Abstract: The invention relates to a heat exchanger provided with channels (3.1, 3.2) which are separated by separating walls, and which are cross-flown in an alternating manner to the counter flow by one or the other flow mediums (W, K). Said heat exchanger is formed by a spiral-shaped, wound, sheet-like material (1). The windings (2.1, 2.2, . . . ) of the spiral form the separating walls between the channels (3.1, 3.2, . . . ). The channels (3.1, 3.2, . . . ) are also separated from each other by separating webs (4.1, 4.2, . . . ) which are arranged between adjacent windings (2.1, 2.2, . . . ).

Abstract: Bicomponent moulded article made of polytetrafluoroethylene (PTFE) which, in the manner of the side-by-side type, is composed of two PTFE components which shrink under the effect of heat and differ in their hot-air shrinkage by at least 1%. A preferred embodiment is in the form of a fibre which can be crimped under heat treatment. (FIG.