Refrigeration, CFCs

The refrigerant CFC-12 has traditionally been used in medium (—15°C) to high (15°C) temperature refrigeration, while HCFC-22 has been used for temperatures down to —35°C, and R-502 down to —45°C. These three refrigerants represented 79, 2, and 19% of the refrigerants used for this appHcation, respectively, in the years 1975—1995 (10). 

Refrigerants CFC-12 (CF2CI2) MFC-134a (CF3CFH2) HCFC-22 (CHF2CI)... 

Randles, S.I., Taylor, P.I., Corr, S., Dekleva, T. and Stewart, A. (1994) Development and Experience with Polyol Ester Lubricants for Use with RI34a Domestic Refrigerators. CFC Halocarbon Conference. 

At the time, they seemed to be ideal coolants for refrigerators. By 1935, the first self-contained home air-conditioning units and eight million new refrigerators in the United States used CFCs as coolants. In addition to their use as refrigerants, CFCs were also used in plastic foams and as propellants in spray cans. 

Uses Refrigerant CFC-12 replacement as diluent in sterilizing gas CFC-11 and -12 replacement in rigid foam insulation applies. Trade Name Synonyms Genetron 124 [Honeywell Spec. Chems. http //WWW. honeywell. com, http //WWW. specialtychem. com] 2-Chloro-1,1,1,2-tetrafluoroethane CAS 2837-89-0 Synonyms Freon 124 R124 Empirical C2HCIF4 Properties M.w. 136.48 Uses Refrigerant... 

Although the initial focus was on CFCs, used at the time for aerosol propellants (CFC-11 and -12), blowing agents (CFC-114), cleaners for electronics (CFC-113) and refrigerants (CFC-115), amendments to the Montreal Protocol have led to the control of such common solvents as carbon tetrachloride and 1,1,1-tri-chloroethane, which were used in very large quantities. 

A. Bhadsavle and W. W. Humm, A Utility Approach to Alternative Refrigerants, CFC Refiigerant Alternative Seminar, New Orleans, LA (1993). 

Composed of carbon, hydrogen, fluorine, and chlorine, chlorinated fluorocarbons (CFCs) are all l halides used in aerosol propellents and refrigerants. CFCs have been replaced by other compounds because they generate chlorine atoms in the upper atmosphere, which deplete the ozone layer (see Section 12.15). Many aerosols are now propelled by carbon dioxide. Different refrigerant molecules (called hydrofluorocarbons, HFCs) are being used in refrigerators and air conditioners. 

Most of the halocarbons produced by industry are intermediates for the manufacture of various products. Halocarbons are also used as solvents for dry cleaning and degreasing in the mechanical industry. Much of this production ends up in waste waters. Others, such as chlorofluorocarbons (CFCs) have been used as aerosol propellants which were discharged to the atmosphere on a short time scale. Some halocarbons are slowly leaking to the environment for other reasons, as for example CFC-12 used as heat exchanger in refrigerators. CFC-12 concentrations in the atmosphere therefore are still increasing, while concentrations of many other CFCs decrease as a result of restrictions on production and use. 

Any of several compounds composed of carbon, fluorine, chlorine, and hydrogen used primarily as refrigerants CFCs are thought to be ozone-depleting chemicals. 

Table 17.3. Possible environmentally acceptable refrigerants (CFCs and COifor...

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