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Graphite composite bipolar plate (BP) have limited conductivity, which makes them less than ideal for extensive application in proton exchange membrane fuel cell (PEMFC). In traditional graphite composite BP, the construction process of the conductive network is entirely random. To enhance conductivity, it is typically necessary to increase the content of conductive fillers or incorporate high aspect ratio carbon nanomaterials to optimize the density of the conductive network. In this work, we manufactured a highly conductive composite bipolar plate with synergistic conductive networks of graphite and metal foam (MF). With a synergistic conductive network, the ASR of CuG80-20ppi decreased to 7.7 mΩ cm2. Additionally, thermal conductivity increased to 24.76 W/(m·K), and in-plane conductivity reached 294.1 S/cm at 80 wt% mass fractions of conductive filler, using 20 ppi copper foam as the metallic conductive network. CuG80-20ppi exhibited a flexural strength of 52.2 MPa. G80 and CuG80-20ppi have the 80 wt% conductive filler and are molded into BP with parallel flow fields. CuG80-20ppi enhances the current density of PEMFC by 0.132 W/cm2 and reduces the ohmic impedance by 5.25%. Therefore, the findings of this study offer valuable insights for the enhancement of composite BP conductivity, while simultaneously ensuring the stability and continuity of the synergistic conductive network. A novel approach is presented to enhance the electrical conductivity of graphite composite bipolar plate (BP) for proton exchange membrane fuel cells (PEMFCs). By embedding metal foam as a supplementary conductive network within the graphite matrix, a synergistic conductive architecture is achieved. This innovation significantly reduces the area specific resistance (ASR) to 7.7 mΩ cm2 and boosts thermal conductivity to 24.76 W/(m·K). The resulting CuG80-20ppi BP, with 80 wt% conductive filler, exhibits improved mechanical strength and conductivity, contributing to a 0.132 W/cm2 increase in PEMFC current density and a 5.25% reduction in ohmic impedance. This work highlights the potential of metal foam integration to enhance BP conductivity and PEMFC performance. • A novel synergistic conductive network is introduced to develop bipolar plates. • This conductive network is constructed from graphite and metal foam. • It can achieve rapid and regular electronic transfer by metal and graphite. • Bipolar plate was optimized for brittleness by incorporating metal foam. • PEMFCs with this novel bipolar plate reduces Ohmic polarization by 5.25%. [ABSTRACT FROM AUTHOR]

Using metal foam as a flow field structure is an attractive route to improve the performance of open-cathode PEMFC. Metal foam has shown great potential in improving the uniformity of reactants, but optimized structure parameters that can more effectively transfer gas and remove excess water are needed. Here we experimentally investigate the effect of metal foam structure parameters on cell performance using polarization curves, power density curves, and electrochemical impedance spectrum (EIS) measurements. By optimizing the pore density, thickness, and compression ratio of the metal foam, the performance of the fuel cell is improved by 49.8%, 42.1%, and 7.3%, respectively. The optimum structure value of metal foam is the pore density of 40 PPI, the thickness of 2.4 mm, and the compression ratio of 4:2.4. In this configuration, the cell could achieve a maximum power density of 0.485 W cm−2. The findings of this work are beneficial for the application of metal foams in open-cathode PEMFC. [ABSTRACT FROM AUTHOR]

This study introduced a novel numerical modeling for the evaluation of a hybrid heat sink design by replacing the solid fins with aluminum foam fins (AFF) for the same thickness of 2 mm within a phase change material (PCM). This innovation is designed to enhance thermal performance in electronic cooling applications. Heat fluxes of 2, 3, and 4 kW/m2 were applied to the base. The performance has been verified at set point temperatures (SPT) of 60°C, 70°C, and 80°C, encompassing a range relevant to various applications. Different AFF thicknesses (4 and 6 mm) and foam porosities (0.85, 0.90, and 0.95) were investigated. The study demonstrated that AFFs improve heat transfer by increasing fin surface area and by effectively raising the thermal conductivity of the PCM. Compared to the SF heat sink, the results show that the AFF design extended the operational time by 5%–8% for the range of heat fluxes. Notably, AFFs with a thickness of 6 mm achieved a significant 41% improvement in the operation time at a lower SPT (60°C). The metal foam porosity of ε = 0.85 exhibited superior thermal performance within the investigated temperature range. This research paves the way for optimizing hybrid heat sink designs using metal foam for efficient thermal management and reduction of weight. [ABSTRACT FROM AUTHOR]

• New data of jet impingement boiling on surface modified metal foam were obtained. • Effects of metal foam wettability on boiling heat transfer were analyzed. • Influence on bubble dynamics behavior was analyzed. • New heat transfer coefficient correlation considering wettability was developed. Wettability may have significant influence on jet impingement boiling on metal foam, but the effect mechanism of metal foam wettability remains unclear. In this study, the boiling heat transfer characteristics of distributed jet array impingement on hydrophobic and hydrophilic metal foam covers were experimentally researched and compared with those on uncoated metal foam covers to analyze the influence of wettability. The experimental conditions cover contact angles of 14.0–158.7°, pore densities of 20–40 PPI, porosities of 92 %-97 %, thicknesses of 3.0–5.0 mm, and jet velocities of 0.5–4.0 m·s−1. The results show that, the obtained maximum heat flux and maximum heat transfer coefficient are up to 538.1 W cm−2 and 57.9 Kw m−2 K−1, respectively; the hydrophobic metal foam cover has a 4.8 K lower surface superheated degree at the onset of nucleate boiling, but a 7.5 % lower maximum heat transfer coefficient compared with the uncoated one; the hydrophilic metal foam cover shows a less deterioration after the departure from nucleate boiling but a 5.3 K higher surface superheated degree at the onset of nucleate boiling than those of the uncoated one. A new correlation for boiling heat transfer coefficients was developed with a mean relative error of 9.75 %. [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]

Lithium-based battery packs consist of numerous battery cells which form an essential component of electric vehicles. Inadequate heat transfer creates various challenges to safety issues in these batteries. Hence, assessment of the thermal performance of battery packs is an integral part of the design phase. In this study, a numerical approach of the system is implemented using a three-dimensional cylindrical model of a lithium Manganese dioxide battery cell. The model incorporates the application of the metal foam of different geometrical parameters saturated with air for the thermal cooling of batteries. The model considers the cooling phenomenon during discharge process of a cell with a C-rate of 1C respectively. The change in internal resistance of the cell with temperature during the process is estimated using the Generalized Reduced Gradient (GRG) algorithm. The system is considered to be adiabatic by maintaining a flow of liquid through convective tubes, to maintain a constant temperature. The Battery Thermal Management System design is proposed using the Ansys-Fluent software assuming finite volume analysis. The results are analyzed in terms of the maximum battery temperature attained and with the maximum surface temperature of the battery and the metal foams acquired during the process. [ABSTRACT FROM AUTHOR]

Dissipation of heat has become a common reason for the thermal runway and malfunction of various electronic devices. To effectively use these devices, it is mandatory to extract heat from the dissipating parts. Impinging jet flows (IJF) have been used for cooling purposes for decades. The jet impingement technique contains a pressurized fluid and is designed to spray the fluid with the help of a nozzle on the surface of the disc or plate which is being heated. However, recent advances on the effective heat transfer using metal foams are being studied. This research work focuses on the contribution of laminar and turbulent flows from IJF in extracting heat from the surface plate in the presence of geometrically diverse metal foams. The factors under consideration are H/Dj, Heat flux, thickness of the metal foams, and diameter of the metal foams. This research is purely experimental, and the experimental setup consists of mainly compressor, pressure gauges, rotameter, electric resistor, and thermocouples. The flows are controlled through rotameter and are kept in the range of Re from 800 to 2000 for laminar and from 3000 to 23000 for turbulent region. The outcomes of the results are extremely useful in engineering applications and the data can be used to design an effective heat exchanger. [ABSTRACT FROM AUTHOR]

Melting and solidification of a phase change material (PCM) is investigated experimentally by applying a partial filling strategy to the hybrid enhancement of heat pipe–metal foam (HP‐MF) in a vertical cylinder. HP‐MF enhancement can improve the heat transfer capacity of the PCM system as it combines HP's efficient heat transfer capacity with MF's highly effective thermal conductivity capability. The experimental results demonstrate that the partial filling strategy in the melting and solidification of HP‐MF PCM can be optimized for effective MF utilization in the HP‐MF PCM system. A filling ratio of 83% of MF in HP‐MF PCM shows almost identical total melting and solidification along with a temperature distribution to that of an HP‐MF PCM (95% porosity, 20 pore density [PPI]). It is plausible to conclude that the removal of 33% or less mass had no significant effect on the overall melting process of HP‐MF PCM. It should be noted that the HP‐MF PCM system's HP heat transfer efficiency significantly decreased during the melting process when the MF filling ratio was 37.5% and 12.5%. [ABSTRACT FROM AUTHOR]

The compressive behavior is one of the most fundamental mechanical properties for engineering materials. In this paper, the octahedral structure model of porous materials is used to evolve the mechanical analysis model under compressive loading for the porous composite materials, which are resulted from reticular metal foams with pore struts presenting multilayered structure. Starting from this analysis model, some fundamental mechanical relationships, including those of the safe load-bearing and overall strength, have been deduced for these porous composite materials. The compressive strength has been characterized for the porous composite body, corresponding to the overall failure caused by the prior breakage of the strut core and by the prior breakage of the strut shell, respectively. The nickel foam products manufactured on the production line of enterprise were used to make porous composite materials by coating the pore struts with epoxy resin, and the metal foam composite material was obtained with the composite pore-struts of metal/resin multilayered structure. Using this porous composite material for compression experiments, it is found that the experimental data match well with the mathematical relationship from the present theoretical model. The results verify the feasibility of this analysis model and the practicality of the relevant mathematical relationship. [ABSTRACT FROM AUTHOR]

An experimental investigation was carried out on high porosity metal foams subjected to array jet impingement with an objective to develop enhanced heat transfer configurations. In this study, we propose an integrated thermal management system (TMS) aimed toward leveraging the conjugate heat transfer capabilities of target plate, metal foam, and the jet plate--all made from aluminum and assembled such that a proper contact between them can be established. Steady-state heat transfer experiments were carried out for 10 and 20 pores per inch (PPI) aluminum foams of 0.93 porosity. Both metal foams were 12.7-mm thick. The normalized jet-to-jet spacing was varied from 2 to 12 times the jet diameter, while the jet diameter was fixed. The ratio of the jet plate thickness and jet diameter (nozzle aspect ratio) was 6.35, which ensured proper development of jets inside the nozzles. Experiments were conducted over a wide range of Reynolds number (based on jet diameter) varied from 100 to 5000. The obtained convective heat transfer coefficient for different configuration was evaluated in context with pressure drop. The analysis of experimental results reveal that large open area ratio jets combined with high porosity metal foams provide highly efficient and high-performance cooling for the investigated range of Reynolds numbers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, theoretical and numerical studies of the dynamic response of a fiber–metal laminate (FML) sandwich beam under uniform blast loading are conducted. On the basis of a modified rigid-plastic material model, the analytical solutions for the maximum deflection and the structural response time of FML sandwich beams with metal foam core are obtained. Finite element analysis is carried out by using ABAQUS software, and the numerical simulations corroborate the analytical predictions effectively. The study further examines the impact of the metal volume fraction, the metal strength factor between the metal layer and the composite material layer, the foam strength factor of the metal foam core to the composite material layer, and the foam density factor on the structural response. Findings reveal that these parameters influence the dynamic response of fiber–metal laminate (FML) sandwich beams to varying degrees. The developed analytical model demonstrates its capability to accurately forecast the dynamic behavior of fiber–metal laminate (FML) sandwich beams under uniform blast loading. The theoretical model in this article is a simplified model and cannot consider details such as damage, debonding, and the influence of layer angles in experiments. It is necessary to establish a refined theoretical model that can consider the microstructure and failure of composite materials in the future. [ABSTRACT FROM AUTHOR]

Metallic foams exhibit unique properties that make them suitable for diverse engineering applications. Accurate mechanical characterization is essential for assessing their performance under both monotonic and cyclic loading conditions. However, despite the advancements, the understanding of cyclic load responses in metallic foams has been limited. This study aims to propose a mesostructural model to assess the fatigue behavior of open-cell metal foams subjected to cyclic loading conditions. The proposed model considers the previous load history and is based on the analogy of progressive collapse, integrating a finite element model, a fatigue analysis model, an equivalent number of cycles model, and a failure criterion model. Validation against experimental data shows that the proposed model can reliably predict the fatigue life of the metallic foams for specific strain amplitudes. [ABSTRACT FROM AUTHOR]

The main task of this work is the optimization of the manufacturing process of Al-alloy lattice cellular structures with rhombic cell, obtained with lost-PLA technique. It is an easy, environment sustainable and economical technique (both for infrastructure and operating costs) for the manufacturing of Al porous structure based on the 3D printing of PLA and replication process alternative to that based on expensive metal 3D printers. Plaster processing, PLA burnout and AA 6082 alloy casting conditions and parameters have been suitably tuned in order to get final samples with geometry and surface finishing conditions identical to the starting ones made in PLA. A good replication process has been implemented with a high repeatability rate and accurate surface finishing, comparable with that of the PLA printed objects. Morphological analysis on PLA and Al 6082 was conducted as well microstructural analysis and Vickers microhardness tests on Al alloy samples in the as-cast conditions. Metallography reveals the presence of AlFeSi and AlFeMnSi intermetallic phases at the cell boundaries and some coarse precipitates Mg2Si in the AA 6082 alloy. Microstructures and HV measured values are aligned with literature data for this alloy in the same (as-cast) conditions. [ABSTRACT FROM AUTHOR]

The need for high speed and reduction in size in electronic components leads to a rise in the power dissipation needed for thermal management. In this research, experiments have been carried out to examine the thermal efficiency from heat sink located on an energy source in a channel. A total of 4 test models with different shapes were tested. Model 1 conventional heat sinks is made from aluminum, model 2 fin heat sinks is made from metal foam, model 3 plate heat sink is made from metal foam and model 4 fin heat sinks filled space between the fins with metal foam; all models have the same flat plate surface area. Copper metal foam of constant pore density of 40 PPI and constant porosity of 0.91 were used. The test runs are done at the air flow rates ranging between (1.2 to 3.3) m/s with the inlet air temperature is 27 °C. The outcomes revealed that the model 3 heat sinks have a greater heat transfer coefficient and a lower thermal resistance than the other types of heatsinks. At input velocity of 3.3 m/s and high power of 30 W, model 3 has the best Nusselt number ratio it has increased from models 2 and 4 by 13.7% and 6.8%, respectively. The plate foam heat sink model 3 has a larger pressure drop when compared to conventional fin heat sink model 1. Moreover, the pressure drop between Models 2 and Model 4 is not significantly different. Additionally, at higher flow rates, the model 3 heat sinks show a 22% reduction in thermal resistance compared to the model 1 at a power of 30 W. [ABSTRACT FROM AUTHOR]

The inefficacy of the conventional methods to form Aluminium Foam Sandwich (AFS) has led to the evolution of laser forming as an alternative. However, the current literature lacks studies that demonstrate the capability of the laser forming to form a targeted part out of AFS. The current study for the first time proposed a methodology and revealed salient factors relevant to laser forming an AFS panel into a prescribed scaled-down model (bumper beam). Estimation of the scan line position and the experimental methodology to obtain the desired process parameters against each scan line to obtain the targeted part are demonstrated. Chances of failure of the AFS part during the laser forming were investigated using finite element simulation. The laser-formed part that was finally obtained conformed well to the targeted shape and also exhibited improved flexural strength with no loss of local compressibility under the three-point bending test. [ABSTRACT FROM AUTHOR]

The main task of this work is the optimization of the manufacturing process of Al-alloy lattice cellular structures with rhombic cell, obtained with lost-PLA technique. It is an easy, environment sustainable and economical technique (both for infrastructure and operating costs) for the manufacturing of Al porous structure based on the 3D printing of PLA and replication process alternative to that based on expensive metal 3D printers. Plaster processing, PLA burnout and AA 6082 alloy casting conditions and parameters have been suitably tuned in order to get final samples with geometry and surface finishing conditions identical to the starting ones made in PLA. A good replication process has been implemented with a high repeatability rate and accurate surface finishing, comparable with that of the PLA printed objects. Morphological analysis on PLA and Al 6082 was conducted as well microstructural analysis and Vickers microhardness tests on Al alloy samples in the as-cast conditions. Metallography reveals the presence of AlFeSi and AlFeMnSi intermetallic phases at the cell boundaries and some coarse precipitates Mg2Si in the AA 6082 alloy. Microstructures and HV measured values are aligned with literature data for this alloy in the same (as-cast) conditions.

The two-dimensional numerical simulations focused on fluid flow and heat transfer within a solar air heater (SAH) channel incorporating copper metal foam with a porosity of 90% were carried out in this study. The Local Thermal Non-equilibrium (LTNE) and Darcy-Extended Forchheimer (DEF) models were employed to predict fluid and thermal transport in the partially porous SAH channel. In the free flow zone, the turbulence model was utilized. The thermal and thermo-hydraulic performances of SAH were examined concerning several factors, including pore density ( ), Reynolds number ( ), and dimensionless foam height ( ). The results demonstrate that inserting a porous substrate into the SAH can substantially increase heat transmission. This enhancement ranges from 4.4 to 18.04 times compared to an empty duct for at . Moreover, increased porous layer height and pore density lead to a corresponding increase in pressure drop. Evaluating both the improvement in heat transmission and the associated pressure penalty, the case with , and demonstrate superior overall performance, boasting a higher Thermal Performance Factor ( ) of 2.82 when compared to an empty channel. This work presents significant findings on optimizing metal foam applications in SAH systems, offering new insights into the field.

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]

High output temperature and photothermal conversion effectiveness were achieved with the absorber platform structure. A novel solar receiver was manufactured to integrate pre-heating and thermal conversion, aiming to enhance heat utilization and output temperature. This work is based on the engineering design and experimental testing of a solar cavity-receiver containing a porous copper foam that can volumetrically absorb high-flux radiation and heat up, through convection with air-flow. The air outlet temperature, outer wall temperature, thermal performance, and efficiency were experimentally determined by pore density, air mass-flow rate and solar irradiance. Additionally, the temperature growth of unit incident power, the unit volume efficiency growth rate, and output temperature were employed to evaluate the thermal conversion characteristics of the endothermic body (copper foam). The results indicated that the air outlet temperatures can reach 500 °C with lower input power. Furthermore, it was found that under a pore density of 30 pores per inch and a flow rate of 60 Lpm, the photothermal conversion efficiency of the absorber with copper foam reached as high as 87.61%, which is 35.04% significantly higher than that of an absorber without copper foam. The manageable solar receiver design proved to deliver a high-temperature air-flow (approximately 500 °C) with a reasonably high thermal efficiency (over 85%). [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]

Copyright of Safety & Security Sciences Review / Biztonságtudományi Szemle is the property of Obuda University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metal foam flow fields are considered as an alternative to conventional channel/rib flow field in polymer electrolyte membrane fuel cell (PEMFC) because of the advantages of three-dimensional pore structure. In this study, the effect of metal foam flow field with different manifold size on PEMFC performance was investigated, with a 25 cm2 unit cell. Polarization curve and electrochemical impedance spectroscopy results were analyzed to investigate the effects of gas stoichiometry and relative humidity on performance. The mass transfer loss was decreased with reduced manifold size. However, mass transfer loss was increased due to difficulty of water discharge in small manifold case. The metal foam flow field offer advantages in water discharge and mass transfer loss. At 100% relative humidity, performance was improved with increased air stoichiometry for different manifold size. At 25% relative humidity, performance was a little improved with increased air stoichiometry for small manifold case. Regardless of relative humidity, fuel cell performance with metal foam flow field was most improved in case of smallest manifold size based on air stoichiometry due to the high pressure drop. • The performances were not proportional to the size of the manifold. • Increasing air stoichiometry, the performance increase was highest for the smallest manifold size. • The mass transfer was mainly influenced by the size of the manifold. [ABSTRACT FROM AUTHOR]

Porous copper (Cu), with varying porosities, has been made using carbamide as a space holder through the powder metallurgy route. Two shapes of carbamide particles were used, (i) needlelike and (ii) spherical, in order to investigate the effect of the space holder shape on the pore structure and mechanical properties of porous Cu. The compressive deformation behavior of porous Cu was studied under a compression test. The pores' structural characteristics and mechanical properties of the porous Cu varied significantly with the shape of the space holder. Although the effect of the space holder shape on the porosity was not regular, the effect on the mechanical properties was regular. The stress increased monotonically with the increase in the strain, and strain hardening occurred at the plastic yield stage. The elastic modulus and yield strength followed the power law, with the relative density irrespective of the space holder shape. The empirical constants associated with different empirically developed power law relations were different, according to the shape of space holder. A quantitative relationship between the elastic modulus and yield strength and the spacer content was obtained to control the mechanical properties of the present porous Cu or other porous metals and metal foams using the well-known space holder method. [ABSTRACT FROM AUTHOR]

This paper investigates the low-velocity penetration dynamic response of metal foam core sandwich panels with composite face sheets reinforced by nanoparticles. Based on the experimental results, an energy model is developed to predict contact force, impactor displacement, energy absorption, mechanisms of impact damage, and failure modes. An elastic–plastic–rigid (E–P–R) model is used to derive the energy absorbed by the metal foam. A stress function in terms of density ratio and strain is considered to predict the compression behavior of metal foam. The effect of nanoparticles investigated by the Halpin Tsai model. The analytical prediction is compared with the results of the experimental test and a reasonable agreement has been observed. The tested sandwich panel consisted of an aluminum foam core and an epoxy/carbon fiber face sheet reinforced with reduced graphene oxide (RGO). This model is useful for improving the design of sandwich panels with carbon fiber composite face sheet reinforced with nanoparticles and aluminum foam core. The results of impact test showed the addition of reduced oxide graphene increased the value of the first peak load by about 15%, the second peak load by about 36% and the amount of energy absorption in sandwich panel by about 18%. The radios of delamination and debonding reduced by 47% and 17.5%, respectively, compared to the sample without nanoparticles. [ABSTRACT FROM AUTHOR]

This study investigates the impact of gas flow field design on the performance of a solid oxide fuel cell (SOFC). A three-dimensional numerical model of the cell and channel is developed to simulate the use of metal foam as flow distributor, along with the presence of obstacles in the gas flow channels. The model is calibrated using experimental data and applied to simulate four relevant cases combining metal foam and obstacles, compared to a straight channel structure. The results demonstrate the positive impact of flow-field modifications on the distribution of species along the cell's active layers. It is found that, even though the pressure drops are affected, reactant gases are more uniformly distributed across the active electrode of the cell, reducing mass transport losses and enhancing current density. Simulations performed at a cell voltage of 0.7 V indicate that incorporating a metal foam as flow distributor increases the maximum current density by 26 % compared to the conventional straight flow design. Furthermore, combining metal foam with obstacles results in the best performance, achieving a 34 % increase in the maximum current density.

Present study reports the influence of various orifice shapes (circular, square, triangular, and elliptical) on the local and average heat transfer properties of a metal foamed surface for a varied range of Reynolds number (Re = 10000 –30,000) and plate to nozzle distances (z/d = 1–10) by employing thermal imaging techniques. A copper open-cell metal foam (OCMF) with a porosity of 90% and a pores per inch (PPI) value of 20 is attached to the flat plate. The thermal behavior of the thin foil in conjunction with the OCMF employing various orifices is observed to be better than that of the smooth foil. The enhancement in heat transfer at the stagnation point for circular, elliptical, square, and triangular orifices with metal foamed plate is observed to be around 76%, 64%, 54%, and 55%, respectively, for Re = 10000. The hot surface integrated with metal foam exhibits improvements in the local thermal characteristics with distinct orifice configurations. A dimensionless foam enhancement factor was defined to assess the influence of foam on jet impingement heat transfer. The foam effect is particularly noticeable in the impingement zone compared to the wall jet region. Compared to other parameters, the nozzle-to-plate distance has a significant effect on the enhancement factor. For z/d ≤4, the improvement in local heat transfer is observed in the stagnation region (x/d ≤2); while, for a higher value of nozzle to plate distance (z/d $ \gt $>6), a uniform augmentation in thermal performance is noted across the entire heated surface. Elliptical and circular orifices exhibit better thermal performance compared to square and triangular orifices. The findings demonstrate that the foam-integrated foil significantly enhances heat transfer performance, particularly at increasing impinging distances. [ABSTRACT FROM AUTHOR]

A numerical assessment of the heat transfer efficacy of a solar air heater (SAH) was carried out. The SAH is supplied with a porous metal foam layer to improve thermal mixing. Both the local thermal non-equilibrium (LTNE) and Darcy-extended Forchheimer (DEF) models were employed to forecast fluid and thermal transport within the partly filled SAH channel. The analysis was performed for various values of dimensionless foam layer lengths ( S = 0 - 1 ), pore densities ( ω = 10 - 40 PPI ), and Reynolds numbers ( R e = 4000 - 1 6 , 000 ) at a fixed value of layer thickness ( H f = 0.6 ). Based on the position of the porous layer, three distinct arrangements, marked as Case 1, Case 2, and Case 3, were explored. Regarding the parameters examined, the findings indicate a definite improvement in the average Nusselt number ( Nu ), but unfortunately, the friction factor also increases unfavorably. By reducing the length of the porous layer, a reasonable reduction in heat transfer rate and a significant decrease in pressure drop were noticed. The results showed about 26.64%, 48.73%, and 70.74% reductions in pressure drop by reducing the dimensionless foam length from 1 to 0.25, 0.5, and 0.75 respectively for ω = 10 at R e = 16 , 000 . On the other side, there are only about 11.05%, 23.11%, and 40.78% reductions in Nu . The exhaustive analysis of the thermal performance of SAH was conducted using the thermal performance factor (TPF), which considers the trade-off between the SAH channel's potential for improved heat transmission and its cost for pressure loss. The TPF may reach a maximum of 2.82 compared to the empty channel when the metal foam layer is inserted with S = 1 , for ω = 10 , and R e = 16 , 000 . [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]

While it is known that PEMFCs with inserted metal foam exhibit superior performance under normal conditions compared to serpentine flow fields, the practical application of such configurations does not guarantee continuous operation under optimal conditions. Therefore, the durability and performance under various extreme conditions need to be demonstrated. Through this study, we aim to compare the durability and performance of the metal foam flow field with a serpentine channel under severe operating conditions. We conducted mechanical accelerated degradation tests, electrochemical accelerated degradation tests, and applied low stoichiometric ratio (SR) and low relative humidity (RH) conditions to both channels to compare their performance under each extreme scenario. The metal foam-inserted flow field demonstrated a higher degradation rate but higher power output in all scenarios, with a notable 30.1% degradation rate in the 18-day without load cycle test, compared to 21.0% in the serpentine flow field. Despite the elevated degradation rate, the metal foam-equipped cell achieved a 15.8% higher maximum power output. Furthermore, the fuel cell with metal foam flow field shows higher air utilization rate and better water management in low stoichiometric ratio and extremely low relative humidity, respectively. In conclusion, this study suggests that the metal foam flow field may not only be a better choice under typical operating conditions but also a superior alternative to the serpentine flow field in various extreme operating conditions. • Performance changes under harsh operating conditions for fuel cells were examined. • The fuel cell with metal foam flow field showed higher maximum power density. • The fuel cell with metal foam flow field had higher air utilization rate. • The fuel cell with metal foam flow field had better water management. [ABSTRACT FROM AUTHOR]

The aim of the present research work is to understand the intricacies of fluid flow through a rectangular channel that has been partially filled with a metal foam block of different blockage ratio (0.16-1), with a pore density (5-30 Pores Per Inch i.e. PPI), along with varying inlet velocity (6.5-12.5 m/s). For the porous region, numerical solutions are acquired using the Darcy Extended Forchheimer model. The Navier-Stokes equation is used in the non-porous zone. Different flow behaviours were seen as a function of PPI, height, and inlet velocity. The pressure drop increases with inlet velocity, PPI, and block height, with a maximum value of approximately 4.5 kPa for the case of 30 PPI, 12.5 m/s, and a blockage ratio of 1. Results show that the existence and location of the formation of eddies depends on the inlet velocity, PPI, and blockage ratio. Such studies have been reported less and will aid research on forced convection through a channel partially filled with metal foam and optimisation studies between increased heat transmission and the additional pressure drop for the same by providing a detailed fluid flow analysis. [ABSTRACT FROM AUTHOR]

Protective steel doors are widely used in buildings due to their high resistance against the impact loads. However, its heavy weight has been always considered as a major drawback for these doors. In this paper, a new optimized stiffened impact-protective steel door incorporating sandwich panel with aluminum foam core (OSSA) is examined. This door consists of two face sheets, main and secondary stiffeners, and aluminum foam as the inner core. In order to optimize the door, at first the rigidity and weight functions of the stiffened steel door were extracted. Then an optimal door weighing 42% less than the primary door was obtained. Due to the high energy absorption capacity of the combined foam core and stiffened steel door structure, the use of aluminum foam core in the optimized steel door was proposed. By doing numerical analysis, and depending on the thickness of the face sheet of OSSA, 20 to 32% reduction in the maximum displacement was observed. The results also showed that, with 67% increase in the peak overpressure, OSSA has kept almost the same maximum displacement as that of the steel door without an aluminum foam. In other words, by using aluminum foam core in the optimized stiffened door, the door will resist 67% more impact load. [ABSTRACT FROM AUTHOR]

With the development of surface engineering, porous surfaces have emerged as a significant research subject in boiling heat transfer. The latter, in turn, plays a crucial role in various industries such as power plants, distillation plants, and microelectronic technology. In this paper, the Molecular Dynamics method is adopted to investigate the wicking dynamics and boiling dynamics of two porous surfaces: foam, which exhibits randomly distributed pores, and mesh, composed of ordered square wires with relatively uniform pore sizes. Three wettability, namely hydrophilic, neutral, and hydrophobic wetting states, are assigned to the two porous surfaces de-coupling the effect of wettability from surface structure. Results reveal that, during the wicking process, the foam surface shows better wetting ability as it absorbs liquid under both hydrophilic and neutral wettability. Comparatively, the mesh surface has the fastest wicking speed under hydrophilic wettability yet it becomes non-wetting under neutral wettability. During the boiling process, the boiling dynamics differ greatly under three wettability. More importantly, the difference in surface structure makes the foam surface possess a better heat transfer whereas the mesh surface causes gentle pressure variation. Our findings provide insights into the design of artificial porous surfaces for certain purpose and their potential application.

A 2D numerical analysis was conducted to examine the melting performance of a shell-and-tube-type phase change material with a two-layer copper foam having higher and lower porosity levels. The design parameters for these two layers of metal foam consisted of three different volume fill ratios (VFR) (30 %/70 %, 50 %/50 %, and 70 %/30 %) and three different shapes (circular, semi-circular, and elliptical) for the lower porosity layer. The results showed that a semicircular-shaped low porosity layer with a 30 % VFR had the least melting time of 475 s. When the VFR increased to 50 %, the elliptical and circular shapes had the least melting time of 394 s. However, at a VFR of 70 %, only the elliptical shape had the least melting time of 323 s. Furthermore, the results were compared with the uniform porosity metal foam system, and deduced that the two-layer system did not always have the lower melting time compared with that of the uniform porosity system because it depended on the VFR and shape of the different porosities filled in the different layers. Additionally, for an average porosity of the metal foam, an optimal combination of two different porosities was observed for the melting performance.

A natural convection heat transfer inside rhombic square cavity partially filled with porous material have been numerically investigated. A constant heat flux has been applied to the left wall with a right wall kept in constant cold temperature while thermally insulated the top and bottom walls. Finite volume technique with Simple algorithm have been used to simulate the governing equations of fluid flow and heat transfer coupled with Darcy-Brinkman model to simulate the flow of the air inside the main cavity and the open cells of the porous media. Three factors were chosen to study their effects on the natural air velocity and the mechanism of the free convection inside the enclosure. The inclined angle of the sidewall of the rhombic (q = 90o, 80o and 70o), the thickness of the metal foam (t = 5 cm, 10 cm, and 15 cm) and the amount of heat flux (q = 150 to 600 w/m2). Copper metal foam with 0.9 porosity was chosen as porous media with open cell filled by air (Prandtl number =0.7) and 10 as pore density. The results showed that using a layer of porous metal foam with open cells will increase the heat transfer rate. It was 41.3% enhancement when use 5 cm of porous media and 68% for 15 cm. Acute inclined angle will decrease local Nusselt number and led to form vorticities. Furthermore, high heat flux increased the average Nusselt number and improved the heat transfer rate.

Abstract A solid substance encircled by a three-dimensional network of voids not interconnected with each other is referred to as close-cell metal foam. The work is based on enhancing mechanical properties of aluminum base close-cell metal foam through the addition of reinforcing particles in varying percentages. Closed-cell aluminum foams with the addition of Mn (0.5 wt.%) and Mg (0, 1, 1.5, 2) were successfully prepared by the melt route method. Al-based metal foam’s morphology and mechanical behavior were examined in order to understand the impact of reinforcing elements. From the current work, it is inferred that the addition of reinforcing elements initially helped to increase the compressive strength as found in Foam-1, but further addition of Mg did not have any beneficial effects. It was found that the value of compression strength depends on foam density. The addition of reinforcing elements increases the length of the plateau which in turn increases the value of energy absorption. It is found that proper bonding of reinforcing particles helps in improving energy absorption. From the evaluation, it was found that besides the increase in density and variations in pores uniformity, Al + Mn (0.5wt. %) + Mg (1.5wt. %) Foam (Foam-1) was found to be superior among all other foams. It can also be concluded that by fixing the percentage of Mn by 1 wt%, the best results can be obtained by addition of 1.5 wt. % Mg in the melt. Further addition of Mg shows a detrimental effect on mechanical and physical properties.

The aim of the present research work is to understand the intricacies of fluid flow through a rectangular channel that has been partially filled with a metal foam block of different blockage ratio (0.16-1), with a pore density (5–30 Pores Per Inch i.e. PPI), along with varying inlet velocity (6.5–12.5 m/s). For the porous region, numerical solutions are acquired using the Darcy Extended Forchheimer model. The Navier-Stokes equation is used in the non-porous zone. Different flow behaviours were seen as a function of PPI, height, and inlet velocity. The pressure drop increases with inlet velocity, PPI, and block height, with a maximum value of approximately 4.5 kPa for the case of 30 PPI, 12.5 m/s, and a blockage ratio of 1. Results show that the existence and location of the formation of eddies depends on the inlet velocity, PPI, and blockage ratio. Such studies have been reported less and will aid research on forced convection through a channel partially filled with metal foam and optimisation studies between increased heat transmission and the additional pressure drop for the same by providing a detailed fluid flow analysis.

The use of Phase Change Materials (PCMs) for latent thermal energy storage enhances the availability of solar energy. PCMs can store a large amount of energy in a small volume using almost entirely isothermal processes. Despite this, the poor thermal conductivity of PCMs is a significant disadvantage of current PCMs, severely limiting their energy storage capabilities. As a result, the solidification/melting rates are reduced to an unacceptable level, and the system reaction time is increased unreasonably. By combining the novel fin arrangement, nanoparticles, and metal foam, the current study improved the solidification rate of the PCM in the Latent Heat Thermal Energy Storage System (LHTESS). LHTESS was numerically evaluated in ANSYS Fluent 18.1 using a solidification and melting model. The addition of cesaro fins, nanoparticles, and metal foam significantly improved PCM solidification in the LHTESS. PCM solidification time was reduced by 42.42% and 39.39% in Type-3 and Type-5 fin configurations, respectively, when compared to Type-4 fin configuration. Furthermore, a temperature difference of 27 K between the Heat Thermal Fluid (HTF) and the PCM ensures the best solidification performance. By incorporating nanoparticles into PCM and metal foam, the solidification time is reduced by 73.68%. Depending on the foam structure and volume fraction of the nanoparticles, dispersing nanoparticles in PCM with metal foam saves up to 75% of the time.

In this work, theoretical and numerical studies of the dynamic response of a fiber–metal laminate (FML) sandwich beam under uniform blast loading are conducted. On the basis of a modified rigid-plastic material model, the analytical solutions for the maximum deflection and the structural response time of FML sandwich beams with metal foam core are obtained. Finite element analysis is carried out by using ABAQUS software, and the numerical simulations corroborate the analytical predictions effectively. The study further examines the impact of the metal volume fraction, the metal strength factor between the metal layer and the composite material layer, the foam strength factor of the metal foam core to the composite material layer, and the foam density factor on the structural response. Findings reveal that these parameters influence the dynamic response of fiber–metal laminate (FML) sandwich beams to varying degrees. The developed analytical model demonstrates its capability to accurately forecast the dynamic behavior of fiber–metal laminate (FML) sandwich beams under uniform blast loading. The theoretical model in this article is a simplified model and cannot consider details such as damage, debonding, and the influence of layer angles in experiments. It is necessary to establish a refined theoretical model that can consider the microstructure and failure of composite materials in the future.

Metallic foams exhibit unique properties that make them suitable for diverse engineering applications. Accurate mechanical characterization is essential for assessing their performance under both monotonic and cyclic loading conditions. However, despite the advancements, the understanding of cyclic load responses in metallic foams has been limited. This study aims to propose a mesostructural model to assess the fatigue behavior of open-cell metal foams subjected to cyclic loading conditions. The proposed model considers the previous load history and is based on the analogy of progressive collapse, integrating a finite element model, a fatigue analysis model, an equivalent number of cycles model, and a failure criterion model. Validation against experimental data shows that the proposed model can reliably predict the fatigue life of the metallic foams for specific strain amplitudes.