Product Presentation; Areas Of Use - ITM Italia EURODRY EFT Serie Manual De Instrucciones

2.

Product presentation

2.1

Areas of use

The dehumidifiers of the EFT series reduce air moisture by condensing the water contained in it. The purpose of
these machines is to dehumidify civil and industrial environments. They are ideal in the construction business for
drying new buildings, flooded buildings, basements/cellars, storage rooms, controlling the humidity in storerooms,
etc.
2.2 Information about dehumidifying the air
This paragraph presents the basic elements for understanding the phenomena involved in dehumidifying the air
and describes the effects of moisture in various situations.
2.2.1 Air moisture
It is well known from experience that ambient air generally contains a certain amount of water in the form of vapor
and this is commonly referred to as air moisture. In actuality to correctly describe the characteristics of moist air we
should define the term 'air moisture'. Before defining this term, let us observe fig. 1.
Fig. 1 Air moisture
of traces of condensation which, we suppose are located at the bottom for the sake of clarity. This simple
experiment allows us to make certain important statements.
Firstly we can state that during the transformation process the temperature t2 at which the air releases traces of
condensation is the dew point. Above said temperature the water is present in the air only in the form of vapor.
Secondly we can state that above the dew point the ratio between the water mass in the form of vapor and dry air
mass remains the same. In fact, in this condition the number of air particles and vapor particles is the same. We
also observe that the volume of the mixture drops during cooling. These phenomena can all be traced to the
fundamental laws of gases, which we shall not delve into here.
If we continue to cool the air, we notice an accumulation of water that becomes more abundant as the temperature
t2 of the initial mixture drops. Now we can conveniently define the concept of absolute air humidity as the ratio
between the vapor mass and dry air mass. We can immediately deduce that all the transformations of the air which
occur at temperatures above the dew point have absolutely constant humidity values. Absolute humidity is
commonly referred to as the vapor content of the air.
In practical language, nonetheless, we usually use the concept of relative humidity of the air, the meaning of
which we shall now explain.
Going back to our experiment we can immediately observe that the air at temperature t1 is able to further absorb
water in the form of vapor that would otherwise remain in the dew condition, also called state of saturation. To
further humidify the air while maintaining it constantly at the temperature of t1 we must inject water and provide
heat to vaporize it. At a certain point, if we maintain a constant temperature, we will note that the water we are
injecting remains in the liquid state because the state of saturation of the air has already been reached. In this case
the number of vapor particles has increased while the dry air remains the same. From these considerations we can
express an index for the humidity by defining it as the ratio between the vapor mass in the air being examined and
the vapor mass that said air would be able to contain
Taking into consideration a certain volume of air
at atmospheric pressure and temperature t1,
imagine separating the water molecules (in the
form of vapor) from those the molecules in the
form of gases making up the air. The crosses in
the figure correspond to the vapor while the
circles signify dry air. The vessel depicted in the
figure has a movable lid of negligible weight that
is perfectly watertight to ensure a constant
pressure (atmospheric) inside the vessel.
Let us now suppose we gradually cool the air by
removing heat from the walls. During this
operation we observe that the movable lid sinks
and at a certain point we notice the appearance
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