The heat-exchanger (1) has a number of flattened tubes (7), running between top (3) and bottom (8) header tanks. The header tanks and tubes are all made of aluminum. The top header tank is divided into two separate chambers by a wall (6) running longitudinally down its middle. An inlet connection (4) passes fluid to the first chamber and an outlet connection (5) passes fluid from the second chamber. The tubes are pinched along the centerlines of their flat sections so that the fluid can flow down one side of the tubes from the first chamber to the bottom header tank and up the other side to the second chamber.
