PREDICTION OF GAS HOLD-UP IN A COMBINED LOOP AIR LIFT FLUIDIZED BED REACTOR USING NEWTONIAN AND NON-NEWTONIAN LIQUIDS

Many experiments have been conducted to study the hydrodynamic characteristics of column reactors and loop reactors. In this present work, a novel combined loop airlift fluidized bed reactor was developed to study the effect of superficial gas and liquid velocities, particle diameter, fluid properties on gas holdup by using Newtonian and non-Newtonian liquids. Compressed air was used as gas phase. Water, 5% n-butanol, various concentrations of glycerol (60 and 80%) were used as Newtonian liquids, and different concentrations of carboxy methyl cellulose aqueous solutions (0.25, 0.6 and 1.0%) were used as non-Newtonian liquids. Different sizes of spheres, Bearl saddles and Raschig rings were used as solid phases. From the experimental results, it was found that the increase in superficial gas velocity increases the gas holdup, but it decreases with increase in superficial liquid velocity and viscosity of liquids. Based on the experimental results a correlation was developed to predict the gas hold-up for Newtonian and non-Newtonian liquids for a wide range of operating conditions at a homogeneous flow regime where the superficial gas velocity is approximately less than 5 cm/

DTM-Pade Approximants for MHD Flow with Suction/Blowing

In this paper, we study theoretically the magnetic effect of Blasius equation with suction/blowing. The similarity transformations are applied to reduce the governing partial differential equations to a set of nonlinear ordinary differential equations in dimensionless form. A mathematical technique, namely the Differential Transform Method (DTM), is used to solve the nonlinear differential equations under appropriate boundary conditions, in the form of series with easily computable terms. Then, Pade approximants are applied to the solutions to increase the convergence of the given series. The combined DTM-Pade procedure is implemented directly without requiring linearization, discretization or perturbation. Graphical results are presented to investigate influence of the Magnetic field on the velocity profiles

Acoustic pressure oscillation effects on mean burning rates of plateau propellants

Combustion instabilities constitute a well pronounced problem in all large rocket motors due to the inherent acoustic pressure oscillations established based on the port geometries. Suppression of the combustion instabilities in the solid rocket motor is required for controlling the mean burning rate variation which arises due to the interaction of acoustic pressure wave with propellant combustion. An experimental study has been carried out to investigate the effects of acoustic pressure oscillations on mean burning rates of non-aluminized and aluminized propellants which exhibit low pressure exponent index (n) in the burning rate trends. Steady and unsteady mean burning rates are determined from combustion photography method using a window bomb test facility over the pressure range of 17 MPa. A rotary valve is coupled with the window bomb setup to generate acoustic pressure oscillations inside the test chamber (cylindrical pressure vessel), which imposes the required frequencies of 140, 180 and 240 Hz respectively. The acoustic pressure amplitudes are varied from 0.04% to 1.4% of the mean chamber pressure. Both non aluminized propellants and aluminized propellants have shown significant enhancement in the mean burning rate due to the fluctuations imposed by acoustic pressure amplitudes and frequencies on the propellant combustion. The enhancement in the mean burning rate also depends upon dynamic response of the flame to the excited frequencies and acoustic pressure amplitudes. The plateau burning behaviour of the non-aluminized propellant is completely distorted whereas it is retained in aluminized compositions. Conversely, it also shifts the mean pressure range of plateau burning rate trend. The maximum burning rate augmentation factors resulted from imposed acoustic pressure wave on non-aluminized and aluminized propellants are observed as 1.27 and 1.47 respectively

Acorus calamus rhizome extract mediated biosynthesis of silver nanoparticles and their bactericidal activity against human pathogens

Silver nanoparticle (AgNP) synthesis and characterization is an area of vast interest due to their broader application in the fields of science and technology and medicine. Plants are an attractive source for AgNP synthesis because of its ability to produce a wide range of secondary metabolites with strong reducing potentials. Thus, the present study describes the synthesis of AgNPs using aqueous rhizome extract of Acorus calamus (sweet flag). The AgNP formation was evaluated at different temperatures, incubation time and concentrations of AgNO3 using Response surface methodology based Box–Behnken design (BBD). The synthesized AgNPs were characterized by UV–Visible spectroscopy, Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS). The surface plasmon resonance found at 420 nm confirmed the formation of AgNPs. SEM images reveal that the particles are spherical in nature. The EDS analysis of the AgNPs, using an energy range of 2–4 keV, confirmed the presence of elemental silver without any contamination. The antibacterial activity of synthesized AgNPs was evaluated against the clinical isolates Staphylococcus aureus and Escherichia coli and it was found that bacterial growth was significantly inhibited in a dose dependent manner. The results suggest that the AgNPs from rhizome extract could be used as a potential antibacterial agent for commercial application

Eco-friendly biosynthesis and characterization of silver nanoparticles using Tinospora cordifolia (Thunb.) Miers and evaluate its antibacterial, antioxidant potential

AbstractThe present study reports an eco-friendly, rapid and easy method for synthesis of silver nanoparticles (AgNPs) using Tinospora cordifolia as a reducing and capping agent. The different factor such as silver nitrate (AgNO3) concentration, fresh weight of T. cordifolia leaf, incubation time, and pH affecting silver reduction was investigated using Response surface methodology based Box–Behnken design (BBD). The optimum conditions were AgNO3 (1.25 mM), incubation time (15 h), Temperature (45 °C) and pH (4.5). T. cordifolia leaf extract can reduces silver ions into AgNPs within 30 min after heating the reaction mixture (60 °C) as indicated by the developed reddish brown color. The UV-Vis spectrum of AgNPs revealed a characteristic surface plasmon resonance (SPR) peak at 430 nm. AgNPs were characterized X-ray diffraction (XRD) revealed their crystalline nature and their average size of nanoparticles was 30 nm as determined by using Scherrer's equation. Fourier transform infrared (FTIR) spectroscopy affirmed the role of T. cordifolia leaf extract as a reducing and capping agent of silver ions. Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) showed spherical shaped and confirming presence of elemental silver. The synthesized AgNPs was found higher antioxidant activity than plant extract by dot plot assay. In addition, antibacterial activity against Staphylococcus sp. (NCBI-Accession: KC688883.1) and Klebsiella sp. (NCBI-Accession: KF649832.1), showed maximum zone of inhibition of 13 mm and 12.3 mm, respectively, at 10 μg/mL of AgNPs. From the results it is suggested that the synthesized AgNPs showed higher antioxidant and antibacterial activity than the plant extract, thus signification of the present study is the production of biomedical products