Search Results (407)

Land use change is closely related to land surface temperature (LST). Based on remote sensing data from 2001 to 2020, this study analyzed the spatiotemporal variations and driving mechanisms of daytime and nighttime LST in the Urumqi Metropolitan Area (UMA) by combining traditional methods with the eXtreme Gradient Boosting (XGBoost)–SHAP coupled model. Although the average LST trend in the region was one of warming, the pixel-level significance analysis indicated that statistically significant warming (p < 0.05) is concentrated mainly in the urban core (2.65% of the area), while the majority of the region (70%) showed a non-significant warming trend. LST displayed significant spatial clustering, with Moran’s I remaining above 0.990, indicating a positive spatial autocorrelation in spatial distribution. With the advancement of urbanization, the proportion of impervious surfaces increased from 0.87% to 1.14%, while wastelands consistently accounted for approximately 50% of the total area. Different land use types showed distinct effects on the urban heat island (UHI) phenomenon: water bodies, grasslands, and forests played cooling roles, whereas barren land and impervious areas were the main heat contributors. The XGBoost-SHAP analysis further revealed that the importance ranking of driving factors has evolved over time. Among these factors, Elevation dominates, while the influence of population-related factors increased significantly in 2020. This study provides a scientific basis for regulating the thermal environment of cities in arid regions from the perspective of land use. This study provides a scientific basis for regulating the thermal environment of arid-region cities from the perspective of land use. 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 article analyses the design aspects of multisensory colour experience in interior architecture. It presents the results of comparative studies on the perception of red and blue spatial environments through various senses (vision, hearing, smell, touch, and thermal sensation). The phenomenon of synaesthesia and its potential application in design are discussed, demonstrating how colors can be encoded and perceived through senses other than sight. Spatial solutions are proposed to enable blind individuals to experience color through touch (e.g., differentiated surface textures), sound (appropriate tones or rhythms), temperature (warm vs. cool lighting), and other environmental properties. The text includes references to the cultural and symbolic meanings of red and blue—covering cross-cultural differences and spatial characteristics attributed to these colors—based on an analysis of Stanisław Lem’s novel Solaris. Furthermore, the article formulates design recommendations from the perspective of sustainable development and inclusivity, taking into account European accessibility guidelines and universal design principles. The aim is to present an integrated approach to interior design, in which color becomes an experience accessible to all users, in line with the concept of “Design for All” and the principles of sustainable design. Full article

In cold regions, performance reduction in a Ground-Coupled Heat Pump (GSHP) system has been frequently reported. Many operational strategies have been adopted to mitigate such an undesirable phenomenon. However, these strategies have limited effects because the specific heat rate of Borehole Heat Exchangers (BHEs) is usually treated as constant. In this study, eight BHEs were installed in typical loess areas in Northwestern China to investigate how borehole depth affects its thermal performance. Thermal response tests (TRTs) showed that deeper boreholes led to a higher fluid outlet temperature. Compared to 150 m and 100 m boreholes, the energy coefficient factor (η) for a 200 m borehole increased by 18.02% and 45.0%, respectively. Numerical simulation also confirmed that deeper BHEs perform better. In addition, the initial ground temperature influences the thermal performance sensitively, but in the opposite way for heating and cooling modes. These findings offer valuable insights for installing GSHP systems to achieve sustainable and high thermal performance in cold regions. Full article

This scientific research examines the intricate dynamics of Maxwell nanofluid flow across a stretching surface with Stefan blowing impacts, with a particular focus on maritime thermal management applications. The analysis integrates multiple physical phenomena including magnetohydrodynamic forces, the energy dissipation phenomenon, and thermal density variations within Darcy porous media. Special attention is given to Stefan blowing’s role in modifying thermal and mass transfer boundary layers. We derive an enhanced mathematical formulation that couples Maxwell fluid properties with nanoparticle transport under combined magnetic and density-gradient conditions. Computational results demonstrate the crucial influence of viscous heating and blowing intensity on thermal performance, with direct implications for naval cooling applications. The reduced governing equations form a nonlinear system that requires robust numerical treatment. We implemented the shooting technique to solve this system, verifying its precision through systematic comparison with established benchmark solutions. The close correspondence between results confirms both the method’s reliability and our implementation’s accuracy. The primary results of this study indicate that raising the Stefan blowing and density parameters causes notable changes in the temperature and concentration fields. The Stefan blowing parameter enhances both temperature and concentration near the wall by affecting thermal diffusion and nanoparticle distribution. In contrast, the density parameter reduces these values because of increased fluid resistance. Full article

Urban microclimates depend on the city’s features, geographical position, climatic conditions, solar irradiance, and building materials. Many urban elements delay heat dissipation, giving rise to the urban heat island (UHI) phenomenon. (1) In Mexico City, UHIs occur mainly during the dry season (April–May) and likely increase in energy consumption in buildings. (2) Computational fluid dynamics models such as Ansys Fluent provide detailed flow field data related to atmospheric parameters and building surface fluctuations. With the data generated, a mitigation technique is proposed that displaces heat away from buildings, using air turbulence to actively cool them by examining the performance of w. (3) An experimental analysis was carried out to simulate thermal and aerodynamic scenarios throughout the day around three modules of different sizes, configurations, and albedo values. All modules showed a decrease in the difference between the building temperature and the air temperature, becoming colder with differences from −0.46 to −0.76 °C, while w presented values from −1.3 to 0.59 m·s⁻¹, indicating some turbulence. (4) Therefore, it is necessary to consider mitigating UHIs in urban planning through efficient use of the properties and construction materials of each building and their arrangement in each block. Full article

There are various mechanisms through which water droplets can be present in compressor flows, e.g., rain ingestion in aeroengines or overspray fogging used in heavy-duty gas turbines to boost power output. For the latter, droplet evaporation within the compressor leads to a cooling of the flow as well as to a shift in the fluid properties, which is beneficial to the overall process. However, due to their inertia, the majority of droplets are deposited in the first stages of a multistage compressor. While this phenomenon is generally considered in CFD computations of droplet-laden flows, the subsequent re-entrainment of collected water, the formation of new droplets, and the impact on the overall evaporation are mostly neglected because of the additional computational effort required, especially with regard to the modeling of films formed by the deposited water. The work presented here shows an approach that allows for the integration of the process of droplet deposition and re-entrainment based on relatively simple correlations and experimental observations from the literature. Thus, the two-phase flow in multistage compressors can be modelled and analyzed very efficiently. In this paper, the models and assumptions used are described first, then the results of a study performed based on a generic multistage compressor are presented, whereby the various models are integrated step by step to allow an assessment of their impact on the droplet evaporation throughout the compressor and overall performance. It can be shown that evaporation becomes largely independent of droplet size when deposition on both rotor and stator and subsequent re-entrainment of collected water is considered. In addition, open issues with regard to the future improvement of models and correlations of two-phase flow phenomena are highlighted based on the results of the current investigation. Full article

In metallurgy, the quenching process often induces changes in certain material properties, such as hardness and ductility, through the rapid cooling of a workpiece in water, gas, oil, polymer, air, or other fluids. Given that lithium-ion batteries operate under relatively benign conditions, conventional rapid cooling does not significantly affect the property variations in their internal electrode materials during normal use. However, thermal runaway presents an exception due to its dramatic temperature fluctuations from room temperature to several hundred degrees Celsius. In this study, we investigated NCM811 cathodes in 18,650 batteries subjected to transient thermal runaway followed by rapid cooling using several advanced analytical techniques. The results reveal a phenomenon characterized by intergranular cracking within NCM811 cathode materials when exposed to rapid cooling during transient thermal runaway. Furthermore, lithium-ion cells utilizing reused NCM-182.4 electrodes in fresh electrolyte demonstrate a reversible capacity of 231.4 mAh/g after 30 cycles at 0.1 C, highlighting the potential for reusing NCM811 cathodes in the lithium-ion battery recycling process. These findings not only illustrate that NCM811 particles may experience intergranular cracking when subjected to rapid cooling during transient thermal runaway, but also the rapidly cooled NCM811 electrodes exhibit potential for reuse. Full article

There is increasing interest in the role of parks as potential cool refuges in the age of climate change. Such potential refuges result from the Park Cool Island (PCI) effect, reflecting the temperature differential between the park and surrounding urban areas. However, this study of different park typologies in Perth, Australia, illustrates that while surface temperatures are 10–15 °C lower in parks during summer afternoons (much less than at other times), air temperatures are generally no different from the adjacent streetscape for the smaller parks. Only the largest park in the study had 1–2 °C lower morning and mid-afternoon air temperature differentials. The study illustrates that while the PCI is a real phenomenon, the magnitude in terms of air temperature is small, and it is of less relevance to the conditions felt by humans in average summer daytime conditions than the direct effects of solar radiation. Many studies have assessed the PCI effect, an indicator that has shown a wide range across different studies and measurement techniques. However, this novel paper utilises satellite remote-sensed land surface temperatures, on-ground measurements of surface temperatures, air temperatures, and humidity, as well as modelling using the microclimatic simulation software ENVI-met version 5.0. A reliance on land surface temperature, which in isolation has a marginal correlation with human experience of thermal comfort, has led some researchers to overstate the PCI effect and its influence on adjoining urban areas. The research reported in this paper illustrates that it is the shade provided by the canopy in parks, rather than parks themselves, that provides meaningful thermal comfort benefits. Accordingly, adaptation to increasing temperatures requires the creation of a continuous canopy, ideally over parks, streetscapes, and private lots in an interconnected network. Full article

A novel behavior of fluid inclusions (FIs) in crystals is reported in this study. Typically, at “high” temperature, FIs in molecular crystals become faceted, adopting the morphology of a single crystal. Usually, upon cooling, these faceted FIs develop into rounded cavities containing the mother solution with a retreat gas bubble. After annealing at low temperature, the FIs reshape back into a negative-crystal morphology, but the gas bubble remains. This latter process can take from minutes to very long times depending on the storage temperature and solubility. Investigations into the behavior of FIs of dicumyl peroxide (DCP) under fast cooling rates have revealed a morphological transition from negative crystals to FIs with a holly-leaf shape. The spikes of the holly-leaf-shaped FIs point toward the corners of the former negative crystal, and the sizes of the gas bubbles exceed those of conventional retreat bubbles. Therefore, it is likely that this phenomenon is linked to rapid cooling and an excess of CO₂ dissolved in the mother solution from which the DCP single crystals were grown. The concentration of the solution inside the FIs rapidly increases after the nucleation of this large gas bubble. This is consistent with a sharp acceleration of inward crystal growth immediately after its appearance. Interestingly, FIs in pyroclastic olivine crystals grown from CO₂-rich lava can also present a holly-leaf shape. Thus, this non-equilibrium morphological transition may be relatively common. Full article

As global climate change accelerates, the urban heat island (UHI) phenomenon has become increasingly pronounced, posing significant challenges to urban energy balance, atmospheric processes, and public health. This study used the Weather Research and Forecasting (WRF) model to dynamically downscale two CMIP6 scenarios—moderate forcing (SSP245) and high forcing (SSP585)—focusing on Zhengzhou, a rapidly urbanizing city in central China. High-resolution simulations captured fine-scale intra-urban temperature patterns and analyze the spatial and seasonal variations in UHI intensity in 2030 and 2060. The results demonstrated significant seasonal variations in UHI effects in Zhengzhou for both 2030 and 2060 under SSP245 and SSP585 scenarios, with the most pronounced warming in summer. Notably, under the SSP245 scenario, elevated autumn temperatures in suburban areas reduced the urban–rural temperature gradient, while intensified rural cooling during winter enhanced the UHI effect. These findings underscore the importance of integrating high-resolution climate modeling into urban planning and developing targeted adaptation strategies based on future UHI patterns to address climate challenges. Full article

Land cover, topography, precipitation, and socio-economic factors exert both direct and indirect influences on urban land surface temperatures. Within the broader context of global climate change, these influences are magnified by the escalating intensity of the urban heat island effect. However, the interplay and underlying mechanisms of natural and socio-economic determinants of land surface temperatures remain inadequately explored, particularly in the context of cold-region cities located in the northern temperate zone of China. This study focuses on Changchun City, employing multispectral remote sensing imagery to derive and spatially map the distribution of land surface temperatures and topographic attributes. Through comprehensive analysis, the research identifies the principal drivers of temperature variations and delineates their seasonal dynamics. The findings indicate that population density, night-time light intensity, land use, GDP (Gross Domestic Product), relief, and elevation exhibit positive correlations with land surface temperature, whereas slope demonstrates a negative correlation. Among natural factors, the correlations of slope, relief, and elevation with land surface temperature are comparatively weak, with determination coefficients (R²) consistently below 0.15. In contrast, socio-economic factors exert a more pronounced influence, ranked as follows: population density (R² = 0.4316) > GDP (R² = 0.2493) > night-time light intensity (R² = 0.1626). The overall hierarchy of the impact of individual factors on the temperature model, from strongest to weakest, is as follows: population, night-time light intensity, land use, GDP, slope, relief, and elevation. In examining Changchun and analogous cold-region cities within the northern temperate zone, the research underscores that socio-economic factors substantially outweigh natural determinants in shaping urban land surface temperatures. Notably, human activities catalyzed by population growth emerge as the most influential factor, profoundly reshaping the urban thermal landscape. These activities not only directly escalate anthropogenic heat emissions, but also alter land cover compositions, thereby undermining natural cooling mechanisms and exacerbating the urban heat island phenomenon. Full article

During hypersonic flight, the air rudder shaft can undergo huge aerodynamic heating load, where it is necessary to design the thermal protection system of the air rudder shaft. Aiming to prevent the rudder shaft from thermal failure due to the heat endurance limit of materials, numerical investigations are conducted systemically to predict the active cooling performance of the rudder shaft with liquid water considering phase change. The validation of the numerical simulation method considering phase-change heat transfer is further investigated by experiments. The effect of coolant injection flow velocity on the active cooling performance is further analyzed for both the steady state and transient state. Finally, to achieve better cooling performance, an optimized design of the cooling channels is performed in this work. The results of the transient numerical simulation show that, employing the initial cooling structures, it may undergo the heat transfer deterioration phenomenon under the coolant injection velocity below 0.2 m/s. For the rudder shaft with an optimized structure, the heat transfer deterioration can be significantly reduced, which significantly reduces the risk of thermal failure. Moreover, the total pressure drop of the optimized rudder shaft under the same coolant injection condition can be reduced by about 19% compared with the initial structure. This study provides a valuable contribution to the thermal protection performance for the rudder shaft, as a key component of aircraft under the aero heating process. Full article

This study focuses on the phenomenon of boiling heat transfer during fluid flow (Fluorinert FC-72) in minichannels. The research stand was built around a specially designed test section incorporating sets of aligned minichannels, each 1 mm deep. These channel arrays varied in number, comprising configurations with 7, 15, 17, 19, 21, and 25 parallel channels. The test section was vertically orientated with upward fluid flow. To address the heat transfer problem associated with transient flow boiling, two numerical approaches grounded in the finite element method (FEM) were employed. One used the Trefftz function formulation, while the other relied on simulations performed using the commercial software ADINA (version 9.2). In both approaches, the heat transfer coefficient at the interface between the heated foil and the working fluid was determined by applying a Robin-type boundary condition, which required knowledge of the temperatures in both the foil and the fluid, along with the temperature gradient within the foil. The outcomes of both FEM-based models, as well as those of a simplified 1D method based on Newton’s cooling law, yielded satisfactory results. Full article

The urban heat island (UHI) effect significantly impacts urban environments, particularly along roads, a phenomenon known as urban linear heat (UHI_ULI). Numerous factors contribute to roads influencing the UHI_ULI; however, effective mitigation strategies remain a challenge. This study examines the relationship between canopy cover percentage, normalized difference vegetation index, land use types, and three road typologies (local, regional, and state) with land surface temperature. This study is based on data from the city of Adelaide, Australia, using spatial analysis, and statistical modelling. The results reveal strong negative correlations between land surface temperature and both canopy cover percentage and normalized difference vegetation index. Additionally, land surface temperature tends to increase with road width. Among land use types, land surface temperature varies from highest to lowest in the order of parkland, industrial, residential, educational, medical, and commercial areas. Notably, the combined influence of the road typology and land use produces varying effects on land surface temperature. Canopy cover percentage and normalized difference vegetation index consistently serve as dominant cooling factors. The results highlight a complex interplay between built and natural environments, emphasizing the need for multi-factor analyses and a framework based on the local climate and the type of roads (local, regional, and state) to effectively evaluate UHI_ULI mitigation approaches. Full article