Direct Simulation of Interstitial Heat Transfer Coefficient Between Paraffin and High Porosity Open-Cell Metal Foam

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Change Process ◽  
Energy Equation ◽  
Metal Foam ◽  
Equation Model ◽  
High Porosity ◽  
Direct Simulation ◽  
Open Cell ◽  
Transfer Region

The interstitial heat transfer coefficient (IHTC) is a key parameter in the two-energy equation model usually employed to investigate the thermal performance of high porosity open-cell metal foam/paraffin composite phase change material. Due to the existence of weak convection of liquid paraffin through metal foam during phase change process, the IHTC should be carefully determined for a low Reynolds number range (Re = 0–1), which however has been rarely addressed in the literature. In this paper, a direct simulation at foam pore scale is carried out to determine the IHTC between paraffin and metal foam at Re = 0–1. For this purpose, the cell structures reflecting realistic metal foams are first constructed based on the three-dimensional (3D) Weaire–Phelan foam cell to serve as the representative elementary volume (REV) of metal foam for direct simulation. Then, by solving the Navier–Stokes equations and energy equation for the REV, the influences of Reynolds number (Re), Prandtl number (Pr), foam porosity (ε), and pore density (PPI) on the dimensionless IHTC, i.e., the Nusselt number Nuv, are investigated. According to the numerical results, a correlation of Nuv at Re = 0–1 is proposed for metal foam/paraffin composite material, which covers both diffusion-dominated interstitial heat transfer region (Re ≤ 0.1) and convection-dominated interstitial heat transfer region (0.1 < Re ≤ 1). Finally, the applicability of this correlation in the two-energy equation model for solid–liquid phase change of paraffin in metal foam is validated by comparing the model predicted melting front with that of experimental observations made in this study. It is found that the IHTC correlation proposed in this study can be used in the two-energy equation model for well predicting the phase change process of paraffin in metal foam.

Metal-Foam-Enhanced PCM Storage System: The Cylindrical Shell Geometry

2011 ◽  
Author(s):  
Nihad Dukhan
Keyword(s):  
Heat Transfer ◽  
Cylindrical Shell ◽  
Phase Change ◽  
Change Process ◽  
Metal Foam ◽  
Storage System ◽  
Open Loop ◽  
High Porosity ◽  
Phase Change Process ◽  
Thermal Conductivities

Phase-change systems remain to be widely used for storage of thermal energy such as the energy harnessed by solar collectors. The major disadvantage of phase change materials (PCMs) is their low thermal conductivities, which drastically slows the phase change process and causes wide temperature variations within PCMs, while requiring heat transfer area. Metal foams are one class of porous media that possess thermal conductivities that are an order of magnitude higher than PCMs. When embedded in PCMs, the random internal structure and high porosity of metal foam enhance and accelerate the phase change process without significantly reducing PCMs’ heat storage capacity. Unlike traditional PCM systems, the distribution of the foam ligaments in PCMs makes the melting and solidification processes uniform and less dependent on location inside PCMs. This also leads to shorter charging and discharging times. The design, fabrication and characterization of a small PCM-metal-foam thermal storage system are described in this paper. The core of the system is a cylindrical shell composed of 90%-porous open-cell aluminum foam filled with Paraffin-based PCM. The foam occupies only 10% of the total volume. The shell walls were fabricated from copper. The system was tested in an open loop wind tunnel. Results for the convection heat transfer coefficient and the effect of volumetric flow rate on the system’s performance were obtained. The heat transfer rate from the system was computed and discussed.

Numerical Study of Heat Conduction of High Porosity Open-Cell Metal Foam/Paraffin Composite at Pore Scale

2016 ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Pore Size ◽  
Metal Foam ◽  
Foam Cell ◽  
High Porosity ◽  
Pore Scale ◽  
Thermal Equilibrium State ◽  
Foam Structure ◽  
Open Cell

In this paper, a numerical model employing 3D foam structure represented by Weaire-Phelan foam cell is developed to study the steady heat conduction of high porosity open-cell metal foam/paraffin composite at the pore-scale level. Two conduction problems are considered in the cubic representative computation unit of the composite material: one with constant temperature difference between opposite sides of the cubic unit (that can be used to determine the effective thermal conductivity (ETC)) and the second with constant heat flux at the interface between metal foam and paraffin (that can be used to determine the interstitial conduction heat transfer coefficient (ICHTC)). The effects of foam pore structure parameters (pore size and porosity) on heat conduction are investigated for the above two problems. Results show that for the first conduction problem, the effect of foam structure on heat conduction (i.e. the ETC) is related to porosity rather than pore size. The essential reason is due to the thermal equilibrium state between metal foam and paraffin indicated by the negligible interstitial heat transfer. While for the second conduction problem with inherent thermal non-equilibrium effect, it shows that both porosity and pore size significantly influence the interstitial heat conduction (i.e. the ICHTC). Furthermore, the present ETC and ICHTC data are compared to the results in the published literature. It shows that our ETC data agree well with the reported experimental results, and are more accurate than the numerical predications based on body-centered-cubic foam cell in literature. And our ICHTC data are in qualitative agreement with the published numerical results, but the present results are based on a more realistic foam structure.

scholarly journals Numerical Simulation on Enhanced Heat Transfer of Metal Foam Based on LBM

2021 ◽  
Vol 2085 (1) ◽  
pp. 012028
Author(s):  
Zhongli Li ◽  
Peng Hu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Nusselt Number ◽  
Metal Foam ◽  
Metal Structure ◽  
Heat Transfer Process ◽  
Solid Particles ◽  
Distribution Model ◽  
High Porosity ◽  
Open Cell

Abstract Open cell foam metal has the characteristics of high porosity and large specific surface area. And it has developed rapidly in the related research of heat exchanger. Aiming at the convective heat transfer process of open cell metal structure with high porosity, a two-dimensional stochastic distribution model is established. Numerical simulation is carried out using the single-relaxation-time dual-distribution-function lattice-Boltzmann-method (BGK-DDF-LBM). For the non-ideal solid particles with unequal diameter and incomplete circular structure, the flow field is analyzed by taking the porosity of 0.964 as an example, and the dimensionless permeability is calculated. When the porosity is constant, the Nusselt number of the porous section increases with the increases of Reynolds number in the range of 10 to 100, which shows heat transfer performance. In addition, the Nusselt number of the porous section increases with the increase of porosity in the range of porosity from 0.900 to 0.980.

How Good Is Open-Cell Metal Foam as Heat Transfer Surface?

2009 ◽  
Vol 131 (10) ◽  
Author(s):  
Indranil Ghosh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Metal Foam ◽  
Heat Transfer Surface ◽  
High Porosity ◽  
Governing Parameter ◽  
Reynolds Analogy ◽  
Open Cell ◽  
F Factor ◽  
High Area

High porosity open-cell metal foam is considered to be an attractive choice for compact heat exchanger applications because of its high area density and superior thermal performance. A systematic study has been made in the present article to verify the suitability of the porous material as an extended heat transfer surface. The area goodness (j/f) factor has been chosen as performance evaluation criterion. This governing parameter has been computed using the existing correlations for the heat transfer and pressure drop coefficients. Conservative estimate shows that the thermohydraulic characteristics of high porosity open-cell metal foam are almost alike, if not better than those of the conventional heat transfer surfaces. Importantly, the analysis has been found to be consistent with the Reynolds analogy. This study helps the designer in making the initial selection of foam surfaces for the heat exchanger application.

Geometric Mean of Fin Efficiency and Effectiveness: A Parameter to Determine Optimum Length of Open-Cell Metal Foam Used as Extended Heat Transfer Surface

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Tisha Dixit ◽  
Indranil Ghosh
Keyword(s):  
Heat Transfer ◽  
Metal Foam ◽  
Geometric Mean ◽  
Fluid Velocity ◽  
High Surface ◽  
Metal Foams ◽  
Heat Sinks ◽  
High Porosity ◽  
Open Cell ◽  
Fin Efficiency

High porosity open-cell metal foams have captured the interest of thermal industry due to their high surface area density, low weight, and ability to create tortuous mixing of fluid. In this work, application of metal foams as heat sinks has been explored. The foam has been represented as a simple cubic structure and heat transfer from a heated base has been treated analogous to that of solid fins. Based on this model, three performance parameters namely, foam efficiency, overall foam efficiency, and foam effectiveness have been evaluated for metal foam heat sinks. Parametric studies with varying foam length, porosity, pore density, material, and fluid velocity have been conducted. It has been observed that geometric mean of foam efficiency and foam effectiveness can be a useful parameter to exactly determine the optimum foam length. Additionally, the variation in temperature profile of different foams heated from one end has been determined experimentally by cooling these with atmospheric air. The experimental results have been presented for open-cell metal foams (10 and 30 PPI) made of copper/aluminium/Fe–Ni–Cr alloy with porosity in the range of 0.908–0.964.

scholarly journals A Review of Thermo-Hydraulic Performance of Metal Foam and its Application as Heat Sinks for Electronics Cooling

2020 ◽  
Author(s):  
Yongtong Li ◽  
Liang Gong ◽  
Minghai Xu ◽  
Yogendra Joshi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Metal Foam ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Metal Foams ◽  
Hydraulic Performance ◽  
Heat Sinks ◽  
Research Progress ◽  
High Porosity

Abstract High porosity metal foams offer large surface area per unit volume and have been considered as effective candidates for convection heat transfer enhancement, with applications as heat sinks in electronics cooling. In this paper, the research progress in thermo-hydraulic performance characterization of metal foams and their application as heat sinks for electronics cooling are reviewed. We focus on natural convection, forced convection, flow boiling, and solid/liquid phase change using phase change materials (PCMs). Under these heat transfer conditions, the effects of various parameters influencing the performance of metal foam heat sink are discussed. It is concluded that metal foams demonstrate promising capability for heat transfer augmentation, but some key issues still need to be investigated regarding the fundamental mechanisms of heat transfer to enable the development of more efficient and compact heat sinks.

Numerical Investigation on the Effect of Aluminum Foam in a Latent Thermal Energy Storage

2015 ◽  
Author(s):  
Bernardo Buonomo ◽  
Davide Ercole ◽  
Oronzio Manca ◽  
Hasan Celik ◽  
Moghtada Mobedi
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Numerical Investigation ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Metal Foam ◽  
Local Thermal Equilibrium ◽  
Melting Time ◽  
High Porosity

In this paper, a numerical investigation on Latent Heat Thermal Energy Storage System (LHTESS) based on a phase change material (PCM) is accomplished. The geometry of the system under investigation is a vertical shell and tube LHTES made with two concentric aluminum tubes. The internal surface of the hollow cylinder is assumed at a constant temperature above the melting temperature of the PCM to simulate the heat transfer from a hot fluid. The other external surfaces are assumed adiabatic. The phase change of the PCM is modeled with the enthalpy porosity theory while the metal foam is considered as a porous media that obeys to the Darcy-Forchheimer law. The momentum equations are modified by adding of suitable source term which it allows to model the solid phase of PCM and natural convection in the liquid phase of PCM. Both local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) models are examined. Results as a function of time for the charging phase are carried out for different porosities and assigned pore per inch (PPI). The results show that at high porosity the LTE and LTNE models have the same melting time while at low porosity the LTNE has a larger melting time. Moreover, the presence of metal foam improves significantly the heat transfer in the LHTES giving a very faster phase change process with respect to pure PCM, reducing the melting time more than one order of magnitude.

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