(368e) Deconstruction of Mixing Processes Using Computational Fluid Dynamics and Z-Transform | AIChE

(368e) Deconstruction of Mixing Processes Using Computational Fluid Dynamics and Z-Transform

Authors 

Yin, D. W. - Presenter, The Dow Chemical Company
Computational fluid dynamics (CFD) is used in studying the performance of mixing processes to complement experimental work by making accessible to the investigator measurements that are difficult to obtain physically. Motivated by the desire to enhance the modeling toolset, we have in recent years demonstrated the use of CFD with z-transform, the discrete-time counterpart of the Laplace transform, to provide a powerful approach for simulating and analyzing the dynamics of mixing processes. Examples that we have illustrated include the open-loop response of a lumped-parameter mixing process, the open-loop response of a distributed-parameter mixing process, the closed-loop response of an unstable mixing process, and the general characterization of mixing processes [AIChE Annual Meeting Papers 2014-354913, 2015-404589, 2016-449915, and 2017-486416].

By the conventional approach, continuous-flow mixing processes are typically modeled as ideal continuous stirred-tank reactors (CSTR) or plug-flow reactors (PFR), or combinations thereof. Real mixing processes, however, do not conform perfectly to the CSTR and PFR paradigm. In order to optimize real mixing processes or to troubleshoot problematic ones, it is desirable to transcend beyond the CSTR and PFR blackbox approach and describe the dynamic behavior of the nonideal mixing processes more accurately. In this presentation we extend our previous work on combining CFD and z-transform and demonstrate how one can deconstruct nonideal mixing processes into networks of smaller and simpler mixing and transport processes. The result allows us to identify and construct practical mathematical models that capture localized phenomena such as compartmentalization and short-circuiting in nonideal mixing processes.