Abstract: Predictions on the solubilities of substances in supercritical fluids have to rely on the equation of state. Consequently, it is very important to develop an equation of state applicable to supercritical fluids, especially for fluids approaching critical conditions. The p-V-T properties of 10 substances CO2, G2H4, C3H8, etc. in the supercritical region were calculated by the RK, RKS, PR, CS-RK and CS-vdW equations of gases state and the calculated results were compared with experimental data. It was found that all these equations of state were not adoptable to the supercritical region, especially at the points approaching critical. A modified RKS equation of state, employing molecular thermodynamics, was suggested: This equation of state was used to calculate the p-V-T properties in the supercritical region and was found to be of good accuracy. In the region approaching the critical point, deviations in calculations by this modified RKS equation were much smaller than those of other equations of state.

摘要： 木文对目前常用的RK、RKS、PR及CS-vdW等状态方程进行了考察,验算了它们对二氧化碳、乙烯、丙烷等十种体系在超临界区、特别在临界点附近区域的适用性.计算结果表明,在上述区域内计算偏差都较大.作者从统计热力学的角度提出了一个“m-RKS”方程:P=RT/(V-b(T))—a(T)/V[V+b(T)],用该方程进行计算,结果与文献报道的实测值之间的偏差大大低于上述常用的诸方程.