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:

Using the menus in the instrument cluster
Fig. 13 Vehicles without multifunction steering wheel: press button ① in the windscreen wiper lever to confirm the menu point and rocker switch ② to change the menu Fig. 14 Vehicles with multifunction steering wheel: control buttons for menus in the instrument cluster First read and ob ...

Fitting the removable ball coupling
Fig. 91 Overview: removable ball coupling First read and observe the introductory information and safety warnings The removable ball coupling is located under the luggage compartment floor with the vehicle toolkit. Key for : Cap Ball coupling Retaining balls Catch for locking ...

Introduction
This chapter contains information on the following subjects: → Stowing items of luggage → Driving with an open tailgate → Driving a loaded vehicle → Vehicle-specific weight ratings Heavy objects must always be stowed securely in the luggage compartment and y ...