Refrigerant type – Detailed Classification Of Refrigerant
INTRODUCTION TO REFRIGERANT :
The working agent in a refrigerating system that absorbs carries or releases heat from the place to be cooled or refrigerated can be termed as a refrigerant. This heat transfer generally takes place through a phase change of the refrigerant.
A more complete definition of a refrigerant could be given as follows:
“Refrigerant is the fluid used for heat transfer in a refrigerating system that absorbs heat during evaporation from the region of low temperature and pressure, and releases heat during condensation at a region of higher temperature and pressure.”
Refrigerant types :
Refrigerants can be broadly classified based on the following:
1. Working Principle
Under this heading, we have the primary or common refrigerants and the secondary refrigerants.
The primary refrigerants are those that pass through the processes of compression, cooling or condensation, expansion and evaporation or warming up during cyclic processes. Ammonia, R12, R22, carbon dioxide come under this class of refrigerants.
On the other hand, the medium which does not go through the cyclic processes in a refrigeration system and is only used as a medium for heat transfer are referred to as secondary refrigerants. Water, brine solutions of sodium chloride and calcium chloride come under this category.
2. Safety Considerations
Under this heading, we have the following three sub-divisions.
These are the non-toxic, non-flammable refrigerants such as R11, R12, R13, R14, R21, R22, R113, R114, methyl chloride, carbon dioxide, water etc.
Toxic and moderately flammable
Dichloroethylene methyl format, ethylchloride, sulphur dioxide, ammonia etc. come under this category.
Highly flammable refrigerants
The refrigerants under this category are butane, isobutene, propane, ethane, methane, ethylene etc.
3. Chemical Compositions
They are further sub-divided as
These are obtained by replacing one or more hydrogen atoms in ethane or methane with halogens.
These are the mixtures of two or more refrigerants and behave as a compound.
Oxygen and Nitrogen Compounds
Refrigerants having either oxygen or nitrogen molecules in their structure, such as ammonia, are grouped separately and have a separate nomenclature from the halogenated refrigerants.
Cyclic organic Compounds
The compounds coming under this class are R316, R317 and R318.
These are further divided into two categories: Cryogenic and Non-cryogenic.
Cryogenic fluids are those which are applied for achieving temperatures as low as – 160 0C to – 273 0C. Above this temperature range, we can use a multi-stage refrigeration system to realise the desired temperature. But below – 160 0C, this is not possible since the COP of the cycle becomes very low. To attain temperatures below – 160 0C, we use refrigerants such as nitrogen, oxygen, helium, hydrogen etc. and for temperatures close to – 273 0C, magnetic cooling is employed.
The inorganic compounds which are employed above the cryogenic temperature ranges come under the remaining sub-division of inorganic refrigerants.
Compounds such as ethylene, propylene etc. are grouped under this head and grouped under the 1000 series for convenience.
This group contains those compounds which cannot be grouped under the other components. They are indicated by the 700 series with the last numbers being their molecular weight. Examples include air, carbon dioxide, sulphur dioxide etc.
As we can see from the above sub-divisions, they are not mutually exclusive. A compound may come under more than one sub-division. Hence, the importance of adopting the various naming conventions to designate the different refrigerants cannot be underestimated.
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