02392nas a2200241 4500008004100000022001400041245009200055210006900147260010600216300001400322490000700336520152900343653000801872653001701880653001101897653002601908653001901934100002001953700002101973700001901994700001902013856011802032 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. uhttp://library.ncl.res.in/content/cfd-simulation-mixing-tall-gas-liquid-stirred-vessel-role-local-flow-patterns-101978nas a2200229 4500008004100000022001400041245007400055210006900129260010600198300001400304490000700318520117900325653000801504653001101512653002101523653002001544100002101564700002001585700001901605700002001624856010401644 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. uhttp://library.ncl.res.in/content/cfd-simulation-liquid-phase-mixing-solid-liquid-stirred-reactor-002786nas a2200265 4500008004100000022001400041245012200055210006900177260010600246300001400352490000700366520179500373653002202168653001802190653003002208653001102238653002002249653001502269653002202284100002502306700002702331700001602358700002102374856012502395 2008 eng d a0009-250900aIdentification and characterization of flow structures in chemical process equipment using multiresolution techniques0 aIdentification and characterization of flow structures in chemic aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcNOV a5330-53460 v633 a

Planar information of velocity from 2D particle image velocimetry (PIV) and large eddy simulation (LES) data have been studied using multiresolution wavelet transform (WT) formalisms, i.e., discrete and continuous WT. Identification of dominant energy containing structures with their characterization in terms of fractal spectra have been carried out for industrially important equipment exhibiting turbulent behavior. These include annular centrifugal contactor, jet loop reactor, ultrasound reactor, channel flow, stirred tank and bubble column reactor. The characterization of their dynamics based on denoising the data and studying the local energy along the WT scales show sensitive variation and this helps in identifying the size and shape of structures. A dependency is seen between mixing time and the higher order moments of length scale distribution, viz., skewness and kurtosis and a generalized correlation has been built up for important types of equipment and associated flow parameters. The correlation is not only based on the knowledge of reactor geometry and operating conditions but also on the flow structures via their statistical parameters. Wavelet transform modulus maxima (WTMM) methodology has been used to study the evolution of structures and their interaction in a reduced dimensionality by evaluating the fractal spectra. Classification studies have been carried out using principal component analysis (PCA) of the fractal spectra. The results obtained show clear classes for the six types of equipments and delineate regimes to obtain benchmark patterns of flow hydrodynamics based on PCA co-ordinates. This methodology offers a generalized way for the optimal design and operation of different types of reactors. (c) 2008 Published by Elsevier Ltd .

10aChemical reactors10ahydrodynamics10aLength scale distribution10amixing10aModel reduction10aTurbulence10aWavelet transform1 aDeshpande, Sagar, S.1 aJoshi, Jyeshtharaj, B.1 aKumar, Ravi1 aKulkarni, B., D. uhttp://library.ncl.res.in/content/identification-and-characterization-flow-structures-chemical-process-equipment-using-001595nas a2200229 4500008004100000022001400041245005800055210005800113260006700171300001400238490000700252520084100259653003901100653001801139653001101157653001701168653001801185100002501203700002401228700002201252856009101274 2015 eng d a0008-403400aHeat transfer and mixing in flow through pinched pipe0 aHeat transfer and mixing in flow through pinched pipe a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcOCT a1860-18680 v933 a

There is an increasing trend of using tubular reactors either with passive or active augmentation methods for process intensification. A new passive method with pinching of pipe' is proposed and investigated for its performance. In the present work, initially, flow in a pinched pipe was studied experimentally and the same was reproduced numerically. The computational model was then used to investigate influences of key geometrical parameters of pinched pipe configuration on pressure drop, heat transfer, and mixing. The simulated results obtained with the pinched pipe were compared with a straight pipe, and with a commonly-used passive augmentation method (twisted tape inserts). The pinched pipe configuration offers better performance and more flexibility in manipulating heat transfer and mixing in intensified devices.

10acomputational fluid dynamics (CFD)10aheat transfer10amixing10apinched pipe10apressure drop1 aHasabnis, Nilesh, S.1 aTotlani, Kartik, A.1 aRanade, Vivek, V. uhttp://library.ncl.res.in/content/heat-transfer-and-mixing-flow-through-pinched-pipe-002392nas a2200241 4500008004100000022001400041245005900055210005700114260000800171300001200179490000700191520169000198653000801888653001801896653002401914653001801938653001101956100002301967700002401990700002602014700002202040856008802062 2019 eng d a0008-403400aFlow, mixing, and heat transfer in fluidic oscillators0 aFlow mixing and heat transfer in fluidic oscillators cFEB a542-5590 v973 a

There is an increasing emphasis on process intensification and development of compact, intensified reactors and separators in recent years. Significant efforts are being made to develop such intensified reactors and separators without any moving parts. Some of the recent research studies have proven that a liquid-liquid extractor based on the Coanda effect and feedback oscillations exhibit excellent mixing and liquid-liquid contacting. These fluidic oscillators can potentially be used for a variety of other multiphase reactions and systems demanding enhanced mixing and heat and mass transfer. In this work, we have computationally investigated flow, mixing, and heat transfer in fluidic oscillators based on the Coanda effect. Available information on flow and mixing in fluidic oscillators was critically reviewed and key gaps in the available knowledge with respect to the design and optimization of fluidic oscillators were identified. Computational flow models were developed to characterize key flow features like unsteady flows, secondary vortices, and internal recirculation over a range of Reynolds number (Re = 90-1538) for three different oscillator designs. Systematic numerical studies were carried out to quantify different flow regimes, oscillations, and the influence of key geometric parameters on flow, mixing, and heat transfer. Simulated results were critically analyzed and are presented in the form of dimensionless numbers. The approach and results presented in this work will provide useful insights and a systematic basis for extending the applications of the Coanda-based feedback oscillatory devices for a wide range of engineering applications.

10aCFD10aCoanda effect10afluidic oscillators10aheat transfer10amixing1 aKhalde, Chirag, M.1 aPandit, Ajinkya, V.1 aSangwai, Jitendra, S.1 aRanade, Vivek, V. uhttp://library.ncl.res.in/content/flow-mixing-and-heat-transfer-fluidic-oscillators