02104nas a2200241 4500008004100000022001400041245011200055210006900167260010600236300001400342490000700356520122600363653001001589653000801599653000701607653002001614653001901634100002001653700002101673700001901694700002201713856012701735 2005 eng d a0009-250900aGas-liquid flow generated by a Rushton turbine in stirred vessel: CARPT/CT measurements and CFD simulations0 aGasliquid flow generated by a Rushton turbine in stirred vessel  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcAPR a2215-22290 v603 a

In this work, computer-automated radioactive particle tracking (CARPT), computed tomography (CT) and computational fluid dynamic (CFD) based models were used to investigate gas-liquid flow generated by a Rushton turbine. CARPT and CT measurements were carried out in a gas-liquid stirred vessel operating in two different flow regimes and captured the quantitative Eulerian information of gas-liquid flow. The CARPT data was then used to extract the circulation tune distribution in a vessel. A two-fluid model along with the standard k-epsilon turbulence model was used to simulate the dispersed gas-liquid flow in a stirred vessel. Appropriate drag corrections to account for bulk turbulence (along the lines proposed by Brucato et al. (Chem. Eng. Sci. 45(1998) 3295)) were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). Most model predictions compared favourably with CARPT and CT measurements. Validated CFD models as attempted in this paper are promising to simulation of industrial stirred vessels. (c) 2005 Elsevier Ltd. All rights reserved.

10aCARPT10aCFD10aCT10agas-liquid flow10astirred vessel1 aKhopkar, A., R.1 aRammohan, A., R.1 aRanade, V., V.1 aDudukovic, M., P. uhttps://library.ncl.res.in/content/gas-liquid-flow-generated-rushton-turbine-stirred-vessel-carptct-measurements-and-cfd-002393nas a2200241 4500008004100000022001400041245009200055210006900147260010600216300001400322490000700336520152900343653000801872653001701880653001101897653002601908653001901934100002001953700002101973700001901994700001902013856011902032 2006 eng d a0009-250900aCFD simulation of mixing in tall gas-liquid stirred vessel: role of local flow patterns0 aCFD simulation of mixing in tall gasliquid stirred vessel role o aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcMAY a2921-29290 v613 a

In this work, we have used the computational fluid dynamics (CFD)-based models to investigate the gas-liquid flows generated by three down-pumping pitched blade turbines. A two-fluid model along with the standard k-epsilon turbulence model was used to simulate the dispersed gas-liquid flow in a stirred vessel. Appropriate drag corrections to account for bulk turbulence [Khopkar and Ranade, 2005. CFD simulation of gas-liquid flow in a stirred vessel: VC, S33 and L33 flow regimes. A.I.Ch.E. Journal, accepted for publication] were developed to correctly simulate different flow regimes. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT4.5 (of Fluent. Inc., USA). The computational model has successfully captured the flow regimes as observed during experiments. The particle trajectory simulations were then carried out to examine the influence of the different flow regimes on the circulation time distribution. The model predictions were verified by comparing the predicted results with the experimental data of [Shewale and Pandit, 2006. Studies in multiple impeller agitated gas-liquid contactors. Chemical Engineering Science 61, 489-504]. The computational model and results discussed in this study would be useful for explaining the implications local flow patterns on the mixing process and extending the applications of CFD models for Simulating large multiphase stirred reactors. (c) 2005 Elsevier Ltd. All rights reserved.

10aCFD10aFlow regimes10amixing10apitched blade turbine10astirred vessel1 aKhopkar, A., R.1 aKasat, Gopal, R.1 aPandit, A., B.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-mixing-tall-gas-liquid-stirred-vessel-role-local-flow-patterns-102910nas a2200241 4500008004100000022001400041245009800055210006900153260009900222300001200321490000700333520203200340653000802372653002902380653001402409653002102423653001802444100002402462700002002486700001902506700001902525856012402544 2006 eng d a0950-423000aCFD simulation of shortstopping runaway reactions in vessels agitated with impellers and jets0 aCFD simulation of shortstopping runaway reactions in vessels agi aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcNOV a570-5810 v193 a

Runaway reactions are continuing to be a problem in the chemical industry. A recent study showed that 26% of our major chemical plant accidents are due to runaways. The consequences of runaway reactions are usually mitigated with (a) reliefs and containment systems or (b) shortstopping (reaction inhibition). This study covers the concept of shortstopping. One of the major reasons for runaways is power failure. In the advent of a power failure, mixing an inhibiting agent with the reactor contents is challenging. However, jets or impellers driven by a small generator can be used for mixing. This study compares shortstopping results in vessels agitated with jets and impellers using computational fluid dynamics (CFD). A commercial CFD code, Fluent is used. For shortstopping systems relying on jet mixing, angle and diameter of jet nozzle and jet velocity are the key design/operating parameters. For the systems with impellers, type, size and RPM of impeller are the key parameters. In this work, mixing with a jet mixer is first investigated for three nozzle diameters and two angles of injection. The best jet mixer configuration on the basis of mixing time is used for shortstopping studies. The simulated shortstopping results with the jet mixer are then compared with those obtained with impeller (Rushton and pitched blade turbine) stirred vessels. Our results identify the conditions for effective shortstopping; i.e., agitation requirements, locations for adding the inhibitor, and the quantity of inhibitor. The distribution of excess inhibitor is shown to be an important and essential design criterion for effective shortstopping when using impeller stirred vessels. The comparative study with a single jet shows that jet mixer is ineffective when used for shortstopping. Efforts such as adding excess inhibitor and inhibition with higher reaction rates at the same power, proved to be ineffective when using jet mixer compared to the results with impellers. (C) 2006 Elsevier Ltd. All rights reserved.

10aCFD10aimpeller stirred vessels10ajet mixer10arunaway reaction10ashortstopping1 aDakshinamoorthy, D.1 aKhopkar, A., R.1 aLouvar, J., F.1 aRanade, V., V. uhttps://library.ncl.res.in/content/cfd-simulation-shortstopping-runaway-reactions-vessels-agitated-impellers-and-jets-001979nas a2200229 4500008004100000022001400041245007400055210006900129260010600198300001400304490000700318520117900325653000801504653001101512653002101523653002001544100002101564700002001585700001901605700002001624856010501644 2008 eng d a0009-250900aCFD simulation of liquid-phase mixing in solid-liquid stirred reactor0 aCFD simulation of liquidphase mixing in solidliquid stirred reac aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcAUG a3877-38850 v633 a

A comprehensive CFD model was developed to gain an insight into solid suspension and its implications on the liquid-phase mixing process in a solid-liquid stirred reactor. The turbulent solid-liquid flow in a stirred reactor was simulated using a two-fluid model with the standard k-epsilon. turbulence model with mixture properties. The multiple reference frames (MRFs) approach was used to simulate impeller rotation in a fully baffled reactor. The computational model with necessary sub-models was mapped on to a commercial solver FLUENT 6.2 (of Fluent Inc., USA). The predicted solid concentration distribution was compared with the experimental data of Yamazaki et al. [ 1986. Concentration profiles of solids suspended in a stirred tank. Powder Technology 48, 205-216]. The computational model was then further extended to simulate and understand the implications of the suspension quality on liquid-phase mixing process. The computational model and the predicted results discussed here will be useful for understanding the liquid-phase mixing process in stirred slurry reactors in various stages of solid suspension. (c) 2008 Elsevier Ltd. All rights reserved.

10aCFD10amixing10asolid suspension10astirred reactor1 aKasat, Gopal, R.1 aKhopkar, A., R.1 aRanade, V., V.1 aPandita, A., B. uhttps://library.ncl.res.in/content/cfd-simulation-liquid-phase-mixing-solid-liquid-stirred-reactor-0