Faculty Publications
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Item Heat transfer distribution of impinging flame and air jets - A comparative study(Elsevier Ltd, 2016) Kadam, A.R.; Tajik, A.R.; Hindasageri, V.Heat transfer distribution of impinging flame jet is compared with that of the impinging air jet based on the experimental data reported in literature for methane-air flame jet and air jet impingement for Reynolds number, R=600-1400 and the non-dimensional nozzle tip to impingement plate distance, Z/d=2-6. The comparative data based on mapping experimental data reported in literature suggest that there is a good agreement between the Nusselt numbers for higher Z/d near stagnation region. However, away from the stagnation region, the Nusselt number for flame jet is higher than that of air jet for similar operating conditions of Re and Z/d. A CFD simulation for impinging air jet and impinging flame jet is carried out to explain the physics and reason for the deviations observed in experimental data. A scale analysis is carried out to identify the dominant forces and their influence on the heat transfer distribution on the impingement plate. © 2015 Elsevier Ltd. All rights reserved.Item Analytical solution to transient inverse heat conduction problem using Green’s function(Springer Science and Business Media B.V., 2020) Parida, R.K.; Madav, V.; Hindasageri, V.A transient inverse heat conduction problem concerning jet impingement heat transfer has been solved analytically in this paper. Experimentally obtained transient temperature history at the non-impinging face, assumed to be the exposed surface in real practice, is the only input data. Aim of this study is to estimate two unknown thermo-physical parameters—overall heat transfer coefficient and adiabatic wall temperature—at the impinging face simultaneously. The approach of Green’s Function to accommodate both the transient convective boundary conditions and transient radiation heat loss is used to derive the forward model, which is purely an analytical method. Levenberg–Marquardt algorithm, a basic approach to optimisation, is used as a solution procedure to the inverse problem. An in-house computer code using MATLAB (version R2014a) is used for analysis. The method is applied for a case of a methane–air flame impinging on one face of a flat 3-mm-thick stainless steel plate, keeping Reynolds number of the gas mixture 1000 and dimensionless burner tip to impinging plate distance equals to 4, while maintaining the equivalence ratio one. Inclusion of both radiation and convection losses in the Green’s function solution for the forward problem enhances the accuracy in the forward model, thereby increasing the possibility of estimating the parameters with better accuracy. The results are found to be in good agreement with the literature. This methodology is independent of flow and heating conditions, and can be applied even to high-temperature applications. © 2020, Akadémiai Kiadó, Budapest, Hungary.Item Inverse estimation of heat transfer coefficient and reference temperature in jet impingement(American Society of Mechanical Engineers (ASME), 2020) Kadam, A.R.; Hindasageri, V.; Kumar, G.N.Applications of impinging jets are wide-ranging from cooling to heating in industrial as well as domestic field. Most of the reported heat transfer distribution data to and from impinging jets have been found from steady-state measurements. This study utilizes the solution to three-dimensional (3D) inverse heat conduction problem to estimate transient temperatures on the impingement side. Then, the temperature gradient is determined near the impingement wall (×0.01mm inside) with which transient heat flux is estimated on the impingement side. Instead of steady-state values, transient heat flux and corresponding wall temperatures are utilized in a thin foil technique to find out heat transfer coefficient and reference temperature simultaneously. The scope of the present technique is examined through its application to impinging jets with various configurations such as laminar jet, turbulent jet, hot jet, cold jet, and multiple jets. In all cases, estimations are reasonably close. The application of this inverse technique can be extended to any configuration of jet impingement irrespective of geometry of nozzle (circular/rectangular), the orientation of nozzle (orthogonal/inclined), the temperature of a jet (hot/cold), Reynolds numbers (laminar/turbulent), the nozzle-to-plate spacing (any Z/d), and roughness of the plate surface. The effect of plate thickness on the accuracy of the present technique is also studied. Up to 5mm thick plates can be used in impinging jet applications without worrying much on accuracy. The use of the present technique significantly reduces the experimental cost and time since it works on transient data of just a few seconds. © © 2020 by ASME.Item Numerical Investigation of Gasper Air Jet Dynamics in an Aircraft Cabin(Taylor and Francis Ltd., 2023) Srinivasa, V.K.; Kattimani, S.; Reddy C, G.Computational fluid dynamics (CFD) is used to analyze the jet interaction of side-vent and gaspers and their influence on cough jets in aircraft cabins. A control device is designed and proposed to be attached to the existing gasper outlet to widen narrow, high-velocity air jet into a widespread air curtain. It forms a shield around the passenger's face, controlling cough droplets from infected passengers entering the co-passengers breathing zone and pushing the high-velocity cough jet toward the floor. A detailed study on flow distribution with existing gaspers and the newly designed control device is presented. The influence and efficacy of the control device in achieving desired flow spread, droplet spread, and intrusion control into co-passengers breathing zones are evaluated. The simulation showed significant droplets were reaching window and aisle passenger breathing zones in the existing gasper, whereas no droplet was found when the control device was introduced. © 2024 Informa UK Limited, trading as Taylor & Francis Group.Item 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 AuthorsItem 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