Search Results (2,323)

This study investigates the aerodynamic and thermal impacts of tire sidewall cooling fins on a passenger vehicle using high-fidelity computational fluid dynamics (CFD) simulations. Continuous heat accumulation from tire rotation and road friction can degrade structural durability. To address this thermal challenge, a parametric study was conducted on the DrivAer notchback vehicle model across various fin angles from −67.5° to 67.5°. The results revealed a distinct design space that offers simultaneous aero-thermal improvements. Specifically, the 22.5° fin configuration demonstrates a dual-benefit performance, achieving a 3.79% net reduction in overall vehicle drag alongside a 17.36% increase in the average heat transfer coefficient (HTC). Conversely, the −22.5° configuration yields the maximum cooling enhancement with a 30.49% increase in average HTC but incurs a 2.52% drag penalty. Microdrag and Turbulent Kinetic Energy (TKE) analyses successfully explain the underlying fluid mechanisms governing these trade-offs. These findings provide practical design guidelines for flow control on rotating wheels, showing that tire sidewall geometries can enhance full-vehicle aerodynamic efficiency and tire thermal reliability. Full article

In Mediterranean countries such as Portugal, summer heatwaves increasingly threaten agricultural productivity by disrupting crop physiological processes. Greenhouse cultivation often exacerbates heat stress, while conventional cooling systems such as air conditioning and evaporative cooling impose unsustainable energy demands. This study investigates an Earth-to-Air Heat Exchanger (EAHE) system consisting of a five-tier helical PVC pipe configuration (29 m, buried at a depth of 3 m), installed in a prototype polycarbonate greenhouse in Covilhã, Portugal, and monitored under real summer conditions. Four ventilation scenarios were simulated in EnergyPlus 25.1, and a segmented NTU thermal model, implemented as a Python plugin via the pyenergyplus API, predicted the EAHE outlet temperature with CV(RMSE) values of 1.47% at 30 m³/h and 3.0% at 50 m³/h. The IPMA meteorological dataset provided the best simulation accuracy (RMSE = 2.31 °C, R² = 0.978). In simulations based on the experimentally calibrated models, EAHE preconditioning reduced accumulated heat stress degree-hours above 28 °C by 9.1 to 9.5% and lowered peak indoor temperature by up to 2.60 °C, at system COPs of 6.9 to 10.6, which are 2.3 to 3.5 times higher than conventional vapour-compression cooling; propagated measurement uncertainties confirm the robustness of this COP advantage. A model-based parametric scale analysis indicated that geometrically scaled circuits (DN200, DN400) achieve degree-hour reductions of 67 and 91%, supporting EAHE scalability through geometric proportioning, pending experimental validation at larger scales. Full article

Heat stress severely hinders citrus yield and fruit quality. This study employed integrated physiological and transcriptomic analyses to investigate the effects of the exogenous application of abscisic acid (ABA) and brassinosteroid (BR) on heat stress responses in citrus. The results showed that the exogenous application of ABA and BR increased the contents of soluble sugar, proline, and ABA, and enhanced the activities of peroxidase and catalase under heat stress. Transcriptome trend analysis identified profiles 1, 6, and 7 as significantly enriched across exogenous ABA, BR, and control conditions. Profile 6 exhibited rapid upregulation followed by stabilization and showed a significantly higher gene count under both ABA and BR treatments than under the control. KEGG enrichment analysis revealed that genes in profile 6 were primarily enriched in amino sugar, nucleotide sugar, galactose, amino acids, 2-oxocarboxylic acid, glycerophospholipid, glucosinolate metabolism, MAPK signaling pathway, plant hormone signal transduction, protein processing in the endoplasmic reticulum, plant–pathogen interaction, and endocytosis. Furthermore, four genes encoding heat shock proteins (HSP), including HSP21A, HSP21B, HSP70-17, and HSP70A, were induced under heat stress and showed significant upregulation in response to exogenous ABA and BR treatments. In conclusion, these findings indicated that exogenous ABA and BR regulated ABA and osmoprotectant accumulation and antioxidant defense activation in response to heat stress. Full article

This study presents the results of long-term field experiments investigating the effects of subsurface heating and irrigation with discharged warm water (28–35 °C) on the hydrothermal, redox, biological, and salt regimes of Haplic Chernozem (Loamic, Endocalcaric) in the central Forest-Steppe zone of Ukraine. The experiments were conducted under contrasting hydro-meteorological conditions, allowing assessment of thermo-reclamation practices across a wide range of temperature and soil moisture regimes. Subsurface heating increased soil temperature by 7.3–11.1 °C at the depth of heating pipe installation, while the thermal effect gradually decreased with increasing distance from the heat source. Combined heating and irrigation created a more uniform temperature distribution within the root zone, reduced the depth and duration of soil freezing, and improved hydrothermal conditions throughout the growing season. The studied soils maintained predominantly oxidative conditions under all treatments. However, the combined application of heating and irrigation promoted a more homogeneous distribution and seasonal stabilization of soil redox potential throughout the profile. Soil heating also enhanced microbiological activity, thereby increasing cellulolytic activity, particularly during cold and dry periods when soil temperature and moisture limited microbial processes. Irrigation with slightly mineralized warm wastewater did not cause significant overall soil salinization but resulted in the redistribution of calcium and sodium within the soil profile. Subsurface heating intensified the seasonal dynamics of readily soluble salts, promoting their temporary accumulation near the heating pipes, whereas combined heating and irrigation facilitated subsequent leaching of excess salts into deeper horizons. The integrated application of subsurface heating and irrigation produced the highest and most stable perennial grass productivity, increasing biomass yield by 87–163% compared with the control, irrespective of meteorological conditions. These findings demonstrate that the integrated use of industrial waste heat for subsurface heating combined with irrigation represents a promising and environmentally sustainable thermo-reclamation technology capable of improving soil functioning and agricultural productivity, provided that long-term monitoring of soil water–salt regimes is maintained. Full article

This study characterises the airtightness of school classrooms in several Spanish educational centres using blower-door measurements (ISO 9972:2015). Building envelope airtightness governs uncontrolled air infiltration and plays a central role in indoor air quality (IAQ): excessively permeable envelopes increase the ingress of outdoor pollutants such as PM_2.5, while highly airtight classrooms without adequate mechanical ventilation may accumulate indoor CO₂ and thermal discomfort. In Mediterranean climates, where mechanical ventilation is not systematically installed in schools, uncontrolled infiltration frequently becomes the dominant air renewal mechanism during the heating season. The measured classrooms show a mean n₅₀ of 9.08 h⁻¹ (range: 4.32–22.67 h⁻¹), placing them at an intermediate level in the international literature. High within-school variability was identified, indicating that single-classroom measurements may be insufficient to represent building-level airtightness. External façade area showed the strongest exploratory association with n₅₀ (Spearman ρ = 0.663, p = 0.037), but the small, non-random sample does not support generalising this relationship beyond the measured classrooms. The paired comparison in Centre C4 did not suggest an airtightness improvement beyond measurement uncertainty after the specific ETICS intervention, while the C5 case illustrates the potential influence of unsealed service penetrations. Overall, the observations point to windows, junctions and service penetrations as priority locations for diagnosis and targeted sealing, to be verified in larger and more diverse samples. Full article

Ultra-processed foods expose consumers to heat-induced contaminants like 5-hydroxymethylfurfural (5-HMF), which impairs intestinal homeostasis via oxidative stress and inflammation. This study quantified 5-HMF in bakery products and evaluated blueberry polyphenols’ capacity to attenuate 5-HMF-induced cellular stress in an in vitro Caco-2 intestinal model. 5-HMF levels in commercial bakery products were determined using a colorimetric assay and HPLC-UV. Differentiated Caco-2 cells were exposed to 5-HMF (0.4 mM) for 48 h, alone or co-treated with blueberry juice (15 µg/mL of phenol equivalents). ROS production, lipid accumulation, gene expression of antioxidant, lipid, and inflammatory markers, and NF-κB/ERK signaling pathways were analyzed. HPLC-UV accurately quantified 5-HMF in bakery products (exceeding 2 mg/100 g), revealing systematic overestimation by the colorimetric method. In Caco-2 cells, 5-HMF significantly increased ROS, lipid accumulation, inflammatory cytokines (NLRP3, IL1B, and IL18), and activated NF-κB and p-ERK. Co-treatment with blueberry juice reduced ROS and lipids, upregulated the NRF2 antioxidant pathway, and drastically suppressed NF-κB -mediated inflammation. 5-HMF induced markers of metabolic dysfunction, oxidative stress, and inflammation in the intestinal epithelial model. Polyphenol-rich blueberry juice attenuated 5-HMF-induced alterations at the tested concentration, suggesting a potential protective nutritional strategy against epithelial stress associated with food-processing contaminants. Full article

Increasing planting density is an effective strategy for improving maize (Zea mays L.) productivity, but it can also intensify interplant competition and canopy shading. Enhanced nitrogen application may help offset these negative effects. A two-year field experiment was conducted in the Hexi Corridor, an arid region of northwestern China, using a full factorial design with three planting density levels D1 (75,000 plants ha⁻¹), D2 (90,000 plants ha⁻¹), and D3 (105,000 plants ha⁻¹), and three nitrogen application levels N1 (198 kg ha⁻¹), N2 (264 kg ha⁻¹), and N3 (330 kg ha⁻¹). The aim was to clarify how the interaction between planting density and nitrogen application regulates maize canopy structure and affects resource use efficiency in arid areas. The results showed that planting density, nitrogen rate, and their interaction significantly affected canopy structure, photosynthetic traits, grain yield, and water and nitrogen use efficiency. From the perspective of each growth stage, combinations of medium and high planting density and nitrogen application levels facilitated the optimization of maize canopy structure, promoted plant growth and dry matter accumulation, and elevated leaf SPAD values. Meanwhile, treatment D2N2 exhibited the most prominent improvement in maize yield components, with grain yield increased by 1.44–35.58% on average across experimental years. This treatment also sustained superior water and nitrogen use efficiency, achieving an average water use efficiency of 3.53 kg·m⁻³ and an average partial factor productivity of nitrogen of 53.41 kg·kg⁻¹. Comprehensive multi-index evaluation verified that D2N2 represented the optimal cultivation regime. This regime could reduce nitrogen fertilizer input by 20% while fully exploiting light and heat resources inherent to arid regions. Collectively, this study establishes a viable green and high-efficiency cultivation paradigm for maize production with high yield, reduced fertilizer input and water conservation, and delivers critical theoretical and technical references for the sustainable intensification of maize cultivation in arid regions of northwest China. Full article

Internal temperature distributions in black tea fermentation regulate enzymatic oxidation, heat accumulation and fermentation uniformity, but continuous three-dimensional measurements remain difficult in practical processing. We developed a CFD-prior-constrained physics-informed neural network (PINN + CFD) to reconstruct the three-dimensional thermal state of a 1.35 m × 0.96 m × 0.08 m fermentation bed under sparse sensing. Nine sensors at z = 0.04 m were used for training, and six held-out depth-wise sensors at z = 0.02 m and z = 0.06 m were reserved for depth-wise validation. The model integrated measured temperatures, transient heat-transfer physics, convective boundary conditions and a CFD-derived volumetric soft spatial prior, which guided spatial extrapolation rather than serving as ground-truth temperature data. Although the multilayer perceptron achieved the lowest fitting error at the instrumented z = 0.04 m plane, PINN + CFD showed better depth-wise extrapolation, with RMSEs of 0.128, 0.129 and 0.296 °C across the three stages. However, its advantage was stage- and validation-target-dependent: the baseline PINN was slightly better in part of the dynamic-stage validation, and standalone CFD had the lowest surface infrared error in the constant-temperature stage, indicating that PINN + CFD mainly improved spatial extrapolation rather than uniformly minimizing all error metrics. The inferred apparent process-level heat-source index Q_react(t) varied continuously, and its cumulative trajectory showed a descriptive association with cumulative polyphenol loss. These results indicate that PINN + CFD enables physically consistent thermal-state reconstruction within the tested sparsely instrumented black tea fermentation bed. Full article

As rooftop photovoltaic (PV) systems are increasingly deployed on taller buildings and across a wider range of building applications, localized overheating or initial fires caused by electrical faults, combustible roof-covering materials, or maintenance-related ignition sources may affect PV modules and contribute to subsequent fire spread over the rooftop system. In this study, a full-scale fire experiment was conducted on a flat-laid rooftop PV system using a nominal 100 kW n-heptane pan fire as a controlled localized external fire source to investigate the fire development and escalation mechanism of the system. The results show that the fire hazard was first and primarily concentrated in the confined under-panel space: the average cavity peak temperature of the ignited array reached 684.0 °C, with a local maximum of 853.4 °C, both significantly higher than the maximum upper-surface center temperature of 370.7 °C. The involvement of the waterproofing membrane in combustion was the key amplifying mechanism driving the transition from localized heating to a sustained high-temperature event; the average cavity temperature exceeded 500 °C after 234 s and remained above this threshold for approximately 201 s, with an average cavity heat accumulation index of 178.1 × 10³ °C·s. Compared with the lower upper-surface center measuring points, hazardous temperatures beneath the modules were reached earlier by 149, 193 and 247 s at the thresholds of 50, 100 and 200 °C, respectively. Under the tested configuration, these findings provide engineering insights for fire-risk identification, early monitoring, and fire-safe design of flat-laid rooftop PV systems in high-rise building applications. Full article

Heavy metal (HM) contamination of soils frequently occurs in combination with other environmental stressors, resulting in a cumulative effect that interferes with plant physiology, biochemistry, and development in a more severe and complex manner than the individual stressors alone. While there are many reviews that consider abiotic stress combinations broadly, this review focuses specifically on combined HM + abiotic stress conditions and classifies in terms of the effect on symptoms or induced defense mechanisms as additive, synergistic (exacerbated) or even antagonistic (counteracted). It is revealed that the combined stress response may depend on the way that each of the stresses presents itself to plant tissues, i.e., whether it is a chemical compound whose accumulation into roots may be regulated or a stress whose application is more general, such as heat stress or flooding (localized versus systemic, respectively). Combined localized stresses such as HMs and hydrocarbons tend to elicit synergistic responses, while localized + systemic stresses are more variable, tending toward antagonistic, such as HM and drought. Modern analysis tools indicate an overlap in or induction of unique response pathways that may alter depending on the conditions (intensity, duration and timing of exposure; greenhouse versus field conditions). The latest findings in mitigation techniques, ranging from chemical amendments and biological treatments, such as biochar and phytohormones, respectively, to genetic engineering, as also summarized. It is revealed that biochar and genetic approaches are both the most-widely used and the most effective. Full article

Understanding the physical mechanisms of compound hot-drought events (CHDEs) over the Yangtze River Basin (YRB) is essential for improving climate predictability. Using high-resolution observations and ERA5 reanalysis, this study conducted a three-dimensional comparative diagnosis of two spatially distinct CHDEs (August 2022 and 2019), deconstructing their circulation dynamics and thermodynamic budgets. Specifically, the 2022 basin-wide event was highly associated with La Niña and a negative Indian Ocean Dipole (NIOD). Anomalous latent heating in the tropical eastern Indian Ocean favored an extensive meridional Hadley circulation and a deep high-pressure belt, blocking southwest moisture transport. Thermodynamically, intense downward vertical motions produced severe descending adiabatic warming, which offset longwave radiational cooling and sustained anomalous heat accumulation throughout the deep troposphere. Conversely, the 2019 localized event occurred under a weak Central Pacific El Niño and a positive IOD. The anomalous tropical cooling weakened systematic subsidence and provided a favorable background for a Rossby wave train, featuring an offshore cyclone over the Western North Pacific that severed moisture pathways. Characterized by shallower vertical subsidence, the lack of a penetrative adiabatic heat source merely maintained a lower-level thermodynamic balance, confining extreme heat to the central–eastern YRB. Although superficially similar at the surface, these CHDEs are sustained by two distinct ocean–atmosphere interaction paradigms. Clarifying these dual paradigms provides a critical physical basis for improving sub-seasonal prediction. Full article

Photovoltaic–thermal (PVT) collectors co-generate electricity and heat—natural front ends for thermochemical energy storage (TCES)—provided the heat transfer fluid stays above the reactor’s desorption temperature. Using an eight-node model of a 0.6834 m² collector at 8.64° N whose thermal core is partially validated against measured data from the same tropical–coastal site (rooftop PV module temperature, RMSE 3.8 °C; prototype absorber-to-water heat transfer, RMSE 1.3 °C), flow-regulated to the ≈95 °C SrCl₂/NH₃ desorption threshold, we quantify the energy and exergy delivered for charging under tropical–monsoon intermittency. The 95 °C setpoint operation, the ≈5.3 h charging window, and all reported exergy yields are simulated: the built prototype delivered hot water peaking at 79 °C and did not reach the 95 °C setpoint. On a measured clear-sky day (clearness index K_t = 0.52), the collector yields 1.38 kWh of energy but only 0.43 kWh of exergy (first-law efficiency ≈ 38%; gross exergy efficiency ≈ 13%); across a 30-seed synthetic-intermittency ensemble, the exergy yield is 0.678 kWh at ≈14% gross exergy efficiency (≈52% combined first-law efficiency). In both cases, the thermal stream dominates the energy output while the electrical stream dominates the exergy output—on the sunlit day, the exergy is about 80% electrical—because 95 °C heat carries a Carnot factor (exergetic quality factor, 1 − T_a/T₇, at the instantaneous ambient dead state) of only ≈0.18 and an integrated Bejan/Kotas thermal-exergy quality of only ≈0.09. The controller holds the outlet within 1.4 K of the setpoint for ≈5.3 h, whereas no fixed flow in the 0.5–5.0 L min⁻¹ range ever reaches it: feedback control is a structural enabler, not an optimisation. On overcast days, the threshold is never reached and charging heat collapses to zero, leaving a PV-only generator. Exergy delivery is nonetheless nearly controller-independent: the accumulated exergy delivery deficit after a 50% irradiance drop is 937 kJ, a controller-independent value changing only 1.3% across a systematic 4 × 4 gain sweep (K_p 0.33–2.7×, K_d 0.25–5× of nominal), and predictive control improves it by ≤1%. For PVT–TCES at this scale, the decisive lever is deployability, not control sophistication. Full article

Confining a phase-change material (PCM) within a polymer shell yields leak-proof, mechanically robust latent-heat storage media, but selecting a shell chemistry and polymerization route requires balancing competing targets: latent-heat storage density (ΔH, the melting enthalpy per unit capsule mass), core loading content (LC), capsule diameter (d), and a melting temperature (T_m) matched to the application. Because the literature characterizes each method–shell–core combination in isolation, these structure–property relationships cannot be compared quantitatively across studies. We present a proof-of-concept, data-driven framework linking shell and process descriptors to encapsulation performance. From a curated dataset of 90 micro- and nano-encapsulated PCM records (53 with measured ΔH) spanning 11 encapsulation routes and eight shell material families, Random Forest (RF) and Gaussian Process (GP) surrogates predict ΔH, and a non-dominated sorting genetic algorithm (NSGA-II) optimizes ΔH, LC, and d over the continuous (T_m, LC) space for every method–shell–core trio with at least three records (n = 11). Benchmarked against mean, linear-LC, and physics-informed baselines under repeated cross-validation, the surrogates match but do not exceed the elementary baselines (median R² ≈ 0.33), a result we report honestly given the modest sample size. The Matérn GP provides borderline-calibrated uncertainty, supporting a robust, extrapolation-penalizing NSGA-II. Hypervolume rankings place emulsion polymerization, sol–gel silica, and in situ polymerization as the top-performing methods under both nominal and robust criteria. Presented as a methodology demonstration rather than a definitive ranking, the framework, with full code and data, is a reusable approach for structure–property quantification of polymer-encapsulated PCMs as experimental data accumulate. Full article

This study evaluates the influence of seasonal harvesting conditions on biomass productivity, oil yield, and biodiesel-related FAME composition of native microalgae—predominantly Chlorella sp., with minor populations of Scenedesmus and Ankistrodesmus—cultivated in an open raceway pond integrated into a pig-slurry biogas plant in Soria, Spain. Processing biomass harvested across four seasons showed that oven drying at 45 °C yields stable seasonal biomass concentrations around 7.80–8.80 g/L, while extended outdoor air-drying during spring and summer reduces yields to 2.86 and 4.33 g/L due to the absence of active growth conditions. Lipids extracted via the Soxhlet method using a dichloromethane: methanol mixture (9:1 v/v) exhibited a wide range of 2.5–18.9 g oil per 100 g dry biomass. Marked seasonal variations were observed: winter samples demonstrated an outstanding lipid accumulation capability, yielding the highest oil production (18.9 g/100 g biomass and 1.47 g/L) and a crude ester content reaching 60.75% FAMEs, which reached a maximum of 93.3 wt.% after purification via column chromatography. Conversely, spring, summer, and autumn samples suffered from limited lipid accumulation, with dry-basis oil yields remaining below 4.2 g/100 g biomass. Extensive characterization confirmed that the residual biomass has limited application as a solid fuel because of its low higher heating values (<10 MJ/kg⁻¹) and exceptionally high ash contents, which climbed from 15.98–60.02% to 41.14–51.91% after extraction. Full article

This study optimised the thermal performance of an air-cooled weapon turret control computer used in military missions by integrating experimental, numerical, and machine learning methods. To address thermal localisation and heat accumulation in high-power-density electronic components, two heat pipes with high effective thermal conductivity were embedded in the heat sink block. Based on numerical predictions, this configuration yielded an 8% thermal enhancement; however, its experimental verification remains a subject for future work. The accuracy of the three-dimensional Computational Fluid Dynamics model was validated within an acceptable error tolerance using experimental data from a physical prototype. To reduce the high computational cost of the parametric design space, Gaussian Process Regression, notable for its probabilistic nature, was employed as a surrogate model instead of traditional artificial neural networks, which tend to overfit small-scale deterministic data. The GPR model successfully mapped the system variance, demonstrating an extremely high coefficient of determination and a minimal margin of error in predicting the maximum chip temperature and system pressure drop. Cross-validation analyses conclusively demonstrated that the model has high generalisation capability without overfitting the dataset. Multi-objective Pareto optimisation was conducted by scanning a dense design grid generated over the trained continuous surrogate model. The optimal balanced design configuration identified along the Pareto front maintained the chip temperature within the safe zone, below the critical operating limit, while significantly reducing aerodynamic resistance on the fan, energy consumption, and noise issues, without compromising the system’s thermal performance. The developed GPR-based methodology offers a stable and reliable optimisation framework that minimises trial-and-error costs in the design of military thermal management systems. Full article