Thermophysical Properties of Unfrozen Water

人们对水的热物理性质进行了大量的研究。低温高压下的测量存在许多技术难点，与高温下的水相比，未冻结水的体积行为还不清楚。迄今为止，只有Bridgman和Aleksandrov等报道了未冻水的PVT关系，本文设计并建造了一种新的高压滴定管法装置，用于测量高压下零度以下未冻水的精确压力-体积-温度关系。目前测量的不确定度估计小于0.09%。为了证实该装置和测量的可靠性，在293.15K的高压下获得的实验数据与文献值进行了比较。我们的实验数据与Kell和沃利的数据以及Soul和瓦格纳的状态方程的计算值在估计的实验误差范围内一致。在258 - 273 K范围内，在压力高达200 MPa的条件下，沿沿着三条等温线对未冻水进行了测量。所有测量值均符合Tait型方程。该方程能较好地再现未冻水的比容，误差小于0.02%。与前人工作的比较表明，在未冻区，实验数据与状态方程计算值的吻合程度比Bridgman的更好。

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.