Abstract: The heat exchanger consists of at least partially connected fins, which run obliquely with respect to one another, and are disposed in a hollow-cylindrical fashion. The sides connecting the fins at their ends form the surfaces of the hollow cylinder. The heat exchanger is disposed between the extruder barrel and the band-shaped, flexible heating element of the heating and cooling configuration. Good heat exchange results, i.e. a quick heating up and cooling down of the extruder barrel and a homogeneous temperature distribution on the extruder barrel. The heat exchangers can be disposed in a row.