@article { ISI:000258442800009, title = {CFD simulation of gas-liquid flows in a reactor stirred by dual rushton turbines}, journal = {International Journal of Chemical Reactor Engineering}, volume = {6}, year = {2008}, month = {JAN}, pages = {Article No. A60}, publisher = {BERKELEY ELECTRONIC PRESS}, type = {Article}, address = {2809 TELEGRAPH AVENUE, STE 202, BERKELEY, CA 94705 USA}, abstract = {

In the present work, we have simulated gas-liquid flows in a tall stirred reactor equipped with dual Rushton turbines. A two fluid model along with the standard k-epsilon turbulence model and modified drag coefficient, (proposed by Khopkar \& Ranade, 2006) accounting for the effect of bulk turbulence, was used to simulate the dispersed gas-liquid flow in a stirred reactor. The multiple reference frames (MRF) approach was used to simulate impeller rotation in a fully baffled reactor. The computational model was mapped on to a commercial solver FLUENT 6.2 (of Fluent Inc. USA). The model was used to simulate three distinct flow regimes in a gas-liquid stirred reactor: L33-VC (lower impeller-upper impeller), S33-VC and VC-VC. The model predictions were compared with the published experimental data of Bombac \& Zun (2000). The predicted results show good agreement with the experimental data for all the three flow regimes. The computational model presented in this work would be useful for simulating different flow regimes in a gas-liquid stirred vessel.

}, keywords = {computational fluid dynamics, dual Rushton turbine, Flow regimes, gas hold-up distribution, stirred reactor}, issn = {1542-6580}, author = {Kasat, Gopal R. and Pandit, Aniruddha B. and Ranade, V. V.} } @article { ISI:000305766800017, title = {Computational fluid dynamics modelling of solid suspension in stirred tanks}, journal = {Current Science}, volume = {102}, number = {11}, year = {2012}, month = {JUN}, pages = {1539-1551}, publisher = {INDIAN ACAD SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

Solid suspension and mixing are crucial in many important processes, including multiphase catalytic reactions, crystallization, precipitation, etc. In recent years, various efforts have been made to numerically simulate solid-liquid flows in stirred vessels using computational fluid dynamics (CFD). In this article, we present a brief account of our group{\textquoteright}s efforts at developing and using CFD models for simulating solid suspension in stirred tanks. Computational models were developed and evaluated by comparing model predictions with our data as well as published experimental data. A variety of experimental techniques ranging from torque and wall pressure fluctuations to ultrasound velocity profiler were used. Efforts were made to develop appropriate sub-models for capturing influence of the prevailing turbulence and solid volume fraction on effective inter-phase coupling terms. A hysteresis in variation of the height of the cloud of suspended solid with impeller rotational speed was observed. The hysteresis, besides having applications in realizing better suspension at lower effective power consumption, also offers an attractive evaluation test for CFD models. A new way to carry out dynamic settling of solid cloud by sudden impeller stoppage has been developed. The approach, models and results presented here will be useful for extending applications of CFD models for simulating industrial stirred slurry reactors as well as further research in the field.

}, keywords = {computational fluid dynamics, hysteresis, solid suspension, stirred tanks}, issn = {0011-3891}, author = {Sardeshpande, Madhavi V. and Ranade, Vivek V.} } @article { ISI:000317469700034, title = {Flow and heat transfer in serpentine channels}, journal = {Aiche Journal}, volume = {59}, number = {5}, year = {2013}, month = {MAY}, pages = {1814-1827}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

Serpentine channels are often used in microchannel reactors and heat exchangers. These channels offer better mixing, higher heat and mass-transfer coefficients than straight channels. In the present work, flow and heat transfer experiments were carried out with a serpentine channel plate comprising of 10 units (single unit dimensions: 1 x 1.5 mm(2) in cross section, length 46.28 mm, D-h 1.2 mm) in series. Pressure drop and heat-transfer coefficients were experimentally measured. Flow and heat transfer in the experimental set-up were simulated using computational fluid dynamics (CFD) models to understand the mechanisms responsible for performance enhancement. The CFD methodology, thus, developed was applied to understand the effect of various geometrical parameters on heat transfer enhancement. A criterion was defined for evaluation of heat transfer performance (heat transfer per unit pumping power), thus, ensuring due considerations to required pumping power. The effect of geometrical parameters and the corresponding mechanisms contributing for enhancement are discussed briefly. Based on the results, a design map comprising different serpentine channels showing heat transfer enhancement with pumping power was developed for Reynolds number of 200 which will be useful for further work on flow and heat transfer in serpentine channels. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1814-1827, 2013

}, keywords = {computational fluid dynamics, heat transfer, pressure drop, serpentine}, issn = {0001-1541}, doi = {10.1002/aic.13954}, author = {Karale, Chaitanya M. and Bhagwat, Sunil S. and Ranade, Vivek V.} } @article {46707, title = {Efficient processing of reactions involving diazonium salts: meerwein arylation in an impinging-jet reactor}, journal = {Organic Process Research \& Development}, volume = {24}, year = {2020}, month = {SEP}, pages = {1658-1664}, type = {Article}, abstract = {

This work reports a novel approach for performing high-throughput synthesis of Meerwein arylation in an impingingjet reactor. The multistep reaction was performed in a single reactor via in situ diazonium salt generation followed by Meerwein arylation. The work involves many iterations between experiments and simulations (where we integrate simulating the flow, heat transfer, and reaction simultaneously) for optimization of conditions in an inverted impinging-jet reactor. The effect of design variables viz. catalyst concentration, inlet temperature, and monomer mole ratio on the yield of the desired product was studied in detail, and the simulation results were used to plan the continuous experiments. An infrared camera was used to monitor the transient reactor temperature for steady-state analysis. The lab-scale inverted impinging-jet reactor with over 93\% isolated yield can offer a space-time yield of 277.78 tons/m(3)/day. The numbering-up of an inverted impinging-jet reactor can be an effective way for cleaner production of products through typical Meerwein arylation.

}, keywords = {computational fluid dynamics, high throughput synthesis, impinging-jet reactor, IR camera, Meerwein arylation, Numbering-up}, issn = {1083-6160}, doi = {10.1021/acs.oprd.0c00271}, author = {Shukla, Chinmay A. and Atapalkar, Ranjit S. and Kulkarni, Amol A.} }