Browsing by Author "Kotresha, B."

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A Parametric Study on Mixed Convection in a Vertical Channel in the Presence of Wire Mesh
(Taylor and Francis Ltd., 2021) Kotresha, B.; Gnanasekaran, N.
A numerical study on mixed convection is carried out through a partially filled brass wire mesh in a vertical channel. A heater embedded with aluminum plates is placed at the center of the vertical channel. The aluminum heater assembly is wrapped with brass wire mesh to facilitate more heat transfer. The vertical channel that consists of aluminum heater assembly with the brass wire mesh is considered as the numerical model. Local thermal non-equilibrium and Darcy extended Forchheimer models are used to accomplish the numerical simulations for thermal and flow characteristics of the considered domain. The aim of the study is to find out the optimum filling of the brass wire mesh in the channel which gives a higher heat transfer rate with low pumping power of the fluid. In the present analysis, three different filling conditions of wire mesh are considered: (i) fully filled channel, (ii) 70% filled channel, and (iii) 40% filled channel. From the results, it is inferred that the vertical channel partially filled with 70% of wire mesh porous medium predicts 89% of heat transfer of the completely filled channel with 41% reduced pressure loss. As a result, the proposed parametric study is good enough to prove that the partly filled wire mesh can be used in the thermal applications where augmentation of heat transfer is required with less pressure drop. © 2020 Taylor & Francis Group, LLC.
A Synergistic Combination of Thermal Models for Optimal Temperature Distribution of Discrete Sources Through Metal Foams in a Vertical Channel
(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2019) Kotresha, B.; Gnanasekaran, N.
This paper discusses about the numerical prediction of forced convection heat transfer through high-porosity metal foams with discrete heat sources in a vertical channel. The physical geometry consists of a discrete heat source assembly placed at the center of the channel along with high thermal conductivity porous metal foams in order to enhance the heat transfer. The novelty of the present work is the use of combination of local thermal equilibrium (LTE) model and local thermal nonequilibrium (LTNE) model for the metal foam region to investigate the temperature distribution of the heat sources and to obtain an optimal heat distribution so as to achieve isothermal condition. Aluminum and copper metal foams of 10 PPI having a thickness of 20 mm are considered for the numerical simulations. The metal foam region is considered as homogeneous porous media and numerically modeled using Darcy Extended Forchheimer model. The proposed methodology is validated using the experimental results available in literature. The results of the present numerical solution indicate that the excess temperature of the bottom heat source reduces by 100 °C with the use of aluminum metal foam. The overall temperature of the vertical channel reduces based on the combination of LTE and LTNE models compared to only LTNE model. The results of excess temperature for both the empty and the metal foam filled vertical channels are presented in this work. © 2019 by ASME.
Analysis of forced convection heat transfer through graded PPI metal foams
(Pleiades journals, 2019) Kotresha, B.; Gnanasekaran, N.
A forced convection heat transfer through high porosity graded Pores per inch (PPI) metal foam heat exchanger is numerically solved in this paper. The physical domain of the problem consists of a heat exchanger system attached to the bottom of a horizontal channel to absorb heat from the exhaust gas leaving the system. Two different pore densities of the metal foam 20 and 40 along with two different metal foam materials are considered for the enhancement of heat transfer in the present numerical investigation. The metal foam heat exchanger is considered as a homogeneous porous medium and is modeled using Darcy Extended Forchheirmer model. The heat transfer through the metal foam porous media is solved by using local thermal equilibrium (LTE) model. The effect of graded pore density and graded thermal conductivity is investigated and compared with the nongraded PPI metal foam. The heat exchanger system is simulated over a velocity range of 6–30 m/s. The pressure drop decreases for the graded pore density metal foams compared to the higher PPI metal foam and also increases with increase in the fluid inlet velocity. The results of temperature and velocity distribution for the graded and nongraded metal foams are compared and discussed elaborately. © Springer Nature Singapore Pte Ltd. 2019.
Asymptotic approach to obtain nusselt number correlation for laminar mixed convection in a vertical channel
(2018) Nakate, P.; Kotresha, B.; Gnanasekaran, N.
In this paper, a general methodology is proposed for treating mixed convection problems in a vertical channel by the concept of asymptotic computational fluid dynamics (ACFD). Average Nusselt number is developed based on the limiting solutions of natural and forced convection.These correlations are then blended to find a unified composite correlation that work very well for extreme limits of mixed convection. For the purpose of demonstration, the problem of 2-D laminar, mixed convection in a vertical channel that comprises of a heater sandwiched between two aluminum plates has been used. Numerical simulations are performed with ANSYS-FLUENT to generate the required correlation. The study proposed in this work reveals that with minimum CFD solutions one can obtain a reasonably good composite correlation for the Nusselt number. � 2018 by the authors of the abstracts.
Asymptotic approach to obtain nusselt number correlation for laminar mixed convection in a vertical channel
(Dalian University of Technology, 2018) Nakate, P.; Kotresha, B.; Gnanasekaran, N.
In this paper, a general methodology is proposed for treating mixed convection problems in a vertical channel by the concept of asymptotic computational fluid dynamics (ACFD). Average Nusselt number is developed based on the limiting solutions of natural and forced convection.These correlations are then blended to find a unified composite correlation that work very well for extreme limits of mixed convection. For the purpose of demonstration, the problem of 2-D laminar, mixed convection in a vertical channel that comprises of a heater sandwiched between two aluminum plates has been used. Numerical simulations are performed with ANSYS-FLUENT to generate the required correlation. The study proposed in this work reveals that with minimum CFD solutions one can obtain a reasonably good composite correlation for the Nusselt number. Â© 2018 by the authors of the abstracts.
Comparison of fluid flow and heat transfer through metal foams and wire mesh by using CFD
(Bentham Science Publishers, 2019) Kotresha, B.; Gnanasekaran, N.
Background: The unique structural characteristics of the metal foams, such as low density, large surface area, ability to increase turbulence, and increased heat transfer efficiency, are the advantages associated with thermal applications such as electronics cooling, refrigeration air conditioning, etc. The porous metal foam structures are extensively used to enhance heat transfer. Objective: This paper discusses the numerical simulations of a vertical channel filled with metal foam and wire mesh. The fluid flow and heat transfer phenomena of a wire mesh are compared with two different types of metal foams. Metal foams are made of aluminium and copper while the wire mesh is made of brass. The porosity of the metallic porous structures varies from 0.85 to 0.95. Methods: A Darcy extended Forchheirmer model is considered for solving fluid flow through the porous media while the heat transfer through the porous media is predicted using local thermal non-equilibrium model. Results: Initially, the results obtained using the proposed numerical procedures are compared with experimental results available in the literature. The numerical simulations suggest that the pressure drop increases as the velocity of the fluid increases and decreases as the porosity increases. The heat transfer coefficient and Nusselt number are determined for both the metal foams and the wire mesh. Conclusion: The Nusselt number obtained for wire mesh shows almost 90% of the copper metal foam in the same porosity range. The numerical results suggest that the brass wire mesh porous medium can also be used for enhancement of heat transfer. In this article, patents have been discussed. © 2019 Bentham Science Publishers.
Determination of interfacial heat transfer coefficient for the flow assisted mixed convection through brass wire mesh
(Elsevier Masson SAS 62 rue Camille Desmoulins Issy les Moulineaux Cedex 92442, 2019) Kotresha, B.; Gnanasekaran, N.
In this work, a numerical investigation of Darcy?Forchheimer mixed convection from a heated vertical flat plate embedded in a brass wire mesh porous medium is carried out to determine the coupled effects of flow and thermal diffusion. The numerical model consists of a two dimensional computational domain in which conjugate heat transfer analysis is performed to predict the hydrodynamic and thermal performance of the brass wire mesh in a vertical channel using Local Thermal Non-Equillibrium (LTNE) model. The novelty of the present study is to acquire the interfacial heat transfer coefficient, an as yet another challenging task, of the wire mesh porous medium so as to provide a quick and feasible solution to modeling of fluid flow and heat transfer through brass wire mesh porous media. The results of heat transfer through brass wire mesh are reported in terms of Colburn j factor, performance factor and are compared with other porous mediums available in literature. The present study not only opens up new vistas for more parametric studies but also provides practical and cost effective assessment to design new porous materials. © 2018 Elsevier Masson SAS
Effect of thickness and thermal conductivity of metal foams filled in a vertical channel – a numerical study
(Emerald Publishing, 2019) Kotresha, B.; Gnanasekaran, N.
Purpose: This paper aims to discuss about the two-dimensional numerical simulations of fluid flow and heat transfer through high thermal conductivity metal foams filled in a vertical channel using the commercial software ANSYS FLUENT. Design/methodology/approach: The Darcy Extended Forchheirmer model is considered for the metal foam region to evaluate the flow characteristics and the local thermal non-equilibrium heat transfer model is considered for the heat transfer analysis; thus the resulting problem becomes conjugate heat transfer. Findings: Results obtained based on the present simulations are validated with the experimental results available in literature and the agreement was found to be good. Parametric studies reveal that the Nusselt number increases in the presence of porous medium with increasing thickness but the effect because of the change in thermal conductivity was found to be insignificant. The results of heat transfer for the metal foams filled in the vertical channel are compared with the clear channel in terms of Colburn j factor and performance factor. Practical implications: This paper serves as the current relevance in electronic cooling so as to open up more parametric and optimization studies to develop new class of materials for the enhancement of heat transfer. Originality/value: The novelty of the present study is to quantify the effect of metal foam thermal conductivity and thickness on the performance of heat transfer and hydrodynamics of the vertical channel for an inlet velocity range of 0.03-3 m/s. © 2018, Emerald Publishing Limited.
Forced Convection Analysis in a Horizontal Pipe in the Presence of Aluminium Metal Foamâ€”A Numerical Study
(Springer Science and Business Media Deutschland GmbH, 2021) Jadhav, P.H.; Kotresha, B.; Gnanasekaran, N.; Arumuga Perumal, D.
Numerical exploration of forced convective heat transfer through the aluminium metallic foam filled in a horizontal pipe is done expending a commercially existing software ANSYS FLUENT 15.0. The motive of the ongoing numerical examination is to investigate the effect of fully filled metal foam in a horizontal pipe for different flow regimes. 10 PPI metal foam having 0.85 porosity is filled 60% along the length of pipe in the flow direction. The Darcy-extended Forchheimer (DEF) flow and local thermal non-equilibrium (LTNE) models are considered at the metal foam region to envisage fluid flow and augment in heat transfer. The numerical methodology is validated by comparing the results with available experimental data. The results of pressure loss, variation of wall temperature and Nusselt number are reported and discussed. Â© 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Forced convection through discrete heat sources and simple thermal model - A numerical study
(International Journal of Mathematical, Engineering and Management Sciences, 2019) Hasavimath, K.; Naik, K.; Kotresha, B.; Gnanasekaran, N.
In this work a forced convection through discrete heat sources and simple thermal model placed inside the vertical channel is analyzed numerically. The problem considered for the investigation comprises of a vertical channel with distinct heat source assembly located at the center of the channel. The novelty of the present work is to replace the discrete heat source assembly by a simple thermal model to obtain uniformly distributed temperature and streamlines. A conjugate heat transfer investigation is carried out because the problem domain consists of aluminum solid strips as well as Bakelite strips in discrete heat source assembly which are replaced by a aluminum solid in case of simple thermal model. The numerically obtained data are initially compared with experimental data for the purpose of validation. The temperature of each discrete sources decrease with increase in inlet velocity of the fluid and bottom heat source is able to take higher heat load. The results in terms excess temperature obtained for both discrete heat source and simple thermal model is presented and discussed. © International Journal of Mathematical, Engineering and Management Sciences.
Inexpensive computations using computational fluid dynamics combined with asymptotics applied to laminar mixed convection in a vertical channel
(American Society of Mechanical Engineers (ASME), 2019) Nakate, P.; Kotresha, B.; Gnanasekaran, N.
In this work, a solution technique is proposed by synergistically combining asymptotics and computational fluid dynamics to ascertain a problem of laminar mixed convection heat transfer in a vertical channel. First, numerical simulation is carried out on a vertical channel that consists of an aluminum heater plate assembly at the center of the channel. The numerical model is treated as a conjugate heat transfer problem, and the concept of perturbation and blending is incorporated wherein the limiting solution of natural and forced convection is obtained in terms of average Nusselt number. These correlations are then blended to find a unified composite correlation that work very well for extreme limits of mixed convection. The Richardson number is chosen as an independent variable in the present analysis; as a result, the Nusselt number correlation is cogent for the mixed convection region. Upon performing the numerical simulations, the results of the mixed convection are then compared with experimental results available in the literature for the purpose of validation of the numerical solution. The results of the present work emphasize that, with minimum computational fluid dynamics (CFD) solutions, one can obtain a reasonably good composite correlation for the Nusselt number for mixed convection and also a substantial reduction of computations is possible ensuing an asymptotically flawless solution. © © 2019 by ASME.
Investigation of Mixed Convection Heat Transfer Through Metal Foams Partially Filled in a Vertical Channel by Using Computational Fluid Dynamics
(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2018) Kotresha, B.; Gnanasekaran, N.
Two-dimensional computational fluid dynamics simulations of mixed convection heat transfer through aluminum metal foams partially filled in a vertical channel are carried out numerically. The objective of the present study is to quantify the effect of metal foam thickness on the fluid flow characteristics and the thermal performance in a partially filled vertical channel with metal foams for a fluid velocity range of 0.05-3 m/s. The numerical computations are performed for metal foam filled with 40%, 70%, and 100% by volume in the vertical channel for four different pores per inch (PPIs) of 10, 20, 30, and 45 with porosity values varying from 0.90 to 0.95. To envisage the characteristics of fluid flow and heat transfer, two different models, namely, Darcy Extended Forchheirmer (DEF) and Local thermal non-equilibrium, have been incorporated for the metal foam region. The numerical results are compared with experimental and analytical results available in the literature for the purpose of validation. The results of the parametric studies on vertical channel show that the Nusselt number increases with the increase of partial filling of metal foams. The thermal performance of the metal foams is reported in terms of Colburn j and performance factors. © Copyright 2018 by ASME.
Natural Convection Through High Porosity Metal Foamsâ€”A Numerical Study
(Springer Science and Business Media Deutschland GmbH, 2021) Kotresha, B.; Jadhav, P.H.; Gnanasekaran, N.
Numerical analysis of natural convection through highly porous metal foams attached to the aluminium plates is performed in this study. A heater sandwiched between two aluminium plates attached with aluminium metal foams of different pores per inch (PPI) is considered for the present analysis. Initially, experiments are carried out for aluminium plate-heater assembly for different heat inputs. In the numerical investigation, the aluminium plates are attached with metal foams on either side for further analysis. A well-known Darcy extended Forchheimer flow and LTNE thermal models are considered for the metal foam in the computations. The natural convection is modelled using Boussinesq approximation. Initially, the numerical result for the plate without metal foam is validated with the experimental results for different heat inputs. The results show that the Nusselt number decreases with the increase of metal foam pore density (PPI) and increases with the increase in Rayleigh number. Â© 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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 Ltd
Numerical Simulations of Flow-Assisted Mixed Convection in a Vertical Channel Filled with High Porosity Metal Foams
(Taylor and Francis Ltd., 2020) Kotresha, B.; Gnanasekaran, N.; Balaji, C.
In this work, two-dimensional numerical simulations of flow-assisted mixed convection in a vertical channel filled with high porosity metal foams have been carried out by using the commercial ANSYS FLUENT. In order to enhance heat transfer, the vertical channel is filled with aluminum metal foams of different pores per inch (PPI). Four different metal foams PPI 10, 20, 30, and 45, with porosity values varying from 0.90 to 0.95 are considered in this study. The geometry under consideration consists of metal foam attached to the aluminum plate in the vertical channel and the resulting problem becomes conjugate heat transfer. The metal foam region is considered as a homogeneous porous medium with the Darcy Extended Forchheirmer model to evaluate the flow characteristics while the local thermal non-equilibrium heat transfer model is considered for the heat transfer analysis. Initially, numerical results are compared with the experimental results available in literature and the agreement was found to be good. Parametric studies show that as the metal foam PPI increases, the pressure drop increases, while the heat transfer is seen to increase with an increase in the pore density of the metal foam. © 2019, © 2019 Taylor & Francis Group, LLC.
Numerical Simulations of Fluid Flow and Heat Transfer through Aluminum and Copper Metal Foam Heat Exchanger–A Comparative Study
(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Kotresha, B.; Gnanasekaran, N.
This article discusses about a numerical simulation of a metal foam heat exchanger system carried out by a commercial software. A metal foam layer is attached to the bottom of the heat exchanger to absorb heat from the exhaust hot gas leaving the system. Two types of metal foams with two different pores per inch (PPI) values are considered for heat transfer enhancement. Similarly, two different materials Aluminum and copper, that poses high thermal conductivity, metal foams are considered for the present numerical simulations. The heat exchanger system is simulated over a range of 6–30 m/s fluid velocity. The proposed simulations are compared with theoretical and experimental data available in the literature. The goal is to improve the thermal performance of the heat exchanger by decreasing the pressure drop and maximizing the heat transfer rate. Finally, it has been noticed that the velocity of the fluid decreases as PPI increases at the expense of its pressure drop. The copper metal foam gives a maximum increase of 4–10% heat transfer rate compared to aluminum metal foams for a fluid velocity of 30 m/s. © 2019, © 2019 Taylor & Francis Group, LLC.
Prediction of heat transfer with discrete heat sources in a vertical channel filled Â ith high porosity metal foam
(Dalian University of Technology, 2018) Kotresha, B.; Gnanasekaran, N.
This paper discusses about the numerical prediction of isothermal condition with discrete heat sources in a vertical channel filled with high porosity metal foams. The problem considered consists of a vertical channel in which discrete heat source assembly is placed at the centre and high porosity metal foams are placed on either side of the aluminium plates to enhance the heat transfer. The flow through the metal foam porous medium is predicted by using Darcy Extended Forchheimer model and Local thermal non-equilibrium model as well as local thermal equilibrium model is used for heat transfer prediction. The results are presented in terms of temperature excess over the ambient for both empty and metal foam filled channel. Finally, the heat input through the discrete heat sources is varied to obtain an isothermal condition on all the heat sources at a constant inlet velocity. Â© 2018 by the authors of the abstracts.
Prediction of heat transfer with discrete heat sources in a vertical channel filled �ith high porosity metal foam
(2018) Kotresha, B.; Gnanasekaran, N.
This paper discusses about the numerical prediction of isothermal condition with discrete heat sources in a vertical channel filled with high porosity metal foams. The problem considered consists of a vertical channel in which discrete heat source assembly is placed at the centre and high porosity metal foams are placed on either side of the aluminium plates to enhance the heat transfer. The flow through the metal foam porous medium is predicted by using Darcy Extended Forchheimer model and Local thermal non-equilibrium model as well as local thermal equilibrium model is used for heat transfer prediction. The results are presented in terms of temperature excess over the ambient for both empty and metal foam filled channel. Finally, the heat input through the discrete heat sources is varied to obtain an isothermal condition on all the heat sources at a constant inlet velocity. � 2018 by the authors of the abstracts.