Using Electrical Resistance Tomography Images to Analyze the Batch and Continuous-Flow Mixing of Pseudoplastic Fluids Possessing Yield Stress in the Agitated Tanks
Non-ideal flows, such as dead zones and channeling, are commonly occurred in the mixing of nonNewtonian fluids possessing yield stress. It is a challenging task to visualize such phenomena occurring inside the mixing vessels due to the opacity of the fluids. Numerous conventional techniques have been used to study the mixing operations in both batch and continuous modes; however, these techniques have their own limitations as they are not suitable for opaque fluids or they might interfere with the local flow pattern. Therefore, the core objective of this study was to employ electrical resistance tomography (ERT), which is an efficient and nonintrusive flow visualization technique for both opaque and transparent fluids, to study the batch and continuousflow mixing of non-Newtonian fluids possessing yield stress in a stirred vessel. In this study the ERT technique was employed to: (i) measure the mixing time in the batch mode, (ii) measure the cavern size in the batch mode, (iii) analyze the cavern deformation in the continuous mode, and (iv) visualize the flow pattern generated by the impeller inside the stirred tank in the continuous mode. The 2D and 3D tomography images were used to identify the existence of the non-ideal flows encountered inside the mixing vessel. The ERT data were also used to validate the CFD model. Applying the outcomes of this research can enhance the design criteria of the mixing of nonNewtonian fluids in both batch and continuous modes.
X-ray studies of cavern sizes and mixing performance with fluids possessing a yield stress
Abstract The use of an X-ray—heavy metal tracer method for the study of mixing patterns in opaque fluids in agitated vessels is described. The heavy metal tracer (Ba or Pb) used is added either in solution or in particulate form and its motion observed on X-ray cine film. This paper also reports the application of this general technique to the study of the flow patterns and cavern sizes during the mixing of opaque fluids exhibiting yield stresses. The cavern sizes measured are compared with the fluids' rheology by a simple extension of a previous model, and good agreement is found. A short motion picture of the caverns and flow patterns has been made.
Complex Systems Architecture Framework: Extension to Multi-objective Optimization
This paper shows the utility to follow an architecture framework in order to design complex systems with a holistic approach. Multi-objective Optimization techniques extend and complete the architecture framework to support trade-off analysis and decision making in the Systems Engineering design process. The merging and combination of these two approaches, decision making and systems engineering, contribute to the efficient design of systems by helping to meet needs and constraints stemming mainly from the system analysis.