flow 10 in the embodiment the passage 9 is an air duct the fresh air flow 10 is generated by a fan 11 when flowing around the sorption unit 5 the flow of fresh air 10 receives the heat liberated in the adsorption process and transfers the heat by means of a heat exchanger 12 to the process air of the air circuit 3 because of the cold water vapor the heat exchanger 2 is cooled significantly more than in a conventional air to air operation the condensation efficiency of the heat exchanger 2 is increased downstream to the heat exchanger 2 the process air first flows through the heat exchanger 12 and then through a multistage electric heater 13 for energetic reasons the heater 13 should be constructed with multi stages so only the lack of energy can be added to the process air stream before the process air stream flows back into the drying chamber 1 the multi stage heater 13 heats the process air flow before it reenters the drying chamber 1 because of the higher condensation level in the heat exchanger 2 the process air flow of the inventive device has a lower relative humidity therefore it can absorb more moisture when it passes through the.