후술하는 농도의 계측과 온도의 계측에 의하여 정해져 동압과 정압으로부터 유속으로 변환된다. 시간분해능이 높은 비접촉식(직접 프 로브를 측정부에 삽입하지 않는 방법) 유속측정이 가능한 방법으로는 레이저 도플러 유속계 (Laser Doppler Velocimetry, 이하 LDV로 표현)를 들 수 있다. LDV는 압력측정에 의한 유속 산출법에서와 같은 온도 및 농도 등의 부수적인 계측이 필요없이, 직접 유속을 검출할 수 있으며 또한 검정이 필요없는 절대유속 측정이 가능하며 현재 연소반응이 있는 흐름에 대한 대부분의 연구에 적용되고 있는 실정이다. 2) 시간평균 화학종 농도측정에 가장 많이 쓰이는 방법은, 연소가스를 채취하여 가스 크로마토 그라프(Gas Chromatograph)로 분석하는 것을 들 수 있다. 한편, 시간 분해능이 높은 화학종 농 도의 계측은 레이저를 사용하여 각 화학종의 발광, 산란 및 흡수성을 이용, 측정한다. 3) 온도측정은 대부분 열전대를 사용하고 있다. 그러나 이 방법은 직접 프로브를 삽입해야 하므로 사용한계의 범위가 지극히 좁으며, 연소반응이 일어나므로 프로브 자체의 촉매반응 및 복사 열전달에 의한 보정 등이 사용상 큰 문제로 제기된다. 그러나 최근 레이저 이용기술의 발달로 (2)항에서의 농도 계측과 같이 반응기체의 온도 및 성분의 동시측정이 가능한 방법도 점차 현 실화 되어가고 있다. 그 대표적인 예로 CARS법(Coherent Anti-Stokes Raman Spectroscopy)을 들 수 있다. 이상으로부터 연소반응이 일어나는 흐름에서의 각종 계측에서는, 비접촉 측정의 가능성과 시간 공간 분해능의 특징으로 미루어 앞으로는 레이저를 이용한 계측 방법이 그 주류를 이룰 것으로 사료된다. 우선 본 해설은 기체의 온도 및 농도의 광학적 측정방법중 Raman산란광 검출법에 대하여 실제로 측정하는 입장에서 간단히 소개한다.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.28-39
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• 1998

This study investigated the natural convection and radiation in a rectangular enclosure with ceiling vent experimentally and numerically. A heat source is located on the center of the bottom surface. The analysis was peformed a pure convection and is combination of natural convection and radiation. The shape of the considered two dimensional model is a square whose center of ceiling($30\%$) is opened. The numerical simulations are carried out for the pure natural convection case and the combined heat transfer case by using the SIMPLE algorithm. For the turbulent flow, Reynolds stresses are closed by the standard $k-{\epsilon}$ model and the wall function is used to determine the wall boundary conditions. The experiment was performed on the same geometrical shape as the computations. The radiative heat transfer is analized by the S-N discrete ordinates method. The results of pure natural convection are compared with those of combined heat transfer by the velocity vectors, stream lines, isothermal lines. The results obtained are as follows 1. Comparing the results of pure convection with those of the combined convection-radiation through the shape of stream lines, isothermal lines are similar to each other. 2. The temperature fields obtained by numerical method are compared to those obtained by experimental one, and it is found that they are showed mean relative error $8.5\%$. 3. Visualization bt smoke is similar to computational results.