屋根内中空層の自然換気に関する実験室実験結果 A Laboratory Experiment on Natural Ventilation of a Roof Cavity

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Abstract

本研究は,屋根内中空層の自然換気が屋根を通して伝達される日射熱を軽減する効果を調べるために,屋根モデルを用いた実験室実験の結果をまとめたものである。実験は,日射時に屋根内中空層へ伝達される熱を中空層上面から発生するものとした。中空層の流入および流出口は、屋根中空層に存在する障害物を模擬するため、78,35,20,10mmとスリット状に狭め、その障害の位置の組み合わせによって3群に分けた。傾斜角20°および30°の2種と単位面積当たり発生熱量50,75,100,150W/m^2の4段階について測定を行い,中空層上下面温度と、中空層内気流速および温度分布を測定し、気流による熱輸送量を推定した。その結果,熱排除能力が開口寸法に強く影響されることを示した。実験中の平均流速の最高値は0.25m/sに達した。この値は換気量に換算して7.7L/sとなり、毎分3.0回の換気回数に相当する。また,実験中の最大レイノルズ数は約2009であった。

A laboratory experiment was carried out on the natural ventilation characteristics of a roof cavity focusing on the lessening of solar heat transfer through the roof. Experimental outcomes resulted from measurements in a cavity model heated at the top side in order to mimic a solar radiation incident on the roof. Inlet and outlet openings were narrowed to simulate obstacles along the cavity and were then grouped into three cases based on the obstacle placement. Two inclination angles at 20 and 30 degrees were examined. The cavity surface temperatures, velocity and temperature profiles in the airflow were measured and heat transported by the airflow was examined. The results showed that the heat-dissipation performance of natural ventilation was greatly influenced by the opening size. It was found that average velocity reached to 0.25m/s in the experiment. The corresponding maximum flow rate was 7.7L/s with a turn of over of 3.0 times per minute. The highest found Reynolds number was 2009.

Journal

  • Transactions of the Society of Heating,Air-conditioning and Sanitary Engineers of Japan

    Transactions of the Society of Heating,Air-conditioning and Sanitary Engineers of Japan 33(135), 27-35, 2008

    The Society of Heating, Air-Conditioning & Sanitary Engineers of Japan

References:  11

Codes

  • NII Article ID (NAID)
    110007996733
  • NII NACSIS-CAT ID (NCID)
    AN00065706
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    0385-275X
  • Data Source
    CJP  NII-ELS  IR  J-STAGE 
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