Volkswagen Polo Service & Repair Manual: Critical Point

Volkswagen Polo Service & Repair Manual / Refrrigerant R134a Servicing / A/C System, General Information / Refrigerant R134a / 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.

Refrigerant R134a Physical Data

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 ...

Refrigerant R134a Environmental Information

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:

Electrically-Driven A/C Compressor for High Voltage System
Caution Non-approved tools or materials such as leak sealing additives can cause damage or malfunctions in the system. Only use tools and materials approved by the manufactu ...

Checking with Expansion Valve, Receiver/Dryer and A/C Compressor Regulator Valve -N280-, Externally Regulated A/C Compressor
Specified Values Note Connecting service station. Refer to → Chapter „Connecting Service Station“. Observe test requirements. Refer to → Chapter „P ...

Front airbags
Fig. 56 Location and deployment zone of the driver front airbag Fig. 57 Location and deployment zone of the front passenger front airbag First read and observe the introductory information and safety warnings In conjunction with the seat belts, the front airbag system gives the front occu ...