Satyanarayanan S

The present study reports developing a bench-top Laser-Induced Breakdown Spectroscopy (LIBS) set up for the online analysis of powder samples without sample preparation. The powder particle blow-off during pulsed laser ablation was mitigated by adding a blow gas (an inert gas blown across the ablation surface) and a suction unit (for extraction of the blow gas and blown-off particle cloud) to the existing LIBS setup. The influence of a blow-gas combined with a suction unit on LIBS emission intensity from coal powder and flyash particles is studied in the present work. The effect of the blow gas flow rate and the suction pressure was studied on the LI-BS emission intensity and removal of the laser blown-off particle cloud. The combination gas flow at 2 lpm (liter per minute) flow rate and suction at 925 mbar (absolute) show an increase in the LIBS emission intensity and effective particle removal. The ratio of LIBS emission intensity of the powder sample and solid-target (pellet) sample improved from 0.25 without the Ar gas flow and the suction unit to 0.85, which is by a factor of 3.4 times with the proposed approach.

Dual-wavelength, broadband photoacoustic technique is demonstrated for measurement of multiple gas species using a supercontinuum laser source. H2O vapor and CO2 measurements are demonstrated near 1920 and 2000 nm.

Nanosecond and femtosecond laser Induced Breakdown Spectroscopy (ns- and fs-LIBS)were used for elemental analysis of Indian coal and ash. Emissions from C, Na, K, Al, Fe, Ca and molecular CN were identified and analyzed.

In this study we report polarization resolved intensity measurements for flyash and water aerosol, respectively, in an industrial stack like environment, for the purpose of developing a methodology for in-situ PM measurements in wet stacks. Flyash and water aerosols up to 4 (Formula presented.) mass concentration were seeded in a lab scale simulated industrial stack operated at velocities up to 15 m/s. Scattering of non-polarized (NP) and horizontally polarized light by these two aerosols were observed at (Formula presented.) back-scatter and (Formula presented.) forward-scatter angles for horizontal and vertical polarization states at the detector. Complete depolarization of horizontally polarized incident light was observed for ash at (Formula presented.) while negligible effects were observed for water. Thus the cross-polarization measurement in this angle, where the scattering energy from the mixed flow could directly represent the flyash concentration, can be the best possible measurement configuration for minimizing the impact of interference from water carryover in industrial emission stacks. Further, the change in depolarization ratio of the mixture (δm) when compared to flyash (δa) alone is proportional to the scattering intensity ratios of ash and water, respectively, and could be used to estimate the individual mass concentrations. With this development, we could propose the design of an instrument that can in-situ correct for errors from counting water droplet, and also enable real time estimation of individual mass concentrations. Copyright © 2020 American Association for Aerosol Research.

The study analyses correlations used to determine the condensation heat transfer coefficient of refrigerant mixtures, R410A and R407C, in a tube in tube condenser. Shah [1], Jaster and Kosky [2], Thome et al. [3], and Dobson and Chato [4] correlations have been considered. The study identifies the flow parameters which influence the accuracy of correlations. The accuracy of the considered correlations is studied against the identified flow parameters. The flow parameters are used as a deciding criterion to select the most accurate correlation for a given case. This leads to a hybrid approach involving multiple correlations. The hybrid approaches are more accurate in comparison to the individual correlations.

Redox flow batteries are being utilised as an attractive electrochemical energy storage technology for electricity from renewable generation. At present, the global installed capacity of redox flow battery is 1100 MWh. There are several parameters that significantly govern redox flow battery performance amongst which electrode activation, electrode material, felt compression, electrolyte additive, electrolyte temperature, membrane, and flow field design are notable. This review article presents an overview of the influence of individual components by comparing the performance of a parametrically modified cell with a default cell, which has 0% felt compression, inactivated electrode, zero electrolyte additives, and ambient condition operation. From the reviewed studies, electrode activation (thermal, chemical, laser perforation) and felt compression were identified as the most significant parameters. Electrolyte additive and flow field design were identified to be reasonably significant. Electrolyte temperature and membrane type were identified as the least significant amongst all the parameters. Based on this survey, a parametric matrix has been outlined that will aid researchers to identify appropriate parameters to focus research efforts onto improved redox flow battery performance.

Process industry mostly uses steam as an indispensable source of energy. We are presenting a technique to measure quality in real time where single laser diode tuning capabilities is being utilized to generate arbitrary modulated laser intensity for non-absorbing and absorbing wavelength of water vapor and eliminates uses of multiple laser source.

The origin, formation mechanism, and emission persistence time of atomic (C I) and molecular (CN Violet system and C2 Swan system) carbon emissions from coal plasma generated by laser ablation were studied using Time-resolved LIBS.

Renewable energy utilisation has become indispensable to attain carbon-zero goals in the near future. Given the intermittent nature of renewable energy sources, it is vital to have an efficient and steadfast storage medium to maintain a stable energy supply. Vanadium redox flow batteries (VRFB) are promising energy storage devices that can be utilised effectively in grid storage applications. Despite their advantages, VRFBs still struggle to compete with lithium-ion batteries in round-trip efficiency. The round-trip efficiency of VRFB can be maximised if all the physical and chemical parameters are optimised simultaneously. To do this, several experimental trials need to be performed to determine the individual and collective effects of the parameters. Hence, in this work, we built a data model for VRFB using literature data, and we revamped the model to be 90 % accurate in assessing the round-trip efficiency (energy efficiency) within the error range of ±2 %. Finally, we used the data model to optimise the parameters for improving the energy efficiency to around 97–98 % for a 4 cm2 active area cell at a current density of 50 mA cm−2. Researchers can utilise this approach for any batteries that need performance improvement with minimal experimental efforts.

The anticipated future growth in the electric vehicle market is driving research and development of alternative battery technologies to lithium batteries. Among the explored batteries, metal-air batteries are an exciting option given their high potential energy density. Currently, metal-air flow batteries have received more attention over conventional metal-air batteries due to their ability to reduce metal passivation. The separator for a metal-air flow battery should be both ion-conductive and partially hydrophobic to favour the ionic movement and suppress the electrolyte flooding on the cathode. In this work, we investigate the use of polyvinyl alcohol (PVA)-based potassium hydroxide (KOH) polymer gel electrolyte (KPGE) as a membrane separator for planar zinc-air flow battery (ZAFB). The KPGE samples, i.e., S20 and S33 with respective KOH wt.% of 20 and 33 were synthesised. Their surface morphology, porosity, tensile strength, and ionic conductivity were studied. Among the samples, S33 sample with higher KOH content showed higher ionic conductivity than S20 sample however the tensile strength of S33 sample was lower than the S20 sample. When tested in the battery, ZAFB with S33 sample demonstrated higher nominal voltage and improved polarisation characteristics when compared to the ZAFB with S20 sample.