Molecular modeling of the solubility of low global warming potential refrigerants in polyol ester lubricants
Abstract Pentaerythritol esters (PECs) act as the main precursors in polyol ester (POE) lubricants. The solubility of low global warming potential (GWP) refrigerants in linear chained PECs was studied in this work using the perturbed chain form of the statistical associating fluid theory (PC-SAFT). The effect of PEC alkyl tail length on the solubility of various refrigerants was investigated. Results showed that the solubility of HFO refrigerants is weakly dependent on PEC molecular structure. On contrary, the solubility of other natural and paraffin refrigerants significantly increased with increasing the alkyl tail length. Within the SAFT framework, pure component and binary interaction parameters were found to correlate linearly with PEC molecular weight. These correlations were used to predict the solubility of refrigerants in a predefined PEC blend through component lumping. Sensitivity analyses showed that the latter simplification could adequately describe the mixture phase behavior. The proposed model was then applied to fully and accurately predict the solubility of carbon dioxide in commercial POE lubricants. Results demonstrate that the proposed model can be used as a fully predictive tool to determine the solubility of refrigerants in commercial POE oils, provided that the lubricant molecular weight is known, a clear step forward developing adequate low GWP refrigerants-lubricant pairs.