Classification of Refrigerants

1.On the basis of safety:

• Toxic refrigerants (Ex: NH3, SO₂, ethylene, chloride, etc.)
• Flammable refrigerants (Ex: Butane, Iso-propane, etc.)
• Safe refrigerants (Ex:CO2, H₂O, R11, R12, etc)

2. On the basis of working principal:

Primary refrigerants:

• Are those fluids, which are used directly as working fluids, for example in vapour compression and vapour absorption refrigeration systems.
• The refrigerants undergoes compression, cooling, condensation and expansion with change in phase.
• These fluids provide refrigeration by undergoing a phase change process in the evaporator.

Examples: R12, R22, CO₂, NH3

Secondary refrigerants:

• This refrigerants does not undergo the cyclic process in refrigeration, but it used only as a medium for cooling.

• which are used for transporting thermal energy from one location to other.

• Secondary refrigerants are also known under the name brines or antifreezes.

Examples: H2O,Brine, Calcium chloride solution

3. On the basis of chemical composition :

Halocarbon Refrigerants

• Halocarbon Refrigerant are all synthetically produced and were developed as the Freon family of refrigerants.
• Essentially these refrigerants are compounds of chlorine, fluorine and carbon.

Examples:

CFC's: R11, R12, R113, R114, R115

Azeotropes:

• This group of refrigerants consist of mixture of different refrigerants which cannot be separated under pressure and temperature and they have fixed thermodynamic properties.
• Azeotropic mixtures are designated by 500 series.
• Azeotropic mixtures:

R 500: Mixture of R 12 (73.8 %) and R 152a (26.2%)

R 502: Mixture of R 22 (48.8 %) and R 115 (51.2%)

Hydrocarbons:

• These refrigerants are nothing but compound of hydrogen and carbon.

• Due to a ban on CFC, considerable interest has been generated in exploration of these refrigerant as alternatives.

• These refrigerants have excellent thermodynamics properties, but are highly flammable and thus unsafe. some important hydrocarbons as refrigerant are:

Examples:

Propane (C³HS): R 290

n-butane (C¹H¹0): R 600

Iso-butane (C4H¹0) : R 600a

Inorganic compounds:

• These are non hydrocarbon group refrigerants, mostly naturally available.
• They were used before the development of hydrocarbon group refrigerants and are still in use.
• They being looked upon as environment friendly refrigerants for the future.

Examples:

Ammonia: R 717

Water: R 718

Air : R 729

Carbon dioxide: R 744