Computational fluid dynamics for chemical reactor design

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Computational fluid dynamics improve efficiencies in fluid flow, heat and mass transfer processes. Computational Fluid Dynamics is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. Computational fluid dynamics Found Its self in various industrial applications, Biomedical, Electronics, Defense, Industrial,Environmental, Civil and drug delivery systems

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Computational fluid dynamics for chemical reactor design

  1. 1. dynamics- for chemical reactor design Article written and published By www.worldofchemicals.com
  2. 2. Abstract  Computational fluid dynamics (CFD) is helping to generate millions of dollars of savings in chemical process applications. It gives process engineers a more complete understanding of the internal operation of individual unit operations.  As a result, some chemical and process companies are equipping their engineers with CFD software and investing in training to improve efficiencies in fluid flow, heat and mass transfer processes.  CFD uses computers to solve the fundamental nonlinear differential equations that describe fluid flow (the Navier- Stokes and allied equations) for predefined geometries with a set of initial boundary conditions, process flow physics and chemistry.  Recent advances in CFD have made it possible to analyze flow problems of ever-increasing complexity, including those involving multiphase flows, mixing-related phenomena, intricate equipment geometries and detailed chemically reacting flows within process-relevant time scales.  This article meant for explaining the future needs and expectations of the chemical processing industry with respect
  3. 3. Introduction  Computational Fluid Dynamics is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows. It is becoming a critical part of the design process for more and more companies. Computational  Fluid Dynamics makes it possible to evaluate velocity, pressure, temperature, and species concentration of fluid flow throughout a solution domain, allowing the design to be optimized prior to the prototype phase.  CFD modeling provides a good description of flow field variables, velocities, temperatures, or a mass concentration anywhere in the region with details not usually available through physical modeling. Once the basic model is established, parametric runs can usually be
  4. 4. Introduction Cont ..  CFD denotes collectively techniques solving equations describing the physics of flows. It is the art of replacing such Partial Differential Equation Systems by a set of algebraic equations which can be solved using digital computers. CFD became a research field in the late 1960s. First commercial CFD software appeared in the 1980s including codes like PHOENICS, FLUENT, STAR-CD, CFX, TASCFLOW, and FLOW3D.  It solves Euler, RANSE (Reynolds Averaged Navier-Stokes Equations) or Navier-Stokes equations.  Computational Fluid Dynamics provides a qualitative (and sometimes even quantitative) prediction of fluid flows by means of  Mathematical modeling (partial differential equations)  Numerical methods (discretization and solution techniques)  Software tools (solvers, pre- and post processing utilities)  Computational Fluid Dynamics enables scientists and engineers to perform ‘numerical experiments’ (i.e. computer simulations) in a ‘virtual flow laboratory’.
  5. 5. Reactor design  Chemically reacting flows are those in which the chemical composition, properties and temperatures change as the result of a simple or complex chain of reactions in the fluid. The reactor is typically simulated using a chemical-reaction model coupled with one of the following four fluid-modeling approaches  1. A perfectly mixed stirred tank (either batch, semibatch or continuous)  2. A plug-flow reactor  3. A network of a relatively small number of perfectly mixed and plug-flow reactors  4. A full CFD model.
  6. 6. Reactor design Cont ..  The calculation time is relatively short for the first three methods and such models may not assess the effects of the reactor hydrodynamics on its performance. Thermal nonuniformities may also accelerate reaction processes, and, in some cases, local hot spots may result in product decomposition, or even in thermal runaways or explosions.  These nonuniformities cannot be captured when modeling the reactor using simplified hydrodynamics assumptions (such as perfect mixing), but can be depicted with reasonable accuracy using full CFD models.  The chemical reactors which are architecture through CFD fluid-flow pattern and temperature fields can be calculated from conservation equations for mass, momentum and enthalpy.
  7. 7. Blue Ridge Numerics, Inc Case study  Blue Ridge Numerics, Inc. has recently launched their new CFdesign UVCalc Module, a CFD solution for simulating and validating ultraviolet (UV) reactor performance to ensure accurate fluence rates (irradiances) for UV light disinfection.  The use of germicidal UV light is a rapidly expanding technology that is used to ensure public safety by deactivating the DNA of bacteria, viruses, and other pathogens, removing their ability to multiply and cause disease.  With the new partnership of Blue Ridge Numerics, Inc. and Bolton Photosciences Inc., design engineers developing UV applications for drinking water disinfection, wastewater treatment, and manufacturing processes for the food and beverage, medical device, pharmaceutical, and semiconductors industries (among others), can now easily leverage fluid flow and UV calculation capabilities to speed up and optimize their product development process.
  8. 8. Case study Cont …  The Cfdesign UVCalc Module empowers engineers with CAD-driven simulation tools that optimize product performance during the digital design phase. The ability to validate UV reactor performance for biodosimetry testing, while still on the digital drawing board, is the focus of Cfdesign and the UVCalc Module. Exploration of multiple design scenarios before building prototypes for physical testing equates to significant cost and time savings.  The use of UV light disinfection is rapidly expanding around the world, especially in emerging countries like China and India where infrastructure is aggressively being developed to support population demands. As a result, companies will be looking for cost effective solutions to help more accurately design their products, and UVCalc with Cfdesign is intended to meet that need and more easily simulate and predict accurate reactor performance
  9. 9. CFdesign UVCalc Module Features  Determine the distribution of UV dose along various flow paths in the reactors and determine the impact of other factors, such as the flow rate, flow distribution, and axial mixing, all which can affect the fluence or UV dose and the performance of the reactor.  Run scenarios which include simulating the effect of inlet flow distribution changes (piping), different transmittance of the fluids, changes in flow rate or flow obstructions.  See side-by-side design comparison and data results of multiple reactor concepts through contour plots, cut planes, iso-surface, particle traces and vectors.  Providing the ability to explore a broad spectrum of possibilities to achieve an optimal design before proceeding with the very expensive and time consuming certification process.
  10. 10. Application areas  Biomedical  Electronics  Defense  Industrial  Environmental  Civil
  11. 11. Biomedical CFD Applications  Flow modeling with computational fluid dynamics (CFD) software lets you visualize and predict physical phenomena related to the flow of any substance. It is widely used in medical, pharmaceutical, and biomedical applications to analyze  Manufacturing Processes,  Device Performance,  Physiological Flows,  Fluid-Structure Interactions,  The Effectiveness of drug delivery systems
  12. 12. Electronic CFD Applications  The Ansys' flagship CFD software, ANSYS-FLUENT, as well as the electronics industry custom- designed ANSYS-ICEPAK suite, offer high-performance electronics cooling solutions covering a wide range of real life problems on any level  Component,  Board,  Package,  System
  13. 13. Defense CFD Applications  Ansys Computational Fluid Dynamics predict how the toxins spread through space and time, dam breaks, the collapse of storage tanks and blast waves associated with explosions or sudden gas leaks.  It also plays a vital part in the design of prevention systems, such as sensors, detectors, portals, and screening devices, to design personal protection equipment, especially masks, suits, to assess the human exposure levels near the attack site, such as estimating the spread of particulates that resulted from the collapse of the Twin Towers, to plan fumigation procedures for buildings.
  14. 14. Industrial CFD Applications  Ansys Computational Fluid Dynamics software predicts fluid flow, heat transfer, and chemical reactions, to optimize, improve equipment, processes and plants, providing financial savings, for processing of industrial minerals, the recovery of precious stones, ore treatment, polymer extrusion, film casting, coating, fiber spinning, thermoforming and blow molding.
  15. 15. Environmental CFD Applications  Ansys Computational Fluid Dynamics is used to design proposals, avoiding the added costs of over sizing and over specification, while reducing risk.  Civil & Other CFD Applications  Ansys Computational Fluid Dynamics flow modeling solutions, you can visualize the complex airflow and thermal performance of data centers.
  16. 16. Conclusion  CFD is already gaining importance in the industry. Some of the companies reaping benefits of the technology are 3M; Air Products; Argonne National Lab; Bechtel; BP Amoco; Chemineer ; Chevron; Cray; Dow Chemical; Dow Corning; DuPont; Eastman Chemical; Eli Lilly; Huntsman; LIGHTNIN; Mitsubishi Chemical-US; NETL ;Nalco Chemical; Fuel Tech; National Institute of Standards & Technology; Phillips Petroleum; Procter & Gamble; Rohm & Haas; Shell Oil-US; UOP; Fuji Xerox Co., Ltd.  The above companies have integrated CFD technology into their design process, which leads to a shortened product-process development cycle, optimization of existing processes, reduced energy requirement, product cost and efficient design of new products and processes. For instance, Fuji Xerox Co Ltd utilizes computational fluid dynamics for designing branched exhaust ducts, optimizing the volume of air suctioned in from each inlet of the exhaust duct, to cool down, and collect dust inside the machine.  Reviewing the chemical reactor design by CFD technology, it is obvious that CFD can offer a great potential for the chemical engineering processes.CFD is the combination of physics, flow technology, computer applications, mathematics and mechanics. It has already made a deep impact on chemical reaction engineering due to its feasibility. Further, it is expected that the role of CFD in the future design of chemical reactors will increase substantially and it w
  17. 17. Reference  1] Franz Zdravistch and Ahmad Haidari, Virtual Fluid Dynamics, Available from- http://www.chemicalprocessing.com/articles/2003/69.html?page=2  [2] L. Oshinowo, L. Gunnewiek, K. Fraser, CFD in Autoclave Circuit Design, Hydrometallurgy 2003 - Proceedings of the 5th International Symposium; August 2003, Available from -  http://www.hatch.ca/engineering/sead/cfd/articles/cfd_autoclave_circuit_design.htm  [3] M. R. de Leval, MD, FRCSa, G. Dubini, PhDc, F. Migliavaccac, H. Jalali, MDa, G. Camporinia, A. Redingtonb, R. Pietrabissa, PhD, Use of computational fluid dynamics in the design of surgical procedures application to the study of competitive flows in cavopulmonary connections, J Thorac Cardiovasc Surg 1996;111502-513, Available from - http://jtcs.ctsnetjournals.org/cgi/content/abstract/111/3/502  [4] C K Harris, D Roekaerts F J J Rosendal, F G J Buitendijk, Ph Daskopoulos, A J N Vreenegoor, H Wang, Koninklijke Sheli-laboratorium, Computational Fluid Dynamics for Chemical Reactor Engineering, Volume 51, Issue 10, Publisher Elsevier, Pages 1569-1594, Available from- http://www.mendeley.com/research/computional-fluid-dynamics-chemical- reactor-engineering/#  [5] Ahmad H. HAIDARI and Brent MATTHEWS, Future trends for computational fluid dynamics in the process industry, Third international conference on CFD in the mineral and process industries,10-12 December 2003, Available from - http://www.cfd.com.au/cfd_conf03/papers/114Hai.pdf  [6] J.A.M Kuipers and W.P.M. van Swaaij, COMPUTATIONAL FLUID DYNAMICS to CEHMICAL REACTION ENGINEERING, Available from - http://doc.utwente.nl/12954/1/K301____.PDF  http://www.worldofchemicals.com/11/chemistry-articles/computational-fluid-dynamics- for-chemical-reactor-design.html  Image Reference  Fig. © From http://www.rdmag.com/Module-assists-CFD-for-UV-reactors/

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