The core role of refrigerant oils is to provide lubrication for the system.
Refrigeration cycles involve different temperature and pressure levels, and refrigerant oils must remain effective regardless of changes. Oils must also offer longevity and resist deterioration under different operating conditions.
Refrigeration oils have key properties that help them perform their purpose and, in this blog, we’ll explain them in turn.
Viscosity
Lubricants have varying levels of viscosity.
In simple terms, viscosity refers to how thick an oil is. The more viscous an oil is, the slower it moves, making it harder to circulate refrigerant through the system.
As a result, it must work harder to transfer heat, defeating the core aim of the refrigeration cycle. As a result, refrigeration oils must have low viscosity.
Miscibility
How effectively an oil mixes with the refrigerant is referred to as miscibility.
When an oil isn’t miscible with the system refrigerant, it can result in an inefficient refrigeration cycle. This puts equipment under excessive strain and can lead to mechanical failure.
Refrigerant oil must be miscible with the refrigerant so that it combines well and lets the refrigerant work effectively to transfer heat.
Hydrolysis and hygroscopy
When water breaks down a product, the process is called hydrolysis.
Some types of oil react with water and deteriorate into alcohol and acids. When this occurs, metal equipment components can become damaged.
In closed systems, refrigerant oil can cycle millions of times, but when there is risk to water contamination, oils must be resistant to hydrolysis, or decomposition can put equipment at risk.
Some oils in circulation are classed as hygroscopic. Such lubricants attract and retain moisture leading to system contamination. As a result, these oils cannot be deployed in systems where moisture is present.
Moisture can put refrigeration systems at risk and can cause severe problems. When water enters the system and freezes, it can create a solid obstruction in circulation pipes. These unwanted blockages can result in inadequate cooling of the system.
Flammability
Finally, the flammability of a refrigeration oil is another important property to consider.
For safe operation, refrigerant oils cannot be explosive or flammable at the pressures and temperatures experienced by the system.
To work out the best type of oils that should be deployed in an application, there are specific flammability tests that operators can conduct. Refrigeration oil users can also refer to the original equipment manufacturer of their system for the recommended lubricant.
