Faculty Publications

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Scaling and Integral Solutions to Mixed Convection Over an Exponential Stretching Sheet
(International Information and Engineering Technology Association, 2020) Veerabhadrappa, R.M.B.; Ademane, V.; Gumtapure, V.; Hindasageri, V.
The reported studies on mixed convection flow problems have been solved purely by method of similarity studies. Scaling analysis is an alternate method that can give better engineering insight of the problem being investigated. Integral solutions are mathematically simpler to handle as the engineering requirement is that of accurate solutions only close to the wall. In the present work, scaling and integral solutions are discussed for a typical mixed convection flow problem already discussed in literature by similarity technique. Scaling method has been demonstrated and is found in good agreement with the results obtained from similarity method. The integral solution is obtained by deriving the integral form of governing equation and solution is discussed for specific case of Prandtl number = 1. The solution obtained by Integral formulations is in good agreement with that of similarity method.
INFLUENCE OF TWISTED TAPE INSERT ON THE COOLANT FLOW CHARACTERISTICS IN SWIRLED FILM COOLING
(Serbian Society of Heat Transfer Engineers, 2022) Ademane, V.; Kadoli, R.; Hindasageri, V.
The present paper discusses film cooling behavior through numerical simulation in the presence of a twisted tape insert inside the film hole. The twisted tape insert imparts a swirl to the coolant flow. Coolant swirl intensity is controlled by varying the pitch of the twisted tape resulting in swirl numbers of 0.0289, 0.116, and 0.168. The film cooling performance is evaluated using area-averaged effectiveness and heat transfer coefficient for blowing ratios of 0.5, 1.0, 1.5, and 2.0. Results revealed a significant amount of improvement in averaged effectiveness with the addition of swirl. Coolant swirl predominantly modifies the jet trajectory resulting in a reduced jet penetration and increased lateral expansion. Further investigation on the effect of twisted tape thickness on the coolant distribution has been found to be negligible. Pressure losses occurring due to the insertion of twisted tape inside the film hole is evaluated through the coefficient of discharge which indicated the necessity of higher pumping power than the film cooling case with no-swirl. © 2022. Society of Thermal Engineers of Serbia. All Rights Reserved.
Simultaneous estimation of reference temperature and heat transfer coefficient in transient film cooling problems
(Yildiz Technical University, 2023) Ademane, V.; Kadoli, R.; Hindasageri, V.
This paper aims to simultaneously estimate the reference temperature and heat transfer coefficient in film cooling situations from transient temperature measurements. The existing steady-state technique is a tedious process and employs distinct boundary conditions to evaluate each parameters of the film cooling. Applying different boundary conditions may lead to errors in the estimated parameters due to differences in aerodynamic conditions. On the other hand, a transient technique can estimate both parameters in a single test by utilizing short-duration transient temperature data. Hence, the present study uses a novel approach for solving transient film cooling problems based on the inverse heat conduction approach, which can simultaneously estimate heat transfer coefficient and reference temperature. The present method employs an optimization technique known as the Levenberg-Marquardt Algorithm. The objective function for the inverse algorithm is constructed using the analytical solution of a transient one-dimensional semi-infinite body. The transient surface temperature data required for the present analysis is obtained through a numerical simulation of film cooling arrangement over a flat surface. Laterally averaged effectiveness and heat transfer coefficient for blowing ratios of 0.5, 0.8, and 1.0 are analyzed using the present technique and compared against the steady-state simulation results to demonstrate the methodology. An average deviation of around 7% for the estimated effectiveness and 4% for the heat transfer coefficient values are observed between the present IHCP method and the steady state simulation results. The deviation in heat transfer coefficient predominately occurred near the film hole exit of x/d < 5, which might have occurred due to the conjugate solution employed in the present work. © 2021, Yıldız Technical University. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).
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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