• 제목/요약/키워드: Radiant Energy

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A Study on the Turbulent Natural Convection - Radiative Heat Transfer In a Partitioned Enclosure (차폐막이 있는 밀폐공간 내에서의 난류 자연대류 - 복사열전달에 관한 연구)

  • 박경우;이주형;박희용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.10
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    • pp.2738-2750
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    • 1994
  • The Effects of radiative heat transfer on turbulent flow in a partitioned enclosure is studied numerically. The enclosure is partially divided by a thin, poorly conducting vertical divider projecting from the ceiling of the enclosure. The low Reynolds number $k-{\epsilon}$ model is adopted to calculate the turbulent flow field. The solutions to the radiative transfer equations are obtained by the discrete ordinates method(DOM). This method is based on control volume method and is compatible with the SIMPLER algorithm used to solve the momentum and energy equations. The effects of optical thickness and Planck number on the flow, temperature fields and heat transfer rates are investigated for a moderate Rayleigh number($=10^9$). The changes in buoyant flow fields and temperature distributions due to the variation of baffle length are also analyzed. From the predictions, radiant heat exchange between the baffle and the sidewalls strongly influences the temperature distribution in the baffle and its vicinity and total heat transfer increases as the optical thickness and the baffle length decrease. It is possible to neglect the radiative heat transfer effect when Planck number is over one.

Numerical Analysis of Natural Convection and Surface Radiation in a Square Enclosure (정사각형 밀폐공간내에서의 자연대류와 표면복사의 수치해석)

  • 권용일;권순석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.5
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    • pp.983-991
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    • 1992
  • This investigation is carried out numerically for the two dimensional natural convection and surface radiation heat transfer in a square enclosure. The bottom and top walls are isothermal at hot and cold temperatures respectively whereas the left and right side walls are adiabatic except a transparent window on the right side partially. The exchange of radiant energy is obtained by the net radiation method and the shape factor by the crossed string method. The changes in temperature and Nusselt number distributions of the walls due to the surface radiation and insolation are also investigated.

Study on Integrated Workflow for Designing Sustainable Tall Building - With Parametric method using Rhino Grasshopper and DIVA for Daylight Optimization

  • Kim, Hyeong-ill
    • KIEAE Journal
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    • v.16 no.5
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    • pp.21-28
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    • 2016
  • Purpose: The Objective of this study is to explore the capabilities of an integrated modelling and simulation workflow when applied to an experiment-based research process, aimed at deriving daylight optimization strategies specific to tall buildings. Methods: Two methods were devised to apply this workflow with the help of DIVA and Rhino/Grasshopper. The first method is a multiple variant analysis by setting up an appropriate base case and analysing its daylight and energy performance, forming the basis of comparison for subsequent cases for design variants. The second method involved setting up the base case within a site context and conducting a solar irradiation study. An architectural variables such as overhang and shading device, were then defined as inputs in the parametric definition in Grasshopper to control the selected variable. Results: While the first method took advantage of the speed and efficiency of the integrated workflow, the second method was derived based on the ability to directly process simulation data within the integrated, single-software platform of the proposed workflow. Through these methods, different architectural strategies were explored, both to increase daylight penetration and to reduce radiant heat gain. The focus is on methods by which this workflow can be applied to facilitate the experimental derivation of daylight optimization strategies that are specific to tall building design.

Parameters Estimation in Longwave Radiation Formula (장파복사 모형의 매개변수 추정)

  • Cho, Hongyeon;Lee, Khil-Ha;Lee, Jungmi
    • Journal of Environmental Impact Assessment
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    • v.21 no.2
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    • pp.239-246
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    • 2012
  • Daily net radiation is essential for heat budget analysis for environmental impact assessment in the coastal zone and longwave radiation is an important element of net radiation because there is a significant exchange of radiant energy between the earth's surface and the atmosphere in the form of radiation at longer wavelengths. However, radiation data is not commonly available, and there has been no direct measurement for most areas where coastal environmental impact assessment is usually most needed. Often an empirical equation, e.g., Penman and FAO-24 formulae is used to estimate longwave radiation using temperature, humidity, and sunshine hour data but local calibration may be needed. In this study, local recalibration was performed to have best fit from a widely used longwave equation using the measured longwave radiation data in Korea Global Atmospheric Watch Center (KGAWC). The results shows recalibration can provided better performance AE=0.23($W/m^2$) and RMSE=14.73($W/m^2$). This study will contribute to improve the accuracy of the heat budget analysis in the coastal area.

Study on Characteristics of Radiation Environment in the Urban through the Field Observation in the Summer (하절기 도시의 장.단파 복사특성 관측)

  • Jung, Im-Soo;Choi, Dong-Ho;Lee, Bu-Yong
    • 한국태양에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.105-110
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    • 2011
  • The objective of this study is to analyze the characteristic of radiation environment in the urban and rural through the field observation in the summer. The radiation balance was compared through the measurement of the shortwave radiation and long-wave radiation in the urban, sub-urban, and rural. The following conclusion could be obtained from this research. (1) In the results of observation including the rain-day, it was found that the short wave radiance in the urban is lower about 10% than the rural. (2) The upper part of atmosphere layers in the urban area absorb much short wave radiation energies compared with the rural relatively. It can increase the temperature of the upper part of atmosphere layers and the emittance of long wave radiation. (3) The ratio of the downward short wave radiation to the downward long wave radiation was 1.24 for the urban, 1.28 for sub-urban and1.35 for rural. It can be estimated that the atmosphere condition of the rural is better than that of other areas.

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Luminance Assessment of Outdoor Lighting for Advertisements at Night (옥외광고용 발광조명의 야간휘도분포 분석)

  • Shin, Hwa Young;Lee, Jong Soo;Kim, Jeong Tai
    • KIEAE Journal
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    • v.9 no.6
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    • pp.65-72
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    • 2009
  • Lighting for outdoor advertising is very common feature of building facades as they provide the information and commercial identification. As the interest of improving street beautification more widely, application of various lighting technologies has been develop for advertisement such as electric sign board and signage. Furthermore, the installation of higher sign luminance than needed has many negative consequences, including higher energy consumption and light pollution. There are now no standard for outdoor advertisements in terms of luminance, and installation of indiscreet outdoor advertisement without luminance consideration is becoming more commonplace. This study was to evaluate the luminous characteristics of outdoor advertising as a function of sign and building facade luminance, luminance ratio. Data were collected on 8 electric sign boards, 20 internally illuminated, externally illuminated, neon, and channel letter signs and 4 commercial areas. Photometric measurements were taken by CS-100(Minolta) and ProMetric-1400(Radiant Imaging) for various sign modes and sign design. Also luminance of building facades were analyzed according with CIE standard of maximum obtrusive light permitted for exterior lighting installations. The findings are as follows; (1) There were excessive luminance of electric sign boards that could affect adjacent building facade and night sky luminance. (2) Sings that are externally illuminated providing an inappropriate amount of light on to the outer surface of the sign caused higher building facade luminance and potential of unnecessary glare.

Acceptable Supply Air Conditions of Dedicated Outdoor Air System for a High-rise Apartment Building (초고층 공동주택 외기전담 시스템 기반 중앙 공급식 환기시스템의 적정 급기조건 설정)

  • Kim, Min-Hwi;Kim, Jin-Hyo;Kwon, Oh-Hyun;Jeong, Jae-Weon
    • 한국태양에너지학회:학술대회논문집
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    • 2009.11a
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    • pp.285-290
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    • 2009
  • The main thrust of this paper is to investigate acceptable supply air conditions of a dedicated outdoor air system (DOAS) for highrise apartment buildings. As for a typical $132-m^2$ apartment unit, it was assumed that centralized DOAS-Ceiling Radiant Cooling Panel was installed. Transient behavior and control characteristics of each system were modeled numerically using a commercial equation solver program. The optimized dew point temperature of the DOAS was discussed on the basis of the ASHRAE standard 62.1-2007 and the current Korean ventilation standard for apartments. It was found that the optimized dew point temperature of the DOAS supply air accommodating total latent load of a space is $11-12^{\circ}C$ and the appropriate supply air temperature of the DOAS is $11-12^{\circ}C$ in cooling period and neutral temperature of $18-20^{\circ}C$ in intermediate period.

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An Investigation of Radiation Heat Transfer on The Horizontal Fin of An External Fuel Tank by Flame of a Flying Flare (날아가는 섬광탄이 연료탱크 수평핀에 미치는 복사열전달 연구)

  • Jung, Daehan;Kang, Chihang;Kim, Sitae
    • Journal of the Korea Institute of Military Science and Technology
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    • v.17 no.2
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    • pp.197-203
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    • 2014
  • In this paper, the effect of unsteady radiation on the horizontal fin of an external fuel tank by flame of a flying flare was analysed to see the temperature increase of the fin and the thermal impact on the fin. Radiation between two surfaces was calculated using the concept of radiation resistance of surface and space including radiation, irradiation and shape factor for two flying trajectories of a flare, maximum temperature of 2200 K, emissivity of 0.95, flying velocity of 30 m/s, and thermal surface area of $0.01m^2$. The result shows that the temperature increase of the fin is 0.236 K, and the thermal effect on the fin is ignorable. And it was found that temperature is increased a little because small amount of heat energy can be radiated due to the short exposure time to the heat source.

Study on Improvement of Heat Dissipation Characteristics of TIM Material Using Radiant Energy (복사에너지를 이용한 TIM소재의 방열 특성 향상을 위한 연구)

  • Hwang, Myungwon;Kim, Dohyung;Jung, Uoo-Chang;Chung, Wonsub
    • 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.

A Study on the Impact of Media Façade Performances on the 10-story Gyeongcheonsa Pagoda (미디어파사드 상영 시 경천사지 십층석탑에 미치는 영향 조사 연구)

  • Lee, Hong Shik;Ryu, Jae Hyoung;Lee, Kwon Joon;Yang, Seok Jin
    • Conservation Science in Museum
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    • v.28
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    • pp.51-64
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    • 2022
  • This study aims to identify the impact of optical energy on cultural properties when the light energy irradiates cultural assets during augmented reality (AR) or media façade performances as activities designed to garner public interest. The 10-story Gyeongcheonsa Pagoda was used for this study, and the impact was evaluated by comparing the optical energy irradiated during a media façade performance with the energy irradiated under normal conditions. For comparison, this study measured the illuminance in lux for each light source that irradiated the ten-story stone pagoda and used the data to calculate illuminance in lux-hours. The results showed that the pagoda receives 786.4 lux per hour when both sunlight and artificial light are present, while 13.2 lux of energy is irradicated by the media façade for each performance. The result indicates that the pagoda receives about 29.8 times more optical energy from sunlight and artificial light sources than during media façade performances on an hourly basis, when the performance is carried out twice a week. This study therefore concludes that the optical energy of media façade performances inflicted trivial damage to the ten-story stone pagoda.