Future of Metal Foam Materials in Automotive Industry

The present study presents a concept of biporous metal foam heat sink applicable to electronic cooling. This heat sink has two metal foam layers arranged in parallel along the primary flow direction, with different metal foam thickness, porosity, and pore density for each layer. The forced convective heat transfer in biporous metal foam heat sink is numerically investigated by employing the Forchheimer–Brinkman extended Darcy momentum equation and local thermal nonequilibrium energy equation. The effects of geometrical and morphological parameters on thermal and hydraulic performance are discussed in detail, and the heat transfer enhancement mechanism of biporous metal foam is analyzed. The thermal performance of biporous metal foam heat sink is compared with that of uniform metal foam heat sink. The results show that the thermal resistance of the biporous metal foam heat sink decreases with decrease of top layer metal foam porosity at a fixed bottom metal foam porosity of 0.9. It is seen that the biporous metal foam heat sink can outperform the uniform metal foam heat sink with a proper selection of foam geometrical and morphological parameters, which is attributed to the presence of high velocity gradient at the boundary layer that can enhance the convective heat transfer. The best observed thermal performance of biporous metal foam heat sink is achieved by employing 30 pores per inch (PPI) metal foam at the bottom layer, with a fixed 50 PPI metal foam at the top layer for the porosities of both layers equal to 0.9, and the optimal thickness of the bottom foam layer is about 1 mm.

Effect of spatial porosity of metal foams on heat transfer filled in a vertical channel

Transient heat transfer analysis of phase change material melting in metal foam by experimental study and artificial neural network

In this paper, experimental investigations were carried out to observe the melting process of a bio-based nano-phase change materials (PCM) inside open-cell metal foams. Copper oxide nanoparticles with five different weight fractions (i.e., 0.00%, 0.08%, 0.10%, 0.12%, and 0.30%) were dispersed into bio-based PCM (i.e., coconut oil) to synthesize nano-PCMs. Open-cell aluminum foams of different porosities (i.e., 0.96, 0.92, and 0.88) and pore densities (i.e., 5, 10, and 20 pores per inch (PPI)) were considered. An experimental setup was constructed to monitor the progression of the melting process and to measure transient temperatures variations at different selected locations. Average thermal energy storage rate (TESR) was calculated, alongside the melting time was recorded. The effects of various nanoparticles concentration, metal foam pore densities, porosities, and isothermal surface temperature on the melting time, TESR, thermal energy distribution, and the melting behavior were studied. It was observed that the melting time significantly reduced by using metal foam and increasing the isothermal surface temperature. It was concluded that the effect of adding nanoparticles on the TESR depends on the characteristics of metal foam, as well as, the weight fractions of nanoparticles. The change in TESR varied from −1% to 8.6% upon addition of 0.10 wt % nanoparticles compared to pure PCM, whereas the increase in the nanoparticles concentration from 0.10% to 0.30% changed TESR by −10.6% to 4.5%. The results provide an insight into the interdependencies of parameters such as pore density and porosity of metal foam and nanoparticles concentration on the melting process of nano-PCM in metal foam.

Introduction. The paper presents a comprehensive overview of the manufacturing methods, materials, properties, and challenges associated with cellular metallic foams, primarily focusing on aluminum and titanium-based foams. Cellular metallic foams are gaining interest due to its unique combination of low density, high stiffness, and enhanced energy absorption capabilities. Cellular metallic foam is renowned for its special combinations of physical and mechanical characteristics, containing their increased stiffness, specific strength at high temperatures, light weight, and good energy absorption at relatively low plateau stress. It has extensive uses in the automotive, shipbuilding and space industries. It has high porosity, low relative density and high strength, which increases performance of the product. The aerospace and automotive industries require a material with a high strength-to-weight ratio. Methods. To meet this need, many metal foam production methods have been developed, such as melt route method, deposition method and powder metallurgy method. Melt route method is widely used to manufacture metallic foam as compared to other methods. Results and Discussion. In the production of aluminum foams, the melt route method is usually used. Titanium hydride (TiH2) has been a popular foaming agent, but its high decomposition rate and cost limitations have led to the development of alternative foaming agents, such as CaCO3 (calcium carbonate). Titanium foam is often manufactured using the space holder method. This method involves mixing titanium powder with a space holder material, forming a preform, and then sintering to remove the space holder and produce a porous structure as the space holder method allows for precise control over the properties of the foam, including pore size, porosity, and relative density. Results also indicate that porosity in cellular metallic foams can range from 50 % to 95 %, as reported in various journals. Pore structures can include mixed types, open cells, and closed cells, each offering different mechanical and thermal properties. It is also observed from various literature sources that relative density, which is the ratio of the foam's density to the bulk material's density, varies from 0.02 to 0.44 based on the production method used.

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.

A computational fluid dynamics analysis of forced convective heat transfer has been conducted numerically on the hydrodynamic and heat transfer of airflow through vertical channel. The effects of airflow Reynolds number, metal foam porosity and thermal conductivity on the overall Nusselt number, pressure drop, maximum temperature and temperature distribution were considered. The novelty of the present study is the use of metal foams in a two-sided vertical channel and the quantification of the heat transfer enhancement compared to an empty channel for different foam material. Based on the generated results, it is observed that the heat transfer rate from the heated plate is the same for aluminium foam (porosity of 0.948) and copper foam (porosity of 0.877) against equal velocity range and heat flux conditions. Furthermore, it is noted that increasing the airflow velocity reduces the maximum temperature; however, the decrement is not linear. Results obtained from the proposed model were successfully compared with experimental data found in the literature for rectangular metal foam heat exchangers.

Numerical and experimental investigations of latent thermal energy storage device based on a flat micro-heat pipe array–metal foam composite structure

Aluminum metal foam, distinguished by its lightweight nature, exceptional strength-to-weight ratio, and distinctive cellular structure, has emerged as a highly promising material with extensive applications across diverse industries. Various fabrication techniques, including the sintering and dissolution process (SDP) and powder metallurgy, have been explored to produce metal foams. However, challenges persist in achieving uniform pore sizes and distributions, especially at temperatures surpassing the base material’s melting point. To overcome this hurdle, simultaneous loading and heating during fabrication have been proposed, with spark plasma sintering (SPS) emerging as a viable solution. This study delves into the manufacturing of aluminum metal foam utilizing NaCl space holders via SPS, investigating variations in space holder volume to analyze pore morphology and porosity. Additionally, the mechanical properties of the resulting foams are examined, providing valuable insights into the potential of SPS for crafting aluminum metal open foams with tailored properties. Porosity analysis, conducted through X-ray micro CT, reveals porosity ranging from 55 to 70% in metal foams with NaCl space holder volume fractions of 60 to 80%. Notably, a maximum energy absorption capacity of 23 MJ/mm3 is achieved in a metal foam with 57% porosity. S1 (40% NaCl) had lower porosity, smaller pore sizes, and thicker pore walls, buckling in the middle with minimal pore collapsibility and crack initiation at the edges. In contrast, the sample with more than 40% NaCl had higher porosity and thinner pore walls, resulting in greater collapse and energy absorption.

Internal Y-shaped bifurcation has been proved to be an advantageous way on improving thermal performance of microchannel heat sinks according to the previous research. Metal foams are known due to their predominate performance such as low-density, large surface area, and high thermal conductivity. In this paper, different parameters of metal foams in Y-shaped bifurcation microchannel heat sinks are designed and investigated numerically. The effects of Reynolds number, porosity of metal foam, and the pore density (PPI) of the metal foam on the microchannel heat sinks are analyzed in detail. It is found that the internal Y-shaped bifurcation microchannel heat sinks with metal foam exhibit better heat transfer enhancement and overall thermal performance. This research provides broad application prospects for heat sinks with metal foam in the thermal management of high power density electronic devices.

<div class="htmlview paragraph">The use of composite materials in the automotive industry has become increasingly widespread. With this increase in use, techniques for non-destructive testing (NDT) have become more and more important. Various optical NDT inspective methods such as holography, moiré techniques, and shearography have been used for material testing. Among these methods, shearography appears to be most practical. Shearography has a simple optical setup due to its “self-referencing” system, and it is relatively insensitive against rigid-body motions. Measurements of displacement derivatives, and thus strain directly, rather than the displacement itself is achieved through this method. Therefore shearography detects defects in objects by correlating anomalies of strain which are usually easier than correlating the anomalies of the displacement itself, as in holography.</div> <div class="htmlview paragraph">To date shearography has shown potential as a NDT tool for identifying defects in small structures. Applications of this technique in automotive inspection and production have been difficult because a high-powered laser typically needs to be used, which limits its application due to cost, and employee safety. In this presentation, a portable self-contained digital shearographic system using multi-laser diodes for the illumination source will be described. This system demonstrates a way to measure both small and large-scale structures with an economical portable shearographic system. Its application for NDT of composite materials in automotive and aerospace industries will be presented.</div>

Forced convection in finned metal foams: The effects of porosity and effective thermal conductivity

The large-scale use of sustainable energy necessitates the use of latent heat storage (LHS). This study aims to increase the melting performance of an LHS system by designing and optimizing the cesaro fins. To examine the melting behaviours of PCM (i.e., RT-82) in a finned LHS system, a 2-D melting heat transfer model is developed and numerically solved. As per literature, there is very literature including the NC (Natural Convection) and represents the coordination in fins, nanoparticles and metal foam. So, the impacts of natural convection, fin arrangement, nanoparticles and metal foam are explored for the Fourier number variations from 0.014 to 0.158 at a constant Stefan number of 0.20. The dynamic temperature distribution, as well as the natural convection and fin arrangement, are investigated to determine how phase change material melts over time by considering the non-thermal equilibrium between metal foam and PCM/nanoPCM. The findings illustrate that natural convection has a significant effect on melting behaviours in the LHTES (Latent Heat Thermal Energy Storage) system, with a 26.8% increase in melting/charging rate as compared to the situation without NC. The LHTES system with improved fin structure (i.e., Type-3) and increased number of fins (i.e., Type-5) configurations have more uniform temperature distribution and a higher melting rate by increasing the heat transfer cooperation between NC and thermal conduction. Low thermal conductivity causes poor performance in PCM (Phase Change Material) energy storage devices. The melting/charging of PCM in an LHTES system is greatly improved in this study by employing a porous metal foam (i.e., copper metal foam) or nanoparticle (i.e., Cu, CuO and Al2O3). The impact of nanoparticle volume fraction and metal foam porosity on the LHTES system's melting/charging performance is also investigated using the enthalpy-porosity technique. According to the results, PCM's melting/charging time is lowered by 63.4% when nanoparticles are mixed in and incorporated with metal foam for the Fourier number varies from 0.014 to 0.158 at a constant Stefan number of 0.20. PCM melting/charging time decreased when the metal foam porosity decreased or increased in the volume fraction of nanoparticles. High porosity metal foams with low volume fractions of nanoparticles can increase melting performance since it assures minimum PCM volume and increases natural convection.

Development of materials in automotive industries plays an important role in order to retain the safety, performance and cost. Metal foams are one of the idea to evolve new material in automotive industries since it can absorb energy when it deformed and good for crash management. Recently, new technology had been introduced to replace metallic foam by using aluminium foam sandwich (AFS) due to lightweight and high energy absorption behaviour. Therefore, this paper provides reliable data that can be used to analyze the energy absorption behaviour of aluminium foam sandwich by conducting experimental work which is compression test. Six experiments of the compression test were carried out to analyze the stress-strain relationship in terms of energy absorption behavior. The effects of input variables include varying the thickness of aluminium foam core and aluminium sheets on energy absorption behavior were evaluated comprehensively. Stress-strain relationship curves was used for energy absorption of aluminium foam sandwich calculation. The result highlights that the energy absorption of aluminium foam sandwich increases from 12.74 J to 64.42 J respectively with increasing the foam and skin thickness.

In this paper, coupling the air jet impingement and the copper metal foam above flowing liquid film were employed to enhance the heat transfer. The thickness of flowing liquid film can be controlled owing to the application of the metal foam above the film, and its solid matrix extends the air-liquid-solid interface of heating surface. The evaporated water can be supplied by the capillary force in the porous layer. The experiments were conducted to investigate the performances of the flowing liquid film with inserted porous layer subjected to impinging jet air. The air jet velocity, the flow rate and thicknesses of the liquid film as well as the porosity of metal foam influence the surface temperature of heated wall and the corresponding local heat transfer coefficient greatly. The change ratios of heat transfer coefficient due to the above factors were presented. More cooling can be obtained on the heated wall in the flowing liquid film with inserted porous layer subjected to impinging jet air while the higher liquid film velocity and air jet velocity, the thinner liquid film and the lower porosity of metal foam occur.