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:
Checking with Restrictor and Reservoir, with Internally Regulated A/C
Compressor
Note
Connecting service station. Refer to
→ Chapter „Connecting Service Station“.
Observe test requirements. Refer to
→ Chapter „Pressures, Checking“.
–
...
Introduction
This chapter contains information on the following subjects:
→ Vehicle identification data
→ Engine data
→ Dimensions
→ Performance figures
The vehicle data sticker in the service schedule or the vehicle registration
documents show which engine is installed i ...
Introduction
This chapter contains information on the following subjects: → Wheel cover
→ Wheel bolt caps
Additional information and warnings:
Tyre monitoring system
Cleaning and caring for the vehicle exterior
Vehicle toolkit
Changing a wheel
Breakdown set
...
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Refrigerant R134a Physical Data
Refrigerant R134a Environmental Information