| 摘要 |
PURPOSE:To prevent the occurrence of closing due to formation of frost at a tip, by a method wherein a distance between a heat transfer pipe in a frontmost row and the tip of a fin is increased over that between a heat transfer pipe in a rearmost row and the rear end of the fin, and a plurality of pores are formed in a plurality of rows in a position in the vicinity of the tip of the fin. CONSTITUTION:Air 8 imparts heat through the surfaces of a fin 5 and a fin collar 6 or the surface of a steel pipe 7 to refrigerant and is cooled. In this case, steam in the air 8 is condensed, and is adhered as water to the surface of a fin 5 or a fin collar 6, and in case, when adhered, a metal surface is cooled down to 0 deg.C or less, the water is momentarily condensed to form frost. However, since the tip of the fin of an air 8 inflow part is expanded in a manner that X is longer than Y and a number of pores 9 are formed in a plurality of rows, the flow of heat from the steel pipe 7 to the tip is impeded, a fin temperature is increased due to lowering of fin efficiency at the tip part of the fin, and an amount of frost formed to the tip part can be decreased.
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