01958nas a2200169 4500008004100000022001400041245012900055210006900184260007100253300001400324490000700338520124300345100002301588700002301611700002201634856013201656 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. uhttps://library.ncl.res.in/content/hydrodynamics-bubble-column-reactors-high-gas-velocity-experiments-and-computational-fluid-001969nas a2200169 4500008004100000022001400041245007400055210006900129260007100198300001600269490000700285520132800292100003201620700002301652700002201675856010201697 2012 eng d a0888-588500aHydrodynamics of liquid-liquid dispersion in an advanced-flow reactor0 aHydrodynamics of liquidliquid dispersion in an advancedflow reac a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC a16251-162620 v513 a

Hydrodynamics and mass transfer of immiscible liquid-liquid flows are explored in an Advanced-Flow Reactor (AFR). These systems are emerging as one of the major commercial systems for small scale continuous flow chemistry, and characterization of the transport phenomena is critical for reaction implementation. With hexane/water as a model system, we use flow visualization techniques to determine drop size distribution, hexane holdup, and specific interfacial areas for a phase flow rate range of 10-80 mL/min. The complex geometry of the AFR with its continuously changing cross section along the flow path and strategically placed obstacles creates pressure changes that cause drop breakup and enhance mass transfer. Observations show that a wide range of average drop size (0.33-1.3 mm) can be achieved in the AFR depending upon the inlet flow rates and inlet composition. Pressure drop measurements are performed to estimate the power consumption and are used to compare the efficiency of AFR with conventional liquid-liquid contactors. The analysis shows that, similar to microreactors, the AFR can provide specific interfacial areas (1000-10 000 m(-1)) and overall mass transfer coefficients (1.9-41 s(-1)) a few orders of magnitude larger than conventional stirred tank reactors and also the static mixers.

1 aNieves-Remacha, Maria, Jose1 aKulkarni, Amol, A.1 aJensen, Klavs, F. uhttps://library.ncl.res.in/content/hydrodynamics-liquid-liquid-dispersion-advanced-flow-reactor-001873nas a2200169 4500008004100000022001400041245008200055210006900137260000800206300001000214490000700224520129800231100002401529700001501553700002301568856011201591 2019 eng d a0888-588500aHydrodynamics and selectivity engineering of a multipoint dosing flow reactor0 aHydrodynamics and selectivity engineering of a multipoint dosing cDEC a228740 v583 a

This paper reports the suitability of a multipoint injection continuous flow reactor for carrying out a sequential reaction, while taking into account the associated hydrodynamics of such systems. Pressure drop was measured for different fluid injection patterns, viz., equal fluid dosing, decreasing dosing, and increasing dosing flow rates from the first to the last inlet. Moreover, residence time distribution was also explored. The data were compared with a conventional single-point injection. The extent of dispersion was found to be higher in the decreasing dosing profile compared to equally distributed dosing. Taking into account of these features, the suitability of such a reactor system for competitive-consecutive homogeneous nitration reaction was evaluated. The analysis was done on the basis of the Damkohler number (Da) for mixing and reaction. The rate-controlling phenomena were used to simulate the performance of the reactor for a range of a number of inlets, the mole ratio of reactants, and relative values of Da. The observations indicate that the multipoint injection is not beneficial for mixing controlled reactions. However, for reactions in the transient regime (i.e., 0.001 < t(m)/t(R) < 1000), it gives higher selectivity of the desired product.

1 aShukla, Chinmay, A.1 aPal, Sayan1 aKulkarni, Amol, A. uhttps://library.ncl.res.in/content/hydrodynamics-and-selectivity-engineering-multipoint-dosing-flow-reactor02412nas a2200205 4500008004100000022001400041245009200055210006900147260000900216300001600225490000700241520169800248653001601946653003001962653002301992100002802015700002102043700002302064856011902087 2023 eng d a0888-588500aHydrodynamics, residence time distribution, and mass transfer in spiral coils in series0 aHydrodynamics residence time distribution and mass transfer in s cDEC  a21822-218340 v623 a

Here, we report the analysis of flow field, residence time distribution (RTD), and mass transfer for the novel design of a spiral coil reactor (SCR) consisting of five spiral coils connected in series. Each coil comprises 8 turns with minimum and maximum radii of curvatures of 15 and 45 mm, respectively. The SCR is made up of an SS 316 tube (1/8 in. approximate to 3.175 mm O.D. and 1.8 mm I.D.), with a total length of 3.89 m. Experiments, as well as three-dimensional (3D) CFD simulations, are carried out to study the effects of the flow rate (61 <= Re-in <= 1839) on spatial variations in velocity and pressure distribution within the individual coils of the reactor. The flow regime is observed to undergo a transition from stable laminar flow for a lesser Dean number (De < 50) to dominant secondary flow vortices for De > 80. During the flow from the inner to the outer turns of the coil, the tangential velocity increases with a decreasing curvature ratio (delta), and the opposite occurs during the flow from the outer to the inner turns of the coil. Experimental RTD results show that the extent of axial dispersion decays exponentially with increasing Re and remains constant for Re > 500. For liquid-liquid two-phase flow, the spiral coils in series offer a mass transfer coefficient comparable to those of static mixers and agitated contactors but with significantly lesser power consumption per unit volume. This work gives new insights into the design of a spiral coil reactor suitable to carry out single-phase and multiphase reactions efficiently as possibly the most space-filling option of tubular reactors with excellent transport characteristics.

10aGas- Liquid10aheat transfer coefficient10aLiquid Taylor Flow1 aKhan, Muzammilanwar, S.1 aDeore, Hital, S.1 aKulkarni, Amol, A. uhttps://library.ncl.res.in/content/hydrodynamics-residence-time-distribution-and-mass-transfer-spiral-coils-series