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. However, it is difficult to accurately measure the steam flow rates because of the large acoustic impedance difference between the pipe material and fluid, signal attenuation in the fluid, and high temperature. Hence, in this study, a new signal processing method using standard deviation of the target signal of the transmitted ultrasonic is proposed. Ultrasonic transmission experiments were carried out in air-water two-phase and saturated steam flows. Two ultrasonic sensors located at up- and down-stream positions were used for the measuring ultrasonic time-of-flight that depends on the flow rate. In air-water two-phase flows, it was shown that flow rate measurements were difficult with increasing of the flow velocity and the wetness fraction. However, the transit time difference of the ultrasonic signals transmitted from the upstream and downstream transducers could be accurately obtained using the proposed method. Furthermore, distributions of the standard deviation were influenced with the flow conditions. Uniqueness shape of the target signal in the standard deviation were also confirmed in the steam flow conditions. Thus, it implies that the proposed method is useful for measuring steam flows.
