Refrigeration – Processes – Lubricant handling
Reexamination Certificate
2000-09-27
2003-03-04
Doerrler, William (Department: 3744)
Refrigeration
Processes
Lubricant handling
C062S077000, C062S114000, C252S068000, C252S067000
Reexamination Certificate
active
06526764
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to compositions for use as refrigerants, aerosol propellants, heat transfer media, gaseous dielectrics, fire-extinguishing agents, foam blowing agents and solvents. More particularly, the invention relates to hydrofluorocarbon refrigerant compositions that are soluble in lubricating oil.
BACKGROUND OF THE INVENTION
Fluorocarbon based fluids have found widespread use in industry for refrigeration, air conditioning and heat pump applications.
Vapor compression cycles are one common form of refrigeration. In its simplest form, the vapor compression cycle involves changing the refrigerant from the liquid to the vapor phase through heat absorption at a low pressure, and then from the vapor to the liquid phase through heat removal at an elevated pressure.
While the primary purpose of refrigeration is to remove energy at low temperature, the primary purpose of a heat pump is to add energy at higher temperature. Heat pumps are considered reverse cycle systems because for heating, the operation of the condenser is inter-changed with that of the refrigeration evaporator.
The art is continually seeking new fluorocarbon based fluids, which offer alternatives for refrigeration and heat pump applications. Currently, of particular interest, are fluorocarbon-based mixtures, which are considered to be environmentally acceptable substitutes for the presently used chlorofluorocarbons. The latter, such as monochlorodifluoromethane (R-22) are suspected of causing environmental problems in connection with the earth's protective ozone layer.
The substitute materials must also possess those properties unique to the chlorofluorocarbons including similar refrigeration characteristics, chemical stability, low toxicity, non-flammability, efficiency in-use and low temperature glides.
By “similar refrigeration characteristics” is meant a vapor pressure that is plus or minus 20 percent of the reference refrigerant at the same temperature.
The characteristic of efficiency in-use is important, for example, in air conditioning and refrigeration where a loss in refrigerant thermodynamic performance or energy efficiency may have secondary environmental impacts through increased fossil fuel usage arising from an increased demand for electrical energy.
Alternative hydrofluorocarbon refrigerants are known. R-507 is an azeotrope-like blend of pentafluoroethane (R-125) and 1,1,1-trifluoroethane (R-143a). R-404A is a non-azeotropic blend of R-125, R-143a and 1,1,1,2-tetrafluoroethane (R-134a). R-407 is a non-azeotropic blend of difluoromethane (R-32), R-125 and R-134a. These alternative refrigerants are available commercially from various sources including Honeywell, DuPont, Atochem and ICI.
R-407C serves as a non-ozone-depleting replacement for R-22 in various air-conditioning applications, as well as in most refrigeration systems including chillers. Since R-407C is a close match to R-22 it also serves as a retrofit fluid in applications where R-22 is generally used.
The widespread commercial use of chlorine-free hydrofluorocarbon refrigerants has been hindered, however, by the lack of commercially adequate lubricants. Mineral oil or alkyl benzenes, which have been used traditionally with R-22, are immiscible with R-407C and must therefore be replaced with expensive polyol ester lubricants. In retrofitting refrigerant systems with hydrofluorocarbon refrigerants it is necessary to drain as much of the oil as possible before adding the replacement lubricant. Often this entails removing the compressor from the system to drain lubricant. A chlorine-free R-22 retrofit fluid that is soluble in lubricating oils would advance the art.
SUMMARY OF THE INVENTION
The invention provides refrigerant compositions that are soluble in lubricating oils and are particularly useful as R-22 retrofit fluids.
The compositions of the invention comprise a refrigerant and a solubilizing agent. Preferably the refrigerant is a hydrofluorocarbon refrigerant. Optionally, the compositions of the invention further comprise a lubricating oil selected from the group consisting of mineral or hydrocarbon oil, alkyl benzene oil, white or paraffinic oil and mixtures thereof.
In one embodiment of the invention, there is provided a composition comprising a refrigerant selected from the group consisting of the compounds listed in Table 1 and mixtures thereof and at least one solubilizing agent selected from the group consisting of the compounds listed in Table 2 and mixtures thereof.
In another embodiment, there is provided a composition comprising (i) from about 80 to about 99.9 weight percent, preferably from about 90 to about 99.9 weight percent, of a refrigerant selected from the compounds listed in Table 1 and mixtures thereof; and (ii) from about 20 to about 0.1 weight percent, preferably from about 10 to about 0.1 weight percent, of a solubilizing agent selected from the compounds listed in Table II and mixtures thereof.
In yet another embodiment of the invention, there is provided a composition comprising (i) from about 80 to about 99.9 weight percent, preferably from about 90 to about 99.9 weight percent, of a refrigerant selected from Table III; and (ii) from about 20 to about 0.1 weight percent, preferably from about 10 to about 0.1 weight percent, of a solubilizing agent selected from the compounds listed in Table II and mixtures thereof.
In still another preferred embodiment, there is provided a composition comprising (i) from about 80 to about 99.9 weight percent, preferably from about 90 to about 99.9 weight percent, of a refrigerant selected from Table IV; and (ii) from about 20 to about 0.1 weight percent, preferably from about 10 to about 0.1 weight percent, of a solubilizing agent selected from the compounds listed in Table II and mixtures thereof.
In a particularly preferred embodiment, there is provided a composition comprising (i) from about 80 to about 99.9 weight percent, preferably from about 90 to about 99.9 weight percent, of a refrigerant selected from the group consisting of R-407C, R-410A, R-404A and R-507A; and (ii) from about 20 to about 0.1 weight percent, preferably from about 10 to about 0.1 weight percent, of a solubilizing agent selected from the group consisting of butane, isobutane, pentane, dimethyl ether, and mixtures thereof.
When a lubricating oil is present, it is present in an amount of from about 1 to about 60 weight percent, preferably from about 10 to about 50 weight percent, based on the total composition.
In a process embodiment, there is provided a method for producing refrigeration which comprises condensing a composition of the invention and thereafter evaporating the composition in the vicinity of a body to be cooled.
In another process embodiment, there is provided a method for producing heating which comprises condensing a composition of the invention in the vicinity of a body to be heated and thereafter evaporating the composition.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The refrigerant may comprise any one of the compounds listed in Table I or mixtures thereof. Hydrofluorocarbon refrigerants are preferred. The term hydrofluorocarbon refers to compounds composed solely of carbon, hydrogen and fluorine atoms. Of the hydrofluorocarbon refrigerants listed in Table I, R-32, R-143a, R-125, R-134a and mixtures thereof are preferred.
Refrigerant mixtures are preferred. Representative refrigerant mixtures are listed in Table III. Hydrofluorocarbon refrigerant mixtures are preferred. Of the hydrofluorocarbon refrigerant mixtures listed in Table III, R-404A, R-407C, R-410A and R-507A are preferred. Hydrofluorocarbon refrigerant mixtures selected from Table IV are also preferred.
As used herein, the term solubilizing agent refers to a compound that increases the solubility of a hydrofluorocarbon refrigerant and a lubricating oil in one another. It will be understood that the solubilizing agent may comprise any one of the compounds listed in Table II or mixtures thereof. Butane, isobutane, pentane and dimethyl ether are preferred
Richard Robert Gerard
Singh Rajiv Ratna
Thomas Raymond Hilton Percival
Wilson David Paul
Doerrler William
Honeywell International , Inc.
Shulman Mark
Szuch Colleen D.
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