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:
A/C System, Operating after Charging
Caution
If it is suspected that chemicals were added to the
refrigerant circuit to seal leaks, do not connect the
A/C service station and do not extract the refrigerant.
...
Changing bulbs in the front headlights (halogen H4)
Fig. 178 Rear view of the
right-hand H4 headlight with plastic covers: ① dipped beam and main beam, ② turn
signal and ③ side light
Fig. 179 Rear view of the
right-hand H4 headlight with rubber cover: ① dipped beam and main beam, ② turn
signal and ③ side light
First read and o ...
Upper section of the centre console
Fig. 7 Overview of the upper section of
the centre console
Key for :
Vent
,
Button for:
Seat heating for the left and right
Traction control system (TCS)
Rear window heating
Hazard warning lights
Indicator l ...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information