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396 results on '"Verma, N. K."'

11. Investigation of continuous stirred tank reactors for improving the mixing in anaerobic digestion : A numerical study

Author

Thakur, H., Verma, N. K., Dhar, A., Powar, Satvasheel, Thakur, H., Verma, N. K., Dhar, A., and Powar, Satvasheel

Abstract

In this paper, mechanical impeller mixing has been analyzed through CFD which has proven to be a useful method for simulating mixing before manufacturing the digester. In this work, simulations were done for five different digester designs for TS level of 12.1%. While the fifth digester was cylindrical, the other four were cubical in design with varying impeller diameters and the number of impellers. The power law model was used to resemble the sewage sludge as a non-Newtonian fluid. The modified versions of dead volume and uniformity index were used along with velocity gradient and mixing energy level to quantify the quality of mixing. An analysis of the temperature distributions during mixing and heating was done using a thermal study. The operating speed of 250 rpm was finalized after testing at continuously increasing speeds from 50 to 600 rpm for a flat blade type impeller. As per the thermal model, a 250-W heater raised the temperature by around 15 °C in just 10 min. It was found that cylindrical vessels worked better than cubical digesters and larger impellers also helped in improving the mixing. The cylindrical digester which achieved about 67% homogeneity at a mixing energy level of around 0.95 W/m3, was the optimum design among the investigated digesters. © 2023 The Authors

Published
2023
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35. Molecular-engineering of Tb2O3@TiO2 complexes sensitized with N719 dye photoanodes and evaluation of their realistic efficiencies in DSSC systems.

Author

Kaur, Manveen, Kumar, Sanjeev, Singh, Rajwant, Verma, N. K., Kumar, Vanish, Younis, Sherif A., and Kim, Ki-Hyun

Abstract

Solar energy is a promising replacement for rapidly depleting, non-renewable fossil fuel resources. For the efficient capture and use of solar energy, we fabricated new unconventional N719 dye-sensitized solar cells (DSSC) based on Tb2O3@TiO2 nanoparticles (NPs) with crystallite sizes in the range of 5–10 nm. The effect of loading concentrations of Tb2O3 (e.g., 0.001 to 0.010 M) on the photovoltaic performance of DSSC@Tb2O3-TiO2 complexes was assessed for comparison with that of a pristine TiO2 photoanode under simulated solar light (100 mW/cm2). Furthermore, the solar energy conversion of Tb2O3@TiO2 NPs was studied and explained in relation to their photoluminescence, photocatalytic, and surface properties. A 22% improvement in the efficiency was achieved for incident photon capture and electricity conversion in the DSSC-Tb2O3@TiO2 photoanode (at 0.001 M Tb2O3) as compared with the TiO2-based photoanode (η= 1.88 vs. 1.54). Tb2O3@TiO2 is thus demonstrated to have improved photoelectrochemical properties with enhanced charge carrier separation based on the high adsorption capability (against sensitized N719 dye: 1.74 × 10–7 mol/cm2) and photocurrent density (6.13 mA/cm2) (e.g., relative to pristine TiO2 (1.01 × 10–7 mol/cm2 and 4.66 mA/cm2, respectively). Therefore, the prepared Tb2O3@TiO2 NPs are recommended for use in photoanode applications to achieve highly efficient up-conversion of solar energy. [ABSTRACT FROM AUTHOR]

Published
2023
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