Double-tube heat exchanger and manufacturing method thereof

A double-tube heat exchanger (1) comprising an outer tube (2) and an inner tube (3) concentrically arranged so as to form a first annular gap (14) in between said outer tube (2) and said inner tube (3), wherein said outer tube (2) is provided with at least an inlet connection (4) and with at least an outlet connection (5) for inletting and outletting, respectively, a first fluid (F1) flowing in said first annular gap (14), wherein said inner tube (3) is provided with at least an inlet connection (6) and with at least an outlet connection (7) for inletting and outletting, respectively, a second fluid (F2) flowing in said inner tube (3) for an indirect heat exchange with the first fluid (F1), wherein said inlet (6) and outlet (7) connections of the inner tube (3) are jointed to equipment or conduits placed upstream (100) and/or downstream (200) of the heat exchanger (1), and wherein at least an assembly wall (35) joints a first end (8) of said outer tube (2) to said inner tube (3) so as to seal said first annular gap (14) at the first end (8) of said outer tube (2), said heat exchanger (1) being characterized in that said inner tube (3) is formed by at least two tube sections (24, 25, 36), jointed each other by means of a joint of butt-to-butt type, wherein at least one (25, 36) of said tube sections is integrally formed, as a single monolithic piece, with said assembly wall (35), wherein a second annular gap (19) is formed in between said assembly wall (35) and said inner tube (3), or formed between said assembly wall (35) and said equipment, or formed between said assembly wall (35) and said inner tube (3) and said equipment, wherein said second annular gap (19) is exposed to the air and is in fluid communication neither with said first annular gap (14) nor with said inner tube (3), and wherein said second annular gap (19) is at least partially surrounded by said first annular gap (14);

• wherein one or more heat transfer elements (39) or heat transfer filling materials (40) are inserted into said second annular gap (19), wherein said heat transfer elements (39) or said heat transfer filling materials (40) are configured for enhancing the heat transfer by passing heat through the heat transfer elements or heat transfer filling materials and between said assembly wall (35) and said inner tube (3), or between said assembly wall (35) and said equipment, or between said assembly wall (35) and said inner tube (3) and said equipment.