02037nas a2200229   4500008004100000022001400041245014900055210006900204260000800273300001100281490000700292520120300299653001601502653002501518653001801543653001901561653003201580100002801612700001601640700002301656856012801679       2022                        eng d  a0001-154100aEvaluating suitability of confined impinging jet reactor for exothermic reactions: hydrodynamics, residence time distribution, and heat transfer0 aEvaluating suitability of confined impinging jet reactor for exo  cOCT  ae177920 v683 a<p>
	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 &lt;= Rej &lt;= 3000\$\$ 500\textbackslashle {\textbackslashmathit{\textbackslashoperatorname{Re}}}_j\text backslashle 3000 \$\$ and 5 &lt;= L/D &lt;= 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.</p>
10aconfinement10aexothermic reactions10aheat transfer10aimpinging jets10aresidence time distribution1 aKhan, Muzammilanwar, S.1 aMane, Mayur1 aKulkarni, Amol, A.  uhttps://library.ncl.res.in/content/evaluating-suitability-confined-impinging-jet-reactor-exothermic-reactions-hydrodynamics02363nas a2200157   4500008004100000022001400041245007600055210006900131260000800200300001600208490000700224520182500231100002802056700002302084856009802107       2023                        eng d  a0743-746300aDynamics of drop formation in the presence of interfacial mass transfer0 aDynamics of drop formation in the presence of interfacial mass t  cAUG  a12627-126390 v393 a<p>The dynamics of drop formation have been investigated in the presence of interfacial mass transfer through controlled flow visualization experiments. The mixtures of n-hexane (solvent) and acetone (solute) were used as a dispersed phase, having different initial compositions varying over a broad range. Drops were formed at the submerged position in the continuous phase (water) at the same operating flow conditions. The unsteady force balance model is developed to analyze the implications of the simultaneously occurring interfacial transfer of the solute on the formation dynamics in real time, and predictions are validated with experimental results. Based on initial compositions, the analysis of the transient drop shape shows a sharp transition in the drop formation regime. At lower initial solute concentrations, i.e., phi(0) &lt; 0.2, axisymmetric drop formation occurs and the interfacial solute transfer has negligible effects on the formation dynamics. Over an intermediate range of solute concentrations, i.e., 0.2 &lt; phi(0) &lt; 0.5, Marangoni instability is triggered along the evolving interface, and therefore, the interface deformations and contractions occur during the drop formation. At phi(0) = 0.5, the drop takes highly nonaxisymmetric shapes and remains away from equilibrium until its detachment from an orifice. For phi(0) &gt; 0.5, the spontaneous ejection of plumes of the solute results in the rapid generation of multiple droplets of smaller size. This work shows that higher solute concentration gradients not only lead to faster solute transport but also induce strong interfacial instability simultaneously. Thus, the coupled effects of transient change in composition and fluid properties govern the drop size and its formation time in such systems under non-equilibrium.</p>
1 aKhan, Muzammilanwar, S.1 aKulkarni, Amol, A.  uhttps://library.ncl.res.in/content/dynamics-drop-formation-presence-interfacial-mass-transfer02412nas 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<p>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 &lt;= Re-in &lt;= 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 &lt; 50) to dominant secondary flow vortices for De &gt; 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 &gt; 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.</p>
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-series02340nas a2200157   4500008004100000022001400041245013800055210006900193260000900262300001400271490000700285520171100292100002802003700002302031856012802054       2024                        eng d  a0888-588500aUnderstanding the effects of physical properties of composite drop on its formation dynamics in presence of interfacial mass transfer0 aUnderstanding the effects of physical properties of composite dr  cAPR   a8430-84490 v633 a<p>
	Dynamics of drop formation is studied in presence of interfacial mass transfer through controlled flow visualization experiments and lumped force balance based model. Experiments were conducted using eight different combinations of ternary systems, involving variations in initial composition and physical properties of drop phase over a broad range. A new image analysis method is reported to accurately measure the size of deformed, nonaxisymmetric drops. Based on flow visualization and analysis of drop shape, four modes of drop formation are identified, including (i) mass transfer free mode, (ii) interfacial instability mode (Marangoni effects), (iii) dripping, and (iv) jetting, with progressively increasing solute concentrations. Exceptions to these modes are observed for tetrahydrofuran-toluene and tetrahydrofuran-benzene mixtures, in which the drop remains in mass transfer free mode even in presence of higher solute concentrations. Model predictions of real time change in drop volume show excellent match with experimental results for all of the systems under study. The analysis of force balance implies that the interplay between (i) surface tension force and (ii) the combination of buoyancy and force due to kinetic energy controls the drop detachment time as well as the final drop volume. Therefore, for identical operating conditions, transition in drop formation time occurs from 4 s to 65 ms, depending on the density difference and interfacial tension between contacting phases. The present findings provide detailed insights into the formation dynamics of composite drops, which are commonly encountered in liquid-liquid extraction and various multiphase operations.</p>
1 aKhan, Muzammilanwar, S.1 aKulkarni, Amol, A.  uhttps://library.ncl.res.in/content/understanding-effects-physical-properties-composite-drop-its-formation-dynamics-presence02143nas a2200241   4500008004100000022001400041245010300055210006900158260000800227300001200235490000700247520126500254653003301519653003501552653003001587653002901617100002801646700002301674700002601697700002401723700002301747856013101770       2025                        eng d  a1083-616000aConfined impinging jet reactor for high-throughput continuous flow mononitration of salicylic acid0 aConfined impinging jet reactor for highthroughput continuous flo  cJAN  a479-4890 v293 a<p>
	Novel approach is reported for highly efficient continuous mononitration of salicylic acid using confined impinging jet reactor (CIJR) with a vent. Initially, controlled semibatch reactions are optimized to achieve complete conversion and formation of mononitro products with very high selectivity for 5-nitrosalicylic acid (5-NSA). Further, the combination of computational fluid dynamics simulations and experiments is employed to optimize CIJR design and operating flow conditions, suitable to yield only mononitro products with excellent control over mixing, heat transfer, and liberation of fumes during continuous flow reaction. Detailed analysis of internal flow patterns, rate of heat generation, and concentration distribution inside the CIJR facilitated the optimization of present exothermic reaction in a safe manner. In less than a minute, complete salicylic acid (SA) conversion with good yield and better selectivity for 5-NSA is achieved using the CIJR. Safety and clogging issues are addressed effectively, even at a relatively lower mole ratio (1:5) of SA:acetic acid (AcOH). The present approach is quite scalable using the numbering-up strategy, with advantages viz. nonfouling, high throughput, and the small footprint of CIJR.</p>
10acomputational fluid dynamics10aconfined impinging jet reactor10ahigh-throughput synthesis10asalicylic acid nitration1 aKhan, Muzammilanwar, S.1 aShaikh, Tabrez, R.1 aKulkarni, Sphurti, P.1 aPatil, Abhishek, A.1 aKulkarni, Amol, A.  uhttps://library.ncl.res.in/content/confined-impinging-jet-reactor-high-throughput-continuous-flow-mononitration-salicylic-acid