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:
Introduction
When the outside temperature is low, the display in the instrument cluster
may take slightly longer to appear than it does when the outside temperatures is
higher.
Additional information and warnings:
Warning and indicator lamps
Volkswagen information system
Selected gear di ...
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 ...
Parking Aid Sensor, Painting
The following parameters must be met when painting to avoid
malfunctions in the parking aid sensor (parking aid system):
New Part, Painting
Maximum coat thickness 125 µm; the coat thickness must
always be measured ...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information