Volkswagen Polo Service & Repair Manual: Critical Point
| Vehicle air conditioning systems make use of the
vaporization and condensation process. In this case, one works
with a substance which boils easily, designated as refrigerant. |
| The refrigerant employed is tetrafluoroethane R134a, which
boils at -26.5 °C (-15.7 °F) at a vapor pressure of 1 bar (14.5
psi). |
| The critical point (critical temperature and critical
pressure) is that above which there is no longer a boundary
between liquid and gas. |
| A substance above its critical point is always in the
gaseous state. |
| At temperatures below the critical point, all types of
refrigerant in pressure vessels exhibit both a liquid and a gas
phase, i.e. there is a layer of gas above the liquid. |
| As long as there is still gas present in the container next
to the fluid, pressure is dependent on ambient temperature.
Refer to
→ Chapter „Refrigerant R134a Vapor Pressure Table“. |
 Note
| Different types of refrigerant are never to be mixed. Only
the refrigerant designated for the corresponding A/C system may
be used. |
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Vehicle air conditioning systems make use of the
vaporization and condensation process. In this case, one works
with a substance which boils easily, designated as ref ...
Vehicle air conditioning systems make use of the
vaporization and condensation process. In this case, one works
with a substance which boils easily, designated as ref ...
Other materials:
Engine oil specification
First read and observe the introductory information
and safety warningsThe engine oil used must correspond exactly to specifications.
The correct engine oil is important for the function and service life of the
engine. A special high quality multigrade oil has been filled at the factory and
t ...
Performance figures
First read and observe the introductory information
and safety warnings
For reasons of vehicle registration and vehicle taxation, the power output and
performance of some engines may vary in some countries from the information given
in this booklet.
Petrol engines
...
Extraction System Group Classifications
At this time, A/C service units for extracting, cleaning and
filling refrigerant for motor vehicle A/C systems are available
from various manufacturers.
Group 3:
Mobile extraction and charging systems for filling
c ...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information