Effect of incident angle on ultrasonic transmission in steam flow for use with clamp-on ultrasonic flowmeter

Abstract

For energy management in industrial plants, it is important to monitor actual consumption of steam in each usage place. In order to measure the steam flow rate in existing pipes, clamp-on ultrasonic flowmeter is one of the effective solution. The ultrasonic flowmeter calculates the transit-time of ultrasonic between downstream and upstream sensors which is affected by the line-averaged velocity along the ultrasonic beam. In order to measure the steam flow rate using the clamp-on ultrasonic flowmeter, the intensity of the transmitted ultrasonic signal is one of the key issues. In this study, we focus on the effect of the ultrasonic incident angle on the transmitted ultrasonic signal intensity in steam flow. The results showed that appropriate incident angle changes depending on the pipe wall thickness, and the Lamb wave was useful for increasing the signal intensity. With increase of the steam velocity, the transmitted signal intensity decreases because of the turbulent dissipation. In order to evaluate the transit-time difference between upstream and downstream sensors, it is important to set the sensors at an appropriate incident angle depending on the wall thickness particularly for higher steam flow rate.