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Tuesday, 10 December 2013

The Most Commonly Used Refrigerants

The Most Commonly Used Refrigerants Points : The Most Commonly Used Refrigerants, Refrigerant, Refrigrant-22, Ammonia The following are the most commonly used refrigerants.
R 12 = Dichiorodifluro methan
R.22 = MonoChiorodifluro methan
R-717 = Ammonia
R-764 = Sulpher dioxide
R-729 = Air
a) Refrigerant-12 R-12 is a very popular refrigerant. It is colorless, almost odorless liquid with a boiling point of 12.7F° (-29°C) at atmospheric pressure. It is nontoxic, non-corrosive, non-irritating and non-flammable. It is used in reciprocating, rotary and large centrifugal compressors. At present time, all small units (Refrigerators etc.) required for domestic applications, use refrigerant-12 (under (lie trade name ‘Freon’12) as a refrigerant. The cylinder code color is white. b) Refrigrant-22 R-22 is a man-made refrigerant developed for. refrigeration installations that need a low evaporating temperature. One application is in fast freezing unit which maintain a temperature of -20°F to -40°F(-29 to -40°C). It has also been successfully used in air conditioning units and in house hold refrigerators. It is used with both reciprocating and centrifugal compressors.
R-22 has a boiling point of -41°F (-41°C) at atmospheric pressure. It is stable and is nontoxic, non corrosive, nonirritating and nonflammable. The evaporator pressure of R-22 is 43 psi or 28 psi (1.96KgIcmn2), at 5°F. The cylinder code color is green. The principal advantage of Refrigerant-22 over Refrigerant- 12 is the smaller compressor displacement required. It is about 60% less than required for Refrigerant- 12 which means that refrigerant-22 has a refrigerating capacity 60% more than that of Refrigerant-12 for a given compressor displacement. The cylinder code color is green.
c) Ammonia Although ammonia is toxic, slightly explosive and flammable under certain conditions yet it is extensively used’ in ice plants, packing plants, large cold storage etc. due to its excellent thermal properties. it has the highest refrigerating effect per Kg of any refrigerant. The common metals which are used in Ammonia systems are iron & steel. It should never be used with copper, bars and other copper alloys. It is a colorless gas. Its boiling temperature at atmospheric pressure is -28°F (33°C) and its melting point from the solid is 108°F(-78°C). For making leak detection in ammonia systems usually sulpher candle is used which gives off a dense white smoke in the presence of ammonia vapour. The cylinder cod color is silver.

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