Primary and secondary refrigerants:

What is Refrigerant
A refrigerant is a substance or mixture, used in a refrigeration cycle. Generally, It undergoes phase transitions from a liquid to a gas and back again.

Types of Refrigerant:

1. Primary Refrigerant:

Primary refrigerant directly take part in refrigeration, Eg Freon ( R11, R22, R32, R407C, R134a etc), Ammonia, water.  Theses refrigerants directly absorb heat from a system and take part of refrigerant cycle. In case of Primary refrigerant latent heat transfer takes place.

Selection of primary refrigerant depends upon 

  1. Properties of refrigerant, like flammability, toxity, reactivity, chemical stability etc.
  2. Environment acceptability like Average life, Global warming potentical, Ozon depletion potential
  3. Cost and efficiency of refrigerants

Some Common Primary Refrigerants:

The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane (R-11 or CFC-11) being fixed at an ODP of 1.0.

Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere up to a specific time horizon, relative to carbon dioxide.

2. Secondary Refrigerant
Secondary refrigerant are cooled by primary refrigerant and then they are circulated, eg Chilled water, Chilled brine.( Methanol, Glycol, Cacl2 etc), In most cases secondary refrigerant  usage sensible heat transfer.

Avoidance of secondary refrigerant will improve energy efficiency in the system, while use of secondary refrigerant system provides freedom from design complication and can be managed easily.

Some Common Secondary refrigerants:

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