Device for drying air for motor vehicles

An air dehumidifier or drier, particularly for a motor vehicle, has an air guiding housing defining three parallel air flow paths, which are defined by a common main air chamber separating two laterally spaced apart secondary air chambers. A reactor containing an adsorbent is positioned between the secondary air chambers, the common main air chamber being defined between the reactors. Air-flow control elements are positioned in each of the main and secondary air chambers. The control elements are pivotal between two operating positions. In each position, one of the reactors is in adsorption operation (dehumidify air) while the other reactor is in desorption operation (reactor being dried or recharged). The desorption air directed to the reactor being dried is heated by a heat exchanger, which has an air passageway for exhausting the air used for drying the reactor. Thus, the desorption air directed to the reactor being dried is preheated using the energy from the exhausting air.