A new setup for speed of sound measurements and experimental data for nanofluids Al₂O₃ or Ag with water or ethylene glycol

The speed of sound of four different nanofluids consisting of Ag or Al₂O₃ nanoparticles and water or ethylene glycol base fluid is measured in the temperature range (298.15–343.15) K and at atmospheric pressure. One aim of this analysis is to learn whether the change from pure base fluid speed of sound to the nanofluid situation is a smooth or disruptive transition when adding nanoparticles. The measurements were conducted on the newly proposed apparatus consisting mainly of function generator, ultrasonic sensor, switch, voltage source, oscilloscope, ultrasonic container and the necessary sensors and equipment for data acquisition. The values for speed of sound were calculated based on the Time of Flight method. Deionised water and ethanol were used to calibrate the apparatus which is additionally tested with pure base fluids water and ethylene glycol and showed excellent agreement with average absolute percentage deviations between experimental and literature data for speed of sound of 0.12% and 0.36%, respectively,. Beside the temperature influence, the influence of the nanoparticle concentration on the speed of sound of nanofluid were investigated and followed. The analysis of the sound velocity allows insight into the molecular level interactions taking place between the nanoparticles and the base fluid molecules of the nanofluid. The decrease in velocity values with the increase of concentration, noticeable in the tested nanofluids, is a result of decrease in nanoparticle-fluid interaction and dominance of particle–particle interaction.