A motor vehicle dehumidifier, including a dehumidifying
drying agent, that can provide a required dehumidifying capacity with a reduced overall quantity of
drying agent compared to conventional
drying agent-based dehumidifiers. In the present invention, a
heat exchanger is disposed on an upstream side of a drying agent unit, and heat is exchanged in the
heat exchanger between inside air to be dehumidified and low-temperature outside air used to cool the inside air. The air cooled by the
heat exchanger flows into the drying agent unit and is dehumidified. Because the air has an increased
relative humidity as a result of being cooled, the amount of water adsorbed from it per unit of drying agent is increased, as the water adsorption characteristic of the drying agent is greatly influenced by the
relative humidity of the air passing over it, and is markedly improved by an increase in the
relative humidity of that air.