Search Results (276)

The thermal response of Carbon Fiber Reinforced Thermoplastic (CFRTP) tapes under short-term localized heating is critical for automated manufacturing processes. Conventional homogenized models often overlook microstructural heterogeneities that can promote non-uniform heating and affect the quality of the consolidated part. In this work, we combine insights from infrared thermography with finite element simulations at the fiber scale built on micrographs extracted from real tapes to quantify the effect of individual heterogeneities—including surface roughness, thickness variation, fiber agglomeration, and porosity—on thermal propagation. Three modeling configurations were compared under identical conditions: a full microstructure model; a simplified geometry-aware model (where the real geometry is taken into the account, including the surface roughness and thickness variability, but the properties of the domain are considered as a homogeneous-equivalent material); and a homogeneous-equivalent baseline with flat borders and uniform thickness. Results show that porosity effects depend strongly on location and orientation: large, horizontally aligned pores near the heated surface produce the highest gradients. Surface roughness, on the other hand, exerts dominant effects on surface temperature non-uniformity with respect to thickness variation and fiber distribution. These findings demonstrate that accounting for microscale heterogeneities is essential to achieve more accurate, optimized, and application-tailored analyses of CFRTP tapes in advanced manufacturing. Full article

We construct a family of self-adjoint operators on the prime numbers whose entries depend on pairwise arithmetic divergences, replacing geometric distance with number-theoretic dissimilarity. The resulting spectra encode how coherence propagates through the prime sequence and define an emergent arithmetic geometry. From these spectra we extract observables such as the heat trace, entropy, and eigenvalue growth, which reveal persistent spectral compression): eigenvalues grow sublinearly, entropy scales slowly, and the inferred dimension remains strictly below one. This rigidity appears across logarithmic, entropic, and fractal-type kernels, reflecting intrinsic arithmetic constraints. Analytically, we show that for the unnormalized Laplacian, the continuum limit of its squared Hamiltonian corresponds to the one-dimensional bi-Laplacian, whose heat trace follows a short-time scaling proportional to $t^{-1/4}$. Under the spectral dimension convention $d_s=-2d\log \Theta /d\log t$, this result produces $d_s=1/2$ directly from first principles, without fitting or external hypotheses. This value signifies maximal spectral compression and the absence of classical diffusion, indicating that arithmetic sparsity enforces a coherence-limited, non-Euclidean geometry linking spectral and number-theoretic structure. Full article

Airplane cabin temperature is a critical environmental factor governing the safety and reliability of airborne equipment. Compared with measuring temperature, predicting temperature is more cost- and time-saving and can cover an extreme flight envelope. Physics-informed neural networks (PINNs) offer a promising prediction solution whose performance hinges on the availability of precise governing differential equations. However, building governing differential equations between flight parameters and cabin temperature is a great challenge, as it is comprehensively influenced by aerodynamic heat, avionic heat, and internal flow. To solve this, a new PINN framework based on “a priori monotonicity” is proposed. Underlying physical trends (monotonicity) from flight data are extracted to construct the loss function as a data-driven constraint, thus eliminating the need for any governing equations. The new PINN is developed to estimate the seven cabin temperatures of an unmanned aerial vehicle. The model was trained on data from four flight sorties and validated on another four independent sorties. Results demonstrate that the proposed PINN achieves a mean absolute error of 1.9 and a root mean square error of 2.6, outperforming a conventional neural network by approximately 35%. The core value of this work is a new PINN framework that bypasses the development of complex governing equations, which enhances its practicality for engineering applications. Full article

The strategic positioning of heating and cooling segments within complex non-rectangular geometries has emerged as a critical engineering challenge across multiple industries in thermal management systems for electronic components. This analysis presents a numerical inspection of buoyancy-driven convective flow and thermal transport mechnisms of nanofluids in a parallelogrammic porous geometry. A single discrete heating–cooling segment has been placed along the slanting surfaces of the geometry. The mathematical model is formulated utilizing Darcy’s law, incorporating the Tiwari and Das approach to characterize the thermophysical properties of the nanofluid. The governing model equations corresponding to the physical process are solved numerically using finite-difference-based alternating direction implicit (ADI) and successive line over-relaxation (SLOR) techniques. Computational simulations are performed for various parametric conditions, including different nanoparticle volume fractions ($\varphi =0$–$0.05$), Rayleigh numbers ($Ra={10}^1$–${10}^3$), and parallelogram geometry ($\alpha$) and sidewall ($\gamma$) tilting angles ($-{45}^{°}\le \alpha \le +{45}^{°}$ and $-{45}^{°}\le \gamma \le +{45}^{°}$), while examining the effect of discrete thermal locations. The results reveal a significant decrement in thermal transfer rates with an increasing nanoparticle concentration, particularly at higher Rayleigh numbers. The skewness of the parallelogrammic boundaries is found to substantially influence flow patterns and thermal transport characteristics compared to conventional rectangular enclosures. Further, the discrete placement of heating and cooling sources creates unique thermal plumes that modify circulation patterns within the domain. The predictions suggest profound insights for optimizing thermal management systems by employing nanofluids in non-rectangular porous configurations, with potential applications in geothermal energy extraction, electronic cooling systems, and thermal energy storage devices. Full article

Solvent-assisted steam-assisted gravity drainage (SA-SAGD) is an advanced hybrid oil recovery technique designed to enhance the extraction of heavy oil and bitumen. Unlike the conventional SAGD process, which relies solely on thermal energy from injected steam, SA-SAGD incorporates a coinjected solvent phase to improve oil mobility through the combined action of heat and mass transfer. This synergistic mechanism significantly reduces the demand for water and natural gas used in steam generation, thereby improving the energy efficiency and environmental sustainability of the process. Importantly, SA-SAGD retains the same well pair configuration as SAGD, meaning that its implementation often requires minimal modifications to existing infrastructure. This study explores the residual oil saturation following multi-component solvent coinjection in SA-SAGD using a linear sand pack model designed to emulate the properties and operational parameters of the Long Lake reservoir. Experiments were conducted with varying constant concentrations of cracked naphtha and gas condensate to assess their effectiveness in enhancing bitumen recovery. The results reveal that the injection of 15 vol% cracked naphtha achieved the lowest residual oil saturation and the highest rate of oil recovery, indicating superior solvent performance. Notably, gas condensate at just 5 vol% concentration outperformed 10 vol% cracked naphtha, demonstrating its effectiveness even at lower concentrations. These findings provide valuable insight into the phase behaviour and recovery dynamics of solvent–steam coinjection systems. The results strongly support the strategic selection of solvent type and concentration to optimise recovery efficiency while minimising steam consumption. Furthermore, the outcomes offer a robust basis for calibrating reservoir simulation models to improve the design and field-scale application of SA-SAGD, particularly in pilot operations such as those conducted by Nexen Energy ULC in the Athabasca Oil Sands. Full article

This study presents a comprehensive evaluation of levulinic acid purification schemes from a circular economy perspective, integrating resource-based indicators with economic and environmental metrics. Twelve alternatives, ranging from conventional distillation sequences to intensified hybrid systems, were assessed using indicators such as Relative Material Impact, total annual cost, Eco-Indicator 99, fuel demand, and CO₂ emissions. The novelty of this work lies in extending the assessment beyond purification infrastructure to include upstream systems that supply energy demand, such as fuel extraction and steam generation. The configurations considered incorporate thermal couplings, dividing wall columns, and decanters, which influence energy efficiency, process complexity, and resource depletion. Among these, the TDWS-D configuration (Thermally Coupled Double Dividing Wall Column System with Decanter) exhibits the highest values in DMR, TAC, and CO₂ emissions, driven by its elevated energy demand and complex infrastructure. Conversely, the TCS2 configuration (Thermally Coupled Sequence, featuring selective heat integration between distillation columns) achieves the lowest impact across all metrics, demonstrating that selective and strategic intensification (rather than maximalist design) can yield superior sustainability outcomes. Across all scenarios, the boiler stage was identified as the main contributor to material depletion, followed by fuel extraction and purification equipment. Notably, some conventional designs proved superior to intensified ones in terms of circularity, challenging the assumption that intensification inherently guarantees sustainability. Overall, the integration of circular economy indicators enables a multidimensional evaluation framework that supports more responsible and resource-efficient process design. Full article

As the global imperative to decarbonize infrastructure intensifies, wastewater treatment plants (WWTPs) are emerging as critical nodes for implementing circular and energy-positive solutions. Among these, thermal energy recovery from sewage sludge presents a transformative opportunity to reduce greenhouse gas (GHG) emissions, enhance energy self-sufficiency, and valorize waste streams. While anaerobic digestion remains the dominant stabilization method in large-scale WWTPs, it often underutilizes the full energy potential of sludge. Recent advancements in thermal processing, including pyrolysis, gasification, hydrothermal carbonization, and incineration with energy recovery, offer innovative pathways for extracting energy in the form of biogas, bio-oil, syngas, and thermal heat, with minimal carbon footprint. This review explores the physicochemical variability of sewage sludge in relation to treatment processes, highlighting how these characteristics influence thermal conversion efficiency and emissions. It also compares conventional and emerging thermal technologies, emphasizing energy yield, scalability, environmental trade-offs, and integration with combined heat and power (CHP) systems. Furthermore, the paper identifies current research gaps and outlines future directions for optimizing sludge-to-energy systems as part of net-zero strategies in the water–energy nexus. This paper contributes to a paradigm shift toward sustainable, decarbonized wastewater management systems by reframing sewage sludge from a disposal challenge to a strategic energy resource. Full article

This paper presents the development and evaluation of an autonomous solar dryer designed to enhance the drying efficiency of bee bread granules. In contrast to natural open-air drying, the proposed system utilizes solar energy in an oscillating operational mode to achieve a controlled and accelerated drying process. The dryer comprises a solar collector integrated into the base of the drying chamber, which facilitates convective heating of the drying agent (air). The system is further equipped with a photovoltaic panel to generate electricity for powering and controlling the operation of air extraction fans. The methodology combines numerical modeling with experimental studies, structured by an experimental design framework. The modeling component simulates variations in temperature (288–315 K) and relative humidity within a layer of bee bread granules subjected to a convective air flow. The numerical simulation enabled the determination of the following: the time required to achieve a stationary operating mode in the dryer chamber (20 min); and the rate of change in moisture content within the granule layer during conventional drying (18 h) and solar drying treatment (6 h). The experimental investigations focused on determining the effects of granule mass, air flow rate, and drying time on the moisture content and temperature of the granular layer of Bee Bread. A statistically grounded analysis, based on the design of experiments (DoE), demonstrated a reduction in moisture content from an initial 16.2–18.26% to a final 11.1–12.1% under optimized conditions. Linear regression models were developed to describe the dependencies for both natural and forced convection drying. A comparative evaluation using enthalpy–humidity (I-d) diagrams revealed a notable improvement in the drying efficiency of the proposed method compared to natural drying. This enhanced performance is attributed to the system’s intermittent operational mode and its ability to actively remove moist air. The results confirm the potential of the developed system for sustainable and energy-efficient drying of bee bread granules in remote areas with limited access to a conventional power grid. Full article

The increasing share of renewable energy sources in power grids demands greater load flexibility from thermal power plants. Circulating Fluidized Bed (CFB) combustion systems, while offering fuel flexibility and high thermal inertia, face challenges in maintaining hydrodynamic and thermal stability during load transitions. This study investigates partial flue gas recirculation (FGR) as a strategy to enhance short-term load flexibility in a 1 MW_th CFB pilot plant fired exclusively with solid recovered fuel. Two experimental test series were conducted. Under conventional operation, where fuel and fluidization air are reduced proportionally, load reductions to 86% and 80% led to operating regime shift. Particle entrainment from the riser to the freeboard and loop seal decreased, circulation weakened, and the temperature difference between bed and freeboard zone increased by 71 K. Grace diagram analysis confirmed that the system approached the boundary of the circulating regime. In contrast, the partial FGR strategy maintained total fluidization rates by replacing part of the combustion air with recirculated flue gas. This stabilized pressure conditions, sustained particle circulation, and limited the increase in the temperature difference to just 7 K. Heat extraction in the freeboard remained constant or improved, despite slightly lower flue gas temperatures. While partial FGR introduces a minor efficiency loss due to the reheating of recirculated gases, it significantly enhances combustion stability and enables low-load operation without compromising fluidization quality. These findings demonstrate the potential of partial FGR as a control strategy for flexible, waste-fueled CFB systems and supports its application in future low-carbon energy systems. Full article

Ti-bearing blast furnace slag (TBS), a byproduct of vanadium–titanium magnetite smelting, serves as an important secondary resource for titanium recovery. However, the complex mineralogical composition and finely dispersed nature of titanium in TBS present significant challenges for efficient extraction. This review systematically examines four major titanium extraction routes: hydrometallurgical leaching, pyrometallurgical smelting, molten salt electrolysis, and selective precipitation, focusing on their limitations and recent improvements. For instance, conventional acid leaching suffers from acid mist release, a colloidal formation that hinders titanium recovery, and waste acid pollution. The adoption of concentrated sulfuric acid roasting activation effectively suppresses acid mist emission and prevents colloidal generation. Pyrometallurgical approaches are hampered by high energy consumption and substantial carbon emissions, which can be alleviated through the use of gaseous reductants to enhance reaction efficiency and reduce environmental impact. Molten electrolysis faces issues such as polarization and undesirable dendritic deposition; these are mitigated by employing liquid metal cathodes integrated with vacuum distillation to achieve high-purity titanium products. Selective precipitation struggles with strict crystallization conditions and low separation efficiency, though advanced techniques like supergravity separation show improved extraction performance. We propose an integrated technical strategy termed “Online conditioning driven by waste heat-mineral phase reconstruction-directional crystallization-optimized liberation.” This approach utilizes the inherent waste heat of slag combined with electromagnetic stirring to enhance homogeneity and promote efficient titanium recovery, offering a sustainable and scalable solution for industrial TBS treatment. Full article

Carbon microspheres were prepared by microwave-assisted hydrothermal treatment, at 180 °C, of commercial carbohydrates (saccharose, glucose, and xylose) and xylose extract obtained from almond shells with varying synthesis parameters. When 1.6 M aqueous solutions of commercial carbohydrates were used, 2–10 μm carbon microspheres were obtained from saccharose after 15 min, while a longer amount of time (60 min) and the addition of acid medium (1% v/v H₂SO₄, 1% v/v H₃PO₄) were needed to obtain carbon microspheres from commercial xylose and glucose (≤ 1 μm). The higher reactivity of saccharose could be related to the formation, during heating, of fructose, which is more reactive than glucose and xylose. An increase in the acid concentration and in the carbohydrate concentration increased the formation and size of the microspheres. Comparative experiments with conventional heating did not produce a solid. Interestingly, when xylose extract obtained from almond shells was used, small carbon microspheres (1–3 μm) were obtained at a much lower concentration (0.2 M) and time (15 min) than with commercial xylose. This could be related to the acid medium used during extraction of xylose from the biomass. Activation of microspheres with CO₂ resulted in high-surface area materials (243–326 m²/g) with great potential as catalytic supports. Full article

Natural food colourants are gaining momentum in the food industry due to their clean-label appeal, safety, and potential health benefits. However, their practical application is often constrained by instability under environmental stressors such as pH fluctuations, heat, light, and oxygen. In response, both traditional and innovative strategies have emerged to improve pigment stability, with some studies reporting up to 50–80% retention of colour intensity under optimised conditions. Most existing research focuses on extraction, with limited emphasis on post-processing stability. This article reviews a wide range of food processing strategies aimed at enhancing the stability of natural pigments. It covers conventional and emerging approaches, including natural chemical stabilisers such as co-pigments, antioxidants, and metal ion chelators, physicochemical methods such as micro- and nanoencapsulation using biopolymers, and physical interventions involving drying technologies, particle size modification, and protective packaging. Modern technologies such as high-pressure processing, pulsed electric fields, ultrasound, and cold plasma are discussed as promising non-thermal alternatives, demonstrating 20–70% improvement in pigment retention compared to untreated controls. By integrating these diverse approaches, this article highlights current advancements, identifies knowledge gaps, and discusses future directions to support the development of stable, sustainable, and functional natural colourant systems for next-generation food products. Collectively, these approaches demonstrate significant potential to improve the performance and resilience of natural pigments in complex food systems. Full article

The growing demand for sustainable biorefinery approaches calls for efficient, environmentally benign strategies to valorize agricultural residues and ensure their complete utilization. This study explores the combination of deep eutectic solvents (DESs) and microwave heating technology as a greener process for the selective fractionation of agri-food waste residues in a zero-waste perspective. Within this framework, five representative biomasses were thoroughly investigated, namely brewer’s spent grain, raw and parboiled rice husks, rapeseed cakes, and hemp hurds. DES formulation was selected for its ability to solubilize and separate lignocellulosic components, enabling the recovery of a polysaccharide-rich fraction, lignin, and bioactive compounds. DES extraction was performed using both microwave heating and conventional batch heating, enabling a direct comparison of the two methods, the optimization of a more sustainable fractionation process, and the maximization of yields while preserving the functional integrity of the recovered fractions. A comprehensive characterization of the separated fractions was carried out, revealing that the two fractionation methods do not yield significant differences in the composition of the primary components. Moreover, a ¹³C CP-MAS NMR analysis of the recovered lignins demonstrates how this analytical technique is a real fingerprint for the biomass source. The results demonstrate the great potential of microwave DES-mediated fractionation as a mild, tunable, and sustainable alternative to conventional methods, aligning with green chemistry principles and opening new approaches for the full valorization of waste byproducts Full article

Globally, winery wastewaters (WWWs) are estimated to account for about 62.5 billion L annually (2021), with COD levels up to 300,000 mg O₂/L primarily attributed to residual ethanol, posing serious environmental concerns. Conventional treatments are effective in COD removal, but they often miss opportunities for energy recovery and resource valorization. This study investigates the aqueous phase reforming (APR) of ethanol-rich wastewater as an alternative treatment for both COD reduction and energy generation. Two scenarios were assessed: electricity and heat cogeneration (S1) and hydrogen production (S2). Process simulations in Aspen Plus^® V14, based on lab-scale APR data, provided upscaled material and energy flows for techno-economic analysis, life cycle assessment, and energy sustainability analysis of a 2.5 m³/h plant. At 75% ethanol conversion, the minimum selling price (MSP) was USD0.80/kWh with a carbon footprint of 0.08 kg CO₂-eq/kWh for S1 and USD7.00/kg with 2.57 kg CO₂-eq/kg H₂ for S2. Interestingly, S1 revealed a non-linear trade-off between APR performance and energy integration, with higher ethanol conversion leading to a higher electricity selling price because of the increased heat reactor duty. In both cases, the main contributors to global warming potential (GWP) were platinum extraction/recovery and residual COD treatment. Both scenarios achieved a positive energy balance, with an energy return on investment (EROI) of 1.57 for S1 and 2.71 for S2. This study demonstrates the potential of APR as a strategy for self-sufficient energy valorization and additional revenue generation in wine-producing regions. Full article

Physalis alkekengi L. has attracted widespread attention and cultivation due to its unique lantern-shaped fruit and various bioactivities. Existing studies have mainly focused on its fruit, while the calyx, despite its significant bioactivity, has long been neglected. In particular, research on the changes in polyphenol content and antioxidant activity during its drying process remains scarce. This study aimed to optimize the extraction process, comprehensively profile the polyphenol composition, and evaluate the effects of the drying temperature on the polyphenol content and antioxidant capacity in the calyx of Physalis alkekengi L. (CPAL). Ultrasound-assisted extraction (40 kHz, 300 W) combined with response surface methodology was used to optimize the extraction conditions. The optimized parameters were determined as a 49% ethanol concentration, a 42 mL/g liquid-to-material ratio, a 64 °C extraction temperature, and a 29 min extraction time. Under these settings, the yield reached 10.44 ± 0.16 mg GAE/g, exceeding that of the conventional heat reflux extraction method. Using high-resolution mass spectrometry, 63 polyphenolic compounds were identified, primarily derivatives of kaempferol, quercetin, and hydroxycinnamic acid; 43 of these compounds were first reported in CPAL. CPAL polyphenols possess potent antioxidant activities, with IC₅₀ values of 68.77, 12.76, and 101.24 μg/mL for DPPH, ABTS, and FRAP, respectively. Furthermore, as the drying temperature increased, the polyphenol content and antioxidant activity of CPAL increased significantly. These findings provide a scientific basis for the development of natural antioxidants and functional foods. Full article