Search Results (563)

Within the scope of this article is the presentation of a modelling and measurement approach for the effects of roof greenings and the application of the approach to evaluate the influence of roof greenings upon the thermal conditions inside a typical residential building. It is shown that overheating in summer can be reduced, and thermal comfort for inhabitants can be increased. The cooling is caused by the transpiration of plants and by the evaporation of water from the substrate. Other relevant physical effects are the shading of plants and the increase in the heat capacity of the building. In state-of-the-art buildings, a layer with a high insulating effect is incorporated into the envelope. This leads to the effect that a huge fraction of the cooling power is taken from the outside of the building and only a smaller part is taken from the inside. In order to mitigate this decoupling, a hydraulic connection between the greening and the interior of the building is introduced. To evaluate the effect of the inside cooling, the difference in the number of yearly hours with overheating in residential buildings is estimated. In addition, the reduction in energy demand for the climatisation of a typical residential building is calculated. The used methods are as follows: (1) Performance of laboratory and free field measurements. (2) Simulation of a typical residential building, using a validated approach. In summary, it can be said that green roofs, in particular with hydraulic connections, can significantly increase the interior thermal comfort and potentially reduce the energy required for air conditioning. Full article

The non-stationary heat problem of friction for two homogeneous layers with imperfect thermal contact and convective heat exchange on the free surfaces is considered. Assuming a constant specific power of friction, an exact solution of the formulated problem is obtained using the Laplace integral transform. The solution is verified by checking the fulfillment of the boundary and initial conditions both in the transform space as well as in the space of the original. Particular solutions are also derived for some specific cases, namely, the perfect thermal contact of friction at large values of the contact heat transfer coefficient and the asymptotic solution at the initial time moments of the heating process. On the basis of developed solutions, numerical analysis was performed in dimensionless form. The influence of the thermal contact conductance, the convective cooling intensity, and the relative layer thickness on the temperature field is investigated. It was established that for Biot number $Bi\ge 50$ yields nearly equal surface temperatures. Full article

This study evaluates indoor thermal comfort and the energy performance of HVAC control strategies in the Congo Zone of a zoological facility located in Poland. The main objective in this zone is to maintain adequate relative humidity, which is more critical for plants and animals than the indoor air temperature range. Long-term measurements were carried out to determine the variation of air system heat transfer as a function of outdoor air temperature. To determine the energy demand for heating, cooling, and air transport, eight control algorithms were analysed, each differing in a single detail but potentially affecting overall energy use and thermal comfort. The algorithms combined the following features: maintaining a constant supply or indoor air temperature; operating with a constant or modulated recirculation damper position; maintaining a constant or variable airflow (CAV or VAV); operating within the normal setpoint range or with an extended range of 1 °C; controlling temperature only or both temperature and humidity; and utilising or not utilising free cooling. The control algorithm operating in the facility maintained indoor humidity within acceptable limits for 98% of the year but failed to meet temperature requirements for 28% of the time. Refined strategies achieved energy savings of up to 74% in fan power and 80% in cooling demand, though often at the cost of reduced humidity control. Full article

Gravitational waves (GW) play an important role in the understanding of several astrophysical objects, like neutron stars and black holes. One technology used to detect them involves massive objects that vibrate as GW cross it, and the detectors built are, accordingly, of the resonant-mass type. SCHENBERG is a resonant-mass GW detector, built in Brazil, whose antenna is a spherical, 65 cm in diameter mass made of a CuAl alloy, and its quadrupole vibrational modes would be excited by GW, as predicted by general relativity. The chosen alloy can be cooled down to mK temperatures with a good mechanical quality factor. The quadrupole mode frequencies were measured at 4K, and a frequency band of about 67.5 Hz was found, but when the antenna was simulated in SolidWorks FEM software version 2010–2011 (as well as in Ansys SpaceClaim^TM), the band obtained for a free sphere was different—around 30 Hz. When the holes for the suspension were included in the simulation, the same discrepancy persisted. In this work, gravity was included in the FEM simulation, and we show that the bandwidth results are even smaller. We were then able to obtain a bandwidth close to the measured one by including a small deviation from the vertical axle, as well as variations on the sphere microstructure, which are assumptions that break the symmetry of a perfect, homogeneous free sphere. We believe that the microstructure variations are due to differences in the cooling time during the sphere casting. As for a good mechanical quality factor, the sphere was not submitted to homogenization. With these additions to the FEM simulation, a reasonable frequency distribution was found, consistent with the one measured for SCHENBERG’s antenna. Full article

This study presents a comprehensive overview of recent advancements in fire protection technologies for reinforced concrete (RC) structures, with a focus on sustainable and high-performance solutions. As climate change and urban densification continue to shape modern construction, the need for fire-resilient and environmentally responsible building systems has never been more urgent. This study examines traditional fire protection practices and contrasts them with emerging innovations. Emphasis is placed on their thermal performance, structural integrity post-exposure, and long-term durability. Case studies and laboratory findings highlight the effectiveness of these systems under standard and severe fire scenarios. This paper will present the results of a research study on the assessment of different fire protection systems for RC columns retrofitted with fiber-reinforced polymer (FRP) jacketing. To quantify how insulation can preserve confinement, three commercial fire protection schemes were tested on small-scale CFRP- and GFRP-confined concrete cylinders: (i) a thin high-temperature cloth + blanket (DYMAT™-RS/Dymatherm), (ii) an intumescent epoxy-based coating (DCF-D + FireFree 88), and (iii) cementitious mortar (Sikacrete™ 213F, 15 mm and 30 mm). Specimens were exposed to either 60 min of soaking at 200 °C and 400 °C or to a 30 min and 240 min ASTM E119 standard fire; thermocouples recorded interface temperatures and post-cooling uniaxial compression quantified residual capacity. All systems reduced FRP–interface temperatures by up to 150 °C and preserved 65–90% of the original confinement capacity under moderate fire conditions ($\le$400 °C and $\le$30 min ASTM E119) compared to 40–55% for unprotected controls under the same conditions. The results provide practical guidance on selecting insulation types and thicknesses for fire-resilient FRP retrofits. Full article

We present two case studies of tropospheric aerosol transport observed over the high-altitude Helmos observatory (1800–2300 m a.s.l.) in Greece during September 2021. Two cases were linked to Saharan dust intrusions, of which one was additionally linked to a mixture of biomass-burning and continental aerosols. Aerosol vertical profiles from the AIAS mobile backscatter/depolarization lidar (532 nm, NTUA) revealed distinct aerosol layers between 2 and 6 km a.s.l., with particle linear depolarization ratio values of up to 0.30–0.40, indicative of mineral dust. The elevated location of Helmos allows lidar measurements in the free troposphere, minimizing planetary boundary layer influence and improving the attribution of long-range transported aerosols. Radiative impacts were quantified using the LibRadtran model. For the 27 September dust outbreak, simulations showed strong shortwave absorption within 3–7 km, peaking at 5–6 km, with surface forcing reaching −25 W m⁻² and TOA forcing around −12 W m⁻², thus, implying a net cooling by 13 W m⁻² on the Earth’s atmosphere system. In contrast, the 30 September mixed aerosol case produced substantial solar attenuation, a surface heating rate of 2.57 K day⁻¹, and a small positive forcing aloft (~0.05 K day⁻¹). These results emphasize the contrasting radiative roles of dust and smoke over the Mediterranean and the importance of high-altitude observatories for constraining aerosol–radiation interactions. Full article

Increasingly stringent energy directives of the European Union, combined with rising cooling demands due to climate change, urge the investigation of energy-efficient cooling solutions. Free cooling offers a viable approach to reducing energy consumption. However, its effectiveness and applicability across different building types remain insufficiently established. This study aims to minimise mechanical cooling energy demand through the implementation of enhanced free cooling (EFC) as an operational control strategy in office, residential, and small commercial buildings. The introduction of the efficiency of EFC (η_fc) supports this analysis by quantifying how effectively EFC exploits free cooling potential in defined thermal and mechanical conditions based on an analytical approach supported by simplified simulations (in Microsoft Excel). The case study indicates that the east-oriented office building with a 40% glazing ratio achieves the highest cooling energy savings (49.63%) on the target summer day. For the residential building, savings are lower (37.78%) but more stable across the hot and the extremely hot days. The results further show that the influence of building orientation diminishes as external temperature increases, while higher glazing ratios stabilise η_fc across the examined thermal conditions. Analysis of the connection between air exchange rate and mechanical cooling energy savings identifies a critical resistance point (n_opt), defined as the ventilation rate beyond which no further cooling energy savings occur. The results enable practical applications in building operation and support both improved energy efficiency and the advancement of sustainable HVAC design. Full article

The fabrication of support-free structures in pellet additive manufacturing (PAM) is severely limited by gravity-induced sagging, a phenomenon lacking predictive, physics-based models. This study introduces and validates a numerical model for the thermofluid dynamics of sagging, aiming to correlate process parameters with filament deflection. A predictive finite element (FE) model incorporating temperature-dependent non-Newtonian material properties and heat transfer dynamics has been developed. This was validated via a systematic experimental study on a desktop-scale PAM 3D printer investigating nozzle temperature, printhead speed, screw speed and fan cooling, using polylactic acid (PLA) as a printing material. Findings show that process parameter optimization can reduce bridge deflection by 64.91%, with active fan cooling being the most dominant factor due to accelerated solidification. Increased printhead speed reduced sagging, whereas higher screw speeds and extrusion temperature showed the opposite effect. The FE model accurately replicated these results and further revealed that sagging ceases once the filament cools below its minimum flow temperature (approximately 150–160 °C for PLA). This validated model provides a robust foundation for tuning process parameters, unlocking effective support-free 3D printing in PAM. Full article

This study investigated the relationships between emulsion droplet triacylglycerol (TAG) crystallinity and colloidal acid stability on in vitro digestion microstructure, lipolysis, and docosahexaenoic acid (DHA) bioaccessibility. Oil-in-water (o/w) nanoemulsions (20 wt%) composed of 50/50 DHA-rich algal oil with either palm stearin (PS) or olein (PO), and either acid-stable Tween 80 (2.0 wt%; AS) or acid-unstable soy lecithin (2.2 wt%; AU) were fast or slow cooled to 37 °C after microfluidization. Similar particle size distributions and D_3,2 (~131–142 nm) and D_4,3 (~208–239 nm) values were achieved. All emulsions were highly electronegative (~−45–70 mV) and differences (p < 0.05) were due to emulsifier type, as expected, and cooling rate. Next, emulsions were subjected to INFOGEST in vitro digestion for analysis of intestinal lipolysis by free fatty acid titration and DHA bioaccessibility. As expected, AU emulsions flocculated, forming larger aggregates during the gastric phase. Slower lipolysis was observed for the AU emulsions (p < 0.05), attributed to gastric phase aggregation, and lower 2 h lipolysis was observed for the PS emulsions (~74–77%) based on the presence of crystallinity. DHA bioaccessibility was high (~57–88%), especially for the AS emulsions (p < 0.05). Therefore, emulsion colloidal acid stability and TAG physical state significantly impacted emulsion gastric microstructure, digestion, and bioaccessibility. Full article

Effective thermal management of molds is a governing factor of the quality and stability of the injection molding process. This study introduces and validates an integrated cooling layer within a thin-walled insert mold designed to enhance thermal control and cavity filling performance. A coupled heat transfer simulation model was developed and subsequently calibrated against experimental temperature measurements. To isolate the mold’s intrinsic thermal response, temperatures were measured during distinct heating and cooling cycles, free from the perturbations of polymer melt flow. The validated mold was then installed on a Haitian MA1200 III injection molding machine to conduct molding trials under various injection pressures. A strong correlation was found between the simulation and experimental results, particularly as pressure increased, which significantly improved cavity filling and reduced the deviation between the two methods. The integrated cooling layer was shown to enhance heat dissipation, minimize thermal gradients, and promote a more uniform thermal field. This, in turn, improved filling stability, especially at moderate injection pressures. These findings provide robust quantitative data for simulation model calibration and mold design optimization, highlighting the potential of advanced cooling strategies to significantly enhance injection molding performance. Full article

This study addresses the operational challenges of conventional packed cooling towers in seawater applications, where salt deposition and blockage significantly impair performance. A packing-free shower cooling tower (SCT) utilizing droplet-based heat and mass transfer is proposed as a robust alternative for high-salinity applications where conventional packed towers are prone to fouling and blockage. A comprehensive numerical model was developed and validated experimentally, showing a maximum error of less than 6% in predicting outlet water temperature. The analysis demonstrates that increasing salinity markedly reduces cooling efficiency—for instance, at threefold concentration (S ≈ 57.96 g/kg), efficiency decreased by 5.59% in summer and 4.91% in winter compared to freshwater, due to reduced vapor pressure and inhibited evaporation. However, elevating the inlet water temperature and air-to-water ratio partially counteracted these effects by enhancing evaporative and convective transfer. Larger droplet diameters also adversely affected performance, with cooling efficiency dropping from 75.87% (1 mm droplets) to 28.92% (3.5 mm droplets) in freshwater summer conditions. Notably, seasonal variations influenced the magnitude of salinity-related performance loss, with winter operations exhibiting less degradation. These findings provide critical insights and a reliable predictive tool for the design and optimization of high-salinity cooling systems. Full article

Carbide-free bainite microstructures were developed in 0.6 wt.%–2 wt.% Si spring steel via austempering at 250 °C. Heat treatment included austenization with subsequent isothermal holding at 250 °C, varying the holding duration to 1.0, 1.5, or 2.0 h with final cooling in water. X-ray diffraction, SEM investigation, tensile test, and hardness measurement were employed to study the microstructure and phase compositions of the samples. It was found that nanostructured bainite developed in the experimental steel. The distribution of distances between phase borders was determined via digital processing of SEM micrographs, and the mode distance was found to be 30 nm. The analytical estimation of possible strengthening showed that the yield strength of the nanobainite obtained should be in the gigapascal range, and the tensile testing results demonstrated that a 2 GPa yield strength was developed in the sample after isothermal treatment at 250 °C for 1 h. Investigations of the fracture surface and microstructure of the cross-section near the fracture zone confirmed the ductile mode of failure. Full article

Heat stress (HS), a pervasive environmental stressor, significantly disrupts systemic physiological homeostasis, posing substantial threats to human and animal health. Sheng Mai San (SMS), a classic Traditional Chinese Medicine (TCM) formula, exerts its therapeutic effects by replenishing qi (the vital energy governing physiological functions) and nourishing yin (the material basis responsible for moistening and cooling actions). This formula demonstrates significant efficacy in astringing sweating and preventing collapse. However, its precise molecular mechanisms against HS-induced myocardial injury remain incompletely elucidated. This study initially employed physicochemical analytical methods to determine the contents of total polysaccharides, saponins, and flavonoids in SMS and evaluated its antioxidant activity. Subsequently, both in vitro and in vivo rat models of HS were established to systematically assess the alterations in reactive oxygen species (ROS), antioxidant enzymes (GSH, SOD, CAT), and heat shock proteins (HSP70, HSP90) following SMS intervention, thereby investigating HS-induced myocardial injury and the protective effects of SMS. Furthermore, Western blot, immunofluorescence, and qRT-PCR techniques were utilized to quantitatively analyze key molecules in the Keap1-Nrf2-HO-1 and Stub1-HSF1 signaling pathways. The results demonstrated that total polysaccharides were the most concentrated in SMS, followed by total saponins. This formula exhibited potent free radical scavenging capacity against DPPH, ABTS, and OH⁻, along with significant reducing activity. HS-induced myocardial injury reached its peak severity at 6-12 h post-stress exposure. SMS intervention effectively suppressed excessive ROS generation, enhanced the activities of antioxidant enzymes (GSH, SOD, and CAT), and downregulated HSP70 and HSP90 mRNA expression levels, thereby significantly mitigating cardiomyocyte damage. Mechanistic investigations revealed that SMS conferred cardioprotection through dual modulation of the Keap1-Nrf2-HO-1 and Stub1-HSF1 signaling pathways. This study not only provides a novel TCM-based therapeutic strategy for preventing and treating HS-related cardiovascular disorders but also establishes a crucial theoretical foundation for further exploration of SMS’s pharmacological mechanisms and clinical applications. Full article

Laboratory buildings represent some of the highest energy-consuming infrastructure due to stringent environmental requirements and the continuous operation of specialized equipment. Ensuring both energy efficiency and indoor air quality (IAQ) in such spaces remains a central challenge for sustainable building design and operation. Recent advances in Internet of Things (IoT) systems allow for real-time monitoring of multivariate environmental parameters, including CO₂, total volatile organic compounds (TVOC), PM_2.5, temperature, humidity, and noise. However, these datasets are often noisy or incomplete, complicating conventional monitoring approaches. Supervised anomaly detection methods are ill-suited to such contexts due to the lack of labeled data. In contrast, unsupervised machine learning (ML) techniques can autonomously detect patterns and deviations without annotations, offering a scalable alternative. The challenge of identifying anomalous environmental conditions and latent operational states in laboratory environments is addressed through the application of unsupervised models to 1808 hourly observations collected over four months. Anomaly detection was conducted using Isolation Forest (300 trees, contamination = 0.05) and One-Class Support Vector Machine (One-Class SVM) (RBF kernel, ν = 0.05, γ auto-scaled). Standardized six-dimensional feature vectors captured key environmental and energy-related variables. K-means clustering (k = 3) revealed three persistent operational states: Empty/Cool (42.6%), Experiment (37.6%), and Crowded (19.8%). Detected anomalies included CO₂ surges above 1800 ppm, TVOC concentrations exceeding 4000 ppb, and compound deviations in noise and temperature. The models demonstrated sensitivity to both abrupt and structural anomalies. Latent states were shown to correspond with occupancy patterns, experimental activities, and inactive system operation, offering interpretable environmental profiles. The methodology supports integration into adaptive heating, ventilation, and air conditioning (HVAC) frameworks, enabling real-time, label-free environmental management. Findings contribute to intelligent infrastructure development, particularly in resource-constrained laboratories, and advance progress toward sustainability targets in energy, health, and automation. Full article

During machining, most of the mechanical energy is converted into heat. A substantial part of this heat is transferred to the cutting tool, causing a rapid rise in tool temperature. Excessive thermal loads accelerate tool wear and lead to displacement of the tool center point, reducing machining accuracy and workpiece quality. This challenge is particularly pronounced when machining titanium alloys. Due to their low thermal conductivity, titanium alloys impose significantly higher thermal loads on the cutting tool compared to conventional carbon steels, making the process more difficult. To reduce temperatures in the cutting zone, cutting fluids are widely employed in titanium machining. They have been shown to significantly extend tool life. Cutting fluids are broadly categorized into cutting oils and water-based cutting fluids. Owing to their distinct thermophysical properties, these fluids exhibit notably different cooling and lubrication performance. However, current research lacks comprehensive cross-comparative studies of different cutting fluid types, which hinders the selection of optimal cutting fluids for process optimization. This study examines the influence of three cutting fluids—emulsion, cutting oil, and synthetic oil-free fluid—on tool wear, temperature, surface quality, and energy consumption during flood-cooled end milling of Ti-6Al-4V. A novel experimental setup incorporating embedded thermocouples enabled real-time temperature measurement near the cutting edge. Tool wear, torque, and surface roughness were recorded over defined feed lengths. Among the tested fluids, emulsion achieved the best balance of cooling and lubrication, resulting in the longest tool life with a feed travel path of 12.21 m. This corresponds to an increase of approximately 200% compared to cutting oil and oil-free fluid. Cutting oil offered superior lubrication but limited cooling capacity, resulting in localized thermal damage and edge chipping. Water-based cutting fluids reduced tool temperatures by over 300 °C compared to dry cutting but, in some cases, increased notch wear due to higher mechanical stress at the entry point. Power consumption analysis revealed that the cutting fluid supply system accounted for 60–70% of total energy use, particularly with high-viscosity fluids like cutting oil. Complementary thermal and CFD simulations were used to quantify heat partitioning and convective cooling efficiency. The results showed that water-based fluids achieved heat transfer coefficients up to 175 kW/m²·K, more than ten times higher than those of cutting oil. These findings emphasize the importance of selecting suitable cutting fluids and optimizing their supply to enhance tool performance and energy efficiency in Ti-6Al-4V machining. Full article