超临界水的热力学模拟:一种可用到4273K、2GPa的立方型状态方程

根据水的高精度热力学模型IAPWS-95和IAPWS-IF97产生的压力-体积-温度(PVT)数据,本文建立了超临界水的一种高精度立方型状态方程。在723.15~2273.15K和0~1.4GPa范围内,该方程的平均体积偏差只有0.26%;在此范围之外,直到4273.15K和2GPa,方程的平均体积偏差不到2%。该方程在精度和适用范围方面均明显优于以前的立方型方程。在可比的温压条件下,该方程也明显优于一些常用的多参数非立方型方程(多数是高次维里型方程)。本文根据上述立方型方程和有关的热力学原理导出了膨胀系数、压缩系数、逸度系数、剩余焓和剩余熵的解析表达式,其计算结果与IAPWS-95模型的结果均吻合得很好。在此基础上很容易计算出许多其它的热力学性质。

Thermodynamic modeling of supercritical water: A cubic equation of state up to 4273K and 2GPa

An accurate cubic equation of state for supercritical water is developed on the basis of the pressure-volume-temperature (PVT) data from the highly accurate thermodynamic formulations IAPWS-95 and IAPWS-IF97. In the range 723.15~2273.15K and 0~1.4GPa, its average volume deviation is only 0.26%. It can also be used outside the range up to 4273.15K and 2GPa with an average volume deviation of less than 2%. It is significantly superior to previous cubic equations of state in both accuracy and applicable P-T range. It is also obviously superior to the commonly used non-cubic equations (mostly high-order virial type equations) with many temperature-dependent parameters under comparable P-T conditions. According to the above cubic equation and relevant thermodynamic theorems, analytical expressions are derived for compression and expansion coefficients, fugacity coefficient, as well as residual enthalpy and entropy, whose calculated results agree very well with those of the IAPWS-95 formulation. With these results, many other thermodynamic properties can be calculated easily.