METHOD OF SELECTING REFRIGERANT-LUBRICANT COMBINATIONS

Abstract

The present invention provides methods for selecting refrigerant and lubricant combinations for use in heat transfer cycle systems and provides methods for operating said heat transfer system. More particularly, the invention provides methods to select lubricant and refrigerant combinations for a heat transfer cycle system wherein at the lower temperatures of the heat transfer cycle the refrigerant and lubricant are miscible and at the upper temperatures of the heat transfer cycle the refrigerant and lubricant are phase separated and such that the density phase inversion temperature of the combination is below the upper operating temperature of the heat transfer cycle.

Claims

1. A method of operating a vapor-compression heat transfer system containing a refrigerant and a lubricant combination comprising: a. determining a lower, evaporator discharge operating temperature range of a vapor-compression heat transfer system; b. determining an upper, compressor discharge operating temperature range of the vapor-compression heat transfer system; and c. wherein said refrigerant is selected from hydrofluorocarbons (HFCs), hydrofluoroolefis (HFOs), hydrochlorofluorocarbos (HCFCs), hydrochlorofluoroolefins (HCFOs), hydrocarbons (HCs), carbon dioxide, ammonia, dimethyl ether, or mixtures thereof at a first concentration and said lubricant is selected from polyalkylene glycols (PAGs), polyol esters (POEs), polyvinyl ethers (PVEs), polyglycols, polyalkylene glycol esters, alkyl benzenes, mineral oils, polyalphaolefins, or mixtures thereof at a second concentration and wherein said refrigerant and said lubricant are miscible at a first temperature within said lower, evaporator discharge operating temperature range and produce a fluid system having a refrigerant-rich phase and a lubricant-rich phase at a second temperature within said upper, compressor discharge operating temperature range provided that said second temperature is higher than said first temperature, wherein the lubricant-rich phase has a higher density than the refrigerant-rich phase at said second temperature and wherein the phase inversion temperature is between the lower, evaporator discharge operating temperature and the upper, compressor discharge operating temperature.

2. The method of claim 1 wherein the hydrofluoroolefin is selected from the group consisting of C3 to C6 alkenes.

3. The method of claim 2 wherein said C3 to C6 alkene is selected from the group consisting of trifluoropropene, tetrafluoropropene, pentafluoropropene and mixtures thereof.

4. The method of claim 3 wherein said trifluoropropene, tetrafluoropropene is selected from the group consisting of 3,3,3-trifluoropropene (HFO-1243zf), 2,3,3,3-tetrafluoropropene (HFO-1234yf) and 1,3,3,3-tetrafluoropropene (HFO-1234ze).

5. The method of claim 1 wherein said higher operating temperature range is about +15 C. to about +90 C. and said lower operating temperature range is about 60 C. to about +25 C.

6. The method of claim 1 wherein said higher operating temperature range is about +30 C. to about +70 C. and said lower operating temperature range is about 30 C. to about +15 C.

7. The method of claim 1 wherein said fluid system further comprises one or more of additives selected from the group consisting of dyes, viscosity modifiers, anti-foaming agents, corrosion inhibitors, stabilizers, compatibilizers, anti-oxidants, pour point depressants, nanoparticles, flame suppressants and mixtures thereof

Description

EXAMPLE 1

[0016] To a graduated pressure vessel was added approximately equal parts of HFO-1234yf and a commercial PAG lubricant (Castrol PAG 46). The components were mixed and allowed to sit at ambient temperature to equilbrate. At ambient temperature (20 C.), the mixture was phase separated, with a lubricant-rich liquid phase floating on a refrigerant-rich liquid phase. To reduce the temperature of the mixture below ambient, the pressure vessel was placed in a contain temperature refrigerator or freezer and cooled until equilibrium was reached. At 8 C. the mixture was miscible, showing only a single liquid phase. At 20 C. the mixture was miscible with only a single liquid phase,

[0017] To raise the temperature of the mixture above ambient, the graduated pressure vessel was then placed in a constant temperature bath and heated in stages to from 25 C. to 50 C., allowed to reach equilibrium at each stage, and the vessel contents were periodically observed. The mixture contained two liquid phases. At 30 C. the two phases were very difficult to distinguish. At 35 C., the two phases were still difficult to distinguish but a liquid, refrigerant-rich phase was floating above a more lubricant-rich phase. At 40 C. and higher, the portion of the sample that was the refrigerant-rich phase had increased and the two phases were more easily distinguished.

[0018] The graduated pressure vessel was removed from the contant temperature bath and allowed to cool. As the vessel cooled, the refrigerant-rich phase was observed to sink to the bottom of the vessel.

[0019] This example shows that the combination of HFO-1234yf with Castrol PAG 46 is miscible from 8 C. to 20 C. while being immiscible at +20 C. and above, with a density phase inversion temperature of about +30 C.

EXAMPLE 2

[0020] A vapor-compression air conditioning system can be operated using the refrigerant/lubricant combination of Example 1, where the refrigerant is HFO-1234yf and the lubricant is Castrol PAG 46, The lower operating temperature range could be from about +8 C. to about 20 C., while the upper operating temperature range could be from about 30 C. and above. The air conditioning system would be operated according to the present invention, where the evaporator temperature is maintained at 4 C.+/2 C., and the condensing temperature is maintained at about 40 C. Using these operating conditions, the refrigerant and lubricant would be miscible at the coldest conditions in the air conditioning system while at the upper operating temperatures, the refrigerant and lubricant would be immiscible but where the refrigerant-rich phase is less dense.