Thermophysical Properties of Unfrozen Water

人们在研究水的热物理性质方面做了大量的工作。在低温和高压下的测量存在许多技术困难，而且与高温下的水相比，未冻结水的体积行为并不是很清楚。到目前为止，只有Bridgman和AlekSandrov等人报道了未冻水的PVT关系。在本研究中，设计并建造了一种新的装置，用于在零度以下的高压下准确测量未冻水的压力-体积-温度关系。目前测量的不确定度估计小于0.09%。为了验证该装置和测量的可靠性，将293.15K高压下的实验数据与一些文献值进行了比较。我们的实验数据与Kell和Whalley的一致，并根据Soul和Wagner报告的状态方程在估计的实验误差内计算了值。在压力高达200 mpa的情况下，沿着258-273K区域内的三条等温线测量了未冻水。所有测量值均符合Tait型方程。该公式能较好地再现未冻水的比容，误差小于0.02%。与前人的数据比较表明，在非冻结区的实验数据与由状态方程计算的数据比Bridgman的数据更接近。

A great deal of effort has been made on the investigation for the thermophysical properties of water. There are many technical difficulties on the measurement at low temperature and under high pressures and the volumetric behavior of unfrozen water is not well known compared with that of water in higher temperature. Up to the present, only Bridgman and Aleksandrov et al.have reported the PVT relationships of unfrozen water.In the present study, a new apparatus using the "high pressure burette" method was designed and constructed for the measurements of the accurate pressure-volume-temperature relationships of unfrozen water at subzero temperature under high pressure. The uncertainty of the present measurements was estimated to be less than 0.09%. To confirm the reliability of this apparatus and measurements, the experimental data obtained at 293.15K under high pressure were compared with some literature values. Our experimental data agree with those of Kell and Whalley and calculated values from the equation of state reported by Soul and Wagner within the estimated experimental error. Measurements for unfrozen water have been performed along three isotherms in the region from 258 to 273K at pressures up to 200MPa. All measurements have been fitted to Tait type equation. This equation can reproduce the specific volume of unfrozen water with an error better than 0.02%. Comparison of our data with previous works shows that the experimental data in unfrozen region agree more closely with the data calculated from the equation of state than that of Bridgman.