CFCs, global warming potential

Ozone Depletion Potential. This is calculated in a similar manner to global warming potential and is expressed relative to CFC-11. Factors for all common gases having significant effects on the ozone layer have been calculated. 

TABLE 14.7 Direct Radiative Forcings per Unit Concentration for Some Fluorinated Compounds0 and Relative Global Warming Potentials Taking GWP(CFC-11) = 1.0b,c or GWP (C02) = 1.0... 

TABLE 2. Atmospheric lifetime, ozone depletion potential (ODP) and global warming potential (GWP) of CFCs, HCFCs, HFCs and halons... 

Hydrofluorocarbons (HFCs), including 1,1,1,2-tetrafluoroethane (HFC-134a), have been developed as alternatives to chlorofluorocarbons (CFCs), which are known to contribute to the breakdown of ozone to oxygen in the stratosphere. HFCs do not contribute to the destruction of stratospheric ozone, but some HFCs have global warming potential. They primarily serve as replacements for CFCs in refrig... 

An ideal CFC substitute is one that offers identical performance properties of the CFC it replaces with the added stipulation that it does not destroy the ozone layer and has low global warming potential. Low toxicity, a property of CFCs, and shorter atmospheric lifetimes compared to CFCs are also preferred. Summarized, the desired characteristics include short atmospheric lifetimes, low toxicity, ozone compatibility, low global warming potential, thermal and chemical stability, equivalent physical properties, and amenability to realistic processes. 

One technical approach to solve this environmental problem is to eliminate the chlorine content of CFCs, primarily by replacing any chlorine atoms with fluorine atoms in these molecules. Hydrochlorofluorocarbons (HCFC s) do not have inqtact zero on the ozone layer and although they have been used in this period, they are already currently subject to restrictions and will be proscribed fi-om 2025. Hydrofluorocarbons (HFC s) have ODP (Ozone Depletion Potential) equal to zero and low GWP (Global Warming Potential) and they are therefore designated as substitutes to CFCs in the field of refijgeration [3]. 

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