超临界水压力-体积-温度(PVT)新数据的评价

Assessment on the New Pressure-Volume-Temperature (PVT) Data of Supercritical Water

1990年以来,超临界水的PVT实验数据和分子动力学模拟数据已延伸到很高的温度和压力。文中详细评价了这些数据的质量。国际水和水蒸汽性质学会所推出的1995年版的水的状态方程(IAPWS95)被选作评价的可靠基础,同时辅以其适当的外延。分析结果表明,Zhang and Duan(2005)的模拟数据和Abramson and Brown(2004)通过声速实验值反演得到的PVT数据与目前最精确的水的PVT数据吻合得很好,但后者有较小的系统偏差。其它几组数据都有较大的系统偏差或不确定度。其中,Belonoshko and Saxena(1991)的模拟数据P-T范围很宽,但不确定度很大,而且有显著的系统偏差。Brdoholt and Wood(1993)的模拟数据也有显著的系统偏差。随着压力的增加,这两组模拟数据的体积偏差都有由正转负的趋势,其中后者尤为显著,而且在高压下离散性很弱,因而易于校正。Withers et al.(2000),Brodholt and Wood(1994)和Frost and Wood(1997)的实验数据都有明显的正偏差,其中前一组的偏差较小,后两组的偏差较大,原则上均可近似地校正。Larrieu and Ayers(1997)的数据总体不确度较大,其中偏差较小的数据仅限于特定的温度和压力,其它数据的偏差没有明显的规律。这些结果应当有助于上述新数据的正确使用和进一步优化。

Since 1990, the PVT data of supercritical water from experiments and molecular dynamics simulations are extended to very high temperatures and pressures. These data are assessed in detail in this work. The equation of state for water developed by the International Association for the Properties of Water and Steam （IAPWS95） is chosen as a reliable basis for the assessment, which is also aided by appropriate extrapolation of the equation. The results suggest that the simulated data of Zhang and Duan （2005） and those of Abramson and Brown （2004） derived from sound velocity measurements agree well with those of the most accurate data of water at present, but the latter has small systematic deviations. The data in the other groups have obvious systematic deviations or uncertainties. The simulated data of Belonoshko and Saxena （1991） have a large P-T range, but they also have large uncertainties and obvious systematic deviations. The simulated data of Brodholt and Wood （1993） also have notable systematic deviations. As pressure increases, the volume deviations of these two groups of simulated data vary from positive to negative, where the deviations in the latter group are particularly obvious, and show very strong pressure dependence features at high pressures, so they are easy to correct. The experimental data of Withers et al. （2000）, Brodholt and Wood （1994） and Frost and Wood （1997） have obvious positive deviations, and can be corrected in principle, where the deviations of the first group are small, but those of the latter two are much bigger. Overall, the experimental data of Larrieu and Ayers （1997） have large uncertainties, where small deviations are only limited to the data at specific temperature and pressure, and the deviations of the other data have no obvious regularity. These results should be helpful in the correct use of and further refinement of the above data.