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How Desiccant Dehumidifiers Work
Sep 02, 2018

How Desiccant Dehumidifiers Work


Desiccant dehumidifiers ignore complicating factors like dew point temperature because they operate using a completely different principle. Specifically, desiccants attract water on a chemical level, and can do so through various means. However, the vast majority of desiccant dehumidifiers use silica gel, which cranks up the rate of condensation by greatly increasing the available surface area of water to adhere to and condense. Here’s a quick look at how a desiccant dehumidifier works:

    1. Humid area is drawn into the desiccant dehumidifier, and pushed across a rotating disc impregnated with silica gel. The disc resembles a bundle of straws through which air can flow, and the silica gel is lined along the inside of these tubes.
    2. The silica gel is filled with nano-sized pores, increasing the surface area of the gel exponentially. In fact, a single teaspoon of silica gel has so many pores that its surface area is similar to the surface area of a football field.
    3. With so much area to condense on, the kinetic energy threshold separating vapor molecules and condensed water molecules dips greatly, meaning vapor molecules exhibiting less energy will be much more likely to condense.
    4. As water collects on the disc, a portion of the air drawn into the dehumidifier is heated and used to recharge the condensation so that it vaporizes again. This air is ducted to the exterior to deposit the water outside and is returned to the building. The remaining dry air is shunted back into the room.

Because desiccant dehumidifiers work using chemical properties, they are unaffected by low dew points and relative humidity. This makes them much more efficient in drier settings and they can be used to drop the relative humidity of a space to nearly one percent. However, they aren’t as energy efficient and fast as thermal condensers when the temperature and relative humidity is higher, so many locations use both to complement each other’s strengths and shortcomings.

That’s a quick look at the science behind the most common dehumidifiers on the market. Of course, it gets more complicated than that, and the physics involved are fit for a college level class, but what’s important is that both technologies are reliable, easy to control and are extremely effective at doing their jobs.