Faculty Publications
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Publications by NITK Faculty
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Item Solid suspension and liquid phase mixing in solid-liquid stirred tanks(2009) Sardeshpande, M.V.; Sagi, A.R.; Juvekar, V.A.; Ranade, V.V.Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid-liquid suspensions were also studied. A new way of characterizing solid-liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid-liquid stirred tanks. © 2009 American Chemical Society.Item Synthesis, characterization & impedance studies of some new nano filtration membranes(Trans Tech Publications Ltd ttp@transtec.ch, 2010) Padaki, M.; Hegde, C.; Isloor, A.M.In the recent years membrane technology has gained significant attention from polymer chemists all around the world due to their attractive features such as efficiency, low costs, low energy costs and as effective solutions to longstanding problems in the chemical industries. Membrane technologies have been widely applied in the separation of liquids and even gases. Many separation problems can be solved economically by nanofiltration alone or in combination with other separation processes. This study aimed to synthesize polysulfone based nanofiltration membranes using DIPS (diffusion induced phase separation) technique. Newly synthesized polymer membranes were subjected to Infra red spectral and water uptake studies. Membranes were also characterized using electrochemical spectroscopy for their proton conducting property. Their surface morphology is visualized by SEM. © (2010) Trans Tech Publications.Item Electrospinning of non-woven poly(styrene-co-acrylonitrile) nanofibrous webs for corrosive chemical filtration: Process evaluation and optimization by Taguchi and multiple regression analyses(Elsevier, 2015) Senthil, T.; Anandhan, S.Nano-fibrous ultra-filtration membranes of poly(styrene- co-acrylonitrile) were produced from n-butanone solution by electrospinning. Effects of governing parameters on morphology and variation in diameter of the electrospun fibers were experimentally investigated by orthogonal experimental design. The process parameters were selected by Taguchi's method. Multiple regression analysis was used to obtain a quantitative relationship between selected electrospinning parameters and average fiber diameter and ANOVA was used to identify the statistically significant parameters and set the optimal level for each parameter. Confirmation experiment revealed a good agreement between the predicted values of the response obtained from optimum level parameters and the observed experimental values. © 2014 Elsevier B.V.Item Reusable floating polymer nanocomposite photocatalyst for the efficient treatment of dye wastewaters under scaled-up conditions in batch and recirculation modes(John Wiley and Sons Ltd vgorayska@wiley.com Southern Gate Chichester, West Sussex PO19 8SQ, 2019) Das, S.; Mahalingam, H.BACKGROUND: In the last decade, research on floating photocatalysts has increased rapidly with polymer substrates being a popular choice. However, most of the published work is on very small volumes and there is very little work on scale-up of such systems. RESULTS: Polystyrene–titanium dioxide nanocomposite floating films were prepared using a facile solvent casting method and tested for the photocatalytic degradation of four different dyes under UV irradiation. The prepared film was characterised by Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES) and profilometry. Scale-up studies were done in batch mode under optimised conditions, and for the larger reactor volume, the effect of recirculation was studied. Complete decolourisation of the model dye (Remazol Turquoise Blue) was observed within 80 min in the scaled-up batch process. In the recirculation mode, for a much larger volume of the dye solution, around 75% decolourisation in 6 h was observed. The reusability of the photocatalytic film was tested, and the results promise a minimum decolourisation efficiency of around 70%. Finally, total organic carbon (TOC) and liquid chromatography mass spectrometry (LC-MS) analysis were used to assess the degradation of the dye. The maximum TOC reduction observed was around 25% possibly due to the complex nature of the dye used in this study. The intermediate products of degradation were identified, and a tentative mechanism is suggested. CONCLUSION: This work demonstrates the recirculation aspects of the photocatalytic reactor under the scaled-up conditions for a complex dye. The prepared film showed excellent stability with satisfactory wastewater decontamination under UV irradiation even after repeated use. © 2019 Society of Chemical Industry. © 2019 Society of Chemical IndustryItem Failure Analysis of Cooling Tower Fan-Arm(Springer, 2020) Padasale, B.; Kumar, J.K.R.; Sondar, P.R.; Cadambi, S.; Hegde, S.R.This work presents failure investigation of cooling tower fan-arms commissioned in a chemical processing plant. The analysis aims at understanding the mechanism and root-cause of the failure. The investigation involves site visits, microstructural analysis, fracture surface analysis, hardness measurements, numerical stress analysis and experimental simulation. Work concludes that the fan-arms failed due to the lack of post-weld heat treatment, which caused localized stress-corrosion and pitting at critical locations that served as crack initiation sites. Fatigue loading condition and presence of residual stresses at the weld enabled easy propagation of cracks that led to recurring premature failure. Based on the root-cause and the mechanism identified in this analysis, proper pre-heating and post-weld heat treatment is recommended to relieve the residual stresses at the critical locations and thus to avoid/minimize such recurring failures in future. © 2020, ASM International.Item Failure Analysis of a Bucket Elevator Shaft(Springer, 2021) Gurudath, B.; Kumawat, K.K.; Tejaswi, V.; Sondar, P.R.; Rakshan Kumar, J.K.; Hegde, S.R.Present work investigates the in-service break down of a bucket elevator in a chemical processing plant. The elevator was used for lifting bulk Di-Ammonium Phosphate and broke down due to premature failure of a shaft made of EN19 steel. The investigation comprises a detailed metallurgical failure analysis involving site visit, visual inspection, fractography, and metallography. The investigation reveals that, about 2 years prior to the failure, the shaft was tack-welded to the sprocket hub and a gib-head key near the keyway to avoid the frequent loosening of the key. The inspection during the site visit confirms that the shaft-sprocket assembly was subjected to in-service jerky loading condition along with uneven stress distribution due to misaligned counterweight. The investigation concludes that a crack was initiated in the shaft at the heat affected zone of the tack-welded spot, propagated transversely by fatigue due to in-service cyclic loading, and terminated catastrophically by a brittle fracture during the service. Tack welding, coupled with uneven stress distribution in the shaft due to misaligned counterweight system, is adjudged the root cause of this failure. Suitable remedial measures are suggested to avoid such a failure in the future. © 2021, ASM International.Item Creep cavitation damage of K-type thermocouples(Elsevier Ltd, 2023) Rakshan Kumar, J.K.; Bhattacharjee, D.; Dsilva, P.; Praveen, R.; Hegde, S.R.This work investigates premature failure of K-Type thermocouples that were used in a chemical processing plant. The work presents a detailed metallurgical failure analysis involving, site visit, visual inspection, metallography, optical microscopy, scanning electron microscopy, and fractography. The analysis reveals that the thermocouple wires endured creep cavitation damage during service and eventually failed by creep-rupture. Interestingly, the influence of creep on the degradation of industrial thermocouples is not detected and reported thus far. By presenting analytical stress calculations using temperature dependent materials properties, the current work reveals that the thermal expansion mismatch between various materials of thermocouple causes high tensile stresses in the thermocouple wires during elevated temperature services. The work concludes that high tensile stresses at elevated temperature operation caused premature creep failure of the K-type thermocouples. © 2022Item High Velocity Air Fuel Spraying for Surface Restoration of Worn-out IN718(Springer, 2025) Sreerag, M.P.; Abhijith Vijay, V.; Babu, N.N.; Ali, S.S.; Cadambi, S.; Rajasekaran, B.This study explores the efficacy of high velocity air fuel (HVAF) spraying for repairing worn-out IN718 thrust collars used in the chemical industry. We investigated the characteristics and application potential of thick IN718 depositions for surface restoration, focusing on their adhesion. To evaluate microstructure and adhesion, approximately 2-mm-thick IN718 layers were deposited onto IN718 wrought coupons. The HVAF-sprayed layers were notably dense (99.5%) and exhibited excellent hardness, reaching 450 HV0.3, which suggests superior mechanical properties compared to the bulk material. A three-point bending test was conducted to assess the adhesion strength of these thick deposits. The results demonstrated excellent adhesion in both compressive (1281 MPa with > 2% strain) and tensile bending. Trusting in these promising substrate-layer interfacial adhesion characteristics, the investigation was extended to demonstrate the refurbishment of an actual worn-out industrial IN718 thrust collar. A 2-mm-thick IN718 deposition was applied to the entire worn area, and excess material was subsequently machined to achieve the desired surface finish for reuse. Overall, HVAF spray technology shows significant promise for developing thick metallic layers with excellent interfacial adhesion, providing a robust and viable solution for effectively refurbishing heavily worn metallic components and extending their service life. © ASM International 2025.Item Microstructure, Mechanical Properties, and Tribological Properties of Fe-Based Composite Coatings Reinforced with WC-Co and Cr3C2(Springer, 2025) Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.; Rahman, M.R.Fe-based (stainless steel 316L) coatings are widely employed in the aerospace, chemical processing, petrochemical, and marine industries owing to their low and stable price, excellent corrosion resistance, and durability. However, at elevated temperatures, their performance is limited due to wear. Thus, the current investigation incorporates tungsten carbide (WC-Co) and chromium carbide (Cr3C2) into the Fe-based coating to enhance its wear resistance at high temperatures. SS316L reinforced by 30% of WC-Co and Cr3C2 by mechanical mixture, then sprayed using high-velocity oxy fuel spraying method. Coating characteristics, such as microstructures and phase analysis, were measured using FESEM/EDS and XRD. Coating density, microhardness, and bond strength were examined by water immersion, Vickers indentation, and ASTM C-633 methods, respectively. A ball-on-disk tribometer was employed to conduct wear examination at various temperatures (25, 300, and 600 °C) and loads (10 and 30 N) against the alumina counter body. The wear rate and friction coefficient of SS316L-30%WC-Co decrease from 25 to 600 °C, while the wear rate of SS316L-30%Cr3C2 increases with temperature up to 300 °C and then decreases at 600 °C. The oxide phase adheres strongly to underlying surfaces forming a protective layer (Cr2O3, NiWO4, Fe2O3, and NiMO4), changing the mode of wear mechanism. At higher temperatures and loads, the coating exhibited oxidation modified adhesive wear, and coatings provide excellent wear resistance along with reduction in friction. This research provides a novel approach for future standardization and evaluation of coatings on metal alloys for industrial applications. © ASM International 2024.Item Exploring the microstructural properties of hydroxypropyl-methylcellulose-based solid polymer electrolytes: a promising candidate for flexible electrical double-layer capacitor(John Wiley and Sons Ltd, 2025) Koliyoor, J.; Hegde, S.S.; Ismayil, N.; Badekai Ramachandra, B.R.This study investigates the development and characterization of solid polymer electrolytes based on hydroxypropyl methylcellulose (HPMC) for magnesium ion transport. Electrolyte films were prepared using a conventional solution casting technique, incorporating HPMC and magnesium acetate. Fourier transform infrared (FTIR) spectroscopy and XRD analyses were conducted to examine the interactions between the polymer and salt components. Impedance spectroscopy was employed to assess the electrical conductivity of the prepared electrolytes. Thermal stability was evaluated using TGA. The FTIR and XRD results indicated the formation of a complex between the polymer and salt. The electrolyte containing 30 wt% magnesium acetate exhibited a room temperature ionic conductivity of 5.88 × 10?4 S cm?1, demonstrating enhanced electrical properties. An electrical double-layer capacitor was fabricated using this high-conductivity electrolyte, and its electrochemical performance was analysed. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.