| 摘要 |
<p>Multiple curved protruding parts (38a), the protruding portions of which continuously curve multiple times, and multiple curved recessed parts (38b), the recessed portions of which continuously curve multiple times, are formed radiating from the center toward the outer perimeter on both of the flat faces of flat tubes (32) such that the period and the amplitude of the curves is greater at the outer circumferential side than at the inner circumferential side. Thus, at the inner circumferential side, the gaps between the multiple curved protruding parts (38a) and the multiple curved recessed parts (38b) are narrow and the resistance to the flow of exhaust air is greater, and at the outer circumferential side, the gaps between the multiple curved protruding parts (38a) and the multiple curved recessed parts (38b) are wider and the resistance to the flow of exhaust air is less, which produces an effect whereby the exhaust air is directed from the inner circumferential side toward the outer circumferential side, making it possible to prevent a short-circuit of the exhaust air at the inner circumferential side of the flat tubes (32).</p> |
