| 摘要 |
PROBLEM TO BE SOLVED: To provide an inner face-grooved heat transfer tube with almost no crushing or tilting of fins during pipe expansion, and superior heat transfer performance in regard to an inner face-grooved heat transfer tube using carbon dioxide as a coolant. SOLUTION: Spiral grooves 4 are formed on an inner face, and fins 2 are formed between the grooves. When an outer diameter D is three to seven millimeters, a height h of the fin 2 is 0.1-0.3 millimeters, the number n of the fins per pipe circumferential length in a tube axis orthogonal cross section is 50 or more, andσ<SB>B</SB>is a tensile strength of the tube, a thickness t of the tube in the groove part 4 satisfies the following mathematical expression. t≥(25.5×D)/[2×(0.8×σ<SB>B</SB>+25.5)] and, a vertical angleαof the fin 2 in the tube axis orthogonal cross section is 15°or more. COPYRIGHT: (C)2008,JPO&INPIT
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