Foam Porosity Research Articles

Flow Boiling Analysis for HFE‐7100 in a Vertical Porous Tube

ABSTRACTMuch recent research has focused on dielectric fluids in engineering applications because of their physical properties. In this study, the use of HFE‐7100 as a working fluid in a porous pipe exposed to thermal conditions like solar radiation conditions in Baghdad city was studied. The two‐phase mixture model with Local Thermal Non‐Equilibrium assumption was applied to analyze the flow boiling of a subcooled HFE‐7100 in a vertical pipe filled with high porosity metal foam. The Finite volume approach with MATLAB code was used to solve the governing equations like continuity, momentum based on Forchheimer‐extended Darcy model and energy equations. The results displayed that the heat transfer rises with the rise in pore density, porosity and the heat flux while the liquid saturation reduces with the raise in heat flux and pore density and the decrease in porosity of the metal foam. PPI effect is more effective at low porosity, as it increases the heat transfer coefficient by 101%, 95%, and 88% at 0.8, 0.9, and 0.95 porosity, respectively. But the effect of porosity is very small compared to PPI effect on the liquid saturation where it decreases by 4% when the porosity decreases from 0.95 to 0.85, while it decreases by 23% when the pore density increases from 10 to 110 PPI.

A study on porosity and mechanical properties of the open aluminum metal foam through spark plasma sintering SDP technique

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.

The Passive Flow Zinc Bromine System

This work demonstrates a minimal overhead storage technology exploiting, rather than compensating for, the innate physical properties of the zinc-bromide system. Using two symmetric planar electrodes and a homogenous electrolyte, we present a ZnBr2 cell with over 50 Wh/L energy density, over 70% roundtrip efficiency, and a lifetime limited by cell sealing quality. The scaled cell cost is estimated to be $40/kWh.The zinc-bromide system is known for its theoretically low cost, long lifetime, and high energy density. However, resolving this theory to practice has been difficult in active flow systems. Classic design goals work to “correct” the physical chemistry of the ZnBr systems, including rigorous separation of the charged Zn and Br2 phases, active phase control of the Br2/water mixture, and forced convection to maximize power density. But balance-of-plant support of concentrated halide electrolytes, complexing required to create reliable Br2 miscibility, and secondary safety systems required when running bromine through forced convection through manifolds conspire to increase the CAPEX and OPEX of the ZnBr2 system while decreasing its reliability.We have previously demonstrated a “static” ZnBr2 system that follows a traditional unit cell design, where zinc plates upon a carbon current collector and Br2 reside in a carbon foam's porosity. Here we present our new designs, where we remove the complexity of the “cathode carbon foam,” replacing it with a simple carbon surface and augmenting it with a better understanding of the native stratification and mixing behaviors of the ZnBr2 electrolyte at different concentrations/state of charge. We will also present learnings of the mixing/settling behavior of the electrolyte as a function of concentration (effective SoC) and orientation, as well as the kinetics of bromine oxidation and consumption on simple carbon electrodes. Figure 1

Numerical Analysis of the Thermal Performance of a Hybrid Heat Sink Comprised of Perforated Foam Fins Embedded Within a Phase Change Material

ABSTRACTThis study presented a numerical model to evaluate a novel design of a hybrid heat sink incorporating perforated foam fins (PFFs) instead of solid fins (SFs) within a phase change material (PCM). This innovation is designed to enhance thermal performance in electronic cooling applications. The base of the heat sink was subjected to constant heat fluxes of 2, 3, and 4 kW/m2. The effect of the perforation location (top, center, and bottom) within the foam fin and foam porosities (0.85, 0.90, and 0.95) were investigated. The results showed that the hybrid PFF design demonstrably improved thermal efficiency compared to the SF configuration. This innovative approach offered three benefits: a significant reduction in overall heat sink weight, an augmentation of the thermal conductivity of PCM, and the intermixed molten PCM between the fins passages through perforations. The PFF heat sink extended the operational time by 6%–8% for the range of heat fluxes at SPT of 70°C and led to a 24.5% increase in PCM volume, compared to the SF configuration. Complete melting of the PCM in the PFF heat sink is observed at 29 min for the highest heat flux of 4 kW/m2, while the melting rates are 25% and 62% for the applied heat flux of 2 and 3 kW/m2. Perforation location within the foam fin (top, center, and bottom) achieved equivalent heat transfer capabilities, enabling design flexibility for perforation location. The PFF with a porosity of 0.85 demonstrated superior thermal performance.

High temperature in-situ 3D monitor of microstructure evolution and heat transfer performance of metal foam

High temperature in-situ 3D monitor of microstructure evolution and heat transfer performance of metal foam

Optimizing graphite-enhanced composite PCMs for superior thermal transport in shell and tube latent heat storage systems

Optimizing graphite-enhanced composite PCMs for superior thermal transport in shell and tube latent heat storage systems

Multi-objective optimization of metal foam parameters for enhanced performance of LHTES unit in shell-and-tube configurations

Multi-objective optimization of metal foam parameters for enhanced performance of LHTES unit in shell-and-tube configurations

Waste-to-resource: Employing lime mud as a foaming agent in glass foam manufacturing

Waste-to-resource: Employing lime mud as a foaming agent in glass foam manufacturing

Structure-property relationships of polydisperse open-cell foams: Application to melamine foams

The melamine foam presents a unique microstructure characterized by an interconnected network of solid struts, which form the edges and faces of high porosity open cells. This study investigates the influence of pore size distribution on acoustic properties for three commercially available melamine foams. Based on the measured transport parameters, a top-down approach is employed to determine the equivalent Kelvin-cell size corresponding to each transport parameter. The differences found in these equivalent pore sizes indicate that the mono-size model is not suitable for these materials, a difference from which a quantitative estimate of the level of polydispersity can be deduced (using macro-scale information). The polydispersity was confirmed from experimental evidence at micro-scale from the analysis of SEM images. Moreover, the measurements collected at micro-scale (average pore size and its standard deviation) can be used as input data to determine the transport and sound absorbing behavior of melamine foam samples from structure-property relationships available for open cell microstructures. This work provides evidence that the polydispersity of melamine foams should be taken into account to obtain an accurate and consistent picture of microstructure and transport properties of such open cell high porosity foams.

Polycaprolactone-based shape memory foams as self-fitting vaginal stents

There is an urgent critical need for a patient-forward vaginal stent that can prevent debilitating vaginal stenosis that occurs after pelvic radiation treatments and vaginal reconstruction. To this end, we developed a self-fitting vaginal stent based on a shape-memory polymer (SMP) foam that can assume a secondary, compressed shape for ease of deployment. Upon insertion, the change in temperature and hydration initiates foam expansion to shape fit to the individual patient and restore the lumen of the stent to allow egress of vaginal secretions. To achieve rapid actuation at physiological temperature, we investigated the effect of architecture of two photocurable, polycaprolactone (PCL) macromers. Star-PCL-tetraacrylate displayed a reduced melting temperature as compared to a linear-PCL-diacrylate. Upon fabrication into high porosity foams with emulsion-templating, both compositions displayed shape fixity (>90 %) in a crimped, temporary shape. However, only the PCL star-foams displayed shape recovery (∼84 %) at 37 °C with expansion back to its permanent shape. A custom mold and curing system were then used to fabricate the PCL star-foams into hollow, cylindrical stents. The stent was crimped to its temporary insertion shape (50 % reduction in diameter, OD ∼ 11 mm) with a custom radial crimper and displayed excellent shape fixity for deployment (> 95 %) and shape recovery (∼ 100 %). To screen vaginal stents, we developed a custom benchtop pelvic model that simulated vaginal anatomy, temperatures, and pressures with an associated computational model. The crimped SMP vaginal stent was deployed in the model and expanded to walls of the canal (∼70 % increase in cross-sectional area) in less than 5 min after irrigation with warm water. The vaginal stent demonstrated retention of vaginal caliber with less than 10 % decrease in cross-sectional area under physiological pressures. Collectively, this work demonstrates the potential for SMP foams as self-fitting vaginal stents to prevent stenosis and provides new open-source tools for the iterative design of other gynecological devices. STATEMENT OF SIGNIFICANCE: Vaginal stenosis, a painful narrowing of the vaginal canal, is a common complication after pelvic radiation therapy or reconstructive surgery. To address this clinical need, we have created a self-fitting vaginal stent from a shape-memory polymer foam. The stent compresses for easy insertion and then expands to adapt to each patient's anatomy to maintain an open vaginal canal and prevent stenosis. This innovative stent provides a patient-friendly solution that could make a significant difference for women undergoing pelvic treatments by reducing pain, aiding recovery, and improving quality of life.

Study on the Enhancement of Energy Storage Mechanism for Phase Change Materials by High Porosity Metal Foams: Numerical Simulation

Introduction: The findings of the study elucidated that as the porosity of copper foam diminished, the internal average temperature of the composite phase change material increased, concurrent with a reduction in the maximum average temperature differential and an enhancement in temperature homogeneity between the heating interface and the copper composite phase change material. Methods: Under the filling rate of this experiment, the heat transfer mechanism of copper composite phase change materials (CPCMs) was mainly heat conduction. Results: With the increase of porosity, the melting time of phase change materials shortened, and the change of natural convection ratio was more obvious. At the same melting time, the porosity decreased, and the pressure drop increased. Conclusion: When the porosity was 94 % and 96 %, the pressure drop was 1425.34 Pa/m and 1222.65 Pa/m, respectively, which was 37.01 % and 17.53 % higher than that when the porosity was 98 %.

The role of Voronoi catalytic porous foam in reactive flow for hydrogen production through steam methane reforming (SMR): A pore-scale investigation

The role of Voronoi catalytic porous foam in reactive flow for hydrogen production through steam methane reforming (SMR): A pore-scale investigation

Phase change heat storage and enhanced heat transfer based on metal foam under unsteady rotation conditions

Phase change heat storage and enhanced heat transfer based on metal foam under unsteady rotation conditions

Melting of PCM-graphite foam composites with contact thermal resistance: Pore-scale simulation

Melting of PCM-graphite foam composites with contact thermal resistance: Pore-scale simulation

Embedded Fluidic Sensing and Control with Soft Open‐Cell Foams

AbstractThe synthesis of soft matter intelligence with circuit‐driven logic has enabled a new class of robots that perform complex tasks or conform to specialized form factors in unique ways that cannot be realized through conventional designs. Translating this hybrid approach to fluidic systems, the present work addresses the need for sheet‐based circuit materials by leveraging the innate porosity of foam—a soft material—to develop pneumatic components that support digital logic, mixed‐signal control, and analog force sensing in wearables and soft robots. Analytical tools and experimental techniques developed in this work serve to elucidate compressible gas flow through porous sheets, and to inform the design of centimeter‐sized foam resistors with fluidic resistances on the order of 109 Pa s m−3. When embedded inside soft robots and wearables, these resistors facilitate diverse functionalities spanning both sensing and control domains, including digital logic using textile logic gates, digital‐to‐analog signal conversion using ladder networks, and analog sensing of forces up to 40 N via compression‐induced changes in resistance. By combining features of both circuit‐based and materials‐based approaches, foam‐enabled fluidic circuits serve as a useful paradigm for future hybrid robotic architectures that fully embody the sensing and computing capabilities of soft fluidic materials.

Performance investigation of metal foam coupled to phase change material as coolant of photovoltaic concentrator systems: Optimization and electrical efficiency analysis

Performance investigation of metal foam coupled to phase change material as coolant of photovoltaic concentrator systems: Optimization and electrical efficiency analysis

Effect of microstructure on the physicochemical characteristics of foam glass made by soda lime -CRT glasses and aluminium dross

Effect of microstructure on the physicochemical characteristics of foam glass made by soda lime -CRT glasses and aluminium dross

Numerical simulation of thermal performance of heat sink augmented with phase change material PCM integrated with solid and aluminum metal foam fins

AbstractThis 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.

A study on syntactic aluminum foams manufactured infiltrating sintered preforms of iron hollow spheres

A study on syntactic aluminum foams manufactured infiltrating sintered preforms of iron hollow spheres

Microstructure and performances of rigid polyurethane foam prepared using double‐effect baking powder as a foaming agent

AbstractThe preparation of rigid polyurethane foam with uniform pore size is extremely challenging. In this work, double‐effect baking powder was used as foaming agent, and rigid polyurethane foam with regular morphology was successfully prepared through semi‐prepolymerization. The rigid polyurethane foam apertures with regular morphology were controlled by the secondary release of CO2 when the content of baking powder is 0.30 part. Combined with theoretical calculation and experimental test, it is found that the particle size distribution, wall thickness, and hole shape are uniform, regular, thin, polygonal, and few broken holes. The compression strength, contact angle, and surface energy of the rigid polyurethane foam are 33.36 kPa, 109.6°, and 21.8 mJ/m2 after adding 0.20 part of double‐effect baking powder, respectively. By adjusting the amount of double‐acting baking powder, the porosity, mechanical properties and foam rate of the polyurethane foams could be significantly improved. Due to the molecular solvation effect, rigid polyurethane foams will deform in the water and oil due phase, but it can remain stable for a long time at room temperature without solvent. It provides a new method for the preparation of rigid polyurethane foam, which is expected to be widely used in transportation and other fields.Highlights Baking powder was firstly used as a foaming modifier for rigid polyurethane. Baking powder releases CO2 twice to ensure uniform structure of polyurethane cell. Rigid polyurethane foam has long‐term stability and regular, uniform cell holes. The porosity and mechanical properties of foams could be significantly improved. Foaming mechanism of rigid polyurethane using baking powder was firstly revealed.