METHOD FOR DETERMINING REPRODUCIBLY IF VISUAL FEATURES OF OBJECTS ARE KNOWN TO A PERSON

摘要

Heat exchanger tube (4; 4') composed of a metal outer tube (2; 2') having inner profile (8; 8') and a metal inner tube (3; 3') having outer profile (9; 9'), wherein the profiles are in undercut engagement with each other so that the inner and outer tubes are in rigid abutment without play, and at least one longitudinal channel (10, 11; 10', 11') is provided for leak detection, formed between the outer tube and the inner tube. The heat exchanger tube can be manufactured by designing the profiles so that the inner and outer tubes can be screwed or slid one into the other, after which the tubes can be brought into a play-free, rigidly abutting configuration through deformation, for instance by means of a drawing die.