• Atmosphere
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• v.22 no.4
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• pp.429-436
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• 2012

The performances of the Seoul National University Urban Canopy Model (SNUUCM) under different meteorological conditions (clear, cloudy, and rainy conditions) in summertime are compared using observation dataset obtained at an urban site. The daily-averaged net radiation, sensible heat flux, and storage heat flux are largest in clear days and smallest in rainy days, but the daily-averaged latent heat flux is similar among clear, cloudy, and rainy days. That is, the ratio of latent heat flux to net radiation increases in order of clear, cloudy, and rainy conditions. In general, the performance of the SNUUCM is better in clear days than in cloudy or rainy days. However, the performance in simulating sensible heat flux in clear days is as poor as that in rainy days. For all the meteorological conditions, the performance in simulating latent heat flux is worst among the performances in simulating net radiation, sensible heat flux, and latent heat flux. The normalized mean error for latent heat flux is largest in rainy days in which the relative importance of latent heat flux in the surface energy balance becomes greatest among the three conditions. This study suggests that improvements to the parameterization of processes that are related to latent heat flux are particularly needed.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.4
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• pp.179-186
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• 2009

Electronic components in an enclosure have been investigated to prevent undesired thermal problems. The electronic devices, such as ECUs of automotive engines, are operated under the contaminated environments, so that they rely on the passive cooling without any fluid-driving methods. Therefore the radiation heat dissipation plays more important role than the conduction and convection heat transfer. Hence their combined heat dissipation phenomena have been simulated by a numerical model to reveal the effects of supplied heat flux, emissivity of material, geometry of enclosure, charging gas and pressure. The result showed that the radiation had a significant effect on the heat dissipation of module in an enclosure, and some space above the module should be reserved to prevent its thermal problem. In addition, the higher thermal conductivity and pressure of gas in an enclosure could be necessary to improve the thermal dissipation from the electronic devices.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.46-50
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• 2012

This paper amis at improving the heat radiation performance of thermoelectric module (TEM) for a commercialization of high-powered LED light with using a multichip LED module. In addition, a 10W multichip LED light was prepared for the heat performance on radiating of which LED light was made for a use of testing by the driving of the thermoelectric module. So, it was found that about 30% in the effect of temperature reduction was confirmed if compared with the radiation heat by heat sink only.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.2
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• pp.173-181
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• 1989

Until recently there was a lack of reliable performance data for the design and operation of Ondol heating systems. This paper presents a calculation method on heat flux from Ondol floor surface. Total heat flux from floor consists of radiation and convection component. In order to analyse the characteristics of both radiation and convection heat flux, each surface temperature is measured and several temperatures near each wall are measured vertically and horizontally in a practical Ondol heating space. Radiation heat flux is calculated and analysed by Gebhart's Absorption Factor Method with the consideration of instantaneous radiant exchanges. Convection heat output is derived from the vertical temperature profiles near floor. The vertical temperature profiles could be expressed by nonlinear regression equation models and convection coefficients could be estimated by the equations. As a result, radiation, convection and total heat flux are suggested by the expression of difference between floor surface and room air temperature.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1639-1644
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• 1990

Effects of radiation on the wall-friction and heat transfer in the convergent and divergent nozzle of a rocket motor are investigated in the present paper. Radiative heat transfer cools down the core gas, and the decrease in the gas temperature reduces the convective heat transfer on the wall. Radiation heat transfer is estimated by using mean-beam-length approach and core flow is assumed to be one-dimensional isentropic. The compressible thermal boundary layer is solved by a finite difference method. The Cebeci-Smith eddy viscosity model is adopted for the present study. Convective heat transfer is reduced at the throat of the nozzle and is almost compensated with an increase in radiative transfer. In the sequel total heat transfer rate is slightly reduced. However, radiation heat transfer is dominant in the converging part of the nozzle.

• Journal of the Korean housing association
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• v.15 no.3
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• pp.93-99
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• 2004

This study was conducted to estimate the solar energy, as an alternative energy evaluating an effect of solar radiation on indoor space of residential building. The basic data of solar radiation which is useful for architectural design was suggested using theoretical and experimental analysis. Accordingly, this study was carried out measuring the solar energy using Explicit Method. These results were compared with the results using steady state heat transfer method. The results of this study are summarized as follows; Based on the results using Explicit Method and steady state heat transfer on the indoor space of building, it was shown that an analysis on heat transfer using Explicit Method is more sensitive to the outdoor environmental changes. The results using Explicit Method to analysis and evaluate the solar radiation should be used for residential building design.

• Journal of Environmental Science International
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• v.25 no.8
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• pp.1057-1063
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• 2016

The heat budget is investigated in the Gumi Reservoir of the Nakdong river. In warm climate season, solar radiation effects play a important role in the change of water temperature. The features of the surface heat balance are almost derived by the latent heat flux and the solar radiation flux. On the other hand, in cold climate season, change of heat stored in the water is mainly dominated by latent and sensible heat transfer between water and air, since flux of solar radiation and loss of outgoing long wave radiation balance approximately. For the annual averages, net flux of radiation, evaporation(latent heat) loss are dominant in the Gumi reservoir. The evaporation losses are dominant from spring to early winter. This means that the Gumi reservoir rolls like a lake of thermal medium or deep depth.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.58-61
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• 2019

The aim of this study is to quantitatively demonstrate the possibility of heat transfer by thermal radiation by comparing heat transfer by conventional heat transfer and radiation by radiation. 1) The heat transfer was measured by using filler of TIM material with low thermal conductivity (CuS). As a result, heat transfer was easier than ceramic with high thermal conductivity ($Al_2O_3$ and $Si_3N_4$). 2) The reason for this is thought to be that the infrared wave due to radiation of the air diaphragm has moved easily. 3) From the above results, the heat dissipation of the TIM material indicates the possibility of heat transfer by thermal radiation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.9
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• pp.2933-2943
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• 1996

A grating composed of elliptical cylinders (GEC), specially designed, is applicable to control of radiation heat transfer from a heated surface, as reported in our previous work. In this study, an analysis of radiation heat transfer is performed for a physical model in which the GEC is placed in front of a heated black-base surface and the major axes of the elliptical cylinders are inclined as a certain angle from the normal to the row of elliptical cylinders. Numerical solutions are obtained. Variations of the direction and the radiative energy concentration with slant angle of the major axis are shown for some parameters. It is verified that the GEC is able to widely change the direction of radiation heat transfer from the heated surface.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.170-178
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• 2005

Multi-hole type oxygen combustion burner was developed for industrial gasification and smelting furnace. We investigated characteristics of flame, radiation transfer, and soot emission in the convectional oxygen burner with respect to the feeding condition of fuel and oxygen. Regarding the results of the conventional burner, we designed new burners which have larger fuel consumption rate and radiation heat transfer. We changed the size and hole number and shape of the exit plane of the burner. In addition, the performance of the burner was tested with respect to the feeding condition of the fuel and air: Normal Diffusion flame(NDF) and Inverse Diffusion Flame(IDF). We investigated the flame configuration, radiation heat transfer, and soot formation by using a CCD camera, heat flux meter, and Laser Induced Incadescence(LII), respectively. The stable operating condition was obtained by the flame configuration and the flame of the burner which has dented exit plane was more stable in whole operating conditions. The characteristics of radiative heat transfer were sensitive to the feeding condition of reactants and the flame of 75% primary oxygen and 25% secondary oxygen of the IDF case shows maximum radiation heat transfer. The soot volume fraction of the flame was measured in the axial direction of the flame and the amount of soot volume fraction is proportion to the radiation heat transfer. As a result, we can get the optimal operating condition of the newly designed burner which enhances the characteristics of flame stabilization and radiation heat transfer.