花弁状内管を有する三重管式熱交換器の流動，伝熱特性

抄録

The authors examined the heat transfer performance of double tube type heat exchanger (pipe outer diameter: 22.0 mm, pipe length: 2.4m) with petal shaped special inner tube having a large wet perimeter. The 6 petal shaped inner tube, 6P-tube, 5P-tube, 5P’-tube with a shallow petal and conventional double tube (CP-tube) were used, and it was made clear that 5P-tube has an excellent heat transfer performance. However, as the flow resistance was increased in proportion to the heat transfer, it did not reach significant improvement of heat transfer efficiency.

In this study, to improve and enhance the heat transfer performance of 5P-tube more a decrease of a large pressure loss of the outer tube will be examined using a triple tube, 5P-tri-tube, and will be shown an excellent heat transfer performance of it. At this time, the hot water of 60 flowed in the inner tube and cold water of 20 flowed in middle and outer tubes as countercurrent flow. Further, to investigate the influence of the flow path position of hot water, the hot water of 60 flowed in the middle tube. As a result, it was shown that for example, at a Reynolds number of Re_e = 6,000 the heat transfer efficiency η_db is improved from 3.7 times to 6.3 times of the CP-tube.