| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat transfer tube with inner helical grooves for improving the tube inside heat transfer ratio, while keeping sufficient pressure-proof strength, in the heat transfer tube with inner helical grooves for constituting a cross fin tube type heat exchanger of a refrigerating air-conditioning hot water supply apparatus using a high pressure refrigerant represented by carbon dioxide. SOLUTION: In a copper or copper alloy heat transfer tube 10, an inner surface fin 14 of the predetermined height is formed between inner surface grooves 12 and 12. When a tube outer diameter is set to D [mm], the bottom thickness forming the tube wall thickness in a forming part of the groove is set to t [mm], the groove depth of the groove is set to d [mm], and the cross-sectional area per one groove in a cross section vertical to the tube axis is set to A[mm<SP>2</SP>], t/D is set to 0.041 to 0.146, and d<SP>2</SP>/A is set to 0.75 to 1.5. When N is set to the number of the grooves, and Di is set to a maximum inner diameter corresponding to a tube inner diameter formed by connecting the groove bottom of the groove, N/Di is set to 8 to 24. COPYRIGHT: (C)2006,JPO&NCIPI
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