Patent ID: 7246437

Claim:
A method of manufacturing a heat exchanger for cooling exhaust gas of an internal-combustion engine, said method comprising the steps of: providing a plurality of tube halves; arranging a plurality of lugs on said tube halves, in pairs, by drawing and pressing together portions of a wall of each of said tube halves to integrally form the lugs from the wall; joining pairs of said tube halves together to form rectangular tubes for guiding exhaust gas with the lugs arranged diagonally to a flow direction of the exhaust gas; providing first and second latticed tube bottoms; welding ends of said rectangular tubes to said latticed tube bottoms such that said rectangular tubes form a bundle; attaching a sheet metal jacket provided with a coolant inlet and a coolant outlet to the tube bottoms, the inlet and outlet adapted to allow a liquid coolant to flow around said rectangular tubes in said sheet metal jacket; and attaching connections to said tube bottoms, to ends of said sheet metal jacket, or to both said tube bottoms and ends of said sheet metal jacket, said connections being configured for attachment to an exhaust pipe communicated with the exhaust gas from the internal-combustion engine, each said connection defining a central opening for communicating said rectangular tubes with the exhaust pipe.