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:

Introduction
This chapter contains information on the following subjects: → Washing the vehicle → Washing the vehicle with a high-pressure cleaner → Cleaning windows and exterior mirrors → Cleaning and changing windscreen wiper blades → Waxing and polishing the ve ...

Run-Flat Tire, Structure and Identification, SST Tire
Run-Flat Tires, Dismounting and Mounting. Refer to → Chapter „Tires, Mounting“. A Tire Pressure Monitoring Display is Necessary When Using Run-Flat Tires. Tire Damage and the Pressure Loss Resulting From it ...

Introduction
This chapter contains information on the following subjects: → Contents of the breakdown set → Preparation → Sealing and inflating tyres → Test after driving for 10 minutes You can use the breakdown set (tyre mobility set) to safely seal any tyre damage cau ...