Oil Talk – Short #167

In this short podcast episode, Bryan gets into some oil talk, covering some common refrigerant oil terms and types.

Esterification is the process by which organic acid and alcohol come together to form polyolester (POE) oil and water. Hydrolysis refers to the decomposition of a substance when it comes into contact with water; when POE mixes with water, it will break down into esters, organic acids, and alcohol. Once POE oil undergoes hydrolysis, the process can't be reversed to get the same original oil.

POE oil is also hygroscopic; hygroscopicity refers to the ability of the oil to absorb moisture. Miscibility refers to the ability of an oil to mix with refrigerant and be carried with it. In the context of refrigerant oil, “polar” refers to a molecular structure with an uneven distribution of electrons; oils with polar structures attract water molecules. Solubility refers to how well one compound can dissolve into another.

Mineral oil is a product of the distillation of crude oil and was common in systems that used CFC and HCFC refrigerants. Mineral oil isn't as miscible with new refrigerants that lack a chlorine molecule. Alkylbenzene (AB) is a synthetic oil used in some commercial refrigeration systems that is compatible with mineral oil. Polyolester (POE) oil is one of the most common synthetic oils we use in systems that use HFC refrigerants; its main downside is its high hygroscopicity and tendency to undergo hydrolysis. Polyalkylene glycol (PAG) oil is common in automotive A/C systems (R-134A) and is more hygroscopic than POE oil but does not undergo hydrolysis. Polyvinyl ether (PVE) oil is used as an alternative to POE oil; it is more hygroscopic but does not undergo hydrolysis.

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