Abstract: The heat exchanger according to the invention comprises extremely flat oval-shaped tubes (3) extending in a mutually parallel and spaced-apart relationship and are connected on their narrow side to manifold pipes (1,2) for forward and return flow. To ensure a sufficiently stable mechanical connection between the pipes and a satisfactory supply and discharge of the heating medium from the manifolds to the flat tubes as well as in the reverse direction, a trough (5) is formed by material removal in the manifold pipes (1a, 2a) thus creating a connection aperture (6) in the wall of the pipe. The flat tube (3a) is fitted into this trough (5) with its rim on the narrow side, to ensure a solid stable welded joint between the pipes. The flat tube (3a) is provided on its narrow side with a bore serving as a connection aperture (7), which comes to lie centrally against the connection aperture (6) in the manifold (1a, 2a).

Abstract: In a radiator having flat tubes arranged in parallel and connected to header pipes for feed and return flow, each flat tube has two connection bores near the front end thereof. To enable the radiator to be manufactured by the use of pressure welding, a support part, angled into U-form with two bent ends arranged coaxially with the two connection bores, is inserted into each flat tube. These ends of the support part prevent the flat tube from being pressed inwardly during pressure welding. The portion of the support part extending parallel with the end edge of the flat tube is welded to the tube end edge, so that the support part simultaneously also forms the end closure wall of the flat tube.