• Title/Summary/Keyword: Equivalent U-value

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A study on the annual energy performance of apartment building with the equivalent U-value of envelope considering the effect of thermal bridges (공동주택 외피의 열교영향을 고려한 상당열관류율 및 연간 에너지소비성능 평가 연구)

  • Kim, Dong Su;Yoon, Jong Ho;Shin, U Cheul;Kwak, Hee Yul
    • KIEAE Journal
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    • v.12 no.3
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    • pp.41-46
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    • 2012
  • The building envelope is important specially for saving energy consumption of residential buildings. but Apartment houses in Korea commonly have inside insulation system which have constantly arisen thermal bridges, the risk of heat loss, as a necessity. This study aims to evaluate integrated insulation performance according to the different shapes of external walls, adjacent to windows. The thermal performance analysis was carried out by Equivalent U-value and using the three-dimensional heat transfer computer simulation (TRISCO-RADCON), under nine different cases of comparing among three each of different bases(current standard model, 30percent energy saving model and 60percent energy saving model). The heating and the cooling load were also compared between two cases (standard U-value and Equivalent U-value) of three each of different bases, using the Building energy simulation which is based on DOE-2.1 analysis. As results, it turns out that if the Equivalent U-value is considered on the envelope analysis, the heat flow loss will be increasing more than the standard U-value, and if heat insulation property of the residential building reinforced rather than current, the rate of influences on the thermal bridges would be extremely expanded. In addition, it is shown that annual heating loads of the apartment house with applied Equivalent U-value substantially increased by more than 15 percent compared to those with the existing U-value, but annual cooling loads were negligibly affected.

Energy Performance Evaluation Study on the Thermal Bridge Blocking External Insulation System for Green Remodeling (그린 리모델링용 열교 차단 외단열 시스템의 에너지 성능 평가 연구)

  • Kim, Woong-Hoi;Kang, Eun-Ho;Yoon, Jong-Ho
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.234-235
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    • 2021
  • We set the representative balcony types of the existed building to two types: unexpanded balcony and extended balcony, and analyze the effect of reducing the cooling and heating energy load when applying remodeling. The scope of the study was limited to balcony walls, including window-wall junctions, and was conducted by comparing cases with and without thermal break insulation structures for a clear conclusion. The study was conducted using the equivalent U-value in each case. The equivalent U-value was calculated by deriving through 2 dimensional steady-state heat transfer analysis of each case balcony envelope. And building energy was calculated using the derived equivalent U-value. According to the calculation results, for unexpanded balconies, the equivalent U-value was reduced by about 80%, and the heating and cooling load was reduced by about 20%. In the case of extended balconies, the equivalent U-value was reduced by about 57% and the resulting heating and cooling load was reduced by about 12%.

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ON SOLVABILITY OF THE DISSIPATIVE KIRCHHOFF EQUATION WITH NONLINEAR BOUNDARY DAMPING

  • Zhang, Zai-Yun;Huang, Jian-Hua
    • Bulletin of the Korean Mathematical Society
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    • v.51 no.1
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    • pp.189-206
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    • 2014
  • In this paper, we prove the global existence and uniqueness of the dissipative Kirchhoff equation $$u_{tt}-M({\parallel}{\nabla}u{\parallel}^2){\triangle}u+{\alpha}u_t+f(u)=0\;in\;{\Omega}{\times}[0,{\infty}),\\u(x,t)=0\;on\;{\Gamma}_1{\times}[0,{\infty}),\\{\frac{{\partial}u}{\partial{\nu}}}+g(u_t)=0\;on\;{\Gamma}_0{\times}[0,{\infty}),\\u(x,0)=u_0,u_t(x,0)=u_1\;in\;{\Omega}$$ with nonlinear boundary damping by Galerkin approximation benefited from the ideas of Zhang et al. [33]. Furthermore,we overcome some difficulties due to the presence of nonlinear terms $M({\parallel}{\nabla}u{\parallel}^2)$ and $g(u_t)$ by introducing a new variables and we can transform the boundary value problem into an equivalent one with zero initial data by argument of compacity and monotonicity.

Heat Transfer of Condensation by the Injecting Steam Flow In Tube (관내연기 분무류의 응축열전달)

  • 김시영
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.20 no.2
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    • pp.137-142
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    • 1984
  • An experimental study has been performed on the heat transfer characteristics of condensation by the injecting steam flow in the tube. The comparison between results of experimental data and available data concerning equivalent Reynolds number has studied. As the result, the followings were obtained. 1. The shear stress of the radial direction in the tube when the injecting steam flow was condensed can be written as root($\tau$sub(0)/$\tau$sub(0v))=1+1.46X sub(tt) super(0.20). 2. The effect of the heat transfer in the injecting steam flow was less than the value of equivalent Reynolds number. The reason are the nonuniform fluid film of the axial and radial direction in the tube. 3. The value of N sub(u) by the heat transfer of condensation can be written as N sub(u)=1.08$\times$[{$\rho$ sub(l) d/$\mu$ sub(l)}/{$\delta$+(2.5/P sub(rl)) ln(y sub(i)/$\delta$)}]$\times${$\tau$ sub(0)/ $\rho$ sub(l)} super(1/2).

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A Study on the Operational Characteristics of a U-shape Heat Pipe (U형 히트파이프의 작동 특성에 관한 연구)

  • Gang, Hwan-Guk;Kim, Cheol-Ju;Lee, Yong-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.12
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    • pp.1711-1720
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    • 2001
  • In this study, the heat transfer characteristics of a U-shape heat pipes were investigated. Heat is supplied to the U heat pipe through its middle zone(evaporator), and is released to the environment through its both arms(condensers). Both heat transfer coefficients and heat transport limitations were measured and compared with correlations previously developed for straight type heat pipes. Special concerns were focused to the cases, when each of condensers were submitted to a different cooling conditions, relatively. As a result. the heat transfer limitation of a U-shape heat pipe was found out to be 10∼15% less than the value for a straight heat pipe with an equivalent size.

LET Calibration of Fe 500 MeV/u Ions using SSNTD (고체비적검출기를 이용한 500 MeV/u 철 이온의 선에너지전이 교정)

  • KIM, Sunghwan
    • Journal of Sensor Science and Technology
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    • v.25 no.1
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    • pp.41-45
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    • 2016
  • In this study, LET (Linear Energy Transfer) calibration of CR-39 SSNTD (Solid State Nuclear Track Detector) was performed using 500 MeV/u Fe heavy ions in HIMAC (Heavy Ion Medical Accelerator) for high LET radiation dosimetry. The irradiated CR-39 SSNDT were etched according JAXA (Japan Aerospace Exploration Agency) etching conditions. And the etched SSNTD were analyzed by using Image J. Determined dose-mean lineal energy ($\overline{y_D}$) of 500 MeV/u Fe is about 283.3 keV/um by using the CR-39 SSNTD. This value is very similar result compare to the results calculated by GEANT4 Monte Carlo simulation and measured with TEPC active radiation detector. We confirmed that the CR-39 SSNTD was useful for high LET radiation dosimetry such as heavy iron ions.

Analysis of radioactivity levels and hazard assessment of black sand samples from Rashid area, Egypt

  • Abdel-Rahman, Mohamed A.E.;El-Mongy, Sayed A.
    • Nuclear Engineering and Technology
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    • v.49 no.8
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    • pp.1752-1757
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    • 2017
  • The aim of this study is to evaluate the radioactivity levels and radiological impacts of representative black sand samples collected from different locations in the Rashid area, Egypt. These samples were prepared and then analyzed using the high-resolution gamma ray spectroscopy technique with a high-purity germanium detector. The activity concentration ($A_c$), minimum detectable activity, absorbed gamma dose rate, external hazard index ($H_{ex}$), annual effective dose rate equivalent, radium equivalent, as well as external and internal hazard index ($H_{ex}$ and $H_{in}$, respectively) were estimated based on the measured radionuclide concentration of the $^{238}U$($^{226}Ra$) and $^{232}Th$ decay chains and $^{40}K$. The activity concentrations of the $^{238}U$, $^{232}Th$ decay series and $^{40}K$ of these samples varied from $45.11{\pm}3.1Bq/kg$ to $252.38{\pm}34.3Bq/kg$, from $64.65{\pm}6.1Bq/kg$ to $579.84{\pm}53.1Bq/kg$, and from $403.36{\pm}20.8Bq/kg$ to $527.47{\pm}23.1Bq/kg$, respectively. The activity concentration of $^{232}Th$ in Sample 1 has the highest value compared to the other samples; this value is also higher than the worldwide mean range as reported by UNSCEAR 2000. The total absorbed gamma dose rate and the annual effective dose for these samples were found to vary from 81.19 nGy/h to 497.81 nGy/h and from $99.86{\mu}Sv/y$ to $612.31{\mu}Sv/y$, which are higher than the world average values of 59 nGy/h and $70{\mu}Sv/y$, respectively. The $H_{ex}$ values were also calculated to be 3.02, 0.47, 0.63, 0.87, 0.87, 0.51 and 0.91. It was found that the calculated value of $H_{ex}$ for Sample 1 is significantly higher than the international acceptable limit of <1. The results are tabulated, depicted, and discussed within national and international frameworks, levels, and approaches.

A Study on the Thermal Performance Analysis of Curtain Wall Office Building Considering the Thermal Bridges (열교부위를 고려한 커튼월 사무소 건물의 열성능 해석에 관한 연구)

  • Shin, U-Cheul;Kim, Seung-Chul;Yoon, Jong-Ho
    • Journal of the Korean Solar Energy Society
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    • v.31 no.3
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    • pp.95-100
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    • 2011
  • Currently, office buildings in Korea tend to adopt as their outer wall the curtain wall structure which can be easily constructed and has beautiful external appearance as well. However, the problem is that the curtain wall structure does not have a uniform composition unlike the wall of existing reinforced concrete structures and has a frame made of metal with high heat conduction. Therefore, it is expected that the structure will be highly influenced by the thermal bridge. Thereupon, this study analyzes how to set up the composition of the wall system and heat transmission rate in consideration of the thermal characteristics of the curtain wall structure and applies it in practice by simulation in order to propose a guideline for the energy simulation method of the curtain wall structure and analyze its differences from existing simulation methods.

A Study on the Environmental Radiation of Concrete Apartments and Neighborhood Living Facilities (콘크리트 공동주택과 근린생활 시설의 환경방사선에 관한 연구)

  • Ji, Tae-Jeong;Kwak, Byung-Joon;Min, Byung-In
    • Journal of the Korean Society of Safety
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    • v.24 no.2
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    • pp.100-104
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    • 2009
  • In this study, the space gamma dose rates in the apartments structured with concrete were measured in accordance with construction year. In addition, the environmental radiation rates coming from the subway platforms and the road tunnels were analyzed in the equivalent dose by multiplying the absorbed dose with the radiation weighting factors. The space gamma dose rates measured in apartments were higher than those of outdoor which was $0.08{\sim}0.11uSv/h$ in the natural conditions. Especially, the older construction year is, the higher becomes space gamma dose rate. The average gamma dose rates in the subway platforms were measured. In the case of Busan and Daegu subway, the earlier the opening year is, the higher becomes dose rate. However, the dose rates of Seoul subway Lines were high overall, regardless of opening year. Seoul subway Line 6 showed the highest value of 0.21uSv/h. The gamma dose rate in road tunnels was higher than one of the outdoor and increased with opening year like as apartment. In dose rate comparison of the concrete structures with the outdoor, therefore, the space gamma dose rate of indoor is higher than one of the outdoor and the older structures have a higher dose rate.

Measurement of Linear Energy Spectra for 135 MeV/u Carbon Beams in HIMAC Using Prototype TEPC (프로토 타입 조직등가비례계수기의 중입자가속기연구소의 135 MeV/u 탄소 이온에 대한 선형에너지 스펙트럼 측정)

  • Nam, Uk-Won;Lee, Jaejin;Pyo, Jeonghyun;Park, Won-Kee;Moon, Bong-Kon;Lim, Chang Hwy;Moon, Myung Kook;Kitamure, Hisashi;Kobayashi, Shingo;Kim, Sunghwan
    • Journal of Sensor Science and Technology
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    • v.23 no.3
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    • pp.197-201
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    • 2014
  • TEPC (Tissue Equivalent Proportional Counter) was usually used for high LET radiation dosimetry. We developed a prototype TEPC for micro-dosimetry in the range of $0.2{\sim}300 keV/{\mu}m$. And, the simulated site diameter of the TEPC is $2{\mu}m$, of similar size to a cell nucleus. For purposes of characterization the response for high LET radiation of the TEPC has been investigated under 135MeV/u Carbon ions in HIMAC (Heavy Ion Medical Accelerator). We determined the gas multiplication factor and measured the lineal energy spectrum [yd(y)] of 135 MeV/u Carbon ions. The value of the gas multiplication factor was 315 at 700 V bias voltage. As a result of the experiment, we could more understand the performance of the TEPC for high LET (Linear Energy Transfer) radiation. And the procedure of high LET radiation dosimetry using TEPC is established.