Search Results (813)

Effective thermal management is critical for high-power lithium-ion batteries to mitigate excessive heat generation and ensure operational reliability. Failure to maintain a uniform temperature distribution can lead to accelerated capacity fading and severe safety risks, such as thermal runaway. In this study, a ferrofluid-based magnetohydrodynamic (MHD) microchannel cooling system was numerically investigated to elucidate the influence of magnetic intensity, magnet geometry, and electrical boundary conditions on flow behavior and heat transfer performance for battery cooling applications. A fully coupled multiphysics model incorporating electromagnetic, fluid flow, and heat transfer phenomena was developed and validated against experimental and numerical data from the literature. The results show that increasing the applied voltage enhances current density and Lorentz force almost linearly, leading to significant flow acceleration and improved convective heat transfer. Electrical insulation effectively suppresses current leakage into the channel walls, increasing the average current density by up to 222% and the Lorentz force by more than 300%. Compared with a cylindrical magnet, a rectangular magnet provides a more uniform magnetic field distribution and stronger near-wall Lorentz forcing, resulting in superior cooling performance. Under a 4C discharge condition, the insulated rectangular magnet reduces the maximum battery temperature by approximately 30% and increases the average Nusselt number by up to 103% relative to the non-insulated case. The findings reveal the critical roles of magnetic-field-controlled flow symmetry and near-wall forcing in MHD-driven microchannels, and provide practical design guidelines for battery cooling systems with no moving mechanical parts and active electromagnetic flow control. Full article

Electromagnetic field-based stimulation has emerged as a promising noninvasive approach for enhancing bone fracture healing. Beyond conventional pulsed electromagnetic field (PEMF) therapies employing spatially uniform fields, dielectrophoretic-force-based (DEPF) stimulation exploits electromagnetic field non-uniformities to induce localized interactions to enhance fracture healing. However, the thermal behavior associated with DEPF-driven PEMF exposure in the presence of metallic orthopedic implants remains largely unexplored. In this study, the thermal response of tissue-like tibia phantoms with and without metallic implants is investigated using an integrated experimental and numerical framework. A custom-designed conical coil is employed to generate non-uniform DEPF excitation capable of affecting the fracture site. Surface temperature evolution is measured using infrared thermal imaging, while electromagnetic power absorption is quantified through specific absorption rate (SAR)-based thermal measurement coupled with a bio-heat formulation. Anatomically realistic tibia phantoms reconstructed from computed tomography data are fabricated via a 3D printer to represent clinically relevant fracture configurations. Experimental results show that the metallic implant exhibits a rapid temperature increase of approximately $0.4 °\mathrm{C}$ within the first few minutes of exposure, followed by thermal stabilization, corresponding to an effective absorbed power of ${\mathrm{SAR}}_{\mathrm{eff},\mathrm{implant}}\approx 2.2 \mathrm{W}/\mathrm{kg}$ inferred from the initial temperature slope. In contrast, the non-conductive resin phantom displays a temperature rise of only $0.05 °\mathrm{C}$ over the same interval, yielding ${\mathrm{SAR}}_{\mathrm{eff},\mathrm{resin}}\approx 0.8 \mathrm{W}/\mathrm{kg}$. These findings demonstrate that implant-related eddy-current losses dominate localized heating under DEPF excitation, while tissue-like media remain weakly affected. This work provides SAR-based experimental evaluation of DEPF stimulation in implanted tibia fracture models, offering new insight into implant-induced electromagnetic heating and its implications for the safety and optimization of DEPF-based bone-healing therapies. Full article

This paper presents a comparative modeling and analysis of an induction furnace for melting aluminum (Al) and copper (Cu), focusing on their electromagnetic behavior and heating performance. The study employs ANSYS Maxwell software version 16.0 with the finite element method (FEM) to simulate eddy current generation, Joule heating, and current density distribution in the metallic workpieces. The effects of coil geometry, input current, and operating frequency (50–100 kHz) on heating efficiency and skin depth are investigated. Estimated heating times based on ohmic losses are provided, revealing significant differences between aluminum and copper due to their distinct electrical and thermal properties. The results demonstrate that higher frequencies concentrate heating near the surface, reducing skin depth, while copper exhibits more uniform heating than aluminum. These findings offer practical insights for optimizing induction furnace design and operation for different non-ferrous metals. Full article

Microwave sintering technology is widely regarded as one of the most promising construction techniques for in situ resource utilization in lunar bases due to its high energy efficiency and unique heating mechanism. However, the extremely low-temperature environment on the lunar surface creates a transient temperature gradient of over a thousand degrees Celsius between the sintered body’s surface and its interior. This temperature difference induces significant thermal stress during the cooling process, leading to macroscopic surface cracks and even structural failure, which severely limits the engineering feasibility of this technology. To evaluate the surface integrity of lunar in situ sintered bodies and determine the safe processing window for microwave sintering, this study develops a multiphysics computational model that couples electromagnetic, thermal, and stress fields. The results show that when the cooling rate is below 15 °C/min, the surface stress remains below the material’s tensile strength threshold, effectively preventing crack formation. However, at a cooling rate of 16 °C/min, the surface stress exceeds this threshold, leading to crack initiation. Further analysis reveals that the cooling rate significantly affects the microstructure, with slow cooling maintaining a dense structure, while fast cooling promotes the formation of microcracks, particularly in regions with low Si/Al content. This study provides a reference for the microwave sintering process of lunar regolith and proposes a strategy of controlling the cooling rate below 15 °C/min. Full article

Electromagnetic shielding (EMS) materials play an important role in modern technology and industry, especially in electronic equipment, communication technology, military applications and so on. With the continuous progress of technologies and the increasing demands for functional materials, EMS materials are expanding towards flexibility and being lightweight. Recently, metal–organic frameworks (MOFs) have garnered significant attention in the EMS field due to their unique structure and adjustable properties. In this paper, alloy-based porous nanospheres (CCZ-C) were fabricated by heat-treatment using CoCuZn-MOFs as precursors, and then electrospun CCZ-C/PVDF nanofiber membranes (NFMs) were prepared in a large-quantity by blending them with PVDF. Afterwards, a hierarchical porous structured NFM (MPPA) was obtained by loading a highly conductive Ag nanolayer on the surface of CCZ-C/PVDF nanofibers using pDA as a binder. By adjusting the CCZ-C content, it was determined that the EMS performance of MPPA was highest when the CCZ-C content was 2 wt.%, with an average SSE of 12,017.01 dB·cm²·g⁻¹. This was because the hierarchical porous structure formed by adding an appropriate amount of CCZ-C further improved the electromagnetic attenuation and impedance matching of MPPA. Full article

The vehicle-mounted flywheel battery is a complex assembly of multiple components that is subject to intense multi-physical field coupling and external disturbances, which lead to real-time changes in system parameters and reduce control performance. The aim of this study is to enhance the robustness and dynamic stability of the system under emergency avoidance conditions. Its internal multiphysics field coupling is intricate, and external disturbances further intensify the cross-coupling. Building upon this method, a highly robust control strategy with real-time coupling characteristic parameters is designed in this study. First, a bidirectional coupling method combining electromagnetism, heat, and structure fields was proposed. This method captured the dynamic interactions among the magnetic, thermal, and structural fields. Based on this analysis, a coupling characteristic function was extracted to quantify the real-time coupling strength. Then, this function was mapped into the parameters of the sliding mode controller. Adaptive gain adjustment can be achieved without relying on an accurate system model. The key assumptions include linear material properties within the operational temperature range and negligible unsteady turbulence effects in airflow. Full article

Plastic pyrolysis can not only effectively solve the environmental pollution caused by the large use of plastics products but also can produce valuable chemical products to alleviate the energy shortage problem. Firstly, this study designs a microwave pyrolysis device for polypropylene plastic based on a symmetrical circular waveguide slot radiation structure. The microwave energy is fed in through the bottom symmetrical circular waveguide port, transmitted to the slot array unit after passing through the horn amplification structure, and then uniformly radiated into the polypropylene plastic. Secondly, the finite element method is employed to conduct multi-physics field coupling calculations for the electromagnetic field, temperature field, chemical reaction field, mass transfer field of concentrated substances, and fluid field involved in the microwave pyrolysis process. Finally, to improve the efficiency of microwave pyrolysis, the wave-absorbing material SiC is introduced to investigate the effects of different doping methods and doping mass ratios m_SiC:m_PP on pyrolysis temperature distribution uniformity, pyrolysis gas yield (Y_G), energy consumption (Q), gas composition, and higher heating value (HHV). The results indicate that optimal pyrolysis performance is achieved when the microwave power is 1000 W, the pyrolysis time is 9.2 min, SiC is uniformly doped and the mass ratio is m_SiC:m_PP = 3:1. The COV of temperature is a mere 0.0004, the Y_G reaches 75.15 wt.%, and Q is 0.15 kWh, the HHV is up to 85.32 MJ/Nm³, and the percentages of C₃H₆ and CH₄ are relatively high at 72% and 11.4%. These findings confirm the designed microwave pyrolysis device can achieve uniform and high-efficiency pyrolysis capability for polypropylene plastic. Full article

Parallel laying of high-voltage cables will generate a zero-sequence current, due to spatial electromagnetic induction, which reduces the cable’s current-carrying capacity, causing heating and corrosion of the grounding points and deteriorating grounding performance. Currently, there is a lack of effective control measures. This article establishes a calculation model for the cable sheath current under the condition of double circuit cable cross interconnection grounding, analyzes the causes of a zero-sequence grounding current in a double circuit cable sheath, and proposes an optimal phase sequence selection method, considering load changes with the goal of maximizing the probability of the cable sheath current, not exceeding the standard. The results show that when the double circuit cable is evenly distributed in the cross interconnection section, the zero-sequence grounding current will be generated on the metal sheath of the cable, causing an excessive total grounding current. By applying the proposed probability-based phase-sequence optimization, the likelihood that both circuits simultaneously satisfy the sheath-current criterion can be significantly improved; for example, under representative layouts and load distributions, the “both-within-limit” probability can reach 53.3% (horizontal layout), 76.2% (horizontal equilateral triangle layout), 90.5% (vertical layout), and 81.6% (vertical equilateral triangle layout). For different working conditions, selecting the optimal load phase sequence combination by maximizing the probability of the sheath current and not exceeding the standard within the current carrying area can help to reduce the cable sheath current. Full article

To solve slot temperature accumulation in high thrust density permanent magnet linear synchronous motors (PMLSMs), this paper proposes an additive manufacturing (AM)-based variable cross-section winding design for coating-cooled tapered PMLSMs. Integrating the magnetic circuit features of tapered PMLSMs and AM windings’ technical merits, the motor’s operating mechanism and electromagnetic distribution are analyzed. With the coating cooling structure as the thermal management foundation, simulation reveals the motor’s temperature distribution under water cooling, defining core slot thermal management requirements. A novel cross-section winding design is then presented: first, a lumped-parameter thermal network model quantifies the coupling between the winding cross-sectional area and slot heat source distribution; second, a greedy algorithm optimizes the winding cross-section globally to reduce the slot hot-spot temperature and suppress temperature rise. Validated by a fabricated tapered PMLSM stator prototype and static temperature-rise experiments, the results confirm that winding cross-section reconstruction optimizes heat distribution effectively, offering a new approach for temperature rise suppression in high thrust density PMLSMs. Full article

Missile-borne active phased array antennas have been widely used in missile guidance for their beam agility, multifunctionality, and strong anti-interference capabilities. However, due to space constraints on the platform and difficulty in heat dissipation, the thermal power consumption of the antenna array can easily lead to excessive temperature, causing two primary issues: first, temperature-induced drift in T/R components, resulting in amplitude and phase errors in the feed current; second, temperature-dependent ripple voltage in the array’s secondary power supply, which exacerbates feed errors. Both issues degrade the electromagnetic performance of the array antenna. To mitigate these effects, this paper investigates feed errors and compensation methods in high-temperature environments. First, a synchronous Buck circuit ripple coefficient model is developed, and an electromagnetic–temperature coupling model is established, incorporating temperature-dependent feed current characteristics, and the law of electromagnetic performance changes is analyzed. On this basis, an electromagnetic performance compensation method based on a genetic algorithm is proposed to optimize the quantization compensation amount of the amplitude and phase of each element under the effect of high temperature. Full article

To promote the transition to a cleaner energy structure and support the achievement of the “carbon peak and carbon neutrality” goals, concentrated solar power (CSP) technology has attracted increasing attention. The molten salt globe valve, as a key control component in CSP systems, faces significant challenges related to low-temperature salt crystallization and thermal stress control. This study proposes an active electromagnetic induction heating method based on a triangular double-helix cross-section coil to address issues such as molten salt blockage in the seal bellows and excessive thermal stress during heating. First, electromagnetic simulation comparisons show that the ohmic loss of the proposed coil is approximately 3.5 times and 1.8 times higher than that of conventional circular and rectangular coils, respectively, demonstrating superior heating uniformity and energy efficiency. Second, transient electromagnetic-thermal-fluid-structure multiphysics coupling analysis reveals that during heating, the temperature in the bellows seal region stabilizes above 543.15 K, exceeding the solidification point of the molten salt, while the whole valve reaches thermal stability within about 1000 s, effectively preventing local solidification. Finally, thermal stress analysis indicates that under a preheating condition of 473.15 K, the transient thermal shock stress on the valve body and bellows is reduced by 266.84% and 253.91%, respectively, compared with the non-preheating case, with peak stresses remaining below the allowable stress limit of the material, thereby significantly extending the service life of the valve. This research provides an effective solution for ensuring reliable operation of molten salt valves and improving the overall performance of CSP systems. Full article

Three different Gas Tungsten Arc Welding methods—DC single electrode, DC double electrode, and PC double electrode—were analyzed using SS304 steel as the base material. Numerical models were developed to simulate the arc plasmas and calculate heat flux, current density, and wall shear stress on the surface of the workpiece. These data were used as input to simulate the weld pools across all three configurations. Experimental validation showed a good agreement with the numerical results. In the double-electrode setup, electromagnetic interaction caused the arcs to deflect, resulting in an 8% reduction in the maximum heat flux and a 4% decrease in the maximum current density. Marangoni stress had a notable effect on the weld pool shape, creating a -shaped pool with the stationary single-electrode setup, whereas the double-electrode setup produced a -shaped pool after 2 s. In the moving weld pool configurations, the sizes of the pools were maximum at the trailing electrodes. The pool was 1.7 mm deep and 5.6 mm wide in DC double- and 1.4 mm deep and 5.4 mm wide in PC double-electrode configurations. The pool depth and width were only 1.0 mm and 4.2 mm when a DC single-electrode setup was used. Comparing the three methods, the DC double-electrode setup produced the largest pool size. The findings of this research offer guidance for enhancing different arc settings and electrode arrangements to attain the intended welding quality and performance. Full article

The contradiction between the threshold values of carbon nanomaterials in cement-based materials for enhancing electrical, magnetic, and mechanical properties appears irreconcilable in previous studies. Reducing the numerical differences of these thresholds of carbon nanomaterials in cement-based materials is a straightforward approach to resolving the predicament. Flash graphene powder (FGP) with varying dosages is used to prepare the modified Portland cement paste in this work. Hydration heat release behaviours and the morphologies of hydrates are significantly impacted due to the unique turbostratic graphene layers. The percolation threshold of FGP in paste approximates its thresholds for enhancing the strength and absorption of electromagnetic waves (EMWs), which is 0.50 wt.% of cement. The compressive and flexural strength values of samples with 0.50 wt.% FGP increased by 59.5% and 22.4%, respectively, compared with the blank sample. The minimum EMWs loss value of the sample with 0.50 wt.% FGP is −12.2 dB with an effective absorption bandwidth value of 7.76 GHz in the EMWs frequency between 2 and 18 GHz. The smaller Portlandite crystals are associated with better conductive and impedance-matching properties, resulting in significantly improved EMWs absorption in the Ku band. This work proposes a possible solution that involves using FGP to replace normal graphene, thereby alleviating the contradiction and reducing the gaps in the graphene thresholds in cement paste and enhancing mechanical and electrical conductivity and EMWs absorption properties. Full article

The paper provides a comprehensive overview of stray losses in conductive structural parts of power transformers, addressing the effects of stray magnetic fields on simple conductive plates, the distribution of additional losses across structural components and measures for their reduction. It examines the (im)possibility of directly measuring stray losses and presents methods for their indirect measurement, highlighting the generation of fault gases due to thermal faults and the importance of understanding multiphysical (electromagnetic–thermal) coupling in calculating stray losses. A problem rarely mentioned in the literature but confirmed here by measurements, is the excessive heating of the connecting elements of the clamping system caused by circulating currents. Full article

Transient arcing often occurs as an electric locomotive traverses an electrical sectioning overlap (ESO), deteriorating current collection stability and reducing the durability of the pantograph–catenary (PC) system. In this study, the formation mechanism and electrical evolution characteristics of transient arcing in the ESO region are investigated through theoretical analysis and numerical simulations. First, based on the dynamic motion of the locomotive passing through the ESO, the transient arcing mechanism of the ESO is clarified, and the plasma characteristics of the arc are described. Then, the electromagnetic, airflow, and thermal field interactions within the PC contact gap during arc ignition are analyzed. A Multiphysics coupled PC arc model is developed, incorporating aerodynamic, electromagnetic, and heat transfer effects. Subsequently, finite element meshing and boundary conditions are applied to simulate the transient evolution of the ESO arc. Finally, the transient arcing characteristics of the ESO are analyzed. The results indicate that the current density is highly concentrated at the initial arcing stage and gradually forms an axially symmetric conductive channel (approximately 10⁷ A/m²), which shifts upward as the contact gap increases. Moreover, due to the geometric discontinuity of the ESO, a strong localized electric field develops near the wire edge, leading to arc root migration and reignition. Full article