CO2 as a Refrigerant – Retail Booster Systems
This is post number ten of a series.
Retail Booster Systems
Two-stage compression is used for transcritical low temperature applications because the discharge temperature of R744 is high and will potentially result in lubricant breakdown. Figure below shows a simple two-stage booster or externally-compounded system:
Simple booster system without oil management
The refrigerant from the low-temperature loads is drawn into the low-stage compressors. The discharge from these compressors goes into the suction of the high-stage compressors.
The refrigerant from the medium-temperature (MT) loads is drawn into the suction of the high-stage compressors. The refrigerant from the receiver pressure-regulating valve is also drawn into the suction of the high-stage compressors. The flash gas from the receiver pressure-regulating valve and the suction gas from the medium temperature loads provide some interstage cooling. This is usually enough to maintain the discharge temperature of the high-stage compressors below the level at which the lubricant will deteriorate. Additional interstage cooling can also be provided if required.
In the next article of this series we’ll take a closer look at retail cascade systems.
Director – CO2 Business Development, Emerson Climate Technologies
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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:
- Series Introduction
- Criteria for Choosing Refrigerants
- Properties of R744
- Introduction to Trancritical Operation
- Five Potential Hazards of R744
- Comparison of R744 with Other Refrigerants
- R744 Advantages / Disadvantages
- Introduction to R744 Systems
- Introduction to Retail Transcritical Systems
- Retail Booster Systems
- Introduction to Retail Cascade Systems
- Introduction to Secondary Systems
- Selecting the Best System