GPSA Ch. 14
| Parameter | Range |
|---|---|
| Propane Evaporator | −40 to +40°F |
| Ethylene Evaporator | −150 to −50°F |
| Methane Evaporator | −260 to −150°F |
| Cascade Approach | 5–10°F |
| COP (2-stage cascade) | 1.5–3.0 |
Coefficient of Performance (COP):
Where QL = cooling duty at the evaporator, Wnet = total compressor power input across all stages.
Optimal Interstage Temperature:
Geometric mean of absolute condenser and evaporator temperatures minimizes total compressor work for equal compression ratios per stage.
Cascade Advantage: By splitting the total temperature lift across multiple refrigerants, each compressor operates at a lower compression ratio. This reduces discharge temperatures, improves volumetric efficiency, and significantly reduces total power consumption compared to single-stage operation.
Power Savings: A 2-stage cascade typically saves 20–35% compressor power vs single-stage over the same temperature range.
Understand cascaded refrigeration design, refrigerant selection, and cryogenic process optimization