Abstract: A regenerator with a hollow cylindrical heat exchange roller which is provided with a jacket of heat carrier material with separated flow regions that are passed through by a flow medium emitting heat and a flow medium receiving heat. The hollow cylindrical roller has a partition wall which separates the flow regions. The flow media pass through the regions by substantially radial passages through the jacket and transverse to the axis of rotation of the heat exchange roller. A housing which holds the roller is provided with radial inlet and outlet channels for the flow media. These channels are displaced from one another by substantially 90.degree..