| 摘要 |
A tube is provided with elastically deformable tube deforming sections (tube curved sections), and a fin is provided with the quality of spring so that the fin deforms in accordance to changes of dimension between the tubes. Accordingly, it is possible to weaken (absorb) stress by the tube deforming sections (tube curved sections), and to prevent the fin from separating from the tube even when the tube deforming section (tube curved section) deforms.
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