The U.S. Environmental Protection Agency and other world scientific bodies have determined that refrigerants comprising chlorofluorocarbons (CFCs) cause harm to the Earth's stratospheric ozone layer after being released into the atmosphere. Hydrochlorofluorocarbons (HCFCs), which are chlorofluorocarbons containing one or more hydrogen atoms, also cause damage to the ozone layer but such damage is generally less than that caused by CFCs. Various rules, regulations, protocols and treaties in the world have phased out CFCs, or are now doing so. HCFCs are being allowed as “transition” substances between CFCs and various zero ozone depletion alternatives. HCFCs are also under phase outs, but on a much longer time scale than the CFCs, with the final HCFC phase-out being in the year 2030. Certain countries may phase out HCFCs earlier than 2030, and certain categories of use (e.g., production of new equipment containing HCFCs) may be phased out earlier, as well, while other categories of use (service fluids for repair of existing equipment) may be maintained until 2030.
Several non-ozone depleting refrigerants have already been developed in the prior art. However, most of them have one or more drawbacks. The main drawback is that refrigerants comprised of hydrofluorocarbons (HFCs), or mixtures thereof, do not mix (are not miscible in) mineral oils used for the earlier CFC and HCFC refrigerants (e.g., CFC-12 and HCFC-22, R-502, R-500). R-407C, comprising R-32/125/134a (23/25/52), closely matches the pressure temperature curve of HCFC-22. However, it requires ester (POE) oil and is totally non-miscible in mineral oil. Ester oils are far more expensive and are less stable than mineral oils. Ester oils also are far more hygroscopic than mineral oils, so moisture can enter a refrigeration system much easier during manufacture or service than it can with mineral oils. This moisture is extremely damaging, and causes the refrigerants to slowly hydrolyze and decompose into hydrofluoric acid (HF) and other components leading to early system failures.
This disclosure relates generally to novel refrigerant blends that can be used to replace chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants. More particularly, the disclosure relates to novel refrigerant blends that can be used to replace R-22 (chlorodifluoromethane) in refrigeration systems designed to use R-22 as the refrigerating fluid.
Refrigeration systems have been in widespread use for decades and have a wide variety of uses, such as comfort cooling, household refrigeration, automobile air conditioning, commercial freezer cooling. Such systems work on the basic premise that a fluid, known as a refrigerant, picks up heat from an area to be refrigerated, and disposes of the heat in an area not adversely affected by an increase in heat. Typically, refrigeration processes encompass a changing state of the refrigerant fluid from a liquid to a vapor, and from a vapor to a liquid, which change of state allows for the rapid removal of heat from the area to be refrigerated. Different types of refrigeration systems use different refrigerants having properties designed to enable the given system to approach peak performance.
Chlorofluorocarbon refrigerants such as R-12 (dichlorodifluoromethane) were the refrigerants of choice for many years in domestic and commercial refrigeration, as well as in automobile air conditioners. However, in view of the recognition in the scientific community that these chlorine-containing refrigerants have an adverse effect on the earth's ozone layer, international agreements have mandated a phase-out of these refrigerants in favor of more environmentally friendly refrigerants. Hydrochlorofluorocarbon refrigerants such as R-22, while believed to be less environmentally problematic than CFCs, are also chlorine-containing, and have likewise raised concerns in the scientific community. International agreements have called for a gradual phase-out of HCFC refrigerants.
Numerous low ozone-depleting refrigerants have been promoted as replacement refrigerants. A widely used replacement refrigerant has been R-134a (1,1,1,2tetrafluoroethane). R-134a contains no chlorine atoms, and is non-ozone-depleting, nonflammable and non-toxic. However, the use of R-134a necessitates major changes in most refrigeration systems. For example, the mineral oil lubricants typically used with CFC and HCFC refrigerants are not compatible with R-134a. As a result, it is necessary to completely drain this oil from systems previously using CFC and HCFC refrigerants, and replaces it with other lubricants that are more compatible with R-134a, such as polyolester (POE) and polyalkylene glycol (PAG) lubricants. In addition, some equipment used in existing air conditioning systems is not compatible with R-134a, thus necessitating significant overhaul and replacement of portions of these air conditioning systems
When new products are designed and/or put into service, such products can be engineered for use with new refrigerants such as R-134a. Thus, such products can be manufactured with components that are compatible with R-134a, and can be produced for use with compatible lubricating oils. However, the situation is more problematic when existing refrigeration systems require replacement refrigerant. Replacements are often required when, for example, existing refrigerant is leaked or evaporated from the system. Replacement refrigerant also must be periodically added to such systems during routine maintenance of the system. In existing refrigeration systems, it is often cost prohibitive to retrofit the system to be compatible with non-CFC or non-HCFC refrigerants such as R-134a. In addition, in small systems it is often inconvenient and uneconomical to completely drain the existing lubricant and replace it with lubricating oil that is more compatible with a replacement refrigerant.
Several refrigerant compositions that are intended to replace R-22 are commercially available. The three best known replacement refrigerants are R-407C (a combination of R-134a, R-125, and R-32), R-410A (a binary blend of R-125 and R-32) and R-417A (a blend of R-125, R-134a, and R-600). R-410A is a high pressure refrigerant that cannot be used in existing R-22 equipment. As a result, the existing refrigeration equipment must be replaced when this refrigerant is used. R-407C can be used in existing R-22 systems; however, this refrigerant is not compatible with the mineral oil lubricants used in such systems. As a result, the system must be flushed, and the lubricant must be replaced with one that is compatible. R-417 A can be used in existing R-22 systems with existing oils. However, this refrigerant shows a decrease in refrigerating capacity about 5 to 15 percent when compared to R-22.
Thus, there is a long-felt but unresolved need for replacing a R-22 refrigerant with a new refrigerant, without the necessity of draining the existing lubricant and/or overhauling the existing refrigeration equipment to make it compatible with the new refrigerant. Preferably, the replacement refrigerant would be low cost, have low flammability and toxicity, have refrigerating capacity similar to the existing refrigerant, be compatible with the existing system and lubricant, and have the ability to substantially resist fractionation into flammable components upon evaporation or leakage from the refrigeration system.