Natural Gases and their Effects on Lubricant Properties

A lubricant’s primary function is to protect against wear, reduce friction and transfer heat. These properties can be significantly affected by the solubilization of dissolved gases in the lubricant. For example dissolved refrigerants such as hydrocarbon gasses (methane, butane, propane) can significantly reduce a lubricants viscosity. This reduction in viscosity can result in increased friction, wear and component failure. Thus an understanding of the effect that these refrigerants have on a lubricant is absolutely essential.  

The degree of gasses effect on a lubricant is dependent on the pressure, temperature and the chemical make up of both the lubricant and the gas. This presentation will first review how pressure and temperature effect lubricant/gas solubility. The presentation will then review how the polarity, molecular weight and density of both the gas and the lubricant effect the degree of solubility. 

During the presentation we will also talk about the differences between solubility and miscibility, two often confused terms. The importance of lubricant/gas miscibility and its effect on cold temperature fluidity and lubricant return will also be discussed.  In addition, we will explore the differences between full miscibility and partial miscibility and how they can affect lubricant performance. 

The data used in this presentation will come from a combination of test data, and industry accepted calculations. The audience will be educated on how to interpret the data as well as how to read typical charts such as PVT curves (Daniel plots) and miscibility curves. 

The presentation will end by making recommendations on the ideal lubricant for each type of natural refrigerant. Listing both the benefits and the drawbacks for each recommendation.