| 摘要 |
PURPOSE:To maintain a heat exchanging capacity by controlling an increase in draft resistance and a reduction in the draft amount at the dewing time by a method wherein the diameters of beat transfer tubes are made smaller as they are nearer the upstream side, and the parts of fins between the tubes are so constituted as to be in flat-shape, wave-shape, and cut and raised shape stepwise from the upstream side of an air flow. CONSTITUTION:At the front edge part of a fin 10 and the circumferences of heat transfer tubes in the upstream side of an air flow, frost layers 16 are formed and as the diameters of heat transfer tubes 11a at the most upstream side of the air flow are smallest, fin efficiency at the front edge part of the fin 10 is lower than that in the case when the tube diameters are larges, and also an overall heat transfer rate at the front edge part does not become so high. Even if the circumferences of the tubes 11a are frosted, a ventilation passage is sufficiently secured. When humid air flows toward the downstream side, that is, when it passes through flat-shaped parts, wave-shaped parts 13, and cut and raised parts 14 which have higher heat transfer rates one after another, frost is formed at respective parts and therefore, uniform frosting condition is formed as a whole. Therefore, clogging, an increase in draft resistance, and a reduction in the draft amount which are caused by frost are controlled and space heating capacity can be maintained for a long time.
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