A desiccant dehumidifier operates on a totally different principle to a refrigerant type. The main benefit of a desiccant dehumidifier is that it performs exceptionally well when used in cooler climates, or when a low dewpoint is required.
As there is no actual water produced during the process, these units can work effectively at sub-zero temperatures. The rotor (the heart of the dehumidifier), is manufactured from alternate layers of flat and corrugated sheets, impregnated with an active component (desiccant). It is made to form a vast number of axial air channels running parallel through the structure.
As air passes through these channels, moisture is transferred between the air and the desiccant in its vapour form. The rotor is generally divided into two air zones which are separated by seals, the process sector (typically 75%), and the reactivation sector (typically 25%). The rotor is rotated slowly (approximately 8 to 12 rph) using a small geared drive motor.
System air is pulled through the larger process sector where moisture is adsorbed from the air by the rotor material. The air leaves the dehumidifier warm and dry. Most of the heat gain is due to energy exchange during adsorption.