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.