Showing papers by "Jyeshtharaj B. Joshi published in 2003"
TL;DR: In this paper, an extensive review on the mathematical models proposed for the liquid-phase mixing has been presented, and the utility of the computational fluid dynamics modeling for the mixing optimization has been illustrated.
Abstract: The published literature on the liquid-phase mixing in a turbulent flow regime has been critically reviewed and analyzed. Experimental techniques for mixing time have been described together with their relative merits. The effects of the impeller design (blade number, blade angle, blade and disk dimensions, and blade shape), the location of the impeller (off-bottom clearance, distance from the vessel center, i.e., eccentricity), and the vessel size on the liquid-phase mixing have been critically analyzed. The mixing performance dependency on the internals such as baffles (number, dimension, and position) and the draft tube has been presented in detail. Further, an extensive review on the mathematical models proposed for the liquid-phase mixing has been presented, and the utility of the computational fluid dynamics modeling for the mixing optimization has been illustrated. Finally, suggestions have been made for the selection of an energy-efficient impeller−vessel configuration, and directions have been gi...
115 citations
TL;DR: This paper intends to provide the perspective of the current status of computational flow modeling with brief comments on the design of process equipment and the role of CFD models in it.
Abstract: This paper intends to provide the perspective of the current status of computational flow modeling. It begins the discussion with brief comments on the design of process equipment and the role of CFD models in it.
110 citations
TL;DR: In this paper, a low Reynolds number k-e model was used to simulate axial dispersion phenomena in both the transition and turbulent regions of pipe flow and an extensive comparison of the predicted axially dispersion coefficient with the experimental data was presented along with the predictions of various models published in the literature.
47 citations
TL;DR: In this paper, a unified model for NO X gas absorption in water and alkalies was proposed, which can be used for predicting point rates of NO X absorption as well as selectivity, for various gas compositions and liquid phase pH.
Abstract: The absorption of NO X gases in water and alkalies /NaOH, NH 4 OH, Ca(OH) 2 )] provides commercially important products nitric acid and salts (nitrates and nitrites), respectively. This complex phenomena of mass transfer with chemical reactions is described quantitatively in terms of /H(kD)] J values for J = N 2 O 3 , N 2 O 4 . However, the reported value of H(kD) for N 2 O 3 absorption in strong alkaline solution was 50 times its value in water. For the intermediate case of NO X absorption in weak alkali Ca(OH) 2 , it was necessary to have a mathematical model which incorporated the HNO 2 decomposition, as well as neutralization by alkali. This led to a unified model for NO X absorption, which can be used for predicting point rates of NO X absorption as well as selectivity, for various gas compositions and liquid-phase pH. Parametric sensitivity has been reported. A comparison of the model predictions with data from patent on Ca(NO 2 ) 2 manufacture has been made to test the model validity.
41 citations
TL;DR: In this paper, a CFD model was developed for the prediction of flow pattern in terms of mean velocity and eddy diffusivity profiles, which agree favourably with all the experimental data published in the literature.
Abstract: Liquid phase mixing time was measured in 0.2 and 0.4 m i.d. columns over a wide range of superficial gas velocity (0.07–0.295 ms–1) and height-to-diameter ratio (1–10). A CFD model was developed for the prediction of flow pattern in terms of mean velocity and eddy diffusivity profiles. The predictions agree favourably with all the experimental data published in the literature. Complete energy balance was established in all cases. The validated CFD model was extended for the simulation of the macro-mixing process by incorporating the effects of both the bulk motion and the eddy diffusion. Excellent agreement was observed between the CFD predicted and experimental values of the mixing time over the entire range of D, VG and HD/D covered. The model was further extended for the prediction of residence time distribution and hence the axial dispersion coefficient (DL). The predicted values of DL were found to agree very well with all the experimental data published in the literature.
36 citations
TL;DR: In this paper, the authors compared the blending performance of three different equipments: stirred tanks, jet mixers and ultrasound mixers, and found that turbochargers offer lower mixing time as compared with impeller mixers.
28 citations
TL;DR: In this paper, the effect of gas velocities on radial gas hold-up profiles for air-aqueous solutions of n-butanol was investigated in 0.385 m i.d. bubble column using gamma ray tomography.
27 citations
TL;DR: In this paper, the deactivation of Hen egg white lysozyme and lipase from Aspergillus oryzae at the gas-liquid interface was comprehensively investigated in three different contactors, viz., bubble column, stirred vessel and falling film.
19 citations
TL;DR: In this article, an attempt has been made to eliminate the unstable behavior of self-inducing reactors using a multiple-impeller system, and experiments were performed in a 1m-i.d. tank, with impeller parameters varied over a wide range.
Abstract: An attempt has been made to eliminate the unstable behavior of self-inducing reactors. For this purpose, a multiple-impeller system was developed. Experiments were performed in 1-m-i.d. tank, with impeller parameters varied over a wide range. Recommendations are made for optimum reactor design.
12 citations