Volkswagen Golf Service & Repair Manual: Refrigerant R134a
| Air conditioners in vehicles use the evaporation and
condensation process. The system contains a liquid with a low
boiling point, called the refrigerant. |
| The refrigerant used is tetrafluoroethane R134a, which boils
at -26.5°C with vapour pressure of 1 bar. |
|
| Physical data of refrigerant R134a |
|
|
|
| Chemical formula |
CH2F–CF3 or CF3–CH2F |
| Chemical designation |
Tetrafluoroethane |
| Boiling point at 1 bar |
-26.5°C |
| Freezing point |
-101.6°C |
| Critical temperature |
100.6°C |
| Critical pressure |
40.56 bar (technical) pressure
equates to 39.5 bar (standard) pressure |
| Critical point (critical temperature and critical pressure)
means the point above which there is no longer a surface of
separation between liquid and gas. |
| Above its critical point, a substance is always gaseous. |
| At temperatures below the critical point, all types of
refrigerant contained within a pressure tank exhibit a liquid
phase and a gas phase, so that there is a gas cushion above the
liquid. |
| As long as there is gas in the pressure vessel alongside the
liquid, the pressure depends directly on the ambient temperature
→ Chapter. |
 Note
| Different types of refrigerants must not be mixed with each
other. Only refrigerants specified for the respective air
conditioning system may be used. |
|
|
|
| Environmental aspects of refrigerant
R134a |
| R134a is a fluorocarbon and contains no chlorine. |
| R134a has a shorter atmospheric persistence than refrigerant
R12. |
| R134a does not damage the ozone layer, the potential to
reduce the amount of ozone is zero. |
| The Global Warming Potential (GWP) of R134a lies by
approx. 1430 (the GWP for carbon dioxide lies by 1). |
| The contribution of R134a to the greenhouse effect is less
by a factor of 10 than that of refrigerant R12. |
|
|
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The vapour pressure table for each refrigerant is published
in the literature for refrigeration engineers. This table shows
the vapour pressure exerted on the liquid ...
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Note
...
Handling pressure tanks
Secure vessels against falling over!
Secure standing cylinders against falling over and lying
cylinders from rolling away.
Do not throw pressure vessels!
When falling, the containers may become sev ...
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Vapour pressure table for refrigerant R134a