PNNL

Abstract

Ultrasonic signals can interrogate many two-phase systems, dense slurry-laden and three-phase suspensions. Ultrasonic signal reflection at a fluid-sensor interface is used to characterize fluid and slurry density and viscosity. The sensor consists of a series of transducers mounted on a wedge with the base of the wedge in contact with the liquid. Ultrasonic beams, striking the wedge base at several angles, are reflected at the base-liquid interface to the receive transducers. The amount of reflection at this interface depends upon the density of the liquid, the speed of sound in the liquid, and the wedge parameters. The response of a shear wave transducer, in conjunction with a density measurement, is used to determine the viscosity. A pipeline probe with the sensing element located in the pipe wall flush with the pipe bore has been demonstrated for process measurement in industrial and harsh environments. The probe was evaluated using physical simulants in a test loop to measure liquid and slurry densities in the range from 1000 to 1500 kg/m3. During these tests, density samples were extracted to permit independent density measurements. Measurements of viscosity conducted with similar slurries show that the sugar water solutions and the slurries are characterized by the theory for light liquids, in which the reflection coefficient is a measure of the product of the density and viscosity of the liquid. Therefore, this technique can be applied to measure the viscosity of water-based solutions and slurries and can be used for real-time process monitoring during processing for many industrial processes. The sensor can be mounted in a pipeline configuration or submerged in a tank for process control. Novel features include: the small size of the probe and the sensor robustness. Performance is not affected by fluid flow rate, entrained air, or vibration. Experimental measurements of the density and viscosity for fluids and slurries are presented.