二氧化碳混合工质临界参数计算模型对比研究

Study on the critical properties calculation models of CO_(2)-based binary mixture working fluid

二氧化碳(CO_(2))混合工质是具有应用潜力的动力循环工质,临界参数作为CO_(2)混合工质的关键基础热物性,对其进行准确地计算和预测具有重要意义。采用4种不同类型的计算模型,分别针对CO_(2)+HFC、CO_(2)+HFO和CO_(2)+HC三类二元混合工质的临界温度和临界压力进行了推算,并与公开发表的实验数据和REFPROP数据库计算结果进行对比,分析讨论了各种计算方法对各类CO_(2)混合工质的适用性。结果表明,Li方法形式简单,混合物临界温度的计算式仅与纯质组分的临界温度及临界体积有关,可用于CO_(2)+HFC和CO_(2)+HFO混合工质临界温度的快速推算。对于CO_(2)+HC混合工质,RK方法计算偏差最小,该类混合物临界参数实验数据点数和套数较多,因此可直接通过RK方法回归得到关联式进行应用。

Carbon dioxide(CO_(2))mixed working fluid is a power cycle working fluid with application potential.Critical parameters are the key basic thermophysical properties of CO_(2)mixed working fluid,and its accurate calculation and prediction are of great significance.Four types of calculation models were used to calculate the critical temperature and critical pressure of three types of binary mixture working fluids,namely CO_(2)+HFC,CO_(2)+HFO and CO_(2)+HC,and compared with the published experimental measured data and REFPROP database.The applicability of calculation models to each type of CO_(2)-based binary mixture is analyzed and discussed.The results show that Li method has a simple form,and the calculation formula of mixture's critical temperature is only related to the critical temperature and critical volume of the pure substances,which can be used to quickly calculate critical temperature of CO_(2)+HFC and CO_(2)+HFO.For the CO_(2)+HC,the RK method showed the lowest deviations when predicting the critical pressure.Due to the completeness on experimental data points and sets of critical properties,the correlation can be directly obtained through RK method for application.