Search Results (7,736)

Heat treatment is a thermal-processing method involving controlled heating and cooling cycles designed to achieve the desired properties of materials. Among these steps, the cooling rate in heat treatment plays a crucial role, as it significantly influences the resulting material properties. In this paper, we investigated the feasibility of random forests in estimating the cooling-rate parameters for the steel-part heat treatment process. Random forests are particularly appealing in modeling an ensemble of expressive decision trees from which cooling can be modeled and estimated from the interaction of metal features. Our computational experiments using real-world data from industrial-scale operations demonstrated the advantageous properties of random forest regression models, particularly when combined with a random oversampling scheme. We also found that the chemical composition—specifically carbon and chromium content—as well as the weight of the steel parts, are key features that predict the cooling rate of steel parts. Furthermore, our validation using real-world cooling scenarios aligned closely with the practical insights of seasoned operators who routinely recommend cooling parameters for the metal-normalizing process. Our results highlight the effectiveness of the ensemble approach of random forest for practical applicability in industrial-scale heat treatment. Full article

There is growing interest in utilising urban parks as nature-based solutions to mitigate the effects of climate change and rising temperatures by improving thermal comfort. Nonetheless, understanding remains limited on how different park configurations influence summer thermal comfort, particularly under future warming scenarios. This novel study evaluates park configurations across different neighbourhood layouts within Perth’s Mediterranean climate under both present and future conditions. Study precincts were modelled and simulated using ENVI-met version 5.5 for an average current summer day, based on 25 years of local weather data and climate projections for 2090 under the Representative Concentration Pathway 8.5 scenario, representing the worst-case scenario. Results showed that park surfaces were consistently cooler than surrounding streets based on LST; however, this did not always translate into improved thermal comfort, as exposed grass areas often exhibited high Physiological Equivalent Temperature (PET) values. PET has been confirmed as the most suitable outdoor human thermal comfort index. Canopy cover and vegetation type, particularly tall trees and bushland, were more influential than park size or configuration in enhancing thermal comfort. These findings provide evidence-based insights, highlighting the importance of strategies that prioritise tree canopy coverage to enhance urban cooling and resilience to climate change. Full article

During the laser cladding process, the distribution of the temperature field directly influences the morphology, microstructure, and residual stress state of the cladding layer. However, the process involves transient characteristics of rapid heating and cooling, making it challenging to study temperature field variations directly through experimental methods. Therefore, numerical simulation has become a crucial tool for gaining a deeper understanding of the laser cladding mechanism, providing theoretical basis and guidance for optimizing process parameters. This study systematically integrates COMSOL Multiphysics coupling simulation with Jmatpro material thermal property data to perform simulations of temperature field evolution, melt pool flow behavior, and Marangoni effects during laser cladding of nickel-based alloy (IN718) onto an EA4T steel substrate. It highlights the influence patterns of different process parameters (e.g., laser power, scanning speed) on the temperature gradient and flow characteristics of the molten pool, providing an in-depth theoretical basis for understanding the formation mechanism of the molten pool and microstructure control. Full article

Passive design strategies incorporating phase change materials (PCM) provide effective thermal energy storage, improve indoor comfort, and reduce building energy demand. This study aimed to evaluate the effectiveness of partially filled PCM glazing systems in stabilizing indoor thermal comfort under Korean climate conditions, testing the hypothesis that partial integration can provide meaningful diurnal temperature regulation without compromising daylight access. Indoor air, interior and exterior glazing surfaces, and the PCM layer were monitored to evaluate heat transfer, while EnergyPlus simulations extended the analysis to seasonal conditions. The PCM model was developed using the Conduction Finite Difference (CondFD) algorithm and validated against experimental data, reliably reproducing dynamic phase change behavior. Field tests with a 28 °C PCM showed reductions in indoor peak temperatures of about 2.0 °C during daytime and increases of 1.5 °C at night. Under broader climatic simulations, the same PCM achieved up to 3.7 °C daytime reductions and 2.0 °C nighttime increases, depending on outdoor conditions. These findings highlight the potential of PCM-integrated glazing systems for adaptive thermal regulation in Korean climates and suggest broader applicability for passive cooling and heating strategies in buildings facing increasingly variable weather conditions. Full article

The aim of this work was to investigate the evolution of the mechanical integrity of the selected offshore oil reservoir during its life cycle. The geomechanical stability of the reservoir formation, including the caprock and base rock, was investigated from the exploitation phase through waterflooding production to the final phase of enhanced oil recovery (EOR) with CO₂ injection. In this study, non-isothermal flow simulations were performed during the process of cold water and CO₂ injection into the oil reservoir as part of the secondary EOR method. The analysis of in situ stress was performed to improve quality of the geomechanical model. The continuous changes in elastic and thermal properties were taken into account. The stress–strain tensor was calculated to efficiently describe and analyze the geomechanical phenomena occurring in the reservoir as well as in the caprock and base rock. The integrity of the reservoir formation was then analyzed in detail with regard to potential reactivation or failure associated with plastic deformation. The consideration of poroelastic and thermoelastic effects made it possible to verify the development method of the selected oil reservoir with regard to water and CO₂ injection. The numerical method that was applied to describe the evolution of an offshore oil reservoir in the context of evaluating the geomechanical state has demonstrated its usefulness and effectiveness. Thermally induced stresses have been found to play a dominant role over poroelastic stresses in securing the geomechanical stability of the reservoir and the caprock during oil recovery enhanced by water and CO₂ injection. It was found that the injection of cold water or CO₂ in a supercritical state mostly affected horizontal stress components, and the change in vertical stress was negligible. The transition from the initial strike-slip regime to the normal faulting due to formation cooling was closely related to the observed failure zones in hybrid and tensile modes. It has been estimated that changes in the geomechanical state of the oil reservoir can increase the formation permeability by sixteen times (fracture reactivation) to as much as thirty-five times (tensile failure). Despite these events, the integrity of the overburden was maintained in the simulations, demonstrating the safety of enhanced oil recovery with CO₂ injection (EOR-CO₂) in the selected offshore oil reservoir. Full article

Urban green spaces provide measurable cooling that can mitigate urban heat islands, yet few studies have quantified these effects over multiple decades. This study analyzed Landsat imagery from four epochs (1990, 2000, 2013, 2018) to derive land surface temperature (LST) and vegetation indices—NDVI for greenness and NDMI for moisture content—for four large urban parks in Krakow. Late spring/summer LST in parks was compared with that of urban areas within 0–150 m and 150–300 m of park boundaries. Statistical significance was evaluated using bootstrapped confidence intervals, long-term trends were assessed via the Mann–Kendall test, and correlation analysis was used to examine relationships between LST and each vegetation index. Results show a persistent park cooling effect, with park interiors ~2–3 °C cooler than adjacent urban areas in all years. Despite an overall city-wide LST rise of ~5–6 °C from 1990 to 2018, the park cool island intensity (temperature difference between park and city) remained stable (no significant long-term trend, p > 0.7). Bootstrapped 95% confidence intervals confirmed that each park’s cooling effect was statistically significant in each year analyzed. NDMI (vegetation moisture content) correlated more strongly with LST (r ~ −0.90) than NDVI (r ~ −0.7 to −0.9), highlighting the importance of vegetation moisture in park cooling. These findings demonstrate that well-watered urban parks can sustain substantial cooling benefits over decades of urban development. The persistent ~2–3 °C daytime cooling observed underscores the value of water-sensitive green space planning as a long-term urban heat mitigation strategy. Full article

The sustainable rehabilitation of existing buildings is essential to achieve urban resilience, resource efficiency and seismic risk reduction. This study investigates an integrated retrofit strategy that combines vertical extension with inter-story isolation to simultaneously enhance seismic performance and energy efficiency, creating additional usable space without additional land consumption. The inter-story isolation mechanism reduces seismic demand by decoupling a new and existing structure and introducing beneficial damping effects, whereas vertical extension improves a building’s envelope to reduce energy demands for heating and cooling. A tailored design methodology for integrated intervention is presented, according to which, for the structural part, a two-degrees-of-freedom dynamic model is adopted to design the characteristics of the isolation layer. The methodology is applied to a case-study building located in L’Aquila, Italy, where two alternative vertical extensions, one rigid and one lightweight, are analyzed. Time-history analyses and energy simulations for annual primary energy demand are carried out to assess the structural and thermal performance of the integrated retrofit. The results indicate that the proposed solution can reduce top-floor acceleration by up to 35%, inter-story drift by 30–35%, base shear by over 30% and primary energy demand by 11%, demonstrating its effectiveness in improving both seismic safety and energy performance. The main novelty of this study lies in the systematic integration of inter-story isolation with building envelope enhancement through vertical extension, offering a unified design framework that merges structural and energy retrofitting objectives into a single sustainable intervention. Full article

Kinetic façades represent a climate-responsive design solution that improves building adaptability by responding to seasonal needs such as daylighting and shading. They offer an attractive retrofit strategy that improves both the esthetics and environmental performance of buildings. This study investigated the integration of an origami-inspired kinetic façade into a student dormitory building located in Dhahran, Saudi Arabia. Using numerical simulations, 35 façade configurations were analyzed under varying conditions of façade orientations, closure ratios (from 5% to 95%), and cavity depths (from 20 cm to 100 cm). The findings highlight the critical impact of kinetic façade design characteristics on daylight availability and solar exposure and the required trade-off between these two variables. In this context, this study observed that at higher façade closure ratios, increasing cavity depth could effectively mitigate daylight reduction by promoting reflected daylight penetration inside the cavity. As for heat gains and cooling load reduction, mid-range façade closure, 50 cm in this study, achieved balanced performance across the three examined orientations. However, the southern façade showed slightly higher efficiency compared to the eastern and western façades, which achieved lower cooling reductions and showed a similar UDI compromise. Thus, a dynamic façade operation is recommended, where higher closure ratios could be applied during peak solar hours on the east in the morning and the west in the afternoon to maximize cooling savings, while moderate closure ratios can be maintained on the south to preserve daylight. Future work should incorporate real-time climatic data and smart control technologies to further optimize kinetic façade performance. Full article

Phase-change materials (PCMs) are integral to the thermal energy storage devices used in phase-change storage air-conditioning systems, but their adoption is hindered by slow heat transfer rates and suboptimal energy storage efficiency. In this study, we design and analyze a flat-panel thermal energy storage device based on PCM, using both numerical simulations and experimental testing to evaluate performance under various operating conditions. The simulations, conducted using computational fluid dynamics (CFD) in a steady-state environment with an inlet temperature of 12 °C, demonstrate that the phase-change completion time for cooling storage is 8331 s, while the cooling release process is completed in 3883 s. The fluid distribution within the device is found to be uniform, and the positioning of the inlet and outlet has a minimal effect on performance metrics. However, the lateral stacking configuration of PCM units significantly improves heat transfer efficiency, increasing it by 15% compared to vertical stacking arrangements. Experimental tests confirm that increasing the inlet flow rate accelerates the phase transition process but has a marginal impact on overall energy utilization efficiency. These results provide valuable quantitative insights into optimizing the design of phase-change thermal storage devices, particularly in terms of enhancing heat transfer and overall energy efficiency. Full article

This paper theoretically and numerically investigates temperature-dependent band structures in elastic metamaterial lattices using a plane wave expansion method incorporating thermal effects. We first analyze a one-dimensional (1D) elastic metamaterials beam, demonstrating that band frequencies decrease with rising temperature and increase with cooling. Then, the method is extended to square and rectangular 2D lattices, where temperature variations show remarkable influence on individual bands; while all bands shift to higher frequencies monotonically with cooling, their rates of change diminish asymptotically as they approach characteristic limiting values. Band structure predictions are validated against frequency response simulations of finite-structure. We further characterize temperature dependence of bands and bandgap widths, and quantify thermal sensitivity for the first four bands. These findings establish passive, robust thermal tuning strategies for ultralow frequency vibration suppression, offering new design routes for space-deployed lattice structures. Full article

This study introduces Internal Induction Heating (In-IH) as an efficient method for local mold temperature control in thin-walled polypropylene (PP) injection molding. Unlike conventional systems that are slow and energy-intensive, the insert is integrated directly into the induction circuit in the In-IH system, generating eddy currents for rapid and localized heating. Numerical and experimental analyses were performed to examine the effects of insert geometry and heating parameters; it was found that thinner inserts achieved higher surface temperatures—the 0.5 mm insert reached ~550 °C, while the 2.0 mm insert reached only ~80 °C—confirming an inverse relationship between thickness and temperature. Narrower inserts (25 mm) concentrated heat more effectively, whereas wider ones yielded better temperature uniformity. The cooling conditions strongly affected the temperature gradients. Mold-filling experiments demonstrated that In-IH significantly improved the flowability of PP: at 180 °C, the 0.4 mm specimen achieved a flow length of 85.33 mm, compared with 43.66 mm for the 0.2 mm specimen. At 250–300 °C, all samples approached full filling (~100 mm). The simulation and experimental results agreed, with a maximum deviation of 10%, confirming that In-IH provides rapid, energy-efficient, and precise temperature control, thus enhancing melt flow and product quality for thin-walled PP components. 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

This study investigates a wallboard integrating encapsulated phase change materials (PCMs) within aluminum honeycomb cells to reduce building energy consumption. The thermal performance of a concrete wall enhanced with this PCM-honeycomb composite was evaluated under varying weather conditions through a two-dimensional heat transfer model. The thermal improvement of PCM is revealed in a comparative analysis of three distinct building envelope materials, i.e., concrete, concrete covered by the honeycomb wallboard, and concrete covered by the honeycomb wallboard containing PCMs. The results demonstrated that the PCM-honeycomb wallboard effectively delays and reduces peak cooling loads. The proposed system lowered building energy consumption by 28.46% and 32.12% in energy consumption over the entire summer season (and 5.76% and 6.27% over one year), respectively, compared to these reference cases. Among the tested PCMs, RT25 was identified as the most effective. The results confirm that incorporating PCM-infused honeycomb wallboards into building envelopes is a viable strategy for passive, year-round temperature regulation. Full article

Reducing energy consumption in buildings presents a challenge for the construction and architectural industries. Stakeholders in the building sector require innovative products and systems to reduce energy usage effectively. Building Energy Simulation (BES) tools are essential for understanding energy-related issues during the design phase. However, the existing BES tools are often complex and costly, making them inaccessible to many architects and engineers who lack the software expertise for integrating new systems into existing Building Energy Simulation frameworks. To address this gap, the authors of this article have developed a new tool that enables early-stage evaluation of building performance. Additionally, the tool includes Water Flow Glazing (WFG) as a construction element that is part of both the facade and the building’s heating and cooling system. The authors validated the methodology by comparing the results from the new tool with those from the commercial BES tool Indoor Climate and Energy IDA-ICE 5.0 in accordance with ASHRAE standards. The same cases were tested by comparing the indoor temperature of a room with the power absorbed by the water, as measured by both tools. A WFG facade can effectively help maintain comfortable room temperatures throughout both winter and summer while producing renewable thermal energy via water heat absorption. The accuracy of this tool was validated using the normalized root mean square error between results from the new tool and those from IDA-ICE 5.0, which remained below the maximum allowable error established by ASHRAE. Validation of the tool using an experimental prototype showed that a coefficient of determination (R²) of 0.91 can be achieved through iterative refinement between the model and measured data. Full article

Colombo, a rapidly urbanizing city, increasingly faces the Urban Heat Island (UHI) effect due to urban expansion and climate change. Urban parks mitigate UHI by creating cool microclimates, quantified as Park Cool Island Intensity (PCII), the temperature difference between parks and surrounding areas. Colombo exhibits an average cooling effect of 0.98 °C $\pm 0.21\%$. The results found that the park area has the most significant positive relationship with the PCII, where the model explained 87.7% of the variance (R² = 0.877), indicating a strong fit, following the park perimeter (R² = 0.811). Park vegetation characteristics exert a significant influence to enhance the cooling effect, with canopy density emerging as a primary factor with a variance of 87.1% (R² = 0.871). Notably, canopy density of more than 80% demonstrates a marked PCII exceeding 1.0 °C. Additionally, other vegetation attributes, tree basal area (R² = 0.868), tree height (R² = 0.784), DBH (R² = 0.757), and stem density (R² = 0.717), exhibit a significant positive correlation with PCII, following canopy density in descending order. Furthermore, park composition analysis reveals that higher water and green cover contribute to maximizing PCII, underscoring the importance of reducing impervious cover in urban park design. These findings provide valuable insights for urban planners in facilitating the development of more effective urban park designs aimed at maximizing cooling effects, promoting sustainable urban development, and contributing to the achievement of SDG 11 and SDG 13. Full article