- Secondary Refrigerants – Transfers heat from the cooling load to the primary refrigerant.
- Water-Based Secondary Refrigerants
- Water (0°C limit)
- Brines: NaCl, CaCl₂ (for sub-zero cooling)
- Glycols: Ethylene Glycol (EG), Propylene Glycol (PG)
- Hydrocarbon-Based
- Silicone Oils (Extreme temps)
- Thermal Oils (Industrial heat transfer)
- Phase-Change Fluids
- CO₂ (R-744) (Cascade systems)
- Ammonia (R-717) (Industrial cooling)
- Uses:
- HVAC & district cooling
- Cold storage & food processing
- Ice rinks & cryogenic applications
