Search Results (28,991)

This study investigates a Solar Air Heating Façade (SAHF), architecturally enhanced through the integration of granular translucent Silica-Aerogel into multi-wall polycarbonate (PC) panels and the implementation of coated timber lamellas. The novelty of this work lies in the combined evaluation of thermal resistance and solar transmission properties of façade-integrated components, aiming to improve both energy efficiency and architectural integration. Two experimental campaigns were conducted: (i) thermal transmittance tests to determine the U-value of PC panels with and without Silica-Aerogel infill, and (ii) solar transmission measurements under controlled artificial solar radiation to evaluate the optical performance of various lamella configurations and coatings. Results show that the incorporation of Silica-Aerogel reduced the U-value by 41.8%, achieving a minimum of 1.19 W/m² K with the 20 mm thick PC panel, while decreasing the solar transmission of 43–53% depending on the incidence angle. The integration of reflective aluminum-coated timber lamella demonstrated promising results, enabling effective management of solar radiation. These findings highlight the potential of façade systems that combine high-performance insulation with visually integrated shading elements. Full article

This study explores the fabrication and characterization of hybrid aluminum matrix composites reinforced with boron carbide (B₄C) and microsilica, produced via ultrasonically assisted stir casting followed by T6 heat treatment. Pure aluminum was selected as the base matrix to evaluate the combined effects of B₄C and microsilica reinforcements. Microstructural analyses showed that ultrasonic treatment effectively dispersed nanoparticles, reduced agglomeration, and enhanced particle–matrix interfacial bonding. T6 heat treatment further refined the grain structure through Zener pinning and promoted the formation of reaction layers at particle interfaces. Mechanical testing revealed that Al/B₄C composites provided the highest strength and hardness, while Al/microsilica systems retained superior ductility. The hybrid Al/B₄C/microsilica composites demonstrated a balanced combination of yield strength (38.6 MPa), ultimate tensile strength (82.6 MPa), and elongation (35.2%), confirming a synergistic strengthening–toughening effect. These results highlight the potential of Al/B₄C/microsilica hybrid reinforcements to optimize the trade-off between strength and ductility in aluminum-based composites. Full article

The method of effectiveness-number of heat transfer units (ε-NTU) is adopted to establish a design indicator prediction model for plate fin precooler (PFP), and experimental verification is conducted. The average error between the experimental heat transfer capacity and the calculated heat transfer capacity is 4.65%, and the predicted mass matches the mass computed via the commercial software SolidWorks 2020. This outcome confirms the model’s reliability. An investigation is conducted into the influences of parametric factors, including hot stream flow length, cold stream flow length, hot side number of layers, and hot side fin pitch on the heat transfer capacity and mass of the PFP. To realize the maximization of heat transfer capacity and the minimization of mass, optimization is performed on the four sensitive configuration parameters by leveraging the multi-objective grey wolf optimizer (MOGWO). This optimization can significantly reduce the mass while ensuring the stability of the heat transfer capacity. Three classes of optimal configurations were derived from Pareto optimal points. Compared to the original structure, the selected schemes exhibit an average 2.95% rise in heat transfer capacity and a 10.7% reduction in mass. These findings show that the optimization method proposed in this study is effective and provides valuable guidance for precooler design. Full article

High-entropy materials have emerged as promising candidates for high-temperature structural, magnetic, and electrochemical applications due to their unique combination of compositional complexity, thermal stability, and tailored functionality. In this study, self-propagating high-temperature synthesis (SHS) was employed to fabricate high-entropy composite in a Ti–Cr–Mn–Co–Ni–Al–C multicomponent system with a focus on elucidating the effect of titanium content on the combustion parameters, as well as on the phase and structure formation patterns of the resulting materials. In situ profiling enables evaluating the maximum combustion temperature of 1560 °C, combustion wave propagation velocity ranging from 0.22 to 4.3 mm/s depending on titanium content, and heating and cooling rates of 300–2000 °C/s and 3 °C/s during synthesis. The synthesized powders exhibited a bimodal particle size distribution, with ~90% of particles below 25 μm and a D50 of 5.38 μm. Post-synthesis densification via spark plasma sintering (SPS) at 1250 °C under 45 MPa yielded dense bulk samples, which exhibited a high relative density and high Vickers microhardness of 1270 ± 35 HV10 attributed to fine TiC dispersion and secondary carbide formation. Thermogravimetric analysis performed under air flow with a heating rate of 20 °C/min showed enhanced thermal stability for both the powder and the sintered bulk. These findings demonstrate the efficacy of SHS for rapid, energy-efficient fabrication of high-entropy composites and underscore the critical role of composition in tailoring their structural and mechanical properties. Full article

Deep and ultra-deep oil and gas reservoirs are characterized by extreme temperature and pressure conditions. During drilling, bottomhole temperatures often exceed the tolerance of downhole tools, leading to signal loss and damage to key components. Accurate prediction of the wellbore temperature field is therefore critical for ultra-deep drilling operations. Cementing quality significantly affects heat transfer between the wellbore and the formation, yet its influence is often neglected in existing prediction models. This study incorporates cementing quality into wellbore–formation heat transfer analysis, develops a method to calculate the effective thermal conductivity of cement, and establishes a transient heat transfer model based on energy conservation. The model is discretized and solved using the finite difference method. The effectiveness of the proposed model is validated against the Keller models, with a resulting relative error of 2.3%. Field data from three ultra-deep wells are used to evaluate the performance of the wellbore heat transfer model, incorporating cementing quality. The results indicate that the mean relative error of bottomhole temperature prediction is 0.77%, while that of outlet temperature prediction is 3.06%. This work provides an accurate method for predicting wellbore temperature profiles in ultra-deep wells and offers technical support for temperature-controlled drilling. Full article

The use of artificial oxygenation to counteract the effects of hypoxia and improve living standards in high-altitude, low-oxygen settings is widespread. A recognized consequence of this intervention is that it elevates the risk of fire occurrence. In this study, we simulated a real fire environment with low-pressure oxygen enrichment in a plateau area. A new multi-measuring apparatus was constructed by integrating an electronic control cone heater and a low-pressure oxygen enrichment combustion platform to enable the simultaneous measurement of multiple parameters. The combined effects of varying oxygen concentrations and thermal irradiance on the combustion behavior of wood plastic composites (WPCs) under specific low-pressure conditions were investigated, and alterations in crucial combustion parameters were examined and evaluated. Increasing the oxygen concentration and heat flux significantly reduced the ignition and combustion times. For instance, at 50 kW/m², the ignition time decreased from 75 s to 16 s as the oxygen concentration increased from 21% to 35%. This effect was suppressed by higher heat fluxes. Compared with low oxygen concentrations and low thermal radiation environments, the ignition time of the material under high oxygen concentrations and high thermal radiation conditions was shortened by more than 78%, indicating that its flammability is enhanced under extreme conditions. Higher oxygen concentrations enhanced the heat feedback to the fuel surface, which accelerated pyrolysis and yielded a more compact flame with reduced dimensions and a color transition from blue-yellow to bright yellow. This intensified combustion was further manifested by an increased mass loss rate (MLR), elevated flame temperature, and a decline in residual mass percentage. The combustion of WPCs displayed distinct stage characteristics, exhibiting “double peak” features in both the MLR and flame temperature, which were attributed to the staged pyrolysis of its wood fiber and plastic components. Full article

The rapid advancement of technologies such as artificial intelligence, big data, and cloud computing has driven continuous expansion of global data centers, resulting in increasingly severe energy consumption and carbon emission challenges. According to projections by the International Energy Agency (IEA), the global electricity demand of data centers is expected to double by 2030. The construction of green data centers has emerged as a critical pathway for achieving carbon neutrality goals and facilitating energy structure transition. This paper presents a systematic review of the role of waste heat recovery technologies in data centers for achieving low-carbon development. Categorized by aspects of waste heat recovery technologies, power production and district heating, it focuses on assessing the applicability of heat collection technologies, such as heat pumps, thermal energy storage and absorption cooling, in different scenarios. This study examines multiple electricity generation pathways, specifically the Organic Rankine Cycle (ORC), Kalina Cycle (KC), and thermoelectric generators (TEG), with comprehensive analysis of their technical performance and economic viability. The study also assesses the feasibility and environmental advantages of using data center waste heat for district heating. This application, supported by heat pumps and thermal energy storage, could serve both residential and industrial areas. The study shows that waste heat recovery technologies can not only significantly reduce the Power Usage Effectiveness (PUE) of data centers, but also deliver substantial economic returns and emission reduction potential. In the future, the integration of green computing power with renewable energy will emerge as the cornerstone of sustainable data center development. Through intelligent energy management systems, cascaded energy utilization and regional energy synergy, data centers are poised to transition from traditional “energy-intensive facilities” to proactive “clean energy collaborators” within the smart grid ecosystem. Full article

Fecal sludge (FS) requires effective management to mitigate environmental and public health risks and enable resource recovery. This study evaluated the effects of microwave (MW) treatment on FS characteristics and subsequent anaerobic digestion (AD) performance. MW treatment raised FS temperatures to ~96 °C, reducing FS volume by 50% and inducing three thermal phases. Soluble chemical oxygen demand (sCOD) showed a multi-phase pattern, with a maximum solubilization of 29.8% during initial heating due to the solubilization of proteins and carbohydrates. Scanning electron microscopy (SEM) revealed morphological changes, while Fourier transform infrared (FTIR) spectroscopy confirmed that core functional groups remained unchanged. MW-pretreated FS enhanced AD performance, achieving a 17% increase in cumulative methane yield, alongside 18% and 33% improvements in organic loading and methane production rates, respectively. MW treatment influenced the phase distribution of digestate components, showing a shift in nutrient portioning towards the liquid fraction. These results suggest that integrating MW pretreatment into FS management systems can improve energy recovery, reduce treatment costs, and support resource-efficient sanitation solutions. Full article

The aim of this work is to investigate the effect of annealing (at temperatures ranging from 260 °C to 530 °C) of thin-walled Al-Mn-Mg-Ti-Zr samples manufactured by selective laser melting (SLM) on their tensile mechanical properties, hardness, and surface roughness. The results of this study may contribute to the development of post-processing modes for thin-walled products made of corrosion-resistant aluminum alloys with increased strength, manufactured using SLM technology. Hierarchical clustering methods allowed us to identify three groups of thin-walled samples with different strain-hardening mechanisms depending on the annealing temperature. The greatest hardening is achieved in the first group of samples annealed at 530 °C. Metallographic analysis showed that at this heat treatment temperature, there are practically no micropores (macrodefects) and microcracks. X-ray phase analysis showed the precipitation of Ti and Zr, as well as the formation of an intermetallic phase with a composition of Mg8Al16. At lower heat treatment temperatures, from 260 °C to 500 °C, the observed hardening is statistically significantly lower than at 530 °C. This phenomenon, combined with the formation of intermetallic phases and the precipitation of titanium/zirconium, contributes to the hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM. The main results of this study show that the optimal strain hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM is achieved by heat treatment at 530 °C for 1 h. The strengthening mechanism has two characteristics: (1) dispersion strengthening due to the formation of precipitates and (2) reduction in macrodefects at high temperatures. Full article

Eco-friendly silver nanoparticle systems are highly effective due to their large surface area and strong adsorption capacity. In this study, a novel silver (diethyldithiocarbamate)-decorated reduced graphene oxide nanocomposite (Ag(DDTC)@rGO) was synthesized via a simple green method, yielding a stable and monodispersed material. SEM and HRTEM analyses revealed uniform anchoring of the Ag(DDTC) complex on rGO, producing a coherent nanocomposite with strong physicochemical coupling. The Ag(DDTC)@rGO nanocomposite exhibited a high Brunauer–Emmett–Teller (BET) surface area (289 m² g⁻¹) with an average pore diameter of 45 nm, confirming the mesoporous nature of the composite. FTIR spectra showed characteristic bands of rGO and DDTC ligands, with new peaks at 620–640 cm⁻¹ confirming the successful anchoring of silver–diethyldithiocarbamate species onto rGO via Ag–S and Ag–O bond formation. Raman spectroscopy further confirmed the multilayered rGO structure after Ag(DDTC) incorporation. X-ray diffraction (XRD) identified a broad hybrid amorphous–crystalline pattern, favorable for catalytic and sensing functions. The superior malachite green adsorption capacity of Ag(DDTC)@rGO was attributed to synergistic electrostatic, π–π stacking, hydrogen bonding, and silver-mediated interactions. Furthermore, antibacterial assays demonstrated significant inhibition of P. aeruginosa ATCC 9027 and S. enterica ATCC 14028, further enhanced by mild heat activation (40–50 °C) that significantly improved the surface activation of silver nanoparticles. The multifunctional Ag(DDTC)@rGO nanocomposite exhibits strong adsorption and antibacterial properties, highlighting its potential for sustainable wastewater treatment and environmental remediation applications. Full article

This paper aims to investigate the rheological behaviour of industrial lubricants at high shear and high pressure. A twin-disk rheometer based on a standard UMT apparatus is used to measure the rheological features and film thickness of three lubricants, namely, 150N, UB-3, and 15W/40, with the shear rate ranging from 0 s⁻¹ to 10⁷ s⁻¹ and the pressure at GPa. A semiempirical rheological model that considers the influence of heat, shear, and fluidic plasticity was proposed to adequately fit the experimental data of three organic lubricants. The rheology of the lubricants has a linear to nonlinear relationship with increasing shear rate, indicating shear thinning, which is then followed by a sharp decrease at approximately 10⁶ s⁻¹ because of thermal effects. At a higher shear rate, the shear stress saturates to a critical value. Moreover, the critical traction coefficients in the saturation region show similar changes in pressure and temperature for the three lubricants. The coefficients are greater at 1 GPa but decrease and saturate above 1.45 GPa, probably because the molecular-free volume is compressed by the constraint. The coefficients change little with varying inlet temperature at 1.45 GPa. This research sheds light on the complex rheological behaviour of three lubricants at high shear rates and high pressures and attempts to explain them theoretically. Full article

This paper investigates the existence of square-mean S-asymptotically $(\omega ,c)$-periodic solutions for a class of neutral impulsive stochastic differential equations driven by fractional Brownian motion, addressing the challenge of modeling long-range dependencies, delayed feedback, and abrupt changes in systems like biological networks or mechanical oscillators. By employing semigroup theory to derive mild solution representations and the Banach contraction principle, we establish sufficient conditions–such as Lipschitz continuity of nonlinear terms and growth bounds on the resolvent operator—that guarantee the uniqueness and existence of such solutions in the space ${\mathcal{S}AP}_{\omega ,c}([0,\infty ),L^2(\Omega ,\mathbb{H}))$. The important results demonstrate that under these assumptions, the mild solution exhibits square-mean S-asymptotic $(\omega ,c)$-periodicity, enabling robust asymptotic analysis beyond classical periodicity. We illustrate these findings with examples, such as a neutral stochastic heat equation with impulses, revealing stability thresholds and decay rates and highlighting the framework’s utility in predicting long-term dynamics. These outcomes advance stochastic analysis by unifying neutral, impulsive, and fractional noise effects, with potential applications in control theory and engineering. Full article

Zero-heat-flux (ZHF) thermometry is a clinically validated method for non-invasive core body temperature monitoring, yet its broad adoption in wearable applications is constrained by the high power consumption of the heater element. In this study, we numerically investigate the role of microporous insulation in minimizing energy demand while preserving measurement accuracy. A three-dimensional finite element model of a ZHF probe was implemented in COMSOL Multiphysics 5.4, consisting of a resistive heater, a microporous insulation shell, and a skin-equivalent substrate regulated by proportional–integral–derivative (PID) control. A Taguchi L9 orthogonal array was utilized to systematically investigate the effects of porosity (0–90%), insulation thickness (2–4 mm), and the convective heat transfer coefficient (5–15 W/m²·K) on the thermal performance of the ZHF thermometry system. Two performance metrics—heater energy consumption and settling time—were analyzed using analysis of variance (ANOVA). The results indicated that porosity accounted for more than 95% of the variance in heater power and over 80% of the variance in settling time. The configuration with φ = 90% and t = 3 mm demonstrated a balanced trade-off between energy efficiency and transient response for low-power ZHF thermometry. These findings provide design insights for energy-efficient wearable temperature sensors. Full article

Microwave (MW) sintering offers a promising alternative to conventional heating in powder metallurgy, providing faster processing, lower energy consumption, and improved microstructural control. In the diamond tool industry—where cost-efficiency and competitiveness are critical—MW–hybrid sintering shows strong potential for producing segments designed for cutting and polishing natural stone and construction materials. This study investigates the effects of sintering temperature, dwell time, and green density on the densification and mechanical properties of metal matrix composite (MMC) segments containing diamond particles. MW sintering reduced the optimum sintering temperature by 90–170 °C when compared to conventional free sintering. Under optimal conditions (57% green density, 820 °C, 5 min dwell), segments achieved ~95% densification and mechanical properties comparable to hot-pressed (HP) samples. Although MW–hybrid sintered matrices exhibited slightly lower Young’s modulus (~15%) and Vickers hardness (~20%), their flexural strength and fracture toughness remained comparable to HP counterparts. Overall, MW hybrid sintering provides a cost-effective, energy-efficient, and scalable route for fabricating high-performance diamond tool segments, supporting both economic viability and sustainable, competitive manufacturing. Full article

The substantial impact of the heating and cooling of the construction sector on global warming necessitates a focus on effective thermal insulation solutions to mitigate high CO₂ emissions. Thus, the development of efficient low-temperature thermochemical energy storage (TCES) materials offers a promising approach to improve thermal regulation. This study explores the morphological, physicochemical, and thermal properties of a silicon composite (PDMS foam) filled with calcium L-lactate (CaL) (0–70 wt.%) for the core sandwich thermopassive regulation of buildings. Furthermore, CaL was incorporated into a composite form to improve the handling and processability of the final sandwich material, as CaL is available in powder form. The results demonstrated that the filler is entirely confined within the polymer matrix (FTIR and ESEM). Additionally, the CaL-PDMS composites showed fully reversible dehydration/hydration abilities over a water vapor hydration–dehydration cycle within a temperature range suitable for low-temperature TCES, with no performance loss due to salt confinement. Regarding the energy density, the 70 wt.% CaL-PDMS composites achieved a value up to 955 MJ/m³, making it an excellent candidate for low-temperature energy storage in the construction sector as compared to other similar composites. These findings contribute to the development of new thermopassive regulation techniques for building materials. Full article