Search Results (22,851)

A computational fluid dynamics and conjugate heat transfer (CFD + CHT) methodology is developed for the thermal simulation of a commercial prismatic LiFePO${}_4$ cell under charging and discharging operating conditions. The approach couples a three-dimensional representation of the battery, including a simplified description of its internal layered structure, with an electrochemical–thermal heat-generation model implemented as a temperature- and time-dependent volumetric source term. The heat source is applied within the active layers of the cell and updated during the transient simulation according to the local thermal state and to the evolution of the state of charge. The methodology is applied to 1C and 2C cycles under natural convection and forced-air cooling at free-stream velocities of $10\mathrm{m}{\mathrm{s}}^{-1}$ and $20\mathrm{m}{\mathrm{s}}^{-1}$. A dedicated wind-tunnel campaign is carried out on the same cell, instrumented with type-K thermocouples distributed over its external surfaces, to provide experimental data for model validation. The results show that the proposed framework accurately reproduces the main wall-temperature trends observed experimentally. Under natural convection, the temperature distribution remains nearly uniform, whereas forced convection produces more pronounced vertical and in-plane gradients. For the charge cycles, the comparison between CFD predictions and end-of-cycle measurements yields a mean absolute error (MAE) of $0.66{}^{\circ }\mathrm{C}$ and a root-mean-square error (RMSE) of $0.82{}^{\circ }\mathrm{C}$ over 168 measurement locations. The discharge cycles yield a comparable level of agreement (MAE $0.65{}^{\circ }\mathrm{C}$, RMSE $0.81{}^{\circ }\mathrm{C}$ over 168 probe points), confirming the predictive capability of the methodology for both operating modes. Full article

Copper selenide compounds, owing to their excellent electrical transport properties and low thermal conductivity, are promising thermoelectric materials, but their poor mechanical flexibility limits practical applications in flexible devices. Herein, a simple all-electrochemical strategy was developed to fabricate polypyrrole (PPy)/Cu_2−xSe composite thermoelectric films through sequential electropolymerization of pyrrole and electrodeposition of Cu_2−xSe. By optimizing the deposition potential of Cu_2−xSe and pyrrole polymerization time, the thermoelectric performance of the composite films was significantly enhanced. The optimized PPy/Cu_2−xSe composite film achieved a maximum power factor of 174.05 ± 9.87 μW m⁻¹ K⁻², nearly 300 times higher than that of pristine PPy, while maintaining a low thermal conductivity of 0.30 W m⁻¹ K⁻¹. The composite film also exhibited excellent flexibility, retaining 94.77% of its initial power factor after 1000 bending cycles. A flexible thermoelectric device assembled from the composite films delivered a maximum output power of 240.5 nW at ΔT = 50 K. This work provides an effective strategy for developing Cu_2−xSe-based flexible thermoelectric composites. Full article

This paper presents an experimental investigation into the flow characteristics and volumetric efficiency (η_vol) of a fixed-displacement external gear pump (GHD 17R) operating under coupled hydraulic parameters using an eco-friendly synthetic ester-based hydraulic fluid (48 mm²·s⁻¹ at 40 °C). Measurements were performed on a laboratory single-circuit hydraulic test rig across a rotational speed range of 500–2500 min⁻¹, operating pressure range of 2–10 MPa, and fluid temperature range of 30–60 °C. To eliminate flow fluctuations caused by structural vibrations at 1250 and 1750 min⁻¹, a 15% trimmed mean statistical filter was successfully implemented. A comparative sensitivity analysis—evaluating absolute, normalized, and relative significance—was developed and compared against a three-way analysis of variance (ANOVA) effect size model (η² and partial η²). The relative sensitivity approach identified rotational speed as the dominant parameter for direct hydraulic flow, accounting for 95.80% of total variation. Conversely, when evaluating volumetric efficiency, the proportional impact of speed was removed, revealing a balanced distribution of internal losses: rotational speed contributed 54.73%, fluid temperature 26.08%, and pressure 19.19%. The three-way ANOVA confirmed that all primary parameters and their cross-interactions had a statistically significant effect (p < 0.05). The findings scientifically demonstrate that temperature-induced viscosity collapse exhibits a stronger relative dynamic sensitivity on volumetric losses than pressure fluctuations within standard operating envelopes. The constructed multi-dimensional flow and efficiency maps provide practical input for advanced diagnostic tools, real-time thermal condition monitoring, predictive maintenance, and energy-optimized control schemes in modern fluid power systems using eco-friendly lubricants. Full article

This paper presents the development of a multi-domain simulation for the Porsche Taycan’s all-wheel-drive (AWD) electric propulsion system to investigate the impact of the rear drive unit’s two-speed transmission on performance and drive quality during maximum acceleration. This study was undertaken independent of the vehicle and propulsion system OEM. A lumped-parameter model of the front and rear electric drive units (EDU) and the high-voltage battery was developed and calibrated against the published data for key benchmarks, including 0–100 kph acceleration times and peak longitudinal acceleration. The mechanical shifting mechanism was reverse-engineered to simulate high-performance shift trajectories. To manage the transition, a clutch control scheme integrates a reduced-order clutch-to-clutch model featuring a feedforward (FF) torque estimator and a closed-loop feedback (FB) controller to achieve target input shaft speeds and shift durations. The study concludes with a comprehensive analysis of the propulsion system’s behavior at a battery state of charge of 96% and 25% and three electric motor speeds at which the upshift is commanded. The simulation results demonstrate that executing an early upshift at 10,700 rpm with 96% of SOC yields a 0.100-s inertia phase shift time, restricts the clutch thermal dissipation to 21 kJ, and achieves an 8-s velocity of 203.4 kph, outperforming the upshift at 15,300 rpm (0.210 s, 34 kJ, and 202.8 kph). Furthermore, the transient regenerative braking on the rear axle during the inertia phase reduces the peak current draw from 675 A to 87 A, recovering the DC bus voltage to enable cross-axle torque boosting on the front axle. Full article

Cellulose acetate (CA) is a promising bio-derived membrane material for water treatment; however, its limited availability of active functional sites can restrict its affinity toward dissolved pollutants. In this study, a cellulose acetate membrane was fabricated by phase inversion and subsequently functionalized through novel direct graft copolymerization with bio-based itaconic acid (IA) using potassium persulfate (KPS) as an initiator in an aqueous medium. The grafting approach introduced carboxylic functional groups into the CA matrix, providing additional active sites for pollutant removal. The successful grafting was confirmed by UV–Vis and 1H NMR spectroscopy, while XRD indicated changes in the structural organization of the polymer matrix. SEM/EDS characterization further revealed morphological changes associated with grafting, and cross-sectional SEM showed the development of finger-like, continuous pore channels within the modified membrane. The effects of reaction time, IA concentration, and KPS concentration on the grafting percentage were systematically evaluated, with grafting increasing up to an optimum range before declining at excessive monomer or initiator concentrations. Thermal analysis demonstrated improved stability after grafting, with the 6.6% grafted CA-g-IA membrane exhibiting an initial decomposition temperature of 351 °C and a reduced weight loss of 85% at 500 °C, compared with 344 °C and 91%, respectively, for pristine CA. The 6.6% CA-g-IA membrane was subsequently evaluated for the removal of Cu(II) and methylene blue (MB) from aqueous solutions. Cu(II) uptake was strongly influenced by contact time, solution pH, initial concentration, and grafting percentage, with the highest performance observed around pH 6 and 240 min contact time. The membrane also maintained its Cu(II)-binding performance over four regeneration cycles following HNO₃ treatment. Overall, direct IA grafting provides a simple bio-based functionalization strategy for enhancing the pollutant-binding functionality of cellulose acetate membranes, demonstrating potential for the removal of metal ions and cationic dyes from contaminated water. Full article

Given that large-scale storage and transportation of liquid hydrogen are key to realizing the hydrogen economy, tank containers have attracted much attention for their flexibility. To minimize evaporation losses, efficient support structures are essential for these liquid hydrogen tank containers. Herein, a carbon fiber-reinforced polymer (CFRP) suspension ring is developed to support the inner vessel of liquid hydrogen tank containers. By using a special resin matrix and optimizing its curing process, the suspension ring capitalizes on a small cross-sectional area and low thermal conductivity, thereby significantly mitigating the cold-bridge heat transferred from the outer vessel to the inner vessel. Experimental results demonstrate that the tensile strength, outgassing rate, and fatigue performance of the suspension ring at both 77 K (liquid nitrogen temperature) and 4 K (liquid helium temperature) can meet the design targets. Notably, its equivalent thermal conductivity was approximately 88% lower than that of a stainless steel structure of the same size. With the integration of this suspension ring into a 40 ft liquid hydrogen tank container, the daily liquid nitrogen evaporation rate was recorded below 0.082%/d. Furthermore, the holding time before the pressure reached 0.14 MPa exceeded 192 h with a 90% liquid hydrogen filling ratio. This work provides key technical support for high thermal insulation, long-endurance liquid hydrogen storage and transportation equipment. Full article

Non-uniform discharge temperature during sinter cooling is a practical issue in ironmaking, as local overheating may increase the thermal load on downstream conveying equipment. To mitigate insufficient cooling in the upper sinter bed under the conventional bottom-blowing mode, this study developed a three-dimensional transient CFD model for an industrial continuous annular cooler and optimized the air-supply strategy in Zones IV and V. Under the conventional condition, ambient air is supplied independently to Zones IV and V from the bottom wind boxes. In the novel air-supply strategy, while keeping the total fresh cooling-air flow rate in the final cooling region unchanged, ambient air is introduced from the upper side of Zone V and discharged from its bottom; the outlet gas from Zone V is then supplied to the bottom of Zone IV, forming a serial air-supply path. The results show that the novel arrangement improves the spatial matching between the cooling gas and the sinter bed during final cooling and suppresses the local high-temperature region near the discharge end. The maximum discharge temperature decreases from 459 K to 410 K, below the process limit of 423 K, while the average discharge temperature decreases from 377 K to 364 K. Based on the enthalpy-flow difference calculation, the predicted recoverable waste heat also increases under the novel condition. These findings suggest that redesigning the gas-flow route in the final cooling region can effectively enhance the uniformity of the discharge temperature in industrial annular coolers. Full article

With the rapid transition of the global energy structure, large-scale clean energy integration has become a major trend in power system development. Nevertheless, the intermittency and stochastic fluctuation of renewable power generation threaten the secure operation of power systems. With high power density and millisecond-level response capability, supercapacitors act as key technical support for frequency stabilization and grid frequency fluctuation suppression. This paper reviews research advances in the application of supercapacitors to power system frequency regulation. It presents the classification and energy storage mechanisms of supercapacitors, analyzes their technical advantages in frequency regulation, and summarizes key research progress involving control strategies, topologies and capacity optimization schemes. Three typical application scenarios are illustrated: standalone frequency regulation, coordinated thermal-storage frequency regulation, and auxiliary frequency regulation for renewable power plants. Considering future requirements for frequency regulation, potential research directions are put forward to provide references for follow-up related studies. Full article

Drying is widely used to stabilize foods, but long processing times and thermal exposure increase energy demand and can impair color, texture, nutrients, and flavor. Cold plasma (CP) pretreatment has attracted interest as a nonthermal strategy for accelerating moisture removal while maintaining product quality. This critical review examines CP pretreatment-assisted drying across food materials by linking structural remodeling with redox regulation and metabolic responses. Current evidence shows that changes in surface wettability, cuticular barriers, cell-wall and membrane integrity, and pore connectivity can facilitate water migration and shorten drying. CP-associated modulation of browning enzymes, oxidative status, and bioactive or flavor-related metabolites may also influence color, antioxidant capacity, nutrient retention, and flavor. However, these effects vary with discharge mode, treatment intensity, gas composition, pressure, temperature, and food-matrix properties. Excessive exposure can instead aggravate oxidation and diminish product quality. Current mechanistic evidence is strongest for plant foods and edible fungi and remains limited for animal-source foods. Together, these findings link plasma-generated chemical and physical agents to structural, biochemical, and drying responses. They provide a basis for defining material-specific operating windows and developing reproducible, safe, and scalable CP pretreatment-assisted drying of foods. Full article

Urban Building Energy Modeling (UBEM) offers a scalable, physics-based method to simulate energy demand at the district level, enabling data-driven district energy demand planning and optimization. However, translating UBEM into a reliable, openly replicable workflow remains a significant methodological gap. In particular, limited attention has been devoted to the development of transparent and transferable UBEM workflows capable of systematically quantifying the impact of modeling assumptions on district-scale thermal demand accuracy. This paper presents and validates a five-step UBEM pipeline integrating freely available geospatial data from OpenStreetMap (OSM), archetype-based building characterization, multi-scenario EnergyPlus simulation via the Urban Modeling Interface (UMI) within a structured validation framework. To improve interpretability and reproducibility, a dedicated three-scenario simulation protocol was developed to isolate and quantify the influence of geometry simplifications, archetype assumptions, and weather data fidelity on model accuracy. The workflow is demonstrated through application to a real district heating system (DHS) in northern Italy, encompassing UBEM results validated against monitored consumption data at different temporal resolutions. The refined model achieves a district-scale annual magnitude error of 1.30% between real and simulated data. Persistent limitations in domestic hot water representation and peak load estimation are identified as priorities for future development. Full article

To address the critical role of armature–rail contact in electromagnetic railguns, a comprehensive electromagnetic–thermal–mechanical coupled model is developed. In contrast to existing coupled railgun models, this work uniquely introduces the dynamic mechanical contact state and contact resistance as coupling variables and explicitly accounts for the interference−fit process during armature loading, enabling a full−cycle simulation from assembly to launch. The simulation results are compared with open−bore experimental measurements, and the model is applied to simulate the launch process. The results reveal a characteristic evolution of contact resistance: a rapid initial decrease followed by a gradual increase, maintaining relatively stable conditions until muzzle exit. Mechanistically, the early−stage decrease is attributed to transverse Lorentz forces that enlarge the contact area, while the later−stage stability is governed by thermal expansion, preserving contact pressure. Parametric studies further elucidate the influence of operating conditions on contact resistance. Full article

Amid the low-carbon transition, university teaching buildings feature high occupancy and energy use, making the synergistic enhancement of their daylighting and thermal environments crucial for “dual carbon” goals. However, traditional “north–south homogenization” designs in cold regions fail to address the spatial heterogeneity of solar radiation and climate resources, intensifying the trade-off between natural daylighting and Heating Energy Use Intensity (E_h) while restricting space performance optimization. Focusing on a typical cold-region teaching building, this study proposes a “parametric modeling–multi-objective optimization–machine learning” integrated framework. Targeting spatial daylight autonomy (sDA), useful daylight illuminance (UDI), and E_h, we compared the homogeneous baseline model with the Pareto-optimal solution set, demarcated key design parameter boundaries, and developed an ensemble-based rapid prediction model. Based on the parametric simulation analysis of this representative case building in a cold region, results indicate that: (1) Compared to the baseline, the overall optimal scheme reduced E_h by 17.43% while increasing UDI and sDA by 12.0% and 10.5%, respectively. (2) The Pareto set strictly converges toward a due-south orientation and a “deep-south, shallow-north” layout (depth ratio: 0.66–0.77); thermal configurations exhibit “enhanced northern insulation and southern heat gain,” confirming heterogeneous design matches cold climates better. (3) The four constructed machine learning models (MLP, LightGBM, XGBoost, and Random Forest) uniformly achieved test recall rates exceeding 99%, enabling highly precise, rapid classification of top-performing design scenarios during early-stage design. This study overcomes climate-matching blindness in traditional design, providing a multi-objective synergistic optimization path balancing low energy and high-quality daylighting with substantial engineering and theoretical value. Full article

Based on on-site surveys of rural dwellings in the Qianbei Region, this study addresses the persistent challenge of high energy consumption, poor thermal comfort, and economic constraints. A regionally adaptive design methodology integrating parametric modeling, global sensitivity analysis (GSA), and multi-objective optimization was developed. Using Rhino–Grasshopper, a parametric model with 24 variables was constructed. The Sobol GSA method identified the most influential variables by quantifying both individual and interaction effects. Optimization objectives were annual energy consumption (E), thermal discomfort time (TDT), and life-cycle cost per unit area (LCC_unit). Multi-objective optimization using the NSGA-II algorithm shows that the high-performance scenario—150 mm XPS insulation combined with Low-E windows—reduces energy consumption by 52.4% and thermal discomfort hours by 55.4%. The cost-effective scenario, based on an 80 m² miniaturized design, lowers LCC_unit to ¥248,000. The optimal synergistic paradigm integrates a southwest orientation (210°) with XPS insulation and Low-E windows, providing a standardized and replicable approach for rural dwelling construction and retrofit in similar climatic regions. Full article

The global plastic pollution crisis demands a fundamental re-evaluation of materials systems beyond incremental improvements to fossil fuel-based polymers. Bioplastics, polymers derived from renewable biological feedstocks, biodegradable under defined conditions, or both, offer a chemically diverse and rapidly evolving platform for transitioning toward circular materials economies in which the value of carbon, energy, and material is retained across multiple use cycles. This review provides a comprehensive and critically organized account of the bioplastics field, spanning three generations of feedstock development from food crops through lignocellulosic residues to algae and waste streams; primary production pathways including microbial fermentation, ring-opening polymerization, and biosynthesis; forming processes from extrusion and injection molding to additive manufacturing; and the mechanical, thermal, and barrier properties that determine application fitness. Particular emphasis is placed on life cycle assessment, which reveals that bioplastics’ climate benefits are conditional on feedstock choice, land-use management, energy source at manufacturing, and end-of-life pathway, and that burden-shifting from greenhouse gas emissions to land use, water consumption, and eutrophication is a systematic risk requiring integrated LCA evaluation rather than single-metric optimization. The review further examines end-of-life recycling, composting, and biodegradation pathways; market applications across packaging, agriculture, automotive, biomedical, and electronics sectors; and the growing role of artificial intelligence and machine learning in accelerating materials design, process optimization, and lifecycle data management. Critical barriers to scale, such as cost premiums of 20–75% over conventional plastics, inadequate composting infrastructure, recycling stream contamination, regulatory fragmentation, and consumer labeling confusion, are systematically analyzed alongside mitigation strategies. The review concludes with a forward-looking discussion of emerging feedstocks, smart and functional bioplastics, and the policy and infrastructure investments required to translate the environmental promise of bio-based polymers into realized circular economy impact. Full article

Unmanned aerial vehicles (UAVs) used in low-altitude mobility and electric aviation are increasingly required to carry higher payloads, operate for longer durations and maintain reliable performance under constrained installation conditions. In compact power cabins, batteries, controllers, power distribution units and auxiliary actuators are densely arranged, making cabin thermal management a critical design issue. In this study, a full-scale conjugate flow and heat transfer model is developed for the power cabin of a UAV and validated against thermal management experiments. The validated model is then used to examine how a conventional rectangular ram-air inlet and a proposed stepped ram-air inlet affect air capture, internal flow organization and temperature distribution. The inlet area of the rectangular configuration is first varied to establish a baseline, after which the transition arc ratio, spacing ratio and area ratio of the stepped inlet are parametrically investigated. The results show that increasing the rectangular inlet area from 0.002 to 0.008 m² increases the total captured mass flow rate from 0.258 to 1.084 kg/s, whereas the cabin average temperature decreases by 0.34 °C. By contrast, the cabin maximum temperature decreases nonlinearly, with a 27.2% reduction when the area increases from 0.004 to 0.006 m². These results indicate that air capture and the cabin average temperature alone are insufficient to evaluate cooling effectiveness in a compact multi-source cabin. For the stepped inlet, the transition arc ratio controls the turning of the incoming flow, the spacing ratio governs shielding and backflow between adjacent inlet sections, and the area ratio redistributes the dominant inlet sections. The best-performing stepped-inlet configuration among the tested cases increases the captured mass flow rate by 32.8% compared with the rectangular baseline under the same opening constraint and improves the utilization of cooling air around high heat load components. This study demonstrates that ram-air inlet design for UAV power cabins should be treated as a coupled problem of the mass flow capture, internal flow path and component-level thermal response. Full article