Solubility of carbon dioxide refrigerant in alkyl naphthalene lubricating oil

A theoretical model of carbon dioxide solubility in alkyl naphthalene oil was established with the modified state equation on the basis of the molecular aggregation theory and the corresponding mixing rules. The critical physical properties of the oil were determined by the group contribution method. The comparison shows that the predictions of the carbon dioxide solubility in alkyl naphthalene oil by the solubility model based on the modified vdWaals equation agree well with the existing experimental data with a mean error of 5. 56% and 3. 47% under the experimental conditions, respectively. Moreover, the more precise value can be obtained at the higher carbon dioxide solubility because of the more obvious molecular aggregation phenomenon. However, the large errors of 48.92% and 46.91% confirm that the modified PR and RKS equations may not be applicable to determining the solubility of carbon dioxide in alkyl naphthalene oil. In addition, the variation of the solubility was predicted using the model developed. The results show that the solubility increases by about 19% from 3. 5 MPa to 4. 5 MPa at 0°C and 10°C, and decreases by 20. 9% and 12. 5%, respectively, when the superheat temperature is from 0°C to 20°C.