Refrigerants are used in the cooling process, which is the process by which heat is removed from the matter or space. Refrigerant is a substance which raises the latent heat, when he evaporated from a liquid to a gas. This is done at low temperature and pressure. Refrigerant casts out the latent heat of condensation of a gas to a liquid at high pressure and temperature. The refrigerant is cooled by absorption of heat in one place and unloaded it in another area.
The desirable properties of a good refrigerant for commercial use are: Low boiling point Safe, nontoxic. Easily liquefy and moderate pressure and temperature High latent heat of combustion Operation with gauge pressure, is Not affected by moisture well Mixed with oil Corrosion of metal. There are other qualities that all refrigerants: the molecular weight, density, compression ratio, combustion heat, and compression temperature. These qualities will vary depending on the refrigerant used. In compressor the amount and type or design will also affect the choice of refrigerant.
CLASSIFICATION
Refrigerants are classified according to their way of absorption or extraction of heat from substances in the fridge:
Class 1 refrigerants used in the standard compression type refrigerating systems
Class 2 refrigerants are used as direct cooling between the agents of Class 1 and 3 types and substances for cooling products
Class 3 refrigerants used in the standard absorption refrigeration systems
Class 1 refrigerants in the cool absorption or extraction of latent heat from the matter.
Class 2 refrigerants cool substances, absorbing their reasonable heats. They include air, calcium chloride brine chloride-sodium salt in brine, alcohol, and similar non-freezing solutions.
Class 3 refrigerants consist of solutions, which include absorbed vapor liquefiable agents or refrigerants. These functions through solutions to their ability to carry liquefiable vapors. Couples produce a cooling effect of the absorption of latent heat. For example, aqua ammonia that is the solution, which consists of distilled water and pure ammonia.
COMMON REFRIGERANTS
Below are some of the most common refrigerants. In table. table 6.1 shows the characteristics of the selected set of refrigerants available for home, commercial and industrial use.
Refrigerants 
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