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CO2 as a Refrigerant – Selecting the Best System

This is post number 13 of a series.

Selecting the Best System – Booster Versus Cascade Versus Secondary

Table 1 lists the advantages and disadvantages of cascade, transcritical, and secondary retail systems

Table 1

Table 1.2

Table 2

Table 3


Transcritical operation is generally less efficient than subcritical operation, so system type selection is usually driven by the ambient temperature profile:

  • Transcritical systems are normally used in areas where the ambient temperature is generally low (i.e., predominantly below 68 °F to 77 °F (20 °C to 25 °C), such as northern Europe and Canada.
  • Cascade and secondary systems (subcritical R744) are usually used in high ambient areas such as southern Europe, the U.S., much of central and South America, southeast Asia, Africa and Australia. The use of transcritical systems in high ambients generally results in lower efficiency, hence cascade or secondary systems are preferred in these areas.
  • Efficiency improvement for Booster Transcritical system for high ambient conditions is being aggressively developed to allow wider use of these systems.

The next articles in this series will provide more detailed information about the design and components of R744 cascade, transcritical booster and secondary systems.

Andre Patenaude
Director – CO2 Business Development, Emerson Climate Technologies

Visit our website for additional information on CO2 Solutions from Emerson. 
Excerpt from original document; Commercial CO2 Refrigeration Systems, Guide for Subcritical and Transcritical CO2 Applications.

To read all posts in our series on CO2 as a Refrigerant, click on the links below:

  1. Series Introduction
  2. Criteria for Choosing Refrigerants
  3. Properties of R744
  4. Introduction to Trancritical Operation
  5. Five Potential Hazards of R744
  6. Comparison of R744 with Other Refrigerants
  7. R744 Advantages / Disadvantages
  8. Introduction to R744 Systems
  9. Introduction to Retail Transcritical Systems
  10. Retail Booster Systems
  11. Introduction to Retail Cascade Systems
  12. Introduction to Secondary Systems
  13. Selecting the Best System
One Comment Post a comment
  1. Wayne Wang #

    Looking forward to the next articles

    November 14, 2021

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