Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
4 results
Search Results
Item Evaluation of artificial neural network in data reduction for a natural convection conjugate heat transfer problem in an inverse approach: experiments combined with CFD solutions(Springer, 2020) Kumar, M.K.H.; Vishweshwara, P.S.; Gnanasekaran, N.In this work, natural convection fin experiments are performed with mild steel as the fin and an aluminium plate as base. The dimension of the mild steel fin is 250 mm × 150 mm × 6 mm and the aluminium base plate is 250 mm × 150 mm × 8 mm. A heater is provided on one side of the aluminium base plate and the mild steel fin emerges on the other side of the plate. The heater provides required heat flux to the fin base; several steady-state natural convection experiments are performed for different heat fluxes and corresponding temperature distributions are recorded using thermocouples at different locations of the fin. In addition, a numerical model is developed that contains the dimensions of the fin set-up along with extended domain to capture the information of the fluid. Air is treated as a working fluid that enters the extended domain and absorbs heat from the heated fin. The temperature and the velocity of the fluid in the extended domain are obtained by solving the Navier–Stokes equation. The numerical model is now treated as a forward model that provides the temperature distribution of the fin for a given heat flux. An inverse problem is proposed to determine the heat flux that leads to the temperature distributions during experiments. The temperature distributions of the experiments and forward model are compared to identify the unknown heat flux. In order to reduce computational cost of the inverse problem the forward model is then replaced with artificial neural network (ANN) as data reduction, which is developed using several computational fluid dynamics solutions, and the inverse estimation is accomplished. The results indicate that a quick solution can be obtained using ANN with a limited number of experiments. © 2020, Indian Academy of Sciences.Item Nuances of fluid flow through a vertical channel in the presence of metal foam/solid block – A hydrodynamic analysis using CFD(Elsevier Ltd, 2020) Kotresha, B.; Gnanasekaran, N.A numerical study is presented in this paper to examine the fluid flow in a vertical channel partly filled with porous metallic foams. The physical model comprises of aluminum plate-heater assembly placed in the vertical channel. Heat is carried away by the working fluid air from the plates inside the vertical channel through forced convection. High thermal conductivity metal foams are attached to the heater-plate assembly in order to reduce the temperature of the aluminum plates. Thus, the study pays attention only to the characteristics of fluid flow at different positions of the vertical channel in the presence of metal foams. The present analysis considers the Forchheimer – Extended Darcy equation for the metal foam to predict the fluid flow in conjunction with the local non-thermal equilibrium model for the analysis of heat transfer through the porous metal foams. At first, the methodology applied to the present numerical analysis is validated with the existing results. Upon reaffirming the solution methodology, the results of the metal foam study are then compared with a solid block that replaces the metal foam structure inside the vertical channel. Consequently, as a novel approach, the analysis enables one to arbitrate the tradeoff between the porous metal foam and the solid block for heat transfer augmentation from the plate assembly to the air. © 2020 Elsevier LtdItem Numerical study on maximizing heat transfer and minimizing flow resistance behavior of metal foams owing to their structural properties(Elsevier Masson SAS 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2021) Trilok, T.; Gnanasekaran, N.Despite many research works considering metal foams largely involving heat exchange applications, an overall comprehensive view on the performance of metal foams based on their structural properties is hitherto unaddressed in the literature. In the present work, an air forced convection-laminar flow in a vertical channel is considered in which a heated plate along with metal foam is placed at the center. The plate is subject to constant heat flux condition to assess the performance of aluminum metal foam based on their degree of inclination towards maximizing heat transfer and minimizing flow resistance behavior in a vertical channel corresponding to the combination of structural properties they possess. Heat transfer and flow phenomena pertaining to the metal foam are numerically modeled using Local Thermal Non-Equilibrium (LTNE) and Darcy–Forchheimer flow models, respectively to obtain key thermo-hydrodynamic parameters. Both the independent and the combined effects of foam structural parameters viz., porosity and pore density on Nusselt number and friction factor are discussed justifying the effects of interfacial specific surface area and interfacial heat transfer coefficient of fluid saturated foam samples. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) a multi attribute decision-making technique is applied to solve the multi objective function to determine the performance of metal foams measured on a scale of 0 to 1. Five distinct criteria are studied involving distributed weights of 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25 and 1:0 each representing amplitudes of varying importance given to maximizing heat transfer and minimizing flow resistance characteristics of metal foams. Global performance charts are obtained, featuring performance abilities of metal foam samples covering wide ranges of porosity ranging from 0.8 to 0.97 and pore densities ranging from 5PPI to 45PPI corresponding to a given criteria involving a specific weight distribution scenario. The present work provides performance characteristics of available as well as possible foam samples with an overview idea on the range of structural aspects of foam samples, where the enhanced ability of the foam to perform best in meeting the given criteria is witnessed. © 2020 Elsevier Masson SASItem Thermal resistance of Open-Cell metal foam with thermal interface materials (TIM)(Elsevier Ltd, 2023) Ganesan, P.; Zaib, F.; Zaharinie, T.; Mobedi, M.; Gnanasekaran, N.This study investigated the thermal resistances of sandwich structures consisting of open-type metal foams, base plates/surfaces, and thermal interface materials (TIMs) in two types of sandwiching configurations, namely Type 1 and Type 2. Samples were prepared using metal foam structures of 20, 40, and 60 pores per inch (PPIs), representing five commercial TIMs, i.e., pyrolytic graphite sheet (PGS), T621, SFT90, PC93, and PC94. They were categorised into two types: (i) thin and hard films (PGS, T621, SFT90) and (ii) thick and soft pads (PC93 and PC94). The thermal resistance and the thickness were measured under compression loadings of 0 – 60 N using an in-house thermal resistance tester developed according to the ASTM D5470 standard. Based on the nanoindentation test, PGS showed the highest hardness (0.2660 GPa), followed by T621 (0.0322 GPa), SFT90 (0.0235 GPa), PC93 (0.0007 GPa), and PC94 (0.0004 GPa). In general, thermal resistances were dependent on compression forces; they decreased with increasing compression loads. At a 30 N load for 60 PPI, the thermal resistance of the hard TIM sample was reduced to 62% with a 1.5% reduction in compression thickness at the Type 1 configuration. The resistance decreased as much as 8% when PPIs increased from 20 to 60. By contrast, at a 30 N load for 60 PPI, the thermal resistance of the soft TIM sample was reduced to 58% with a 16% reduction in compression thickness at the Type 1 configuration. When PPIs increased from 20 to 60, the resistance decreased by just 5%. Despite a lower thermal resistance reduction than the hard TIM, the soft TIM was 19% higher in thermal resistance difference. This study showed that joining metal foam, TIM, and base plate reduced thermal resistances while increasing their performance. © 2022 Elsevier Ltd