FIELD: chemistry.
SUBSTANCE: present invention refers to a process fluid for a heat exchanging unit containing i) CO2, as a refrigerant, and ii) a lubricant composition of polyol esters having a viscosity ratio of 130 or higher, containing a mixture of esters of formula 
I, wherein n represents an integer from 1 to 20; each R independently represents alkylcarbonyl with 3-12 carbon atoms; each R1 is specified independently and represents either group R, or a substitute of formula 
II, and wherein at least 50% of all groups R in the compounds of formula I found in the process fluid represent n-pentanoyl, and wherein the lumbicant composition of polyol esters ii) contains: a) from 20 to 45 wt % of the compounds of formula I, wherein n is equal to 1 and each R1 is specified independently and represents a group R, b) from 15 to 20 wt % of the compounds of formula I, wherein n is equal to 2 and each R1 is specified independently and represents the group R, c) from 10 to 15 wt % of the compounds of formula I, wherein n is equal to 3 and each R1 is specified independently and represents the group R, and d) from 30 to 55 wt % of the compositions of formula I, which represent pentaerythritol oligomers of 4 or more monomer groups of pentaerythritol.
EFFECT: technical effect of the present invention is producing the process fluid containing the lubricant of polyol esters providing the excellent viscosity and lubricating property together with the unexpectedly excellent mixability with the CO2 refrigerant.
7 cl, 5 tbl, 7 ex
