Heat exchanger with a plurality of individual tubular parts and process for the manufacture thereof

A process for manufacturing a heat exchanger comprising a plurality of tube joints between inner and outer tubular shaped elements, wherein said inner and outer tubular shaped elements originally having the same diameter, said process comprising the steps of:

• passing the ends of a set of tubular elements selected from the set of outer tubular shaped elements and the set of inner tubular shaped elements through the orifices of a pressure platen having a number of orifices therethrough corresponding to the number of tube joints;
• expanding the ends of said outer tubular shaped elements, the outer diameter of the expanded ends of said outer elements being larger than the diameter of at least a portion of said orifices of said pressure platen, and the inner diameter of the expanded ends of said outer elements being substantially equal to the outer diameter of the ends of the inner elements, the ends of both the inner and outer tubular shaped elements being cylindrical;
• inserting the cylindrical ends of the inner tubular shaped elements into axially overlapping position within the expanded cylindrical ends of the outer tubular shaped element to produce a pluralty of tube joints lying in a single plane;
• and
• moving said pressure platen onto the overlapping ends of said outer and inner tubular shaped elements with orifice portions having a smaller diameter than the outer diameter of the cylindrical end portions of said outer tubular shaped elements disposed around the overlapping end portions of the inner and outer tubular shaped elements between the free ends of said overlapping cylindrical end Portions to simultaneously reduce the cross section in all of the tube joints, thereby obtaining a plastically deformed Pressure fit between said inner and outer tubular shaped elements, wherein said pressure fit comprises a radially inwardly directed plastic deformation of both the inner and the outer tubular shaped elements between the free ends of the overlapping cylindrical end portions, and the outer diameter of the inner tubular shaped element in the plastically deformed area of the pressure fit is smaller than the outer diameter of the remainder of the inner tubular shaped element.