Modeling of Conduction and Natural Convection in Ice-Water Systems Containing Porous Metal Foams

2013 ◽  
Author(s):  
Sylvain Bories ◽  
B. Rabi Baliga
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Metal Foam ◽  
Porous Metal ◽  
Water Systems ◽  
Metal Foams ◽  
Local Thermal Equilibrium ◽  
Numerical Predictions ◽  
Laminar Natural Convection ◽  
Ice Water

Mathematical models and numerical predictions of heat conduction and laminar natural convection in ice-water systems containing porous metal foams are presented, in the context of computationally convenient two-dimensional steady-state problems with rectangular calculation domains. The Darcy-Brinkman-Forchheimer equations were used to model momentum transfer in the liquid-water-metal-foam region. For modeling the heat transfer, volume-averaged equations governing two intrinsic-phase-average temperature fields were used: one for the metal foam and the other for the water (solid or liquid). The following improvements are proposed: novel expressions for the interfacial (metal-water) heat transfer coefficient in both the convection and conduction regimes; and effective thermal conductivity correlations that provide consistency between the formulations of one-temperature and two-temperature models in the limit of local thermal equilibrium. A well-established fixed-grid, co-located, finite volume method (FVM) was adapted and used for the numerical solutions. The proposed models and FVM were used to solve the test and demonstration problems involving conduction and laminar natural convection in ice-water-aluminum-foam systems contained in rectangular enclosures. The findings and results of these investigations are presented and discussed in this paper.

Microtomography-Based Analysis of Pressure Drop and Heat Transfer Through Open Cell Metal Foams

2013 ◽  
Author(s):  
M. Oliviero ◽  
S. Cunsolo ◽  
W. M. Harris ◽  
M. Iasiello ◽  
W. K. S. Chiu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Thermal Characteristics ◽  
Industrial Applications ◽  
Metal Foams ◽  
Surface Evolver ◽  
Periodic Cell ◽  
Numerical Predictions

Their light weight, open porosity, high surface area per unit volume and thermal characteristics make metal foams a promising material for many industrial applications involving fluid flow and heat transfer. Pressure drop and heat transfer of porous media have inspired a number of experimental and numerical studies. Many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models. Most studies are based on idealized periodic cell structures. In this study, the true 3-D micro-structure of the metal foam is obtained by employing x-ray computed microtomography (XCT). For comparison, ideal Kelvin foam structures are developed in the free-to-use software “Surface Evolver” surface energy minimization program. Pressure drop and heat transfer are then investigated using the CFD Module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out.

Numerical Analysis of Heat Transfer and Pressure Drop in Metal Foams for Different Morphological Models

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Marcello Iasiello ◽  
Salvatore Cunsolo ◽  
Maria Oliviero ◽  
William M. Harris ◽  
Nicola Bianco ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Industrial Applications ◽  
Metal Foams ◽  
The Real ◽  
Numerical Predictions ◽  
The Ideal

Because of their light weight, open porosity, high surface area per unit volume, and thermal characteristics, metal foams are a promising material for many industrial applications involving fluid flow and heat transfer. The pressure drop and heat transfer in porous media have inspired a number of experimental and numerical studies, and many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models, and most studies are based on idealized periodic cell structures. In this study, the true three-dimensional microstructure of the metal foam is obtained by employing x-ray computed microtomography (XCT). This is the “real” structure. For comparison, ideal Kelvin foam structures are developed in the free-to-use software “surface evolver” surface energy minimization program. These are “ideal” structures. Pressure drop and heat transfer are then investigated in each structure using the CFD module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out. The predictions showed that heat transfer characteristics are very close for low values of Reynolds number, but larger Reynolds numbers create larger differences between the results of the ideal and real structures. Conversely, the differences in pressure drop at any Reynolds number are nearly 100%. Results from the models are then validated by comparing them with experimental results taken from the literature. The validation suggests that the ideal structure poorly predicts the heat transfer and pressure drops.

scholarly journals Numerical study on heat transfer performance of vacuum tube solar collector integrated with metal foams

2019 ◽  
Vol 14 (3) ◽  
pp. 344-350
Author(s):  
Yalin Lu ◽  
Zhenqian Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Solar Collector ◽  
Heat Transfer Performance ◽  
Metal Foam ◽  
Metal Foams ◽  
Local Thermal Equilibrium ◽  
Transfer Performance ◽  
Vacuum Tube ◽  
The Impact

Abstract Applying vacuum tube solar collector is one effective way to reduce heat loss in solar collection. However, low conductivity of pure water leads to poor heat transfer performance in vacuum tube. In order to enhance heat transfer in tube, a novel vacuum tube solar collector using water as medium and metal foams as filler is presented, which consists of outer glass tube, inner metal tube and metal foam filler. The heating process of vacuum tube with metal foam filler of different structural parameters (porosity in range of 0.8991–0.9546 and PPI of 5, 10 and 20) is numerically studied and local thermal equilibrium model is applied.The temperature distribution of vacuum tube collectors with and without metal foam filler are compared. The impact of porosity and PPI on heat transfer performance is obtained. The results show that metal foams plays a great role in heat transfer enhancement for vacuum tube solar collector. Thermal performance of the novel vacuum tube solar collector is influenced by porosity and PPI of metal foams. Compared with traditional vacuum tube solar collector, the proposed vacuum tube solar collector has better thermal performance and greater potential in solar building integration.

A Synergistic Combination of Thermal Models for Optimal Temperature Distribution of Discrete Sources Through Metal Foams in a Vertical Channel

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Banjara Kotresha ◽  
N. Gnanasekaran
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Source ◽  
Metal Foam ◽  
Vertical Channel ◽  
Metal Foams ◽  
Local Thermal Equilibrium ◽  
High Porosity ◽  
Heat Sources ◽  
Excess Temperature

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.

EXPERIMENTAL STUDY OF FREE CONVECTION HEAT TRANSFER IN THE POROUS METAL-FOAM HEAT SINK

2013 ◽  
Vol 37 (3) ◽  
pp. 841-850 ◽  
Author(s):  
Tzer-Ming Jeng ◽  
Sheng-Chung Tzeng ◽  
Zhi-Ting Yeh
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Metal Foam ◽  
Convection Heat Transfer ◽  
Porous Metal ◽  
Metal Foams ◽  
Heat Sinks ◽  
Convection Heat ◽  
Pore Density ◽  
Free Convection Heat

This study experimentally investigated the free convection heat transfer characteristics of the annular metal-foam heat sinks. The results showed that the heat transfer coefficient (h) decreased as the pore density of metal foams increased when the thickness (tc) of the annular metal foams equaled 5 mm, but the (h) increased as the pore density increased when tc = 11 and 14.5 mm. Besides, the (h) increased firstly and then decreased as (tc) increased. There was better heat transfer effect when tc = 11 mm in the present study.

Interstitial Heat Transfer Coefficient and Dispersion Conductivity in Compressed Metal Foam Heat Sinks

2006 ◽  
Vol 129 (2) ◽  
pp. 113-119 ◽  
Author(s):  
Sheng-Chung Tzeng ◽  
Tzer-Ming Jeng
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Metal Foam ◽  
Rectangular Channel ◽  
Metal Foams ◽  
High Porosity ◽  
Fluid Medium ◽  
Numerical Predictions

This work experimentally and numerically investigates the heat transfer in uncompressed∕compressed metal foams. Experiments were conducted to obtain the thermal characteristics of a rectangular channel filled with aluminum foams using air as the fluid medium. The experimental data reveal that the uncompressed sample has a larger Nusselt number (Nu) than the compressed sample. The 0.93 porosity sample has the largest average Nu followed by the 0.7 porosity sample; the 0.8 porosity sample has the worst average Nu. The experimental data concerning the 0.93 porosity samples (uncompressed samples) were consistent with the numerical predictions obtained using the model for high-porosity metal foam, reported elsewhere. Finally, a numerical model to simulate flow and heat transfer characteristics in compressed metal foams is presented and the interstitial heat transfer coefficient and dispersion conductivity were semi-empirically determined.

STUDY ON SOLIDIFICATION OF PHASE CHANGE MATERIAL IN FRACTAL POROUS METAL FOAM

Fractals ◽  
2015 ◽  
Vol 23 (01) ◽  
pp. 1540003 ◽  
Author(s):  
CHENGBIN ZHANG ◽  
LIANGYU WU ◽  
YONGPING CHEN
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Pore Structure ◽  
Phase Change Material ◽  
Fractal Structure ◽  
Metal Foam ◽  
Porous Metal ◽  
Solid Matrix ◽  
Transfer Model ◽  
Change Material

The Sierpinski fractal is introduced to construct the porous metal foam. Based on this fractal description, an unsteady heat transfer model accompanied with solidification phase change in fractal porous metal foam embedded with phase change material (PCM) is developed and numerically analyzed. The heat transfer processes associated with solidification of PCM embedded in fractal structure is investigated and compared with that in single-pore structure. The results indicate that, for the solidification of phase change material in fractal porous metal foam, the PCM is dispersedly distributed in metal foam and the existence of porous metal matrix provides a fast heat flow channel both horizontally and vertically, which induces the enhancement of interstitial heat transfer between the solid matrix and PCM. The solidification performance of the PCM, which is represented by liquid fraction and solidification time, in fractal structure is superior to that in single-pore structure.

Laminar Natural Convection Heat Transfer in a Differentially Heated Square Cavity Due to a Thin Fin on the Hot Wall

2003 ◽  
Vol 125 (4) ◽  
pp. 624-634 ◽  
Author(s):  
Xundan Shi ◽  
J. M. Khodadadi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Computational Study ◽  
Convection Heat Transfer ◽  
Square Cavity ◽  
Left Wall ◽  
Flow Modification ◽  
Laminar Natural Convection ◽  
Rayleigh Numbers ◽  
Blockage Effect

A finite-volume-based computational study of steady laminar natural convection (using Boussinesq approximation) within a differentially heated square cavity due to the presence of a single thin fin is presented. Attachment of highly conductive thin fins with lengths equal to 20, 35 and 50 percent of the side, positioned at 7 locations on the hot left wall were examined for Ra=104,105,106, and 107 and Pr=0.707 (total of 84 cases). Placing a fin on the hot left wall generally alters the clockwise rotating vortex that is established due to buoyancy-induced convection. Two competing mechanisms that are responsible for flow and thermal modifications are identified. One is due to the blockage effect of the fin, whereas the other is due to extra heating of the fluid that is accommodated by the fin. The degree of flow modification due to blockage is enhanced by increasing the length of the fin. Under certain conditions, smaller vortices are formed between the fin and the top insulated wall. Viewing the minimum value of the stream function field as a measure of the strength of flow modification, it is shown that for high Rayleigh numbers the flow field is enhanced regardless of the fin’s length and position. This suggests that the extra heating mechanism outweighs the blockage effect for high Rayleigh numbers. By introducing a fin, the heat transfer capacity on the anchoring wall is always degraded, however heat transfer on the cold wall without the fin can be promoted for high Rayleigh numbers and with the fins placed closer to the insulated walls. A correlation among the mean Nu, Ra, fin’s length and its position is proposed.

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