In-line visualization and on-line characterization of nontransparent fluids becomes an important subject for process development in food and nonfood industries. In our work, a noninvasive Doppler ultrasound-based technique is introduced. Such a technique is applied for investigation of nonstationary flow in the chocolate precrystallization process. Unstable flow conditions were induced by abrupt flow interruption and were followed up by strong flow pulsations in the piping system. While relying on available process information, such as absolute pressures and temperatures, no analyses of flow conditions or characterization of suspension properties could possibly be done. It is obvious that chocolate flow properties are sensitive to flow boundary conditions. Therefore, it becomes essential to perform reliable structure state monitoring and particularly in application to nonstationary flow processes. Such flow instabilities in chocolate processing can often lead to failed product quality with interruption of the mainstream production. As will be discussed, a combination of flow velocity profiles, on-line fit into flow profiles, and pressure difference measurement are sufficient for reliable analyses of fluid properties and flow boundary conditions as well as monitoring of the flow state. Analyses of the flow state and flow properties of chocolate suspension are based on on-line measurement of one-dimensional velocity profiles across the flow channel and their on-line characterization with the power-law model. Conclusions about flow boundary conditions were drawn from a calculated velocity standard mean deviation, the parameters of power-law fit into velocity profiles, and volumetric flow rate information.
The rheology of a fluid flowing in an industrial process pipe can be calculated by combining the pressure drop and the velocity profile that the fluid develops across the tube diameter. The profile is obtained non-invasively through an ultrasound Doppler investigation. Unfortunately, at present, no system capable of real-time velocity profile assessment is available for in-line industrial rheological measurements, and tests are operated by manually moving fluid specimens to specialized laboratories. In this work we present an embedded system capable of in-line and realtime measurement of velocity profile and pressure drop, which enables the automatic rheological characterization of non-Newtonian fluids in process pipes. The system includes all the electronics for the ultrasound front-end, as well as the digital devices for the real-time calculation of the velocity profile. The proposed system is high programmable, low-noise and specifically targeted for industrial use. It is shown capable of producing, for example, 512-point velocity profiles at 45 Hz rate. An application is presented where a sludge fluid, flowing at 600 L/min in a 48 mm diameter high-grade stainless steel pipe, is characterized in real-time with a ±5% accuracy.
The continuous monitoring of rheological parameters of industrial fluids during production is of paramount importance for process and quality control. Up to now, no system capable of a complete and non-invasive in-line measurement is commercially available, so that only time discrete laboratory measurements on fluids specimens are possible. In this work a new, fully integrated ultrasound system for in-line fluid characterization, named Flow-Viz, is presented. The system measures the velocity profile of the fluid moving in a pipe through pulsed Doppler ultrasound, and combines it with the pressure drop. The electronics, featuring two ultrasound transmission/reception channels used alone or in pitch-catch configuration, includes powerful digital processing capabilities for real-time velocity profile calculation, and is fully programmable. Particular attention is paid to low-noise design for achieving the optimal performance in highly attenuating suspensions. An application is presented where the system, coupled to a non-invasive ultrasound sensor unit, performs in-line rheological measurements through the wall of a high-grade stainless steel pipe.
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