Search Results (1,266)

Radiant tube burners (RTBs) are widely used in industrial heat-treatment furnaces, yet the coupled effects of hydrogen co-firing and exhaust gas recirculation (EGR) on their thermal fields remain insufficiently understood. This study presents a three-dimensional CFD analysis of 28 operating conditions, spanning hydrogen fractions from 0 to 100% and EGR rates from 0 to 20% at a fixed excess air ratio of 10%. The model employs the eddy dissipation concept with a reduced two-step methane mechanism, detailed hydrogen kinetics, and a Discrete Ordinates radiation model with a weighted-sum-of-gray-gases approach. All cases exhibit splitting flames: hydrogen enrichment intrinsically raises the laminar flame speed above the flame morphological transition threshold, while in pure methane, radiative preheating increases the flame speed by 29%, eliminating the triangular flame mode. The volumetric temperature uniformity index peaks near 30% H₂, whereas EGR improves uniformity in hydrogen-rich cases but slightly degrades it in methane-rich conditions. Surface temperature uniformity is maximized at 20% EGR due to near-wall thermal blanketing. Thermal efficiency increases with hydrogen fraction, from 59.1% at 0% H₂ without EGR to 68.6% at 100% H₂ with 10% EGR, while higher EGR suppresses peak temperatures. These findings provide guidance for balancing energy efficiency and temperature uniformity in hydrogen-ready RTBs. Full article

Earth-based materials are promising candidates for balancing thermal performance, hygrothermal regulation, and environmental sustainability. The objective of this study is to evaluate and compare the hygrothermal behavior of two earthen materials, structural cob and lightweight insulating earth, against conventional reference concrete, taking into account not only their insulating properties but also their ability to regulate coupled heat and moisture transfers. Experimental tests show a significantly higher hygroscopic buffering capacity for earth-based materials, with an MBV of 2.23 g/(m²∙%RH) for the structural material and 1.21 g/(m²∙%RH) for the insulation material, compared to less than 0.5 g/(m²∙%RH) for concrete. The sorption isotherms confirm distinct water storage behaviors, with an average sensitivity to relative humidity of 10.47% for the insulation material, compared to 3.8% for concrete and 2.25% for the structural material, in addition to an average reduction of 26% in the adsorption capacity between 23 °C and 45 °C for both earthen materials. Coupled heat–moisture simulations in COMSOL quantitatively demonstrate the hygrothermal superiority of bio-based materials over conventional concrete, as concrete promotes interstitial moisture accumulation due to its low vapor permeability. The parametric sensitivity analysis highlights the effect of hygrothermal properties, where diffusivity controls transport kinetics and sorption governs water storage, while thermal conductivity modulates the spatial redistribution of thermo-hygric fields. The next and final step made it possible to link the phenomena observed at the material scale to the actual energy performance of the building, confirming the potential of the double-wall cob + lightweight earth system to reduce heating and cooling requirements and maintain stable indoor comfort, where the annual heating demand is reduced by approximately 24% compared to the conventional prototype. Full article

High Velocity Oxy-Fuel (HVOF) thermal spraying enables the deposition of dense coatings with low porosity, high hardness, and good fracture resistance. Tungsten carbide–cobalt (WC-Co) coatings are widely used in industrial and aerospace applications due to their excellent wear resistance; however, improving crack resistance and coating–substrate adhesion remains a key challenge. In this study, WC-Co+Ni composite coatings were deposited on ductile cast iron, with emphasis on the role of Ni addition in controlling microstructure development under HVOF conditions. Microstructural characterization was performed using optical, scanning, and transmission electron microscopy (OM, SEM, TEM), while phase composition and chemical analysis were determined by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The coatings exhibited a dense, low-porosity microstructure composed of fine WC and W₂C carbides embedded in a Co–Ni binder, with locally nanocrystalline regions. XRD analysis confirmed WC and W₂C as the dominant phases, with weak reflections corresponding to the η-phase (Co₆W₆C), indicating local decarburization. The addition of Ni increases the fraction of the transient liquid phase during particle flight, enhancing carbide dissolution and mass transport in the binder, which accelerates decarburization kinetics and promotes η-phase formation. Simultaneously, Ni modifies the binder into a more ductile Co–Ni matrix, reducing the detrimental effect of brittle η-phase on coating integrity. Mechanical and tribological testing (instrumented indentation and scratch testing) demonstrated improved crack resistance, wear resistance, and adhesion. The results show that Ni addition enables process-driven microstructural tailoring of HVOF-sprayed WC-Co coatings, leading to enhanced performance despite the presence of η-phase. Full article

Thermal regulation of electrode materials offers an effective strategy for optimizing electrochemical kinetics in phosphate-based energy-storage systems. In this work, cobalt phosphate (Co₃(PO₄)₂) (CoP) electrodes were directly synthesized on nickel foam through a hydrothermal route and subsequently annealed at different temperatures (300, 400, and 500 °C) to investigate the influence of thermal treatment on structural evolution and supercapacitive behavior. X-ray diffraction confirmed the formation of crystalline CoP, while FESEM analysis revealed a strong dependence of morphology on annealing temperature, with CoP-400 exhibiting a well-developed interconnected plate-like architecture favorable for ion transport. XPS and elemental mapping verified the successful incorporation and uniform distribution of Co, P, and O species. Electrochemical investigations demonstrated that annealing temperature critically governs charge-storage behavior, ion diffusion, and mass transport properties. Among all electrodes, CoP-400 exhibited the best electrochemical performance, delivering a high areal capacitance of 28.62 F/cm² at 20 mA/cm², together with the highest ionic diffusion coefficient, lowest equivalent series resistance (0.39 Ω), and dominant diffusion-controlled charge-storage contribution (89%). Furthermore, CoP-400 retained 84.44% capacitance after 12,000 cycles. An asymmetric supercapacitor assembled using CoP-400//AC achieved an areal capacitance of 302 mF/cm², an energy density (ED) of 0.094 mWh/cm², and excellent cycling stability. These findings highlight annealing-engineered CoP as a promising electrode material for high-performance asymmetric supercapacitors. Full article

This study investigates potassium-L zeolite (K-L) as an adsorbent for the removal of thallium (Tl⁺) from aqueous solutions, focusing on the relationship between cation exchange and framework structural response. X-ray powder diffraction (XRPD), thermal analysis, and Rietveld refinements were employed to monitor structural modifications upon Tl⁺ uptake, combined with batch adsorption experiments to evaluate the removal performance. At low Tl⁺ uptake, only minor structural perturbations occur, mainly involving slight shifts in extra-framework cation positions and limited rearrangement of channel water molecules. At higher Tl⁺ concentrations, a measurable anisotropic expansion of the zeolite framework is observed, consistent with partial substitution of K⁺ by Tl⁺ and progressive modification of the hydration environment within the pores. Moreover, the crystallographic distribution of Tl⁺ differs from that of the original K⁺ cations, suggesting a specific site preference during the uptake process. Batch experiments reveal rapid uptake kinetics, with equilibrium reached within minutes, and high removal efficiency up to 99.5%. The adsorption behaviour is well described by the Langmuir model, with a maximum adsorption capacity of 631 mg g⁻¹. These findings highlight the coupling between ion exchange and structural flexibility in K-L zeolite and support its potential application for efficient thallium removal from contaminated water. Full article

A computational fluid dynamics (CFD) analysis is conducted to systematically investigate heat transfer enhancement in tubes fitted with grooved twisted tapes and to identify the groove geometry that provides the best thermo-hydraulic performance. Three grooved twisted tape configurations—circular-grooved twisted tapes (CGTT), rectangular-grooved twisted tapes (RGTT), and triangular-grooved twisted tapes (TGTT)—are evaluated and compared with a smooth tube and a conventional twisted tape over a Reynolds number range of 5000–20,000 under isothermal wall conditions. The grooved twisted tapes enhance heat transfer through the combined effects of swirl-induced secondary flows and groove-generated flow disturbances, which intensify turbulent mixing and reduce the thickness of the thermal boundary layer. Compared with the plain tube, the grooved configurations increase the Nusselt number by 1.472–1.98 times while increasing the friction factor by 3.21–3.58 times. Relative to the conventional twisted tape, the grooved designs provide an additional 8.0–12.1% enhancement in heat transfer with only a marginal increase of 0.2–1.5% in friction factor. The thermodynamic analysis indicates that the CGTT configuration exhibits the lowest entropy generation rate and exergy loss throughout the investigated Reynolds number range. In particular, the CGTT achieves a Bejan number of 0.999841 at Re = 5000, demonstrating an excellent balance between heat transfer enhancement and frictional losses. Furthermore, the CGTT attains the highest thermal performance factor (TPF) of 1.294 at Re = 5000 and maintains TPF > 1.0 over the entire Reynolds number range. The overall performance ranking is consistently established as CGTT > TGTT > RGTT based on comprehensive analyses of velocity fields, streamline patterns, turbulent kinetic energy distributions, temperature contours, and thermodynamic characteristics. Although the present study identifies the circular-groove configuration as the optimal design for a twist ratio (y/W) of 3.0, further parametric investigations involving variations in twist ratio, groove dimensions, and groove pitch are required to develop generalized design guidelines. Full article

Direct utilization of biomass-derived silica in neutral surfactant-templated mesoporous synthesis remains underexplored with respect to mesostructure control and functional integration. High-purity silica extracted from acid-treated rice husk ash (~98.4 wt% SiO₂) was employed as the sole precursor in a fluoride-assisted sol–gel route to synthesize MSU-X frameworks without chemical modification. Systematic parametric variation—pH, Si/surfactant ratio, hydrothermal temperature, and aging duration—establishes quantitative structure–processing correlations. Under optimized conditions (pH 2, Si/Tergitol = 8, 60 °C, 96 h), the resulting material exhibits a wormhole-like mesoarchitecture with a BET surface area of 816 m² g⁻¹, mean pore diameter of ~3.6 nm, and three-dimensionally interconnected channels, confirmed by SAXS, TEM, and N₂ sorption. EDXRF analysis confirms effective impurity removal and high silica incorporation efficiency (~95–96%); thermal stability persists to 700 °C, with incipient crystallization near 800 °C. As a functional demonstration, MSU-X served as an anti-agglomeration scaffold for ZIF-8 crystallization during DDT adsorption. Despite attenuated kinetics relative to pristine ZIF-8—where severe agglomeration occludes active imidazole nodes—the Z8/MSU-X composite achieved near-quantitative DDT removal (74.10 mg g⁻¹). This performance stems from the mesoporous matrix driving size-confined, highly dispersed ZIF-8 growth, thereby maximizing active-site exposure. Operating within a reagent-limited regime rather than a capacity-saturated boundary, this efficient depletion confirms that the scaffold successfully suppresses site loss. Ultimately, these findings validate biogenic silica as a directly integrable precursor for tailored mesostructure assembly, positioning agricultural waste as a high-performance feedstock for hierarchical adsorption architectures. Full article

This work presents a case study of sensitivity analysis applied to the modeling of ethanol steam reforming (SRE) in a catalytic porous medium, with a focus on hydrogen production. Considering the high variability of parameters reported in the literature, the objective is not to propose a universal model, but rather to assess the impact of uncertainties associated with input parameters on the model outcomes. The model was developed under steady-state conditions, coupling flow in porous media, species transport, and heat transfer, with kinetics described as a function of partial pressures. The sensitivity analysis was conducted through the systematic variation of kinetic and physicochemical parameters within ranges associated with their uncertainties. The results indicate that activation energy is the parameter most sensitive to uncertainty variation, exhibiting the greatest impact on hydrogen production. The thermal properties of the medium, particularly thermal conductivity and solid density, also stand out, highlighting the role of thermo-kinetic coupling. In contrast, parameters such as porosity, water reaction order, and particle diameter exhibited low sensitivity under the analyzed conditions. As a main contribution, this work establishes a sensitivity hierarchy associated with parameter uncertainties and provides guidance for other researchers regarding the prioritization of their determination and calibration in hydrogen production models. Full article

This study reports the plant-mediated synthesis of copper-oxide-decorated magnetic iron oxide composite (CuO@Fe₃O₄) nanoparticles using Dolomiaea costus extract and their application as nanocarriers for β-galactosidase immobilization. The fabricated nanocomposite exhibited favorable physicochemical properties, achieving an immobilization efficiency of 83%, with enhanced thermal and pH tolerance compared to the free enzyme. Kinetic analysis revealed a modest increase in Km and a 31% decrease in Vmax after immobilization, while maintaining 69% of the catalytic activity, confirming the system’s suitability for industrial lactose hydrolysis. Reusability and storage tests showed 79% retained activity after five cycles and 77% after 60 days at 4 °C. In milk hydrolysis, the immobilized enzyme achieved 77% conversion within 3 h, following pseudo-first-order kinetics. Biocompatibility was evaluated using HepG2 cells via the MTT assay. BDH, MDH, and ABC maintained high cell viability across the tested dilution range of 25–100% (v/v), indicating no detectable cytotoxic effect under the experimental conditions, whereas cisplatin showed marked cytotoxicity with an IC₅₀ of 14.98 µg/mL. These findings demonstrate that the green-synthesized CuO@Fe₃O₄ support provides a safe, reusable, and magnetically recoverable platform for β-galactosidase immobilization, offering a promising sustainable strategy for producing lactose-free dairy products. Full article

In this work, the catalytic effect of a mechanochemically synthesized Co–Fe metal–organic framework (Co–Fe-MOF) on the thermal decomposition behavior of composite ammonium perchlorate–aluminum (AP-Al) systems was studied. The structural and morphological properties of the synthesized catalyst were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results confirmed the formation of a highly dispersed Co–Fe-MOF structure with a heterogeneous surface morphology and uniformly distributed active regions, as observed by SEM. The thermal decomposition behavior of the composites based on AP was studied using differential scanning calorimetry (DSC) at different heating rates. The addition of Co–Fe-MOF significantly affected the thermal decomposition process, moving the main exothermic decomposition step towards lower temperatures. At 5 wt.% of catalyst, the decomposition temperature decreased from 438–467 °C to 358–398 °C. The kinetic parameters were evaluated using the Kissinger and Ozawa–Flynn–Wall methods. The activation energy decreased from around 191–200 kJ·mol⁻¹ for pure AP and 184–194 kJ·mol⁻¹ for the AP-Al system to 95–109 kJ·mol⁻¹ after the introduction of 5 wt.% of Co-Fe-MOF. The observed catalytic activity is associated with accelerated electron transfer processes involving the redox couples Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺, which favor the decomposition of AP and the oxidation of aluminum. The results demonstrate that the mechanochemically synthesized Co–Fe-MOF is an effective catalyst to improve the thermokinetic performance of AP-based energetic systems. Full article

This work presents a spatially explicit 19-variable reaction–diffusion model for within-host SARS-CoV-2 dynamics that integrates viral kinetics, innate and adaptive immune responses, cytokine regulation, antibody production, and tissue-level thermoregulatory dynamics. Adaptive immune recruitment is described through smooth sigmoidal activation functions, whereas pro-inflammatory cytokines are controlled by Michaelis–Menten-type saturation with IL-10 feedback. The thermoregulatory component is formulated as a downstream tissue-level inflammatory readout driven by bounded virus-dependent pyrogenic forcing, homeostatic relaxation, and effective thermal diffusion. The system is solved using a meshless multiquadric radial basis function collocation method based on Kansa’s formulation. Numerical simulations reproduce the qualitative progression of acute infection, including early viral expansion, innate immune activation, delayed adaptive recruitment, and immune-mediated clearance. Spatial analysis reveals heterogeneous tissue-level patterns, such as localized viral foci, antibody depletion near the infection center, delayed cytotoxic effector coverage, and transient thermal gradients. The proposed framework provides a biologically interpretable and computationally flexible approach for investigating the spatiotemporal organization of within-host SARS-CoV-2 immune dynamics, while remaining a mechanistic modeling study rather than a patient-specific clinical predictor. Full article

Multi-field coupled numerical analysis and strain monitoring experiments were conducted for the curing process of a ring-shaped CFRP component. The curing kinetics and mechanical properties of LD-2184 epoxy resin were characterized using non-isothermal DSC, tensile testing, and CTE measurements. The curing reaction follows a single-stage autocatalytic mechanism with an activation energy of 54.73 kJ·mol⁻¹. A piecewise curing kinetics equation was established. The elastic modulus of the fully cured resin is 2.810 GPa, and the coefficient of thermal expansion is 6.060 × 10⁻⁵ K⁻¹. Composite ring specimens were fabricated using a wet winding process. FBG sensors were embedded to monitor axial strain during curing. A coupled numerical model was developed that includes heat conduction, curing kinetics, and curing deformation. ABAQUS was used to simulate the curing process of the composite ring. The results show a temperature gradient within the filament-wound layer. Thermo-chemical strain is similar between inner and outer regions. Total strain varies along the thickness due to mold constraint. Residual stress is governed by resin chemical shrinkage and thermal contraction during cooling. The difference between measured and simulated strain is 7.15%, which supports the validity of the multi-field coupled curing model. Full article

The pressing issues of organic pollutants contamination of aquatic ecosystems challenges current research. Herein, we prepared three melamine-based POFs, to remove organic dyes from water. Melamine was polymerized with 1,4-dibromobutane (POF-1,4), terephthalaldehyde (POF-TerA) and trimesic acid (POF-TriA), obtaining POFs of different structural order degree and aromaticity. POFs were characterized using FT-IR spectroscopy, thermal gravimetric analysis, BET, powder X-ray diffraction and scanning electron microscopy. They were employed to remove cationic (Rhodamine B, RhB and Methylene Blue, MB) and anionic dyes (Methyl Orange, MO and Eosin Yellow, EY), using UV-vis investigation. The adsorption process was studied from the kinetic and thermodynamic points of view and reusing the best adsorbent was also considered. Data collected evidence that adsorption capacity depends on the POF structure, with maximum adsorption capacity, according to Langmuir isotherm model, of 329 mg/g for POF-1,4/MO and 472 mg/g for POF-TerA/RhB. Interactions involved in the adsorption were also elucidated. Comparison with reported data demonstrates that our materials show comparable performance to some previously reported systems. Furthermore, POF-TriA, is effective for dye mixtures and reusable three times without performance loss, after washing with methanol, avoiding harsh acidic/basic treatments. Results obtained systematically relate the adsorption efficiency to structural features of melamine-based POFs, representing useful support in designing such materials to remove selected classes of contaminants. Full article

Phase-inversion in situ implants (PIISIs) represent a versatile polymer platform in which the rational choice of matrix former and solvent system directly governs the macroscopic properties of the resulting depot. This study applied a Quality by Design (QbD) approach to rationalize a bleached shellac–based PIISI, with particular focus on the physicochemical interactions between the polymer and the injection vehicle. Bleached shellac—a natural, low-cost, biodegradable oligomeric resin bearing –COOH, –OH, and ester functional groups—was selected as the matrix former and screened in seven neat solvents and five 1:1 binary combinations at 25% (m/m). Twelve formulations were evaluated against a predefined set of critical quality attributes, including injectability, phase-inversion kinetics, solvent diffusion volume, and implant structure (n = 5 per formulation; mean ± standard deviation (SD); one-way analysis of variance (ANOVA) with Tukey’s post hoc test, p < 0.05). Three lead solvent systems—propylene glycol/N-methylpyrrolidone (PG+NMP), PG/dimethyl sulfoxide (PG+DMSO), and DMSO/benzyl alcohol (DMSO+BA)—were identified as those providing an optimal balance between hydrogen-bond donor/acceptor solvation and controlled solvent extraction. In the second stage, shellac concentration (20–35%) was optimized, with 30% shellac in PG+NMP yielding the fastest phase inversion (~50 s), a structurally uniform matrix, and the lowest swelling (22%). A working mechanistic framework consistent with all observed critical quality attribute (CQA) trends in which solvent hydrogen-bond donor/acceptor balance and water miscibility govern implant architecture is proposed, and it is intended as a hypothesis-generating basis for the rational design of PIISI formulations; direct validation by spectroscopic, thermal-analytical, and biological methods is identified as the next step. The developed formulations are presented as a preliminary physicochemical platform; biological validation (in vitro cytocompatibility and inflammatory response assessment) is required before the system can be considered a validated formulation for dental drug delivery. Full article

The drying kinetics and quality attributes of Polygonatum cyrtonema Hua (PCH), including color, rehydration efficiency, microstructure, and oxidation resistance, were systematically evaluated under various drying methods: hot-air drying (H-D), infrared drying (IR-D), microwave drying (M-D), freeze-drying (F-D), and vacuum drying (V-D). The results indicate that the Midilli model provides the best fit for the experimental data. Among the five drying methods, hot air drying (H-D) is extensively utilized due to its well-established technology; however, its drying performance is relatively average. M-D and IR-D exhibit high drying rates attributed to their strong thermal permeability. Notably, M-D achieves the highest drying rate, with a drying time of only 1/83 that of F-D, yet it demonstrates a relatively low retention rate of total polysaccharides. Furthermore, while IR-D offers fast drying rates, low energy consumption, and favorable color preservation, it performs poorly in preserving the microstructure, active component content, and oxidation resistance of PCH. By contrast, F-D and V-D exhibit significant advantages in maintaining antioxidant activity, active ingredients, and flavor. Nevertheless, F-D requires an extended duration (1080 min), leading to high energy consumption, which restricts its large-scale industrial application. This comprehensive analysis revealed that V-D achieves an optimal balance between energy consumption and product quality, demonstrating substantial advantages and providing a critical reference for the industrial drying production of PCH. Full article