Updated: Jul 24, 2020
When looking at the best option between ammonia, CO2, or utilizing both refrigerants for your application-- the size of the loads, the design constraints, facility layout, and the temperature ranges of the various loads all significantly impact the benefits of each configuration.
To review the key parameters that impact installation, energy, and recurring maintenance costs check out our recent blog post to see how Ammonia and CO2 compare! In this blog post, we cover the advantages of a CO2 + ammonia cascade systems, and review applications where this system offers specific advantages over other design options.
For assistance with a systematic review of the design options for your application, including estimated energy savings, please call us for a free consultation.
Following are specific advantages for CO2 to ammonia cascade systems:
· Carbon Dioxide (CO2) is often used for the low-temperature loads as this configuration often provide the highest ROI when all factors are considered.
· CO2 is often applied in a rack configuration favorable for the creation of different suction groups. By removing lower temperature loads from the ammonia plant, it is often possible to raise the temperature at which ammonia is applied. The chart below shows the significant impact on efficiency when the evaporator temperature is raised by even just a few degrees.
· The high discharge temperature and non-toxic nature of CO2 creates higher grade heat that is relatively easy to recover. When applied in processes that can utilize this high-grade heat, the energy impact can significantly raise the ROI for the cascade system.
· The integration of CO2 provides facility owners control over the ammonia charge, both in the overall charge level and the location where ammonia is applied throughout the facility. Limiting ammonia to the mechanical room, can increase safety, and significantly reduce maintenance/ regulatory costs.
Ammonia – Impact of Evap Temperature on Performance
1. Based on BITZER open-drive ammonia screw 9583 series
operating at 105F condensing, 2F superheat, 0F subcooling
2. Relative performance based on
nominal conditions of: -20F low-temp, +20F med-temp
Cascading System Simplified Sketch
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