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:

Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308
Function: The Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308- determines the temperature behind the evaporator. This value goes to the air conditioning control module and serves as a reference signal for ...

Opening and closing the bonnet
Fig. 134 A: release lever in the footwell on the driver side. B: release lever on the bonnet Fig. 135 C: holder for the bonnet stay in the lock carrier. D: bonnet secured with the bonnet stay First read and observe the introductory information and safety warningsOpening the bonnet Ensu ...

How to start the engine using jump leads
Fig. 191 How to connect the jump leads when starting vehicles without start/stop system: discharged battery Ⓐ and battery providing assistance Ⓑ Fig. 192 How to connect the jump leads when starting vehicles with start/stop system: discharged battery Ⓐ and battery providing assistance ...