TWISTING TUBE WITH INNER SURFACE SPIRAL GROOVE AND HEAT EXCHANGER

摘要

PROBLEM TO BE SOLVED: To provide a twisting tube with an inner surface spiral groove and a method for manufacturing the same.SOLUTION: A twisting tube made of an aluminum alloy with an inner surface spiral groove, in which plural spiral grooves extending in a lengthwise direction are formed on an inner surface thereof at intervals in a circumferential direction, and a spiral fin is formed between the spiral grooves, has an outer diameter of 3 to 10 mm. A bottom wall thickness of the twisting tube with the inner surface spiral groove in the plural spiral grooves is not less than 0.55 mm and not more than 0.9 mm, a height of the spiral fin from the spiral groove is not less than 0.24 mm and not more than 0.8 mm, a fin top angle, which is represented by a relative angle of two side wall surfaces in a sectional view of the spiral fin, is not less than 5° and not more than 25°, a fin inclination angle is 1° or less, and an average crystal grain size in a crystal structure is 80 μm or less. On an external surface of the twisting tube with the inner surface spiral groove, there is not an orange peel which is defined as a step of which a surface roughness (Rmax) exceeds 15 μm.SELECTED DRAWING: Figure 3