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:

Fuses in the vehicle
Fig. 172 Dash panel on the driver side: fuse box cover Fig. 173 In the front left of the engine compartment: fuse box cover First read and observe the introductory information and safety warnings Fuses must always be replaced by a new fuse with the same amp rating (same colour and marki ...

Wires with Cross Section up to 0.35 mm 2, Repairing
Special tools and workshop equipment required Crimping Pliers - .35-2.5mm -VAS1978/1A- Wiring Harness Repair - Crimping Head - .35-2.5mm -VAS1978/1-1- When repairing wires with a cross- ...

Vehicle key
Fig. 18 Vehicle key Fig. 19 Vehicle key with alarm button First read and observe the introductory information and safety warnings Vehicle key The key can be used to lock and unlock the car from a distance . The remote control transmitter and the battery are integrated in the key. The re ...