The thermal diffusivity of water at high pressures and temperatures

Thermal diffusivities of fluid water have been measured to a pressure of 3.5 GPa, a density of 1.4 g cm-3 and a temperature of 400 degreesC. Above 100 degreesC, both the diffusivities and the related conductivities are found, unexpectedly, to scale as the square-root of absolute temperature; in contrast, the excess conductivities are highly dependent on temperature. Measurements at 25 degreesC, extending into a metastable regime with respect to ice VI, do not scale in this manner and this anomalous behavior is not suppressed by pressures up to 1.3 GPa. (C) 2001 American Institute of Physics.