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Heterostructured design and microcrack management mitigate the strength-ductility dilemma in metallic materials. Here, we demonstrate a simultaneous enhancement of strength and ductility in graphene-decorated bimodal pure nickel, achieving a strength increase to 1 GPa and an 18% improvement in elongation by designing heterostructure with graphene, metal powders, and metal foams. The results show that grain refinement, hetero-deformation-induced hardening, and activated stacking faults mainly cause the strength-ductility synergy. Additionally, while dispersed microcracks nucleate within the fine grain zones, their propagation is constrained by the coarse grain zones. This study provides new insights into improving the strength-ductility combination in metallic materials. [ABSTRACT FROM AUTHOR]

The study investigated the deflagration and detonation suppression effect by different thicknesses of metal foam. The results show that the gas explosion suppression effect of metal foam is related to the explosion stage and the metal foam thickness. In the deflagration stage, the flame could be quenched by 10 mm, 20 mm, and 30 mm thick metal foam. In the flame acceleration stage, the flame can only be quenched by the 30 mm thick metal foam. In the detonation stage, detonation could be completely quenched by 20 mm or 30 mm thick metal foam. Ten-millimeter-thick metal foam could make detonation stage convert into deflagration stage and overpressure decreases obviously. Different propagation mechanisms of deflagration and detonation lead to different suppression effects of foam metal. [ABSTRACT FROM AUTHOR]

AbstractThis study examines active vibration control (AVC) in a truncated conical shell composed of metal foam reinforced with agglomerated graphene nanoplatelets and integrated with piezoelectric layers functioning as sensors and actuators. Both complete and partial agglomeration states are considered based on the Eshelby–Mori–Tanaka approach, and the mechanical properties of the porous core are characterized using a closed-cell metal foam model. The governing equations of motion are derived using Hamilton’s principle, based on the two-dimensional axisymmetric elasticity theory, and solved through the finite element method coupled with the Newmark method. Vibration mitigation is achieved using a fractional-order fuzzy proportional–integral–derivative (PID) controller. A comprehensive parametric study is conducted, examining the effects of geometric dimensions, various boundary conditions, reinforcement parameters (including weight fraction, distribution patterns, and agglomeration parameters), and porosity parameters (including pore size, and porosity pattern) on the vibration properties of the shell. Numerical simulations are performed to assess the effectiveness of the proposed AVC system in reducing structural vibrations compared to a constant velocity feedback control approach. The velocity feedback controller reduced central deflection from 12.65 to 5.089 μm, while a fractional-order fuzzy PID controller further improved it to 2.348 μm, representing a 53.86% enhancement over the velocity feedback controller. [ABSTRACT FROM AUTHOR]

Lately, metal foams have been widely used in various engineering structures due to their exceptional mechanical properties, including their lightweight. However, scientists have proposed adding nano-fillers like graphene nanoplatelets (GNPs) to overcome the issue of low stiffness caused by increased porosity. Hence, aerodynamic stability and vibrational behaviors of nanocomposite metal foams (NCMF)-reinforced GNPs sector microplate with piezoelectric/metallic face sheets are provided in this work. The microstructure is sited on Kerr elastic substrate and also is in a hygro-thermo-electrical media, subjected to supersonic flow based on first-order piston's theory (FPT). Gaussian random field (GRF), Halpin-Tsai, and extended rule of mixture (ERM) in conjunction with Gurtin-Morduch, modified strain gradient theories, and Hamilton's principle are used to derive the governing equations and linked boundary conditions. Generalized differential quadrature (GDQ) scheme is chosen to attain the results. By validating the results' precision, the effects of different parameters on the natural frequencies (NFs) and critical aerodynamic pressures (CAPs) are observed. It is perceived that adding GNPs enhances both NFs and CAPs significantly, and increasing porosity up to seventy percent, leads the results to drop. Various industries use simpler models to evaluate the microstructure, therefore the present model can pave the way for future uses and push the boundaries of knowledge in these industries based on the results it produces. [ABSTRACT FROM AUTHOR]

The effect of the metal foam thickness on the conduction and convection heat transfer for a metal foam flat plate impinged by a circular air jet is investigated. The IR thermography and thin-metal foil technique are used for the measurement of local heat transfer. An open-cell aluminum metal foam is used for the metal foam flat plate. A 3D-printed resin foam and detached metal foam flat plate are used for the appreciation of the conduction and convection heat transfer. The varying parameters are the thickness of the foam, Reynolds number, and the nozzle exit to plate distance. The presence of the metal foam offers a conduction effect. This predominates over the attenuation in the convective heat transfer by foam due to additional hydraulic resistance. The additional hydraulic resistance offered by the porous foam increases with the increase in the foam thickness. The heat transfer of a porous foamed flat plate decreases with the increase in the foam thickness. The local Nusselt number of the resin foam and detached foam flat plate is almost the same. The conduction effect and attenuation in the convection heat transfer of a metal foam flat plate are quantified by attenuation and enhancement factors. The overall augmentation offered by 4, 8, and 12 mm thick metal foam flat plates is 1.71, 1.42, and 1.43 times compared to the smooth flat plate case, respectively. Hence, it is advisable to use a metal foam flat plate with 4-mm-thick metal foam under circular air jet impingement. [ABSTRACT FROM AUTHOR]

This study investigates tube-in-tube heat exchanger performance under steady-state conditions, examining co-current and counter-current flows. It explores various configurations, including metal foam enhancements, to optimize heat transfer efficiency and minimize pressure drop. Driven by the potential of metal foam to enhance heat transfer, the study aims to demonstrate significant improvements in thermal performance compared to conventional designs. Experimental methods involve testing four configurations with Nickel foam (10 PPI, 0.90 porosity) inserts, evaluating temperatures and pressure drops across flow rates of 25 to 50 LPH. Hot water at 65°C flows in the annulus, while normal water at 31°C flows in the outer annulus. Results show metal foam’s substantial enhancement in heat transfer, with counter-current metal foam configurations achieving up to 3.71 times greater efficiency than parallel flow setups. Moreover, comprehensive performance evaluation reveals that the counter-flow heat exchanger with metal foam is 2.03 times more efficient than the conventional co-current flow without metal foam. Conclusions highlight metal foam’s effectiveness in improving heat transfer performance and optimizing thermal systems through systematic parameter optimization using response surface methodology. [ABSTRACT FROM AUTHOR]

This research investigates the use of metal foam inserts to enhance the thermal-hydraulic performance of double-tube heat exchangers, relevant for energy-efficient systems such as solar flat plate collectors. Motivated by the need for improved heat transfer efficiency, this study hypothesizes that metal foam integration can significantly boost performance. Through systematic experimental study, the impact of metal foam inserts on heat transfer and pressure drop characteristics is comprehensively evaluated across various configurations, spanning horizontal and vertical orientations. Experimental evaluations were conducted on four configurations, including both conventional and metal foam-integrated heat exchangers in horizontal and vertical orientations, using water as the working fluid and Nickel metal foam with 0.9 porosity and 10 PPI in the annular space. The findings highlight significant enhancements in heat transfer performance with metal foam integration across both horizontal and vertical heat exchanger configurations compared to conventional counterparts, particularly showcasing superior effectiveness and efficiency in the horizontal configuration. Results show that metal foam integration substantially enhances heat transfer, with horizontal configurations exhibiting a 14.56% higher heat transfer coefficient than vertical ones. Additionally, the comprehensive performance index improved by 1.17 times, indicating a better balance between heat transfer enhancement and pressure loss. These findings were validated against established correlations from the literature, confirming the superior effectiveness of horizontal metal foam heat exchangers. [ABSTRACT FROM AUTHOR]

Under lateral load, this article aims to discuss the large deflection and yield criterion of Y-shape sandwich beams filled with foam. Considering the effect of metal foam strength, a yield criterion of Y-shape sandwich structure filled with foam is proposed. An analytical solution for large deflection of clamped foam-filled Y-shape sandwich beam under lateral load is derived using yield criterion, considering the interaction between stretching and bending due to large deflection. The corresponding numerical calculation of sandwich beams under lateral load is carried out. It is shown that the theoretical results are in good agreement with the calculated results. The effects of metal foam strength, face-sheet thickness and punch width on large deflection are studied in detail. The results show that the analytical model could predict the large deflection of foam-filled Y-shaped sandwich beam under lateral load really well. [ABSTRACT FROM AUTHOR]

The influence of metal foam thickness on the convection and conduction heat transfer is studied by measuring the local heat transfer of a smooth flat plate, attached and detached metal foamed flat plate under multiple jet impingement conditions. 27 jets of 3 mm diameter are introduced from a jet plate. These jets impinge on a thin stainless steel foil that serves as a targeted plate. The pitch of the jets is 4d in both the spanwise and streamwise directions. The spent fluid is exiting in all directions. The influence of metal foam thickness is investigated for an open-cell aluminum foam with 4, 8, and 12 mm thickness. The porosity of aluminum metal foam is 0.92. The pore density (pores per inch) is 20 PPI. The local heat transfer is measured using infrared thermography and a thin metal foil technique. A smooth flat plate impinged by multiple jets serves as a reference case. The evaluation of the convection and conduction heat transfer offered by the metal foamed flat plate is obtained with the help of the detached foam configuration. The jet diameter-based Reynolds number ranges from 2500 to 15000. The range of the jet to plate spacing covered is 3d to 6d. Depending on the metal foam thickness, the metal foamed flat plate offers additional hydraulic resistance to the jet flow and conduction effect. The additional hydraulic resistance attenuates the convective heat transfer and is represented by attenuation factor (α). For metal foam having 4, 8, and 12 mm thickness, the attenuation factor is around 1.11, 0.99, and 0.64, respectively. The conduction effect offered by metal foam is responsible for the enhancement of the heat transfer. The conduction effect is represented as an enhancement factor (E). For metal foam having 4, 8, and 12 mm thickness, the enhancement factor is around 1.51, 1.58, and 2.32, respectively. The conduction effect presented in the metal foamed flat plate dominates over the attenuation in the convective heat transfer. The overall enhancement offered by 4, 8, and 12 mm metal foamed flat plate is around 1.67, 1.56, and 1.48, respectively. [ABSTRACT FROM AUTHOR]

Composite metal foams (CMFs) are a new class of closed-cell porous materials that can be produced by distributing metallic spheres in a metallic matrix. CMFs could offer better mechanical performance in comparison to the conventional metal foams due to the uniform shape and even distribution of voids. To evaluate elastic properties of CMFs, the conventional theoretical approaches for periodic models are not good candidates due to the random distribution of voids in these materials. Thus, in this research, first, a three-dimensional model is developed based on the Lubachevsky and Stillinger (LS) approach, which is then used for the FE analysis. Using homogenization technique, the elastic properties of the CMFs are evaluated focusing here on elastic modulus and Poisson's ratio. Comparing results against experimental results shows a very good agreement. In this paper, for the first time, effects of geometrical and material parameters such as thickness of the spheres, microporosity in the wall of spheres and matrix, matrix materials, and diameter of the spheres on the elastic properties of CMFs are examined. It is observed that the microporosity in the matrix has higher effect on the elastic modulus of the CMFs than the microporosity in the wall of the spherical particles. [ABSTRACT FROM AUTHOR]

Nonlinear bending of functionally graded metal/graphene (FGMG) sandwich rectangular plate with metal foam core resting on nonlinear elastic foundations is elucidated in this article. A new shear deformation plate theory is presented to formulate the displacement field. The nonlinear partial differential equations considering the small size effect are established via the principle of virtual work. The nonlinearity is considered by using Von Karman's strain-displacement relations. While, the size effect is captured by employing the modified couple stress theory. The upper and lower layers are made of aluminum as a matrix that reinforced with graphene platelets (GPLs). The GPLs are functionally graded through the thickness of the face layers according to a new cosine rule. Moreover, the metal foam core is also made of aluminum containing porosities that uniformly distributed or functionally graded through the core thickness. The governing equations are solved based on the Galerkin and Newton's methods. The obtained results are examined by introducing some comparison examples. In addition, several parametric examples are discussed including the effects of the porosity type, GPLs distribution type, core-to-face thickness, elastic foundation stiffness, side-to-thickness ratio, plate aspect ratio and material length scale parameter on the nonlinear deflection and stresses of FGMG sandwich plate with metal foam core. [ABSTRACT FROM AUTHOR]

AbstractThe variable thickness function is innovatively added. The carbon fiber layer and the porous foam metal aluminum, are selected to composite the composition of a variable thickness cantilevered trapezoidal plate for modeling and free vibration analysis. Hamilton’s principle is used to develop the motion control equation of the trapezoidal plate with variable thickness cantilevered sandwich, and Galerkin’s approach is used to determine the inherent frequency of the system. The research employs suitable analytical methods to solve them, and analyzes the outcomes to uncover the effects of geometric parameters, material properties, and thickness variations on the structure. [ABSTRACT FROM AUTHOR]

AbstractA novel porous multi-jet impingement cooling technology since the current conventional cooling technologies are insufficient for thermal engineering devices. This innovative numerical study explores the effect of various metal foam sizes (h/H), jet numbers (n) and wavy jet target plates (C) on the hydrothermal performance and thermodynamical performance at varying Reynolds numbers (Re). The novel results of multi-objective optimum design are a unique aspect of this work by combining the results of RSM with CFD, where low porosity (ε = 0.1), low applied heat flux (Q = 100 × 103 W/m2) and low location jet ratio (LRVin = 0.26) were achieved the aim of the optimum hydrothermal performance (NumP/NumS = 25-30 times and Tb Reduction% = 83.5%-89.5%) and the thermodynamical performance (EG Reduction% = 93%-96% and CoPCarnot = 2.3-6.5 times). Thus, a valuable procedure for the optimal design of the hydrothermal and thermodynamical performance for porous multi-jet impingement cooling is proposed. [ABSTRACT FROM AUTHOR]

The application of natural convection heat transfer within a novel Ϻ-shaped cabinet filled with single-phase pure water/metal foam is investigated numerically. Natural convection is modeled throughout the porous zone using the Local-Thermal-Equilibrium mode and Darcy-Forchheimer-Brinkman law. A novel Ϻ-shaped cabinet with varies Ϻ ratio (0 ≤ Ϻ ≤ 0.8) and temperature difference (10 K ≤ ΔT ≤ 40 K) is applied at a constant porosity of ε = 0.85. Furthermore, the current research is conducted to analyze the response surface methodology (RSM) accompanied by a computational simulation for optimizing the multi-objective function of the M-shaped cabinet in terms of two computed responses: maximizing the Nusselt number ratio (NNR) and minimizing the entropy generation ratio (EGR). The optimization study considers the various pore per inch (10 ≤ PPI ≤ 50), Darcy number (10-9 ≤ Da ≤ 10-1) and uniform magnetic fields (0 ≤ Ha ≤ 100). The results showed that the optimum working conditions consistent with the desired aim are achieved in the maximization of NNR by nearly 20.84 times and the minimization of EGR of 0.895 obtained at Ha = 100, Da = 10-1 and PPI = 30. Thus, the current investigation is a unique application study of CFD and RSM which provides a helpful reference for the optimum design cooling efficiency and entropy performance of a novel Ϻ-shaped cabinet. [ABSTRACT FROM AUTHOR]

An enhanced flow field significantly improves reactant transfer and proton exchange membrane fuel cells (PEMFCs) performance. Metal foams with high porosity and electrical conductivity are promising flow field structures. This study aims to investigate the effect of metal foam porosity and pore density on PEMFC performance. A three-dimensional multi-physics PEMFC model with holomorphic microscopic metal foam (HMMF) as a cathode flow field was established using computational fluid dynamics (CFD). The HMMF with high porosity as a cathode flow field can enhance reactant transfer and accelerate the electrochemical reaction process. It is also observed that increasing the porosity of HMMF can significantly improve the peak power and current density of PEMFC. The simulation results show that the current density gains an increase of 15.3% by raising the porosity from 0.8 to 0.96. Besides, the current density increases by 4.3% when the pore density is 95 PPI compared to 21 PPI. Moreover, the effects of cathode stoichiometry ratios on oxygen molar fraction and polarization curves were studied to obtain better operating conditions for the HMMF flow field. The results indicate that increasing the cathode stoichiometry ratio can effectively enhance oxygen concentration. And the increase of the cathode stoichiometry ratio from 1.5 to 4.0 results in a 45.5% increment of current density. [ABSTRACT FROM AUTHOR]

The present study investigates the aeroelastic flutter characteristics of the graphene platelets (GPL) reinforced metal foam beam. Closed-cell metal foam beams having graded distribution of pores and functionally graded reinforcement of GPLs are considered in this study. The closed-cell metal foam model has been used for deriving the mechanical properties of the foam matrix, which makes provision for determining the relation between the co-efficient of porosity and the co-efficient of density. Modified Halpin-Tsai micromechanics is used to obtain the effective Young's modulus of the GPLs reinforced composite beam, Density and Poisson's ratio are calculated with the help of the rule of mixture. The Hamilton's principle together with the Ritz method, employing the first-order piston theory gives the governing equations of motion for aeroelastic flutter characteristics of the beam for different end conditions. Juxtaposition of dimensionless natural frequencies with the results previously published by others is executed for validating the correctness of the approach followed in the present model. A study of various parameters has been executed, and the results in tables and graphs present the influence of porosity as well as GPLs reinforcement, different boundary conditions and thermal loading on aeroelastic flutter characteristics of the FG-GPL reinforced metal foam beam. [ABSTRACT FROM AUTHOR]

The present paper is mainly focused on analyzing the flexural wave dispersion of imperfect Ti-6Al-4V foam circular cylindrical shells in a thermal environment. The pores were supposed to be distributed across the thickness (z-direction) in the form of three different patterns as follows: symmetric porosity distribution (SPD), asymmetric porosity distribution (ASPD) and uniform porosity distribution (UPD). Besides, various kinds of temperature variations, including sinusoidal, linear and uniform temperature variations, were studied. The strain-displacement relationship of the shell was derived based on the first-order shear deformable theory (FSDT) of shells. Hamilton's principle was also applied to obtain the governing equations of metal foam shells which were then solved using an analytical method. Finally, influences of different parameters including circumferential wave number, different kinds of temperature variation, temperature change, radius to thickness ratio $ {R / h} $ R / h , types of porosity distribution across the thickness, porosity coefficient and mode number on the variations of phase velocity and wave frequency were investigated and the results were illustrated and discussed. [ABSTRACT FROM AUTHOR]

In this paper, the plastic behavior of metal sandwich beams with foam-filled sinusoidal corrugation is studied theoretically and numerically. The yield criterion of foam-filled sinusoidal corrugation sandwich cross-section is established, considering the effects of metal foam strength and sinusoidal corrugation strength. Based on the yield criterion, an analytical model for the plastic behavior of fully clamped foam-filled sinusoidal corrugation sandwich beams under transverse loading is developed, considering the interaction of axial force and bending moment. Finite element calculations are carried out to verify the analytical model. The influences of geometrical and material parameters on the load-carrying capacity and energy absorption of foam-filled sinusoidal corrugation sandwich beams are discussed. The results show that, with the increase of foam strength, face-sheet thickness, sinusoidal corrugation strength, sinusoidal corrugation sheet thickness, sinusoidal amplitude, sinusoidal half wavelength and punch width, the load-carrying capacity and energy absorption of foam-filled sinusoidal corrugation sandwich beams increase. In addition, when the loading position moves from the midspan to the clamped ends, the load and absorbed energy for the same deflection increase obviously. [ABSTRACT FROM AUTHOR]

The purpose of present investigation is to study propagation of flexural wave in porous metal foam beams resting on Winkler–Pasternak foundation based upon refined higher-order shear deformable beam theory. Moreover, different types of porosity distribution through the thickness direction are probed namely; uniform, symmetric and asymmetric. The Hamiltonian approach is implemented to catch motion equations of porous metal foam beams. Then, the obtained governing equations of porous metal foam are solved analytically. The influences of different parameters such as various types of porosity distribution, porosity coefficient, slenderness ratio, wave number and elastic foundation coefficients on the variation of wave frequency, escape frequency and phase velocity are covered and presented within the framework of a group of figures which can be observed in detail. [ABSTRACT FROM AUTHOR]

This work introduces a new approach of analyzing convective heat transfer in porous medium by considering the foam structure as a type of fin. It provides the resulting heat transfer characteristics for the design of a longitudinally flowed tube bundle reformer used for the Micro Gas Turbine Solid Oxide Fuel Cell (MGT-SOFC) hybrid process. Owing to a limited experimental database available in literature for the above-mentioned situation, a physical model is initially introduced for a channel flow configuration between two large flat plates using a commercial PDE solver. This model is then validated with experimental results available in literature. A comparison with theoretical solutions is also conducted. Later, this model is modified/adapted for a pipe flow configuration. The physical model for a channel with representative cross-section shape of a longitudinally flowed tube bundle is more complex and is therefore built in a commercial CFD-Solver. A comparative study of the heat transfer behavior in channels of different cross-sections is performed based on a new dimensionless correlation, whose physical coherence with fin efficiency is explained and mathematically proved. The applicability of the heat transfer correlation from one cross-sectional shape to the other are discussed. The proposed new treatment of the porous medium as a fin structure considerably simplifies the heat transfer analysis in porous medium by the clear physical meaning behind fin efficiency and Biot number. This relationship contributes to a better understanding of the heat heat transfer characteristics in porous media in contrast to the correlation between Nusselt number and Reynolds number. Furthermore, this correlation enables a direct comparison between foam structures of different parameters because the fin efficiency is always between 0 and 1. The strong physical background of new correlations also enhances the reliability and plausibility at characterizing and designing the metal foam for heat transfer enhancement. [ABSTRACT FROM AUTHOR]

The objective of this contribution is twofold. First, a multi-objective hydrothermal optimization is performed to determine the optimum nanoparticles (NPs) shape in nanofluid flow through an annular pipe having metal foam fins, in the forced convection regime. Second, the suitability of the performance evaluation criterion (PEC), as a common method to analyze the hydrothermal performance of thermal systems, is examined by comparing the outcomes of the multi-objective optimization method with those obtained by maximizing PEC. It is found that, depending on the value of the Reynolds number, the cylindrical-shaped NPs or the blade-shaped NPs exhibit the highest heat transfer performance. The lowest value of the required pumping power belongs to the spherical-shaped NPs. The results indicate that PEC attains its maximum value in the spherical-shaped NPs, the NPs fraction of 0.01, the nondimensional fin length of 0.4, the Darcy number of 0.01, and the medium porosity of 0.75. However, the multiobjective algorithm provides several optimum circumstances, each for a certain criterion indicating the suitability of this strategy for hydrothermal performance optimization of the system. [ABSTRACT FROM AUTHOR]

Metal foam (MF) and nano-sized particles (NSP) are regarded as patent tools for enhancing the thermal performance of phase change materials (PCM)-based latent thermal energy storage unit (LTES), but data on this issue for large-scale installations is very scarce. This study provides a comprehensive computational analysis of the effects of MF and NSP on the solidification process of RT82 paraffin (PCM matrix) in a large-scale shell-and-tube latent thermal energy storage unit (of heat exchanger form). The developed 2D transient model developed on Ansys Fluent 15.0 software was initially verified using available literature experimental data. The process performance was tested for 5% Al2O3 nanoparticles and various MFs [i.e. aluminum (Al), copper (Cu), nickel (Ni) and titanium (Ti)] with varied porosity (96–100%). The computed mean and spatial temperature and solidified degree of the PCM block showed a drastic acceleration of the solidification process with the b MF technique rather than with the nanoparticles system. The solidification performance increased in the direction of MF-thermal conductivity increase, i.e. Cu > Al > Ni > Ti, and material porosity decrease. These conditions allow rapid HTF heat recovery and then stocking considerable thermal energy. However, the MF porosity could not decrease below 95% to avoid a huge loss of material storage (PCM), thereby diminishing the thermal storage capacity of the LTES unit. [ABSTRACT FROM AUTHOR]

The melting/solidification of PCM "phase change material" (C19-C20) and cooling/heating of air (HTF "heat transfer fluid") have been analyzed under the variation of temperature, by an increment of 2 K, on the external side of the heat exchanger (Tw). Aluminum foam (20%, v/v) was used to improve the thermal conductivity of the adopted PCM (C19-C20). Eight cases were investigated during the melting (Tw: from 310 to 324 K) and solidification (Tw: from 284 to 298 K) periods of PCM (C19-C20). It has been shown that the melting/freezing processes of PCM were enhanced by increasing (from 310 to 324 K)/decreasing (from 298 to 284 K) the temperature on the external side of the heat exchanger. On the other side, the cooling/heating mechanisms of air were found to be less dependent on the temperature of the external side of the thermal unit. Additionally, it was observed that the decreasing/increasing of air (HTF) temperature were more rapid than the fusion/freezing processes of PCM. Based on the mass fraction profiles of the liquid PCM, it was retrieved that the fusion and solidification mechanisms proceeded in a quasi-homogeneous way as the melting or freezing of PCM were observed to take place gradually all around the center of the heat exchanger. Compared to the fusion process of PCM, its freezing regime was observed to be slower. [ABSTRACT FROM AUTHOR]

We show a way to solve the problems of hydrodynamics and heat transfer in helical medium flow channels in the helical coordinate system. Specifically, such problems are solved for the buoyant liquid metal flow in a heated helical fin ring-shaped channel. The problems are related to heat transfer in the flow process over the fuel pin located within the fuel bundle finned in the liquid metal nuclear reactor core. The article shows the tensor analysis derivation of the mass-, momentum-, and energy-conservation equations as applied to a liquid metal medium in the helical coordinate system. We assume as the basis the well-known equations for a cylindrical system proposed to be added, with extra terms arising in the process of transition to the helical coordinate system. In line with the proposed technique, numerical computation of the velocity, pressure, and temperature profiles in the process of turbulent liquid flow in a helical fin ring-shaped channel was performed. Two computation cases are compared: with straight and twisted (helical) fins. Examples of the computation data show the measurable effect of a twisted fin upon flow and heat transfer parameters. The available gap between the fin and the external tube enhances the vorticity effect. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) with coordinatively unsaturated open metal sites (OMSs) are promising sorbent materials in atmospheric water harvesting (AWH) systems at low relative humidity (RH) due to their strong interactions with water molecules. However, accurate computational modelling of water adsorption in those materials are challenging, as standard force fields (FFs) based on the 12-6 Lennard–Jones (L–J) potential cannot properly describe the water–OMS interactions. In biomolecular simulations, the 12-6-4 L–J potential has been successfully used to model metal ion–water interactions in which the extra 1/r4-term is for charge-induced dipole electrostatics. In this work, we adopted this strategy and used the 12-6-4 L–J potential to model water–OMS interactions in MOFs for low RH AWH applications. Without any modifications, the parameters used for aqueous metal ions were able to greatly improve the accuracy in predicting water adsorption isotherms in MOF-74, which highlights the simplicity and transferability of this method. [ABSTRACT FROM AUTHOR]

Using metal foams mitigates the low thermal conductivity of phase change materials (PCMs) in latent heat thermal energy storage (LHTES). However, the heat transfer within PCMs is not uniform due to natural convection. In the present study, the effect of the porosity distribution on the heat transfer performance of shell-and-tube thermal energy storage (TES) was analyzed. The results demonstrated that the melting rate and average heat transfer rate both were improved as the porosity gradient increased along positive y-direction. Compared with the uniform porosity (ε = 0.94), the average heat transfer rate was enhanced by 21.6% for ε = 0.94 + 0.267y during the melting process. For the porosity gradient increasing along outer radius direction, the heat transfer rate near the heating wall was improved, while the phase change process of PCM near the outer wall slowed down. The maximum of average heat transfer rate existed for ε = 0.88 + 0.6r. [ABSTRACT FROM AUTHOR]

This study reports a parametric numerical investigation to elucidate the thermal-hydraulic performance of metal foam for cooling applications. In this study, both spanwise and streamwise size of metal foams having high porosity value of ∼0.95 is varied, along with the solid-phase thermal conductivity and pore-density of metal foams, for both air and water as working fluid flowing at different Reynolds number. Thinner foams (in spanwise) and shorter foams (in streamwise) were found to have highest convective heat transfer coefficient at a certain pumping power, with water-based configurations yielding ∼10 times more heat dissipation at a certain pressure drop when compared to air-based configurations. [ABSTRACT FROM AUTHOR]

Porous materials have remarkable mechanical properties. With the development of methods to produce cellular structures such as additive manufacturing, the fabrication of metal foams with the desired geometry and properties has expanded greatly. Despite the existence of more than a 100 types of cellular structures, the behavior of many of them remains unknown. Therefore, the objective of this work is to get more insight into the influence of cell geometries on the compression characteristics of porous materials. Moreover, the influence of density on typical compressive properties of porous materials such as elastic modulus, yield stress, plateau stress, and energy absorption are studied in the present study. To this end, three different values of foam density for five-unit cell configurations including alternated cantitruncated cubic honeycomb (ACCH), cantellated cubic honeycomb (CCH), rectified cubic honeycomb (RCH), Kelvin (K), and Weaire-Phelan (WP) are considered. The results imply that, overall behavior of porous structures highly depends on individual cell deformation. Stress localization on the macro scale is a consequence of failure at the cell level. To validate numerical results, several experimental tests are carried out. Various unit cell configurations show a different level of influence on typical compressive properties. Therefore, the structures are divided into two groups in terms of elastic modulus: those that are stiff (ACCH, CCH, and RCH unit cell) and those that are compliant (K and WP unit cell). [ABSTRACT FROM AUTHOR]

Challenges exist in the applicability of thermoplastic foams as scaffolds for bone tissue engineering including mismatch of mechanical properties. Template assisted electrodeposition was carried out to fabricate hybrid polymeric-metallic foams. Compression test, cytotoxicity and biofunctionality evaluations was performed on polyurethane coated niobium foams to investigate the enhancement of desired properties. Results indicated that ultimate compressive strength of polyurethane foams improved due to the niobium coatings. Biocompatibility evaluations showed that the niobium coated foams were biocompatible. Bio-functionality evaluations showed that the coating of niobium on polyurethane decreases its ability to support osteoblastic cell attachment and proliferation. [ABSTRACT FROM AUTHOR]

Most of the studies investigated either charging or discharging process in a phase change material (PCM) based heat sink. In this paper, both melting and solidification of n-eicosane filled heat sink is studied numerically. The system filled only with PCM is unable to provide desired performance because of poor thermal conductivity of material. In order to enhance the response time, fins and foams are used in this study. Here, a PCM filled hybrid system of two cases is considered. For case 1, the heat sink with horizontal and vertical fins and for case 2, the heat sink with combination of horizontal fins and metal foams (aluminum) are employed. In case 1, no fin case is compared with rectangular fins and tapered fins. Results show that tapered fins are good for distribution of temperature within the system. In case 2, different filling heights such as 10 mm, 15 mm, and 20 mm with horizontal tapered fins are investigated. From the results, it is observed that the convection is delayed by increasing the filling heights. For solidification cases, 20 mm filling height foam performs better than all other cases. [ABSTRACT FROM AUTHOR]

Analysis of nonlinear vibration properties of stiffened toroidal convex/concave shells made of porous metal foam material in elastic medium has been performed in the present research. Metal foam is considered as porous material with uniform and nonuniform models. The governing equations of motion of eccentrically stiffened porous toroidal shell segments are derived based on the classical shell theory with the geometrical nonlinear in von Karman–Donnell sense and the smeared stiffeners technique. The nonlinear governing equations are solved with the use of Jacobi elliptic functions to obtain the exact frequency–amplitude curves of the geometrically nonlinear metal foam toroidal shell. Presented results demonstrate the significance of porosity distribution, geometric nonlinearity, foundation factors, stiffeners and curvature radius on vibration characteristics of porous toroidal convex/concave shells. [ABSTRACT FROM AUTHOR]

A numerical analysis aiming to investigate the influence of numerous parameters on the energy storage systems has been conducted. The system performance working with phase change materials (PCMs) is evaluated in terms of complete melting time and metal foam radial distance in annulus. A comprehensive transient analysis is presented to monitor the melting behavior of the integrated PCM in the presence of porous metal foam sleeves under constant volume at various locations as thermal conductivity enhancers (TCEs). Aluminum alloy T-6201 is used for the porous metallic foam, while paraffin is introduced as PCM. The porosity, pore size (PPI), various PCM materials, and porous distance from the heat sources were investigated. Results show that porous TCEs radial distance from the applied heat sources has a substantial effect and can lead to an improved rate of melting depending on the sleeve location. In addition, high thermal conductivity near the heat source suppresses the porous resistance to liquid PCM flow and thus natural convection. Results revealed that case B provides a uniform liquid PCM profile and heat distribution while case D has the highest melting during the initial stage and lower one at the final stages of melting. Pure PCM case imposed the least resistance but has the slowest melting time while a turning point in melting rate is noticed from case C. Eventually, results show that higher PPI materials have a similar melting pattern as a result of high thermal conductivity. [ABSTRACT FROM AUTHOR]

Electric vehicles with a pack of lithium-ion batteries (LIBs) are taking a significant place in the field of transportation. Since lithium-ion battery efficiency relies on battery pack temperature, the temperature of the battery pack must be maintained within the safe limits for proper working of the system. This paper proposes a novel experimental method to dissipate and maintain the thermal energy emitted by LIBs based on a nickel foam/paraffin composite and a composite of copper foam/paraffin for thermal management of Panasonic NCR 18650B cylindrical lithium-ion battery cells. The results indicate that the surface temperature of the battery is reduced by 30.95% by comparing with ambient air convection and 24% temperature reduction by comparing with PCM by the application of nickel foam at a 2C discharge rate. By using copper foam/paraffin composite 34% and 25% temperature reduction by comparing with ambient air convection and PCM (paraffin) accordingly was achieved at a 2C discharge rate. Additionally, the result of temperature uniformity on the thermal management of the battery pack was also studied. [ABSTRACT FROM AUTHOR]

The thermal and hydraulic properties of flow through metal foams have been further investigated, but knowledge of flow through the Metal foam is still limited. In this work, three samples of copper foams (10, 20, and 30 PPI) were carried out for experiments and numerical simulations to investigate airflow characters through a tunnel. A novel honeycomb-like equivalent model is proposed to predict the internal flow characteristics of foam metals. Compere with the numerical simulation of pressures drop and flow conditions of three types equivalent model (FCC, Ligament model, and Honeycomb geometry model) in commercial software FLUENT. The honeycomb-like equivalent model possesses excellent prediction accuracy of pressure at 20 PPI and the overall average error is 4.27%. The difference in velocity increase with the rising of inlet velocity and a decreasing tendency of difference in velocity with the increase of porosities on the two sides of the copper foam. [ABSTRACT FROM AUTHOR]

The adsorption of Na/Na+ and K/K+ on the three open metal site formate paddlewheels (PWs) of metal-organic frameworks with different metals from the first row of TM (Co-PW), the second row of TM (Mo-PW), and the third row of TM (Ir-PW) were examined to determine if they could be used in NIBs and KIBs. Na/Na+ and K/K+ adsorption energies were measured in the range of −203.5 to −42.1 kJ/mol and −208.4 to −43.7 kJ/mol, respectively. Co-PW cannot serve as a suitable example for NIBs and KIBs since atomic Na and K are both adsorbed more favourably than ionic ones. Ir-PW is suitable only for NIBs with a positive ΔEcell of −14.3 kJ/mol for Na/Na+ adsorption. Mo-PW is a potential candidate as anode material for both Na-ion batteries (NIBs) and K-ion batteries (KIBs) with Ecell of −91.0 and −34.8 kJ/mol with related Vcell of 1.97 and 0.75 V because both Na+ and K+ are much more feasible to adsorption on Mo-PW than Na and K. Although four atoms of Na and K with a theoretical capacity of 288.2 mAh/g toward sodium and potassium can be exothermally adsorbed on the Mo-PW, the ΔEcell and Vcell of the fourth K are close to zero. [ABSTRACT FROM AUTHOR]

Metallic foams are popular due to their high strength-to-weight ratio. Moreover, foams are excellent vibrations damper, which attracted attention of researchers. This study investigated the improvements in the characteristics of metal foams for the structural applications. The metal foams were fabricated by stir casting method using calcium carbonate (CaCO3) as foaming agent. The metallic foam generated are aluminium hybrid composite foam (AHCF) with densities varying between 0.88 and 1.14 g/cc. Developed AHCF was characterised for their physical and mechanical properties like density, porosity, three-point bending, compression and hardness followed by microstructural investigation. Results show that the percentage of the weight (wt.%) of the foaming agent plays a significant role in deciding the density, compressive strength, bending strength and the hardness of AHCF. The study reveals that compressive strength, flexural strength and the hardness of AHCFs increased with their density. AHCF exhibits lower density and higher specific strength when compared to aluminium (AA7075). [ABSTRACT FROM AUTHOR]

Due to its high heat transfer performance, the open-cell metal foam has a great potential of applications in heat exchanger industries. Based on the cell structure of the perforated metal foam, a simplified hexahedral structure model was proposed herein. The fluid flow in metal foams was simulated by computational fluid dynamics software. The accuracy of the model was verified by experiments. Based on the numerical simulation, heat transfer performance and the mechanism of enhanced heat transfer were investigated and discussed. The results show that the hexahedron model proposed in this article is feasible and accurate. The heat transfer and pressure drop properties of metal foams were numerically calculated and analyzed at the inlet air velocity of 1–5 m/s. At a certain PPI (pores per inch) and porosity, with the increase of Reynolds number Re, both the heat transfer coefficient h and pressure drop ΔP/L increase gradually. The comprehensive performance of convective heat transfer of metal foams with a lower PPI is relatively better. Increasing PPI or decreasing porosity is conducive to the destruction of the fluid boundary layer, enhancing the fluid disturbance, thus forming a vortex at the back of the skeleton and strengthening the heat transfer. [ABSTRACT FROM AUTHOR]

In this study, the effect of fiber angle alignment on the energy-absorbing behavior of 0°, 5° and 10° conical CFRP tubes was numerically investigated. Feedforward Neural Networks (FFNN) were used to determine the optimum fiber angle alignment for the highest absorbed energy (AE), crash force efficiency (CFE), and lowest peak force. In addition, 100, 400, 600, and 800 kg/m3 metallic foam filling was used to investigate the foam filling effect in tubes with an optimum fiber angle alignment. The results showed that the amount of absorbed energy can increase by up to 118% with optimum fiber alignment. [ABSTRACT FROM AUTHOR]

This work presents an approach to evaluate axially compressed metallic foams with the presence of holes on the structure further than foam voids. Adding holes, the total material weight is decreased but the stiffness is not linearly reduced. The stress–strain characterization is investigated and presented considering the number, size, and thickness of rectangular holes. The characterization uses representative volume elements to decompose the foam into fundamental portions. Symmetries, boundary conditions and homogenization principles are combined in a formulation in terms of parameters describing the holes, resulting in a parametric characterization. Examples are presented where the influence of holes is analyzed. [ABSTRACT FROM AUTHOR]

Appropriate arrangement of the fin structures in the evaporator and condenser not only enhances the heat transfer coefficient but also suppresses the increase of pressure drop. Due to this reason, a new method of using large-scale pin fins is explored to increase the heat transfer area and to modify the liquid film flow characteristics in the enhanced tubes. In the present study, four enhanced tubes and one plain tube were manufactured by selective laser melting. The working fluid is R407C and the enhanced tubes are eight short pin fins tube, five long pin fins tube, twisted pin fins tube and a tube filled with metallic foam. The results show that the shorter fin tube has the largest heat transfer coefficient for condensation at 3967 W/m2⋅K and the metallic foam tube demonstrates the largest heat transfer coefficient for boiling at 10606 W/m2⋅K. However, the shorter fins have the highest efficiency indices based on the heat transfer coefficient-pressure drop evaluation criterion and the heat transfer coefficient-area evaluation criterion. For condensation, the indices are 1.28 and 1.35, respectively. For boiling, the indices are 2.55 and 1.62, respectively. [ABSTRACT FROM AUTHOR]

This investigation deals with wave propagation analysis of porous metal foam resting on the Kerr substrate in the thermal environment within the framework of the refined higher-order plate theory. Different types of temperature rise are studied namely; uniform, linear and sinusoidal temperature rise. The pores are distributed through the thickness symmetrically and asymmetrically. The principle of Hamilton is employed in order to reach motion equations of porous metal foam plates. Next, governing equations of porous metal foam are derived for a refined inverse cotangential shear deformation plate and then solved analytically. The effects of various parameters including porosity coefficient, various types of porosity distribution, different types of temperature rise, length to thickness ratio, shape function, wave number and linear and shear layers of Kerr substrate on the variation of wave frequency and phase velocity of metal foam plate are covered and presented within the framework of a group of figures which can be observed in detail. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to investigate the yield criterion and dynamic response of fully clamped slender rectangular sandwich tubes with metal foam core struck by a low-velocity heavy mass. A plastic yield criterion is proposed for the rectangular sandwich tubes with metal foam core. Using the yield criterion, analytical solutions are derived for the dynamic response of fully clamped slender rectangular sandwich tubes with metal foam core struck by a low-velocity heavy mass, in which the foam core strength effect and the interaction of bending and stretching are considered. Numerical calculations are carried out to predict the dynamic response of the rectangular sandwich tubes under low-velocity impact. The analytical model captures the numerical results reasonably. The effects of foam core strength and wall thickness of tube on the dynamic response are discussed in detail. It is shown that the present analytical model can reasonably predict the dynamic response of the rectangular sandwich tube with metal foam core under the low-velocity impact. [ABSTRACT FROM AUTHOR]

In this paper, a numerical investigation in metal porous structures with Kelvin cell model is carried out on water/Al2O3 nanofluids using the single-phase model. The examined foams are characterized by a porosity of 0.95 and different values of cells per inch (CPI), equal to 10 and 20 CPI. Three different values of Al2O3 nanoparticle volume concentrations equal to 0, 2 and 4% are used. Results are presented and discussed in terms of pressure drop between the inlet and outlet sections. Furthermore, it has been possible to obtain a correlation used to find the value of permeability and drag coefficient for metal porous structures under investigation. It has been possible to notice how these two properties of the foam do not depend on the type of fluid but only on the geometric properties. In addition, the interfacial heat transfer coefficient between the fluid phase and the solid matrix has been estimated. In conclusion, the results in terms of Nusselt number as a function of Reynolds number based on the struct diameter show that it does not change varying the CPI values. [ABSTRACT FROM AUTHOR]

Although several field studies have indicated that water penetration can be expected through face-sealed joints over the lifespan of buildings, in particular, when sealed by means of construction sealant, face-sealed systems are still being applied by industry, e.g. precast concrete panels. Laboratory studies evaluating the concept of face-sealed joints are, however, limited. This study assesses and compares the initial performance of four sealing systems, tapes, silicone strips, silicone-based coating and foam sealing strips, applied to seal building joints in a face-sealed manner and subjected to simulated wind pressures and driving rain loads. The results give insight into the initial watertightness of the sealing materials and the sensitivity of the performance of the materials to different installation methods. The results indicate that water leakage can be expected through unperceivable openings in the face-sealed joints and that great care should be taken to install the sealing materials in the correct manner. The findings also suggest that closed-cell foam strips might be considered as an alternative to construction sealant to face-seal joints. Further research should evaluate the performance of these foam sealing strips after natural weathering and exposure to cyclic building movements. [ABSTRACT FROM AUTHOR]

Cold start has been realized as an important issue for PEMFC in its global commercialization. As is well-known, the conventional "channel-rib" type flow field will surely lead to several problems, such as water accumulation under the rib, resulting in slow water removal and serious ice blockage in the pores. In recent years, with the fast development of metal foam materials, metal foam has been recognized as a promising alternative replacement of the conventional "channel-rib" type flow field. In this study, a cold start model of PEMFC is established under sub-zero temperature. The coupled transport processes of heat, mass and charge in PEMFC under various subzero temperatures and startup modes are simulated. The results show that ice formation is slower in the PEMFC with metal foam as cathode flow field in cold start process, due to the superior performance of metal foam in water removal and uniform distribution of gas supply. However, the excellent thermal conductivity of metal foam could also result in faster heat loss from PEMFC. Furthermore, ice formation is highly dependent on the supercooled water transfer behavior, though small amount of supercooled water is maintained in the cell. This work aims to provide a systematic analysis for the cold start behavior of PEMFC with metal foam flow field. [ABSTRACT FROM AUTHOR]

High-porosity "cellular materials" are desirable for manufacturing multifunctional heat exchangers. While stochastic metal foams and regular strut-based topologies have been the focus of many prior investigations, there is very limited research on mathematically defined, triply-periodic minimal surfaces (TPMS). To this end, convective heat transport in sheet-based TPMS topologies, viz. gyroid and Schwarz P are numerically investigated and compared against "Tetrakaidecahedron," which is a representative unit cell of stochastic metal foams. The candidacy of sheet-based topologies over strut-based in conjugate thermal transport applications was evaluated by plotting the product h ¯ A f against the pumping power, where gyroid outperformed the other two topologies. [ABSTRACT FROM AUTHOR]

Metal foam, as a potential alternative to conventional flow fields in proton-exchange membrane fuel cells (PEMFCs), has been adequately proven to possess high gas uniformity and water storage ability. In this study, various cathode flow fields including meatal foam and conventional parallel and serpentine flow fields are compared experimentally. Meanwhile, electrochemical impedance spectroscopy (EIS) is also used to characterize the impedances as a further evidence of water management capacity for different flow fields. The results indicate that the cell with metal foam can achieve up to over 80% power density than that of the serpentine flow field with one third pressure drop. The porosity selection of metal foam is dependent on the inlet relative humidity (RH) to reduce the polarization loss and maximize the cell performance. The inlet relative humidity is also an important factor to the PTFE loading strategy for effective water removal. [ABSTRACT FROM AUTHOR]

The present research conducts an experimental study on the thermal performance of the finned metal foam (FMF) heat sinks with phase change material. The dynamic temperature response of an FMF heat sink is analyzed and compared with the corresponding finned heat sink. The effects of porosity and pore density on the thermal performance of FMF heat sinks are analyzed. Furthermore, the enhancement ratio and heat exchange capability are evaluated for the optimization of FMF heat sinks. The results indicate that the thermal conduction enhancement caused by the addition of metal foam exceeds the heat transfer loss arising from the suppression of natural convection. A decrease in porosity leads to an increase in heat exchange capability and contributes to a higher enhancement ratio. Considering the tradeoff between the low operating temperature and longer duration of reliability, the porosity of 0.9 is the best choice for FMF heat sinks. Though the porosity is identical, the thermal performance of an FMF heat sink is better with the increase of pore density. Considering the maximum energy charging capacities are identical, the FMF heat sink with larger pore density is recommended for practical engineering applications. [ABSTRACT FROM AUTHOR]

This article studies nonlinear dynamic buckling of imperfect beams made of functionally graded (FG) metal foams subjected to a constant velocity with various boundary conditions. Four types of FG porosity patterns, including two symmetric porosity distributions, non-symmetric porosity distribution, and uniform porosity distribution, are considered. By introducing the first mode function as a trial function, the Galerkin method is utilized to transform the governing equations into ordinary differential equations, which were then solved by the fourth-order Runge–Kutta method. The proposed methods are validated by using finite element method (FEM) and finally a detailed parametric study is conducted. [ABSTRACT FROM AUTHOR]

In this paper, experimental data pertinent to deionized water pool boiling across 10 mm thick aluminum foams are presented. Two foam samples with different pore densities, 5 and 10 pores per inch, yet an identical mean porosity of 0.92 are tested. Compared to a heated flat plate, of the same base size, the foams offer higher heat transfer area albeit at induced bubble escaping resistance. The tradeoff between these two effects is investigated. Through the use of high-speed camera recording, bubble generation, trajectory and growth rate were analyzed and critically discussed as functions of the working conditions and of the foam geometry. Furthermore, the experimental data were compared against a correlation appositely proposed for water pool boiling on metal foams. A good degree of agreement was observed. [ABSTRACT FROM AUTHOR]