Method of improving performance of refrigerant systems

Abstract

A method of improving performance of refrigerant systems such as refrigerators and air conditioners that utilize a refrigerant working fluid. The working fluid consists essentially of a heat transfer fluid and a lubricant that is miscible and is otherwise compatible with the heat transfer fluid at all operating temperatures of the refrigerant system. The method is directed particularly to chlorine-free fluoro-group organic fluids and more particularly to hydrofluorocarbon heat transfer fluids. The preferred lubricants comprise polyol ester basestocks and compounded polyol esters that are highly miscible with such hydrofluorocarbon heat transfer fluids.

What is claimed is:  
     
         1 . A process of improving the performance of a refrigerant system comprising a compressor, condenser, expansion device and evaporator, the process comprising the step of employing in the system a working fluid consisting essentially of a heat transfer fluid and a lubricant that is miscible with the heat transfer fluid over the entire operating conditions of the system.  
     
     
         2 . The process according to    claim 1    wherein the heat transfer fluid is a chlorine-free fluoro-group organic heat transfer fluid.  
     
     
         3 . The process according to    claim 2    wherein the fluoro-group containing heat transfer fluid is a hydrofluorocarbon.  
     
     
         4 . The process according to    claim 3    wherein the lubricant comprises an ester of alcohols that contain at least two —OH groups and a monocarboxylic acid in which at least 22 number percent of the acyl groups in the ester are either straight chain and contain from three to six carbon atoms or have a carbon bonded to three other carbon atoms and contain up to nine carbon atoms.  
     
     
         5 . The process according to    claim 4    wherein the lubricant consists essentially of an ester in which at least 92% of alcohol moieties in the esters of all alcohols containing at least two —OH groups are moieties derived from alcohols selected from the group consisting of pentaerythritol, dipentaerythritol, 2,2-dimethyl-1,3-propanediol, and 2,2dimethyl-1-butanol.  
     
     
         6 . A process of improving the performance of a refrigerant system in which the system undergoes the steps of compression, condensation, expansion and evaporation said process comprising the further step of incorporating in the system a working fluid consisting essentially of a chlorine-free fluoro-group containing heat transfer fluid and a lubricant composition consisting of esters of alcohols containing at least two —OH groups and at least one carboxylic acid.  
     
     
         7 . The process according to    claim 6    wherein the fluoro-group containing heat transfer fluid is selected from the group consisting of difluoromethane, pentafluoroethane, 1,1-difluoroethane, 1,1,1-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, and mixtures thereof.  
     
     
         8 . The process according to    claim 6    wherein the lubricant consists essentially of an ester formed from an alcohol comprising pentaerythritol and dipentaerythritol and an acid mixture in which acyl groups used to from the ester are derived from acyl groups having 5, 6, 7, 8, 9 and 10 carbon atoms.  
     
     
         9 . The process according to    claim 8    wherein at least 98% of the monocarboxylic acids are derived from acyl groups having 5, 7 or 9 carbon atoms.  
     
     
         10 . The process according to    claim 6    wherein at least 98% of the monocarboxylic acids are derived from acyl groups having 5 or 9 carbon atoms.  
     
     
         11 . The process according to    claim 9    wherein at least 98% of the alcohol moieties in the ester are derived from pentaerythritol and dipentaerythritol and the acyl groups used to make the ester are derived from a mixture of about 43 wt. % 3,5,5-trimethylhexanoic acid, about 37 wt. % n-pentanoic acid and about 20 wt. % of a mixture of 2-methylbutanoic acid and 3-methylbutanoic acid.  
     
     
         12 . A process of improving the performance of an air conditioner comprising a compressor, condenser, expansion device and evaporator, the process comprising the step of employing in the system a working fluid consisting essentially of a heat transfer fluid and a lubricant that is miscible with the heat transfer fluid over the entire operating conditions of the systems.  
     
     
         13 . The process according to    claim 12    wherein the heat transfer fluid is a hydrofluorocarbon and the lubricant is an ester formed from an alcohol comprising pentaerythritol and dipentaerythritol and an acid mixture derived from acyl groups having 5, 6, 7, 8, 9 and 10 carbon atoms.  
     
     
         14 . The process according to    claim 13    wherein the hydrofluorocarbon heat transfer fluid is selected from the group consisting of difluoromethane, pentafluoroethane, 1,1,-difluoroethane, 1,1,1,-trifluoroethane, 1,1,1,2-tetrafluoroethane and mixtures thereof.  
     
     
         15 . The process according to    claim 13    wherein the ester lubricant is formed from a carboxylic acid mixture in which at least 22 no % of the acyl groups in the acid mixture are selected from the group consisting of straight chain acid of three to six carbon atoms, an acid containing up to nine carbon atoms in which at least one carbon atom is bonded to three other carbon atoms and mixtures thereof.  
     
     
         16 . The process according to    claim 13    wherein the ester includes up to 8 percent by weight of at least one additive.  
     
     
         17 . A process of improving the performance of a refrigerator comprising a compressor, condenser, expansion device and evaporator, the process comprising the step of employing in the system a working fluid consisting essentially of a heat transfer fluid and a lubricant that is miscible with the heat transfer fluid between −27° C. and +30° C.  
     
     
         18 . The process according to    claim 17    wherein the heat transfer fluid is selected from the group consisting of difluoroethane, pentafluoroethane, 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane and mixtures thereof.  
     
     
         19 . The process according to    claim 17    wherein the lubricant is an ester formed from an alcohol comprising pentaerythritol and dipentaerythritol and an acid mixture in which the acyl groups used to form the ester are derived from acyl groups having 5, 6, 7, 8, 9 and 10 carbon atoms.  
     
     
         20 . A process according to    claim 17    wherein the heat transfer fluid is 1,1,1,2-tetrafluoroethane and the lubricant consists of an ester formed from an alcohol selected from the group consisting of pentaerythritol, dipentaerythritol, tripentaerythritol and mixtures thereof and an acid consisting of about 43 wt % 3,5,5-trimethylhexanoic acid, about 37 wt % n-pentanoic acid and about 20 wt % of a mixture of 2-methylbutanoic acid and 3-methylbutanoic acid.