Azeotropics:  The azeotropic mixtures
are usually binary mixtures in which the composition of mixture does not change
with respect to  temperature. however
for standard azeotropic mixtures, the
composition change is small.  For example refrigerant R502 is a mixture of
R22 and R152a.

Zeotropics: Zeotropic mixtures are also called as Non-Azeotropic Refrigerant
mixtures  in which composition of mixture
changes with respect to  temperature. These
type of refrigerants can be used in applications where the external heat source
and sink temperature varies. For example zeotropic refrigerant mixture is R407c, is a mixture of  R32 , R125 and R134a.

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From the refrigerant mixtures we can control the
toxicity, flammability,  with
the help of different compositions. But due to leakage the composition of
zeotropics can change we should require to take at most care.

 

There are different types of synthetic refrigerants like :

·        
Chlorofluorocarbons(CFCs): These
refrigerants contain chlorine, Fluorine, Carbon as its constituents. These
refrigerants are ideal that they did not react with other materials, non-toxic,
and non-reactive. But later discovered that the chlorine present in refrigerant
act as a catalyst for ozone depletion, which chlorine atom depletes the oxygen
molecule from the ozone which is not a environment safety. so Montreal protocol
has 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 its
constituents. These are eco friendly refrigerants having just 10% of ozone
depletion level. They are cost effective, Less toxic. But these HCFCs are responsible
for climate change, and global warming so Montreal protocol has prohibited the
usage 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 than
HCFCs but they are having considerable amount of ozone depleting elements.
However R134a from the HFC family is now using in wide range of applications
because of its low global warming potential and ozone depletion level. These
refrigerants are also having less toxicity and energy efficient. Examples of
HFCs 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 to
the Montreal protocol, the ODP of refrigerants should be zero.

·        
Global Warming
Potential (GWP):
Refrigerants
should have as low a GWP value as possible to minimize the problem of global
warming.

 

 

There are also other factors that
we have to look while selecting the refrigerant

·        
Toxicity: When the concentration
of refrigerants is high, it will lead to suffocation. HFCs and CFCs are non
toxic in nature when mixed up with air. But when they came in to contact with
heating element they decompose and forms high toxic gases.

·        
Flammability: When any
vehicle met with an accident the refrigerant should not to be flammable and explosive.

·        
Chemical
stability: The refrigerant should have chemical stability when they are using as a
working fluid in the refrigeration system

·        
Ease of leak
detection: If there is any leakage in the system, it should be  easily identified.

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