Ventilating Performance of Vertical Exhaust Duct in a Multi-story House : Model Experiment and Computer Simulation for Pressure Distribution through the Exhaust Duct

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  • 集合住宅の共用排気ダクト設計方法に関する研究 : 合流損失に関する模型実験およびダクト内圧力分布に関する数値解析
  • シュウゴウ ジュウタク ノ キョウヨウ ハイキ ダクト セッケイ ホウホウ ニ

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Abstract

Ventilating performance of the vertical exhaust duct installed in multi-story houses was analysed by model experiment and computer simulation. The pressure losses at the flow junctions in the vertical duct were investigated by the model experiment. The pressure distributions along the vertical duct in three different multi-story houses of 5, 15 and 25 stories were calculated by the computer simulation. The results are as follows: 1) The pressure losses at the flow junctions in the vertical duct were expressed by the approximate equations with two ratios of the air velocity and sectional area in the vertcial duct to those values in the branch duct. 2) The pressure loss of the converging flow at the junction through the vertical duct was positive with tee junction, but that with elbow-type junction was negative. This means that the elbow-type junction makes the pressure in the duct increase upward, and the reverse flow from the vertical duct to the apartments possibly occurs in the upper stories. Therefore, the tee junction should be used in order to prevent such reverse flow. 3) It is possible to keep the pressure in the vertical duct at constant by controlling the rotational speed of the exhaust fan mounted at the top of the vertical duct.

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