二氧化碳制冷剂在烷基萘润滑油中的溶解度研究

Solubility of Carbon Dioxide Refrigerant in Alkyl Naphthalene Lubricating Oil

为了研究二氧化碳制冷剂在烷基萘润滑油中溶解度的变化,根据分子聚集理论修正了状态方程并运用相应的混合法则,建立了二氧化碳在烷基萘润滑油中溶解度的理论计算模型.模型中润滑油的临界物性参数通过基团贡献法估算得到.与现有文献实验数据对比发现,建立在vdWaals分子聚集理论修正方程上的理论模型计算值与实验数据吻合较好,实验工况下的平均误差分别为5.56%和3.47%,且溶解度越高,分子聚集现象越明显,模型计算值越准确.利用PR和RKS修正方程计算出的溶解度误差均非常大,分别达到了48.92%和46.91%,不适用于二氧化碳制冷剂在烷基萘润滑油中溶解度的理论计算.利用模型对二氧化碳溶解度随温度和压力的变化趋势进行了预测,发现在0℃和10℃下,压力从3.5MPa增加到4.5MPa时,溶解度约提高19%,而当过热度从0℃升高到20℃时,溶解度分别降低20.9%和12.5%.

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 ℃ and 10 ℃,and decreases by 20.9% and 12.5%,respectively,when the superheat temperature is from 0 ℃ to 20 ℃.