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Journal ArticleDOI

A Simple Thermal Resistance Model for Open Cell Metal Foams

01 Mar 2013-Journal of Heat Transfer-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 135, Iss: 3, pp 032601
TL;DR: In this paper, the authors present a methodology for obtaining the convective heat transfer coefficient from the wall of a heated aluminium plate, placed in a vertical channel filled with open cell metal foams.
Abstract: This paper presents a methodology for obtaining the convective heat transfer coefficient from the wall of a heated aluminium plate, placed in a vertical channel filled with open cell metal foams. For accomplishing this, a thermal resistance model from literature for metal foams is suitably modified to account for contact resistance. The contact resistance is then evaluated using the experimental results. A correlation for the estimation of the contact resistance as a function of the pertinent parameters, based on the above approach is developed. The model is first validated with experimental results in literature for the asymptotic case of negligible contact resistance. A parametric study of the effect of different foam parameters on the heat transfer is reported with and without the presence of contact resistance. The significance of the effect of contact resistance in the mixed convection and forced convection regimes is discussed. The procedure to employ the present methodology in an actual case is demonstrated and verified with additional, independent experimental data.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a steady-state test system was constructed to measure the effective thermal conductivities of composite PCMs, which were also theoretically calculated based on the correlations and models from the literature.

275 citations

Journal ArticleDOI
TL;DR: In this paper, two ideal three-dimensional geometries are generated using cylinder-joint and sphere-subtraction methods, respectively, and an analytical model of heat transfer in a foamed heat exchanger is then proposed using the transfer matrix method and one-equation model.

30 citations

Journal ArticleDOI
TL;DR: In this paper, an open-Kelvin model was used to investigate the heat transfer characteristics of porous media with high porosity within a velocity range of 4-90m/s.

29 citations

Journal ArticleDOI
TL;DR: In this article, a combination of the volume-of-fluid (VOF) and enthalpy-porosity (EPP) methods was employed for numerical investigation of solidification.
Abstract: Infiltration of phase change materials (PCM) into highly conductive porous structures effectively enhances the thermal conductivity and phase change (solidification and melting) characteristics of the resulting thermal energy storage (TES) composites. However, the infiltration process contributes to formation of voids as micron-size air bubbles within the pores of the porous structure. The presence of voids negatively affects the thermal and phase change performance of TES composites due to the thermophysical properties of air in comparison with PCM and porous structure. This paper investigates the effect of voids on solidification of PCM, infiltrated into the pores of graphite foam as a highly conductive porous medium with interconnected pores. A combination of the volume-of-fluid (VOF) and enthalpy-porosity methods was employed for numerical investigation of solidification. The proposed method takes into account the variation of density with temperature during phase change and is able to predict the volume shrinkage (volume contraction) during the solidification of liquids. Furthermore, the presence of void and the temperature gradient along the liquid–gas interface (the interface between void and PCM) can trigger thermocapillary effects. Thus, Marangoni convection was included during the solidification process and its importance was elucidated by comparing the results among cases with and without thermocapillary effects. The results indicated that the presence of voids within the pores causes a noticeable increase in solidification time, with a sharper increase for cases without thermocapillary convection. For verification purposes, the amount of volume shrinkage during the solidification obtained from numerical simulations was compared against the theoretical volume change due to the variation of density for several liquids with contraction and expansion during the freezing process. The two sets of results exhibited good agreement.

18 citations

Journal ArticleDOI
TL;DR: In this paper, a new design of a circular pipe partially filled with a grooved metallic foam is proposed in order to improve the hydraulic and thermal performance, and consequently reduce the pumping power losses and the metal foam volume.

14 citations

References
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Book
01 Oct 1991
TL;DR: In this article, the authors identify the principles of transport in porous media and compare the available predicted results, based on theoretical treatments of various transport mechanisms, with the existing experimental results, and the theoretical treatment is based on the volume-averaging of the momentum and energy equations with the closure conditions necessary for obtaining solutions.
Abstract: Although the empirical treatment of fluid flow and heat transfer in porous media is over a century old, only in the last three decades has the transport in these heterogeneous systems been addressed in detail. So far, single-phase flows in porous media have been treated or at least formulated satisfactorily, while the subject of two-phase flow and the related heat-transfer in porous media is still in its infancy. This book identifies the principles of transport in porous media and compares the available predicted results, based on theoretical treatments of various transport mechanisms, with the existing experimental results. The theoretical treatment is based on the volume-averaging of the momentum and energy equations with the closure conditions necessary for obtaining solutions. While emphasizing a basic understanding of heat transfer in porous media, this book does not ignore the need for predictive tools; whenever a rigorous theoretical treatment of a phenomena is not available, semi-empirical and empirical treatments are given.

2,551 citations

Journal ArticleDOI
TL;DR: In this article, the effective thermal conductivity (ke), permeability (K), and inertial coefficient (f) of high porosity metal foams were derived by considering a circular blob of metal at the intersection of two fibers.

998 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental and numerical study of forced convection in high porosity (e∼0.89-0.97) metal foams was conducted using air as the fluid medium.
Abstract: We report an experimental and numerical study of forced convection in high porosity (e∼0.89-0.97) metal foams. Experiments have been conducted with aluminum metal foams in a variety of porosities and pore densities using air as the fluid medium. Nusselt number data has been obtained as a function of the pore Reynolds number. In the numerical study, a semi-empirical volume-averaged form of the governing equations is used. The velocity profile is obtained by adapting an exact solution to the momentum equation. The energy transport is modeled without invoking the assumption of local thermal equilibrium. Models for the thermal dispersion conductivity, k d , and the interstitial heat transfer coefficient, h sf , are postulated based on physical arguments. The empirical constants in these models are determined by matching the numerical results with the experimental data obtained in this study as well as those in the open literature. Excellent agreement is achieved in the entire range of the parameters studied, indicating that the proposed treatment is sufficient to model forced convection in metal foams for most practical applications

911 citations

Journal ArticleDOI
TL;DR: In this article, a geometrical effective thermal conductivity model of a saturated porous metal foam was developed, based on the idealized three-dimensional basic cell geometry of a foam, the tetrakaidecahedron.

693 citations

Journal ArticleDOI
TL;DR: In this paper, open-cell metal foams with an average cell diameter of 2.3 mm were manufactured from 6101-T6 aluminum alloy and were compressed and fashioned into compact heat exchangers.

681 citations