Patent ID: 8590604

Claim:
A double-wall-tube heat exchanger comprising an outer tube, and an inner tube disposed in and spaced apart from the outer tube such that a clearance between the outer tube and the inner tube and the interior of the inner tube serve as respective refrigerant flow paths, wherein at least one end portion of the inner tube projects from the outer tube, and the outer tube includes an expanded portion which is formed near an end portion of the outer tube from which the inner tube projects, and a contracted portion which is formed on the outer side of the expanded portion with respect to a longitudinal direction, is smaller in diameter than the expanded portion, and is brazed to the inner tube, wherein the outer tube includes a plurality of ridges integrally provided on an inner circumferential surface thereof at predetermined intervals in a circumferential direction such that the ridges project radially inward and extend along the longitudinal direction; portions of the ridges which portions are present on inner circumferential surfaces of the expanded portion and the contracted portion of the outer tube are crushed; and clearances between an outer circumferential surface of the inner tube and inner circumferential surfaces of portions of the contracted portion of the outer tube where the ridges are not formed are filled with a brazing filler metal.