Development of a Non-Intrusive In-Line Tomographic Ultrasonic Velocity Meter to Measure Liquid Rheology

The number of chemical processes transferred from a batch-wise approach to continuous flow is increasing, due to several advantages of continuous over batch: processes can be operated at more extreme conditions, resulting in higher speed and efficiency. Thus it is critical to evaluate key performance indicators real-time and in-line. For fluid handling processes like mixing and filling, the viscosity of the process fluid is a critical parameter. Also, for non-Newtonian fluids the viscosity varies with the shear rate. Hence the measured rheology is affected by intrusive sensor designs. Moreover, in view of fouling prevention and safety, the pipe wall should not be punctured. We propose a new concept to measure the viscosity as a function of shear rate by measuring the liquid velocity profile in and the pressure drop over the sensor. The concept is in-line, real-time, does not puncture the pipe wall and is non-intrusive. Here, we report on the development and performance of the tomographic ultrasonic velocity meter, which is part of said concept. The device consisted of 9 transducers distributed along the outer surface of a pipe. Tomographic time delay inversion was used to extract the liquid velocity profiles. The performance of the entire measurement chain was predicted using simulations. The transfer functions and acoustic wave fields were measured using a hydrophone setup. The device was tested with water and a high viscosity Newtonian liquid. The sensor successfully measured liquid velocity profiles.