Refrigerants

http://en.wikipedia.org/wiki/List_of_refrigerants

http://en.wikipedia.org/wiki/Refrigerant

http://www.engineeringtoolbox.com/refrigerants-designations-d_903.html

Among the commonly used CFCs, dichlorodifluoromethane (CFC-12) is one of the most widely used refrigerants in various applications such as Domestic Refrigerators, Bottle, Coolers, Deep Freezers, Water Coolers, and Mobile Air Conditioners etc. The excellent characteristics of CFC – 12 have lead to the development of highly efficient and reliable compressors and other refrigeration system components. Studies have shown that these refrigeration appliances give satisfactory performances for approximately 15 to 20 years. This high degree of reliability has caused the consumers to expect long services from these appliances in general. Same is for HCFC22. It is mostly used in air-conditioning applications. Table shows a brief history of development of CFC refrigerants.

Development of Refrigerants.

The ozone layer consists of ozone present at very low concentration in the stratosphere between 12 to 30 km up in altitude. Ozone is a gas formed naturally in the stratosphere by the action of sunlight on oxygen. Ozone is also converted back to oxygen by several natural processes. Two of the processes, which can convert ozone back to oxygen, involve nitrogen oxides and chlorine. Therefore the observed amount of ozone present in stratosphere at any time is the net result of a competing process of formation and destruction. This layer prevents harmful ultra-violet radiation from reaching the earth. In small doses ultra violet radiation is beneficial as it contributes to vitamin D formation in the body; but in large doses it can causes fatal diseases such as skin cancer. A hole was detected in the ozone layer for the first time in 1956. IT is found that CFCs on emission contribute to depletion of ozone.In 1987, twenty-four countries including the USA, Japan, the then Soviet Union and European countries signed Montreal Protocol to regulate the Ozone Depleting Substances (ODS). Many countries including developing countries banned the CFCS and HCFCs days are also numbered. Throughout the world research is going on alternative refrigerants to CFCS for the last three decades but so far there are no refrigerants which exactly replace the CFCS. R407 is a mixture. You can check the DuPont web site for more details.