Relation between Density of Buildings and Absorptivity of the Earth for Solar Radiation in Urban Regions : Part 5-An Approximated Estimation Method for Apparent Solar Absorptivity of Urban Canyons with Arbitral Absorptivity Profiles

DOI Web Site 2 Citations
  • NAITO Kazuo
    Department of Environmental Engineering, Faculty of Engineering, Osaka University
  • MIZUNO Minoru
    Department of Environmental Engineering, Faculty of Engineering, Osaka University
  • UCHIYAMA Kazuchika
    Postgraduate Course, Osaka University

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Other Title
  • 都市域における建物密度と日射吸収率の関係 : 第5報-壁面に吸収率分布をもつ凹凸の吸収特性の推定方法
  • 都市域における建物密度と日射吸収率の関係-5-壁面に吸収率分布をもつ凹凸の吸収特性の推定方法
  • トシイキ ニ オケル タテモノ ミツド ト ニッシャ キュウシュウリツ ノ カ

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The urban canyons composed by the buildings have different absorption properties for radiation from those of the plane surface because of mutual reflection of the radiation among the buildings and the ground surface. Changing the heat budget of solar irradiation at the earth surface, this special feature of absorption properties is one of the major factors for the formation of the urban climate. The absorption properties for the solar irradiation of the urban canyons, which have no absorptivity profiles on the walls, was reported by the authors in the previous papers. In this paper, the absorptivities of the urban canyons composed by the uniform parallelepipeds, which have arbitral absorption profiles on the walls, arranged regularly on the horizontal plane was calculated and several approximated methods to estimate the absorptivities were considered. As the results, an approximated calculation method was proposed. This method requires the precise calculation of the direct solar irradiation profiles on the wall surfaces, but the additional absorption resulted from mutual reflection can be estimated from the absorption properties of the urban canyons composed by the uniform walls having no absorptivity profiles, which can be estimated by the charts presented in the previous papers reported by the authors. It is expected that the approximated method gives a fairly good estimation for the absorptivities of more complex configurations of the urban canyons walls have arbitral absorptivity profiles, bacause it is based on the basic principles of heat transfer and uses no empirical correction factors.

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