| 摘要 |
PROBLEM TO BE SOLVED: To improve a function by providing a plurality of horizontal louvers having inner surface side air passage areas smaller than outer surface side air passage areas at the same height as an inside cylinder of an outer cylinder top part. SOLUTION: A chimney 1 is constituted by providing a permeable wall 5 consisting of a plurality of horizontal louvers 4 roughly at the same height as the inner cylinder 2 as well as surrounding an outer periphery of the inner cylinder 2 at a top part of an outer cylinder 3 surrounding a plurality of inside cylinders 2. Thereafter, a vertical cross section shape of the louver 4 is made triangle where side length of an outer surface side 3a of the outer cylinder 3 is smaller than side length of an inner surface side 3b or trapezoidal. When cross wind blows in the neighbourhood of the wall 5 and a flow of moving air enters the outer cylinder 3 through the louvers 4, a passage formed between the adjacent louvers 4 becomes narrow toward the inside of the outer cylinder 3, and accordingly, the air passing the louver 4 is compressed, suddenly expanded inside the outer cylinder 3 and comes to easily flow above the outer cylinder 3 where pressure is low, and air blowing by from the louver 4 in the downstream of the outer cylinder 3 decreases. Consequently, it is possible to restrain occurrence of down wash and to prevent contamination of the outer cylinder.
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