Working fluids comprising fluorinated olefins/fluorinated saturated hydrocarbon blends and polyol esters

1. A working fluid comprising:

i) a refrigerant blend comprising from 80 to 60% by weight, based on the weight of the refrigerant blend, of fluorinated alkane, from 20 to 40% by weight of a fluorinated olefin, and less than 5 wt % of other refrigerants are present, and

ii) a polyol ester lubricant composition having a kinematic viscosity at 40° C. of from 32 to 120 cSt and a kinematic viscosity at 100° C. of from 5 to 20 cSt, comprising:

a) from about 30 to about 85 wt % C 5-10 alkylcarboxy esters of pentaerythritol,

b) from about 1 to about 20 wt % C 5-10 alkylcarboxy esters of di-pentaerythritol,

c) from about 1 to about 10 wt % C 5-10 alkylcarboxy esters of tri-pentaerythritol, and

d) from about 10 to about 45 wt % C 5-10 alkylcarboxy esters of pentaerythritol oligomers of 4 or more pentaerythritol monomer groups, based on the weight of all polyol esters in the lubricant, and wherein 60 mole % or more of all the C 5-10 alkylcarboxy esters are linear or branched C 5 alkylcarboxy esters, and 25 to 55% of the C 5-10 alkylcarboxy esters are branched.

2. The working fluid according to claim 1 wherein the polyol ester lubricant composition has a kinematic viscosity at 40° C. of from 40 to 140 cSt.

3. The working fluid according to claim 1 wherein the polyol ester lubricant composition comprises:

a) from about 30 to about 55 wt % C 5-10 alkylcarboxy esters of pentaerythritol,

b) from about 1 to about 20 wt % C 5-10 alkylcarboxy esters of di-pentaerythritol,

c) from about 1 to about 10 wt % C 5-10 alkylcarboxy esters of tri pentaerythritol, and

d) from about 25 to about 45 wt % C 5-10 alkylcarboxy esters of pentaerythritol oligomers of 4 or more pentaerythritol monomer groups.

4. The working fluid according to claim 1 wherein 75 mol % or more of all alkylcarboxy esters are linear or branched C 5 alkylcarboxy esters.

5. The working fluid according to claim 1 wherein 30 to 50 of the C 5-10 alkylcarboxy esters are branched.

6. The working fluid according to claim 1 wherein the refrigerant blend comprises from 70 to 75% by weight of fluorinated alkane and from 25 to 30% by weight of a fluorinated olefin hydrofluorocarbon refrigerant.

7. The working fluid according to claim 1 wherein the refrigerant blend comprises a hydrofluoro alkane and a hydrofluoro olefin, which a hydrofluoro olefin has 3, 4 or 5 carbon atoms.

8. The working fluid according to claim 7 wherein the hydrofluoro alkane comprises difluoromethane (R-32), 1,1,1,2-tetrafluoroethane (R-134a), 1,1,2,2-tetrafluoroethane (R-134), pentafluoroethane (R-125), or 1,1,1-trifluoroethane (R-143a).

9. The working fluid according to claim 8 wherein the hydrofluoro olefin comprises a polyfluorinated propene.

10. The working fluid according to claim 7 wherein the hydrofluoro olefin comprises a polyfluorinated propene.

11. The working fluid according to claim 1 wherein the refrigerant consists of a mixture of the fluorinated-olefin and the fluorinated alkane.