| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem in a conventional doubler pipe type heat exchanger that, when high-water temperature of about 90°C is obtained, water-side heat transfer rate is deteriorated to remarkably reduce the supplying quantity of high-temperature water. SOLUTION: In this double pipe type heat exchanger comprising an inner pipe and an outer pipe, the outer pipe has a plurality of spiral grooves formed continuously on the inner wall. The grooves are formed so that the ratio of the groove depth Hf to the minimum inside diameter Di of the outer pipe is 0.015 or more, the twisting angle of the grooves to the pipe axis is 25°or more, and the ratio of the number of grooves to the minimum inside diameter Di of the outer pipe is about 1.5-5.0 piece/mm. COPYRIGHT: (C)2005,JPO&NCIPI
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