Showing papers by "Jyeshtharaj B. Joshi published in 2005"
Abstract: The formation of gas bubbles and their subsequent rise due to buoyancy are very important fundamental phenomena that contribute significantly to the hydrodynamics in gas−liquid reactors. The rise o...
657 citations
TL;DR: In this article, an attempt has been made to develop a complete correspondence between the operation of a real column and the simulation by using CFD simulations for the prediction of flow pattern in bubble column reactors using 1D, 2D and 3D k-e models.
131 citations
TL;DR: The oxidation of benzyl alcohol by dilute nitric acid has been selected for the study as a typical method for the manufacture of industrially important intermediate benzaldehyde as mentioned in this paper.
Abstract: The oxidation of benzyl alcohol by dilute nitric acid has been selected for the study as a typical method for the manufacture of industrially important intermediate benzaldehyde. All the reactions ...
55 citations
TL;DR: The extent of cellulase deactivation has been found to correlate well with the average turbulent normal stress within the stirred vessel.
48 citations
TL;DR: In this paper, power consumption, mixing time, and flow pattern have been carried out in a stirred vessel of 0.5 m diameter for a standard 45° pitched-blade turbine and for a hydrofoil impeller with a variety of baffle and draft tube configurations.
Abstract: The flow pattern, power consumption, and mixing time in a stirred vessel depend not only on the impeller design but also on the tank geometry and internals. Measurements of power consumption, mixing time, and flow pattern have been carried out in a stirred vessel of 0.5 m diameter for a standard 45° pitched-blade turbine and for a hydrofoil impeller with a variety of baffle and draft tube configurations. The comparison of the flow pattern (average velocity, turbulent kinetic energy, maximum energy dissipation rate, average shear rate, and turbulent normal stress) has been presented on the basis of equal power consumption to illustrate the extent of interaction between the rotating impeller and the internals. Comparisons of laser Doppler anemometer (LDA) measurements and computational fluid dynamics (CFD) predictions have been presented.
40 citations
TL;DR: In this article, a criterion for the transition from the homogeneous to the heterogeneous regime in a bubble column is developed based on the theory of linear stability, and a good agreement has been obtained between the experimental transition gas hold-up and the predictions of the same obtained by the theory developed in this work.
37 citations
TL;DR: In this paper, the axial dispersion coefficient of liquid phase axial mixing was measured in a 100 mm id bubble column operated in the pressure range of 1-05 MPa.
22 citations
TL;DR: In this article, a low Reynolds number k-e computational fluid dynamics (CFD) model has been used for the description of flow pattern near the wall and an excellent agreement has been shown between the predicted and experimental hold-up and velocity profiles.
21 citations
TL;DR: The extent of lipase deactivation in both the columns was found to increase with an increase in hydrodynamic and interfacial flow parameters, however, at equal value of any of these parameters, the extent of deactivation was different in the two columns.
12 citations
TL;DR: In this paper, the authors proposed a method based on the synergistic combination of energy spectrum and the intermittency models for revealing different stages in the turbulent cascades for the estimation of eddy diffusivity and hence such a combination has resulted in a robust validation tool.
11 citations
TL;DR: In this paper, the kinetics of aerobic biological oxidation of a PTA (terephthalic acid) plant waste was investigated for plant effluent (initial COD: 7000-8000 ppm) and anaerobically treated PTA effluent, and experiments were performed at three different Dissolved oxygen (DO) levels viz. low (0.05-0.1 ppm), intermediate (1.00-3.00 ppm), and high (>6.
TL;DR: In this article, a computational fluid dynamics (CFD) model was developed to describe both of the extreme regimes (viscous and turbulent), including the transition regime, and an extensive comparison of predicted mean axial liquid velocity profiles and fractional gas hold-up profiles with the experimental data has been presented.
Abstract: In the present work, a computational fluid dynamics (CFD) model was developed to describe both of the extreme regimes (viscous and turbulent), including the transition regime. The second objective was to examine the extent to which CFD models are able to describe quantitatively the variation of eG with VG as a function of flow regimes. This study helps to underline the distinguishing characteristics of both regimes: homogeneous and heterogeneous. An extensive comparison of predicted mean axial liquid velocity profiles and fractional gas hold-up profiles with the experimental data has been presented. The agreement has been shown to be excellent. The CFD model has also been compared with the simplified analytical solutions. In a fully developed heterogeneous regime and under turbulent conditions, the reversal point for the axial velocity was found to be in the range of 0.7−0.75R. With a decrease in the Reynolds number (DVCρL/μL), the reversal point was found to shift toward the center up to 0.5R. Further, ...
TL;DR: In this paper, the authors investigated the gas induction characteristics of a stator-rotor-type self-inducing impeller in the cases without and with gas line resistance, and the dominant role of local gas holdup was identified and the mechanism of gas induction was established.
Abstract: The gas induction characteristics of a stator-rotor-type self-inducing impeller were investigated in the cases without and with gas line resistance. To understand the hydrodynamics near the impeller, and to characterize the mechanism of gas induction, the local liquid velocity was measured with a laser Doppler anemometer. The effect of impeller speed, impeller submergence, and gas line resistance on the volumetric flow rate of liquid, as well as the rate of gas induction, was investigated. The dominant role of local gas holdup was identified and the mechanism of gas induction was established, with the help of an energy balance.
TL;DR: The relationship between the geometry and the operating conditions, hydrodynamics and performance of an industrial gas-liquid stirred reactor has been studied with the help of CFD modeling and gamma ray tomography as mentioned in this paper.