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:

Stowage
Fig. 161 In the luggage compartment underneath the floor covering A: Spare wheel and vehicle toolkit without ball coupling, B: Spare wheel and vehicle toolkit with ball coupling, C: Spare wheel and vehicle toolkit without ball coupling First read and observe the introductory information an ...

Refrigerant Circuit with A/C Service Station, Filling
Caution If it is suspected that chemicals were added to the refrigerant circuit to seal leaks, do not connect the A/C service station and do not extract the refrigerant. ...

A/C Compressor with A/C clutch
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 ...