In which refrigerant is the solubility of refrigerant oil lowest?

The solubility of refrigerant oil is lowest in carbon dioxide (CO2) compared to the other refrigerants listed. This characteristic is crucial in applications such as cooling systems, where oil circulation and lubrication must function effectively without mixing excessively with the refrigerant.

When oil is less soluble in the refrigerant, it remains in the compressor and other parts of the system where lubrication is needed, ensuring proper operation without the risk of impairing heat transfer efficiency. In practical terms, refrigerants like R-22, ammonia (NH3), and R-12 tend to have higher solubility of oil, which can lead to challenges in maintaining adequate lubrication and potentially result in efficiency losses or mechanical issues in the cooling system.

Understanding solubility is important for system design and performance, particularly in ensuring that the oil can do its job without the risk of flooding or reduced lubrication caused by excessive mixing with the refrigerant.