Adsorption dehumidifier TTR-series
While the dehumidification process is based on the dew point in case of condensation dryers, desiccant dehumidifiers use the principle of sorption. Here, the vapour pressure gradient between the humid air and a hygroscopic sorption agent is used for water withdrawal from the air.
This category also includes dehumidification granules, although they are at best suited for keeping the inside of small, closed containers dry.
Granules – a rather bland solution
The original and main purpose of these pouches is to protect moisture-sensitive goods during transport and storage. Everyone knows the little bags that come in new handbags, electronic devices, pharmaceuticals or clothing.
Therefore, granules do not serve as a true alternative to dehumidifiers. Moreover, they are an uneconomical single-use solution requiring the user to regularly buy fresh granule bags for the receptacle since the granules are not regenerated. Much like a sponge, the desiccant permanently absorbs water from the air and must be replaced as soon as it is saturated – a highly cost-intensive procedure in the long run.
The case is different with electrical devices with hot air regeneration. They have an integrated, rotating desiccant wheel coated with highly hygroscopic materials such as silica gel or lithium chloride that withdraw the water molecules from the sucked in air flowing through the desiccant wheel.
To ensure that the desiccant wheel can take up moisture continuously, the latter must be given off again in some way. This is done by hot air generation: hot air is guided through a regeneration zone of the desiccant wheel and uses its thermal energy to remove the water vapour previously bound in the rotor from the silica gel.
Comfort devices with condenser
These devices designed for private use work on the same principle as desiccant dehumidifiers for commercial applications.
The sucked-in room air is guided through the dehumidification sector of a rotating desiccant wheel coated with a hygroscopic sorption agent on which the moisture from the air deposits.
Silica gel is a typical sorbent – a desiccant with a very large hygroscopic surface. In professional industrial desiccant dehumidifiers, each gram of this desiccant has a surface of more than 700 square metres. This means that less than 10 grams have a surface as large as an entire football pitch.
The dry air – dehumidified since the moisture was taken up by the desiccant – is then blown out into the room again.
To remove the water from moisture-loaded desiccant wheel, warm air heated by a heating element flows through a separate regeneration sector of the desiccant wheel in a continuous circuit. Owing to its temperature, the air can take up the moisture from the desiccant wheel and then guides it through a condenser element.
The cooler intake air simultaneously circulates around the condenser element, which is why the water inside the element condenses and drips into a water tank. The regeneration air is then refed to the heating element in a constant circuit to take up new moisture.
