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:

Vents
Fig. 128 In the dash panel: vents First read and observe the introductory information and safety warnings The vents should be left open to ensure that the vehicle interior is sufficiently heated, ventilated and cooled. Turn the relevant thumb wheel (magnified view) in the required ...

Decorative Trims, Replacing, Bonded Decorative Trims
Special tools and workshop equipment required Cartridge Gun -VAG1628- Trim Removal Wedge -3409- Wiring Harness Repair Set - Hot Air Blower -VAS1978/14A- Materials ...

Cigarette Lighter Illumination Bulb -L28-, Removing and Installing
Note On some vehicle equipment levels, socket illumination is via Light Emitting Diode (LED) instead of a bulb. These LEDs are integrated with the illumination housing and cannot be serviced or replaced separately. ...