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:

Automatic gearbox: selecting a gear
Fig. 111 Left-hand drive vehicles: selector lever for automatic gearbox with lock button (arrow) Fig. 112 Right-hand drive vehicles: selector lever for automatic gearbox with lock button (arrow) First read and observe the introductory information and safety warnings The selector lever is ...

Midtronics Battery Tester -MCR340VKT-, Troubleshooting
Sometimes the display shows the malfunction or the messages based on the condition. The following is a list of the most frequent displayed messages together with suggested solutions. Note Refer to the MCR3 ...

Crimping Pliers with Insert
The Crimping Pliers without Insert -VAS1978/1- with Crimping Pliers - Insert 2 -VAS1978/2- is a component of the Wiring Harness Repair Set -VAS1978- and is used to crimp the connector during the wiring harness repair. ...