Freezing Technology

3.2.8. Physical characteristics of refrigerants

• Boiling and condensing temperature and pressures
• Freezing temperature
• Critical temperature
• Discharge temperature
• Latent heat of vapourisation
• Specific heat
• Density
• Viscosity

Boiling and condensing temperature and pressures

• The evaporator and condensing temperatures determine the pressures
• The maximum condensing temperature is largely affected by climatic condition
• It is desirable to select a refrigerant whose saturation pressure (at minimum operating temperature) is a few pounds above atmospheric pressure.

Freezing temperature

• Should have low freezing temperature to avoid operational obstruction by the refrigerant itself

Critical temperature

• Should be well above the maximum condensing temperature

Discharge temperature

• High discharge temperatures from the compressor should be avoided
• It causes some refrigerant breakdowns as well as poor lubrication effectiveness

Latent heat of vapourization

• Heat which converts the refrigerant from the liquid state to vapour
• It should have a higher value

Specific heat

• Higher specific heat is not desirable

Density

• Low vapour density refrigerants are preferred

Viscosity

• Low viscosity of the liquid refrigerant is desired to reduce the pressure drop in the lines