Solubility of CO2 in commercial POE Oils with different standard viscosity

The selection of the optimal commercial oil to be used as lubricant in a refrigerating system with carbon dioxide (CO2) as working fluid is not solved yet, though POE and PAG oils give acceptable results. Only a real knowledge of the oil structure and thermodynamic behavior of the oil+refrigerant mixture allows a proper selection of the lubricant. Then, a systematic study on the solubility of CO2 in some commercial POE oils and their precursors is underway at our laboratory, and several measurements have been performed till now. Here, an investigation on the solubility of CO2 in commercial POE lubricants with different ISO standard viscosity is presented on the base of measurements performed at temperatures from 283 K and 343 K. The results are discussed and compared with the solubility of precursors in view of the development of thermodynamic models able to predict the properties of the mixture oil+refrigerant.