Refrigerant Definitions

Pure Fluid

• A fluid when used in refrigeration cycle does not change volumetric composition or saturation temperatures as they evaporate or condense at a constant pressure
  
  
• r-12, r-134a

Blend

• Refrigerants consisting of mixtures of two or more different chemical compounds

Azeotrope

• A refrigerant blend when used in refrigeration cycle does not change volumetric composition or saturation temperature appreciably as the evaporate or condense at a constant pressure
  
  
• R-33, R-507

Near-Azeotrope

• Azeotropic blend with a small temperature and composition glide over the application range.
  
  
• No significant effect on system performance operation, and safety
  
  
• R-404a (hp62)

Zeotrope

• Blends, when used in refrigeration cycle, that change volumetric composition and saturation temperature to varying extent as they evaporator or condense at a constant pressure
  
  
• R-401a (mp39)

Glide

• The difference between the starting and ending temperature of a phase change process by a refrigerant at a constant pressure

 Fractionalization

• A change in the composition of a blend by preferential evaporation of the more volatile component or condensation of the less volatile component

Critical Temperature

• The highest temperature at which a refrigerant can exist as a liquid
  
  
• When a refrigerant reaches its critical temperature it can no longer be condensed into a liquid

Critical Pressure

• The vapor pressure at a critical temperature