Azeotropics: The azeotropic mixturesare usually binary mixtures in which the composition of mixture does not changewith respect to temperature. howeverfor standard azeotropic mixtures, thecomposition change is small. For example refrigerant R502 is a mixture ofR22 and R152a. Zeotropics: Zeotropic mixtures are also called as Non-Azeotropic Refrigerantmixtures in which composition of mixturechanges with respect to temperature. Thesetype of refrigerants can be used in applications where the external heat sourceand sink temperature varies. For example zeotropic refrigerant mixture is R407c, is a mixture of R32 , R125 and R134a.From the refrigerant mixtures we can control thetoxicity, flammability, withthe help of different compositions.
But due to leakage the composition ofzeotropics can change we should require to take at most care. There are different types of synthetic refrigerants like :· Chlorofluorocarbons(CFCs): Theserefrigerants contain chlorine, Fluorine, Carbon as its constituents. Theserefrigerants are ideal that they did not react with other materials, non-toxic,and non-reactive. But later discovered that the chlorine present in refrigerantact as a catalyst for ozone depletion, which chlorine atom depletes the oxygenmolecule from the ozone which is not a environment safety. so Montreal protocolhas prohibited the usage of CFCs. Some of the examples of CFCs are R11, R12,R13, R500, R502, R503.· Hydro chlorofluorocarbons(HCFCs): These are the refrigerants consists of hydrogen, chlorine, Fluorine, Carbon as itsconstituents. These are eco friendly refrigerants having just 10% of ozonedepletion level.
They are cost effective, Less toxic. But these HCFCs are responsiblefor climate change, and global warming so Montreal protocol has prohibited theusage of HCFCs. Examples of HCFCs are R22, R123,R124, R401A,R401B.· Hydroflurocarbons(HFCs): These refrigerants contain Hydrogen, Fluorine,Carbon as its constituents. These are having less global warming potential thanHCFCs but they are having considerable amount of ozone depleting elements.
However R134a from the HFC family is now using in wide range of applicationsbecause of its low global warming potential and ozone depletion level. Theserefrigerants are also having less toxicity and energy efficient. Examples ofHFCs are R134a, R23, R407c, R507. Generally the all refrigerants are characterised by two numbers: · Ozone depletion potential (ODP): Which means reduction in the concentration of ozone in the ozone layer. According tothe Montreal protocol, the ODP of refrigerants should be zero. · Global WarmingPotential (GWP):Refrigerantsshould have as low a GWP value as possible to minimize the problem of globalwarming. There are also other factors thatwe have to look while selecting the refrigerant· Toxicity: When the concentrationof refrigerants is high, it will lead to suffocation.
HFCs and CFCs are nontoxic in nature when mixed up with air. But when they came in to contact withheating element they decompose and forms high toxic gases.· Flammability: When anyvehicle met with an accident the refrigerant should not to be flammable and explosive.· Chemicalstability: The refrigerant should have chemical stability when they are using as aworking fluid in the refrigeration system· Ease of leakdetection: If there is any leakage in the system, it should be easily identified.