Effect of Gas Radiation on Radiative Heat Transfer between Pavement and Human Scale Object

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  • ふく射性ガスの吸収および放射を考慮した路面から人体スケール物体へのふく射伝熱解析
  • フクシャセイ ガス ノ キュウシュウ オヨビ ホウシャ オ コウリョ シタ ロメン カラ ジンタイ スケール ブッタイ エ ノ フクシャ デンネツ カイセキ

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Abstract

This paper describes the three-dimensional numerical simulation of radiative heat transfer from pavement and gases which exist in urban street canyon space to human scale object with consideration of absorption and emission process of the participating non-gray gas mixtures consist of H_2O and CO_2. The ambient temperature and the participating gas concentration were assumed to be of the present summer condition (Case A: ambient temperature 35℃, relative humidity 66%, CO_2 concentration 400ppm) and the projected extreme condition ca 2100 (Case B: 40C, 66%, 800ppm). Effects of solar radiation were not considered in the simulation. The results demonstrated that the gas radiation significantly affects the infrared radiation flux to human scale object from the pavement and from the participating gas mixtures especially in case that horizontal and vertical scale is lager than 20m. Radiation flux with participating gas mixtures is approximately 120〜160W/m^2 higher than that without participating gas. A half of total radiation flux into human scale object model comes from the participating gas mixtures. Participating gas mixtures absorb approximately 30% of total incident radiation flux from the pavement to human object scale model. These results indicate that non-gray gas mixtures could play an important role in the human thermal comfort in urban outdoor environment in hot and humid summer condition. The simulation result under the projected 2100 condition (Case B) is almost same as the result under the present condition (Case A). This means that CO_2 concentration does not affect to radiation transfer to human scale body at least within the scale treated in this study. Furthermore, it is shown that the bottom part of human scale object model tends to receive the radiation from the pavement, whereas the top part of the model mainly receives the radiation from the participating gas mixtures.

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