Search Results (5,065)

Aiming to improve cooling and dehumidification performance in air conditioning systems and to meet the trend toward environmentally friendly refrigerants, this study proposes a coupled system that combines a CO₂ transcritical refrigeration cycle (CTRC) with a liquid desiccant dehumidification cycle. The system takes advantage of high-grade waste heat from the exothermic side of the CTRC to drive the regenerating process of the liquid desiccant dehumidification. A cooling evaporator is adopted to cool indoor air, while another evaporator (i.e., Evaporator II) is utilized to cool the concentrated solution, improving dehumidification capacity and enabling independent control of sensible and latent heat loads. Through thermodynamic modeling and the exergy analysis model, a mathematical model of the system is developed to examine how key parameters (such discharge pressure and the CO₂ mass flow rate ratio in Evaporator II (λ)) affect performance and to analyze exergy loss features. Results show that the system’s coefficient of performance (COP) and dehumidification coefficient of performance (COP_deh) initially rise and then fall with increasing CTRC discharge pressure, achieving an optimal pressure of around 10,500 kPa (COP up to 4.32) under a specific working condition, surpassing those of standalone CTRC systems. Properly increasing λ enhances dehumidification capacity and energy efficiency, with a low specific dehumidification energy (SDE) of 0.2033 kWh/kg, indicating high economic efficiency. Most exergy losses occur in the CO₂-solution heat exchanger and dehumidifier (over 60% of total losses). The system’s maximum exergy efficiency reaches 12.4%, leaving room for further improvements. This coupled system offers an efficient, eco-friendly way for air conditioning in high-humidity environments, combining cooling and dehumidification with the potential for energy recovery. Full article

Battery thermal management is critical for electric vehicles operating in cold climates, where low temperatures reduce battery efficiency, limit regenerative braking and accelerate degradation. This study compares PTC heater and heat pump systems for battery thermal management in electric minibuses using optimization-based control strategies. A control-oriented model of the vehicle thermal system, validated against chassis dynamometer measurements, and a heat pump system model, validated against testbed measurements, are used to optimize thermal management strategies via nonlinear programming, minimizing energy consumption while accounting for Joule losses, regenerative braking energy and thermal system consumption. Battery degradation is evaluated using a Doyle-Fuller-Newman (DFN) electrochemical model incorporating physics-based degradation mechanisms. Results show that optimized thermal management strategies can simultaneously reduce energy consumption and degradation. With the PTC heater system, only marginal improvements are achievable, and further reductions in degradation come at the cost of increased energy consumption. In contrast, the more efficient heat pump system enables simultaneous reductions in both degradation and energy consumption through optimized thermal management. These findings highlight that advanced thermal management leveraging heat pump systems can enhance both driving range and battery lifetime in cold-climate electric vehicle operations. Full article

Recently, CuBa₂Ca₃Cu₄O_10+δ (Cu1234) has garnered significant interest owing to its distinctive triple-high superconducting properties (118K high T_c, combined with high J_c and high H_irr at liquid nitrogen temperature at ambient pressure) and potential for practical applications. The Cu1234 is initially synthesized at high pressures and is stable at a room temperature range but tends to decompose upon heating above 300 °C at ambient. In this study, we investigate the thermal stability of Cu1234 through annealing at various temperatures and oxygen pressures. It is found that Cu1234 starts to decompose at approximately 350 °C, 550 °C, and 600 °C when annealed at 1 bar, 100 bar, and 150 bar oxygen pressure, respectively. Prior to decomposition, however, the superconducting properties remain largely unchanged. The decrease in oxygen occupancy within the BaO layer of the BaCuO_3−δ charge reservoir block is proposed to be the primary cause of the structural instability of Cu1234, while higher oxygen pressures retard oxygen loss from this block. Our result suggests that the decomposition temperature of Cu1234 will further increase with higher oxygen pressure, e.g., possibly to 800 °C at 260 bar if a linear extrapolation is adopted. This study offers important insights for fabricating Cu1234 tapes via the powder-in-tube method. Full article

This study presents a comprehensive thermo-energetic and exergetic assessment of a 250 MW steam boiler in a Cuban thermal power plant, operating under partial load conditions (plant: 62–66%; boiler: 58–61%). An integrated diagnostic methodology was developed and implemented in Mathcad 15 to evaluate key performance indicators, including thermal efficiency (η_tGV); exergetic efficiency (η_ExGV); exergy destruction ratio (γ_ExGV); steam generation index (IG_v); and specific fuel consumption (B_Esp). The methodology was applied to two fuels with contrasting thermophysical and chemical properties: fuel oil and Enhanced Crude Oil 650. The results indicate superior performance with fuel oil due to its higher heating value; however, efficiency losses were mainly attributed to operational factors such as excessive air supply (22.7–26.4%), heat transfer surface fouling, and inadequate maintenance. The analysis revealed significant deviations from design values—thermal efficiency (90.27–90.59%) and exergetic efficiency (<60%)—highlighting an untapped potential for energy savings. Quantitative estimates indicate potential annual fuel cost savings of approximately 1.2 million USD through optimized combustion and maintenance practices. The proposed framework enables accurate diagnostics of complex boiler systems and provides actionable indicators to support combustion optimization and energy efficiency strategies in conventional thermal power plants. Full article

This study introduces a hybrid framework that integrates transient numerical simulations with artificial neural networks (ANNs) to analyze and predict heat transfer in building walls. The framework is applied to ten different material–insulation combinations. Using the Leapfrog–Hopscotch (LH) finite difference scheme, we evaluated dynamic heat transfer and identified optimal insulation thicknesses for buildings in the cold continental climate of Bukhara. An ANN model was trained and validated on a dataset generated from 410 simulated wall configurations. The model achieved high predictive accuracy, with a mean squared error below 0.005. The thickness of the outer material layer ranged from 20 cm to 35 cm, while the inner layer thickness varied from 1 cm to 3 cm. Among the materials analyzed, glass wool + steel and gypsum + brick demonstrated superior insulation performance by minimizing heat loss most effectively, with values as low as 361,234 W/m² and 4,983,441 W/m², respectively, at 35 cm wall thickness. These findings underscore the potential of combining ANN-based predictions with physics-based simulations to design energy-efficient building envelopes in cold climates. Full article

The continuous current dissipation of direct current grounding electrodes generates intense Joule heat, causing severe soil moisture loss and localized thermal runaway. Traditional static models ignore the temperature-dependent nature of soil parameters, leading to dangerous underestimations of actual temperature rises and thermal risks. To address this critical issue, this study establishes a bidirectional dynamic electro-thermal coupled model for a vertical grounding electrode using COMSOL Multiphysics. Comparative analysis demonstrates that the dynamic model accurately reproduces the late-stage accelerated temperature rise observed in experiments, proving its necessity over static methods. Simulations reveal that increased soil resistivity governs heat generation and directly causes a dramatic surge in both grounding resistance and maximum step voltage. In two-layer heterogeneous soils, current is forced into lower-resistivity regions, triggering extreme localized overheating. To mitigate this, expanding the cross-sectional radius of the coke bed effectively suppresses the thermal concentration. These findings provide quantitative evidence and non-uniform design guidelines for the safe operation and thermal protection of grounding electrodes under complex geological conditions. Full article

The Amazonian açaí waste is promising for producing charcoal through pyrolysis and bioenergy through combustion, but the property losses from its poor disposal in the environment remain unknown. Therefore, this work aimed to analyze how different storage conditions of the açaí waste over time, which mimic the reality throughout the Amazon, modify its bioenergetic properties. The samples were stored in a covered greenhouse for nine months in the following conditions: immersed in water, on the soil, and in open plastic bags. The biomass was analyzed by Fourier-transformed near-infrared spectroscopy, physical properties, stereomicroscopy, proximate composition, and thermogravimetry. The degraded waste showed endocarp attack and fungi proliferation. The chemical groups of primary cell wall components were concentrated, unlike water-soluble materials, raising the fixed carbon from 22% to 25% after 30 days. Consequently, higher heating values were kept (≈19 MJ/kg). However, water immersion storage sharply decreased the waste basic density from 0.81 g/cm³ to 0.56 g/cm³, dropping the energy density from 12 GJ/m³ to 8 GJ/m³. Moreover, storage raised ash content from 1.1% up to 1.9%. The storage hindered the start of the main phases of combustion and pyrolysis, which were later intensified, especially for soil-stored waste. Therefore, more stable combustion and pyrolysis require fresh waste. Besides natural drying, plastic bag storage over time kept the waste quality closer to that of the fresh waste. Full article

A 2D multiphase-flow coupling simulation model for preparing nanocrystalline ribbons using planar-flow casting (PFC) with a cooling roller was established. The influence of roller speed on molten pool characteristics, cooling-roller heat transfer, and ribbon thickness was analyzed. The effect of ribbon thickness on the total loss and permeability of the magnetic cores was investigated. The results indicate that the molten pool size decreased as the roller speed increased. At t = 5 ms, the maximum heat-transfer coefficient of the roller surface increased from 2.09 × 10⁶ W·m⁻²·K⁻¹ at 15 m/s to 2.6 × 10⁶ W·m⁻²·K⁻¹ at 24 m/s. The ribbon thickness decreased from 39.96 μm to 20.02 μm (a 49.9% reduction) as the roller speed increased from 18 m/s to 30 m/s. The total loss of the nanocrystalline magnetic cores increased with ribbon thickness, whereas their permeability increased as ribbon thickness decreased. At 100 kHz, the nanocrystalline magnetic core made of 10–12 μm ribbons exhibited a high permeability of 59,507. Full article

The study is based on Land Surface Temperature (LST) and Air Temperature data and Nonparametric Data Envelopment Analysis (DEA) technique to evaluate heat efficiency and detect anomalies in the thermal regime in the Eastern Black Sea Region, particularly in Hopa and Artvin, during the period 2000–2024. The regulating role of the Black Sea has resulted in Hopa having the warmest and most stable temperature patterns, with daytime temperatures 1.8 to 3.7 °C higher than Artvin. Previous DEA analysis of daytime temperatures has shown that the 2018–2020 period had the highest daily temperatures, while the 2001–2010 decade was characterized by the highest nighttime temperatures. A future heat map based on Monte Carlo simulation using six climate change scenarios indicates that in the most optimistic case, assuming a temperature increase of +0.8 °C, efficiency scores could increase as high as 0.995. On the other hand, if global warming leads to a sudden temperature increase above +7.2 °C, there is a 21.7% climate efficiency loss. Sensitivity analysis showed that technological innovation and good governance are the main positive factors affecting climate efficiency. Random Forest (RF) and SHapley Additive Explanations (SHAP) analyses were applied to determine the impact of climate factors on DEA scores and also indicated areas requiring risk assessment. The findings highlight the importance of considering location-specific climate adaptation strategies. Based on the observed thermal contrasts between coastal and inland environments, potential adaptation considerations may include urban heat management and agricultural water stress in coastal areas such as Hopa, and cold-climate resilience and energy-efficient infrastructure in inland locations such as Artvin. Full article

Anaerobic digesters operating under neotropical conditions face significant technological constraints. High humidity, intense solar radiation, and pronounced diurnal temperature variations increase conductive, convective, and radiative heat losses. These factors reduce internal thermal stability and directly affect methane production rates and overall energy efficiency. As a result, thermal instability becomes a recurrent operational bottleneck in biogas plants without active temperature control. This review examines the thermal and dynamic behavior of anaerobic reactors from a process-engineering perspective. It integrates energy balances, heat-transfer mechanisms, and computational fluid dynamics (CFD) modeling. The combined effects of temperature gradients, hydrodynamic mixing patterns, and structural material properties are analyzed to determine their influence on thermal homogeneity, microbial stability, and methane yield consistency under mesophilic conditions. Technological strategies to mitigate thermal losses are evaluated. These include passive insulation using low-conductivity materials, geometry optimization supported by numerical modeling, and thermal recirculation schemes, as these factors govern temperature distribution and process resilience. Current limitations are also discussed, particularly the frequent decoupling between ADM1-based kinetic models and transient heat-transfer analysis. This separation restricts predictive capability under real-scale diurnal temperature oscillations. The development and validation of coupled hydrodynamic–thermal–biokinetic models under fluctuating neotropical boundary conditions are proposed as critical steps. Such integrated approaches can enhance operational stability, ensure consistent methane production, and improve energy self-sufficiency in organic waste valorization systems. Full article

A warm-up is a critical procedure in sports science for enhancing muscular performance and optimizing subsequent athletic activities. However, the physiological and athletic performance effects of a warm-up are often transient, diminishing rapidly during the period of inactivity after the warm-up, which is known as the warm-up transition phase. In this study, a multi-functional thermoregulation wearable composite film of graphene–MXene–bacterial cellulose/polyethylene glycol (G-M-BC/PEG) was developed by integrating MXene (a two-dimensional material with good photothermal conversion performance) and graphene into a bacterial cellulose aerogel framework, subsequently impregnated with polyethylene glycol (PEG-2000). The film showed stable structure, efficient solar photothermal conversion and storage (SPCS), and improved mechanical properties. Under 1 sun irradiation, the optimized G-M-BC/PEG wearable film showed excellent SPCS performance, sustaining a temperature plateau of 38–40 °C for 10 min after the xenon lamp was switched off under 1 sun irradiation, with a leakage rate of only 5.32% after five cycles. By constructing a biomimetic sports human body model, the composite aerogel was shown to significantly elevate muscle surface temperature and effectively mitigate heat loss during the transition phase. In the warm-up effectiveness and sports performance tests, the wearable film improved 200 m sprint performance by 0.8% ± 0.4% (p = 0.039). It also maintained subjective thermal sensation during the warm-up transition phase, with no significant decline at 5 or 10 min after the warm-up and a significant decrease only at 15 min (p = 0.02), while thermal comfort remained stable, suggesting improved neuromuscular readiness. This research provided a novel strategy for the fabrication of advanced aerogel-based wearable devices aimed at precision thermal management and athletic performance optimization. Full article

Background: Recent research has highlighted the potential of postbiotics for addressing obesity and associated metabolic disorders. In this randomized, double-blind clinical trial, the efficacy of a postbiotic product in managing overweight and associated parameters was assessed. Methods: Sixty individuals were randomized into two groups: one group (n = 30) received the Postbiotic (heat-killed L. fermentum strain K8-Lb1) and the other (n = 30) a Placebo control. Body weight, waist circumference, body composition, vital signs, blood biomarkers and questionnaires for quality of life, eating behavior, eating control and gastrointestinal symptoms were assessed. Results: After a 12-week intervention, body fat mass (primary parameter) was significantly (p = 0.016) reduced in the Postbiotic group (98.15 ± 3.32% of baseline) compared to the Placebo group (100.41 ± 3.39%). In line with this, body weight (p = 0.047) and waist circumference (p = 0.034) were significantly reduced and visceral fat tended to be reduced (p = 0.053). Accordingly, the Postbiotic group tended (p = 0.066) to feel more in control of their body weight. Despite weight loss, muscle mass tended (p = 0.062) to increase. ALT, AST and GGT tended to be reduced, which may indicate an improvement in liver steatosis. Estimated average glucose (eAG) differed significantly between the groups in individuals with normal fasting glucose levels. The ability to concentrate significantly (p = 0.014) improved. Conclusions: Under an ad libitum diet, the postbiotic L. fermentum strain K8-Lb1 reduced body fat mass, body weight, and waist circumference, improved the ability to concentrate, and showed a trend towards an increase in muscle mass. The results of this pilot trial need confirmation by a pivotal trial. Full article

Indoor swimming pools require ventilation and precise temperature and humidity control, leading to significant energy consumption. This study investigated the use of liquid desiccant technology to reduce energy consumption for heating and dehumidification of two indoor swimming pools in a UK leisure centre. Through dynamic modelling and techno-economic analysis, this research quantified heat losses in the pools, simulated the performance of liquid desiccant technology, evaluated the economic benefits and cost implications of regenerating the desiccant solution using waste heat, and assessed the feasibility of adopting the technology across the entire UK. The results showed that evaporative losses were the dominant heat loss mechanism for both pools, while the proposed liquid desiccant system effectively maintained optimal temperature and humidity conditions. Additionally, pool water can serve as a heat sink after desiccant regeneration, thereby reducing the energy demand for pool water heating. Energy consumption could be reduced by 68.9–76.7% when using a cooling tower and 77.5–88.1% when using pool water for heat rejection, with internal rates of return that can exceed 15% for the most cost-effective configurations. If the regeneration heat is sourced externally, up to £34.7/MWh could be paid for the heat required while ensuring the cost-effectiveness of the process. These findings suggest that liquid desiccant systems can reduce heating and dehumidification energy in indoor swimming pools when low-temperature heat is available for regeneration. Future research should focus on experimental validation, addressing interactions with chlorine gases, long-term system performance and real-world implementation challenges to ensure commercial deployment. Full article

Historic buildings often exhibit high energy use intensity (EUI), while conservation constraints limit envelope retrofits, making it difficult to identify robust and actionable operational predictors. Using four in-use historic buildings in Shenyang, China, this study presents a pilot methodological demonstration with a controlled-comparability workflow consisting of two linked layers: (i) a Driver layer of intervenable operational variables and (ii) a Pathway layer of calibrated EnergyPlus heat-balance terms for physics-informed interpretation. Three importance approaches (Spearman, wrapper RFE with XGBoost, and Random Forest) are compared; rankings are fused via reciprocal rank fusion, and stability is tested using cross-period rolling validation across Top-K feature sets. After similarity screening, EUI variation is better explained by operational predictors and the corresponding simulated loss channels than by macro-scale structural heterogeneity. Infiltration-related indicators and envelope/infiltration loss components remain consistently prominent, while Spearman importance is less stable in the Pathway layer under seasonal switching and nonlinear coupling. A Top-10 subset provides a favorable accuracy–stability trade-off. The proposed Driver–Pathway mapping supports conservation-compatible prioritization hypotheses within a simulation-consistent interpretive framework; findings are associational and context dependent and should be validated through field measurements and experimental or quasi-experimental studies before prescriptive claims are made. Full article

Acute heat stress frequently causes mass mortality in farmed red swamp crayfish (Procambarus clarkii), yet the mechanisms underlying immune collapse remain poorly understood. We established an acute heat stress model (37 °C, 6 h) and performed an integrative analysis combining hemocyte profiling, redox and immune assays, RNA-seq, and qRT-PCR. Heat stress significantly increased mortality and disrupted the hemocyte system, with a ~25% reduction in total hemocyte count and a selective decline in granular cells. This was associated with severe redox imbalance, evidenced by ROS/H₂O₂ accumulation, suppressed SOD and CAT activities, and lipid peroxidation damage. Transcriptomic analysis revealed 1446 differentially expressed genes, indicating concurrent activation of ER stress and autophagy alongside suppression of energy metabolism. Key gene validation confirmed upregulation of pro-apoptotic factors (CASP3, P53) and ER stress markers (GRP78, XBP1), consistent with hemocyte depletion. These findings provide multi-level evidence that acute heat stress triggers a redox crisis (“oxidative burst–defense suppression”), which in turn activates ER stress and apoptosis, leading to selective loss of granular cells and systemic immune compromise. This study establishes a mechanistic framework for understanding heat-induced mortality in crustaceans and offers a theoretical basis for developing targeted interventions to enhance thermal resilience in crayfish aquaculture. Full article