Opel 1900 1973 Service Manual page 538

AS A HIGH PRESSURE-HIGH
TEMPERATURE VAPOR
2
UPON REMOVAL OF HEAT
VAPOR BECOMES HIGH
PRESSURE LIQUID REFRIGERANT
within
certain operating limits. If these limits are
exceeded, many physical and chemical reactions oc-
cur. Since the results of these reactions within the
system cannot be easily removed, they build up into
a constantly accelerating vicious circle to eventually
fail the system.
CHEMICAL INGREDIENTS OF AN AUTOMOTIVE
AIR CONDITIONING SYSTEM
All systems involve metals, refrigerant, and oil which
are basic and essential. The desiccant, or dehydrating
agent, and another chemical ingredient, synthetic
rubber, makes it even more complex.
All of these ingredients have chemical properties
which are entirely different from each of the others.
In spite,of these differences, by proper selection of
the ingredients and controlled processes in manufac-
ture, plus careful servicing procedures they can be
combined so that they "live together" to provide
many years of satisfactory and trouble-free operat-
ion.
If, however, only one undesirable element is added or
REFRIGERANT COMPONENTS ALL MODELS
REFRIGERANT RETURNS TO
COMPRESSOR AS LOW PRESSURE
EXPANSION VALVE
3
LIQUID REFRIGERANT IS STORED
HERE UNTIL NEEDED
Figure 98-23 Basic Refrigeration
is allowed to enter the system, it can start a chain of
chemical reactions which upsets stability and inter-
feres with the operation of the unit.
M e t a l s
In most cases, metals contribute to the decomposi-
tion of R-12 and oil in varying amounts. All are
attacked by acids.
Each of the metals in common use in a system has
been selected for a specific reason; heat conductivity,
durability, strength, and chemical composition.
Under favorable conditions, the amounts of decom-
position of Refrigerant-12 and oil produced by these
metals is negligible and allowable. However, if un-
desirable substances are added and the temperature
is increased, the rate of decomposition and the pro-
duction of harmful acids increases proportionally.
Refrigerant
The chemical properties of refrigerants are very im-
portant factors in the stability of a system since the
VAPOR
FROM AIR VAPORIZES
LOW PRESSURE
LIQUID REFRIGERANT
4
HIGH PRESSURE
TO LOW PRESSURE
LIQUID AT THIS
POINT
Cycle