Porous Block Research Articles

Porous Monolithic Perovskite Structures for High-Temperature Thermochemical Heat Storage in Concentrated Solar Power (CSP) Plants and Renewable Electrification of Industrial Processes

A novel approach towards thermal energy storage of surplus renewable energy (RE) is introduced via a hybrid thermochemical/sensible heat storage concept implemented with the aid of porous structures made of redox metal oxides, capable of reversible reduction/oxidation upon heating/cooling in direct contact with air, accompanied, respectively, by endothermic/ exothermic heat effects and demonstrating fully reversible dimensional changes under cyclic operation. The proposed modular storage units can be heated during the day to a level exceeding the metal oxide’s reduction onset temperature either by hot air streams from air-operated Concentrated Solar Power (CSP) tower plants or via surplus/cheap RE-electricity from photovoltaics, wind, or other renewable sources (“charging”/energy storage step). When this RE sources become non-available or upon demand, the fully charged system can transfer its energy to a controlled airflow that passes through the porous oxide block and initiates the exothermic oxidation of the reduced metal oxide. Thus, a hot air stream is produced which can be used to provide electricity or exploitable heat for industrial processes. The present work elaborates on the operating principles and the potential application of this concept and reports progress in the preparation and shaping of reticulated porous ceramics (RPCs also known as “ceramic foams”) from CaMnO3-based perovskite compositions and their preliminary testing with respect to cyclic reduction-oxidation.

Solar-Adaptive Cooling Blocks Composed of Recycled Fabric.

Radiative cooling technologies have had a significant impact on advancing carbon neutrality efforts by significantly improving the passive cooling efficiency. The tandem of conduction and radiation enables solar-adaptive radiative cooling through the insulating effect of materials along with solar absorption, which affects the thermal state of materials and enhances radiative thermal transfer from the surface under solar irradiation. This enhancement is achieved by utilizing the porous polymeric structure of materials, which facilitates improved conduction pathways along with solar reflectance, while maintaining the effective emission of thermal radiation. In this particular scenario, blocks, which were made of recycled fibers, offer a great opportunity as solar-adaptive cooling materials, enabling their easy deployment for cooling applications. Herein, we have fabricated a porous block using fiber wastes that combines strong solar reflectance (92%) at the 1 μm region and high thermal infrared emittance (∼75%) at the 10 μm region. The combination of effective solar reflection and thermal infrared emission allows the fiber block to achieve a high cooling performance of approximately 68 W/m2 under solar irradiation. In addition, the fiber block works effectively for insulation during the night, thereby enhancing its heat retention capabilities. The economic and environmental advantages of the fiber block make it a cost-competitive and sustainable choice for near-market cooling technologies. This design is anticipated to expand the practical application range of passive cooling.

Assembly of Chitosan/Caragana Fibers to Construct an Underwater Superelastic 2D Layer-Supported 3D Architecture for Rapid Congo Red Removal.

Developing environmentally friendly bulk materials capable of easily and thoroughly removing trace amounts of dye pollutants from water to rapidly obtain clean water has always been a goal pursued by researchers. Herein, a green material with a 3D architecture and with strong underwater rebounding and fatigue resistance ability was prepared by means of the assembly of biopolymer chitosan (CS) and natural caraganate fibers (CKFs) under freezing conditions. The CKFs can randomly and uniformly distribute in the lamellar structure formed during the freezing process of CS and CKFs, playing a role similar to that of "steel bars" in concrete, thus providing longitudinal support for the 3D-architecture material. The 2D layers formed by CS and CKFs as the main basic units can provide the material with a higher strength. The 3D-architecture material can bear the compressive force of a weight underwater for multiple cycles, meeting the requirements for water purification. The underwater compression test shows that the 3D-architecture material can quickly rebound to its original shape after removing the stress. This 3D-architecture material can be used to purify dye-containing water. When its dosage is 3 g/L, the material can remove 99.65% of the Congo Red (CR) in a 50 mg/L dye solution. The adsorption performance of the 3D architecture adsorbent for CR removal in actual water samples (i.e., tap water, seawater) is superior than that of commercial activated carbon. Due to its porous block characteristics, this material can be used for the continuous and efficient treatment of wastewater containing trace amounts of CR dye to obtain pure clean water, meaning that it has great potential for the effective purification of dye wastewater.

Mechanisms and advancements in microwave-enhanced CO2 mineralization of lightweight porous concrete

Lightweight porous concrete (LPC) typically exhibits low early strength, which can be addressed by enhancing early strength through carbon dioxide (CO2) mineralization curing while achieving permanent CO2 sequestration. The efficacy of this process relies on maintaining optimal moisture levels. This study investigates the influence of moisture content on the performance of solid waste-based lightweight porous concrete blocks (RSFAC) subjected to microwave heating pretreatment. Moisture levels were adjusted to 10%, 20%, 30%, and 40% (initial water-to-cement ratio of 45.4%) before undergoing mineralization curing within an environment set at a temperature of 20 °C, relative humidity 75%, and a CO2 concentration of 40% for a duration of 0.5 h. The impact of moisture content on RSFAC's compressive strength, carbon sequestration rate, mineralization products, and microstructure was evaluated. Results indicate that compared to conventional oven pretreatment methods requiring nearly 10 h, microwave pretreatment technology achieves equivalent water content within just 50 min, significantly reducing the time needed for mineralization pretreatment. RSFAC, when pretreated with microwave heating, outperforms untreated samples (Ref-0 and Ref-1) in terms of compressive strength and carbon sequestration efficiency. Optimal performance was observed at a moisture content level of 30%, with the highest recorded compressive strength achieved at 1, 3, and 7 d respectively. At the curing age of 7 d, the compressive strength reached up to 2.32 MPa while the carbon sequestration rate reached approximately 11.61%. Furthermore, aragonite and calcite (tetrahedral and hexahedral), without poorly crystalline spherulites, were identified as the main crystalline CaCO3 generated by RSFAC under this specific moisture content condition; pores larger than 50 nm served as primary reaction sites for RSFAC mineralization curing, whereas there was a significant increase in pore proportion with sizes less than 20 nm after filling with mineralization products.

Mechanism of the rapid generation of superheated and saturated steam using a water-containing porous material

Superheated steam (SHS) is employed in various fields for everyday activities and industrial production, e.g., drying, cleaning, and reaction engineering. Although a facile method for realizing rapid SHS and saturated steam generation from water-containing porous materials has been proposed, with a second order start-up/cut-off response time and high energy utilization efficiency, the mechanism of this rapid SHS generation has not been clarified despite the proposition of a two-step process, including heating-based evaporation beneath the wire heater and reheating in the flow path. In this study, further experiments were conducted to separately consider both heating processes. The steam temperature directly beneath the wire heater correlated well with the film temperature, which is equal to the average temperature of the wire heater and the saturation temperature of the surface of the porous material. The measurement results of the temperature distribution inside the porous material block as well as the results of the electrical resistance directly beneath the wire heater revealed that no dry-out area was formed directly beneath the wire heater during SHS generation. Further, the three-dimensional laser scanning results revealed significant roughness on the surface of the porous material. The narrow gap, which was formed between the wire heater and the surface of the porous material, was critical to SHS generation, and the detailed mechanism was presented.

Numerical modeling of wave interaction with a porous floating structure consisting of uniform spheres

Porous materials are increasingly being used in the design of floating structures in coastal and ocean engineering, but there is a lack of numerical tools that can aid in the design of a movable floating porous structure. To close this gap, the existing volume-averaged numerical model for flow interacting with a fixed porous body was extended to floating scenarios by (1) using the relative velocity in the porous friction force, (2) calculating rigid body motion using volume integral of porous body force, and (3) modifying a dynamic mesh algorithm for a mobile porous body. As a demonstration, the developed model was applied to a porous floating structure consisting of cubically packed uniform spheres. Two sets of model applications were involved. The first set considered three-dimensional flow around a fixed porous block placed beneath the free surface. The measured total force on the block under wave or steady flows was predicted accurately with an error less than 10%. The second set involved a two-dimensional wave interacting with a floating porous block representing a breakwater. For free-floating conditions, the model can accurately predict the dynamic response of the structure, including the time varying movement of its rigid body and the mean drift. For mooring-restrained conditions, the mooring force and wave transmission coefficients were also predicted well with an error less than 20%. The proposed numerical approach can be applied to other floating structures with a rigid volumetric porous body. Future research is also required to study the microscopic pore flows, upon which more detailed parameterization of the porous media can be derived.

Physics-informed neural network for turbulent flow reconstruction in composite porous-fluid systems

This study explores the implementation of physics-informed neural networks (PINNs) to analyze turbulent flow in composite porous-fluid systems. These systems are composed of a fluid-saturated porous medium and an adjacent fluid, where the flow properties are exchanged across the porous-fluid interface. The segregated PINN model employs a novel approach combining supervised learning and enforces fidelity to flow physics through penalization by the Reynolds-averaged Navier-Stokes (RANS) equations. Two cases were simulated for this purpose: solid block, i.e. porous media with zero porosity, and porous block with a defined porosity. The effect of providing internal training data on the accuracy of the PINN predictions for prominent flow features, including flow leakage, channeling effect and wake recirculation was investigated. Additionally, L2 norm error, which evaluates the prediction accuracy for flow variables was studied. Furthermore, PINN training time in both cases with internal training data was considered in this study. Results showed that the PINN model predictions with second-order internal training data achieved high accuracy for the prominent flow features compared to the RANS data, within a 20% L2 norm error of second-order statistics in the solid block case. In addition, for the porous block case, providing training data at the porous-fluid interface showed errors of 18.04% and 19.94% for second-order statistics, representing an increase in prediction accuracy by 7% compared to without interface training data. The study elucidates the impact of the internal training data distribution on the PINN training in complex turbulent flow dynamics, underscoring the necessity of turbulent second-order statistics variables in PINN training and an additional velocity gradient treatment to enhance PINN prediction.

Nanoscopic catalyst-loaded porous metal oxide hollow frameworks using porous block copolymer templates for high performance formaldehyde sensors

Porous and hollow nanostructures functionalized with nanoscopic catalysts have attracted considerable interest in a wide range of applications depending on surface reactions. In this study, we present an efficient and versatile synthetic strategy of porous metal oxide hollow frameworks (HFs) decorated with noble metal nanoparticles (NPs). The key lies in the use of porous and bicontinuous polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) microparticles as templates, which feature pores on the order of several hundred nanometers in size. Homogeneous Pt loading on the surface of the porous microparticles is achieved through the preferential adsorption of Pt precursors onto the P4VP block via electrostatic interactions. Subsequent SnO2 thin film deposition and calcination ultimately yield honeycomb-like SnO2 HFs with macropores and uniform distribution of Pt NPs. The Pt NP-loaded SnO2 HFs exhibit exceptional formaldehyde (HCHO) sensing capabilities, characterized by remarkable sensitivity (31.4 at 5 ppm), rapid response time (4.7 s at 5 ppm), ultra-low detection limit of 10 ppb, and remarkable cross-selectivity. These outstanding features result from their high surface area, gas permeability within porous hollow structures, and well-dispersed Pt NPs, which catalytically activate the sensor. Our study provides great promise for advancing surface catalytic reactions due to their exceptional surface area and gas permeability, paving the way for future applications.

Reconstruction of unstable ankle charcot deformity using a 3-D printed titanium porous block and hindfoot nail – A case report

Charcot neuroarthropathy (CN) of the ankle joint can cause marked bone resorption of the talus resulting in severe deformity and instability. The utilisation of a 3-D printed bespoke titanium porous block that allows the use of an intramedullary calcaneo-tibial nail is an attractive option in such cases that has been reported for use in post-trauma deformities, following tumour resections, in avascular necrosis of talus and for revision of failed total ankle replacements, however has not previously been reported for Charcot ankle reconstructions. We present a novel case and surgical technique illustrating the use of a 3-D printed titanium porous block and hindfoot nail for reconstruction of a deformed and unstable Charcot hindfoot.

Porous block copolymer films with self-adjustable optical transmittance and passive radiative cooling

Porous block copolymer films with self-adjustable optical transmittance and passive radiative cooling

Comparison between tritium breeders with pebble bed and Gyroid block configurations using numerical investigation: Flow behavior and heat transfer performance

This study proposed using a Gyroid structure, a type of triply periodic minimal surface (TPMS), to replace conventional pebble bed configurations and address drawbacks such as inherently low packing fractions, extensive stress concentrations, high flow resistance, and low thermal conductivity. The feasibility of the Gyroid block configuration was evaluated by comparing it with a pebble bed configuration regarding the flow behaviors and heat transfer performance. The flow behavior of the porous block configuration was superior to that of the pebble bed configuration. At the same inlet velocity of 0.1–0.2 m/s, the porous block configuration had a ∼56 % higher average flow velocity and only half the pressure drop. The convective heat transfer coefficient and Nusselt numbers in the porous block configuration were 56–84 % and 2.6–3.1 times higher, respectively, than those in the pebble bed configuration. The effective thermal conductivity of the porous block configuration increased by ∼18 % at an inlet velocity of 0.15 m/s and a temperature of 773–1173 K. This study preliminarily verified the feasibility of the Gyroid structures for tritium breeders in engineering applications and is anticipated to provide new opportunities for the design of tritium breeders with higher lithium densities, remarkable flow behavior, and outstanding thermal performance.

Macroscopic modeling of urban flood inundation through areal-averaged Shallow-Water-Equations

An areal-averaged form of classical Shallow-Water-Equations is developed in conjunction with Finite-Volume-Method for capturing sub-grid bed variation. The averaging mechanism treats sub-grid obstacles through depth-dependent-area-averaged porosity at the macroscopic level. This porosity assumes a binary distribution (0,1) for a resolution fine enough to treat bed-variation separately, resulting in convergence of the developed framework to classical form. An attempt has been made to incorporate the unresolved fine-scale flow-information (e.g., micro-scale and cross-scale interaction components) in terms of the macroscopic variables through a non-linear closure model. An augmented approximated Riemann solver incorporates varying source–sink terms within interfacial fluxes along with discontinuous porosity and bed variation. The model is applied to three test-cases ranging from wave-interaction with trapezoidal porous block to dam-break flows through obstacle(s) with varying grid configurations. The coarse-scale formulation, along with closure, produces a reasonably accurate solution with minimal computational overhead.

Aqueous arsenic (III) removal using a novel solid waste based porous filter media block: Traditional and machine learning (ML) approaches

Arsenic (As) contamination of groundwater is one of the main obstacles preventing people from having easy access to potable water. Gypsum-based a porous filter media block (PFMB) made with moringa bark was proposed to remove arsenic (III) from aqueous solutions. The adsorption isotherms using Langmuir (R2 = 0.976) and Freundlich (R2 = 0.967) and kinetics using pseudo-first and second order and intraparticle diffusion models were achieved. The removal rates of PFMB using 10 g/L in batch experiments were found to be 98.4 % and 94.2 % for 0.50 and 1.0 ppm, respectively. The efficiency was evaluated by varying the material composition, pH, and experimental conditions using a machine learning model with an R2 = 0.95. A new approach to forecasting adsorption capacity based on material composition and experimental data allows the effective determinate to be found from a wider perspective. The model explanation with shapley additive value (SHAP) and partial dependence plots (PDP) showed the initial concentration, and time were the most influential factors in the adsorption process. Arsenic (III) adsorption on the innovative composite material appears promising, which will ensure the reuse and effective disposal of solid waste. ANN can be used to evaluate and predict new conditions without lab experimentation.

Numerical study on the suppression of liquid sloshing with a square porous block

Liquid sloshing is an urgent engineering issue with the increasing volume of the membranes used in floating liquefied natural gas (FLNG) facilities. Development of an appropriate method to reduce the liquid sloshing in the tank is a significant problem. Therefore, this study numerically analyzed the mechanism of the suppression of liquid sloshing under shallow water conditions by a square porous wall structure. A numerical model for sloshing in a rectangular tank with a porous block was established and validated. The effect of the square porous block on the local impact and global load was systematically studied. The square porous block effectively suppresses the kinematic free surface before impact on the sidewall and decreases the temporal and spatial distribution of the impact pressure along the sidewall. Furthermore, the overall force of the sidewall was reduced significantly by 56.10%, and the global moment of the tank was decreased by 33.38%. The porous block suppresses the liquid sloshing in the tank by acting as friction damping to dissipate the liquid energy and forming air cushion effect to reduce the impact pressure. Therefore, a reasonable arrangement of porous blocks in the tank can significantly improve the anti-sloshing performance to avoid damage to the tank structure.

Two-dimensional counter-current capillary imbibition of a wetting phase into a partially submerged porous cylindrical matrix block

The purpose of this study is to address the two-dimensional counter-current capillary dominant imbibition of a wetting phase into a water-wet porous cylindrical matrix block partially submerged in the wetting phase. A two-dimensional unsteady-state diffusion equation is used to model the process. The governing equation is solved using a combination of the Laplace and the finite Fourier sine transforms to find and analyze the solutions for the normalized water saturation and the volume of the imbibed wetting phase. The results reveal that the volume of the imbibed wetting phase and the capillary diffusion shape factor for a partially submerged matrix block are significantly lower compared to those of a fully submerged matrix block, highlighting the overestimation of imbibed volume using available models based on full immersion in the wetting phase. It has been observed that the volume of the imbibed wetting phase increases over time until reaching a state of equilibrium. In the case of a partially submerged matrix block, the shape factor is inversely proportional to the square root of time (σ ∼ 1/t) during the early time and decreases sharply as the imbibed wetting phase reaches an equilibrium. In the case of a fully submerged matrix block, the shape factor is inversely proportional to the square root of time (σ ∼ 1/t) during the early time and later reaches a pseudo-steady-state value. The proposed model, along with the findings obtained, advances our understanding of capillary imbibition in porous media.

Mixed convection heat transfer in a partial porous layered split lid-driven wavy wall cavity with Cu–H2O nanofluid

This numerical study investigates mixed convection heat transfer in a two-dimensional irregularly-shaped enclosure with a nanofluid-saturated porous medium. The enclosure has wavy vertical walls, a centered triangular block, and a lid split into two regions moving in opposite directions. Transport equations are solved using the finite element method under varied Darcy (10−5 to 10−1), Reynolds (50 to 200), Richardson (0.1 to 10), amplitude (0 to 0.2), and nanoparticle volume fraction (0 to 0.1) numbers. Results demonstrate the combined effects of forced convection from lid motion and natural convection from temperature differences significantly enhance heat transfer. The wavy walls induce secondary flows and periodic disruption of thermal boundary layers. Increasing Darcy number enables deeper penetration into the porous block. Copper nanoparticles incrementally improve conductive heat transfer. Richardson number effects are more prominent at higher Reynolds numbers as buoyancy forces influence vertical convection. This study provides novel insights into synergistically utilizing wavy geometries, nanofluids, porous media, and active pumping for optimizing heat transfer in irregular enclosures for electronics cooling and thermal management.

Data-driven modal analysis of turbulent momentum exchange and heat transfer in composite porous fluid systems

This paper investigates the dynamics governing turbulent momentum exchange and heat transfer between pore flow within porous media and the turbulent flow passing over it. Employing high-fidelity pore-scale large eddy simulation, our investigation explores the fundamental mechanisms driving these phenomena. Modal analysis based on snapshot proper orthogonal decomposition (POD) is employed to quantify the modes of interaction between porous and non-porous regions, providing a comprehensive understanding of the underlying processes. Spatial and temporal modes reveal the existence of localized flow structures at the pore scale, contributing to time-varying patterns of information exchange. At the commencement of the porous block, the mean flow (Mode = 0) from the porous to non-porous region is the dominant mechanism in momentum exchange and heat transfer. This mode facilitates convective heat transfer from the porous to the non-porous region through upward and forward flow movements, showcasing positive flow leakage. In addition to the mean flow, the turbulent flux inherent in alternate POD modes (Mode ≠ 0) plays a substantial role in information propagation, influencing diverse directions. Spatial modes, complemented by statistical analysis, uncover a significant likelihood of observing negative vertical velocity values in the wake of the porous ligaments at the porous-fluid interface, indicative of negative flow leakage. This negative flow leakage precisely corresponds to the local penetration of fluid from the non-porous region into the porous region. Furthermore, our study reveals that information exchange via turbulence fluctuations manifests through complex outward and inward interactions in regions characterized by substantial positive flow leakage. Notably, these regions exhibit a distinct tendency for high-momentum streamwise-oriented flow to migrate outward from the porous region into the non-porous region (outward interactions). Conversely, inward interactions arise in these regions when the instantaneous magnitude of positive flow leakage is smaller than the mean value of positive flow leakage, emphasizing the pulsating nature of positive flow leakage. Finally, the distribution of the Nusselt number highlights that more than 60% of total heat transfer occurs within the initial one-third of the porous block length. Significantly, a notable portion of the porous ligaments experiences insufficient cooling due to positive flow leakage, underlining the critical implications of these findings for the understanding of turbulent momentum exchange and heat transfer in a composite porous-fluid system.

Exploration of Clean Water Provision Endeavors in Residential Facilities for Construction Workers within the National Capital Development Area (IKN), Indonesia

Clean water is one of the basic needs to support human life. As the population grows, the need for clean water also increases. In the development of the National Capital area in North Penajam Paser, a lot of clean water will be needed. The study aims to find out alternative steps that will be taken to increase the fulfillment of clean water needs in the construction area of flats housing construction workers (HPK) in the National Capital Region (IKN) North Penajam Paser Regency, East Kalimantan Province, Indonesia. The study was carried out in the construction area of flats housing construction workers in the National Capital Region, North Penajam Paser Regency, East Kalimantan Province, Indonesia. The data collected is in the form of qualitative data, namely a description of the study location in general, and quantitative data: number of residents, water needs per person, number of flats for worker housing, and rain conditions in the study area. The techniques used to collect data that are appropriate to the object of study are observation, interviews, institutional visits, and literature review. The analytical methods used are: (1) a qualitative approach using descriptive analysis which describes the existing conditions of the study area, (2) analysis of population projections and (3) analysis of clean water supply. The study results in a show that efforts to provide clean water in HPK IKN can be done other than dams and reservoirs, namely by harvesting rainwater through infiltration wells, rainwater collection ponds, bio pore absorption holes, rain gardens, porous paving blocks, and storage reservoirs.

Effect of PMMA pore former on mechanical strength and performance of glass fibre metal-bonded porous diamond blocks with Cu–Sn–Ti solder alloys

To develop a metal-bonded diamond tool that does not require frequent dressing during grinding, a novel glass fibre metal-bonded porous diamond block is proposed. The effect of the content percentage and particle size of polymethyl methacrylate (PMMA) pore formers on the porosity of porous diamond blocks was investigated. The Vickers hardness and bending strength of the porous blocks with and without diamonds were tested. Wear tests were performed on the porous diamond blocks. The results show that an increase in the PMMA content (1.75–9.45 wt%) caused an increase in the porosity (2.8 %–22.9 %) and a decrease in the bending strength (8.6 %–71.9 %) and Vickers hardness (22.1 %–54.3 %), compared to those of the blocks without PMMA. An increase of PMMA size (20–40 μm diameter) caused an increase in the porosity (2 %–11.6 %), and a decrease in the bending strength (34.1 %–42.7 %) and Vickers hardness (23.7 %, 40.5 %), compared to those of the blocks without PMMA. However, excessively large PMMA particles (50–70 μm diameter) caused a decrease in the porosity and an increase in the bending strength and Vickers hardness. Increasing the porosity of the diamond blocks appropriately can reduce the need for frequent dressing and enhance the SiC removal rate. However, excessive porosity tends to accelerate diamond wear, leading to a decrease in the SiC removal rate.

Stereolithography and gelcasting of Li2TiO3 block breeders with a Gyroid structure: Slurry optimization and performance evaluation

This study proposes porous block structures as a viable alternative to conventional pebble bed structures, aiming to overcome the structural drawbacks including low packing fractions, extensive stress concentrations, and low thermal conductivity. To validate the feasibility of the porous block structures, Gyroid Li2TiO3 block breeders were prepared by the hybrid process of stereolithography and gelcasting. The resulting Gyroid Li2TiO3 block breeders, measuring ∼18.8 × 18.8 × 18.8 mm3, achieved a high packing fraction of ∼78.8% through optimized slurry and sintering at 1100 °C for 3 h. These Gyroid Li2TiO3 block breeders exhibited clear contours, integrated channels, a compressive strength of 8.78 MPa, and a low isotropic sintering shrinkage of ∼6%. The hybrid process demonstrated enormous advantages over the reported 3D printing for the preparation of porous block breeders with low shrinkage and large-sized dimensions. This study offers an effective avenue for the manufacture of porous block breeders with tunable tritium-releasing channels and large-sized configurations.