A Laboratory Experiment on Natural Ventilation of a Roof Cavity

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  • 屋根内中空層の自然換気に関する実験室実験結果

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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.


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