Functional principle of the air dehumidifier
As it flows through or over the evaporator, the air stream is cooled to dew point. The water vapour con-
denses, and is collected in a condensate trap from where it is drained off.
2
1
A
B
C
a
Fig. 4: Functional principle of the air dehumidifier
1: Evaporator
2: Condenser
A: Air temperature
B: Air direction
C: Humidity
a: Progression
The condensation of water vapour
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 out-
side of a cold drinks bottle.
As the relative humidity of the air increases, so too
does the dew point, making it easier for the tem-
perature to fall below it.
Condensation heat
The energy transferred to the air from the con-
denser consists of:
1.
the amount of heat derived beforehand in the
evaporator
2.
the electrical drive energy
3.
the condensation heat released by the lique-
fying of the water vapour.
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