Faculty Publications

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Author: search.filters.author.Madav, V.

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    Application of green’s function to establish a technique in predicting jet impingement convective heat transfer rate from transient temperature measurements
    (Pleiades journals, 2019) Parida, R.K.; Kadam, A.R.; Hindasageri, V.; Madav, V.
    Jet impingement heat transfer has gained attention of the researchers due to its very high rate of convective heat transfer. The objective of this study is to establish an analytical technique to predict the convective heat transfer coefficient and the reference temperature over a surface being impinged. This technique is based on the fundamental mathematical concept of Green’s function. A code in MATLAB is developed to predict both local convective heat transfer coefficient and reference temperature over the impinging surface, which requires the transient temperature data at both faces of the impinging plate as input. Radiation correction is also considered to incorporate radiation losses in high-temperature applications. This code works on the principle of one-dimensional heat transfer across the impinging plate, for known dimensions, thermal diffusivity, and surface emissivity. A numerical simulation of hot jet at Reynolds number equal to 1000, over a cold plate of thickness 10 mm, is carried out for a given set of spatially varying convective heat transfer coefficient and reference temperature values, along the impinging surface. The impinging plate is considered to be orthotropic to ensure one-dimensional heat conduction across the plate thickness. Transient temperature at both the faces for a duration of 10 s with an interval of one second was recorded and used as input to the code to validate the proposed technique. Local heat transfer coefficient and the reference temperature predicted are in good agreement with those input values for numerical analysis using ANSYS, having a maximum deviation of 2 and 10%, respectively. Further, it is observed that estimated values of convective heat flux at a given location on the impinging surface varies linearly with temperature at the same location, which confirms Newton’s law of cooling. © Springer Nature Singapore Pte Ltd. 2019.
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    Investigation on Tire Pyrolysis Oil (Tpo) as a Fuel for Cook Stove and Lamps
    (Institute of Physics Publishing helen.craven@iop.org, 2018) Mohan, A.; Prajeeth Kumar, K.P.; Madav, V.
    Pyrolysis is an technology to derive value added products like pyrolytic oil, steel wire and carbon black, which works on the principle of thermo-chemical conversion of any carbonaceous feed stocks. The major factors affecting the pyrolysis are temperature, reactor configurations, residence time, heating source etc. A pilot plant study was conducted in a tire pyrolysis oil production industry located in Oyalapathy, Kerala for collecting the oil samples for the analysis. Tire pyrolysis oil (TPO) is a brownish colored, freely flowing liquid, medium viscosity with complex chemical composition. Due to its complex aromatic structure, presence of acids, aldehydes, oxygenated compounds hinders to apply in engine and stove as a fuel. Upgrading of hydrocarbons are necessary to obtain value added products and to derive thermally stable products. There are limited number of studies are carried out in the field of stove fuel production from hydrocarbon derived waste. An attempt was carried out to find the suitability of pyrolysis oil as a fuel in cook stove and oil lamps. The water boiling test was carried out to examine the boiling time for specific volume of water. The study shows that the TPO boils water in shorter time than kerosene and a clear comparison of two brand of fuels. The present study mainly includes the characterization like FTIR, GC-MS to investigate the components present in the oil and compare with diesel and kerosene. The commercialization and economic feasibility studies will be planned in future. © Published under licence by IOP Publishing Ltd.
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    Co-pyrolysis of scrap tire and plastic using coal derived fly-ash
    (ETA-Florence Renewable Energies, 2019) Mohan, A.; Dutta, S.; Madav, V.; Bhushnoor, S.S.; Fernandez-Garcia, J.F.; Williams, P.T.
    Used automobile tires and thermoplastics (e.g. polypropylene) have become liability of modern societies and several avenues have been explored for their suitable disposal. Pyrolytic liquefaction of tires and plastics have attracted significant attention since the process can provide value-added products such as liquid transportation fuels and chemicals while mitigating the waste disposal issues. Pyrolysis can be done both in absence (thermal) or presence (catalytic) of a catalyst. Catalytic pyrolysis is favored by less demanding reaction conditions and better quality of product. Catalytic copyrolysis has the additional advantage in using a wider feedstock and a possible synergistic effects from different feeds during molecular transformations. This work investigates the effect of untreated fly-ash (class F) as catalyst for the copyrolysis of scrap tire and polypropylene at 300o C and atmospheric pressure using batch type pyrolysis reactor and also studied the effect of fly-ash during pyrolysis of scrap tire using Pyro-GC/MS. Copyrolysis was carried out using various ratio of scrap tire and polypropylene at 300o C, whereas the pyrolysis of scrap tire in pyro-GC/MS was carried out at 500o C. The maximum yield (23.33%) of oil was obtained at a ratio of 60:40 (w/w) of scrap tire and polypropylene in presence of 20wt% of fly ash catalyst. The oils were characterized by NMR, GC-MS, FT-IR and elemental analysis. © 2019 ETA-Florence Renewable Energies.
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    Modeling and design validation of fluidized bed reactors for co-gasification of coal and biomass to study hydrodynamics and conversion
    (ETA-Florence Renewable Energies, 2019) Manu, J.; Dev, R.; Madav, V.
    The gasifier was designed with reaction chamber of 65mm diameter and 500 mm height. The study of gas-solid hydrodynamics is essential in designing of fluidized bed gasifier. Drag force plays a critical role in modeling fluidization behavior for gas-solid flow. This paper aims to study the effect of drag force on the fluidization parameter for the presently designed gasifier using CFD approach. The Eulerian-Eulerian model, coupled with different drag models was employed for this purpose. Time-averaged solid volume fraction, granular temperature, axial velocity of the solid particle in a lateral direction, and a central axis of the reactor were examined for different drag models like Syamlal O’Brien, Gidaspow, Mckeen and Representative unit cell. Effects of laminar and turbulent models on flow behavior were also studied. The study concluded that the McKeen model shows a relatively flat profile while estimating solid volume fraction while the RUC model overestimated the axial velocity of particles. There was relatively no change in flow behavior for the laminar and turbulent model while predicting the axial velocity of the solid particle in the lateral direction. The axial velocity of particles at a different packing factor was studied and showed no such observable difference in predicting hydrodynamics flow behavior. © 2019 ETA-Florence Renewable Energies.
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    Hydrodynamic effect of elastic and inelastic collisions in fluidized bubbling bed reactor
    (American Institute of Physics Inc. subs@aip.org, 2020) Manu, J.; Madav, V.
    Collison of sand particles in fluidized bed plays a very important role in determining hydrodynamics of fluidized bed. Effect of coefficient of restitution on hydrodynamics on 300?μm particles in gas-solid fluidized bed was investigated. Eulerian-Eulerian model was used for simulating hydrodynamics of fluidized bed. For investigation, different values of coefficient of restitution which correspond to different values of elasticity of particles were used. No bubbles were found for perfectly elastic collisions. With decrease in the value of coefficient of restitution from 1 to 0.8, bubble formation shows a positive effect. © 2020 Author(s).
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    High temperature corrosion behaviour of stainless steels and Inconel 625 in hydroxide salt
    (Elsevier Ltd, 2021) Pooja, M.; Ravishankar, K.S.; Madav, V.
    Biomass gasification had proven to be an alternative source of energy to coal gasification. However, it requires high temperatures of about 1000°C for biomass drying and reduction. On the other hand, to reduce the oxidation and corrosion of gasifier structural materials it is important to keep the gasifier working temperature as low as possible. One effective way of keeping the reduction temperature low is to use molten salts as catalyst during biomass gasification. However, by virtue, molten salts cause several corrosion issues in ferrous alloys. In this context, the present study investigates the effect of hydroxide molten salt on the corrosion behaviour of stainless steels such as 316 and 310 and Inconel 625. The samples exposed to the salt at 700°C for about 48 h was analysed for corrosion using weight loss method. A scanning electron microscopy analysis of the exposed samples revealed the depth of corrosion and change in microstructure due to molten salt attack. Although all the selected materials suffered severe corrosion, among all, Inconel 625 show higher corrosion resistance. © 2021 Elsevier Ltd. All rights reserved.
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    Capture and Characterization of Particulates from a Single-Cylinder Diesel Engine Fuelled with Refined Tire Pyrolysis Oil
    (Springer Science and Business Media Deutschland GmbH, 2023) Mohan, A.; Madav, V.
    Crude tire pyrolysis oil (CTPO) was refined using the principle of selective adsorption and preferential solubility using silica gel as an adsorbent and petroleum ether as a diluent and combusted in a single-cylinder diesel engine. Particulate analysis was conducted in a single-cylinder diesel engine to understand the carbonaceous deposition in piston crowns and surfaces using various analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Further, lubricating oil analysis was performed using a combination of ICP-AES, viscosity, flash, and fire point tests. The results showed that carbon deposition from upgraded tire pyrolysis oil is observed to be higher than diesel due to its high aromatic content. The high amount of carbon deposits from upgraded tire pyrolysis oil was attributed to the high amount of oxygenates in StTPO, which leads to increased polymerization and subsequent condensation on piston crown surfaces, which was then carbonized. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    The experimental analysis of heat transfer characteristics of a hot surface impinged by a lateral air jet
    (American Institute of Physics, 2025) Kumar, C.; Madav, V.
    This experimental investigation explores the heat transfer dynamics caused by lateral air jet impingement on a hot, thin stainless steel foil. The aim is to understand the heat transfer characteristics of air jet impinging laterally on the top surface. This setup is relevant to industrial cooling applications where space is limited. Using a thermal imaging camera, the study captures the steady-state temperature distribution across the foil surface. The experiment was conducted by varying the jet exit to stagnation point-to-diameter (S/d) ratios for the lateral jet (2 to 20). The study was carried out for Reynolds number 3000. Keeping electronic chip temperatures below a critical threshold is crucial, as excessive heat can cause performance issues, chip damage, and even pose safety risks in extreme cases. To address the substantial cooling needs of heat-generating chips, a variety of methods and technologies have been explored, including heat pipes, pool boiling, microchannel heat sinks, spray cooling, and jet impingement, among others. The findings show that the lateral jets is good choice for electronic cooling applications when the localized cooling is necessary, and by keeping specific S/d value wider area cooling can also be achieved. It is observed that at S/d=8 maximum Nu is achieved and as S/d is increased further cooling area coverage is widening even though the maximum Nu achieved is comparatively less. This study offers valuable insights into optimizing air jet impingement techniques for enhanced thermal management in various technological domains. © 2025 Author(s).
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    Sustainable Nanoplasmon-Enhanced Photoredox Reactions: Synthesis, Characterization, and Applications
    (Wiley-VCH Verlag info@wiley-vch.de, 2020) Bhattacharya, C.; Saji, S.E.; Mohan, A.; Madav, V.; Jia, G.; Yin, Z.
    Plasmonic materials with their unique properties, such as light-excitable resonant oscillation of conduction electrons, strong local electric field, and energetic hot charges (electrons/holes) etc., have overcome the limitations of traditional photoredox catalysts. They are especially important due to their superior light focusing ability, from free-space wavelengths to the sub-wavelength range. Although noble metal plasmonic enhancement has been recognized as one of the most important strategies in photocatalysis, the high cost and limited spectral range absorption of noble metals remain the biggest challenges for their practical application, which has led to a gradual shift in the focus on the abundant and less expensive non-noble metal plasmonics. Recently, various non-noble plasmonic materials such as non-noble metals (Cu, Al, Ni and Bi), metal oxides and chalcogenides (WO3-x, MoO3-x, NiO, MNbO3, where M = Ca, Sr or Ba; Fe2O3, SrTiO3, In2O3, Cu2-xS and Bi2Se3), nitrides (TiN, ZrN, HfN and WN) have emerged as efficient photocatalysts. Herein, the door to the relatively new and exciting world of noble metal-free plasmonic materials and their promising applicability in solar-energy driven photo-redox catalysis such as water splitting, CO2 reduction, nitrogen reduction, organic transformations and environment remediation is opened. Their synthesis methods and a plethora of characterization techniques are also systematically exhibited. © 2020 Wiley-VCH GmbH
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    Directional synthesis of aviation-, diesel-, and gasoline range hydrocarbon fuels by catalytic transformations of biomass components: An overview
    (Elsevier Ltd, 2023) Dutta, S.; Madav, V.; Joshi, G.; Naik, N.; Kumar, S.
    Selective conversion of heavily oxygenated biomolecules into hydrocarbon-based liquid transportation fuels with stipulated structural traits is of academic and industrial significance. This work provides an overview of producing fuel precursors from biomass components and their catalytic transformation into aviation-, diesel-, and gasoline-range hydrocarbon fuels (HCFs). Strategic applications of various organic transformations for the molecular design of targeted products have been rationalized. Construction and alteration of the carbon skeletal system in the fuel candidates via chemical-catalytic transformations have been highlighted. Emphasis has also been given to the process conditions and details of the catalysts employed in these processes. Critical analysis of the literature data presented in this review will assist the researchers in developing more proficient processes for the biorenewable production of drop-in HCFs. © 2023 Elsevier Ltd