| 摘要 |
<p>Provided is a heat exchanger producing method wherein, even when a heat transfer tube with inner surface grooves, which has an inner surface (11) from which a plurality of inner surface protrusions are projected, is used, the heat transfer tube can be expanded so that a tube expanding load is prevented from increasing, fins can be prevented from folding, and a sufficient contact with heat release fins can be obtained. In the heat exchanger producing method, a heat transfer tube (1) having the inner surface (11) on which a fin structure portion (12A) functioning as inner surface protrusions is formed, is expanded by a tube expansion plug (2), so that the heat transfer tube is brought into close contact with heat release fins (3). The tube expansion plug (2) is comprised of a plug expansion portion (2A) and a plug shrinkage portion (2B) subsequent to the plug expansion portion. The outer peripheral surface of the plug expansion portion (2A) has a radius (R1) of curvature along the outer peripheral shape in the axial direction of the tube, said radius (R1) of curvature satisfying 8 mm = R1 = 20 mm. The outer peripheral surface of the plug shrinkage portion (2B) has a radius (R2) of curvature along the outer peripheral shape in the axial direction (D1) of the tube, said radius (R2) of curvature satisfying R2/R1 = 0.8. The heat transfer tube (1) which has been shrunk after being expanded is expanded again by extracting the tube expansion plug (2) from the inside of the heat transfer tube (1).</p> |
