The Experts below are selected from a list of 96 Experts worldwide ranked by ideXlab platform
Aniruddha B Pandit - One of the best experts on this subject based on the ideXlab platform.
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studies in multiple impeller agitated gas liquid contactors
Chemical Engineering Science, 2006Co-Authors: Satish D Shewale, Aniruddha B PanditAbstract:Experiments have been performed to study the effect of the density and the volume of the tracer pulse on the mixing time for two impeller combinations in the presence of gas in a 0.3 m diameter and 1 m tall cylindrical acrylic vessel. The tall multi-impeller aerobic fermenters, which require periodic dosing of nutrients that are in the form of aqueous solution, is a classic case under consideration. Conductivity measuring method was used to measure the mixing time. Two triple impeller combinations; one containing two pitched blade downflow Turbines as upper impellers and Disc Turbine as the lowermost impeller (2 PBTD-DT) and another containing all pitched blade downflow Turbines (3 PBTD) have been used. Other variables covered during experiments were the density and the amount of the tracer pulse, the impeller rotational speed and the gas superficial velocity. Fractional gas hold-up, Power consumption and mass transfer coefficient have also been measured for both the impeller combinations. Influence of aeration and impeller speed on the mixing time has been explained by the interaction of air induced and impeller generated liquid flows. Three different flow regimes have been distinguished to explain the hydrodynamics of the overall vessel (i.e., multiple impeller system). A compartment model with the number of compartments varying with the flow regimes have been used to model liquid phase mixing in these flow regimes. A correlation for the prediction of the dimensionless mixing time in the loading regime has been proposed in order to account the effect of the density and the amount of the tracer pulse on the mixing time. Correlations have also been proposed to predict fractional gas hold-up and k L a.
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optimizing the impeller combination for maximum hold up with minimum power consumption
Biochemical Engineering Journal, 1998Co-Authors: S J Arjunwadkar, Aniruddha B Pandit, K. Saravanan, P R KulkarniAbstract:Abstract To select the optimum operating conditions for a multiple impeller laboratory bio-reactor, nine impeller combinations consisting of three basic impeller types, namely pitched blade Turbine downflow (PTD), pitched blade Turbine upflow (PTU) and Disc Turbine (DT), were tested. Power consumption and fractional gas hold-up measurements were taken over a range of 1–4 kw m −3 of power and 0.5–2 VVM of gas flow rates, for all the nine combinations consisting of any two impellers. A radial flow impeller (DT) near the sparger, i.e. lower impeller, was found to be a necessity for enhanced gas hold-up. With the DT as a lower impeller, use of PTD as an upper impeller was found to give higher gas hold-up compared with any other combination consisting of both radial flow (DT-DT) or both mixed flow (PTD-PTU, PTD-PTD, PTU-PTD and PTU-PTU) impellers, for equivalent power dissipation.
Doraiswami Ramkrishna - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation and comparison of industrial crystallizers
Canadian Journal of Chemical Engineering, 2014Co-Authors: Chinmay V Rane, Arijit A Ganguli, Ekambara Kalekudithi, R. N. Patil, J B Joshi, Doraiswami RamkrishnaAbstract:Simulation of flow patterns in eleven industrial crystallizers (standard Messo, Cerny direct contact, Swenson draft tube baffled, Swenson walker, Swenson evaporative, Oslo cooling, Oslo Krystal, APV Kestner, Batch Vacuum, stirred tank with Disc Turbine, and stirred tank with pitched blade impeller) have been carried out using computational fluid dynamics (CFD). Population balance modelling (PBM) is coupled with CFD to obtain better results. In all the cases, the crystallizer volume was 100 liter and the power consumption per unit volume was 1 kW/m3. The simulation results have been presented in terms of mean velocity components, turbulent kinetic energy and dissipation rate. On the basis of the flow patterns, these eleven crystallizers have been compared for crystal size distribution (CSD). It was found that Swenson Evaporative, Krystal and Batch Vacuum provide relatively low CSD.
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Effect of impeller design and power consumption on crystal size distribution
AIChE Journal, 2014Co-Authors: Chinmay V Rane, Jyeshtharaj B. Joshi, K. Ekambara, Doraiswami RamkrishnaAbstract:Crystallization processes in a 500 mL stirred tank crystallizer with computational fluid dynamics (CFD) and population balances toward estimating how crystal size distributions (CSDs) are influenced by flow inhomogeneities was explored. The flow pattern and CSD are presented here though extensive phase Doppler particle analyzer measurements and CFD predictions for three different impeller designs (Disc Turbine, pitched blade Turbine, and Propeller) and each rotated at three different speeds (2.5, 5, and10 r/s). As crystallization processes in practice could involve break-up and aggregation of crystals, some selected break-up and aggregation kernels are incorporated. Extensive comparison of simulations with experimental data showed consistent trends in the proper quantitative range. An attempt has also been made to develop scaling laws: (a) mean particle size with average power consumption per unit mass and (b) particle-size distribution with the turbulent energy dissipation distribution. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3596–3613, 2014
Abhijit Guha - One of the best experts on this subject based on the ideXlab platform.
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inflow rotor interaction in tesla Disc Turbines effects of Discrete inflows finite Disc thickness and radial clearance on the fluid dynamics and performance of the Turbine
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2018Co-Authors: Sayantan Sengupta, Abhijit GuhaAbstract:The article establishes the physics of the complex interaction of Discrete multiple inflows with the stationary shroud and the rotating channel of a Tesla Disc Turbine. Using a large number (150) o...
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the fluid dynamics of the rotating flow in a tesla Disc Turbine
European Journal of Mechanics B-fluids, 2013Co-Authors: Abhijit Guha, Sayantan SenguptaAbstract:Abstract The flow induced by rotating Discs has attracted some of the greatest minds in fluid dynamics like von Karman and Batchelor, and still is a vigorously active research area. In comparison, the available analysis of the rotating flow in the narrow gaps among closely-spaced co-axial multiple Discs of a Tesla Turbine, which produces power, is limited. In this paper a simple theory has been presented that describes the three-dimensional fields of velocity and pressure in the Tesla Disc Turbine. The theory gives the torque and power output which have been verified by comparing the theoretical predictions with recently published experimental results. The governing conservation equations have been cast in a form that makes it possible to formulate analytical solutions and to develop clear physical interpretation for each term in the equations. Thus the roles of each of the centrifugal, Coriolis, inertial and viscous forces in generating torque and power, and in establishing the pressure field have been comprehensively investigated and explained here. This physical exposition of the rotating flow in a Tesla Disc Turbine has been achieved for the first time in the present paper. Several subtle flow physics and fluid dynamic behaviors have been elucidated. As an example, it is shown here that a Tesla Disc Turbine may generate net torque and power even when the tangential fluid speed at the Disc periphery is less than the local tangential speed of the Disc. The subtle role of the Coriolis acceleration in establishing such flow conditions, which involve flow reversal and complex pathlines, has been explained.
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experiment and analysis for an improved design of the inlet and nozzle in tesla Disc Turbines
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2010Co-Authors: Abhijit Guha, B SmileyAbstract:AbstractIn this article, the performance of the inlet to a Tesla Disc Turbine has been studied. The losses in the inlet and nozzle are known to be a major reason why the overall efficiency of Disc Turbines is not high. A new nozzle utilizing a plenum chamber inlet has been designed and tested here. Experiments have demonstrated less than 1 per cent loss in total pressure in the new design compared to losses in the range 13–34 per cent for the original nozzle and inlet. Other than the dramatic improvement in loss reduction, the new plenum-integrated nozzle achieves a considerable enhancement in the uniformity of the jet. This has been demonstrated here both by experimental traverses of Pitot tubes as well as computational fluid dynamics studies. The greater uniformity of the jet means that a single Pitot measurement approximately positioned at the centre of the jet would record a value close to the true centre-line total pressure, and that calculations based on centre-line values of total pressure would gi...
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the design of a test rig and study of the performance and efficiency of a tesla Disc Turbine
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy, 2009Co-Authors: G P Hoya, Abhijit GuhaAbstract:AbstractA Tesla Disc Turbine and a flexible test rig have been designed and manufactured, and experimental results are presented. An analysis of the performance and efficiency of the Disc Turbine is carried out. The design philosophy of the flexible test rig has been explained. Various complementary methods of measurement have been implemented and compared, and several operational experiences have been noted. A new simple method, the angular acceleration method, for measuring output torque and power in a Tesla Turbine has been developed. This proved to be a successful method for overcoming the difficulties associated with the determination of very low torque at very high angular speed.
P R Kulkarni - One of the best experts on this subject based on the ideXlab platform.
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optimizing the impeller combination for maximum hold up with minimum power consumption
Biochemical Engineering Journal, 1998Co-Authors: S J Arjunwadkar, Aniruddha B Pandit, K. Saravanan, P R KulkarniAbstract:Abstract To select the optimum operating conditions for a multiple impeller laboratory bio-reactor, nine impeller combinations consisting of three basic impeller types, namely pitched blade Turbine downflow (PTD), pitched blade Turbine upflow (PTU) and Disc Turbine (DT), were tested. Power consumption and fractional gas hold-up measurements were taken over a range of 1–4 kw m −3 of power and 0.5–2 VVM of gas flow rates, for all the nine combinations consisting of any two impellers. A radial flow impeller (DT) near the sparger, i.e. lower impeller, was found to be a necessity for enhanced gas hold-up. With the DT as a lower impeller, use of PTD as an upper impeller was found to give higher gas hold-up compared with any other combination consisting of both radial flow (DT-DT) or both mixed flow (PTD-PTU, PTD-PTD, PTU-PTD and PTU-PTU) impellers, for equivalent power dissipation.
J B Joshi - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation and comparison of industrial crystallizers
Canadian Journal of Chemical Engineering, 2014Co-Authors: Chinmay V Rane, Arijit A Ganguli, Ekambara Kalekudithi, R. N. Patil, J B Joshi, Doraiswami RamkrishnaAbstract:Simulation of flow patterns in eleven industrial crystallizers (standard Messo, Cerny direct contact, Swenson draft tube baffled, Swenson walker, Swenson evaporative, Oslo cooling, Oslo Krystal, APV Kestner, Batch Vacuum, stirred tank with Disc Turbine, and stirred tank with pitched blade impeller) have been carried out using computational fluid dynamics (CFD). Population balance modelling (PBM) is coupled with CFD to obtain better results. In all the cases, the crystallizer volume was 100 liter and the power consumption per unit volume was 1 kW/m3. The simulation results have been presented in terms of mean velocity components, turbulent kinetic energy and dissipation rate. On the basis of the flow patterns, these eleven crystallizers have been compared for crystal size distribution (CSD). It was found that Swenson Evaporative, Krystal and Batch Vacuum provide relatively low CSD.
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cfd simulation of stirred tanks comparison of turbulence models part i radial flow impellers
Canadian Journal of Chemical Engineering, 2011Co-Authors: J B Joshi, Chinmay V Rane, Nandkishor K Nere, B N Murthy, Channamallikarjun S Mathpati, Ashwin W Patwardhan, Vivek V RanadeAbstract:A critical review of the published literature regarding the computational fluid dynamics (CFD) modelling of single-phase turbulent flow in stirred tank reactors is presented. In this part of review, CFD simulations of radial flow impellers (mainly Disc Turbine (DT)) in a fully baffled vessel operating in a turbulent regime have been presented. Simulated results obtained with different impeller modelling approaches (impeller boundary condition, multiple reference frame, computational snap shot and the sliding mesh approaches) and different turbulence models (standard k − e model, RNG k − e model, the Reynolds stress model (RSM) and large eddy simulation) have been compared with the in-house laser Doppler anemometry (LDA) experimental data. In addition, recently proposed modifications to the standard k − e models were also evaluated. The model predictions (of all the mean velocities, turbulent kinetic energy and its dissipation rate) have been compared with the experimental measurements at various locations in the tank. A Discussion is presented to highlight strengths and weaknesses of currently used CFD models. A preliminary analysis of sensitivity of modelling assumptions in the k − e models and RSM has been carried out using LES database. The quantitative comparison of exact and modelled turbulence production, transport and dissipation terms has highlighted the reasons behind the partial success of various modifications of standard k − e model as well as RSM. The volume integral of predicted energy dissipation rate is compared with the energy input rate. Based on these results, suggestions have been made for the future work in this area.
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assessment of standard k e rsm and les turbulence models in a baffled stirred vessel agitated by various impeller designs
Chemical Engineering Science, 2008Co-Authors: B N Murthy, J B JoshiAbstract:Abstract In the present work, laser-doppler anemometry measurements as well as CFD simulations have been performed for the flow generated by various impellers, namely Disc Turbine (DT), a variety of pitched blade down flow Turbine impellers varying in blade angle (Standard PBTD60, 45 and 30) and hydrofoil (HF) impeller. The tank was fully baffled, and the flow regime was turbulent. The objective of the present work was to carry out a detailed investigation of the predictive capabilities of the various turbulence models, i.e. the standard k – e model, Reynolds-stress transport model (RSTM) and large eddy simulations (LES). In case of LES, effect of subgrid scales on the resolved scales has been modeled by dynamic one equation subgrid-scale model. The simulated values of the mean axial, radial and tangential velocities along with the turbulent kinetic energy have been compared with the measured LDA data. It has been identified that the present SGS LES model performs well for predicting all the flow variables. Whereas, RSM and standard k – e model underpredict the turbulent kinetic energy profiles significantly in the impeller region. RSM can capture well all the mean flow characteristics and the standard k – e model fails to simulate the mean flow associated with the strong swirl. Energy content of the precessional vortex has been quantified for all the five impeller designs. Intermediate frequencies inbetween the mean circulation and the precession instability have been identified having a non-dimensional frequency of 0.04 to 0.07 for all the impeller designs under consideration.