Search Results (513)

Modern power grids face increasing stress from volatile, high-dynamics loads, such as Electric Vehicle (EV) charging clusters and intermittent renewable energy sources. Accurate transformer thermal monitoring via the International Electrotechnical Commission (IEC) 60076-7 and the Institute of Electrical and Electronics Engineers (IEEE) C57.91 standards is crucial, yet their methodologies differ significantly. This study develops a comprehensive MATLAB simulation framework to quantify these differences. The analysis compares physical thermal models across multi-stage cooling—Oil Natural Air Natural (ONAN), Oil Natural Air Forced (ONAF), and Oil Forced Air Forced (OFAF)—and insulation aging models. It is demonstrated that divergence in transformer life estimation stems primarily from the physical thermal models. A ‘reversal of conservatism’ is identified, where ‘conservative’ is defined as predicting higher hot-spot temperatures and enforcing a larger safety margin. Results prove that while the IEC model is thermally more conservative during cooling failures (static mode), the IEEE model is consistently more conservative during normal active cooling. Additionally, 2D “heat maps” are presented to define safe operational zones, and the catastrophic impact of cooling system failures is quantified. These findings provide a quantitative outline for managing transformer state under increasingly demanding loading schemes. Full article

In this study, the design and optimization of some parameters thought to be effective in the convective heat transfer caused by an air jet impinging on a rotating heated cylindrical surface are investigated by using the Taguchi optimization method. The temperature distribution on the rotating cylindrical surface resulting from air jet impingement is measured with an infrared thermal camera, and the heat transfer due to the difference between the air jet temperature and the surface temperature is shown by Nusselt number. The effects of some major parameters such as the Reynolds number of the air jet, jet-to-surface distance, speed of the rotating cylinder, geometry of the nozzle, and constant surface temperature on Nusselt number are evaluated by means of Analysis of Variance (ANOVA). As a result, the Reynolds number, surface temperature, and rotational speed are found to play key roles in enhancing heat transfer under the tested conditions. The results provide valuable insight for thermal management applications such as gas turbines, brake disks, and electronic cooling, and the adopted Taguchi-based approach may serve as a systematic framework for future studies involving nanofluids and multi-jet systems. Full article

To meet the requirement of thermal management of modern electronic devices, polymer composites with high thermal conductivity (TC) and dielectric performance are nowadays in urgent demand. Herein, a highly ordered continuous network of boron nitride nano-sheet (BNNS) was constructed in cyclic olefin polymer (COP) films via the forced flow processing in the rubbery state (FFRS), melt-spinning, fiber-alignment, and hot-pressing procedures. The composites exhibited superior TC, low dielectric permittivity, and low dielectric loss simultaneously. The in-plane TC of the composites reached 3.92 W/(mK) when the content of BNNS was at 27 weight percentage (27 wt%), since the procedures improved the face-to-face contact between the BNNS (which was exfoliated, dispersed, and in-plane oriented during FFRS), enhancing the continuity of the BNNS thermally conductive network. Both the TC and the experimental results indicated the outstanding heat dissipation performance of the composites. Meanwhile, the dielectric permittivity and dielectric loss of the 27 wt% BNNS composites were 2.56 and 0.00085 at 10 GHz, respectively, lower than that of the COP-POE matrix. Moreover, the mechanical properties, water vapor permeability, and coefficient of thermal expansion of the composites were excellent. The composites with such highly ordered continuous networks are very promising in high-performance electronic devices. Full article

The anisotropic jelly roll structure of cylindrical Li-ion batteries leads to highly directional heat generation, causing severe radial heat accumulation and creating a critical demand for precise thermal management. Conventional anisotropic phase change materials (PCMs), often reliant on single-dimensional conductive skeletons, exhibit limited enhancement in thermal conductivity anisotropy. This study proposes a novel strategy utilizing a hybrid carbon aerogel composed of one-dimensional carbon nanotubes (CNTs) and three-dimensional expanded graphite (EG) to construct highly aligned thermal conduction pathways within a flexible PCM. A three-step experimental method was employed to successfully fabricate a composite PCM with highly anisotropic thermal conductivity. A case study confirmed that, compared to a sole 3D skeleton, the hybrid 1D/3D aerogel significantly improves the alignment of the microstructure. At an optimal hybrid aerogel content of 8 wt.%, the composite achieved a 5.0% increase in radial thermal conductivity and a remarkable 16.7% increase in axial thermal conductivity, indicating a significantly optimized anisotropy ratio. When applied to a cylindrical battery thermal-management case, this material enables directed heat dissipation, effectively lowering the maximum battery-surface temperature by 13.1 °C. This work provides a scalable approach for designing high-performance anisotropic flexible PCMs tailored for advanced thermal management in high-power-density Li-ion batteries and other compact electronics. Full article

This paper presents an innovative solution based on the Indirect Regenerative Evaporative Cooling (IREC) concept for high-power density electronics. The technology relies on forced convective cooling by air that is additionally cooled via evaporation. The system comprises dry and wet channels for the cooled and wet air, respectively; water is delivered through porous membranes in the wet channels. The novelty relative to HVAC-type exchangers (based on IREC technology) is a full flow return configuration, in which the entire stream from the dry channels is redirected into the wet channels. The performance benefits become pronounced at high ambient temperatures, where traditional forced convection may be insufficient; inlet air absolute humidity is a key factor governing efficiency. The authors present a developed prototype, a simplified thermal analysis, measurement results, and a discussion of IREC applicability to electronics cooling. The results indicate feasibility and highlight the potential of the proposed design for the energy-efficient thermal management of sensitive electronic equipment. Full article

Background/Objectives: An observed increase in fungal infection incidence over the past two decades underscores the limitations of conventional topical treatments for deep infections, primarily due to the skin’s stratum corneum barrier. This has driven the development of advanced topical preparations. This study evaluated the encapsulation of oxiconazole utilizing novasomes to enhance its topical delivery. Methods: Oxiconazole-loaded novasomes were synthesized by the ethanol injection technique and subsequently characterized using key physicochemical parameters, including encapsulation efficiency (EE%), vesicle size (VS), zeta potential (ZP), polydispersity index (PDI), and percentage drug release (DR%). The optimized formulation underwent comprehensive evaluation employing Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Moreover, its activity was evaluated through in vitro penetration studies and in vivo assessments. Results: R9 was identified as the optimal candidate, demonstrating an encapsulation efficiency of 94.63 ± 1.60%, a vesicle size of 174 ± 1.15 nm, a zeta potential of −46.5 ± 1.61 mV, a polydispersity index of 0.184 ± 0.01, and a drug release rate of 51 ± 0.50% within 8 h. This optimal formula achieved 94 ± 1.75% permeation of oxiconazole within 24 h. FTIR examination affirmed the interaction of oxiconazole and the excipients, while DSC analysis verified the thermal durability of oxiconazole. In vivo histopathological examination demonstrated the superior efficacy of the optimal formula in treating Candida albicans infection. Conclusions: Novasomes emerge as a promising and efficacious system for oxiconazole encapsulation, holding significant potential for the effective and prolonged management of topical fungal infections. Full article

The increasing power density of Unmanned Aerial Vehicles (UAVs) has intensified the need for the efficient thermal management of their propulsion and electronic subsystems. This paper presents a systematic multi-fidelity methodology for the design and validation of a ducted forced convection cooling system for a Class-I mini-UAV. The approach combines analytical sizing and computational fluid dynamic (CFD) analyses. In the preliminary design phase, a surrogate-based optimization (SBO) framework was implemented to determine the optimal geometric characteristics of a NACA-type inlet duct, enabling the efficient exploration of the design space using a limited number of CFD simulations. SBO employed a Kriging surrogate model trained on a Design of Experiments (DoE) dataset to capture nonlinear interactions between duct geometry and performance metrics such as pressure recovery, total-pressure loss, and outlet flow uniformity. The optimized configuration was then refined and validated through detailed external and internal CFD studies under representative flight conditions. The optimized NACA duct configuration achieved an average increase of 10.5% in volume flow rate (VFR) and a 9.5% reduction in velocity distortion while maintaining a drag penalty below 1% compared to the benchmark Frick’s NACA duct. The presented methodology demonstrates that the early integration of surrogate-based optimization in UAV inlet design can significantly improve aerodynamic and thermal performance. Full article

Ensuring efficient heat transfer to maintain optimal system performance is crucial in modern electronics owing to the rise of artificial intelligence. In the last few decades, scholars have explored various strategies for enhancing electronic device thermal management, focusing on the effects of fin shape, dimension, and spacing on heat transfer efficiency. Recent advancements in additive manufacturing have enabled fabrication of complex geometries, such as triply periodic minimal surfaces (TPMSs), which represent promising alternatives to conventional designs. This study presents a comparative analysis of the thermal performance and fluid flow characteristics of two foam TPMS-based (gyroid and primitive) heat sinks with wavy fins made using aluminum foam. COMSOL Multiphysics version 5.1, employed along with the implemented finite element method, was used to simulate convective heat transfer, pressure drop, the Nusselt number, and thermal performance at different fluid velocities along the length of a channel. The foam structure was heated by a copper plate, and the Nusselt number was evaluated over porosity levels from 0.1 to 0.9. A porosity between 0.5 and 0.7 offers the best balance of cooling performance and pumping power. Foam TPMS heat sinks, particularly those with a gyroid structure, provide enhanced thermal dissipation owing to their high surface area-to-volume ratio and interconnected geometry. Our findings confirm that TPMS heat sinks have promising potential for use as alternatives to conventional wavy designs for advanced thermal management applications. Full article

The “double-high” characteristics of power systems—namely, the high penetration of renewable energy and the widespread use of power electronic devices—have significantly increased operational complexity. This underscores the necessity of adopting coordinated energy storage systems and wind-storage hybrid microgrids to support the black start restoration of thermal power plants. This paper addresses two critical challenges in the black start process of a wind–storage–diesel microgrid: dynamic power coordination and state of charge (SOC) balancing of the energy storage system. A coordinated control strategy is proposed for the entire black start sequence, incorporating SOC equilibrium management. A novel hybrid control architecture is introduced, which effectively integrates grid-forming virtual synchronous generator (VSG)-based energy storage units with grid-following P/Q-controlled storage units, while leveraging the dynamic reactive power support capability of diesel generators. By coordinating SOC balancing among storage units and combining diesel generation with wind power maximum power point tracking (MPPT) control, the strategy enables wind power output to effectively track microgrid load demand. It also ensures reliable reactive power support to prevent black start failure. During periods of power imbalance between wind generation and black start loads, the energy storage system compensates for active power discrepancies. Furthermore, control schemes for both grid-forming and grid-following storage units are enhanced to achieve SOC-based active power distribution, ensuring balanced SOC levels across all units. Finally, a simulation model for the wind–storage–diesel black start is developed in PSCAD/EMTDC, validating the effectiveness and robustness of the proposed control strategy. Full article

Cross-seasonal and cross-regional operations make it inevitable for low-temperature cycling of lithium–ion batteries, which accelerates battery aging and induces large inconsistency between batteries in the battery pack. This causes slight overcharging. However, the influence of long low-temperature cycling on the following slight overcharging aging and aging mechanism under multi aging path is not studied clearly. This affects the function of the battery management system (BMS), including state of health (SOH) prediction, state of charge estimation, etc. This work takes 18,650-type batteries as the study objects. Battery aging at low temperature (−10 °C) and slight overcharging (4.4 V) aging after low-temperature cycling are studied in this work. Hybrid pulse power characteristic, incremental capacity analysis, scanning electron microscope, and X-ray diffraction are used to reveal the aging mechanisms. The results indicate that a negative electrode degradation affects the cycle life of batteries more compared to a positive electrode, and the primary aging mechanisms are “dead lithium” and electrolyte decomposition. Compared to low-temperature cycling, slight overcharging is the lower stress factor. Cycling at low stress factor suppresses aging of battery cycled at high stress factor. When the SOH of battery is near 90%, lithium plating growing at low temperature is consumed after slight overcharging cycling. The generated products suppress further lithium plating. When the SOH is near 80%, although lithium plating is consumed, it also grows continuously. Slight overcharging causes more transition metal dissolution and graphite exfoliation. When SOH is near 90%, thermal management strategies should operate to control operation temperature of battery to avoid further low-temperature cycling. The results in this work are important to battery design and battery management system development. Full article

This study investigates the thermal characteristics of two hybrid nanofluids, single-walled carbon nanotubes with titanium dioxide ($SWCNT-Ti{O}_2$) and multi-walled carbon nanotubes with copper ($MWCNT-Cu$), as they flow over an inclined, porous, and longitudinally stretched cylindrical surface with kerosene as the base fluid. The model takes into consideration all of the consequences of magnetohydrodynamic (MHD) effects, thermal radiation, and Arrhenius-like energy of activation. The outcomes of this investigation hold practical significance for energy storage systems, nuclear reactor heat exchangers, electronic cooling devices, biomedical hyperthermia treatments, oil and gas transport processes, and aerospace thermal protection technologies. The proposed hybrid ANN–numerical framework provides an effective strategy for optimizing the thermal performance of hybrid nanofluids in advanced thermal management and energy systems. A set of coupled ordinary differential equations is created by applying similarity transformations to the governing nonlinear partial differential equations that reflect conservation of mass, momentum, energy, and species concentration. The boundary value problem solver bvp4c, which is based in MATLAB (R2020b), is used to solve these equations numerically. The findings demonstrate that, in comparison to the $MWCNT-Cu/kerosene$ nanofluid, the $SWCNT-Ti{O}_2$/kerosene hybrid nanofluid improves the heat transfer rate (Nusselt number) by up to $23.6\%$. When a magnetic field is applied, velocity magnitudes are reduced by almost $15\%$, and the temperature field is enhanced by around $12\%$ when thermal radiation is applied. The impact of important dimensionless variables, such as the cylindrical surface’s inclination angle, the medium’s porosity, the magnetic field’s strength, the thermal radiation parameter, the curvature ratio, the activation energy, and the volume fraction of nanoparticles, is investigated in detail using a parametric study. According to the comparison findings, at the same flow and thermal boundary conditions, the $SWCNT-Ti{O}_2$/kerosene hybrid nanofluid performs better thermally than its $MWCNT-Cu$/kerosene counterpart. These results offer important new information for maximizing heat transfer in engineering systems with hybrid nanofluids and inclined porous geometries under intricate physical conditions. With its high degree of agreement with numerical results, the ANN model provides a computationally effective stand-in for real-time thermal system optimization. Full article

Polyhedral oligomeric silsesquioxanes (POSS) harness their molecularly precise organic–inorganic hybrid cage architecture to deliver hardness, scratch resistance, and programmable functionality for next-generation transparent coatings. Tailoring of solubility, thermal stability, mechanical robustness, electronic characteristics, and interfacial properties is achieved through strategic peripheral modifications enabled by versatile synthetic methodologies—spanning metal catalysis, metal-free routes, and selective bond activation. Advanced integration techniques, including covalent grafting, chemical crosslinking, UV–thermal dual curing, and in situ polymerization, ensure uniform dispersion while optimizing coating–substrate adhesion and network integrity. The resultant coatings exhibit exceptional optical transparency, mechanical durability, tunable electrical performance, thermal endurance, and engineered surface hydrophobicity. These synergistic attributes underpin transformative applications across critical domains: atomic-oxygen-resistant spacecraft shielding, UV-managing agricultural films, flame-retardant architectural claddings, mechanically adaptive foldable displays, and efficiency-enhanced energy devices. Future progress will prioritize sustainable synthesis pathways, emergent asymmetric cage architectures, and multifunctional designs targeting extreme-environment resilience, thereby expanding the frontier of high-performance transparent protective technologies. Full article

This review examines recent advances in Gallium Nitride (GaN) power semiconductor devices and their growing impact on the development of high-efficiency power conversion systems. It explores innovations in device design, packaging methods, and gate-driving strategies that have improved both performance and reliability. Key metrics such as switching speed, conduction losses, thermal management, and device robustness are analyzed, supported by reliability assessment techniques including Double-Pulse Testing (DPT). The discussion extends to current market dynamics and strategic industry initiatives that have catalyzed widespread GaN adoption. These combined insights highlight GaN’s role as a transformative material offering compact, efficient, and durable power solutions while identifying challenges that remain for broader implementation across diverse industries. Full article

The thermal therapy mask, as a wearable device, requires precise thermal management to ensure therapeutic efficacy and safety, which necessitates a detailed investigation of its heat conduction behavior under complex conditions. However, the heat convective behavior of an orthotropic thermal therapy mask with an embedded line heat source under practical operational conditions has not yet been rigorously investigated. Therefore, this study addresses this specific problem by abstracting it into a 2D orthotropic transient heat conduction problem with a line heat source under Robin BCs, and derives its analytical solution using the SSM without any assumption of solution form. The SSM first transforms the governing equation into the frequency domain via the Laplace transform technique and reformulates it within the Hamiltonian framework. The original problem is then decomposed into two subproblems, which are solved by the method of separation of variables and the symplectic eigen expansion. The final analytical solution is obtained through superposing the solutions of the subproblems, and its accuracy is validated through comparison with the finite element method. The influence of the heat convection coefficient on the thermal behavior is systematically analyzed, revealing that increasing the heat convection coefficient accelerates the procedure from transient to steady state and results in reduced steady-state temperature. Furthermore, the analysis of orthotropic thermal conductivity reveals a “short-plank effect”, where the temperature evolution is limited by the smaller thermal conductivity. This study provides benchmark results for accurate and efficient thermal prediction and may enable an extension to broader applications in flexible electronics such as wearable sensors and displays. Full article

Fecal sludge (FS) requires effective management to mitigate environmental and public health risks and enable resource recovery. This study evaluated the effects of microwave (MW) treatment on FS characteristics and subsequent anaerobic digestion (AD) performance. MW treatment raised FS temperatures to ~96 °C, reducing FS volume by 50% and inducing three thermal phases. Soluble chemical oxygen demand (sCOD) showed a multi-phase pattern, with a maximum solubilization of 29.8% during initial heating due to the solubilization of proteins and carbohydrates. Scanning electron microscopy (SEM) revealed morphological changes, while Fourier transform infrared (FTIR) spectroscopy confirmed that core functional groups remained unchanged. MW-pretreated FS enhanced AD performance, achieving a 17% increase in cumulative methane yield, alongside 18% and 33% improvements in organic loading and methane production rates, respectively. MW treatment influenced the phase distribution of digestate components, showing a shift in nutrient portioning towards the liquid fraction. These results suggest that integrating MW pretreatment into FS management systems can improve energy recovery, reduce treatment costs, and support resource-efficient sanitation solutions. Full article