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What is refrigerant or gas in refrigeration system?

 Refrigerant in refrigeration system



   the fluid used for energy exchange in the refrigerating or heat pump is called the refrigerant. The refrigerant usually absorb heat while undergoing a phase change and then is compressed to a higher pressure and higher temperature.Allowing it to transfer that energy directly or indirectly to the atmosphere or medium being purposefully heated. Refrigerant  suitability for a given application depend on many factors including its thermodynamics physical and chemical properties and its safety. The significance or relative importance of each characteristics varies from one application to the next and there is no such thing as an ideal refrigerant for all applications some of the characteristics of general importance are as follows.


Thermodynamics characteristics

1) High latent enthalpy of vaporization:- these means a large refrigerating effect per unit mass of the refrigerant circulated  in small capacity systems however resulting low flow rate May actually lead to problem.

2) low freezing temperature:- the refrigerant must not solidify during normal operating condition.

3) Relatively high critical temperature:- large amounts of power would otherwise be required for competition

4) positive evaporating pressure:- pressure in the evaporator should be above atmosphere to prevent air from looking into the system.

5) Relatively low condensing pressure:- otherwise expensive piping and equipments will be required

Physical and chemical Characteristics

1) high dielectric strength of vapour:- this permits use in hermetically sealed compressor where vapour may come in contact with motor winding 

2)Good heat transfer characteristics:-   thermophysical properties should be such that high heat transfer Coefficient can be obtained 

3)Satisfactory oil solubility:- oil can dissolve in some refrigerant and some refrigerants can dissolve in oil this can affect lubrication and heat transfer characteristics and lead to oil logging in evaporator.A system must be designed with oil solubility characteristics in mind

4) Low water solubility:- Water in the refrigerant can lead to freeze up in the expansion device or corrosion.

5) Inertness and stability:- Refrigerant must not react with the material that will contact it, and it's own chemical makeup must not change with time.

Safety 
1)Non flammability:- The refrigerant should not burn or support combustion when mixed with air.

2)Non toxicity:- The refrigerant should not be harmful to humans, either directly or indirectly through foodstuffs.

3) Nonirritability:- The refrigerant should not irritate humans

Effect on the Environment

1) Ozone Depletion Potential:-  The refrigerant potential to deplete the ozone in the upper atmosphere should be low.

2) Global warming potential:- The refrigerant potential to persists in the ozone in the upper atmosphere and to trap the radiation emitted by the earth should be low.

Refrigerant Safety Group








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