Ultrasonic waveguide-based distributed temperature measurement on a solid surface

Abstract

This paper describes a novel technique for the simultaneous measurement of the temperature of solid structures at multiple locations using a single transducer attached to a single bent waveguide with axisymmetric notches. This technique improves upon earlier reported studies using straight waveguides and bent waveguides without notches, where the lack of consideration for the effect of temperature gradients was found to be a significant limitation. This work also describes the L(0,1) and T(0,1) mode transmission and reception in the bent waveguide for selecting an appropriate gauge length for the waveguide sensor. The range of temperature measurement is from room temperature to the maximum utility temperature of the pipe structure in a process industry. The change in time-of-flight of the reflected ultrasonic signal from the waveguide features (bend and notch) is used to measure the local temperature of the surrounding media. This work is of interest in several industrial applications, including the petrochemical and nuclear industries.