Azeotropic and Zeotropic Refrigerants: Properties and Differences

Azeotropic Refrigerant Blends

Azeotropic refrigerant blends are characterized by their constant temperature behavior during phase changes. They have a fixed boiling point. During evaporation or condensation, their composition remains unchanged. In practice, these blends are often treated like pure substances. A near-azeotropic refrigerant blend is R507, which is often considered azeotropic due to its minimal temperature glide. A true azeotropic refrigerant blend is R500.

Zeotropic Refrigerant Blends

Zeotropic refrigerant blends exhibit a temperature glide during phase changes. Their temperature varies during evaporation or condensation depending on the pressure. Additionally, their composition changes between liquid and vapor states. Examples of such refrigerants include R407A and R407F, which both belong to the ASHRAE R-4xx series.

Safety Classifications

Refrigerant blends are classified according to their flammability and toxicity. Class A1 refrigerants are non-flammable and have low toxicity. Examples include R507 and R404A. Class A2L refrigerants are slightly flammable but have low toxicity. R32 is a notable example. Highly flammable refrigerants with low toxicity fall into Class A3. Examples of these include R290 (propane) and R600a (isobutane).

Conclusion

Selecting the right refrigerant depends on the specific application and safety requirements. Azeotropic blends are particularly suitable for systems that require straightforward maintenance. Zeotropic blends, on the other hand, are often more efficient and are preferred in specialized applications.