| 摘要 |
In the method of manufacturing a heat exchanger, transverse sectional shapes of heat exchanging tubes can be easily formed into elliptical shapes. The method includes the steps of: piling metallic fins, each of which includes collared through-holes, so as to form tube holes, which are formed by connecting the collared through-holes; piercing heat exchanging tubes, whose transverse sectional shapes are circular shapes, through the tube holes; and inserting expanding bullets, whose transverse sectional shapes are elliptical shapes, into the heat exchanging tubes. The heat exchanging tubes are elliptically expanded to and integrated with the metallic fins.
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