A two dimensional simulation study of liquid-liquid (water and cyclohexane) two phase ow in Yjunc... more A two dimensional simulation study of liquid-liquid (water and cyclohexane) two phase ow in Yjunction microchannels with and without obstructions has been studied numerically using volume of uid method (VOF). The Y-junction angle of inclination between inlets of the two phases was varied in three equal steps. Various types of ow pattern were visualized for different concentrations of liquids, and velocity elds were also checked to quantify mixing e ciency. On the basis of mixing e ciency and mixing length an optimal angle was obtained. A comparison of mixing e ciencies with and without obstructions in mixing zone clearly indicates the usefulness of microchannel with obstructions. The simulated results obtained were also compared and validated with existing theoretical and experimental results. As angle of inclination is one of the key parameter in uencing the mixing of components in microchannels apart from velocities of the two phases, so two approaches were used to predict ow behavior and mixing e ciency, rstly by varying the angle of inclination in three steps (60°, 90° and 120) keeping liquid velocities constant and secondly by varying the velocity of liquids (from 0.025 ms − 1 to 0.5 ms − 1) keeping angle of inclination constant. Finally, 120° was observed as the optimal angle of inclination for mixing of liquids. In addition, heat effects on mixing of liquids in microchannel wall temperature ranges 300 to 350 K were also studied and discussed. Pressure of the Y-junction at different angles of two inlets with different capillary number (C a) as well as different Reynolds no (Re) was also analyzed to investigate ow patterns mechanism.
International Journal of Chemical Reactor Engineering, Nov 11, 2016
Compared with arsenate [As(V)], arsenite [As(III)] is more toxic to human health and more difficu... more Compared with arsenate [As(V)], arsenite [As(III)] is more toxic to human health and more difficult to be removed from aqueous solution. In this study, a novel adsorbent, Zr(IV)-loaded collagen fiber (ZrCF), was prepared, and its adsorption characteristics to As(III) were investigated. It was found that ZrCF can effectively remove As(III) from aqueous solution in the pH range of 9.0-12.0. The maximum adsorption capacity of As(III) by ZrCF reached up to 54.02 mg As/g when the initial concentration of As(III) was 73.00 mg/L at 303 K and pH 11.0. The adsorption isotherms of ZrCF to As(III) were well fitted by the Langmuir-Freundlich equation. The adsorption kinetic experimental data were well described by the pseudo-second-order rate equation, and the calculated adsorption capacities were close to those obtained by experiments. The leakage of zirconium loaded on ZrCF was negligible during adsorption process. Therefore, this study indicates that ZrCF is a promising adsorbent for As(III) removal from aqueous solution.
Chemical and Biochemical Engineering Quarterly, Jul 16, 2016
Microfluidic devices are quite important for process industries, as these devices can intensify h... more Microfluidic devices are quite important for process industries, as these devices can intensify heat and mass transfer in two-phase reaction systems. Two-phase reaction systems, such as gas-liquid and liquid-liquid reactions with certain limitations have already been carried out in microfluidic systems by a few authors. However, these concepts are still under development and a detailed understanding of the hydrodynamics involve is required. Hydrodynamics studies are inherently crucial to provide precise reaction conditions and identify asymptotic performance limits. In the present work, Computational Fluid Dynamics (CFD) simulation was carried out to investigate the hydrodynamics involved in the T-junction enhanced microchannel. The slug formation, slug size, slug shape, and pressure drop in the enhanced microchannel were predicted using the volume of fluid (VOF) for water-cyclohexane system. The effects of obstruction spacing on pressure drop, slug lengths, and mixing within the slug were also examined. This study revealed that mixing enhances tremendously within the slug and at the interface in the enhanced microchannel, but with slightly greater pressure drop. However, an increase in obstruction spacing affects the slug formation, unit slug length, and pressure drop.
Chemical and Biochemical Engineering Quarterly, Oct 1, 2007
Bubble column (BC) or slurry bubble column (SBC) reactor has emerged as one of the most promising... more Bubble column (BC) or slurry bubble column (SBC) reactor has emerged as one of the most promising devices in chemical, biochemical and environmental engineering operations because of its simple construction, isothermal conditions, high heat and mass transfer rates, and on-line catalyst addition and withdrawal. The present work has been carried out to characterize the dynamics of three-phase flow in cylindrical bubble column, run under homogeneous bubble flow and heterogeneous flow conditions using CFD (Computational Fluid Dynamics) simulation. The investigation has been done to study the flow pattern of three-phase bubble column along with parametric studies. The simulations were performed for air-water-glass beads in a bubble column of H = 0.6 m height, D i = 0.1 m and d s = 0.05 m sparger diameter to study the flow pattern. Eulerian-Eulerian three-phase simulations with k-e turbulence for liquid phase were carried out using the commercial flow simulation software CFX-5.6, with a focus on characterizing the dynamics properties of gas liquid solid flows. The model has been validated using available experimental data and is in good agreement. Detail study of the flow pattern in three-phase bubble column has been carried out and flow pattern has been presented in the form of contour and vector plots. The results presented are useful for understanding the dynamics of gas liquid solid flows in bubble column and provide a basis for further development of CFD model for three phase systems.
Chemical and Biochemical Engineering Quarterly, Oct 20, 2021
A novel and efficacious inorganic-organic hybrid material was synthesized by immobilizing Cu(II)-... more A novel and efficacious inorganic-organic hybrid material was synthesized by immobilizing Cu(II)-Schiff's base complex on silica-gel using 3-(2-aminoethylamino) propyltrimethoxysilane as linker and 1,3-diphenyl-1,3-propanedione for Schiff's base formation. The hybrid was characterized by FT-IR, DRUV-Vis, Solid State 13 C CPMAS NMR, Powder-XRD, SEM, ICP-AES, EDX and TGA and EPR techniques. Catalytic ability of the hybrid was evaluated for oxidative degradation of Reactive Black 5, and oxidation of few representative organic substrates, viz., tetralin, cyclohexane, cyclohexanol, and cyclopentanol, where the hybrid catalyst decomposes H 2 O 2 to generate ·OH free radicals. Influence of various reaction parameters, i.e., H 2 O 2 concentration, catalyst concentration, and temperature, on dye degradation process was studied and best reaction conditions for maximum degradation of RB5 were also determined. The catalyst gave a high dye degradation efficiency of 91 %, and a good product yield of 42.61 %, 41.09 %, 40.54 %, and 38.44 % for conversion of tetralin (with selectivity of 74.23 % and 25.77 % for tetralone and tetralol, respectively), cyclohexane (with selectivity of 75.05 % and 24.95 % for cyclohexanone and cyclohexanol, respectively), cyclohexanol (with 100 % selectivity for cyclohexanone), and cyclopentanol (with 100 % selectivity for cyclopentanone), respectively. Easy separation, reusability, and good catalytic activity leading to possible development of eco-friendly industrial manufacturing process are the motivating factors for using the synthesized novel material.
Chemical and Biochemical Engineering Quarterly, Oct 7, 2017
In this study, bubble dynamics and frictional pressure drop associated with gas liquid two-phase ... more In this study, bubble dynamics and frictional pressure drop associated with gas liquid two-phase slug flow regime in adiabatic T-junction square microchannel has been investigated using CFD. A comprehensive study on the mechanism of bubble formation via squeezing and shearing regime is performed. The randomness and recirculation profiles observed in the squeezing regime are significantly higher as compared to the shearing regime during formation of the slug. Further, effects of increasing gas velocity on bubble length are obtained at fixed liquid velocities and simulated data displayed good agreement with available correlations in literature. The frictional pressure drop for slug flow regime from simulations are also obtained and evaluated against existing separated flow models. A regression correlation has also been developed by modifying C-parameter using separated flow model, which improves the prediction of two-phase frictional pressure drop data within slug flow region, with mean absolute error of 10 %. The influences of fluid properties such as liquid viscosity and surface tension on the two-phase frictional pressure drop are also investigated and compared with developed correlation. The higher liquid viscosity and lower surface tension value resulted in bubble formation via shearing regime.
In this work, the effect of different vortex generators on fin-plate heat exchanger performance w... more In this work, the effect of different vortex generators on fin-plate heat exchanger performance with a triangular channel cross-section is examined. The analysis is done using finite volume method. The effects of vortex generators in a channel are investigated by consideration of channel temperature and heat transfer coefficient. Six different vortex generators including a simple rectangular vortex generator (SRW), rectangular trapezius vortex generator (RTW), angular rectangular vortex generator (ARW), Wishbone vortex generators (WW), intended vortex generator (IVG) and wavy vortex generator (WVG) have been investigated. The observations suggest that simple rectangular vortex generator increases the heat transfer of finplate heat exchanger more than other models. This vortex generator increases heat transfer in the heat exchanger by 7%. However, vortex generators increase the pressure drop in heat exchanger. In addition, by increasing the height of the vortex generators the heat transfer rate is increased and the best angle of attack for the installation of vortex generator is 45 o .
The stringent laws and tight regulation on heavy metal bearing wastewaters being discharged into ... more The stringent laws and tight regulation on heavy metal bearing wastewaters being discharged into the water stream lead to emergence of technically advanced and super effective treatment methods. Heavy metal contaminated aqueous streams have become a global concern due to their carcinogenicity and delirious effects on human health. In particular, the health hazards of mercury include adverse effect on central nervous system, pulmonary and kidney functions, etc. Having a maximum discharge limit of 0.001 mg/L, which is the lowest amongst other heavy metals, mercury contamination has become a matter of global concern. In the present study, TiO2 having a proven track record for its affinity for heavy metals was lab synthesized in the form of fiber mats and tested for its adsorptive behaviour towards Hg(II) in aqueous system. The electrospinned nanofibers possessed smooth morphology and very high surface area ≈ 740 m 2 /g. The batch adsorption experiments showed titania nanofibers possessed great affinity towards Hg(II). At the most optimized conditions the removal percentage went remarkably high to 95.5% with initial Hg(II) concentration of 0.01 mg/L. Since the rate limiting steps in adsorption are of vital importance in order to define the rate parameters for design purposes, the present study takes into account External mass transfer, Weber and Morris and Boyd mass transfer diffusion models for Hg(II) adsorption on lab synthesized titania nanofibers. The equilibrium data were then analyzed using Langmuir, Freundlich and Temkin sorption models and the characteristic sorption parameters for each isotherm were determined. The Mass transfer mechanism appeared to be film diffusion controlled and data fitted best to Freundlich isotherm with regression value of 0.991. The discussion also focuses on few of the recently used adsorbents for Hg(II) uptake and their comparison with the present study on the basis of removal percentage and kinetics involved. Promising adsorbent characteristics and rapid Hg(II) uptake makes this process a convenient one.
This paper presents an experimental investigation on nucleate pool boiling of saturated methanol ... more This paper presents an experimental investigation on nucleate pool boiling of saturated methanol on uncoated as well as copper-coated mild steel heating tubes of various thicknesses at atmospheric and subatmospheric pressures. It also includes the effect of heat flux, pressure and coating thickness on the boiling heat transfer coefficient of coated tube surfaces. Heat flux was progressively increased from 15,670.20 to 43,151.57 W/m 2 in six steps and pressure from 23.02 to 98.68 kN/m 2 in five steps. Boiling characteristics on such surfaces are compared with those on uncoated ones. Also, a criterion for enhanced boiling of methanol on copper-coated tubes is described.
Single phase fluid flow through series of uniform microchannels connected via transition section ... more Single phase fluid flow through series of uniform microchannels connected via transition section (converging-diverging section with or without throat) was analytically and numerically studied to characterize the flow within the channel and in the transition sections. Three sets of microchannels of diameters 100, 184, and 249 μm were considered for investigation. Each set contains 10 numbers of microchannels of length 20 mm, connected to each other in series via transition sections. Transition section consists of either converging-diverging section with throat or without throat. The effect of non-uniformity in microchannels on pressure drop was determined by passing water/air through the set of channels for Reynolds number 50 to 1000. Compressibility and rarefaction effects in transition sections were also tested analytically and numerically for air flow. The analytical and numerical results show that these configurations can be used in enhancement of transport processes. However, co...
International Journal of Chemical Engineering and Applications, 2017
The present investigation focuses on testing the adsorptive behaviour of laboratory synthesized t... more The present investigation focuses on testing the adsorptive behaviour of laboratory synthesized titania nanofibers towards Hg(II) and Pb(II) in the aqueous system. The BET analysis confirmed that the electrospinned nanofibers were confirmed to possess a large surface area of 740 m 2 /g. The fiber mats were analysed by EDX, which confirmed the adsorption of the metals on the fiber surface. SEM revealed the smooth morphology and continuous nature of the fibers. The effect of pH, contact time and adsorbent dose is compared for both the metals. At the most optimized conditions, highest uptake of 95.5% was observed for 0.01 mg/L Hg(II) concentration while it was 83.8% for 0.5 mg/L Pb(II) concentration. Since the rate limiting steps in adsorption are of vital importance in order to define the rate parameters for design purposes, the present study takes into account Weber and Morris and Boyd mass transfer diffusion models for both Hg(II) and Pb(II) adsorption on titania nanofibers. The equilibrium data were then analyzed using Langmuir and Freundlich sorption models and the characteristic sorption parameters for each isotherm were determined. The discussion also focuses on few of the recently used adsorbents for heavy metal uptake and their comparison with the present study.
Titania nanofibers were synthesized using a combination of sol-gel and electro-spinning technique... more Titania nanofibers were synthesized using a combination of sol-gel and electro-spinning techniques followed by calcination to eliminate organic phase. Effects of precursor and polymer concentration and temperature on fiber morphology were studied. The BET adsorption, FTIR spectroscopy, SEM and XPS techniques were used to characterize titania nanofibers. The obtained fibers were properly aligned and smooth. Presence of titanium(IV) and Ti-O bonds were confirmed. The fibers exhibited a large surface area (740.2 m 2 /g) and high uptake efficiency (95.5 %) for mercury(II). Adsorption equilibrium obeyed Freundlich isotherm and process followed pseudo second order kinetics.
In this present work, a numerical study was conducted for the formation of a slug bubble for shea... more In this present work, a numerical study was conducted for the formation of a slug bubble for shear thinning non-Newtonian fluid in a cross-junction 2-D square horizontal microchannel. Carboxymethyl cellulose (CMC) of concentration 0.2 (w/w%) percent was used as a continuous phase that shows the shear thinning behavior of non-Newtonian fluid and Nitrogen (N2) was used as the discrete phase. The pressure-based double precision solver was used in ANSYS FLUENT 2021 R2 with the volume of fluid (VOF) method. The finite volume method is applied for the discretization of the continuity and momentum equation. This article also focuses on the fluctuation of static pressure, mechanism of slug, annular, and churn annular flow i.e., obtained by the variation in the inlet velocities. On the other hand, a concept that was applied in this work was also validated with the prior literature data.
This paper theoretically studied pressure drop variation in microchannels having different cross ... more This paper theoretically studied pressure drop variation in microchannels having different cross sections (circular, rectangular, square, trapezoidal, triangular, elliptical, parallel plate, co-centric circles, hexagonal, wavy, smoothed or rounded corners cross sections, and rhombus) for single phase Newtonian fluid (gas and liquid) flow. Based on 41 years (approximately) prior literature (1981–till now), 249 articles were studied and number of correlations of pressure drop calculation in microchannels with or without friction factor equation for four cross sections i.e., rectangular, square, circular, trapezoidal, wavy and triangular is collected and also mentioned their limitations at one place. Other than these four cross sections, there is very few experimental/numerical works was present in the literature. A comparable study was performed for laminar as well as turbulent friction factor to calculate the pressure drop with the help of classical theory for gas and liquid flow in ...
A two dimensional simulation study of liquid-liquid (water and cyclohexane) two phase ow in Yjunc... more A two dimensional simulation study of liquid-liquid (water and cyclohexane) two phase ow in Yjunction microchannels with and without obstructions has been studied numerically using volume of uid method (VOF). The Y-junction angle of inclination between inlets of the two phases was varied in three equal steps. Various types of ow pattern were visualized for different concentrations of liquids, and velocity elds were also checked to quantify mixing e ciency. On the basis of mixing e ciency and mixing length an optimal angle was obtained. A comparison of mixing e ciencies with and without obstructions in mixing zone clearly indicates the usefulness of microchannel with obstructions. The simulated results obtained were also compared and validated with existing theoretical and experimental results. As angle of inclination is one of the key parameter in uencing the mixing of components in microchannels apart from velocities of the two phases, so two approaches were used to predict ow behavior and mixing e ciency, rstly by varying the angle of inclination in three steps (60°, 90° and 120) keeping liquid velocities constant and secondly by varying the velocity of liquids (from 0.025 ms − 1 to 0.5 ms − 1) keeping angle of inclination constant. Finally, 120° was observed as the optimal angle of inclination for mixing of liquids. In addition, heat effects on mixing of liquids in microchannel wall temperature ranges 300 to 350 K were also studied and discussed. Pressure of the Y-junction at different angles of two inlets with different capillary number (C a) as well as different Reynolds no (Re) was also analyzed to investigate ow patterns mechanism.
International Journal of Chemical Reactor Engineering, Nov 11, 2016
Compared with arsenate [As(V)], arsenite [As(III)] is more toxic to human health and more difficu... more Compared with arsenate [As(V)], arsenite [As(III)] is more toxic to human health and more difficult to be removed from aqueous solution. In this study, a novel adsorbent, Zr(IV)-loaded collagen fiber (ZrCF), was prepared, and its adsorption characteristics to As(III) were investigated. It was found that ZrCF can effectively remove As(III) from aqueous solution in the pH range of 9.0-12.0. The maximum adsorption capacity of As(III) by ZrCF reached up to 54.02 mg As/g when the initial concentration of As(III) was 73.00 mg/L at 303 K and pH 11.0. The adsorption isotherms of ZrCF to As(III) were well fitted by the Langmuir-Freundlich equation. The adsorption kinetic experimental data were well described by the pseudo-second-order rate equation, and the calculated adsorption capacities were close to those obtained by experiments. The leakage of zirconium loaded on ZrCF was negligible during adsorption process. Therefore, this study indicates that ZrCF is a promising adsorbent for As(III) removal from aqueous solution.
Chemical and Biochemical Engineering Quarterly, Jul 16, 2016
Microfluidic devices are quite important for process industries, as these devices can intensify h... more Microfluidic devices are quite important for process industries, as these devices can intensify heat and mass transfer in two-phase reaction systems. Two-phase reaction systems, such as gas-liquid and liquid-liquid reactions with certain limitations have already been carried out in microfluidic systems by a few authors. However, these concepts are still under development and a detailed understanding of the hydrodynamics involve is required. Hydrodynamics studies are inherently crucial to provide precise reaction conditions and identify asymptotic performance limits. In the present work, Computational Fluid Dynamics (CFD) simulation was carried out to investigate the hydrodynamics involved in the T-junction enhanced microchannel. The slug formation, slug size, slug shape, and pressure drop in the enhanced microchannel were predicted using the volume of fluid (VOF) for water-cyclohexane system. The effects of obstruction spacing on pressure drop, slug lengths, and mixing within the slug were also examined. This study revealed that mixing enhances tremendously within the slug and at the interface in the enhanced microchannel, but with slightly greater pressure drop. However, an increase in obstruction spacing affects the slug formation, unit slug length, and pressure drop.
Chemical and Biochemical Engineering Quarterly, Oct 1, 2007
Bubble column (BC) or slurry bubble column (SBC) reactor has emerged as one of the most promising... more Bubble column (BC) or slurry bubble column (SBC) reactor has emerged as one of the most promising devices in chemical, biochemical and environmental engineering operations because of its simple construction, isothermal conditions, high heat and mass transfer rates, and on-line catalyst addition and withdrawal. The present work has been carried out to characterize the dynamics of three-phase flow in cylindrical bubble column, run under homogeneous bubble flow and heterogeneous flow conditions using CFD (Computational Fluid Dynamics) simulation. The investigation has been done to study the flow pattern of three-phase bubble column along with parametric studies. The simulations were performed for air-water-glass beads in a bubble column of H = 0.6 m height, D i = 0.1 m and d s = 0.05 m sparger diameter to study the flow pattern. Eulerian-Eulerian three-phase simulations with k-e turbulence for liquid phase were carried out using the commercial flow simulation software CFX-5.6, with a focus on characterizing the dynamics properties of gas liquid solid flows. The model has been validated using available experimental data and is in good agreement. Detail study of the flow pattern in three-phase bubble column has been carried out and flow pattern has been presented in the form of contour and vector plots. The results presented are useful for understanding the dynamics of gas liquid solid flows in bubble column and provide a basis for further development of CFD model for three phase systems.
Chemical and Biochemical Engineering Quarterly, Oct 20, 2021
A novel and efficacious inorganic-organic hybrid material was synthesized by immobilizing Cu(II)-... more A novel and efficacious inorganic-organic hybrid material was synthesized by immobilizing Cu(II)-Schiff's base complex on silica-gel using 3-(2-aminoethylamino) propyltrimethoxysilane as linker and 1,3-diphenyl-1,3-propanedione for Schiff's base formation. The hybrid was characterized by FT-IR, DRUV-Vis, Solid State 13 C CPMAS NMR, Powder-XRD, SEM, ICP-AES, EDX and TGA and EPR techniques. Catalytic ability of the hybrid was evaluated for oxidative degradation of Reactive Black 5, and oxidation of few representative organic substrates, viz., tetralin, cyclohexane, cyclohexanol, and cyclopentanol, where the hybrid catalyst decomposes H 2 O 2 to generate ·OH free radicals. Influence of various reaction parameters, i.e., H 2 O 2 concentration, catalyst concentration, and temperature, on dye degradation process was studied and best reaction conditions for maximum degradation of RB5 were also determined. The catalyst gave a high dye degradation efficiency of 91 %, and a good product yield of 42.61 %, 41.09 %, 40.54 %, and 38.44 % for conversion of tetralin (with selectivity of 74.23 % and 25.77 % for tetralone and tetralol, respectively), cyclohexane (with selectivity of 75.05 % and 24.95 % for cyclohexanone and cyclohexanol, respectively), cyclohexanol (with 100 % selectivity for cyclohexanone), and cyclopentanol (with 100 % selectivity for cyclopentanone), respectively. Easy separation, reusability, and good catalytic activity leading to possible development of eco-friendly industrial manufacturing process are the motivating factors for using the synthesized novel material.
Chemical and Biochemical Engineering Quarterly, Oct 7, 2017
In this study, bubble dynamics and frictional pressure drop associated with gas liquid two-phase ... more In this study, bubble dynamics and frictional pressure drop associated with gas liquid two-phase slug flow regime in adiabatic T-junction square microchannel has been investigated using CFD. A comprehensive study on the mechanism of bubble formation via squeezing and shearing regime is performed. The randomness and recirculation profiles observed in the squeezing regime are significantly higher as compared to the shearing regime during formation of the slug. Further, effects of increasing gas velocity on bubble length are obtained at fixed liquid velocities and simulated data displayed good agreement with available correlations in literature. The frictional pressure drop for slug flow regime from simulations are also obtained and evaluated against existing separated flow models. A regression correlation has also been developed by modifying C-parameter using separated flow model, which improves the prediction of two-phase frictional pressure drop data within slug flow region, with mean absolute error of 10 %. The influences of fluid properties such as liquid viscosity and surface tension on the two-phase frictional pressure drop are also investigated and compared with developed correlation. The higher liquid viscosity and lower surface tension value resulted in bubble formation via shearing regime.
In this work, the effect of different vortex generators on fin-plate heat exchanger performance w... more In this work, the effect of different vortex generators on fin-plate heat exchanger performance with a triangular channel cross-section is examined. The analysis is done using finite volume method. The effects of vortex generators in a channel are investigated by consideration of channel temperature and heat transfer coefficient. Six different vortex generators including a simple rectangular vortex generator (SRW), rectangular trapezius vortex generator (RTW), angular rectangular vortex generator (ARW), Wishbone vortex generators (WW), intended vortex generator (IVG) and wavy vortex generator (WVG) have been investigated. The observations suggest that simple rectangular vortex generator increases the heat transfer of finplate heat exchanger more than other models. This vortex generator increases heat transfer in the heat exchanger by 7%. However, vortex generators increase the pressure drop in heat exchanger. In addition, by increasing the height of the vortex generators the heat transfer rate is increased and the best angle of attack for the installation of vortex generator is 45 o .
The stringent laws and tight regulation on heavy metal bearing wastewaters being discharged into ... more The stringent laws and tight regulation on heavy metal bearing wastewaters being discharged into the water stream lead to emergence of technically advanced and super effective treatment methods. Heavy metal contaminated aqueous streams have become a global concern due to their carcinogenicity and delirious effects on human health. In particular, the health hazards of mercury include adverse effect on central nervous system, pulmonary and kidney functions, etc. Having a maximum discharge limit of 0.001 mg/L, which is the lowest amongst other heavy metals, mercury contamination has become a matter of global concern. In the present study, TiO2 having a proven track record for its affinity for heavy metals was lab synthesized in the form of fiber mats and tested for its adsorptive behaviour towards Hg(II) in aqueous system. The electrospinned nanofibers possessed smooth morphology and very high surface area ≈ 740 m 2 /g. The batch adsorption experiments showed titania nanofibers possessed great affinity towards Hg(II). At the most optimized conditions the removal percentage went remarkably high to 95.5% with initial Hg(II) concentration of 0.01 mg/L. Since the rate limiting steps in adsorption are of vital importance in order to define the rate parameters for design purposes, the present study takes into account External mass transfer, Weber and Morris and Boyd mass transfer diffusion models for Hg(II) adsorption on lab synthesized titania nanofibers. The equilibrium data were then analyzed using Langmuir, Freundlich and Temkin sorption models and the characteristic sorption parameters for each isotherm were determined. The Mass transfer mechanism appeared to be film diffusion controlled and data fitted best to Freundlich isotherm with regression value of 0.991. The discussion also focuses on few of the recently used adsorbents for Hg(II) uptake and their comparison with the present study on the basis of removal percentage and kinetics involved. Promising adsorbent characteristics and rapid Hg(II) uptake makes this process a convenient one.
This paper presents an experimental investigation on nucleate pool boiling of saturated methanol ... more This paper presents an experimental investigation on nucleate pool boiling of saturated methanol on uncoated as well as copper-coated mild steel heating tubes of various thicknesses at atmospheric and subatmospheric pressures. It also includes the effect of heat flux, pressure and coating thickness on the boiling heat transfer coefficient of coated tube surfaces. Heat flux was progressively increased from 15,670.20 to 43,151.57 W/m 2 in six steps and pressure from 23.02 to 98.68 kN/m 2 in five steps. Boiling characteristics on such surfaces are compared with those on uncoated ones. Also, a criterion for enhanced boiling of methanol on copper-coated tubes is described.
Single phase fluid flow through series of uniform microchannels connected via transition section ... more Single phase fluid flow through series of uniform microchannels connected via transition section (converging-diverging section with or without throat) was analytically and numerically studied to characterize the flow within the channel and in the transition sections. Three sets of microchannels of diameters 100, 184, and 249 μm were considered for investigation. Each set contains 10 numbers of microchannels of length 20 mm, connected to each other in series via transition sections. Transition section consists of either converging-diverging section with throat or without throat. The effect of non-uniformity in microchannels on pressure drop was determined by passing water/air through the set of channels for Reynolds number 50 to 1000. Compressibility and rarefaction effects in transition sections were also tested analytically and numerically for air flow. The analytical and numerical results show that these configurations can be used in enhancement of transport processes. However, co...
International Journal of Chemical Engineering and Applications, 2017
The present investigation focuses on testing the adsorptive behaviour of laboratory synthesized t... more The present investigation focuses on testing the adsorptive behaviour of laboratory synthesized titania nanofibers towards Hg(II) and Pb(II) in the aqueous system. The BET analysis confirmed that the electrospinned nanofibers were confirmed to possess a large surface area of 740 m 2 /g. The fiber mats were analysed by EDX, which confirmed the adsorption of the metals on the fiber surface. SEM revealed the smooth morphology and continuous nature of the fibers. The effect of pH, contact time and adsorbent dose is compared for both the metals. At the most optimized conditions, highest uptake of 95.5% was observed for 0.01 mg/L Hg(II) concentration while it was 83.8% for 0.5 mg/L Pb(II) concentration. Since the rate limiting steps in adsorption are of vital importance in order to define the rate parameters for design purposes, the present study takes into account Weber and Morris and Boyd mass transfer diffusion models for both Hg(II) and Pb(II) adsorption on titania nanofibers. The equilibrium data were then analyzed using Langmuir and Freundlich sorption models and the characteristic sorption parameters for each isotherm were determined. The discussion also focuses on few of the recently used adsorbents for heavy metal uptake and their comparison with the present study.
Titania nanofibers were synthesized using a combination of sol-gel and electro-spinning technique... more Titania nanofibers were synthesized using a combination of sol-gel and electro-spinning techniques followed by calcination to eliminate organic phase. Effects of precursor and polymer concentration and temperature on fiber morphology were studied. The BET adsorption, FTIR spectroscopy, SEM and XPS techniques were used to characterize titania nanofibers. The obtained fibers were properly aligned and smooth. Presence of titanium(IV) and Ti-O bonds were confirmed. The fibers exhibited a large surface area (740.2 m 2 /g) and high uptake efficiency (95.5 %) for mercury(II). Adsorption equilibrium obeyed Freundlich isotherm and process followed pseudo second order kinetics.
In this present work, a numerical study was conducted for the formation of a slug bubble for shea... more In this present work, a numerical study was conducted for the formation of a slug bubble for shear thinning non-Newtonian fluid in a cross-junction 2-D square horizontal microchannel. Carboxymethyl cellulose (CMC) of concentration 0.2 (w/w%) percent was used as a continuous phase that shows the shear thinning behavior of non-Newtonian fluid and Nitrogen (N2) was used as the discrete phase. The pressure-based double precision solver was used in ANSYS FLUENT 2021 R2 with the volume of fluid (VOF) method. The finite volume method is applied for the discretization of the continuity and momentum equation. This article also focuses on the fluctuation of static pressure, mechanism of slug, annular, and churn annular flow i.e., obtained by the variation in the inlet velocities. On the other hand, a concept that was applied in this work was also validated with the prior literature data.
This paper theoretically studied pressure drop variation in microchannels having different cross ... more This paper theoretically studied pressure drop variation in microchannels having different cross sections (circular, rectangular, square, trapezoidal, triangular, elliptical, parallel plate, co-centric circles, hexagonal, wavy, smoothed or rounded corners cross sections, and rhombus) for single phase Newtonian fluid (gas and liquid) flow. Based on 41 years (approximately) prior literature (1981–till now), 249 articles were studied and number of correlations of pressure drop calculation in microchannels with or without friction factor equation for four cross sections i.e., rectangular, square, circular, trapezoidal, wavy and triangular is collected and also mentioned their limitations at one place. Other than these four cross sections, there is very few experimental/numerical works was present in the literature. A comparable study was performed for laminar as well as turbulent friction factor to calculate the pressure drop with the help of classical theory for gas and liquid flow in ...
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Papers by Siraj Alam