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:

Attaching child seat with lower anchoring points (ISOFIX)
Fig. 64 On vehicle seat: different markings identifying the lower anchoring points for child seats First read and observe the introductory information and safety warnings 2 retaining rings, also known as lower anchoring points, are fitted to each outer rear seat. Overview of installation ...

Pressure Relief Valve
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 ...

Stowage compartment on the front passenger side
Fig. 97 Stowage compartment on the front passenger side Fig. 98 Open stowage compartment on the front passenger side First read and observe the introductory information and safety warnings Opening and closing the stowage compartment To open, pull up the opening lever . To close ...