• Title/Summary/Keyword: radiation of heat

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A Study on the Natural Convection Cooling of Electronic Device Considering Conduction and Radiation (전도와 복사를 고려한 전자 장비의 자연대류 냉각에 관한 연구)

  • Lee, K.S.;Baek, C.I.;Kim, W.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.2
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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.

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Surface Heat Budget of the Northern Sea of Cheju Island for June-August 1993 and 1994 (제주도 북부해역의 표면 열수지 해석 -1993년과 1994년 하계의 경우-)

  • 김해동;양성기
    • Journal of Environmental Science International
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    • v.4 no.3
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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/$m^2$.

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Estimation of Heat Losses From the Receivers for Solar Energy Collecting System of Korea Institute of Energy Research

  • Ryu, Siyoul;Seo, Taebeom
    • Journal of Mechanical Science and Technology
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    • v.14 no.12
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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.

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Heat Transfer from Rectangular Fins with a Circular Base (원형 베이스와 사각 휜 주위의 열전달 해석)

  • Yu, Seung-Hwan;Lee, Kwan-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.5
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    • pp.467-472
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    • 2011
  • The heat transfer over a radial heat sink, adapted for LED (light emitting diode) downlights, was experimentally and analytically investigated. We added radiation heat transfer into a previous calculation that neglected this factor. The numerical results agreed well with experimental results. Parametric studies were performed to compare the effects of the geometric parameters (fin length, fin height, ideal number of fins) and the operating parameter (heat flux) on the average heat-sink temperature from the heat-sink array. We found the fin length that maximizes the heattransfer performance. As the emissivity increased, the effect of geometric parameters on the radiation heat transfer decreased.

Analysis of the Heat Radiation of LED Light Fixture using CF-design (LED조명기구의 CF-Design 방열 해석)

  • Eo, Ik-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.6
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    • pp.1565-1568
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    • 2008
  • This thesis is about the design of heat sink which is the obstacle in commercializing LED light fixture. It suggests a way of solving the problem by the analysis on heat radiation of LED light fixture using CF-design. As a result of the analysis, the difference of simulation value and the measured temperature of proto-type was derived as less than 6[$^{\circ}C$]. Even the results approaching the target value of actual product could be obtained with the given factors well applied.

Impact of Horizontal Global Solar Radiation Calculation Modelson Building Energy Performance Analysis Considering Solar Heat Gain Coefficient and Window-to-wall Ratio (수평면 전일사량 산출모델이 일사열취득계수 및 창면적비를 고려한 건물 에너지 성능분석에 미치는 영향)

  • Kim, Kee Han;Oh, John Kie-Whan
    • Journal of the Korean Solar Energy Society
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    • v.34 no.1
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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.

Analysis and Visualization of Temperature Field for Wafer Batch in Furnace (반응로 내 웨이퍼 배치의 온도장 분석 및 가시화)

  • Kang, Seung-Hwan;Lee, Seung Ho;Kim, Byeong Hoon;Ko, Han Seo
    • Journal of the Korean Society of Visualization
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    • v.13 no.3
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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.

Unsteady Heat Transfer in Radiatively Active Spherical Medium (구형 복사 매질에서의 비정상 열전달 특성에 관한 연구)

  • 한상헌;백승욱;안국영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.10
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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.

Thermal radiation and some physical combined effects on an asymmetric peristaltically vertical channel of nanofluid flow

  • Amira S. Awaad;Zakaria M. Gharsseldien
    • Advances in nano research
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    • v.16 no.6
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    • pp.579-591
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    • 2024
  • This study explained the effects of radiation, magnetic field, and nanoparticle shape on the peristaltic flow of an Upper-Convected Maxwell nanofluid through a porous medium in an asymmetric channel for a better understanding of cooling and heating mechanisms in the presence of magnetic fields. These phenomena are modeled mathematically as a system of non-linear differential equations, that are solved under long-wavelength approximation and low Reynolds number conditions using the perturbation method. The results for nanofluid and temperature described the behavior of the pumping characteristics during their interaction with (the vertical position, thermal radiation, the shape of the nanoparticle, and the magnetic field) analytically and explained graphically. Also, the combined effects of thermal radiation parameters and some physical parameters on pressure rise, pressure gradient, velocity, and heat distribution are pointed out. Qualitatively, a reverse velocity appears with combined high radiation and Grashof number or combined high radiation and low volume flow rate. At high radiation, the spherical nanoparticle shape has the greatest effect on heat distribution.

Thermal Effect of the Transparent Insulated Opaque Envelopes (투명 단열외피의 열적성능에 관한 연구)

  • Kim, Se-Hwan;Lee, Sung
    • The Journal of Sustainable Design and Educational Environment Research
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    • v.4 no.4
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    • pp.19-24
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    • 2004
  • The thermal effect of a transparent insulated opake wall with solar energy was investigated theoretically. The heat gain through transparent insulated opake wall was studied for relative simple conditions. The stationary heat transport effect was studied for layer which is built on the opake wall. This study shows that a relative low solar radiation intensity causes a great heat reduction through the transparent insulated opake wall. Because the transparent insulation layer is mostly transparent to solar radiation, it is opaque to heat radiation.

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