Classification, Types and Examples of Refrigerants

A refrigerant is defined as a heat carrying medium. According to the requirement of application, different types of refrigerants are used in indutries and domestic scale. Refrigerants are classified on different basis. In this tutorial, we are going to learn about how refrigerants are classified and what are the types of refrigerants are being used (were being used) in the world.

Classification of refrigerants

We can classify refrigerants considering several basis as below and examples of refrigerants are mentioned with each basis.

  1. Basis: Safety of refrigerants
  2. Basis: Working principle
  3. Basis: Chemical composition
  4. Basis: Nature of refrigerants

classifications of refrigerants in air conditioning

Basis: Safety of refrigerants

There are three sub-classifications considering safety of refrigerants.

  1. Safe refrigerants: These refrigerants are not toxic and non flammable. Therefore using these refrigerants is safe for health of humans. Carbon dioxide (CO2), water (H2O), R-11, R-12 are few examples to safe refrigerants.

  2. Toxic refrigerants: These refrigerants can be harmful to health of people if people were exposed to such kind of refrigerants. Ammonia (NH3), sulfur dioxide (SO2), ethylene chloride are several examples.

  3. Flammable refrigerants: These refrigerants can catch fire if flammable conditions are met. Butane and isopropane are two examples for flammable refrigerants.

Basis: Working Principle

There are two classifications considering working principle (refrigerant cycle).

  1. Primary refrigerant: These kind of refrigerants are directly undergone through the refrigerant cycle which has four stages; compression,cooling, condensation and expansion. In each phase, a phase change is occurred due to sensible heat transfer. R12, R22, CO2 and NH3 are few examples for primary refrigerants.

  2. Secondary refrigerant: These refrigerants do not undergone through the refrigeration cycle as primary refrigerants. Secondary refrigerants are used only for cooling purposes and water, brine, calcium chloride solutions are few examples.

Basis: Chemical composition

Four groups can be identified when chemical composition of refrigerants are considered and discuss in detail in next section of this tutorial.

  1. Halocarbon refrigerants
  2. Azeotropes
  3. Hydrocarbons
  4. Inorganic

Basis: Nature of refrigerants

  1. Natural refrigerants
  2. Artificial / Synthetic refrigerants

Types of refrigerants

Here, we will look types of refrigerants in detail.

Halocarbon refrigerants

In these refrigerants, there are Chlorine, Fluorine and Carbon (sometimes Hydrogen too). Because these halocarbon refrigerants has the capability of damaging ozone layer and causing other environmental damages, they were globally banned. There are (were) several halocarbon refrigerants in the market and will provide you a detailed description for each of them. These halocarbon refrigerants are commercially available as "Freons".

Refrigerant Number Name of Chemical Chemical Formula
R-11 Trichloromonofluoromethane CCl3F
R-12 Dichlorodifluoromethane CCl2F2
R-22 Chlorodifluromethane CHClF2
R-40 Methyl chloride / Chloromethane CH3Cl
R-113 Trichlorotrifluroethane CCl2FCClF2

Let's discuss above refrigerants in detail.

R-11 / Trichloromonofluoromethane / Trichloromonofluoromethane (CCl3F)

  • A low pressure refrigerant
  • Non flammable and non-toxic
  • Applications: in large centrifugal compressors, to clean internal parts of compressors used in refrigeration purposes (as a flushing agent)
  • Melting point: -1110C
  • Boiling point: 23.70C
  • High pressure: 1.23 bar
  • Low pressure: 0.202 bar
  • How to identify leakages: Use a soap solution or a halide torch or by an electronic sensor

R-12 / Dichlorodifluoromethane (CCl2F2)

  • Non flammable and non-toxic, there is a faint ethereal odor
  • Applications: in small refrigeration machines, in rotary and reciprocating compressors, freezers, water coolers
  • Melting point: -1580C
  • Boiling point: -29.80C
  • Extreme pressures: 0.82 and 6.4 bar

R-22 / Chlorodifluromethane (CCHClF2)

  • Non flammable, non-toxic, non-corrosive, ethereal odor, colourless gas at room temperature
  • Applications: Used in fast freezing machines which requires low evaporation temperatures, also used in chillers and air-conditioners
  • Melting point: -157.40C
  • Boiling point: -40.80C
  • Extreme pressures: 1.92 bar and 10.88 bar

R-40 / Methyl chloride / Chloromethane (CH3)Cl

  • clear, colorless gas at room temperature, has a faint, sweet odor. Gas is noticeable only at levels that may be toxic to inhale. It is heavier than air, and it is extremely flammable.
  • Applications: reciprocating and rotary compressors, to identify leakages
  • Melting point: -97.60C
  • Boiling point: -23.70C
  • Extreme pressures: 1.92 bar and 10.88 bar

R-113 / Trichlorotrifluroethane / CCl2FCClF2

  • A colorless liquid with a sweet, ether-like odor and irritant.
  • Applications: In industrial refrigeration systems where centrifugal compressors are used.
  • Melting point: -36.220C
  • Boiling point: 47.70C

Azeotrope refrigerants

Stable mixture of refrigerants which have identical compositions in both liquid and vapor phases over a wide temperature rage is defined as azeotrope refrigerants.

Refrigerant Number Formula of Azeotrope Mixture Chemical Formula
R-500 R-12:73.8% and R-152: 26.2% CCl2F2 + CH3CHF2
R-502 R-22: 48.8.8% and R-115: 51.2% CHClF2 + CClF2CF3
R-504 R-32: 48.2% and R-115: 51.8% CH2F2 + CClF2CF3