In a zeotropic blend, do all refrigerants have the same boiling point?

• A. True
• B. Depends on the pressure
• C. False
• D. Only in azeotropic blends

Answer: (C)

In a zeotropic refrigerant blend, you don't have a single boiling point for the mixture. Each component has its own distinct boiling point, so the mixture boils over a range of temperatures at a given pressure. As boiling proceeds, the liquid becomes richer in the less volatile components and the vapor becomes richer in the more volatile ones, creating a temperature glide during phase change. Because of this, not all refrigerants in the blend share the same boiling point. Only in azeotropic blends do all components boil at the same temperature, behaving like a single substance. So this statement is false.