Clamp-on type ultrasonic flow meter and a temperature and pressure

Abstract

A ratio C of sonic speed in a fluid to a sinusoidal value at an incident angle of sonic waves from the pipe to the fluid is designated as a basic unknown quantity. A distance D between the opposite inner wall surfaces of the pipe, a thickness t.sub.p of the pipe wall, a projection length t.sub.w of sound rays in the oblique wedge projected onto a plane orthogonal to the center axis of the pipe, and sonic speed C.sub.w, C.sub.p in the oblique wedge and the pipe wall are used as given values. A propagation time .tau. of ultrasonic waves through the oblique wedge and the pipe wall is treated as a variable. The value C is determined in course of calculating a projection length L of sound rays between the ultrasonic transducers projected onto the center axis of the pipe by a gradual approximation, which is determined as a given value. Then, a refraction angle .theta..sub.f of sonic waves from the pipe wall to the fluid and a propagation time .tau. of ultrasonic waves through the oblique wedge of the ultrasonic transducer are determined based on the value C. These values and a propagation time of ultrasonic waves between the ultrasonic transducers obtained by a measurement are applied to a basic equation to derive a flow velocity of the fluid in the pipe at temperature and pressure under a service condition.