TOIL-e
Group A
The heat carrier decomposes (disproportionates) at or below the boiling point at 1 bar. It is mostly the more volatile fractions that are cracked. If the maximum application temperature θmax is exceeded, the properties of the oil undergo permanent change.
Group B
The heat carrier can be used at temperatures above the boiling point, if an inert gas is present to prevent evaporation. Any vapours given off can no longer condense in the form of the original substance. The oil undergoes a lasting change.
Group C
The heat carrier does not undergo any change neither during evaporation nor condensation, the original properties are retained.