Abstract: The heat exchanger (1) contains a jacket element (2) and an insert element (3), wherein the insert element (3) is arranged in the operating state in the interior of the jacket element (2). The insert element has a longitudinal axis (4). The insert element (3) contains an insert jacket element (31) and a plurality of web elements (9, 10), the web elements (9, 10) having a first end (13) and a second end (14). The first end (13) and the second end (14) of each web element (9, 10) are connected to the insert jacket element (31) at different locations. At least a portion of the web elements (9, 10) includes web element channels (11, 12), the web element channels (11, 12) extending from the first end (13) of the web element (11) to the second end (14) of the web element (11). An intermediate jacket element (5) is arranged between the insert jacket element (31) and the jacket element (2).