|
The use of a humidifier can allow the
reproduction of dust mites or the growth of harmful mold, which can be
especially harmful for children and the elderly. The relative humidity
should not normally be increased above 55%.
Dehumidifier
Mechanical/refrigerative
dehumidifiers
They usually work by drawing moist air
over a refrigerated metal coil with a fan. Since the saturated vapor
pressure of water decreases with decreasing temperature (i.e. cold air
can hold less water vapor), the water in the air condenses, and drips
into a collecting bucket. The air is then reheated by the warmer side of
the refrigeration coil.
Most dehumidifiers can be adapted to connect the drip output directly to
a drain. Manufacturers may price dehumidifiers differently solely on the
size of the collection bucket. There are usually sensors to detect when
the collection bucket is full.
Air conditioners automatically act as dehumidifiers when they chill the
air and thus need to handle the accumulated water as well. Window units
simply allow the water to drip outside. Central air conditioning units
need to be connected to a drain.
Desiccant
dehumidifiers
A desiccant dehumidifier is a
device that employs a desiccant material to produce a dehumidification
effect. Desiccant materials have a high affinity for water vapor.
Typically their moisture content is a function of the relative humidity
of the surrounding air. Exposed to low relative humidities desiccant
materials come to equilibrium at low moisture contents and exposure to
high relative humidities results in equilibrium at high moisture
contents. The process involves exposing the desiccant material to a high
relative humidity air stream, allowing it to attract and retain some of
the water vapor and then exposing the same desiccants to a lower
relative humidity air stream which has the affect of drawing the
retained moisture from the desiccant.
In general a desiccant dehumidifier is comprised of four major
components. The component that holds the desiccant of which there are
several types, a fan to move the air to be dehumidified (process air)
through the desiccant holder, a fan to move the low humidity air for
drying the desiccant through the desiccant holder and a heater to heat
the air that will be used to dry the desiccant (regeneration air).
Relative effectiveness
of dehumidifiers
Refrigerant dehumidifiers are more
efficient when the air is quite humid (over about 45% relative humidity,
higher if the air is cold). Sometimes, they are used in tandem, such as
when the air is very humid, and needs to be made very dry. Source: Wikipedia
More Humidifier/dehumidifier Information
|