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:

Controls for the air conditioning system
Fig. 125 In the centre console: air conditioning controls (manual) Fig. 126 In the centre console: Climatronic controls First read and observe the introductory information and safety warnings Press the corresponding button to switch a function on or off. When a function is switched on, ...

Tread depth and wear indicators
Fig. 147 Tyre tread: wear indicators First read and observe the introductory information and safety warningsTread depth Difficult driving situations demand the deepest possible tread depth for the tyres and the same tread depth for the tyres on the front and rear axles. This applies in pa ...

General Information
The following descriptions also apply to Left Rear Cigarette Lighter -U3-, Right Rear Cigarette Lighter -U7-, Rear Cigarette Lighter -U9-, 12 V Socket 2 -U18-, 12 V Socket 3 -U19-, 12 V Socket 4 -U20-, Cigarette Lighter 2 -U25- and 12 V Socket 5 -U26- if ...