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What is “Cascade” Refrigeration?
Photo Courtesy of Emerson
What is Cascade refrigeration?
“Cascade refrigeration” is a term you will hear more and more over the coming years, and while some of the systems may be very complex, the concept is actually pretty simple.
Some refrigerants are well-suited for high and medium-temperature applications, and some are better suited for lower-temp applications. In a cascade system, the high/medium-temp refrigerant circuit is used to cool the condenser of the low-temp circuit via a heat exchanger.
In essence, the condenser for the low temp system is also the evaporator or part of the evaporator of the high/medium temp system.
In the diagram above, the medium-temp circuit is used in the medium temp cases and is ALSO used in the heat exchanger to condense the refrigerant in the low temp circuit.
There are many reasons for this type of system, but one of the big reasons is that it is a practical solution for using CO2 (R744) as a-low temp refrigerant.
Many different refrigerants are used in cascade systems often several at the same time. Also many cascade systems use a very refined purified butane as a lubricant for the refrigerant. Helps keep the system from getting oil logged.