A Microwave–Ultrasonic Cell for Sound-Speed Measurements in Liquids

Abstract

In this work preliminary results obtained in developing a prototype cylindrical ultrasonic cell designed to apply a microwave resonance technique to the determination of its internal dimensions are described. Since the apparatus is intended for speed-of-sound measurements in pressurized liquid-phase media, the cell design is such that a double reflector pulse-echo technique can be used for time-of-flight measurements. The main absorption and dispersion effects that influence the acoustic measurement in this interferometer-like configuration and the values of the corresponding corrections are considered and discussed. The performance of the experimental apparatus and method in terms of achievable precision and accuracy was tested by measuring the speed of sound in water on a single isotherm at 325 K between 0.1 and 90 MPa.KEY WORDS: microwave resonator; pulse-echo method; speed of sound.

An apparatus for the determination of speeds of sound in fluids

“…The spherical resonator has been used to obtain measurements with high accuracy in gases by Mehl and Moldover [3,4], Ewing et al [5], Trusler and Zarari [6], and Benedetto et al [7], whereas the pulse-echo technique is preferred for measuring the speed of sound in liquids and compressed gases at high pressure. Corresponding data were reported by Kortbeek et al [8], Ye et al [9], Wang and Nur [10], Zak et al [11], Benedetto et al [12], and Meier and Kabelac [13].…”

Ultrasonic Velocity and Density Studies of Solutions of Maleic Acid and Tartaric Acid in Water at T = (298.15 and 308.15) K

“…Ultrasonic velocities were measured by using a multifrequency ultrasonic interferometer (M-83, Mittal Enterprises, India) at 2 MHz. The ultrasonic interferometer was calibrated with triply distilled deionized water (conductivity, 0.054 μS · cm −1 [5] or resistivity, 18.18 M [6]). For measurement of ultrasonic velocities of aqueous solutions of maleic and tartaric acids at different temperatures, water at different temperatures was circulated through the measuring cell of the ultrasonic interferometer by a pump.…”

Thermodynamic Properties of Gases from Speed-of-Sound Measurements

“…For that purpose, the pressure range may be divided into a number of isobars. However, it is known that an interpolation polynomial estimates derivatives at the boundary points with lower accuracy than at intermediate points [13]. For that reason, in order to keep the number of these boundary points as low as possible (e.g., two), over the whole pressure range, the number of isobars should not be greater than the order of the interpolation polynomial plus one.…”

“…This approach was recently introduced for the liquid phase [13]. However, for the case of the gaseous phase, integration is performed with respect to temperature rather than pressure [14].…”