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331703 Application of Discrete Tangent Based Sensitivity Analysis to Computation of Reacting Flows
331703 Application of Discrete Tangent Based Sensitivity Analysis to Computation of Reacting Flows
Wednesday, November 6, 2013
Grand Ballroom B (Hilton)
Reactors and flow processes involving chemical reactions are often governed by many operating parameters such as the inlet and exit flow rates, compositions, reaction mechanisms, rate constants, pressures, and temperatures. In most systems many of these parameters influence the system in complicated and interconnected manner. It often requires generating, gathering, and analyzing design data from a large number of simulations or experiments to determine and quantify the critical parameters that govern the performance and their range of influence.
CFD simulations have become a vital tool to study, design, and optimize the equipment and processes concerned with reactive flows. These analyses provide details spatial and temporal detail of the conditions in the system helping to make informed decisions regarding improving or optimizing the performance. However, CFD simulations usually are also time consuming and expensive to perform especially when a large number of parameters are involved.
The study applies discrete tangent based CFD simulation methodology for reacting systems in a tubular reactor that provides the sensitivity of the solution to variations in input parameters in single simulation. Unlike traditional CFD approaches that require multiple single-point simulations to derive the sensitivity map of the solution to a given input parameter, this approach enables computation of the sensitivity along with the single-point solution. In this implementation, the derivatives of any input parameter (referred to as the sensitivity parameter) are propagated through the entire solution algorithm, so that derivatives of all computed quantities with respect to the sensitivity parameter are determined. Information about the dependence on input parameters is available not only for reduced quantities such as performance metrics, but also for entire fields, and this can be very valuable in providing visual insight into the problem. This sensitivity analysis methodology is orders of magnitude less expensive and quicker than the conventional multiple simulation approach given that it requires fewer simulations fill in the sensitivity map of the design space.
The work presents investigation of a Plug Flow Reactor (PFR) system and an industrial tubular reactor having multiple inlet streams. The Eddy-Dissipation Model (EDM) and the Eddy Dissipation Concept (EDC) models are used to compute the reaction rates, and the k-epsilon model is used to model turbulence. The results for the sensitivity of the flow and temperature profiles and the outlet stream concentration to input parameters such as the inlet flow rate, the inlet feed composition and the inlet temperature are presented. Results include the solution fields (or derived quantities) at the specified value of the sensitivity parameter (computed value), the gradient of the solution field with respect to this sensitivity parameter (derivative), and the extrapolated value of the field about the specified value of sensitivity parameter. The sensitivity results will be compared with results obtained from multiple single-point simulations using traditional CFD solvers. The work also quantifies the time saved to obtain the range of sensitivity data for this demonstrative reactor flow compared to the conventional CFD methods.
See more of this Session: Poster Session: Catalysis and Reaction Engineering (CRE) Division
See more of this Group/Topical: Catalysis and Reaction Engineering Division
See more of this Group/Topical: Catalysis and Reaction Engineering Division