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:

Wheel cover
Fig. 163 Removing press-on wheel covers Fig. 164 Removing bolted-on wheel covers First read and observe the introductory information and safety warnings Removing and fitting press-on wheel covers Take the box spanner and wire hook from the toolkit . Insert the wire hook into o ...

Performance figures
First read and observe the introductory information and safety warnings For reasons of vehicle registration and vehicle taxation, the power output and performance of some engines may vary in some countries from the information given in this booklet. Petrol engines ...

Wiring Eyelets, Repairing
Special tools and workshop equipment required Torque Wrench 1331 5-50Nm -VAG1331- Note Do not use rust remover, contact spray or grease because the lack of friction will cause the torque to be ...