Abstract: Firstly, a heat transfer tube, in which grooves are formed on its inside surface in groove working step (1) and then its forming is applied in forming step (2), is softened in annealing step (3). Then, the tube is coiled in line in coiling in-line step (4). Here, while supplied in the length direction, the heat transfer tube is heated and cooled in the annealing step (3). Further, in the coiling in-line step (4), the heat transfer tube is coiled in line on a body of bobbin, so that works of installing the heat transfer tube to the bobbin can be simplified.

Abstract: A pipe (40) having a specific length is filled with nitrogen gas (4a). From opening ends of connecting portions (42, 42) located at respective ends of the pipe (40), cross sectionally hat-shaped block plugs (50) made of brazing material are pressed into the connecting portions (42, 42) respectively and are fitted thereto for the purpose of sealing the pipe (40). Next, one end of a connecting piece (60) is inserted into the connecting portion (42) of one pipe (40) so as to break through the block plug (50) fitted thereto. The other end of the connecting piece (60) is also inserted into the connecting portion (42) of another pipe (40) so as to break through the block plug (50) fitted thereto. Thereafter, the block plugs (50) are melt so that the connecting portions (42) of both the pipes (40) are brazed with the connecting piece (60).

Abstract: An expanding mandrel (10) used mainly for expanding heat exchanging tubes (21) of a cross fin coil (20) of an air conditioning machine, so as to connect them to fins of the cross fin coil. The expanding mandrel has flexibilty, comprising a plurality of mandrel pieces (11) which are bandably connected in a row, with an expanding head (13) disposed at the leading end. By an expanding method and an expanding apparatus both using the mandrel (10), the mandrel (10) is wound on the winding drum (41); is fed from the winding drum (41) so as to be inserted into the heat exchanging tube (21) of the cross fin coil so as to be expanded at the time of tube expansion; and is retracted from the heat exchanging tube (21), after completion of the expanding, so as to be wound on the winding drum (41). This provides a decreased size of the apparatus and allows even an expansion of a heat exchanging tube which has been bend-processed.