01957nas a2200169 4500008004100000022001400041245012900055210006900184260007100253300001400324490000700338520124300345100002301588700002301611700002201634856013101656 2007 eng d a0888-588500aHydrodynamics of bubble column reactors at high gas velocity: experiments and computational fluid dynamics (CFD) Simulations0 aHydrodynamics of bubble column reactors at high gas velocity exp a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC a8431-84470 v463 a

This paper focuses on the modeling of flow and mixing in a bubble column reactor operated at high gas velocities (up to 0.40 m/s). A dual-tip conductivity probe was used to measure local void properties such as local time-averaged gas holdup, chord length distribution, bubble velocity distribution, and interfacial area. Chord length distribution was converted to bubble size distribution, using the backward transformation method. Liquid-phase mixing time measurements were conducted using a conductivity probe. A computational fluid dynamics (CFD) model was developed to simulate the unsteady gas-liquid flow in a bubble column using commercial code FLUENT 6.2. The time-averaged flow properties predicted by CFD simulations were compared with the experimental data. The role of unsteady flow structures in mixing was studied. The `' multiple snapshots `' approach was used to simulate the mixing time using CFD. The mixing times that were predicted for all superficial gas velocities compared favorably to the measured values. This study of the hydrodynamic behavior of a bubble column at higher gas velocity provides a basis for understanding and simulating solid suspension (or solid mixing) in slurry bubble column reactors.

1 aRampure, Mohan, R.1 aKulkarni, Amol, A.1 aRanade, Vivek, V. uhttp://library.ncl.res.in/content/hydrodynamics-bubble-column-reactors-high-gas-velocity-experiments-and-computational-fluid-002206nas a2200205 4500008004100000022001400041245011300055210006900168260006800237300001400305490000700319520140200326653000801728653003101736653002801767100003001795700002301825700002201848856013001870 2010 eng d a0001-154100aHysteresis in cloud heights during solid suspension in stirred tank reactor: experiments and CFD simulations0 aHysteresis in cloud heights during solid suspension in stirred t a111 RIVER ST, HOBOKEN, NJ 07030 USAbJOHN WILEY & SONS INCcNOV a2795-28040 v563 a

Solid suspension in stirred tank reactor is widely used in process industries for catalytic reactions, dissolution of solids, crystallization, and so on. Suspension quality is a key issue in design and operation of stirred reactor and its determination is not straight forward. Cloud height measurements of solid suspension provide a relatively simple way to quantify quality of suspension. In this work, experiments were carried out to quantify variation of cloud heights with impeller speed and particle characteristics. These measurements were carried out using visual observations, image analysis, and ultrasound velocity profiler techniques. The obtained data demonstrated the existence of hysteresis in cloud heights with respect to impeller speed. Apart from possible applications in reducing power required for achieving desired solid suspension quality, the existence of hysteresis also provides a new way to evaluate computational fluid dynamics (CFD) simulations of solid liquid flows in stirred vessels. An attempt was made to capture observed hysteresis in cloud heights in CFD simulations. The simulated results were compared with the experimental data. The presented models and results (experimental and computational) will he useful for simulating complex solid liquid flows in stirred reactors. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 2795-2804, 2010

10aCFD10ahysteresis in cloud height10asolid velocity profiles1 aSardeshpande, Madhavi, V.1 aJuvekar, Vinay, A.1 aRanade, Vivek, V. uhttp://library.ncl.res.in/content/hysteresis-cloud-heights-during-solid-suspension-stirred-tank-reactor-experiments-and-cfd-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-002646nas a2200265 4500008004100000022001400041245012000055210006900175260000900244300001200253490000800265520177000273653001502043653001702058653001302075653001402088653002502102100001602127700002402143700002102167700002202188700002202210700002502232856012302257 2019 eng d a0301-479700aHydrodynamic cavitation using vortex diode: an efficient approach for elimination of pathogenic bacteria from water0 aHydrodynamic cavitation using vortex diode an efficient approach cJUL  a210-2190 v2423 a

The present study successfully demonstrates greener methodology of hydrodynamic cavitation using rotational flows for disinfection of water. Disinfection of two model microbial strains-gram-negative (Escherichia colt) and gram-positive (Staphylococcus aureus) using vortex diode was evaluated. The removal efficacy was quantified for two different cavitation reactors. Practically complete elimination of E. coli was achieved (99%) after 1 h of cavitation at a pressure drop of only 0.5 bar. However, elimination of S. aureus using vortex diode was observed to be lower in comparison to the removal of E. coli and only 60% disinfection could be achieved under similar conditions, which can be subsequently enhanced up to 98% by increasing pressure drop. The results were compared with another cavitating device that employs linear flow for cavitation, orifice. The reactor geometry has significant impact on the disinfection process and orifice was found to require significantly higher pressure drop (10 bar) conditions for disinfection and for eliminating grain-positive bacteria with high efficiency. A plausible mechanism for disinfection was proposed to elucidate the role of cavitation in cell destruction leading to death of cells through the rupture of cell wall, oxidative damage and possible DNA denaturation. Also, a cavitation model using per pass disinfection was developed that can provide meaningful physical description of the disinfection process as against the conventional first order reaction rate model. This study would provide meaningful insight into cavitation process based on hydrodynamic cavitation for the destruction of both gram-negative and gram-positive bacteria from various water sources, including industrial wastewaters.

10aCavitation10aDisinfection10akinetics10apollution10aWastewater treatment1 aJain, Pooja1 aBhandari, Vinay, M.1 aBalapure, Kshama1 aJena, Jyotsnarani1 aRanade, Vivek, V.1 aKilledar, Deepak, J. uhttp://library.ncl.res.in/content/hydrodynamic-cavitation-using-vortex-diode-efficient-approach-elimination-pathogenic02376nas a2200229 4500008004100000022001400041245013800055210006900193260000800262300000600270490000800276520154700284653002801831653003501859653002401894653001801918653002401936100002301960700002101983700002202004856012002026 2022 eng d a0974-362600aHydrogen solubility in biphasic liquid reaction mixture of cinnamaldehyde hydrogenation: experimental and mathematical modeling study0 aHydrogen solubility in biphasic liquid reaction mixture of cinna cMAR a10 v1343 aThe solubility of hydrogen in the biphasic reaction mixture of cinnamaldehyde hydrogenation at 298 to 353 K has been determined in this work experimentally and by using a thermodynamic model. It is evident from many studies that the addition of extra phase, aqueous KOH as the fourth phase, to the three-phase cinnamaldehyde hydrogenation mixture [gas (hydrogen)-liquid (cinnamaldehyde + toluene)-solid (catalyst)] leads to enhancement of cinnamyl alcohol selectivity to a great extent. Determination of hydrogen solubility in this biphasic (organic-aqueous) reaction mixture is crucial to understand the intrinsic reaction kinetics of this reaction. The solubility of hydrogen was experimentally determined using a pressure drop method and reported in terms of Henry's constant. Firstly, hydrogen solubility was determined in pure components viz. toluene, cinnamaldehyde, and water followed by determination of its solubility in the cinnamaldehyde-toluene mixture, aqueous KOH, and eventually, in the reaction mixture containing the two immiscible liquid phases. The effect of changing concentrations in these mixtures and changing phase holdups in the total reaction mixture on hydrogen solubility was studied. Starting from pure components to the reaction mixture, the hydrogen solubility was predicted using a two-step thermodynamic approach involving regular solution theory and the theory of corresponding states. The solubility predictions from this thermodynamic model will be helpful in the accurate estimation of kinetic parameters.10abiphasic liquid mixture10agas-liquid-liquid-solid [GLLS]10ahydrogen solubility10aHydrogenation10athermodynamic model1 aKhan, Muzammil, Y.1 aJoshi, Sunil, S.1 aRanade, Vivek, V. uhttp://library.ncl.res.in/content/hydrogen-solubility-biphasic-liquid-reaction-mixture-cinnamaldehyde-hydrogenation