• Title/Summary/Keyword: Thermal Radiation Analysis

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PRELAUNCH THERMAL ANALYSIS OF KSLV-I PAYLOAD FAIRING

  • Choi Sang-Ho;Kim Seong-Lyong;Kim Insun
    • Bulletin of the Korean Space Science Society
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    • 2004.10b
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    • pp.356-359
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    • 2004
  • Prelaunch thermal analysis of the KSLV (Korea Space Launch Vehicle)-I PLF (Payload Fairing) was performed to predict maximum/minimum liftoff temperatures and to evaluate of air conditioning performance. Prelaunch thermal analysis includes internal air conditioning effect, external convective heating/cooling, radiation exchange with the ground and sky, radiation between spacecraft and PLF, and solar radiation incident on PLF. Analysis was performed at two extreme conditions, hot day condition and cold day condition. The results showed that the maximum liftoff temperature was $53^{\circ}C$ and the minimum liftoff temperature was $-3.8^{\circ}C$. It was also found that conditioned air supplying, in $20{\pm}2^{\circ}C\;and\;1200\;m^3/hr$, is sufficient to keep the internal air in required temperature range.

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Radiation Effects on ${\gamma}$-Ray Irradiated Ethylene Propylene Rubber using Dielectric Analysis

  • Kim, Ki-Yup;Ryu, Boo-Hyung;Lee, Chung;Lim, Kee-Joe
    • KIEE International Transactions on Electrophysics and Applications
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    • v.3C no.2
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    • pp.48-54
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    • 2003
  • To evaluate the radiation degradation of ethylene propylene rubber (EPR), radiation effects on EPR were investigated by using dielectric analysis and thermal-gravimetric analysis. Permittivity, loss factor, tan$\delta$, and thermal decomposition temperature were observed for ${\gamma}$-ray irradiated EPR. As the radiation dose was increased, the peak temperature of the loss factor and tans of EPR were increased and loss factor and tan$\delta$ at peak temperature were decreased. Activation energies were calculated using loss factor and thermal decomposition for ${\gamma}$-ray irradiated EPR as well. The trends of both calculated activation energies showed the same tendencies as radiation dose was increased.

Analysis of Passive Cooling Effect of the Tree by Field Observations in the Summer (하절기 단일 수목의 열 환경 관측을 통한 서열완화 효과 해석)

  • Choi, Dong-Ho;Lee, By-Yong
    • Journal of the Korean Solar Energy Society
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    • v.26 no.4
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    • pp.109-118
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    • 2006
  • The tree is regarded as an sustainable architectural outdoor design element which reduce urban heat island effect by its solar shading and evapotranspiration. This study carried out field observations of measuring thermal environment of selected tree and its ambience to determine passive cooling effects. Results from the field observations are as below; Tree-shading effect to the thermal environment can not be properly evaluated by merely measuring air temperature differences between tree-shaded space and unshaded space for the maximum temperature difference is less than $1.5^{\circ}C$. The differences of longwave radiation and shortwave radiation between tree-shaded space and unshaded space are measured. Shortwave radiation is considered as a main thermal comfort determining factor for the difference of the shortwave radiation is much bigger than that of longwave radiation. By thermal infrared image analysis, the surface temperature of the tree under strong solar radiation is measured same as ambient air temperature. By which the evapotranspiration is considered to retard tree surface temperature raising effectively.

Radiation-induced thermal conductivity degradation modeling of zirconium

  • Sangil Choi;Hyunmyung Kim;Seunghwan Yu
    • Nuclear Engineering and Technology
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    • v.56 no.4
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    • pp.1277-1283
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    • 2024
  • This study presents a radiation-induced thermal conductivity degradation (TCD) model of zirconium as compared to the conventional UO2 TCD model. We derived the governing factors of the radiation-induced TCD model, such as maximum TCD value and temperature range of TCD. The maximum TCD value was derived by two methods, in which 1) experimental result of 32 % TCD was directly utilized as the maximum TCD value and 2) a theoretical approach based on dislocation was applied to derive the maximum TCD value. Further, the temperature range of TCD was determined to be 437-837 K by 1) experimental results of post-annealing of irradiation hardening as compared to 2) the rate theory and thermal equilibrium. Consequently, the radiation-induced TCD model of zirconium was derived to be $f_r=1-{\frac{0.32}{1+{\exp}\,\{(T-637)/45\}}}$. Because the thermal conductivity of zirconium is one of the factors determining the storage and transport system, this newly proposed model could improve the safety analysis of spent fuel storage systems.

Analysis of the Thermal Dome Effect from Global Solar Radiation Observed with a Modified Pyranometer

  • Zo, Ilsung;Jee, Joonbum;Kim, Buyo;Lee, Kyutae
    • Current Optics and Photonics
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    • v.1 no.4
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    • pp.263-270
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    • 2017
  • Solar radiation data measured by pyranometers is of fundamental use in various fields. In the field of atmospheric optics, the measurement of solar energy must be precise, and the equipment needs to be maintained frequently. However, there seem to be many errors with the existing type of pyranometer, which is an element of the solar-energy observation apparatus. In particular, the error caused by the thermal dome effect occurs because of the thermal offset generated from a temperature difference between outer dome and inner casing. To resolve the thermal dome effect, intensive observation was conducted using the method and instrument designed by Ji and Tsay. The characteristics of the observed global solar radiation were analyzed by classifying the observation period into clear, cloudy, and rainy cases. For the clear-weather case, the temperature difference between the pyranometer's case and dome was highest, and the thermal dome effect was $0.88MJ\;m^{-2}\;day^{-1}$. Meanwhile, the thermal dome effect in the cloudy case was $0.69MJ\;m^{-2}\;day^{-1}$, because the reduced global solar radiation thus reduced the temperature difference between case and dome. In addition, the rainy case had the smallest temperature difference of $0.21MJ\;m^{-2}\;day^{-1}$. The quantification of this thermal dome effect with respect to the daily accumulated global solar radiation gives calculated errors in the cloudy, rainy, and clear cases of 6.53%, 6.38%, and 5.41% respectively.

Effect of Gamma Ray Irradiation on the Mechanical and Thermal Properties of MWNTs Reinforced Epoxy Resins

  • Shin, Bum Sik;Shin, Jin Wook;Jeun, Joon Pyo;Kim, Hyun Bin;Oh, Seung Hwan;Kang, Phil Hyun
    • Journal of Radiation Industry
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    • v.5 no.2
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    • pp.137-143
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    • 2011
  • Epoxy resins are widely used as high performance thermosets in many industrial applications, such as coatings, adhesives and composites. Recently, a lot of research has been carried out in order to improve their mechanical properties and thermal stability in various fields. Carbon nanotubes possess high physical and mechanical properties that are considered to be ideal reinforcing materials in composites. CNT-reinforced epoxy system hold the promise of delivering superior composite materials with their high strength, light weight and multi functional features. Therefore, this study used multi-walled carbon nanotubes (MWNT) and gamma rays to improve the mechanical and thermal properties of epoxy. The diglycidyl ether of bisphenol A (DGEBA) as epoxy resins were cured by gamma ray irradiation with well-dispersed MWNTs as a reinforcing agent and triarylsulfonium hexafluoroantimonate (TASHFA) as an initiator. The flexural modulus was measured by UTM (universal testing machine). At this point, the flexural modulus factor exhibits an upper limit at 0.1 wt% MWNT. The thermal properties had improved by increasing the content of MWNT in the result of TGA (thermogravimetric analysis). However, they were decreased with increasing the radiation dose. The change of glass transition temperature by the radiation dose was characterized by DMA (dynamic mechanical analysis).

Analysis of Solar Radiation Components for the Installation of Solar Thermal System in Korea (국내 태양열시스템 설치를 위한 성분일사량 분석)

  • Jo, Dok-Ki;Kang, Young-Heack
    • Journal of the Korean Solar Energy Society
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    • v.29 no.3
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    • pp.12-18
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    • 2009
  • The Knowledge of the solar radiation components are essential for modeling many solar energy systems. This is particularly the case for applications that concentrate the incident energy to attain high thermodynamic efficiency achievable only at the higher temperatures. In order to estimate the performance of concentrating thermal systems, it is necessary to know the intensity of the beam radiation, as only this component can be concentrated. The Korea Institute of Energy Research(KIER) has began collecting solar radiation component data since January, 2002. KIER's component data will be extensively used by concentrating system users or designers as well as by research institutes. The theoretical analysis of solar radiation as a component has compared with the experimental data obtained by the KIER station. The Result of simulation analysis shows that the annual-average daily diffuse radiation on the horizontal surface is $1,457cal/m^2$ and daily direct radiation on the horizontal surface is $1,632cal/m^2$ for all over the 16 areas in Korea.

Efficient Finite Element Heat Transfer Analysis by Decomposing a Domain and Radiation Boundaries (영역 및 복사 경계의 완전 분할을 통한 유한요소 열전달 해석의 효율화)

  • Shin, Eui-Sup;Kim, Yong-Uhn;Kim, Sung-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.10
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    • pp.836-843
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    • 2008
  • An efficient domain/boundary decomposition method is applied for heat transfer problems with non-linear thermal radiation boundaries. The whole domain of solids or structures is considered as set of subdomains, an interface, and radiation interfaces. In a variational formulation, simple penalty functions are introduced to connect an interface or radiation interfaces with neighboring subdomains that satisfy continuity conditions. As a result, non-linear finite element computations due to the thermal radiation boundaries can be localized within a few subdomains or radiation interfaces. Therefore, by setting up suitable solution algorithms for the governing finite element equations, the computational efficiency can be improved considerably. Through a set of numerical examples, these distinguishing characteristics of the present method are investigated in detail.

Analysis of heat-loss mechanisms with various gases associated with the surface emissivity of a metal containment vessel in a water-cooled small modular reactor

  • Geon Hyeong Lee;Jae Hyung Park;Beomjin Jeong;Sung Joong Kim
    • Nuclear Engineering and Technology
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    • v.56 no.8
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    • pp.3043-3066
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    • 2024
  • In various small modular reactor (SMR) designs currently under development, the conventional concrete containment building has been replaced by a metal containment vessel (MCV). In these systems, the gap between the MCV and the reactor pressure vessel is filled with gas or vacuumed weakly, effectively suppressing conduction and convection heat transfer. However, thermal radiation remains the major mode of heat transfer during normal operation. The objective of this study was to investigate the heat-transfer mechanisms in integral pressurized water reactor (IPWR)-type SMRs under various gas-filled conditions using computational fluid dynamics. The use of thermal radiation shielding (TRS) with a much lower emissivity material than the MCV surface was also evaluated. The results showed that thermal radiation was always the dominant contributor to heat loss (48-97%), while the conjugated effects of the gas candidates on natural convection and thermal radiation varied depending on their thermal and radiative properties, including absorption coefficient. The TRS showed an excellent insulation performance, with a reduction in the total heat loss of 56-70% under the relatively low temperatures of the IPWR system, except for carbon dioxide (13%). Consequently, TRS can be utilized to enhance the thermal efficiency of SMR designs by suppressing the heat loss through the MCV.