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:
Run-Flat System PAX, Examining Support Ring
As with the tire, the supporting ring is generally not
replaced after driving with flat tire.
Replace the support ring if the following damages have
occurred:
Blowouts or mis ...
Tires and Rims, Matching
If necessary repair flat spots from standing. Refer to
→ Chapter „Flat Spots, Correcting“.
–
Dismount the tire. Refer to
→ Chapter „Tires, Dismounting“.
–
Turn the ...
Tires, Dismounting, Run-Flat Tires and Ultra High Performance Tires
Only trained personnel can perform the assembly work on
run-flat tires and ultra high performance tires.
If equipped check the tire pressure monitoring sensor with
the vehicle diagnostic tester and if necessary replace.
...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information