Condair Esco

9 Vaporisation / condensation
9.1 Terminology and definitions
• Vaporisation
Vaporisation is understood to be the transition of a liquid into the gaseous
stage upon reaching the substance’s boiling point. The onset of the
boiling process depends on the following parameters:
• Steam pressure of the liquid
• Ambient pressure
• Temperature
• Substance
• Saturated vapour pressure
The saturated vapour pressure is that value, which is characterised by
the balance between the ambient pressure and the vapour pressure
of a liquid.
Once the equilibrium is reached, vaporisation of the liquid takes place;
this is called saturated steam.
The steam pressure of a liquid is temperature-dependent so that the
pressure equilibrium, at which evaporation begins, is characterised for
each substance by a temperature pressure curve. This curve is called
saturated steam curve.
• Saturated steam
Steam that reaches the saturated steam pressure but is not separated
from the liquid phase, interacts with the liquid, i.e. the amount of water
that vaporises equals the amount of steam that condenses. Steam, in
such an interactive state, is called saturated steam.
Most important characteristic:
Saturated steam is not compressible (a part of it would condense in
the process).
• Wet steam
When saturated steam cools down (e.g. by heat loss) part of it condenses,
and the share of water droplets in the steam increases. This
is called wet steam.
• Superheated steam
Steam, which is separated from the liquid and heated up, is called
superheated steam.
Most important characteristic:
Superheated steam is compressible.