404589 Modeling Distributed-Parameter Mixing Processes Using Computational Fluid Dynamics and z-Transform

Tuesday, November 10, 2015: 1:33 PM
Salon H (Salt Lake Marriott Downtown at City Creek)
De-Wei Yin, Engineering & Process Science Laboratory, Fluid Mechanics & Mixing Discipline, The Dow Chemical Company, Midland, MI

Computational fluid dynamics (CFD) has become a widely used method for analyzing the performance of mixing unit operations in the chemical process industry. Results of these simulations can yield useful insights into a mixing process. Repeated CFD simulations to capture the dynamic behavior of the same mixing process set-up under different sets of boundary conditions can, however, demand significant computational resources and present a practical challenge to practitioners.

We have previously illustrated how the combination of CFD with the z-transform technique provides a convenient approach to analyzing the open-loop response of a lumped-parameter process. Using a continuous stirred-tank reactor as an example, we showed that the simpler z-transform model has excellent accuracy and relatively low computational cost requirements (Yin and Yu, AIChE 2015 Paper 354913). In our current presentation, we extend this methodology to the analysis of distributed-parameter mixing processes where multiple physics and spatial heterogeneity may manifest in the system. One example of such a system is a stirred-tank coupled with heat transfer through the vessel wall. Using the results of an initial CFD simulation we derive a z-transform model which can then be inverted to give the dynamic response of the mixing process for any arbitrary perturbation. We compare the results obtained from the z-transform model against results of CFD simulations to demonstrate the accuracy of this approach and savings in computational cost, and discuss the sources of error and the limitations of this method.

Extended Abstract: File Not Uploaded
See more of this Session: The Use of CFD in Simulation of Mixing Processes
See more of this Group/Topical: North American Mixing Forum