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research-article

Trial for Monitoring the Water Temperature Utilizing the Frequency Dependence of Reflection Coefficient of Ultrasound Passing through Thin Layer

[+] Author and Article Information
Hironori Tohmyoh

Aoba 6-6-01, Aramaki, Aoba-ku, Sendai, 980-8579 Japan tohmyoh@ism.mech.tohoku.ac.jp

Shu Terashima

Aoba 6-6-01, Aramaki, Aoba-ku Sendai, Miyagi 980-8579 Japan mcnkc6222@gmail.com

1Corresponding author.

Manuscript received August 13, 2018; final manuscript received February 9, 2019; published online xx xx, xxxx. Assoc. Editor: Fabrizio Ricci.

ASME doi:10.1115/1.4042871 History: Received August 13, 2018; Accepted February 12, 2019

Abstract

This paper describes a new concept to monitor the temperature of water utilizing the acoustic resonance, which occurs when ultrasound passes through a thin layer. In the ultrasonic transmission system that comprises of the reflection plate, thin film and water, the reflection coefficient of the ultrasound at the plate/film/water interface depends on the frequency, and takes its minimum value at the resonant frequency. Notably, this is closely related with the acoustic impedance of the water; moreover, it is a known fact that the acoustic impedance of the water demonstrates temperature dependence. Against this background, the present study aims to develop a technique in order to monitor the temperature of water utilizing the aforementioned correlation between the reflection coefficient and water temperature. Firstly, a theoretical model was developed to determine the acoustic impedance of water from the difference in the amplitude spectra of echoes reflected at the back of the plate in the cases both with and without the film. It was found the ratio of the amplitude spectrum of the echo recorded in the case with the film to that in the case without the film clearly declined with a drop in water temperature. From this, we obtained the equation to determine water temperature experimentally. Finally, the temperature of water, which was brought down by air or ice cooling, was monitored by the proposed method. It was found that the behavior of temperature determined by the proposed method was congruent with that which was measured by a thermocouple.

Copyright © 2019 by ASME
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