抄録
Experiments to measure the heat transfer characteristics of eight spiral pipes, in which the P(pitch)/d(diameter) ratio was changed from 1.0 to 4.0, have been performed. The air flow around pipes was observed to be divided into three flow-types, i.e., passing, circumferential and mixed, depending on the P/d ratio. The maximum heat transfer was obatined for the pipes of P/d=3.0∼3.5, and was estimated to be comparable to the heat transfer for straight pipe. An equation correlating Nud with P/d and Red was proposed for the pipes of P/d≤4.0.
