Multiphase Modeling in ANSYS CFD - ANSYS - Simulation Driven PDF
Preview Multiphase Modeling in ANSYS CFD - ANSYS - Simulation Driven
Multiphase Models in ANSYS CFD Gilles Eggenspieler Senior Product Manager 1 © 2011 ANSYS, Inc. May 14, 2012 Which Reactor is Better? Depends! When gas dissolution is important Solid catalyst particles Higher hold up! Much better mixing! 2 © 2011 ANSYS, Inc. May 14, 2012 ANSYS CFD: A Platform for Modeling Multiphase Flows 3 © 2011 ANSYS, Inc. May 14, 2012 Introduction Multiphase flow involves the simultaneous flow of two or more immiscible interacting phases Many industrial processes involve multiphase flow • Gasoline sprays in automobile combustion engines •• GGaassiiffiiccaattiioonn aanndd ccooaall ccoommbbuussttiioonn iinn ppoowweerr ppllaannttss • Fluid catalytic cracking in refineries • Aeration in water treatment plants • Icing on aircrafts • And several others … 4 © 2011 ANSYS, Inc. May 14, 2012 Challenges Involving Multiphase Flows Engineering operations often involve “non-spontaneous” processes • Mixing -- Keep a mixture of components that separate naturally, mixed. Desire to improve contact between the phases to improve and enhance interfacial transfer processes •• SSeeppaarraattiioonn ---- NNeeeedd ttoo sseeppaarraattee ccoommppoonneennttss tthhaatt aarree ddiiffffiiccuulltt to separate, such as fine dust from flue gases Flow dynamics crucial to the efficiency of these processes Non-linear effect of parameters and geometry on processes 5 © 2011 ANSYS, Inc. May 14, 2012 Lower Dimensional Simulations Tools like Aspen, HYSYS, gProms • Quick • System wide simulation Need to be supplemented with detailed engineering analysis •• EEnnggiinneeeerriinngg aannoommaalliieess – Flow mal-distribution, hot spots, stress concentrations • Insights on off-design performance • Effect of geometry 6 © 2011 ANSYS, Inc. May 14, 2012 The Need for Detailed Simulations • Include all relevant phenomena • Effect of inlets, outlets, internals and other geometric details captured •• SSccaallee iinnddeeppeennddeenntt • Qualitative and quantitative information 7 © 2011 ANSYS, Inc. May 14, 2012 Appropriate Models for Multiphase Flow What is the engineering problem of interest? What is the flow regime? • Length scale of interface in relation to the domain? •• RReeggiimmee cchhaannggee?? Other important physics? • Impact of flow on size? • Heterogeneous and homogeneous reactions 8 © 2011 ANSYS, Inc. May 14, 2012 Modeling Multiphase Flows Length scale of equipment - L Length scale of flow that is resolved (mesh) – l Interfacial length scale (droplet or bubble size) – d • l >> d –– DDiissppeerrsseedd ffllooww – Droplets, bubbles or particles unresolved! – Need to model interactions (momentum, heat and mass) • l << d or d ≈ L – Separated flow – Interfacial interactions resolved as part of solution 9 © 2011 ANSYS, Inc. May 14, 2012 Separated or Dispersed? Bubble columns Fluidized beds 10 © 2011 ANSYS, Inc. May 14, 2012
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