Building materials and structures
are capable of absorbing
considerable volumes of water,
such as brick 90-190 l/m³, heavy
concrete 140-190 l/m³ and
limestone 180-270 l/m³.
The drying of moist materials
such as masonry is effected as
follows:
■
The moisture
moves from
the inside of
the material
to its surface
■
Evaporation occurs on
the surface = transfer of water
vapour to the ambient air
Temp.
Water vapour content in g/m
3
at humidity of
°C
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
■
The air containing water vapour
is constantly circulated through
the REMKO air dehumidifier.
The air is dehumidified and,
slightly heated, leaves the unit
in order to re-absorb water
vapour
■
In this way, the moisture
contained in the material
is reduced gradually.
The material is dried!
The accumulated condensate is collected
in the unit and drained off from there.
Verdampfer
Kondensator
°C
30
25
20
15
% r.F.
100
90
80
70
60
50
40
30
20
10
+
+
-
Lufttemperatur
Luftfeuchte
Verlauf
Luftrichtung
As it flows through or over the evaporator, the air stream is cooled
to dew point. The water vapour condenses, and is collected in a
condensate trap from where it is drained off.
Drying materials
Water vapour
condensation
Because the capacity for
the maximum possible volume of
water vapour increases as the air is
heated, the volume of water
vapour contained remains constant
and so relative humidity falls.
In contrast, because the capacity for
the maximum possible volume of
water vapour decreases as the air is
cooled, the volume of water vapour
contained remains constant and so
relative humidity increases.
If the temperature continues to fall,
the capacity for the maximum
possible volume of water vapour
is reduced so much so that it is
ultimately equal to the volume of
water vapour contained in the air.
This temperature is referred to as
the dew point. If the air is cooled
to below dew point, the volume of
water vapour in the air will become
greater than the maximum possible
volume of water vapour.
At this point, the water vapour
begins to precipitate.
It then condenses to water.
Humidity is then removed from the
air.
Examples of condensation include
steamed-up window panes
in winter, or the moisture on
the outside of a cold drinks bottle.
As the relative humidity of
the air increases, so too does
the dew point, making it easier for
the temperature to fall below it.
Evaporator
Capacitor
Air temperature
Air direction
Air humidity
Progression
% RH
5
