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:
Pressure Gauge, Tests and Measurements
Indicators on pressure gauge
1 -
Temperature scale for refrigerant R134a CF3–CH2F or
CH2F–CF3.
2 -
Pressure scale
The pressure gauge may have one or more temperature s ...
Radio reception and aerials
First read and observe the introductory information
and safety warningsFor factory-fitted radio or navigation systems, the aerial
for radio reception can be installed in various locations in the vehicle:
On the inside of the rear window, together with the rear window heating.
On the i ...
Checklist
Observe the following information both before and during every journey
to ensure your own safety, and the safety of all passengers and other road users
:
Check that all lights and turn signals are
working properly.
Check the tyre pressure Wheels and tyres
Wheels and tyres Tyres ...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information