How Dehumidifiers Work to Remove Moisture from the Air

Air humidifiers, as you know, add humidity to the air. Dehumidifiers, on the other hand, remove moisture from the air and lower the relative humidity. Excess moisture can cause damage to the structure of homes. My parents had a dehumidifier, and I always wondered how it worked.

Condensation--you've seen it. Water forming on the outside of a cold glass? That's condensation. When warm air is exposed to a cold surface, water is pulled from the air, collecting on the cool surface. Dehumidifiers use the same principle to extract moisture from the air.

Dehumidifier Basics

A dehumidifier uses a fan that pulls air inside and across a metal coil, which is cooled with a compressor. Then the air is re-heated and exhausted, once the water has been collected on the coils. It subsequently falls into a reservoir, where the water is drained. The reservoir has to be emptied regularly to avoid overflowing, either manually or through a hose that drains into the floor drain or a pump.

Types of Dehumidifiers

The type of dehumidier we just discussed describes a refrigerative model. There are also desiccant dehumidifiers, portable, restoration, and whole-house dehumidifiers.

Desiccant dehumidifiers: These types of dehumidifiers pull air inside and pass it over a desiccant material, like silica gel. A desiccant naturally absorbs moisture, so the air does not need to be cooled before dehumidifying it.

Portable dehumidifiers: These are the kind of dehumidifiers that you will find in home improvement stores; this is the kind that my parents had. They are very lightweight, often made of plastic, and very affordable.

Restoration dehumidifiers: These are heavy-duty machines designed to withstand harsh conditions, and are typically used to repair heavy water damage from natural disasters.

Whole-house dehumidifiers: This is the largest model on the market; it needs to be installed by a professional to augment the home's heating, ventilating and air conditioning system.

Other Factors

There are several factors that affect a dehumidifier's performance level. Air movement, ambient air temperature, relative humidity: These all factor into the performance of a dehumidifier. The more air a dehumidifier can move, the better job it will do removing moisture from it. The cooler the air is, the harder the dehumidifier will have to work to cool it even more. And the higher the relative humidity is, the easier it will be to remove moisture from the air.

References
Dehumidifier Basics
Types of Dehumidifiers
How Dehumidifiers Work