Search Results (7,120)

This paper focuses on the analysis of long-term land surface temperature (LST) dynamics and land-use changes in the city of Košice, Slovakia, during the period 1985–2025. The analysis is based on multi-temporal Landsat satellite imagery processed within a geographic information system (GIS) environment. Non-parametric statistical methods, including the Mann–Kendall trend test and the Theil–Sen slope estimator, were applied at the pixel level to identify the direction, magnitude, and statistical significance of long-term trends. Land-use changes were evaluated using CORINE Land Cover data together with the NDVI and NDBI spectral indices. The results revealed a statistically significant increase in land surface temperature across almost the entire urban area, with the mean LST increasing by 5.83 °C between 1985 and 2025. The analysis also confirmed a strong positive correlation between built-up areas and LST values, whereas vegetation cover exhibited a significant cooling effect represented by a strong negative correlation with surface temperature. Spatial analysis identified pronounced warming hotspots concentrated mainly in industrial and newly urbanized areas, while vegetation-stabilized zones showed lower warming intensity or localized cooling trends. The findings highlight the dominant influence of urbanization processes on the city’s thermal regime and emphasize the importance of urban vegetation as a key adaptation element for mitigating the surface urban heat island effect. The study also illustrates the added value of integrating remote sensing data, GIS tools, and pixel-based trend analysis in the assessment of long-term changes in the urban thermal environment of medium-sized Central European cities. The results provide a spatial basis for climate adaptation planning and future assessments of urban thermal comfort and environmental quality. Full article

The safe and uninterrupted operation of the ship’s main engine is critical for maritime transportation. The shutdown mechanism, part of the main engine protection systems, prevents serious damage by automatically stopping the engine in critical situations such as low lubrication oil pressure, overspeed, high bearing temperature, and cooling system failures. However, identifying the faults that trigger the shutdown system and evaluating their risk levels is crucial for improving system reliability. In this study, shutdown events that may occur in a two-stroke low-speed marine diesel main engine were investigated using Fuzzy Fault Tree Analysis (FFTA). The shutdown event was defined as the peak event, and a total of 34 baseline events were modelled under five main branches: low lubrication oil pressure, overspeed, high thrust bearing temperature, abnormal jacket coolant inlet condition, and crankcase/cylinder oil mist formation. Fuzzy assessments based on expert opinions were defuzzified and converted into probability values and used in fault tree calculations. The results showed that the shutdown risk is largely affected by failures originating from the jacket coolant system and the lubrication oil system. Specifically, lubrication oil filter clogging and contamination/blockage in the coolant line were identified as the most critical risk factors. The findings significantly contribute to prioritizing maintenance and condition-monitoring activities aimed at improving the ship’s main engine reliability through a risk-based approach. Full article

Buildings in Lagos require mechanical cooling year-round, with air conditioning accounting for up to 80% of residential electricity consumption. Despite this, the Nigerian Building Code (NB 485:2017) still references 1990s thermal design data, creating a growing mismatch between design assumptions and actual thermal conditions. Compounding background warming and an intensifying urban heat island have widened this gap considerably, yet no study has linked long-term cooling demand trends to quantified engineering design shortfalls for any Nigerian city. This study presents a 35-year cooling degree day (CDD) trend analysis for Lagos (1990–2024), derived from 12,784 daily temperature records at four engineering base temperatures (22 °C, 23.3 °C, 26 °C, and 28 °C) respectively. Trends are detected using the Mann–Kendall test with Trend-Free Pre-Whitening and Sen’s slope as the magnitude estimator. Significantly increasing CDD trends are confirmed at three base temperatures, with a Sen’s slope of +4.55 °C·days yr⁻¹ at the primary design reference of 23.3 °C (p < 0.01). Structural break analysis identifies 2015 as the transition into a persistently above-baseline thermal regime, with mean CDD in the most recent sub-period exceeding the 1990–2001 design baseline by up to 50% at higher base temperatures. The detected trends are translated into three engineering gap analyses: required envelope U-value trajectories, an HVAC capacity undersizing index, and annual thermal cycling frequency as a structural fatigue proxy. Results show that the dominant uninsulated sandcrete typology fails ASHRAE 90.1-2019 Zone 1A prescriptive limits throughout the study horizon, installed HVAC systems are already operating in the engineering caution zone, and façade fatigue loading has intensified markedly since 2015. To the author’s knowledge, this study is the first to couple a statistically robust long-period CDD record for Lagos with code-referenced design gap figures, providing a replicable framework for climate-adaptive building code revision across similar hot–humid climates in sub-Saharan Africa. Full article

Energy pile groups present a dual-functional solution for structural support and geothermal energy utilization, yet their thermo-mechanical interactions with conventional piles remain insufficiently understood. This study establishes a 3D transient finite element model incorporating thermo-hydro-mechanical coupling to investigate thermal interference and differential settlement in hybrid pile groups under seasonal thermal loading. Systematic parametric analyses of pile length (10–30 m), diameter (1–2 m), and spacing (2D–3D) reveal two key findings: (1) Thermal perturbations in adjacent conventional piles exhibit distance-dependent attenuation characteristics, with measurable temperature variations (1–4 °C) observed within 4D spacing distances; (2) Differential settlement patterns demonstrate significant dependence on thermal operation modes, where heating cycles induce upward thermal stresses while cooling enhances consolidation settlement. The numerical framework is validated against field monitoring data and benchmarked with COMSOL 5.6/ABAQUS 6.14 simulations. Through optimized pile arrangements and spacing configurations, we demonstrate effective mitigation strategies for thermal interference and structural deformation, providing key guidance for the design of geothermal-energy-integrated foundation systems. Full article

Cross-flow micro heat exchangers enable compact thermal management for high-density electronics, but their design is traditionally constrained by a strict trade-off between heat transfer and hydraulic resistance. To mitigate this limitation, we investigate the influence of mixed-geometry channel designs on the coupled thermal and hydraulic performance using a three-dimensional conjugate heat transfer model of water flowing through a stainless-steel micro-matrix with a 40-micrometer hydraulic diameter. Numerical simulations show that at low Reynolds numbers (100 to 200), corner-induced steady three-dimensional flow redistribution modifies the thermal boundary layer, causing convective and hydraulic performance to deviate from standard macroscale predictions. By expanding the transverse microchannel spacing from 10 to 60 μm, the Nusselt number increases from 1.15 to 2.07 while maintaining a nearly constant pressure gradient. These results provide geometric guidelines for designing high-efficiency microfluidic cooling systems by mitigating the traditional trade-off between heat-transfer enhancement and hydraulic resistance. Among the geometries evaluated, pure square channels maximize heat transfer, hybrid circular-square configurations optimize hydraulic efficiency, and triangular designs perform poorly due to high viscous drag. These results provide geometric guidelines for mitigating the traditional trade-off between heat-transfer enhancement and hydraulic resistance in microfluidic cooling systems. Full article

Decarbonising existing commercial buildings requires replacing combustion-based heating systems with electrically driven alternatives such as air-source heat pumps (ASHPs). Although the energy and emissions benefits of heat pumps are well established, less attention has been given to the plant-level electrical demand uplift and hydronic constraints that can limit retrofit feasibility in existing buildings. This study quantifies the electrical demand uplift and air-handling unit (AHU) coil performance limitations associated with ASHP retrofitting in an existing Australian commercial office building. A peak design-load assessment was undertaken to compare the baseline gas-fired heating system with an electrified ASHP configuration under equivalent thermal load conditions. The principal electrical outcomes are derived from a specified 1900 kW Stage 3 plant-screening heating boundary. This boundary reflects the prevailing installed plant-screening condition, rather than the aggregate of scheduled AHU heating duties. First-principles energy balances and hydronic relationships were used to translate thermal demand into plant electrical demand under winter design conditions, while existing AHU heating coils were re-rated under low-temperature hydronic operation. The results show that baseline winter heating is associated with only a small auxiliary electrical load, whereas the governing baseline plant peak occurs during cooling at 399 kW. When referenced to the adopted 1900 kW Stage 3 installed-capacity screening boundary, the peak winter ASHP plant electrical demand increased to 956.66 kW, corresponding to an upper-bound electrical uplift of 557.7 kW relative to the governing baseline plant electrical demand. In parallel, low-temperature hydronic operation (55/45 °C) reduced AHU heating-coil capacity, requiring increased flow rates and, in many cases, coil modification to maintain scheduled duty. These findings indicate that, in the assessed case-study building, the principal barriers to ASHP retrofitting are not annual energy performance alone, but peak electrical infrastructure implications and hydronic system compatibility. The study therefore provides a transparent, building-scale screening methodology for assessing electrification feasibility in existing commercial buildings, while recognising that the reported numerical results are specific to the case-study building and stated design assumptions. Full article

Non-destructive evaluation of surface cracks in Inconel 718 nickel-based alloys operating at high temperatures is crucial for monitoring aero-engine hot-section components. Conventional eddy current testing is often constrained by thermal core degradation and low signal-to-noise ratios, struggling to meet detection requirements in such extreme environments. To address this, this study proposes an optimized absolute probe integrated with an efficient water-cooling system. A multi-physics finite element model was developed to optimize the probe design, focusing on key parameters such as excitation frequency and the geometric dimensions of the coil and ferrite core. Experimental results demonstrate that the optimized probe significantly enhances detection sensitivity over conventional models. Specifically, the peak amplitude increased by 76.2% and the signal-to-noise improved by nearly 10 dB for a 0.3 mm-deep crack. In practical applications, the probe achieves high-sensitivity detection of a 0.3 mm-deep crack at 500 °C. At 600 °C, it reliably detects a 0.5 mm-deep crack with a coefficient of variation not exceeding 3.5% and it retains detection capabilities even at 650 °C. Therefore, this sensor design strategy proves to be a highly viable method for non-destructive evaluation in extreme industrial thermal environments. Full article

Chemical absorption is currently the most mature technology for carbon capture from flue gas in coal-fired power plants. The selection of the amine solution system and process optimization directly determine the energy consumption of carbon capture and are critical to the large-scale implementation of the amine process. In this study, a composite amine solution of N-methyl-diethanolamine-piperazine-water (MDEA-PZ-H₂O) was selected as the CO₂ absorbent. Aspen HYSYS (14.0) software was used to establish a typical process model for CO₂ capture from flue gas in coal-fired power plants. Using single-factor sensitivity analysis, key process parameters in the typical carbon capture process—including amine solution composition, flue gas inlet temperature, lean liquid temperature, and gas-to-liquid ratio—were optimized. Based on the process optimization, this study conducted integrated energy-saving optimization by optimizing the temperature distribution in the absorption tower (achieved through the integration of inter-stage cooling in the absorption tower) and regeneration energy savings (achieved through the coupling of the Mechanical Vapor Recompression (MVR) process). The results indicate that the carbon capture system integrating the inter-stage cooling process with the MVR energy-saving process reduces the energy consumption per unit of carbon captured by 15.15% compared to a typical process system. This demonstrates that the integration of multiple energy-saving processes with the recovery of flue gas and CO₂ waste heat recovery within the system is an effective approach to reducing the energy consumption per unit of carbon capture. Full article

In wind tunnel testing, an active vibration suppression system based on piezoelectric actuators is an effective means to ensure stable operation. However, in a cryogenic wind tunnel testing environment, the performance of piezoelectric actuators degrades significantly when they are exposed to cold temperatures and subjected to uneven cooling. This is particularly problematic during real-time changes in the attack angle of a test model. To ensure the reliable operation of wind tunnel tests, an active–passive hybrid thermal control method is proposed in this paper. First, the insulation and heating structure was designed based on the thermal analysis results. Then, combining simulation and measured data, the temperature field was reconstructed in real time using a recurrent neural network algorithm. Next, considering the non-uniform heat dissipation of the system, a thermal allocation module was designed based on digital–physical integration to actively control the overall and localized heat. Finally, a heat preservation performance test platform was established to conduct cooling experiments in a small-scale cryogenic wind tunnel. The results indicated that the proposed thermal control method reduced the average cooling rate of the system by 97% and improved the overall temperature uniformity by approximately 94.23%. Full article

In order to investigate the suppression effect of different extinguishing agents on lithium-ion battery fires in real confined spaces, a comparative experiment was conducted using aerosols, heptafluoropropane, and perfluorohexanone. In tests without any fire suppression measures, the peak heat release rate reached up to 69.09 kW, and a total of 8.05 MJ of heat was generated along with multiple deflagration events. Moreover, the heptafluoropropane and perfluorohexanone both effectively extinguished the flames with extinguishing times of 12 and 20 s, respectively. The aerosol agent caused a significant contraction of the flames, but it was unable to achieve complete extinguishment. Regarding cooling performance, the heptafluoropropane decreased the front surface temperature of the battery by 147 °C, while perfluorohexanone achieved a reduction of 230 °C. Additionally, the liquid-phase adhesion characteristics of perfluorohexanone enabled sustained cooling. A comprehensive comparison indicates that the perfluorohexanone agent exhibits outstanding performance in flame extinguishment, cooling efficiency, and the suppression of thermal propagation. Heptafluoropropane demonstrates rapid fire suppression and is suitable as a fast-response agent, whereas the aerosol requires a multi-discharge design to achieve reliable performance. Based on these findings, it is recommended that energy storage systems adopt a composite suppression strategy for fire protection. Full article

Human innovation has continually expanded the boundaries of knowledge, from mastering atomic science to reaching the Moon and now into the era of Industry 4.0, where artificial intelligence, the Internet, and advanced additive manufacturing turn imagination into reality. Among these achievements, hypersonic vehicles represent a pinnacle of technological advancement. Modern vehicles reach speeds exceeding Mach 27 (approximately 9300 m/s), where the air at the leading edges transforms into a chemically reactive, thermally ionized plasma. At such velocities, stagnation temperatures climb to 9000–12,000 K (8726.85–11,726.85 °C), creating one of the most extreme environments encountered by any human-made system—conditions under which conventional materials cannot survive without advanced cooling strategies. To address this challenge, researchers worldwide have developed and experimentally validated a range of thermal protection and leading-edge cooling techniques. This review presents the historical evolution of hypersonic vehicles, highlights recent advancements, examines the key challenges posed by sustained hypersonic flight, and surveys state-of-the-art cooling strategies. The discussion emphasizes methods that combine passive, active, adaptive, and hybrid approaches to protect vehicle integrity under extreme thermal loads, providing insight into the current and future capabilities of hypersonic thermal manageme nt. Full article

This study explores the selection of a heat recovery system for cogeneration units based on gas engines supplying the district heating system in Opole in order to enhance the efficiency and sustainability of the system. The proposed modifications focus on utilizing low-temperature (LT) waste heat from engine cooling circuits and improving exhaust heat recovery. The research examines retrofitting three cogeneration engines (total thermal capacity of 7.6 MW) by integrating water-to-water heat pumps to upgrade low-temperature waste heat (55–45 °C up to 700 kW), enhancing heat supply to the district heating network. Additionally, a second stage of economizers is evaluated to maximize condensation-based exhaust heat recovery from the existing 95–135 °C system. These system modifications increase the overall thermal capacity up to 9–9.1 MW. To maintain heat supply during cogeneration unit shutdowns (due to failures or electricity price fluctuations), an auxiliary air-to-water cascade heat pump provides an additional 0.8–1 MW. With increasing electricity price volatility, these system modifications provide crucial operational flexibility. Computational simulations confirm that the hybrid configuration successfully upgrades waste heat while strictly maintaining the existing engine return water safety limit. The evaluation demonstrates high economic profitability alongside stable emission reductions. This research presents a case study in optimizing heat recovery in cogeneration-based district heating networks, demonstrating practical and scalable applications for sustainable energy systems. Full article

This paper presents a parametric numerical study on the cooling performance of photovoltaic panels using water and an Al₂O₃-based nanofluid. The increase in operating temperature leads to a decrease in electrical efficiency, making thermal management a key factor in optimizing these systems. The analysis was carried out through numerical simulations in ANSYS, aiming to evaluate the influence of volumetric flow rate and inlet temperature of the cooling fluid on the panel cooling time under transient conditions. The results show that the performance of the Al₂O₃ nanofluid depends on the flow rate of the cooling fluid. At a low flow rate of 0.05 m³/h and a concentration of 4%, the cooling time is reduced by approximately 18–22% compared to water, while this advantage diminishes as the flow rate increases. A favorable operating region was also observed within the investigated laminar and near-transitional range, beyond which increasing the flow rate produced only limited additional reductions in cooling time under the assumptions of the numerical model. The findings highlight the importance of correlating the thermophysical properties of the fluid with flow parameters in order to optimize the thermal management of photovoltaic panels. Full article

This study critically addresses the challenge of selecting optimal insulation materials for contemporary, energy-efficient building envelopes, a decision with profound environmental, structural, and occupational health consequences. The paper responds to the growing demand for sustainable, resilient solutions by comparing wool, a bio-based, regenerative material, and expanded polystyrene (EPS), a synthetic polymer widely implemented in the construction industry, and advanced laboratory testing (thermal conductivity, moisture buffering, freeze–thaw resistance) is discussed in a comprehensive synthesis of the recent literature. Also, field evaluations from European retrofits and pilot projects (UK, Denmark, Finland, Iceland, Norway, Sweden, Germany and France) further contextualize performance outcomes, and life cycle impacts are considered. Recent results reveal that wool insulation achieves a moisture buffering value (MBV) between 1.8 and 2.7 (g/m²) % RH, minimal vapor resistance (mvr = 1–2), and preserves functional and structural integrity through more than 100 freeze–thaw cycles, leading to significant stabilization of the interior microclimate and enhanced durability. In contrast, EPS delivers lower thermal conductivity (0.032–0.037 (W/mK), critical for reducing heating/cooling demand, but exhibits limited vapor permeability (lvp = 60–150 MN·s/(g·m)), increased risk of condensation and mold, and reduced compressive strength (<22% after 30 cycles), especially when ventilation details are inadequate. Hybrid envelope systems leveraging both EPS and wool are demonstrated to optimize energy efficiency (up to 23% seasonal savings) and reduce interior humidity fluctuations, while lifecycle and recycling assessments show wool panels to be markedly superior in carbon footprint reduction and circularity. The stratification of insulation layers incorporating wool for vapor and moisture control, and EPS for pure thermal resistance is emerging as best practice in sustainable retrofit and new-build projects. Recommendations highlight the necessity for rigorous laboratory validation, international standards alignment, and integrated material design for robust hygrothermal comfort and environmental performance. The review also covers wool- and EPS-based hybrid composites, showing how natural fibers can improve key mechanical properties without compromising thermal insulation performance or environmental benefits. Full article

Ceramic additive manufacturing offers strong potential for fabricating geometrically complex and application-specific components, yet achieving reliable dimensional fidelity remains challenging because dimensional deviation is governed by highly coupled material, process, thermal, and environmental factors. To address this problem, this study proposes an uncertainty-aware computational framework for dimensional error prediction in ceramic 3D printing under variable material and process conditions. The contribution is positioned as a system-level integration of established learning, uncertainty estimation, calibration, and reliability-interpretation components within a ceramic additive manufacturing dimensional-error prediction workflow, rather than as a fundamental methodological breakthrough. The validation is conducted using the publicly available Ceramic 3D Printing Process Control Dataset, a 1000-sample tabular dataset, and the resulting findings are therefore interpreted as dataset-specific computational evidence rather than direct proof of industrial deployment readiness. The methodology begins with a structured data-driven preprocessing pipeline that transforms the Ceramic 3D Printing Process Control Dataset into a multi-condition feature space through data cleaning, one-hot material encoding, min–max normalization, and engineered descriptors capturing extrusion–speed balance, thermal gradients, cooling intensity, deposition density, and material-conditioned interactions. A multi-branch deep computational architecture is then developed to encode material, process, thermal-environmental, and engineered-feature streams separately, followed by adaptive cross-condition fusion to learn nonlinear dependencies across ceramic printing regimes. To improve reliability beyond deterministic regression, the framework jointly models aleatoric and epistemic uncertainty and incorporates calibration refinement to align predictive confidence with observed error behavior, thereby enabling preliminary reliability-oriented interpretation of stable and high-risk operating conditions. Experimental results demonstrate that the full model achieves the best overall within-dataset performance, with a test MAE of 0.0118, RMSE of 0.0172, $R^2=0.999$, MAPE of 1.74%, calibration error of 0.003, PICP of 0.996, reliability score of 0.992, and a stable prediction rate of 98.7%. Although these values indicate strong predictive behavior under the current structured dataset, the exceptionally high $R^2$ should be interpreted cautiously because external experimental validation, larger measured datasets, and cross-machine ceramic printing trials are still required. These findings show that the proposed framework provides an effective system-level computational strategy for dataset-specific reliability-aware dimensional quality prediction in ceramic additive manufacturing and offers a preliminary data-driven foundation for uncertainty-aware intelligent process optimization. Full article