maintained between the tube 31 and the intermediate barrier wall 53 before a brazing process may be 0 2 to 0 3 mm this gap g is filled up by a clad material in the brazing process as a result the coupling force between the intermediate barrier wall 53 and the tube 31 increases so that desired stiffness against the inner pressure of refrigerant may be secured partition plates 70 are installed at opposite ends of the first header 11 to seal the first header 11 another partition plate 70 is also installed at a central region of the first header 11 as a result the first header 11 is partitioned into two tanks 11 a and 11 b a group of tubes 31 which are included in the first heat exchanging unit 30 are connected to each of the first and second tanks 11 a and 11 b thus refrigerant flows in the first header 11 in the form of a plurality of flows separated from one another by a plurality of partition plates 70 similarly partition plates 70 are installed at opposite ends of the second header 12 to seal the second header 12 the second header 12 is partitioned into a single tank 12 a accordingly all tubes 41 of the second heat exchanging unit 40 are connected to the tank 12 a of.