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Air conditioning system with refrigerant R134a - Edition 10.2014
1.3
Basics of air conditioning
lk
1.3.1
Physical basics:
The four known physical states of water also apply to air condi‐
tioning refrigerants.
1 - Gas (invisible)
2 - Vapour
3 - Liquid
4 - Solid
When water is heated in a container (heat absorption), the rising
water vapour is visible. If the vapour is heated by further heat
absorption, the visible vapour becomes invisible gas. This proc‐
ess is reversible. If heat is extracted from gaseous water, it
changes first to vapour, then to water and finally to ice.
A - Heat absorption
B - Heat dissipation
1.3.2
Heat always flows from warmer to colder
material
Every material consists of a mass of moving molecules. The fast
moving molecules of a warmer material loose part of their energy
to slower molecules possessing less heat. This slows down the
molecules of the warmer material and accelerates those with less
heat. This continues until the molecules in both materials are
moving at the same speed. They have the same temperature, and
no further exchange of heat occurs.
1.3.3
Pressure and boiling point
The boiling points given in the table below are always based on
an atmospheric pressure of 1 bar. If the pressure on a liquid is
changed, its boiling point changes also.
It is well known that, for example, the lower the pressure, the lower
the temperature at which water boils.
The vapour pressure curves for water and for refrigerant R134a
show that at constant pressure and falling temperature the vapour
becomes liquid (in the condenser), and that when pressure drops,
the refrigerant changes from liquid into the vapour state (evapo‐
rator).
2
Rep. gr.00 - Technical data
English 
