@article { ISI:000226743800002, title = {Computational study of a single-phase flow in packed beds of spheres}, journal = {AICHE Journal}, volume = {51}, number = {2}, year = {2005}, month = {FEB}, pages = {365-378}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

Packed-bed reactors are widely used in petrochemical, fine chemical, and pharmaceutical industries. Detailed knowledge of interstitial flow in the void space of such packed-bed reactors is essential for understanding the heat and mass transfer characteristics. In this paper, fluid flow through the array of spheres was studied using the unit-cell approach, in which different periodically repeating arrangements of particles such as simple cubical, 1-D rhombohedral, 3-D rhombohedral, and face-centered cubical geometries were considered. Single-phase flow through these geometries was simulated using computational fluid dynamics (CFD). The model was first validated by comparing predicted results with published experimental and computational results. The validated model was further used to study the effect of particle arrangement/orientation on velocity distribution and heat transfer characteristics. The simulated results were also used to understand and to quantify, relative contributions of surface drag and form drag in overall resistance to the flow through packed-bed reactors. The model and the results presented here would be useful in elucidating the role of microscopic flow structure on mixing and other transport processes occurring in packed-bed reactors. (C) 2005 American Institute of Chemical Engineers.

}, keywords = {CFD, drag, heat transfer, packed bed, packing arrangement}, issn = {0001-1541}, doi = {10.1002/aic.10314}, author = {Gunjal, P. R. and Ranade, V. V. and Chaudhari, Raghunath V.} } @article { ISI:000231486900018, title = {Modeling of vaporization and cracking of liquid oil injected in a gas-solid riser}, journal = {Chemical Engineering Science}, volume = {60}, number = {22, SI}, year = {2005}, note = {7th International Conference on Gas-Liquid and Gas-Liquid-Solid, Strasbourg, FRANCE, FEB, 2005}, month = {NOV}, pages = {6049-6066}, publisher = {Chem Engn Grp Nancy}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Vaporization and cracking of liquid oil injected in a gas-solid riser (fluid catalytic cracking riser reactor) was computationally studied in this work. Evaporation of a single drop injected in a stream of gas-solid mixture was analyzed first. A model for simulating evaporation of a drop considering heat transfer from the gas phase as well as from the solid particles was developed. The model relates the evaporation rate of droplet with rate of collisions of solid particles, specific heat capacities of solid and liquid, latent heat of vaporization, relative velocity of gas and liquid and temperatures of three phases. The understanding gained from such a model was then extended to simulate evaporation of liquid drops injected in FCC risers. The Eulerian-Lagrangian approach was used to simulate simultaneous evaporation and cracking reactions occurring in FCC riser reactors. A commercial CFD code, FLUENT (of Fluent Inc., USA) was used. Four and ten lump models were used for simulating cracking reactions. Appropriate user defined functions were developed to implement heterogeneous kinetics and heat transfer models in FLUENT. A special algorithm was developed to calculate accumulated coke on catalyst particles. A boiling point range was considered for simulating realistic oil feedstock. The model was first evaluated by comparing predicted results with published industrial data. The simulations were then carried out to understand influence of key design and operating parameters on performance of FCC riser reactors. The parameters studied included; initial oil droplet distribution, catalyst inlet temperature, catalyst to oil ratio and thermal cracking. The approach, model and results presented here would be useful for optimization of FCC operation, cost to benefit analysis of new FCC nozzles and related decision-making. (c) 2005 Elsevier Ltd. All rights reserved.

}, keywords = {cracking reactions, Evaporation, FCC, heat transfer, riser}, issn = {0009-2509}, doi = {10.1016/j.ces.2005.04.046}, author = {Nayak, S. V. and Joshi, S. L. and Ranade, V. V.} } @article { ISI:000260283800018, title = {Effect of hydrodynamic cavitation on zooplankton: a tool for disinfection}, journal = {Biochemical Engineering Journal}, volume = {42}, number = {3}, year = {2008}, month = {DEC}, pages = {320-328}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Application of hydrodynamic cavitation for disinfection of water is gaining momentum, as it provides environmentally and economically sound options. In this effort, the effect of cavitating conditions created by differential pump valve opening and that created by flowing through a cavitating element (orifice plates) on the microbes (zooplankton in sea water) is described. The experimental results are compared with modelling of cavitating conditions that includes cavity dynamics, turbulence generated by individual oscillating cavity, cell wall strength and geometrical and operating parameters of cavitation device. Theoretical model for quantifying the cavitationally generated turbulent shear and extent of microbial disinfection has been developed. Experimental results indicated that cavitation and/or turbulent fluid shear dominantly originating from cavitation are effective tools for sea water disinfection as more than 80\% of the zooplankton present in the sea water were killed. It was also observed that shock waves generated due to cavitation is not the sole cause for zooplankton disruption. A correct physical mechanism accounting fluid turbulence and shear, generated from stable oscillation of cavity, significantly contribute towards the disruption. Further refinement of the model presented will serve as a basis for higher degree of disinfection and provide a practical tool for sea water disinfection. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Cell disruption, heat transfer, Hydrodynamic cavitation, Modelling, Wastewater treatment, Zooplankton}, issn = {1369-703X}, doi = {10.1016/j.bej.2008.08.001}, author = {Sawant, Subhash Shivram and Anil, Arga Chandrashekar and Krishnamurthy, Venkat and Gaonkar, Chetan and Kolwalkar, Janhavi and Khandeparker, Lidita and Desai, Dattesh and Mahulkar, Amit Vinod and Ranade, Vivek Vinayak and Pandit, Aniruddha Balchandra} } @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 { ISI:000317151900024, title = {Synthesis of triangular gold nanoplates: role of bromide ion and temperature}, journal = {Colloids and Surfaces A-Physicochemical and Engineering Aspects}, volume = {422}, year = {2013}, month = {APR}, pages = {181-190}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Synthesis of noble metal triangular nanoplates is a kinetically controlled process in which temperature and packing defects play a major role. Nucleation and growth process of kinetically controlled reaction can be greatly influenced by temperature affecting the yield and edge length of the triangles. Through a conventional batch mode process, here we study the effect of temperature on nucleation and growth of gold triangular nanoplates and obtain some insight of the temperature effects on the final yield and edge length of triangles. The role of Br- ions in the synthesis of triangular nanoplates is studied by varying the amount of CAB and by replacing the CTAB with HBr. The results show that, while CTAB controls the edge length and yield of triangles, its use is not mandatory to attain plate like morphology. Finally we show that, while the initial temperature of the reaction mixture governs the nucleation rate and the rate of temperature rise governs the growth rate of particles, they along with the concentration of Br- ions control the edge length and yield. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Au nanotriangles, Halide ion effect, heat transfer, Kinetically controlled, Nature of gold precursor complex, Nucleation and growth, Optical properties}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2013.01.044}, author = {Kumar, D. V. Ravi and Kulkarni, Amol A. and Bhagavatula L. V. Prasad} } @article { ISI:000330613400003, title = {Two-phase flow boiling in small channels: a brief review}, journal = {Sadhana-Academy Proceedings in Engineering Sciences}, volume = {38}, number = {6}, year = {2013}, month = {DEC}, pages = {1083-1126}, publisher = {INDIAN ACAD SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

Boiling flows are encountered in a wide range of industrial applications such as boilers, core and steam generators in nuclear reactors, petroleum transportation, electronic cooling and various types of chemical reactors. Many of these applications involve boiling flows in conventional channels (channel size \>= 3 mm). The key design issues in two phase flow boiling are variation in flow regimes, occurrence of dry out condition, flow instabilities, and understanding of heat transfer coefficient and vapor quality. This paper briefly reviews published experimental and modeling work in these areas. An attempt is made to provide a perspective and to present available information on boiling in small channels in terms of channel size, flow regimes, heat transfer correlations, pressure drop, critical heat flux and film thickness. An attempt is also made to identify strengths and weaknesses of published approaches and computational models of boiling in small channels. The presented discussion and results will provide an update on the state-of-the-art and will be useful to identify and plan further research in this important area.

}, keywords = {Boiling, dry-out, heat transfer, instabilities, small channel, two-phase flow}, issn = {0256-2499}, author = {Sardeshpande, Madhavi V. and Ranade, Vivek V.} } @article { ISI:000362083400021, title = {Heat transfer and mixing in flow through pinched pipe}, journal = {Canadian Journal of Chemical Engineering}, volume = {93}, number = {10}, year = {2015}, month = {OCT}, pages = {1860-1868}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

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{\textquoteright} 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.

}, keywords = {computational fluid dynamics (CFD), heat transfer, mixing, pinched pipe, pressure drop}, issn = {0008-4034}, doi = {10.1002/cjce.22275}, author = {Hasabnis, Nilesh S. and Totlani, Kartik A. and Ranade, Vivek V.} } @article {45486, title = {Flow, mixing, and heat transfer in fluidic oscillators}, journal = {Canadian Journal of Chemical Engineering}, volume = {97}, year = {2019}, month = {FEB}, pages = {542-559}, type = {Article}, abstract = {

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.

}, keywords = {CFD, Coanda effect, fluidic oscillators, heat transfer, mixing}, issn = {0008-4034}, doi = {10.1002/cjce.23377}, author = {Khalde, Chirag M. and Pandit, Ajinkya V. and Sangwai, Jitendra S. and Ranade, Vivek V.} } @article {48062, title = {Evaluating suitability of confined impinging jet reactor for exothermic reactions: hydrodynamics, residence time distribution, and heat transfer}, journal = {AICHE Journal}, volume = {68}, year = {2022}, month = {OCT}, pages = {e17792}, type = {Article}, abstract = {

Effect of confinement (wall proximity) of a confined impinging jet reactor (CIJR) on the flow field, residence time distribution and heat transfer are explored, through experiments and CFD simulations. Hydrodynamic characteristics are evaluated for different parameters namely confinement, impinging jet velocity, temperature gradient, and so on. For 2 mm confinement, highest values of dispersion number and overall heat transfer coefficient are observed due to interaction of turbulent eddies followed by the effect of reactor wall proximity. For the CIJR having confinements above 10 mm, jet velocity need to be greater than 3 m/s to achieve both, excellent mixing efficiency and high heat removal rate. Empirical correlations for Dispersion and Nusselt numbers as a function of Re-j and L/D are obtained, over a range of 500 \<= Rej \<= 3000\$\$ 500\textbackslashle {\textbackslashmathit{\textbackslashoperatorname{Re}}}_j\text backslashle 3000 \$\$ and 5 \<= L/D \<= 35\$\$ 5\textbackslashle L/D\textbackslashle 35 \$\$, which correspond to jet velocity of 0.5-3 m/s. The present study gives a basis for designing CIJR suitable for rapid, homogeneous, exothermic reactions.

}, keywords = {confinement, exothermic reactions, heat transfer, impinging jets, residence time distribution}, issn = {0001-1541}, doi = {10.1002/aic.17792}, author = {Khan, Muzammilanwar S. and Mane, Mayur and Kulkarni, Amol A.} }