Oil Structure Influence on the Solubility of Carbon Dioxide in POE Lubricants

A better knowledge of the transport and thermodynamic properties for the refrigerant+lubricant system is required to properly design the refrigeration circuit. This is essential also to develop proper models able to predict the behavior of the mixture refrigerant+lubricant depending on the working conditions. However, the experimental data available in literature are insufficient to build dedicated models, being frequently related to commercial lubricants with undefined structure. Recently, a series of measurements have been performed at isothermal conditions with a static method to evaluate the solubility of carbon dioxide in commercial POE lubricants and pure pentaerythritol tetraalkyl esters (both linear and branched) as POE precursors. Parallely, the PRSV EoS, with the Huron-Vidal mixing rules has been selected for the correlation of the solubility data. The paper presents a discussion on the solubility data obtained and their correlation with the selected model, with particular reference to the influence of the lubricant structure.