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:

Drawers
Fig. 100 In the front seat: drawer First read and observe the introductory information and safety warnings There may be a drawer under each of the front seats. Opening or closing the drawer To open press the button in the drawer grip (arrow) and open the drawer. To close, push the drawer u ...

Repair Instructions for the Underbody and Stone Chip Protection
Note The underbody and stone chip protection structure must be restored back to its original layer strength and appearance during a repair. Water drain holes must remain free. All threade ...

Rain/light sensor
Fig. 75 Windscreen wiper lever: setting the rain/light sensor Ⓐ Fig. 76 Sensitive surface of the rain/light sensor First read and observe the introductory information and safety warnings When the rain/light sensor is activated, it automatically controls the frequency of the wiper inte ...