Determination of the acoustic nonlinearity parameter in liquid water up to 250°C and 14 MPa

This work reports, for the first time, the direct measurement of sound speed in liquid water at temperatures up to 250°C and pressures up to 14 MPa. These measurements enabled the determination of the acoustic nonlinearity parameter, B/A, an important property of liquids. From an applications perspective, B/A determines the efficiency of devices that are based on acoustic nonlinear mixing. The objective of the present work was to use a specialized measurement cell for sound speed measurements and the determination of B/A in liquid water as a function of temperature and pressure. Sound speed was measured using Swept Frequency Acoustic Interferometry, while B/A was determined from the derivatives of the sound speed with respect to pressure and temperature. B/A at ambient pressure and temperature was determined to be 4.8, in good agreement with literature values. At 250°C and 14 MPa, B/A was found to be roughly twice its ambient temperature value.