To prevent a brazing area from decreasing due to variation in the clearance of bonding face.
As shown on Fig. 4(b), the bonding face of both tubes 221, 222 is divided into a plurality of sections by making a groove space G which is not bonded to the bonding face. Since the bonding face is divided into a plurality of sections by the groove space G which is not bonded thereto, variation in the clearance of the bonding face is divided among the plurality of sections and decreased even when two flat tubes 221, 222 are bonded over the entire region in the longitudinal direction. Even if molten brazing material is shifted to a part of small clearance and a part of large clearance is not brazed to generate a void, it is confined within a small part of each section and a uniformly brazed state is obtained as a whole, thus ensuring a brazed area.
OKINOYA TAKESHI
YAMAMOTO KEN
KOBAYAKAWA TOMOAKI
KUSAKARI KAZUTOSHI
SAIKAWA MICHIYUKI
TOKYO ELECTRIC POWER CO
CENTRAL RES INST ELECT