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:
Fitting the front towing eye
Fig. 193 In bumper at front right:
depiction of variants for screwing in towing eye
First read and observe the introductory
information and safety warnings
The towing eye is screwed into a threaded hole behind a cover on the right of
the front bumper .
The towing eye must always be kept i ...
Winter tyres
First read and observe the introductory information
and safety warningsIn winter road conditions, winter tyres will considerably
improve the car's handling. The design of summer tyres (width, rubber compound,
tread pattern) gives less grip on ice and snow. Volkswagen urgently recommends the
...
Switching the TCS on and off
Fig. 116 In the centre console: button
for switching the TCS on and off manually
First read and observe the introductory information
and safety warnings The electronic stability control (ESC) only
functions when the engine is running. It consists of ABS, EDL and TCS.
When the engine is r ...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information