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:

Dimensions
Fig. 17 Dimensions First read and observe the introductory information and safety warnings The data in the table apply to the most basic German model. The specified values can vary due to different tyre and wheel sizes, if additional equipment is fitted, for different model versions, for ret ...

Sun visors
Fig. 70 Sun visor First read and observe the introductory information and safety warnings Various positions for the driver and front passenger sun visors: Folded down over the windscreen. Pulled out of the bracket and swung over towards the door . Vanity mirror light There is a v ...

A/C Compressor without Magnetic 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 ...