Faculty Publications

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Author: search.filters.author.Kumar, C.

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    Sub-pixel mineral mapping using EO-1 hyperion hyperspectral data
    (International Society for Photogrammetry and Remote Sensing, 2014) Kumar, C.; Shetty, A.; Raval, S.; Champatiray, P.K.; Sharma, R.
    This study describes the utility of Earth Observation (EO)-1 Hyperion data for sub-pixel mineral investigation using Mixture Tuned Target Constrained Interference Minimized Filter (MTTCIMF) algorithm in hostile mountainous terrain of Rajsamand district of Rajasthan, which hosts economic mineralization such as lead, zinc, and copper etc. The study encompasses pre-processing, data reduction, Pixel Purity Index (PPI) and endmember extraction from reflectance image of surface minerals such as illite, montmorillonite, phlogopite, dolomite and chlorite. These endmembers were then assessed with USGS mineral spectral library and lab spectra of rock samples collected from field for spectral inspection. Subsequently, MTTCIMF algorithm was implemented on processed image to obtain mineral distribution map of each detected mineral. A virtual verification method has been adopted to evaluate the classified image, which uses directly image information to evaluate the result and confirm the overall accuracy and kappa coefficient of 68% and 0.6 respectively. The sub-pixel level mineral information with reasonable accuracy could be a valuable guide to geological and exploration community for expensive ground and/or lab experiments to discover economic deposits. Thus, the study demonstrates the feasibility of Hyperion data for sub-pixel mineral mapping using MTTCIMF algorithm with cost and time effective approach.
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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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    Identification and characterization of hydrothermally altered minerals using surface and space-based reflectance spectroscopy, in parts of south-eastern Rajasthan, India
    (Springer Nature, 2020) Chattoraj, S.L.; Sharma, R.U.; Kumar, C.; Champati Ray, P.K.; Sengar, V.
    Imaging spectroscopy has evolved as one of the most significant advancements due to contiguous spectral coverage and higher spectral resolution which enable mineral identification and mineral exploration. Many phyllosilicate and carbonate minerals show specific spectral absorption feature in the wavelength range of visible-to-near-infra-red region of electromagnetic spectrum. These spectral features enable delineation of different mineral assemblages which in turn help in mineral prospecting using hyperspectral imaging spectra. The present study is focussed on evaluation and application of EO-1 Hyperion (hyperspectral) data as an Earth Observation tool for mineral detection and mapping in parts of Udaipur district in south-eastern Rajasthan. Hyperion reflectance imagery of this area was analysed using spectral angle mapper after pre-processing, atmospheric correction and geometric correction. Five endmembers, viz. dolomite, montmorillonite, chlorite, phlogopite and serpentine, were derived from both atmospherically corrected image and from rock samples in the laboratory using ASD field spectroradiometer covering spectral range of 0.4–2.5 µm. The reflectance spectra of endmembers derived from satellite image were initially compared with USGS mineral spectral library, and then after comparing with laboratory-based spectra with respect to absorption features, target minerals were identified which shows more than 70% match with the USGS and laboratory spectra. These minerals were also cross-checked with the reported litho-sequence of the area. Minerals derived from laboratory and image spectra are indicative of hydrothermally altered outer thermal aureole which is also corroborated by litho-structural association of the area. © 2020, Springer Nature Switzerland AG.
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    Experimental study of convective heat transfer distribution of non-interacting wall and perpendicular air jet impingement cooling on flat surface
    (Elsevier Ltd, 2024) Kumar, C.; Ademane, V.; Madav, V.
    An experimental study evaluated heat transfer with perpendicular and wall-impinging air jets on stainless steel foil, for Reynolds numbers Re = 3000, 5000, 8000, and 10000, where the perpendicular jet targets the bottom and the wall jet the top, creating a unique, non-interacting effect. Distances to nozzle diameter ratios for wall jets (S/d = 4, 6, 8, 10) and perpendicular jets (Z/d = 2, 4, 6, 8) were varied. Significant heat transfer increases were noted, with the Nusselt number rising by up to 49.20 % for a Z/d = 6 and S/d = 8 combination at Re = 5000. Improvements ranged from 10.03 % to 49.20 %, peaking when the jets' high heat transfer regions overlapped. Optimal performance for Re = 3000 was at S/d = 10, aligning the wall jet's maximum with the perpendicular jet's stagnation area. For Re = 5000 to 10000, optimal S/d values were 8 and 4 for Z/d = 6, 8 and Z/d = 2, 4, respectively. The Nusselt number increase ranged from 29.21 % to 46.57 % at S/d = 10 for Re = 3000, the highest among all tested values. Wall jet heat transfer downstream increased by 90–105 % over perpendicular jets in corresponding regions. Increasing the wall to perpendicular jet distance improved heat transfer near the stagnation point, suggesting this cooling method for high-density electronics like CPUs and GPUs. © 2024 The Authors
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    Performance assessment of solar PV panels under varying environmental conditions: a laboratory and field-based approach for sustainable energy in mining operations
    (Springer, 2025) Tripathi, A.K.; Mangalpady, M.; Sharma, S.; Kumar, C.; Didwania, M.
    This study provides a novel and comprehensive assessment of solar photovoltaic (PV) panel performance under varying environmental conditions, integrating laboratory experiments with real-world field studies to address challenges specific to mining operations. The research uniquely explores the combined effects of shading, temperature, humidity, dust deposition, and tilt angle, delivering actionable insights for optimizing PV systems in harsh conditions. Laboratory experiments demonstrated that a parallel configuration significantly minimizes power losses under partial shading, while a rise in temperature from 35 to 75 °C resulted in a notable 21.34% and 29.12% power output reduction for monocrystalline and polycrystalline panels, respectively. Furthermore, increased humidity (65.40 to 98.20%) caused a 35.82% decline in power output due to scattering effects. Field studies conducted in a surface mining environment revealed that dust accumulation led to a substantial 43.18% drop in maximum power output after 5 days, emphasizing the importance of regular cleaning. Optimal energy capture was achieved at a 15° tilt angle, aligning with the site’s latitude. These findings underscore the novelty of using combined experimental approaches and field validation to improve PV performance in mining operations. Practical recommendations, including parallel configurations to mitigate shading losses, temperature regulation strategies, and frequent cleaning protocols, are proposed to enhance the sustainability and efficiency of renewable energy systems in challenging environments. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
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    Analysis of heat transfer characteristics of a coaxial air jet on a hot surface: An experimental study with circular nozzles of different arrangements
    (Elsevier B.V., 2025) Kumar, C.; Madav, V.
    Coaxial jets are widely utilized in various engineering applications where highly localized heat transfer is the requirement, including combustion systems, cooling technologies, propulsion systems, material processing, and environmental control. This study investigates the effects of air jet impinging on a hot surface by varying the nozzle-to-plate distance-to-diameter ratio (Z/d) at values of 2, 4, 6, and 8, along with adjustments in the inner-to-outer jet exit distance ratio (H/d), set at -1, 0, and +1, under different Reynolds numbers (Re) of 5000, 10000, 15000, and 20000. The study provides a comparative analysis of Nusselt number achieved by coaxial jet configurations against conventional circular single-jet impingement, highlighting significant improvements in heat transfer rate The findings demonstrate that coaxial jets markedly enhance heat transfer, particularly at the stagnation point of the foil surface, with the H/d = +1 configuration yielding the best result. An improvement of 191 % is observed for Z/d = 6 and H/d = +1 case when Re is increased from 5000 to 20000, Proving the impact of increase in Re on stagnation Nusselt Number. When stagnation Nusselt number is compared for normal circular jet with that of H/d = +1 case in coaxial jet, a maximum of 88.73 % improvement is seen. This study is important because the results offer valuable insights for optimizing air jet impingement techniques to improve thermal management across a range of industrial applications ranging from Gas turbines to manufacturing industries where localized cooling is the major requirement. The correlations to calculate the stagnation Nusselt number for three configurations of the coaxial jet are developed. © 2025