4
Air Dehumidification
The processes that take place during air dehumidifica-
tion are based on physical laws. We will try to describe
these in a simplified form to give you a general idea
about the principle of air dehumidification.
There are two different ways of drying buildings:
1. B y h ea t in g a n d ex c ha n g in g t he a ir :
The ambient air is heated to absorb moisture and ex-
pelled to the outside. However, the total generated
energy is lost with the expelled humid air.
2. B y d eh um id if yi n g:
The humid air in the closed room is continuously de-
humidified based on the principle of condensation.
With respect to energy consumption, dehumidification
offers one important advantage:
Energy is only needed for the existing room volume.
The mechanical heat released during the dehumidifica-
tion process increases the room temperature slightly.
When used properly, the air dehumidifier consumes on-
ly approx. 25 % of the energy to be supplied according
to the “heating and ventilation” principle.
As you can see, the corrosion rate is insignificant at a
relative air humidity of less than 50 % and at a humidity
rate of less than 40 %, it can even be ignored. When
the relative humidity exceeds 60 %, the corrosion rate
increases considerably.
This limit for damage caused by humidity also applies
for many other materials, such as powdery substances,
packing materials, wood, and electronic devices.
Relative air humidity
Ambient air is a gas mixture which always contains a
certain percentage of water as water vapour.
This percentage of water is indicated in g per kg of dry
air (absolute water content).
1 m³ of air weighs approx. 1.2 kg at 20° C.
Depending on the temperature, each kg of air can only
absorb a defined quantity of water vapour. When this
quantity has been absorbed, the air is “saturated” and
has a relative humidity of 100 %.
Relative air humidity is defined as the ratio between the
percentage of water vapour contained in the air at the
moment in question and the maximum possible per-
centage of the water vapour when the temperature is
the same.
The capacity of air to absorb water vapour increases
when the temperature rises. This means that the maxi-
mum possible (= absolute) water content is increased
as the temperature increases.
The use of REMKO air dehumidifiers
◊
No matter how well doors and windows are insulat-
ed, dampness and moisture penetrate even thick
concrete walls.
◊
It can take up to 1 or 2 months for the water used in
the production of concrete, mortar, plaster, etc. to
dry.
◊
The moisture that penetrates brickwork as a result of
flooding is released very slowly.
◊
E.g. this is also the case regarding moisture con-
tained in materials in storage.
The moisture escaping from parts of buildings or materi-
als (water vapour) is absorbed by the ambient air. Con-
sequently the humidity of the air increases which results
in corrosion and in formation of mildew, decay, flaked
off paint and other unwanted damage.
The diagram below is an example of the corrosion rate
of metal at different air humidity levels.
Temp. °C
Water vapour content in g/m³ at an air humidity of
40%
60%
80%
100%
-5
1.3
1.9
2.6
3.3
+10
3.8
5.6
7.5
9.4
+15
5.1
7.7
10.2
12.8
+20
6.9
10.4
13.8
17.3
+25
9.2
13.8
18.4
23.0
+30
12.9
18.2
24.3
30.3