Refrigerant R134a
Vehicle air conditioning systems make use of the vaporization and condensation process. Use is made of a substance with a low boiling point.
The refrigerant employed is tetrafluoroethane R134a, which boils at -26.5 C at a vapor pressure of "1 bar".
Physical Data
| Chemical formula | CH2FCF3 or CF3CH2F |
| Chemical designation | Tetrafluoroethane |
| Boiling point at 1 bar | - 26.5 ° C |
| Solidification point | -101.6 ° C |
| Critical temperature | 100.6 ° C |
| Critical pressure | 40.56 bar (absolute) |
Critical Point
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 both liquid and gas are present in the vessel, the pressure is governed by ambient temperature. Refer to → Air Conditioning System Principles .
- Different types of refrigerant are never to be mixed. Exclusive use is to be made of the refrigerant specified for the respective air conditioning system.
Environmental Aspects
- R134a is a fluorocarbon and contains no chlorine.
- R134a has a shorter atmospheric life span than refrigerant R12.
- R134a does not deplete the ozone layer.
- The global warming effect of R134a is "ten" times less than that of refrigerant R12.