真实气体等压热容的关联

Correlation of Heat Capacity at Constant Pressure for Real Gas

根据热力学原理,在第二维里系数关系式、RK方程与SRK方程基础上导出了真实气体等压热容的关联式。利用这些关联式计算了包括极性气体的3种真实气体在不同压力和温度下的等压热容,并与文献上的实验数据进行了比较。计算结果表明:基于第二维里系数关系式的等压热容关联式简单方便,在p<10MPa与对比体积Vr≥2的条件下,计算误差一般在3%以下;在不接近露点的条件下,基于SRK方程导出的关联式计算误差一般小于4%,基于RK方程导出的关联式对于非极性气体计算误差一般小于4%;本文关联式计算准确性优于剩余热容图法,为工程计算提供了一种便于计算机应用的计算方法。

On the basis of secondary Virial coefficient relation, RK equation and SRK equation, a correlation for heat capacity at constant pressure of real gas was derived on the thermodynamics principle. The correlation was used to calculate the heat capacity for three kinds of real gas with polar gas included at different pressures and temperatures. Comparison was made between the calculating result of the correlation and literature experiment data, it indicates that the correlation based on secondary Virial coefficient relation is simple and convenient, at conditions ofp 〈 20 MPa and Vr≥4, its calculating error is generally below 3%, at conditions of non-close dew point the calculating error of the correlation based on the SRK equation is generally below 4%, the calculating error of the correlation based on the RK equation is generally below 4% for non- polar gas. The correlation is more accurate than method by diagram of surplus heat capacity, a convenient and practical method for computer is provided for engineering calculation in this paper.