Abstract: A single inlet/outlet-tank U-shaped tube heat exchanger is disclosed comprising a tank having a header plate and a plurality of U-shaped tubes whose legs extend through and terminate with an open end at one side of the header plate. A first group of the tubes is arranged so that the two open ends of each of these tubes are located in one and the other of two outboard rows extending longitudinally of the header plate. A second and remaining group of the tubes is arranged so that the return bends of these tubes criss-cross those of alternate tubes in the first group and have their open leg ends all located in a third and inboard row extending between the two outboard rows.