Search Results (2,155)

Plant-based materials exhibit different moisture absorption properties than synthetic materials. In the case of synthetic fibrous insulation, the effect of moisture on thermal conductivity can be relatively easily determined based on the mass fraction of moisture in the material’s skeleton. In the case of cellulosic materials with an open capillary structure, determining this effect requires laboratory testing. The authors conducted laboratory tests of the thermal conductivity coefficient of dry and wet plant-based insulation, such as flax and hemp shives. The effect of material densification at various moisture levels was also considered. The article also presents a numerical analysis of the thermal state and moisture content of thermal insulation used in walls operating under moderate climatic conditions. For damp shives, thermal conductivity increases noticeably with increasing densification, while for dry shives, thermal conductivity decreases until a certain level of densification is achieved. The obtained results were compared with values calculated using a linear model of the relationship between thermal conductivity and moisture content in the material. At higher moisture values, around 14–15 wt.%, thermal conductivity results are significantly lower than those obtained from the linear model (12.5–16.3% in the case of flax shives and 8.4–11.3% in the case of hemp shives) This is a favorable characteristic of shives compared to the performance of, for example, mineral wool in elevated humidity conditions. The authors believe that their results will be not only scientific but also practical, facilitating the assessment of heat loss in buildings. Full article

Urban leaf litter represents an underutilized biomass resource with potential applications in sustainable building materials. This study investigates the suitability of dried, comminuted leaves collected from municipal green areas as a loose-fill thermal insulation material. The material was characterized in terms of thermal conductivity, settlement behavior, fire reaction, resistance to mold growth, water vapor diffusion, hygroscopic sorption, and short-term water absorption. Tests were conducted following relevant DIN and ISO standards, with both untreated and flame-retardant-treated samples examined. Results indicate that the thermal conductivity of leaf-based insulation (λ = 0.041–0.046 W/m·K) is comparable to other bio-based loose-fill materials such as cellulose and wood fiber. Optimal performance was achieved for particles sized 2–16 mm, showing settlement below 1%. All variants, including untreated material, fulfilled the fire resistance requirements of class E, while selected treatments further improved fire resistance. The material exhibited moderate vapor permeability (μ ≈ 4–5), low water absorption, and moisture buffering behavior similar to that of other bio-based insulation materials. Resistance to mold growth was satisfactory under standardized conditions. Overall, the results demonstrate that leaf litter can serve as an effective and environmentally favorable loose-fill insulation material, offering an innovative recycling pathway for urban green waste. Full article

This paper investigates the influence of fire protection systems and insulation materials on the thermal performance of steel columns. An unprotected column and several columns insulated with different fire protection materials were analyzed using the SAFIR^® (2022 version) and ABAQUS simulation (2017 Version). Thermal and mechanical properties of steel were defined according to Eurocode (EC3), and fire exposure was simulated following the ISO-834 standard fire. The following two insulation systems were considered: contour encasement and box encasement. Results show that, for identical material properties and thickness, box encasement significantly slows the temperature rise compared to contour encasement. Vegetable-based fire protection materials such as wood fiber, sheep wool, and expanded cork reduced the steel temperature to 400 °C for up to 80 min and extended fire resistance of steel columns 40 to 310 min. These findings demonstrate that such insulation materials can markedly enhance the fire performance and structural integrity of steel columns, offering a sustainable and effective solution to fire protection. Full article

Mechanical coffee drying is an energy-intensive stage of postharvest processing that directly affects product quality and production costs. This study evaluated the technical and economic feasibility of using expanded polystyrene (EPS) as a thermal insulation material to improve the performance of a mechanical coffee dryer and to demonstrate its potential for sustainable reuse. Experiments were conducted using a total of 210 kg of wet parchment coffee (Coffea arabica L. var. Cenicafé 1) per treatment, corresponding to three experimental replicates of 70 kg each, dried at 50 ± 2 °C, comparing an EPS-insulated dryer (0.02 m thickness) with a non-insulated control. A theoretical model based on steady-state heat transfer through series resistances estimated energy losses and system efficiency for different insulating materials. Theoretical results indicated that EPS, polyethylene foam, and cork reduced heat losses by 58.1%, 54.3%, and 50.9%, respectively. Experimentally, EPS reduced drying time by 7.82%, fuel consumption by 13.9%, and energy demand by 9.5%, while increasing overall efficiency by 6.7% and reducing wall heat losses by 37.7%. Improved temperature stability enhanced heat retention and moisture migration behavior. Economically, EPS reduced operating costs, yielding annual savings of USD 81.5, a 0.45-year payback period, and an annual return on investment (ROI) of 10.86, confirming its viability as a cost-effective and sustainable solution for improving energy efficiency in mechanical coffee drying. Full article

Mosque buildings have symbolic significance, which makes them ideal candidates for implementing energy-efficient building design strategies. Mosques located in hot climates face several challenges in achieving thermal comfort while meeting energy efficiency requirements due to their distinct architectural features and intermittent occupancy patterns. Addressing these challenges requires integrating innovative energy-efficient retrofit strategies that cater to the characteristics of existing contemporary mosque buildings. Thus, this study provides a review of these approaches, considering both passive and active strategies. Passive strategies include thermal insulation, glazing upgrades, and shading improvements, while active ones include Heating, Ventilation, and Air Conditioning (HVAC) zoning and smart control, lighting upgrades, and the integration of photovoltaic panels. The findings highlight the potential of combining both passive and active retrofitting measures to achieve substantial energy performance improvements while addressing the thermal comfort needs of mosque buildings in hot climates. However, more research is needed on smart control systems and advanced building materials to further enhance energy performance in mosque buildings. By adopting these strategies, mosques can serve as models of energy-efficient design, promoting sustainability and resilience in their communities. Full article

This paper introduces the dynamic hygrothermal performances of existing walls in humid climates using the EN ISO 15026 procedure. Water content, mould formation and freezing risk were investigated considering rock wool (RW) and expanded polystyrene (EPS) allocated at different points of two typologies of existing walls requiring renovation. Results show that RW is recommended for insulation on the external side, whereas EPS is more suitable for the internal side. A freezing risk occurs in massive walls insulated internally with RW in severe winter climates. Mould formation appears in the initial phases on the renovated side, driven by the built-in humidity of the new layers. Wall thermal transmittance shows large fluctuations, especially in lightweight structures renovated with EPS, reaching an increase of over 22% at the beginning of the heating period, driven by EPS water content peaks of 1.9 kg/m² in cold climates when installed on the external side, achieved in a stabilized regime and independently from the wall’s technical solution. Outcomes confirm transient hygrothermal analysis as the recommended approach to evaluate the component behaviour over a long-term projection, facilitating sizing in the design phase and ensuring compliance with regulations for retrofitted elements. Full article

Ventilated façade systems are being increasingly used in energy-efficient building envelopes due to their configurational flexibility and potential to reduce thermal bridging. This study focuses on the experimental evaluation of anchoring components used in such systems, specifically examining the effect of various thermal insulation pads and internal inserts on the system’s mechanical, thermal, and fire performance. A series of laboratory tests was carried out to assess the static behavior of aluminum brackets under both tensile (suction wind load) and compressive (pressure wind load) forces. The results demonstrate that the use of thermal pads and inserts does not lead to any significant degradation of the mechanical capacity of the anchoring brackets, confirming their structural reliability. Additional thermal testing revealed that the use of insulating materials significantly reduces heat transfer through the brackets. Fire resistance tests were conducted to compare the performance of different types of insulation pads under elevated temperatures. The findings indicate that the choice of pad material substantially influences both fire integrity and thermal performance. This study confirms the potential of incorporating optimized insulating pads and inserts into façade brackets to enhance the thermal and fire performance of ventilated façades without compromising their structural behavior. Full article

This study investigates the early-age performance of large-area C30 concrete slabs under different curing regimes using a multi-scale approach combining laboratory experiments, field monitoring, and numerical simulation. The experimental results indicated that standard curing (SC7) maximized the mechanical properties. In contrast, the thermal insulation and moisture retention curing (TC) regime significantly reduced temperature gradients and stress mutation amplitudes by 42% compared to wet curing (WC) by leveraging the synergistic effect of aluminum foil and insulating cotton. This makes TC a preferred solution in situations where engineering constraints apply. Field monitoring demonstrated that WC is suitable for humidity-sensitive scenarios with low-temperature control requirements, while TC is more suitable for large-area concrete or low-temperature environments, balancing early strength development and long-term durability. This multi-field coupled model exhibits significant deviations during the early stage (0–7 days) due to complex boundary interactions, but achieves high quantitative accuracy in the long-term steady state (after 14 days), with a maximum error below 8%. The analysis revealed that the key driving factors for stress evolution are early hydration heat–humidity coupling and mid-term boundary transient switching. The study provides a novel, multi-scale validated curing optimization path for crack control in large-area concrete slabs. Full article

The properties of chemically bonded core sands strongly depend on the reactivity of phenol-formaldehyde resole binders and on the granulometry of the sand matrix. This study presents an evaluation of the mechanical, technological, thermomechanical, and thermophysical properties of core sands prepared using two resole binders with different reactivity levels (Resin 1—lower reactivity; Resin 2—higher reactivity) and two fractions of quartz sand (BK 40 and BK 45). The investigations included the kinetics of strength development (1–48 h), friability, permeability, thermal deformation (DMA), and the determination of thermophysical coefficients (λ₂, a₂, b₂) based on temperature field registration during the solidification of a copper plate. The results indicate that sands containing the higher-reactivity binder exhibit a faster early strength increase (≈0.42–0.45 MPa after 1–3 h), whereas sands bonded with the lower-reactivity resin reach higher tensile strength after 24–48 h (≈0.58–0.62 MPa). Specimens based on BK 45 quartz sand achieved higher tensile strength; however, the finer grain fraction resulted in increased friability (up to ≈3.97%) and a reduction in permeability by 30–40%. DMA analysis confirmed that sands based on BK 40 exhibit delayed and more stable thermal deformation. Thermophysical parameters revealed that BK 45 provides significantly higher thermal insulation, extending the solidification time of the Cu plate from 71–73 s to 89–92 s compared with BK 40. Overall, the results indicate that the combination of BK 40 quartz sand and a lower-reactivity resin offers an optimal balance between thermal conductivity and thermal stability, promoting improved technological performance in casting processes. The determined thermophysical coefficients can be directly applied as input data for foundry process simulations. Full article

This review explores the variety of diamond-based sensing applications, emphasizing their material properties, such as high Young’s modulus, thermal conductivity, wide bandgap, chemical stability, and radiation hardness. These diamond properties give excellent performance in mechanical, pressure, thermal, magnetic, optoelectronic, radiation, biosensing, quantum, and other applications. In vibration sensing, nano/poly/single-crystal diamond resonators operate from MHz to GHz frequencies, with high quality factor via CVD growth, diamond-on-insulator techniques, and ICP etching. Pressure sensing uses boron-doped piezoresistive, as well as capacitive and Fabry–Pérot readouts. Thermal sensing merges NV nanothermometry, single-crystal resonant thermometers, and resistive/diode sensors. Magnetic detection offers FeGa/Ti/diamond heterostructures, complementing NV. Optoelectronic applications utilize DUV photodiodes and color centers. Radiation detectors benefit from diamond’s neutron conversion capability. Biosensing leverages boron-doped diamond and hydrogen-terminated SGFETs, as well as gas targets such as NO₂/NH₃/H₂ via surface transfer doping and Pd Schottky/MIS. Imaging uses AFM/NV probes and boron-doped diamond tips. Persistent challenges, such as grain boundary losses in nanocrystalline diamond, limited diamond-on-insulator bonding yield, high temperature interface degradation, humidity-dependent gas transduction, stabilization of hydrogen termination, near-surface nitrogen-vacancy noise, and the cost of high-quality single-crystal diamond, are being addressed through interface and surface chemistry control, catalytic/dielectric stack engineering, photonic integration, and scalable chemical vapor deposition routes. These advances are enabling integrated, high-reliability diamond sensors for extreme and quantum-enhanced applications. Full article

The construction industry is increasingly oriented toward the development of sustainable materials aimed at reducing environmental impact while ensuring adequate mechanical and hygrothermal performance. This study investigates the effect of two distinct forms of waste tire particles—powder (UTWP) and granulate (UTWG)—separately incorporated into lime-stabilized adobe blocks at respective contents of 5–25% and 10–60%. The physical, thermal, mechanical, and microstructural properties of the blocks were evaluated through density measurements, ultrasonic pulse velocity, water absorption, thermal conductivity, mechanical strength tests, and microstructural characterization using SEM-EDX. The results show that the incorporation of powdered waste tires (UTWP) significantly enhances thermal, hygroscopic, and microstructural performance; thermal conductivity decreases by up to 21.6%, and a 40% reduction in capillary water absorption is achieved with only 5% DPUP, indicating improved insulation and increased resistance to moisture. In contrast, granular waste tires (UTWG) induce a notable increase in ductility and acoustic absorption at the expense of a more pronounced reduction in mechanical strength. The observed improvements in water resistance, microstructural stability, and ductile behavior impart a resilient character to the material, making it particularly suitable for arid environments. Overall, adobe modified with optimized fractions of waste tire particles emerges as a sustainable and multifunctional construction material that promotes waste valorization while enhancing the functional performance of earthen architecture. Full article

This work presents the design, modeling, and experimental validation of an innovative, highly autonomous, and economically viable photovoltaic solar cooker, integrating a robust battery storage system. The system combines 1200 Wp photovoltaic panels, a control block with DC/DC power converters and digital control for intelligent energy management, and a thermally insulated heating plate equipped with two resistors. The objective of the system is to reduce dependence on conventional fuels while overcoming the limitations of existing solar cookers, particularly insufficient cooking temperatures, the need for continuous solar orientation, and significant thermal losses. The optimization of thermal insulation using a ceramic fiber and glass wool configuration significantly reduces heat losses and increases the thermal efficiency to 64%, nearly double that of the non-insulated case (34%). This improvement enables cooking temperatures of 100–122 °C, heating element surface temperatures of 185–464 °C, and fast cooking times ranging from 20 to 58 min, depending on the prepared dish. Thermal modeling takes into account sheet metal, strengths, and food. The experimental results show excellent agreement between simulation and measurements (deviation < 5%), and high converter efficiencies (84–97%). The integration of the batteries guarantees an autonomy of 6 to 12 days and a very low depth of discharge (1–3%), allowing continuous cooking even without direct solar radiation. Crucially, the techno-economic analysis confirmed the system’s strong market competitiveness. Despite an Initial Investment Cost (CAPEX) of USD 1141.2, the high performance and low operational expenditure lead to a highly favorable Return on Investment (ROI) of only 4.31 years. Compared to existing conventional and solar cookers, the developed system offers superior energy efficiency and optimized cooking times, and demonstrates rapid profitability. This makes it a sustainable, reliable, and energy-efficient home solution, representing a major technological leap for domestic cooking in rural areas. Full article

This research paper explores the key role of energy analysis in the initial phases of architectural design. The main research question is as follows: How can energy analysis shape and optimize architectural design variables? To address this question, the research paper identifies key architectural design variables, including structural system, roof, window-to-wall ratio (WWR), and building envelope, all of which are influenced by energy efficiency strategies. Through case studies of residential buildings in Bahrain, the research investigates the optimization of these design variables. Energy models are employed to explore the impact of energy analysis on the design and performance of the selected residential buildings. The findings reveal a significant potential for energy reduction in annual consumption through the collective optimization of passive strategies. Furthermore, specific energy reduction for each sole variable is observed, as follows for structural system material (3.63% to 11.29%), roof thermal insulation (0.75% to 3.37%), WWR optimization (0.61% to 1.27%), and building envelope (7.39% to 13.5%). These findings establish energy analysis as a fundamental design approach for initial design phases or selection between design alternatives, and can be generalized to similar arid, humid climates and residential building designs. Full article

This study investigates the thermal performance and durability of high-emissivity-coated tile-type insulators, a key material for cost-effective and reusable thermal protection systems (TPSs), using a high-velocity oxygen fuel (HVOF) torch. A single specimen was first exposed to a heat flux of 1.25 MW/m² for 100 s. The specimen exhibited excellent thermal performance, reaching surface temperatures exceeding 900 °C while maintaining an internal temperature increase of less than 20 °C at a depth of 40 mm from the top. Subsequently, a tile-type specimen was subjected to repeated heating at a heat flux of 0.65 MW/m² for up to 100 s. Despite peak surface temperatures exceeding 700 °C, the internal temperature remained stable, within 50 °C, demonstrating consistent thermal protection. Furthermore, under the same heat flux conditions, the results of four repeated experiments confirmed that the temperature of the thermal protection material at a depth of 40 mm from the surface was maintained within a range of ±1.23 °C (95% confidence interval). These results demonstrate that the tile-type TPS maintains reliable thermal protection performance under repeated re-entry conditions. Full article

Conventional non-intumescent fire-resistive coatings often require excessive thickness and exhibit poor adhesion. To address these limitations, this study developed a novel geopolymer-based aerogel composite (GBAC) coating. The effects of aerogel content, water-to-binder (W/B) ratio, curing age, latex powder, basalt fibers, and an expansive agent on the physical and mechanical properties of GBAC were systematically investigated. The results have indicated that increasing the aerogel content and W/B ratio reduces the dry density, thermal conductivity, and compressive strength. Both basalt fibers and expansive agent significantly inhibit drying shrinkage while enhancing tensile and tensile bonding strength. Although latex powder shows a negligible effect on shrinkage reduction, it effectively improves tensile and bonding strength. The incorporation of 2.5% of latex powder, 1.0% of basalt fibers, and 4.0% of expansive agent results in a remarkable reduction in shrinkage strain by 85.23%, an increase in tensile strength by 90.93%, and an enhancement in tensile bonding strength by 64.89%. GBAC coatings with thicknesses of 20 and 25 mm can extend thermal insulating efficiency of steel plates by 84 and 108 min and make steel beams satisfy the requirements of Classes II and I fire resistance, respectively. Full article