Abstract: A heat exchanger for exchanging heat between two media, one of which includes incrusting substances, includes a pair of end walls having a rotary shaft extending rotatably between the end walls. Between the end walls are located disc-shaped hollow members each of which has a central passage for the shaft. The members each have a through opening located on the side of the passage which opening is sealed from the interior of the member. Partitions extend within the hollow members between the peripheral inside of the member, in a place between an inlet and an outlet for the second medium, and the passage. Cleaning arms are non-rotatably connected to and extend radially from the shaft. In a heat exchanger in an assembled state, with an inlet for the first medium at one end wall and an outlet for the first medium at the other end wall, a cleaning arm is alternatively located between each member between the end walls. A cleaning arm is also located between each end wall and the member adjacent to each end wall.