Porous Metal Foam Research Articles

Pore-scale computational analyses of non-Darcy flow through highly porous structures with various degrees of geometrical complexity

This study relies on pore-scale direct computations of velocity fields within highly porous open-cell metal foams (OCF) characterized by differing geometrical attributes. The Navier-Stokes equations are solved across a suite of synthetically generated pore structures to assess relationships between attributes/patterns of the pore-scale flow field and OCF pore-structure. This study explores the effect of porosity and number of pores per inch (PPI) of the foam structures on the onset of non-Darcy flow, and values of Forchheimer coefficient and permeability of the system. The results show that the complexity of the pore flow patterns causes the onset of non-Darcy flow to occur at low values of Reynolds number (Rek). The analyses encompass a wide range of values of Rek corresponding to Darcy and non-Darcy flow regimes. The results suggest that permeability increases up to 30% by increasing porosity from 0.85 to 0.95, the corresponding onset of a non-Darcy flow regime taking place for Rek= 1.77 and 1.44, respectively. Otherwise, a significant decrease of permeability is documented upon increasing the PPI value from 10 to 40, the corresponding onset of a non-Darcy flow regime taking place for Rek= 1.77 and 0.28, respectively.

Small size-effect isogeometric analysis for linear and nonlinear responses of porous metal foam microplate

The main objective of this paper is to explore the linear and nonlinear responses of porous metal foam micro-plate using a modified couple stress theory coupled with isogeometric analysis. The material properties of metal foam micro-plate are derived from three porosity variation models, namely uniform, symmetric and asymmetric variation across the thickness of the microplate. The stress-strain and the modified couple stress constitutive relations are obtained using a seventh order distributed function based on the general shear deformation theory. Furthermore, the Hamilton’s principle is utilized to establish the size-effect equilibrium equations for metal foam micro-plate. The presented numerical solution is able to capture the small size effect of microplate by considering the material length scale parameter in the classical continuum theory. The reported results demonstrate the effect of small size-effect, porosity variation, porosity coefficient, slenderness ratio on free vibration, linear and nonlinear static bending of porous metal foam micro-plate. The role of pattern porosity variation in the nonlinear responses becomes more important by increasing the porosity coefficient. The pattern of symmetric porosity presents the best performance of linear and nonlinear responses.

On Numerical Modeling of Thermal Performance Enhancementof a Heat Thermal Energy Storage System Using a Phase Change Material and a Porous Foam

In this investigation, a comprehensive numerical analysis of the flow involved in an open-ended straight channel fully filled with a porous metal foam saturated and a phase change material (paraffin) has been performed using a single relaxation time lattice Boltzmann method (SRT-LBM) at the representative elementary volume (REV) scale. The enthalpy-based approach with three density functions has been employed to cope with the governing equations under the local thermal non-equilibrium (LTNE) condition. The in-house code has been validated through a comparison with a previous case in literature. The pore per inch density (10≤PPI≤60) and porosity (0.7≤ε≤0.9) effects of the metal structure were analyzed during melting/solidifying phenomena at two Reynolds numbers (Re = 200 and 400). The relevant findings are discussed for the LTNE intensity and the entropy generation rate (Ns). Through the simulations, the LTNE hypothesis turned out to be secure and valid. In addition, it is maximum for small PPI value (=10) whatever the parameters deemed. On the other hand, high porosity (=0.9) is advised to reduce the system’s irreversibility. However, at a moderate Re (=200), a small PPI (=10) would be appropriate to mitigate the system irreversibility during the charging case, while a large value (PPI = 60) might be advised for the discharging case. In this context, it can be stated that during the melting period, low porosity (=0.7) with low PPI (=10) improves thermal performance, reduces the system irreversibility and speeds up the melting rate, while for high porosity (=0.9), a moderate PPI (=30) should be used during the melting process to achieve an optimal system.

Energy, exergy, environmental and economic analyzes (4E) and multi-objective optimization of a PEM fuel cell equipped with coolant channels

In the current research, the energy, exergy, environmental and economic (4E) analyzes of a PEM fuel cell are investigated. Parameters related to exergy are studied by considering the environmental effects and operating conditions of the PEM fuel cell. Multi-objective optimization is applied to maximize output power and efficiency and minimize environmental impacts and cost. The fuel cell is simulated with coolant channels and the effects of using porous metal foam inside the gas channels and coolant channels are investigated on the distribution of hydrogen and liquid water. The effect of using a hybrid nanofluid as a high potential liquid to keep the fuel cell cool is investigated. Optimal output power and optimal cost are provided according to the number of different cells. Optimal efficiencies (energy and exergy) and optimal environmental characteristics are likewise presented in a wide range of current densities. The results show that the simultaneous use of nanofluid and porous metal foam for cooling the fuel cell may not be appropriate. Furthermore, the effect of using metal foam is recommended for better cooling (increased heat transfer) of the fuel cell. Likewise, the use of porous metal foam inside the anode channel affects the distribution of hydrogen and liquid water. The effect of using porous foam in Re = 300 and above is significant so that in Re = 300, a 48% increase in heat transfer compared to the channel without porous foam can be seen. Besides, the percentage of reduction of nanofluid heat transfer in the presence of porous foam (in Re = 500) compared to pure water is 7.5%.

Thermal and hydrodynamic behavior of forced convection gaseous slip flow in a Kelvin cell metal foam

Porous metallic foams are a key material in numerous thermal and hydraulic applications. Gas flows in such micro/nanoporous systems deviate from classical continuum descriptions due to nonequilibrium in gas dynamics, and the resulted heat and mass transport show variation by rarefaction. This study performed a wide range of pore-level analysis of convective gas flows in a Kelvin cell model at different porosities and working conditions. Rarefaction effects onto permeability and heat transfer coefficients were calculated through Darcy to Forchheimer flow regimes. Permeability increased up to 60% by increasing rarefaction while this enhancement decreased by increasing porosity. At the same time, rarefaction lessened inertial effects such that Forchheimer coefficients decreased substantially. At high flow velocities, the increase in rarefaction considerably decreased the effect of drag forces. Hence, hydrodynamic enhancement due to rarefaction was found to increase by increasing Reynolds number. On the other hand, positive influence of boundary slip and negative influence of temperature jump developing between gas and solid almost canceled each other for the studied low heat flux region of highly conductive metal foam structures. Hence, Nusselt numbers were found mostly related to Reynolds number independent from rarefaction. We described Nusselt value based on power law model as a function of Reynolds and porosity. Results and the proposed model are important to accurately predict the thermal and hydrodynamic performance of metal foams in the 80 PPI range.

Thermodynamic analysis of entropy generation in a horizontal pipe filled with high porosity metal foams

In the field of thermal management of electronic equipment , examining entropy generation properties is extremely useful. The entropy production experiments have been expanded to porous media using high porosity metal foams. The entropy production/generation for forced convection heat transfer in a tube is quantified via a numerical research. In the field of air stream direction, the horizontal pipe is entirely filled with nickel metal foam of 0.6 m length. For the isotropic porous metal foam zone, the Darcy-extended Forchheimer (DEF) flow is used to capture the dynamics of flow and local thermal non-equilibrium (LTNE) model is used for analyzing the heat transport phenomenon, while the k-ɛ turbulent model is used for the non-foam porous region of the tube. The effect of fully filled nickel metallic foam with different pore densities of 10, 20, and 30 metal foam with a porosity of 0.85 is being investigated. The computational solutions presented here are supported by experimental results published in the literature. The outlet exergy of the system rises with higher flow rates and falls with higher metal foam pore densities. The results of entropy generation due to thermal and fluid friction and Bejan number conceptions are also shown and discussed.

Recent advancements in latent heat phase change materials and their applications for thermal energy storage and buildings: A state of the art review

Phase change materials (PCMs) have received substantial interest for their ability to store and release latent heat for energy conservation and thermal control purposes. PCMs are available in a variety of latent heat and melting points but their performance is low due to low value of thermal conductivity which limits its usage. The addition of highly thermal conductivity nanoparticles, porous metal foams and encapsulation methods have been used to address this issue and try to fix the low thermal conductivity of PCMs which is broadly discussed in this manuscript. The ability of PCM to store and release the thermal energy prompted the researchers to use it in potential applications. The energy retained and emitted by PCMs may be used for a variety of purposes, such as in photovoltaic (PV) panels, thermoelectric generators, building air-conditioning, air and water heating systems, heat exchangers, desalination solar stills, textiles, thermal management of electronic equipment and batteries and food packaging. Therefore, in this review, first the advancements in thermal properties of PCMs are thoroughly discussed in terms of enhancement in melting and solidification rates. After that, the use of PCMs in various applications is then explored, and conclusions are drawn accordingly. Based on analysis of recent literature, it was discovered that the phase transition temperature, phase transition enthalpy and thermal conductivity are three important parameters for the selection of an appropriate PCM for use in various applications. The current status of these advanced energy storage materials is also presented in this review. Lastly, some challenges and future recommendation are also proposed for future researchers which will bring a revolution in thermal management field.

Effects of gradient porous metal foam on the melting performance and energy storage of composite phase change materials subjected to an internal heater: A numerical study and PIV experimental validation

This work aims to explore the effects of gradient porous metal foam on the 3D melting heat transfer as well as the heat storage performance of a latent heat thermal energy storage (LHTES) unit inside an internal heated cubic cavity. A modified structure of metal foam with gradient porosity of three stratification layers is proposed to optimize the melting characteristic of the composite phase change materials. The enthalpy-porosity method is adopted to model melting process, and the Darcy-Forchheimer law and local thermal non-equilibrium model are assumed for metal foam. The numerical code of proposed model is in good consistency with the experimental results of particle image velocimetry (PIV) visualization. The effects of porosity gradient with equal and non-equal stratification heights, as well as pore per inch (PPI) on the melting performance, heat transfer and heat storage are investigated. The results indicate that the competitive relation between the conduction and convection induced by the gradient porosity influences the heat transfer and energy storage. The energy storage of negative gradient is greater than that of positive gradient, but the average rate of energy storage of the former is lower than that of the latter. In the middle melting stage, the total average Nusselt number increases with larger porosity gradient for positive cases and decreases for negative cases. With the increase of the stratification height of middle layer, the heat transfer efficiency of positive cases weakens, while it is enhanced for negative cases. Moreover, the increase of PPI can reinforce the conduction effect and improve the average rate of energy storage of the LHTES unit for both positive and negative cases.

Optimal hydro-thermal characteristics of a porous annular elliptic pipe using response surface method

Natural convection of pure water within an annular condensed elliptic pipe fully filled with saturated porous metal foam is computationally evaluated. A single-phase fluid with the Darcy-Forchheimer model and Local-Thermal-Equilibrium between fluid and solid is implemented for water flow through the porous zone. The outer and inner surfaces of the annular pipe are exposed to constant cold temperature and variable hot temperatures, respectively. The desirable hydraulic-thermal features for the hot surface temperature of the inner pipe (Th) and contraction ratio (CR) are considered. After achieving the optimum of Th and CR, the response surface method (RSM) is conducted to maximize heat transfer rate and minimise skin friction coefficient by utilising the multi-objective optimum design for porous metal foam properties such as porosity (ε), viscous resistance (1/K) and inertial resistance (C) simultaneously. The key results show that the local and average Nusselt number and heat transfer rate are enhanced, while the local and average skin friction coefficients have been increased with hot surface temperature increase and contraction ratio decrease. In addition, RSM shows that porosity (ε) and viscous resistance of metal foam (1/K) have a major effect on hydro-thermal efficiency enhancement, while inertial resistance (C) has a minor effect on the desired responses. Consequently, for any value of inertial resistance (C), the optimal values of porous media properties are ε = 0.95, 1/K = 106. This investigation provides an original method and useful guidance for the optimum design of the annular condensed elliptic pipe.

Thermally annealed self-assembled three-dimensional graphene for direct construction of porous flow distributor in polymer electrolyte membrane fuel cell

Self-assembled three-dimensional graphene (STG), which is constructed via advanced boiling method (ABM) has advantages in terms of low-cost, facile procedures, and needless to use any backbone structure. Although the previously developed STG is considered as a promising material and structure to be used as a flow distributor in polymer electrolyte membrane fuel cell (PEMFC), the STG flow distributor should be advanced in the aspect of conductivity to achieve higher performance. Herein, the conductivity of STG is improved via the thermal annealing process and the advanced STG is applied in PEMFC as a flow distributor to enhance the performance of the single-cell system. Single cell constructed with the thermally annealed STG exhibits a lowered charge and ohmic resistance, which leads to the performance enhancement. These results imply that direct coating of the advanced STG can be one of the alternatives of the complex and high-cost process of graphene coating to the porous metal foam through chemical vapor deposition (CVD).

Nonlinear Stability of Higher-Order Porous Metal Foam Curved Panels with Stiffeners

Nonlinear Stability of Higher-Order Porous Metal Foam Curved Panels with Stiffeners

Experimental study on flow boiling heat transfer characteristics of multi-channel modified filled foam metal small channel

This experiment reports the experimental study on the heat transfer performance of water in the flow-boiling heat transfer process of different modified foam metal-filled channels. In the experiment, the foam metal has subjected to surface hydrophobicity treatment, surface roughness modification treatment, and gradient pore density stacking treatment. The mass flow rate is 50–150 ml/min, and the heat flux is 15 kW/m2 – 25 kW/m2. The pore density of foam metal is 20 PPI, 50 PPI, and 110 PPI. A high-speed camera, micro camera, and electron microscope are used to record and observe the internal flow of the channel, the results after surface treatment, and the related reaction mechanism. The experiment uses different modifications as the basis for grouping and uses heat flux and mass flow rate as variables to perform multiple sets of orthogonal experiments. At the same time, the prediction model of matching heat transfer coefficient and the correlation of pressure drop gradient are proposed. Construct a comprehensive evaluation index of heat exchange of porous foam metal, which is evaluating the heat exchange performance of foam metal that matches the change of resistance.

3D porous nickel metal foam/polyaniline heterostructure with excellent electromagnetic interference shielding capability and superior absorption based on pre-constructed macroscopic conductive framework

The integration of dielectric and magnetic components is a promising strategy for fabricating electromagnetic interference shielding materials with peculiar characteristics. To further promote the shielding capability while still maintaining the high absorption performance, rational and meticulous structural design is urgently required for their practical application as advanced shielding materials. In this work, a highly porous nickel metal foam (NF) with the macroscopic pre-constructed conductive framework is selected as the substrate. Then, the polyaniline (PANI) coating layer is successfully intertwined on NF by a facile in-situ polymerization technology. Finally, the NF/PANI composite foam (NPF) with a unique three-dimensional (3D) porous heterostructure is created. Although the thickness is only increased by 2.7% of the pristine NF, the shielding effectiveness of NPF heterostructure is significantly improved, even reaching 93.8 dB (~99.99999996% radiation can be shielded). In particular, NPF possesses superior characteristics of absorption loss per unit thickness (147.64 dB/mm) among previously reported shielding materials. Such extraordinary performance could be ascribed to the 3D porous heterostructure, the presence of abundant interfaces, and dielectric-magnetic integration in NPF. These characteristics dramatically improve the interfacial polarization, dielectric polarization, dipole relaxation, attenuation constant, and multiple reflection. Both power balance analysis and the comparison between the absorption and reflection behaviors suggest that absorption dominates the shielding mechanism. The excellent comprehensive shielding capability endows such heterostructure with great application prospects in electronic devices. Furthermore, a prototype for achieving high-performance shielding materials based on 3D porous heterostructure is also provided.

A porous edge on turbine blades and aircraft wings reduces noise production

Replacing the outer 20% of an airfoil with a porous metal foam can reduce its noise by up to 7 decibels.

Nonlinear dynamic responses of sandwich functionally graded porous cylindrical shells embedded in elastic media under 1:1 internal resonance

In this article, the nonlinear dynamic responses of sandwich functionally graded (FG) porous cylindrical shell embedded in elastic media are investigated. The shell studied here consists of three layers, of which the outer and inner skins are made of solid metal, while the core is FG porous metal foam. Partial differential equations are derived by utilizing the improved Donnell’s nonlinear shell theory and Hamilton’s principle. Afterwards, the Galerkin method is used to transform the governing equations into nonlinear ordinary differential equations, and an approximate analytical solution is obtained by using the multiple scales method. The effects of various system parameters, specifically, the radial load, core thickness, foam type, foam coefficient, structure damping, and Winkler-Pasternak foundation parameters on nonlinear internal resonance of the sandwich FG porous thin shells are evaluated.

Special review: Mechanical investigation on failure modes of reticular porous metal foams under different loadings in engineering applications

PurposeThe purpose of this paper is to provide a summarization and review of the present author's main investigations on failure modes of reticular metal foams under different loadings in engineering applications.Design/methodology/approachWith the octahedral structure model proposed by the present authors themselves, the fundamentally mechanical relations have been systematically studied for reticular metal foams with open cells in their previous works. On this basis, such model theory is continually used to investigate the failure mode of this kind of porous materials under compression, bending, torsion and shearing, which are common loading forms in engineering applications.FindingsThe pore-strut of metal foams under different compressive loadings will fail in the tensile breaking mode when it is brittle. While it is ductile, it will tend to the shearing failure mode when the shearing strength is half or nearly half of the tensile strength for the corresponding dense material and to the tensile breaking mode when the shearing strength is higher than half of the tensile strength to a certain value. The failure modes of such porous materials under bending, torsional and shearing loads are also similarly related to their material species.Originality/valueThis paper presents a distinctive method to conveniently analyze and estimate the failure mode of metal foams under different loadings in engineering applications.

Vibration analysis of porous metal foam truncated conical shells with general boundary conditions using GDQ

Present work investigates the natural vibration characteristics of the porous metal foam truncated conical shells with the two interesting elastic restrained boundaries by using the generalized differential quadrature (GDQ) method. There are three types of porosity distribution being applied to do the vibration analysis (uniform distribution, nonuniform distribution and nonuniform asymmetric distribution along the thickness direction). In the light of the first order shear deformation theory (FSDT), the theoretical formulations are derived employing Hamilton principle. Two interesting elastic constraint boundary conditions are realized by employing the uniformly distributing artificial springs. The mode shapes and the natural frequencies of the system are determined. The convergence and a larger number of validation investigations are performed by the contrast researches of the present numerical results with those obtained from other literatures for truncate conical shell with C–C, S-S, S-C, S-C, C-S, C-F, F-C, F-S and F-F boundary conditions, respectively. The effects of the porosity, pore distribution characteristic, geometry, boundary conditions of the conical shell and elastic restraint stiffness are studied comprehensively.

Benchmarking of oxygen evolution catalysts on porous nickel supports

Summary Active and inexpensive oxygen evolution reaction (OER) electrocatalysts are needed for energy-efficient electrolysis applications. Objective comparison between OER catalysts has been blurred by the use of different supports and methods to evaluate performance. Here, we selected nine highly active transition-metal-based catalysts and described their synthesis, using a porous nickel foam and a new Ni-based dendritic material as the supports. We designed a standardized protocol to characterize and compare the catalysts in terms of structure, activity, density of active sites, and stability. NiFeSe- and CoFeSe-derived oxides showed the highest activities on our dendritic support, with low overpotentials of η100 ≈ 247 mV at 100 mA cm–2 in 1 M KOH. Stability evaluation showed no surface leaching for 8 h of electrolysis. This work highlights the most active anode materials and provides an easy way to increase the geometric current density of a catalyst by tuning the porosity of its support.

Thermal and electrical efficiencies enhancement of a solar photovoltaic-thermal/air system (PVT/air) using metal foams

Photovoltaic-thermal (PVT) collectors, are useful systems to absorb solar energy and convert that to electrical and thermal energy. However, to make the best out of solar irradiation, it is vital to improve the thermal and energy efficiencies of such systems. Porous metal foams are suggested to be utilized in the present study for cooling of the PV cells and increase the thermal and electrical efficiencies. Moreover, the effects of various parameters, such as porous layer thickness, solar heat flux, and Reynolds number on these efficiencies are investigated numerically. Results mainly focus on the effects of the porous media on both thermodynamic and hydrodynamic characteristics of the system, i.e., velocity profiles and the pressure drop. The results indicated that the usage of porous media can improve both efficiencies (between 3 and 4% for the electrical and between 10 and 40% for the thermal efficiency) with a subsequent pressure loss. But for cases with a thickness of more than half of the channel height, it has a negative effect. In the best condition, Rp=0.5, the overall efficiency reaches up to 95%, however, in this case, the pressure drop rises considerably (up to 600 Pa), which causes destructive effects on the system and imposes additional costs.

Scale-dependent nonlocal strain gradient isogeometric analysis of metal foam nanoscale plates with various porosity distributions

A scale-dependent nonlocal strain gradient isogeometric model of metal foam nanoscale plates with various porosity distributions is proposed. Three porosity distributions through the plate thickness including uniform, symmetric and asymmetric distributions are considered. The present model is efficient to capture both nonlocal and strain gradient effects in nanoplates. The strain–displacement relations are assumed to be derived from the higher-order shear deformation plate theory. Achieved relations will be then incorporated with the nonlocal strain gradient theory (NSGT) to reach deflections of metal foam nanoplates by using isogeometric analysis (IGA). Thanks to higher-order derivatives and continuity of NURBS basic functions, the IGA fulfills the weak form of nanoplates which requires at least the third-order derivatives in approximate formulations. The effects of different parameters including porosity distribution, porosity coefficient, length-to-thickness ratios, boundary condition, nonlocal parameter and length scale parameter on static and dynamic deflections of metal foam nanoplate are investigated. The reported results indicate that the mechanisms of stiffness-softening and stiffness-hardening mechanisms are pointed out in the present model. Also, a rise of porosity coefficient leads to a decrease of the plate stiffness, and a symmetrically porous metal foam is generally used to manufacture the nanoplate.