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P Sesha Talpa Sai
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P Sesha Talpa Sai
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P Sesha Talpa Sai
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Sai, P. S.T.
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47 results
Now showing 1 - 10 of 47
- PublicationNumerical investigation of membrane oxygenation using sub-channel analysis(30-10-2018)
;Subraveti, Sai Nikhil ;Vinod Kumar, V. ;Pothukuchi, Harish; Purpose: Better membrane oxygenators need to be developed to enable efficient gas exchange between venous blood and air. Design/methodology/approach: Optimal design and analysis of such devices are achieved through mathematical modeling tools such as computational fluid dynamics (CFD). In this study, a control volume-based one-dimensional (1D) sub-channel analysis code is developed to analyze the gas exchange between the hollow fiber bundle and the venous blood. DIANA computer code, which is popular with the thermal hydraulic analysis of sub-channels in nuclear reactors, was suitably modified to solve the conservation equations for the blood oxygenators. The gas exchange between the tube-side fluid and the shell-side venous blood is modeled by solving mass, momentum and species conservation equations. Findings: Simulations using sub-channel analysis are performed for the first time. As the DIANA-based approach is well known in rod bundle heat transfer, it is applied to membrane oxygenators. After detailed validations, the artificial membrane oxygenator is analyzed for different bundle sizes (L/W) and bundle porosity (epsilon) values, and oxygen saturation levels are predicted along the bundle. The present sub-channel analysis is found to be reasonably accurate and computationally efficient when compared to conventional CFD calculations. Research limitations/implications: This approach is promising and has far-reaching ramifications to connect and extend a well-known rod bundle heat transfer algorithm to a membrane oxygenator community. As a variety of devices need to be analyzed, simplified approaches will be attractive. Although the 1D nature of the simulations facilitates handling complexity, it cannot easily compete with expensive and detailed CFD calculations. Practical implications: This work has high practical value and impacts the design community directly. Detailed numerical simulations can be validated and benchmarked for future membrane oxygenator designs. Social implications: Future membrane oxygenators can be designed and analyzed easily and efficiently. Originality/value: The DIANA algorithm is popularly used in sub-channel analysis codes in rod bundle heat transfer. This efficient approach is being implemented into membrane oxygenator community for the first time. - PublicationAmmonium-Based Ionic Liquid as an Entrainer for the Separation of n-Propanol + Water and Isopropanol + Water Mixtures(08-03-2018)
;Janakey Devi, V. K.P.; Balakrishnan, A. R.The effect of the ionic liquid tetramethylammonium chloride [TMACl] on the vapor-liquid equilibrium of n-propanol + water and isopropanol + water was studied experimentally. The ionic liquid [TMACl] was identified as a suitable entrainer for breaking the azeotrope of these two alcohol-water mixtures. This work reports the influence of an ammonium-based ionic liquid on the separation of azeotropic mixtures. The isobaric vapor liquid equilibrium data of n-propanol + water + [TMACl] and isopropanol + water + [TMACl] were measured at atmospheric pressure. The amount of [TMACl] required for eliminating the azeotrope for both the systems was found to be low compared to imidazolium ionic liquids reported earlier. For n-propanol + water system, the azeotrope was eliminated at [TMACl] mole fraction of 0.05, and for isopropanol + water system, the azeotrope was eliminated at a mole fraction of 0.026. The effect of [TMACl] on both the alcohol-water systems was explained in terms of relative volatility and activity coefficient. - PublicationEnrichment of titanium dioxide in red mud: a kinetic study(01-01-1999)
;Kasliwal, PankajA process is described for the enrichment of titanium dioxide in red mud. The procedure employed is leaching the red mud with hydrochloric acid followed by roasting the leached residue with sodium carbonate. The kinetics of leaching of various constituents of red mud were obtained experimentally in a stirred batch reactor. The variables include acid to mud ratio and temperature. The data obtained were analysed using the shrinking core model and Jander's equation. The effect of roasting time and temperature on percentage dissolution of alumina in leached residue was studied using a full factorial search and optimized conditions were obtained. - PublicationNumerical simulation of the hydrodynamics of a liquid solid circulating fluidized bed(01-01-2014)
;Roy, S.; We present a modeling framework for the simulation of the hydrodynamic features of a liquid solid circulating fluidized bed (LSCFB) using computational fluid dynamics (CFD). Using an Eulerian-Eulerian approach to deal with the two-phase flow aspects and the kinetic theory of granular flow (KTGF) approach to deal with the solid-fluid interaction, we simulate the complete flow loop of an LSCFB using three-dimensional, time-dependent CFD calculations. We show that the essential features of the two-phase flow in the riser, the downcomer, the liquid-solid separator at the top and in the solids return feed pipe at the bottom are captured well in these simulations. The role of the flow distributors in establishing circulation is critically analyzed with the aid of post-processing tools. Comparison with literature data shows qualitative agreement with known trends of important hydrodynamic parameters and highlights the need for calibration of the constitutive equations for LSCFB applications. © 2013 Elsevier B.V. - PublicationMacroscopic properties of liquid-solid circulating fluidized bed with viscous liquid medium(01-01-2011)
;Vidyasagar, Shilapuram ;Krishnaiah, K.Experiments were conducted in a liquid-solid circulating fluidized bed to study the effect of liquid viscosity and solids inventory on pressure gradient, critical transitional liquid velocity, onset average solids holdup, axial solids holdup distribution, average solids holdup and solids circulation rate in circulating fluidization regime with riser operated in fixed inventory mode. The results indicate that critical transitional liquid velocity decreases with increase in liquid viscosity. The onset average solids holdup, on the other hand, increases with increase in either auxiliary liquid velocity or solids inventory. The variation of axial solids holdup distribution, average solids holdup and solids circulation rate with liquid viscosity when solid inventory was 0.15. m was dissimilar with either 0.25. m or 0.35. m solid inventory. Correlations were proposed for estimating the average solids holdup and are satisfactorily compared with experimental values. © 2010 Elsevier B.V. - PublicationEffect of bivalent cation inorganic salts on isobaric vapor-liquid equilibrium of methyl acetate-methanol system(15-10-2014)
;Dhanalakshmi, J.; Balakrishnan, A. R.The salt effect of four inorganic salts, namely; zinc nitrate, calcium nitrate, magnesium nitrate and magnesium chloride on the vapor liquid equilibria of the binary methyl acetate-methanol system was investigated using a modified Othmer still at 1atm. The salting out effect of methyl acetate was studied at different salt concentrations. For a salt concentration of 5wt%, it was found that zinc nitrate gives better salting out effect than calcium and magnesium nitrate. Magnesium chloride also shows a salting out effect, but could not eliminate the azeotrope completely, even at higher salt concentrations. It is observed that the bivalent cation salts (ZnNO3, CaNO3, MgNO3 and MgCl2) had greater salting out effect than univalent cation salts (LiNO3,LiCl) reported earlier. Further, salting out coefficients were calculated using the scaled particle theory. The experimental vapor-liquid equilibrium data with the salts was compared with that calculated using the scaled particle theory, but only qualitative agreement was observed. - PublicationHydrodynamics and flow regimes in turbulent bed contactor with non-Newtonian liquids(01-02-2012)
;Bruce, A. E.R. ;Swathi, P. ;Krishnaiah, K.The flow regimes normally encountered in a turbulent bed contactor (TBC) are static, partially fluidised, completely fluidised and flooding regimes. Experiments were conducted in a TBC operating in Type I mode to identify the flow regimes with non-Newtonian liquid. Flow regime transition velocities were obtained from the pressure drop and bed expansion measurements at various operating and geometric variables. The variables include apparent viscosity of the liquid, gas and liquid velocities, size and density of the particles, and static bed height. The effect of the above variables on delineation of flow regime transition was studied. Based on the experimental data, correlations were proposed for predicting the transition velocity from one regime to the other. The influence of the variables on regime transition velocities is more or less similar to that observed for Newtonian liquids. © 2011 Canadian Society for Chemical Engineering. - PublicationOptimization of air distribution in direct reduction process in rotary kilns(01-01-1999)
;Ramakrishnan, V.An algorithm for optimization of the air distribution in direct reduction process in rotary kilns akin to the SL/RN process is proposed, based on Pontryagin's continuous maximum principle. The optimum air distribution has been obtained for given operating conditions. The optimum air distribution has been found to have a definite pattern with small changes due to variation in process conditions. Air distribution has been found to be the most important parameter, which could be suitably chosen to obtain desired operating conditions. The influence of operating parameters, such as iron and carbon concentration in the charge, oxide and coal reactivity, have been studied and the process behaviour has been analyzed. Performance of the process has been observed to improve for an increase in oxide and coal reactivity and iron and carbon concentrations in the charge. - PublicationStudies on segregation of binary mixture of solids in a continuous fast fluidized bed. Part I. Effect of particle density(01-05-2008)
;Palappan, K. GaneshSegregation of binary mixture of solids was experimentally investigated in a continuous fast fluidized bed of 69 mm i.d. and 3.65 m high with air as the separation medium. The feed is a binary mixture of solid particles of same size, but different density. The variables include superficial gas velocity, solids feed rate and feed composition. It was observed that, at steady state, there exists physical equilibrium between the evolved flotsam and the residual jetsam when the granular solids are in fluid-like state. The phase diagram was constructed from the experimental observations. It shows the range for segregation, behavior of the fluidized bed and the distribution of the flotsam and jetsam, which can be understood by analogy with the distillation of the binary liquid mixture. The effect of the solids feed rate and feed composition on equilibrium distribution of the flotsam and jetsam was studied. © 2007 Elsevier B.V. All rights reserved. - PublicationInfluence of feed entry on the segregation of a binary mixture of solids in a continuous fast fluidized bed(07-12-2011)
;Palappan, K. GaneshStudies on the influence of feed entry on segregation using continuous fast fluidization is not clearly understood even though studies are available on the segregation of particles in continuous bubbling/turbulent fluidized beds. In the present study, four different feed inlet positions are selected and tested in a 69 mm ID and 3.65 m height continuous fast fluidized bed. The feed is a binary mixture of solid particles of the same size, but different density. The inimitable observations noticed at various feed locations on fluidization behavior with segregation is discussed. Change in the feed inlet height of the fluidized bed is reflected drastically on the compositions of top and bottom products. Disparate behavior of continuous fluidization is noticed at selected feed inlet positions. Operation is not stable due to either particle congestion in the feeding line or nonuniform discharge of solids from the fluidized bed when the feed inlet position is located close to distributor. Further an enhanced-feed inlet location created a particles cloud above the dense phase. Excess of feed inlet height transformed the binary mixture severance and freeboard height. The optimum operating gas velocity required for maximum separation of both species is identified at every feed entry for different feed rates. A unique feed entry location is recognized for maximum separation of both the species and minimum gas. © 2011 American Chemical Society.