In order to investigate the leak detection strategy of a heating network,a space-based simulation mathematical model for the heating network under leakage conditions is built by graph theory.The pressure changes of al...In order to investigate the leak detection strategy of a heating network,a space-based simulation mathematical model for the heating network under leakage conditions is built by graph theory.The pressure changes of all the nodes in the heating network are obtained from node leak and pipe leak conditions.Then,a leakage diagnosis system based on the back propagation（BP）neural network is established.This diagnosis system can predict the leakage pipe by collecting the pressure change data of the monitoring points,which can preliminary estimate the leak location.The usefulness of this system is proved by an example.The experimental results show that the forecast accuracy by this diagnosis system can reach 100%.展开更多
The determination of source-side extracted heating parameters is of great significance to the economic operation of cogeneration systems.This paper investigated the coupling performance of a cogeneration heating and p...The determination of source-side extracted heating parameters is of great significance to the economic operation of cogeneration systems.This paper investigated the coupling performance of a cogeneration heating and power system multidimensionally based on the operating characteristics of the cogeneration units,the hydraulic and thermodynamic characteristics of the heating network,and the energy loads.Taking a steam network supported by a gas-steam combined cycle cogeneration system as the research case,the interaction effect among the source-side prime movers,the heating networks,and the terminal demand thermal parameters were investigated based on the designed values,the plant testing data,and the validated simulation.The operating maps of the gas-steam combined cycle cogeneration units were obtained using THERMOFLEX,and the minimum source-side steam parameters of the steam network were solved using an inverse solution procedure based on the hydro-thermodynamic coupling model.The cogeneration operating maps indicate that the available operating domain considerably narrows with the rise of the extraction steam pressure and flow rate.The heating network inverse solution demonstrates that the source-side steam pressure and temperature can be optimized from the originally designed 1.11 MPa and 238.8°C to 1.074 MPa and 191.15°C,respectively.Under the operating strategy with the minimum source-side heating parameters,the power peak regulation depth remarkably increases to 18.30%whereas the comprehensive thermal efficiency decreases.The operation under the minimum source-side heating steam parameters can be superior to the originally designed one in the economy at a higher price of the heating steam.At a fuel price of$0.38/kg and the power to fuel price of 0.18 kg/(kW·h),the critical price ratio of heating steam to fuel is 119.1 kg/t.The influence of the power-fuel price ratio on the economic deviation appears relatively weak.展开更多
Giant magnetoimpedance(GMI)sensors are increasingly employed in modern magnetic sensing technologies.However,improving the GMI performance of magnetic cores remains challenging due to intrinsic limitations in material...Giant magnetoimpedance(GMI)sensors are increasingly employed in modern magnetic sensing technologies.However,improving the GMI performance of magnetic cores remains challenging due to intrinsic limitations in material properties and structural stability.In this work,we explore the use of Joule heating to enhance the GMI response of Fe_(20)Ni_(80)/Cu composite wires.By applying a current of 1.8 A for 10 min,notable improvements in magnetic domain uniformity and a reduction in domain spacing are observed.Under these conditions,GMI ratios reach 1870% in the non-diagonal mode and1147%in the diagonal mode,respectively,highlighting their potential for applications in high-precision weak magnetic field sensing.展开更多
In this study,an architecture featuring a gradient conductive network structure and three-dimensional dual-continuous network structure is constructed in a carbon nanotubes/cellulose-boron nitride/poly(vinyl alcohol)(...In this study,an architecture featuring a gradient conductive network structure and three-dimensional dual-continuous network structure is constructed in a carbon nanotubes/cellulose-boron nitride/poly(vinyl alcohol)(CNT/cellulose-BN/PVA)composite.Using cellulose aerogel as a template,CNT were incorporated into the cellulose template by vertically impregnating the CNT suspension.Following the impregnation of BN/PVA and high-pressure compression,three-dimensional dual-continuous network structure was successfully constructed in the CNT/cellulose-BN/PVA composite.The comprehensive performance of the composite,including electromagnetic interference(EMI)shielding and Joule heating performance,was investigated.The results indicate that the total EMI shielding effectiveness(SE)for the CNT/cellulose-BN/PVA composite reveals similar values for electromagnetic waves incident from different directions,but totally different shielding mechanisms.For the CNT/cellulose-BN/PVA composite with three impregnation cycles of CNT,the EMI SE values exceeded 39 dB for electromagnetic waves incident from both the high-and low-CNT-content sides.93%of the microwaves were reflected when electromagnetic waves were incident from the high-CNT-content side,while the reflection coefficient decreased to 0.44 for the transverse direction.In addition,the construction of the dual-continuous network structure enabled the composite to exhibit both excellent electrical conductivity and good thermal conductivity simultaneously,endowing the material with good Joule heating performance.CNT/cellulose-BN/PVA composite films have significant potential for application as EMI shielding materials in extremely cold weather.展开更多
Thermal storage electric heating(TSEH),as a prevalent variable load resource,offers significant potential for enhancing system flexibility when aggregated into a cluster.To address the uncertainties of renewable energ...Thermal storage electric heating(TSEH),as a prevalent variable load resource,offers significant potential for enhancing system flexibility when aggregated into a cluster.To address the uncertainties of renewable energy and load forecasting in active distribution networks(ADN),this paper proposes a multi-timescale coordinated optimal dispatch strategy that incorporates TSEH clusters.It utilizes the thermal storage characteristics and short-term regulation capabilities of TSEH,along with the rapid and gradual response characteristics of resources in active distribution grids,to develop a coordinated optimization dispatch mechanism for day-ahead,intraday,and real-time stages.It provides a coordinated optimized dispatch technique across several timescales for active distribution grids,taking into account the integration of TSEH clusters.The proposed method is validated on a modified IEEE 33-node system.Simulation results demonstrate that the participation of TSEH in collaborative optimization significantly reduces the total system operating cost by 8.71%compared to the scenario without TSEH.This cost reduction is attributed to a 10.84%decrease in interaction costs with the main grid and a 47.41%reduction in network loss costs,validating effective peak shaving and valley filling.The multi-timescale framework further enhances economic efficiency,with overall operating costs progressively decreasing by 3.91%(intraday)and 4.59%(real-time),and interaction costs further reduced by 5.34%and 9.25%,respectively.Moreover,the approach enhances system stability by effectively suppressing node voltage fluctuations and ensuring all voltages remain within safe operating limits during real-time operation.Therefore,the proposed approach achieves rational coordination of diverse resources,significantly improving the economic efficiency and stability of ADNs.展开更多
The integrated electricity-heat-hydrogen system(IEHHS)facilitates the efficient utilization of multiple energy sources,while the operational flexibility of IEHHS is hindered by the high heat inertia of alkaline electr...The integrated electricity-heat-hydrogen system(IEHHS)facilitates the efficient utilization of multiple energy sources,while the operational flexibility of IEHHS is hindered by the high heat inertia of alkaline electrolyzers(AELs)and the variations of renewable energy.In this paper,we propose a robust scheduling of IEHHS considering the bidirectional heat exchange(BHE)between AELs and district heating networks(DHNs).First,we propose an IEHHS model to coordinate the operations of AELs,active distribution networks(ADNs),and DHNs.In particular,we propose a BHE that not only enables the waste heat recovery for district heating but also accelerates the thermal dynamics in AELs.Then,we formulate a two-stage robust optimization(RO)problem for the IEHHS operation to consider the variability of renewable energy in ADNs.We propose a new solution method,i.e.,multi-affine decision rule(MADR),to solve the two-stage RO problem with less conservatism.The simulation results show that the operational flexibility of IEHHS with BHE is remarkably improved compared with that only with unidirectional heat exchange(UHE).Compared with the traditional affine decision rule(ADR),the MADR effectively reduces the IEHHS operating costs while guaranteeing the reliability of scheduling strategies.展开更多
The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating(MWH)in two scenarios:intermittently and conti...The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating(MWH)in two scenarios:intermittently and continuously.The mechanical properties and surface appearance of the heated samples were also investigated.Continuous and intermittent microwave drying kinetic experiments were conducted at a frequency of 2.45 GHz using a microwave laboratory oven at 300,500,and 1000 watts.Drying rate curves indicated three distinct phases of MWH.Increasing the microwave power with a shorter drying time led to rapid increases in internal temperature and water evaporation rates of the heated samples.Mechanical results indicated that samples heated under continuous MW(Microwave)power at 300 watts had a modulus of rupture(MOR)and modulus of elasticity(MOE)in three static bending tests higher than 29%and 36%,respectively,than samples heated at 1000 watts.Intermittent microwave heating(IMWH)of samples at 300 and 1000 watts produced the highest MOR and MOE values of 31%and 51%,respectively,unlike those heated under continuous microwave heating(CMWH).External qualitative observation showed that samples heated at high microwave power had severe surface checks.These defects were missing when using IMWH.An analysis of variance(ANOVA)showed that mechanical properties were linked to both microwave power level and the heating scenario,except for MOR in axial compression under CMWH.展开更多
With the continuous advancement of electronic devices,flexible thin films with both thermal manage-ment functions and excellent electromagnetic interference(EMI)shielding properties have received much attention.Hence,...With the continuous advancement of electronic devices,flexible thin films with both thermal manage-ment functions and excellent electromagnetic interference(EMI)shielding properties have received much attention.Hence,inspired by Janus,a CNF/MXene/ZnFe2O4@PANI composite film with an asymmetric gradient alternating structure was successfully prepared by adjusting the filler content of the conduc-tive and magnetic layers using a vacuum-assisted filtration method.Benefiting from the magnetic reso-nance and hysteresis loss of ZnFe2O4@PANI,conductive loss and dipole polarization of MXene,as well as the exclusive"absorption-reflection-reabsorption"shielding feature in the alternating multilayered films,CM&CZFP-4 G film has superior EMI shielding performance,with an EMI SE of up to 45.75 dB and shield-ing effectiveness of 99.99%.Surprisingly,the composite film maintains reliable EMI shielding properties even after prolonged erosion in harsh environments such as high/low temperatures,high humidity,acids and alkalis.Furthermore,the CM&CZFP-4 G responded quickly within about 50 s and reached a maximum steady-state temperature of 235.8℃ at an applied voltage of 9.0 V,indicating the obtained film acquired outstanding and controllable Joule heating performance.This result was attributed to the homogeneous dispersion of MXene to build up a conductive network and endow the CNF/MXene with high conduc-tivity.Meanwhile,the fire resistance of CM&CZFP-4 G was significantly improved compared to pure CNF,which guaranteed fire safety during its application.Additionally,contributed by long fiber entanglement of CNF,extensive hydrogen-bonding interactions and multilayer structural design,the CM&CZFP-4 G film exhibits excellent mechanical characteristics,with the tensile strength and fracture strain of 27.74 MPa and 6.21%,separately.This work offers a creative avenue to prepare multifunctional composite films with electromagnetic shielding and Joule heating for various application environments.展开更多
This study investigates the heat transfer and flow dynamics of a ternary hybrid nanofluid comprising alumina,copper,and silica/titania nanoparticles dispersed in water.The analysis considers the effects of suction,mag...This study investigates the heat transfer and flow dynamics of a ternary hybrid nanofluid comprising alumina,copper,and silica/titania nanoparticles dispersed in water.The analysis considers the effects of suction,magnetic field,and Joule heating over a permeable shrinking disk.Amathematicalmodel is developed and converted to a systemof differential equations using similarity transformation which then,solved numerically using the bvp4c solver in Matlab software.The study introduces a novel comparative analysis of alumina-copper-silica and alumina-coppertitania nanofluids,revealing distinct thermal conductivity behaviors and identifying critical suction values necessary for flow stabilization.Dual solutions are found within a specific range of parameters such that the minimum required suction values for flow stability,with S_(c)=1.2457 for alumina-copper-silica/water and S_(c)=1.2351 for alumina-coppertitania/water.The results indicate that increasing suction by 1%enhances the skin friction coefficient by up to 4.17%and improves heat transfer efficiency by approximately 1%,highlighting its crucial role in stabilizing the opposing flow induced by the shrinking disk.Additionally,the inclusion of 1%silica nanoparticles reduces both skin friction and heat transfer rate by approximately 0.28%and 0.85%,respectively,while 1%titania concentration increases skin friction by 3.02%but results in a slight heat transfer loss of up to 0.61%.These findings confirm the superior thermal performance of alumina-copper-titania/water,making it a promising candidate for enhanced cooling systems,energy-efficient heat exchangers,and industrial thermal management applications.展开更多
The vigorous development of modern electronic communication demands multi-functional materials with exceptional electromagnetic interference(EMI)shielding.However,constructing lightweight and highly efficient metal-fr...The vigorous development of modern electronic communication demands multi-functional materials with exceptional electromagnetic interference(EMI)shielding.However,constructing lightweight and highly efficient metal-free carbon-based EMI shielding materials remains a huge challenge,particularly with robust EMI responses across a broadband frequency.Herein,a broadband(8-27 GHz)and strong EMI shielding response nitrogen-doped carbon plate(NCP)is constructed by a pressing and two-step pyroly-sis process.The layered stacking structure and N-doping impart extraordinary EMI shielding performance to the carbon plate,achieving EMI shielding effectiveness values of 82.60,95.44,and 104.12 dB in the X band,Ku band,and K band,respectively.Notably,the overall thickness of NCP was<1 mm.Moreover,the NCP exhibits remarkable joule heating performance with a low driving voltage(≤3 V)and a fast elec-trothermal response.This work enables the potential for the development of metal-free carbon materials with lightweight,highly efficient and broadband-strong EMI shielding performance.展开更多
The cold-rolled quenching and partitioning(Q&P)steel with an initial microstructure of deformed ferrite and pearlite was studied.The microstructural evolution under various heating rates of 1.78,50,and 300℃/s was...The cold-rolled quenching and partitioning(Q&P)steel with an initial microstructure of deformed ferrite and pearlite was studied.The microstructural evolution under various heating rates of 1.78,50,and 300℃/s was investigated using microstructural characterization and theoretical modeling.At the same time,the characteristics of recrystallization and austenite formation kinetics were decoupled by examining recrystallized ferrite and deformed ferrite as initial conditions.The findings revealed that the austenite formation during continuous heating can be simplified into two stages:(i)the early nucleation-dominated formation stage and(ii)the later grain growth-dominated stage,resulting in the development of a modified two-stage model based on Johnson-Mehl-Avrami-Kolmogorov.Further experiments confirmed that when the austenite volume fraction exceeded approximately 5% at a heating rate of 1.78℃/s,ferrite recrystallization was suppressed.In consequence,a mixed model including recrystallization kinetics was employed to couple the austenite formation occurring in deformed ferrite and recrystallized ferrite,thereby describing the austenite formation kinetics affected by recrystallization.Precise predictions of non-isothermal austenite formation kinetics in cold-rolled Q&P steel were achieved during slow and ultrafast heating processes by integrating the suppression effect into the model for austenite formation.展开更多
Alginate-based magnetic micro/millirobots have demonstrated significant potential for biomedical applications due to their flexible structures and capacity to carry various types of cargo,such as cells,enabling target...Alginate-based magnetic micro/millirobots have demonstrated significant potential for biomedical applications due to their flexible structures and capacity to carry various types of cargo,such as cells,enabling targeted therapy to specific diseased regions within the body.Their active therapy is typically achieved through magnetic actuation and magnetic heating,while monitored by medical imaging methods like CT which pose additional risks due to radiation exposure.In the last decades,a novel imaging method for superparamagnetic materials,known as magnetic particle imaging(MPI),has been under active development,offering not only positional tracking but also the ability to measure concentration and temperature.Here,we report the world's first MPI-traceable magnetic hydrogel robots,which employ a combination of iron oxide nanoflowers,NdFeB powder,and calcium alginate.Unlike previous magnetic alginate robots composed of a single magnetic material,the synergistic combination of NdFeB and nanoflowers enables these robots to exhibit triple magnetic functionalities:magnetic heating,locomotion at low magnetic fields,and tracking,all of which can be controlled using a single all-in-one electromagnetic coil system.The effects of various magnetization fields,as well as different concentrations of NdFeB and nanoflowers on the robots'magnetic properties were analyzed.This led to the development of three types of triple-function robots(spiral,droplet,and hybrid),with experimental results demonstrating biocompatibility,a magnetic heating temperature increase of over 10℃in plasma fluid under a magnetic field of 13 kA·m^(-1)at 200 kHz,locomotion speeds of up to 25 mm·s^(-1)in fields below 2 mT,and an MPI tracking error of 2.8 mm with a selection field of 0.4 mT·mm^(-1).Additionally,the robots'capacity for localized thermal therapy and selectively targeted cell delivery,as well as their locomotion within a medical phantom against a maximum flow of 50 mm·s^(-1)were demonstrated.展开更多
The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF...The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.展开更多
The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to...The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to improve thermal efficiency.In this work,buoyancy-induced flow above two heating elements flush-mounted at the bottom of a square enclosure containing air is numerically investigated over a range of Rayleigh numbers(0<Ra≤1.5×10^(8)),with a focus on equal and unequal heat flux conditions under a constraint of constant total thermal energy input.Distinct flow transitions are observed in both cases,leading to the identification of three flow regimes:Steady,periodic unsteady,and chaotic unsteady.Two types of periodic flows are distinguished,in which the first is a periodic flow dominated by a fundamental frequency(FF)and its integer-multiple frequencies(INTMF),while the second is a more complex periodic flow featuring FF,INTMF,and their sub-harmonics.The transitions between these regimes are affected by the relative heat flux of the two heaters.When the heat flux of the two heaters is unequal,the range of Rayleigh numbers corresponding to periodic flow is suppressed.It is also found that the time-averaged maximum temperature of the strong heater increases more rapidly with Ra,while that of the weak heater increases more slowly,reflecting the interaction between buoyancy-driven flow dynamics and asymmetric heat input.Analysis of the time-averaged Nusselt number demonstrates that heat dissipation from the isothermal walls remains roughly equivalent,even when the heat flux of the two heaters differs by a factor of two.These findings highlight the critical roles of Rayleigh number,the number of heaters,and the heat flux ratio of the heaters in determining heat transfer and flow characteristics for buoyancy-driven convection systems,providing important theoretical support and design references for engineering scenarios such as electronic devices and design of new energy systems.展开更多
Oat milk has gained widespread consumer acceptance for its creamy texture,β-glucan content,and environmental sustainability.However,its relatively low protein content(typically 2-3 g/serving)presents a nutritional li...Oat milk has gained widespread consumer acceptance for its creamy texture,β-glucan content,and environmental sustainability.However,its relatively low protein content(typically 2-3 g/serving)presents a nutritional limitation,largely due to poor protein solubility.This study investigated how processing conditions influence protein content and functional stability in oat-based systems by applying two treatments:(1)α-amylase enzymatic hydrolysis,and(2)pH-shifting(from pH 7 to 12 and back)with mild heating(50℃for 10 or 30 min).Oat protein solutions were formulated from two sources:oat flour(OF)and oat protein isolate(OPI).Results suggests that α-amylase pretreatment effectively reduced starch-driven viscosity in OF,facilitating better sample handling and centrifugation.Following pH-shifting and heat treatment,both OF and OPI solutions showed significantly improved protein solubility,with protein content increased from 2.0 to~6.5 g/serving.These changes were accompanied by reduced precipitation,smaller particle sizes,and more negative zeta potential values,indicating enhanced colloidal stability.SDS-PAGE analysis revealed the presence of low-molecular-weight protein fractions,supporting increased solubilization.Fluorescence microscopy confirmed the formation of smaller,more uniformly dispersed particles in treated samples compared to controls.However,noticeable darkening or browning occurred under high-pH heating,indicating potential challenges in color control.The findings provide useful information for future industrial applications and product innovation in the plant-based beverage sector.展开更多
Nuclear heating plays an important aspect in design and deployment of both fission and fusion reactors and experimental devices in terms of cooling requirements. Two experimental campaigns in the framework of a collab...Nuclear heating plays an important aspect in design and deployment of both fission and fusion reactors and experimental devices in terms of cooling requirements. Two experimental campaigns in the framework of a collaboration project between the French Atomic and Alternative Energy Commission(CEA) and Jožef Stefan Institute(JSI), Slovenia, have been performed at the JSI TRIGA reactor for the experimental assessment of nuclear heating in fission and fusion-relevant materials by the differential calorimetry technique, based on the CALMOS and CARMEN differential calorimeters, previously developed at CEA. The results of the first campaign performed at reactor powers between 100 and 250 kW have already been reported, highlighting some measurement difficulties. Therefore, the second campaign was performed at a lower reactor power of 30 kW to overcome these issues. Moreover, a computational analysis of the experiments was performed using the JSIR2S code package to calculate the nuclear heating levels. Both experiments and their reproduction by simulations are described in detail. We present a comparison of the previously reported measured nuclear heating values of the first campaign with the computational results, with consistent underestimation by simulations by 8–35%. We report the experimental and computational results for the second experimental campaign performed at a reactor power of 30 kW. The simulated heating values were in agreement with the measurements within the measured heating uncertainty, with simulated heating 2.7–11.3% lower than the experimental values.展开更多
This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in...This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in compact cooling systems,such as those used in heat exchangers.A two-dimensional,steady-state Computational Fluid Dynamic(CFD)model is developed in ANSYS Fluent to simulate the behavior of an incompressible ferrofluid under applied constant heat flux and magnetic fields.The magnetic force is modeled using the Kelvin force,which acts on magnetized nanoparticles in response to spatially varying electromagnetic fields generated by two strategically positioned current-carrying wires.The effects of magnetic field strength,quantified by the magnetic number(Mn),on flow behavior and temperature distribution are thoroughly analyzed.The results indicate that increasing Mn leads to higher Nusselt numbers,demonstrating enhanced convective heat transfer.Secondary vortices induced by magnetic forcing improve fluid mixing,particularly in curved regions of the pipe.A mesh-independence study and model validation with benchmark data support the reliability of the numerical framework.This work highlights the potential of magnetic-field-assisted thermal control in energy-efficient cooling applications and provides a foundation for the further development of advanced ferrofluid-based heat transfer systems.展开更多
Flash Joule heating(FJH),as a high-efficiency and low-energy consumption technology for advanced materials synthesis,has shown significant potential in the synthesis of graphene and other functional carbon materials.B...Flash Joule heating(FJH),as a high-efficiency and low-energy consumption technology for advanced materials synthesis,has shown significant potential in the synthesis of graphene and other functional carbon materials.Based on the Joule effect,the solid carbon sources can be rapidly heated to ultra-high temperatures(>3000 K)through instantaneous high-energy current pulses during FJH,thus driving the rapid rearrangement and graphitization of carbon atoms.This technology demonstrates numerous advantages,such as solvent-and catalyst-free features,high energy conversion efficiency,and a short process cycle.In this review,we have systematically summarized the technology principle and equipment design for FJH,as well as its raw materials selection and pretreatment strategies.The research progress in the FJH synthesis of flash graphene,carbon nanotubes,graphene fibers,and anode hard carbon,as well as its by-products,is also presented.FJH can precisely optimize the microstructures of carbon materials(e.g.,interlayer spacing of turbostratic graphene,defect concentration,and heteroatom doping)by regulating its operation parameters like flash voltage and flash time,thereby enhancing their performances in various applications,such as composite reinforcement,metal-ion battery electrodes,supercapacitors,and electrocatalysts.However,this technology is still challenged by low process yield,macroscopic material uniformity,and green power supply system construction.More research efforts are also required to promote the transition of FJH from laboratory to industrial-scale applications,thus providing innovative solutions for advanced carbon materials manufacturing and waste management toward carbon neutrality.展开更多
This paper is concerned with an initial boundary value problem for the planar magnetohydrodynamic compressible flow with temperature dependent heat conductivity in a half-line.In particular,the transverse magnetic fie...This paper is concerned with an initial boundary value problem for the planar magnetohydrodynamic compressible flow with temperature dependent heat conductivity in a half-line.In particular,the transverse magnetic field is assumed to satisfy the Neumann boundary condition,which was first investigated by Kazhikhov in 1987.We establish the global existence of the unique strong solutions to the MHD equations without any smallness conditions on the initial data.More precisely,our result can be regarded as a natural generalization of Kazhikov’s result for applying the constant heat-conductivity in bounded domains to the degenerate case in unbounded domains.展开更多
An efficient data-driven numerical framework is developed for transient heat conduction analysis in thin-walled structures.The proposed approach integrates spectral time discretization with neural network approximatio...An efficient data-driven numerical framework is developed for transient heat conduction analysis in thin-walled structures.The proposed approach integrates spectral time discretization with neural network approximation,forming a spectral-integrated neural network(SINN)scheme tailored for problems characterized by long-time evolution.Temporal derivatives are treated through a spectral integration strategy based on orthogonal polynomial expansions,which significantly alleviates stability constraints associated with conventional time-marching schemes.A fully connected neural network is employed to approximate the temperature-related variables,while governing equa-tions and boundary conditions are enforced through a physics-informed loss formulation.Numerical investigations demonstrate that the proposed method maintains high accuracy even when large time steps are adopted,where standard numerical solvers often suffer from instability or excessive computational cost.Moreover,the framework exhibits strong robustness for ultrathin configurations with extreme aspect ratios,achieving relative errors on the order of 10−5 or lower.These results indicate that the SINN framework provides a reliable and efficient alternative for transient thermal analysis of thin-walled structures under challenging computational conditions.展开更多
基金The National Natural Science Foundation of China(No.50378029)
文摘In order to investigate the leak detection strategy of a heating network,a space-based simulation mathematical model for the heating network under leakage conditions is built by graph theory.The pressure changes of all the nodes in the heating network are obtained from node leak and pipe leak conditions.Then,a leakage diagnosis system based on the back propagation（BP）neural network is established.This diagnosis system can predict the leakage pipe by collecting the pressure change data of the monitoring points,which can preliminary estimate the leak location.The usefulness of this system is proved by an example.The experimental results show that the forecast accuracy by this diagnosis system can reach 100%.
基金Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization(South China University of Technology)(2013A061401005)Research Fund(JMSWFW-2110-044)from Zhongshan Jiaming Electric Power Co.,Ltd.
文摘The determination of source-side extracted heating parameters is of great significance to the economic operation of cogeneration systems.This paper investigated the coupling performance of a cogeneration heating and power system multidimensionally based on the operating characteristics of the cogeneration units,the hydraulic and thermodynamic characteristics of the heating network,and the energy loads.Taking a steam network supported by a gas-steam combined cycle cogeneration system as the research case,the interaction effect among the source-side prime movers,the heating networks,and the terminal demand thermal parameters were investigated based on the designed values,the plant testing data,and the validated simulation.The operating maps of the gas-steam combined cycle cogeneration units were obtained using THERMOFLEX,and the minimum source-side steam parameters of the steam network were solved using an inverse solution procedure based on the hydro-thermodynamic coupling model.The cogeneration operating maps indicate that the available operating domain considerably narrows with the rise of the extraction steam pressure and flow rate.The heating network inverse solution demonstrates that the source-side steam pressure and temperature can be optimized from the originally designed 1.11 MPa and 238.8°C to 1.074 MPa and 191.15°C,respectively.Under the operating strategy with the minimum source-side heating parameters,the power peak regulation depth remarkably increases to 18.30%whereas the comprehensive thermal efficiency decreases.The operation under the minimum source-side heating steam parameters can be superior to the originally designed one in the economy at a higher price of the heating steam.At a fuel price of$0.38/kg and the power to fuel price of 0.18 kg/(kW·h),the critical price ratio of heating steam to fuel is 119.1 kg/t.The influence of the power-fuel price ratio on the economic deviation appears relatively weak.
基金supported by the State Key Research and Development Program,Special Gravity Wave(Grant No.2023YFC2206003)the Gansu Provincial Science and Technology Program Funding(Grant No.24JRRA499)+1 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2024QB219)the Lanzhou City Science and Technology Program Project(Grant No.2025-2-47)。
文摘Giant magnetoimpedance(GMI)sensors are increasingly employed in modern magnetic sensing technologies.However,improving the GMI performance of magnetic cores remains challenging due to intrinsic limitations in material properties and structural stability.In this work,we explore the use of Joule heating to enhance the GMI response of Fe_(20)Ni_(80)/Cu composite wires.By applying a current of 1.8 A for 10 min,notable improvements in magnetic domain uniformity and a reduction in domain spacing are observed.Under these conditions,GMI ratios reach 1870% in the non-diagonal mode and1147%in the diagonal mode,respectively,highlighting their potential for applications in high-precision weak magnetic field sensing.
基金financially supported by the National Natural Science Foundation of China(No.52103127)the Opening Project of the State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-10)Shaanxi Provincial Science and Technology Department(No.2025GH-YBXM-042).
文摘In this study,an architecture featuring a gradient conductive network structure and three-dimensional dual-continuous network structure is constructed in a carbon nanotubes/cellulose-boron nitride/poly(vinyl alcohol)(CNT/cellulose-BN/PVA)composite.Using cellulose aerogel as a template,CNT were incorporated into the cellulose template by vertically impregnating the CNT suspension.Following the impregnation of BN/PVA and high-pressure compression,three-dimensional dual-continuous network structure was successfully constructed in the CNT/cellulose-BN/PVA composite.The comprehensive performance of the composite,including electromagnetic interference(EMI)shielding and Joule heating performance,was investigated.The results indicate that the total EMI shielding effectiveness(SE)for the CNT/cellulose-BN/PVA composite reveals similar values for electromagnetic waves incident from different directions,but totally different shielding mechanisms.For the CNT/cellulose-BN/PVA composite with three impregnation cycles of CNT,the EMI SE values exceeded 39 dB for electromagnetic waves incident from both the high-and low-CNT-content sides.93%of the microwaves were reflected when electromagnetic waves were incident from the high-CNT-content side,while the reflection coefficient decreased to 0.44 for the transverse direction.In addition,the construction of the dual-continuous network structure enabled the composite to exhibit both excellent electrical conductivity and good thermal conductivity simultaneously,endowing the material with good Joule heating performance.CNT/cellulose-BN/PVA composite films have significant potential for application as EMI shielding materials in extremely cold weather.
基金supported by Integrated Distribution Network Planning and Operational Enhancement Using Flexibility Domains Under Deep Human-Vehicle-Charger-Road-Grid Coupling(U22B20105).
文摘Thermal storage electric heating(TSEH),as a prevalent variable load resource,offers significant potential for enhancing system flexibility when aggregated into a cluster.To address the uncertainties of renewable energy and load forecasting in active distribution networks(ADN),this paper proposes a multi-timescale coordinated optimal dispatch strategy that incorporates TSEH clusters.It utilizes the thermal storage characteristics and short-term regulation capabilities of TSEH,along with the rapid and gradual response characteristics of resources in active distribution grids,to develop a coordinated optimization dispatch mechanism for day-ahead,intraday,and real-time stages.It provides a coordinated optimized dispatch technique across several timescales for active distribution grids,taking into account the integration of TSEH clusters.The proposed method is validated on a modified IEEE 33-node system.Simulation results demonstrate that the participation of TSEH in collaborative optimization significantly reduces the total system operating cost by 8.71%compared to the scenario without TSEH.This cost reduction is attributed to a 10.84%decrease in interaction costs with the main grid and a 47.41%reduction in network loss costs,validating effective peak shaving and valley filling.The multi-timescale framework further enhances economic efficiency,with overall operating costs progressively decreasing by 3.91%(intraday)and 4.59%(real-time),and interaction costs further reduced by 5.34%and 9.25%,respectively.Moreover,the approach enhances system stability by effectively suppressing node voltage fluctuations and ensuring all voltages remain within safe operating limits during real-time operation.Therefore,the proposed approach achieves rational coordination of diverse resources,significantly improving the economic efficiency and stability of ADNs.
基金supported by the Science and Technology Project of State Grid“Research and Application of Wide Area Multi energy Storage Collaborative Optimization and Control Technology in Provincial Power Grid”.
文摘The integrated electricity-heat-hydrogen system(IEHHS)facilitates the efficient utilization of multiple energy sources,while the operational flexibility of IEHHS is hindered by the high heat inertia of alkaline electrolyzers(AELs)and the variations of renewable energy.In this paper,we propose a robust scheduling of IEHHS considering the bidirectional heat exchange(BHE)between AELs and district heating networks(DHNs).First,we propose an IEHHS model to coordinate the operations of AELs,active distribution networks(ADNs),and DHNs.In particular,we propose a BHE that not only enables the waste heat recovery for district heating but also accelerates the thermal dynamics in AELs.Then,we formulate a two-stage robust optimization(RO)problem for the IEHHS operation to consider the variability of renewable energy in ADNs.We propose a new solution method,i.e.,multi-affine decision rule(MADR),to solve the two-stage RO problem with less conservatism.The simulation results show that the operational flexibility of IEHHS with BHE is remarkably improved compared with that only with unidirectional heat exchange(UHE).Compared with the traditional affine decision rule(ADR),the MADR effectively reduces the IEHHS operating costs while guaranteeing the reliability of scheduling strategies.
文摘The aim of this paper was to characterize through experiment the moisture and temperature kinetic behavior of Eucalyptus gomphocephala wood samples using microwave heating(MWH)in two scenarios:intermittently and continuously.The mechanical properties and surface appearance of the heated samples were also investigated.Continuous and intermittent microwave drying kinetic experiments were conducted at a frequency of 2.45 GHz using a microwave laboratory oven at 300,500,and 1000 watts.Drying rate curves indicated three distinct phases of MWH.Increasing the microwave power with a shorter drying time led to rapid increases in internal temperature and water evaporation rates of the heated samples.Mechanical results indicated that samples heated under continuous MW(Microwave)power at 300 watts had a modulus of rupture(MOR)and modulus of elasticity(MOE)in three static bending tests higher than 29%and 36%,respectively,than samples heated at 1000 watts.Intermittent microwave heating(IMWH)of samples at 300 and 1000 watts produced the highest MOR and MOE values of 31%and 51%,respectively,unlike those heated under continuous microwave heating(CMWH).External qualitative observation showed that samples heated at high microwave power had severe surface checks.These defects were missing when using IMWH.An analysis of variance(ANOVA)showed that mechanical properties were linked to both microwave power level and the heating scenario,except for MOR in axial compression under CMWH.
基金supported by the National Natural Science Foundation of China(Nos.22005277,52474256 and 52074247)the Natural Science Foundation of Hubei Province(No.2024AFB662)+1 种基金the Young Top-notch Talent Cultivation Program of Hubei Province,Opening Foundation of State Key Laboratory of Organic-Inorganic Composites,Beijing University of Chemical Technology(No.oic-202401012)the Fundamental Research Funds for National Universities,China University of Geosciences(No.2024XLA93).
文摘With the continuous advancement of electronic devices,flexible thin films with both thermal manage-ment functions and excellent electromagnetic interference(EMI)shielding properties have received much attention.Hence,inspired by Janus,a CNF/MXene/ZnFe2O4@PANI composite film with an asymmetric gradient alternating structure was successfully prepared by adjusting the filler content of the conduc-tive and magnetic layers using a vacuum-assisted filtration method.Benefiting from the magnetic reso-nance and hysteresis loss of ZnFe2O4@PANI,conductive loss and dipole polarization of MXene,as well as the exclusive"absorption-reflection-reabsorption"shielding feature in the alternating multilayered films,CM&CZFP-4 G film has superior EMI shielding performance,with an EMI SE of up to 45.75 dB and shield-ing effectiveness of 99.99%.Surprisingly,the composite film maintains reliable EMI shielding properties even after prolonged erosion in harsh environments such as high/low temperatures,high humidity,acids and alkalis.Furthermore,the CM&CZFP-4 G responded quickly within about 50 s and reached a maximum steady-state temperature of 235.8℃ at an applied voltage of 9.0 V,indicating the obtained film acquired outstanding and controllable Joule heating performance.This result was attributed to the homogeneous dispersion of MXene to build up a conductive network and endow the CNF/MXene with high conduc-tivity.Meanwhile,the fire resistance of CM&CZFP-4 G was significantly improved compared to pure CNF,which guaranteed fire safety during its application.Additionally,contributed by long fiber entanglement of CNF,extensive hydrogen-bonding interactions and multilayer structural design,the CM&CZFP-4 G film exhibits excellent mechanical characteristics,with the tensile strength and fracture strain of 27.74 MPa and 6.21%,separately.This work offers a creative avenue to prepare multifunctional composite films with electromagnetic shielding and Joule heating for various application environments.
基金funded by Universiti Teknikal Malaysia Melaka,through Fakulti Teknologi dan Kejuruteraan Mekanikal(FTKM)’s publication fund-K23003.
文摘This study investigates the heat transfer and flow dynamics of a ternary hybrid nanofluid comprising alumina,copper,and silica/titania nanoparticles dispersed in water.The analysis considers the effects of suction,magnetic field,and Joule heating over a permeable shrinking disk.Amathematicalmodel is developed and converted to a systemof differential equations using similarity transformation which then,solved numerically using the bvp4c solver in Matlab software.The study introduces a novel comparative analysis of alumina-copper-silica and alumina-coppertitania nanofluids,revealing distinct thermal conductivity behaviors and identifying critical suction values necessary for flow stabilization.Dual solutions are found within a specific range of parameters such that the minimum required suction values for flow stability,with S_(c)=1.2457 for alumina-copper-silica/water and S_(c)=1.2351 for alumina-coppertitania/water.The results indicate that increasing suction by 1%enhances the skin friction coefficient by up to 4.17%and improves heat transfer efficiency by approximately 1%,highlighting its crucial role in stabilizing the opposing flow induced by the shrinking disk.Additionally,the inclusion of 1%silica nanoparticles reduces both skin friction and heat transfer rate by approximately 0.28%and 0.85%,respectively,while 1%titania concentration increases skin friction by 3.02%but results in a slight heat transfer loss of up to 0.61%.These findings confirm the superior thermal performance of alumina-copper-titania/water,making it a promising candidate for enhanced cooling systems,energy-efficient heat exchangers,and industrial thermal management applications.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(No.2023B1515040013).
文摘The vigorous development of modern electronic communication demands multi-functional materials with exceptional electromagnetic interference(EMI)shielding.However,constructing lightweight and highly efficient metal-free carbon-based EMI shielding materials remains a huge challenge,particularly with robust EMI responses across a broadband frequency.Herein,a broadband(8-27 GHz)and strong EMI shielding response nitrogen-doped carbon plate(NCP)is constructed by a pressing and two-step pyroly-sis process.The layered stacking structure and N-doping impart extraordinary EMI shielding performance to the carbon plate,achieving EMI shielding effectiveness values of 82.60,95.44,and 104.12 dB in the X band,Ku band,and K band,respectively.Notably,the overall thickness of NCP was<1 mm.Moreover,the NCP exhibits remarkable joule heating performance with a low driving voltage(≤3 V)and a fast elec-trothermal response.This work enables the potential for the development of metal-free carbon materials with lightweight,highly efficient and broadband-strong EMI shielding performance.
基金funded by the National Key R&D Program of China(No.2021YFB3702404)the National Natural Science Foundation of China(Nos.52201101 and 52274372)+1 种基金the Major Program Funding of Cisri(No.21T62450ZD)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-22-013A1 and FRF-TP-22-015A1).
文摘The cold-rolled quenching and partitioning(Q&P)steel with an initial microstructure of deformed ferrite and pearlite was studied.The microstructural evolution under various heating rates of 1.78,50,and 300℃/s was investigated using microstructural characterization and theoretical modeling.At the same time,the characteristics of recrystallization and austenite formation kinetics were decoupled by examining recrystallized ferrite and deformed ferrite as initial conditions.The findings revealed that the austenite formation during continuous heating can be simplified into two stages:(i)the early nucleation-dominated formation stage and(ii)the later grain growth-dominated stage,resulting in the development of a modified two-stage model based on Johnson-Mehl-Avrami-Kolmogorov.Further experiments confirmed that when the austenite volume fraction exceeded approximately 5% at a heating rate of 1.78℃/s,ferrite recrystallization was suppressed.In consequence,a mixed model including recrystallization kinetics was employed to couple the austenite formation occurring in deformed ferrite and recrystallized ferrite,thereby describing the austenite formation kinetics affected by recrystallization.Precise predictions of non-isothermal austenite formation kinetics in cold-rolled Q&P steel were achieved during slow and ultrafast heating processes by integrating the suppression effect into the model for austenite formation.
基金supported by a Korea University Grantby the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)with Grant Number 2022R1A2C1003381。
文摘Alginate-based magnetic micro/millirobots have demonstrated significant potential for biomedical applications due to their flexible structures and capacity to carry various types of cargo,such as cells,enabling targeted therapy to specific diseased regions within the body.Their active therapy is typically achieved through magnetic actuation and magnetic heating,while monitored by medical imaging methods like CT which pose additional risks due to radiation exposure.In the last decades,a novel imaging method for superparamagnetic materials,known as magnetic particle imaging(MPI),has been under active development,offering not only positional tracking but also the ability to measure concentration and temperature.Here,we report the world's first MPI-traceable magnetic hydrogel robots,which employ a combination of iron oxide nanoflowers,NdFeB powder,and calcium alginate.Unlike previous magnetic alginate robots composed of a single magnetic material,the synergistic combination of NdFeB and nanoflowers enables these robots to exhibit triple magnetic functionalities:magnetic heating,locomotion at low magnetic fields,and tracking,all of which can be controlled using a single all-in-one electromagnetic coil system.The effects of various magnetization fields,as well as different concentrations of NdFeB and nanoflowers on the robots'magnetic properties were analyzed.This led to the development of three types of triple-function robots(spiral,droplet,and hybrid),with experimental results demonstrating biocompatibility,a magnetic heating temperature increase of over 10℃in plasma fluid under a magnetic field of 13 kA·m^(-1)at 200 kHz,locomotion speeds of up to 25 mm·s^(-1)in fields below 2 mT,and an MPI tracking error of 2.8 mm with a selection field of 0.4 mT·mm^(-1).Additionally,the robots'capacity for localized thermal therapy and selectively targeted cell delivery,as well as their locomotion within a medical phantom against a maximum flow of 50 mm·s^(-1)were demonstrated.
基金National Natural Science Foundation of China(11875039)Shanxi Scholarship Council of China(2023-033)+2 种基金Fundamental Research Program of Shanxi Province(202303021221071)China Baowu Low Carbon Metallurgical Innovation Foundation(2022)2023 Anhui Major Industrial Innovation Plan Project。
文摘The in-flight heating process of cerium dioxide(CeO_(2))powders was investigated through experiments and numerical simulations.In the experiment,CeO_(2)powder(average size of 30μm)was injected into radio-frequency(RF)argon plasma,and the temperatures were measured using a DPV-2000 monitor.A model combining the electromagnetism,thermal flow,and heat transfer characteristics of powder during in-flight heating in argon plasma was proposed.The melting processes of CeO_(2)powders of different diameters,with and without thermal resistance effect,were investigated.Results show that the heating process of CeO_(2)powder particles consists of three main stages,one of which is relevant to a dimensionless parameter known as the Biot number.When the Biot value≥0.1,thermal resistance increases significantly,especially for the larger powders.The predicted temperature of the particles at the outlet(1800–2880 K)is in good agreement with the experimental result.
基金supported by the Tianjin Education Commission Research Program Project(No.2024KJ105)。
文摘The buoyancy-induced flow constitutes a core scientific issue for thermal management of electronic devices and thermal design of energy systems,where accurate characterization of flow and heat transfer is essential to improve thermal efficiency.In this work,buoyancy-induced flow above two heating elements flush-mounted at the bottom of a square enclosure containing air is numerically investigated over a range of Rayleigh numbers(0<Ra≤1.5×10^(8)),with a focus on equal and unequal heat flux conditions under a constraint of constant total thermal energy input.Distinct flow transitions are observed in both cases,leading to the identification of three flow regimes:Steady,periodic unsteady,and chaotic unsteady.Two types of periodic flows are distinguished,in which the first is a periodic flow dominated by a fundamental frequency(FF)and its integer-multiple frequencies(INTMF),while the second is a more complex periodic flow featuring FF,INTMF,and their sub-harmonics.The transitions between these regimes are affected by the relative heat flux of the two heaters.When the heat flux of the two heaters is unequal,the range of Rayleigh numbers corresponding to periodic flow is suppressed.It is also found that the time-averaged maximum temperature of the strong heater increases more rapidly with Ra,while that of the weak heater increases more slowly,reflecting the interaction between buoyancy-driven flow dynamics and asymmetric heat input.Analysis of the time-averaged Nusselt number demonstrates that heat dissipation from the isothermal walls remains roughly equivalent,even when the heat flux of the two heaters differs by a factor of two.These findings highlight the critical roles of Rayleigh number,the number of heaters,and the heat flux ratio of the heaters in determining heat transfer and flow characteristics for buoyancy-driven convection systems,providing important theoretical support and design references for engineering scenarios such as electronic devices and design of new energy systems.
基金supported by the USDA National Institute of Food and Agriculture,Hatch project 7009323.
文摘Oat milk has gained widespread consumer acceptance for its creamy texture,β-glucan content,and environmental sustainability.However,its relatively low protein content(typically 2-3 g/serving)presents a nutritional limitation,largely due to poor protein solubility.This study investigated how processing conditions influence protein content and functional stability in oat-based systems by applying two treatments:(1)α-amylase enzymatic hydrolysis,and(2)pH-shifting(from pH 7 to 12 and back)with mild heating(50℃for 10 or 30 min).Oat protein solutions were formulated from two sources:oat flour(OF)and oat protein isolate(OPI).Results suggests that α-amylase pretreatment effectively reduced starch-driven viscosity in OF,facilitating better sample handling and centrifugation.Following pH-shifting and heat treatment,both OF and OPI solutions showed significantly improved protein solubility,with protein content increased from 2.0 to~6.5 g/serving.These changes were accompanied by reduced precipitation,smaller particle sizes,and more negative zeta potential values,indicating enhanced colloidal stability.SDS-PAGE analysis revealed the presence of low-molecular-weight protein fractions,supporting increased solubilization.Fluorescence microscopy confirmed the formation of smaller,more uniformly dispersed particles in treated samples compared to controls.However,noticeable darkening or browning occurred under high-pH heating,indicating potential challenges in color control.The findings provide useful information for future industrial applications and product innovation in the plant-based beverage sector.
基金supported by the Slovenian Research Agency(research project NC-0001-Analysis of nuclear heating in a reactor,research core funding Reactor physics No.P2-0073,infrastructure program I0-0005)。
文摘Nuclear heating plays an important aspect in design and deployment of both fission and fusion reactors and experimental devices in terms of cooling requirements. Two experimental campaigns in the framework of a collaboration project between the French Atomic and Alternative Energy Commission(CEA) and Jožef Stefan Institute(JSI), Slovenia, have been performed at the JSI TRIGA reactor for the experimental assessment of nuclear heating in fission and fusion-relevant materials by the differential calorimetry technique, based on the CALMOS and CARMEN differential calorimeters, previously developed at CEA. The results of the first campaign performed at reactor powers between 100 and 250 kW have already been reported, highlighting some measurement difficulties. Therefore, the second campaign was performed at a lower reactor power of 30 kW to overcome these issues. Moreover, a computational analysis of the experiments was performed using the JSIR2S code package to calculate the nuclear heating levels. Both experiments and their reproduction by simulations are described in detail. We present a comparison of the previously reported measured nuclear heating values of the first campaign with the computational results, with consistent underestimation by simulations by 8–35%. We report the experimental and computational results for the second experimental campaign performed at a reactor power of 30 kW. The simulated heating values were in agreement with the measurements within the measured heating uncertainty, with simulated heating 2.7–11.3% lower than the experimental values.
文摘This study investigates the enhancement of convective heat transfer in a serpentine pipe using ferrofluid flow influenced by dual non-uniform magnetic sources.The primary objective is to improve thermal performance in compact cooling systems,such as those used in heat exchangers.A two-dimensional,steady-state Computational Fluid Dynamic(CFD)model is developed in ANSYS Fluent to simulate the behavior of an incompressible ferrofluid under applied constant heat flux and magnetic fields.The magnetic force is modeled using the Kelvin force,which acts on magnetized nanoparticles in response to spatially varying electromagnetic fields generated by two strategically positioned current-carrying wires.The effects of magnetic field strength,quantified by the magnetic number(Mn),on flow behavior and temperature distribution are thoroughly analyzed.The results indicate that increasing Mn leads to higher Nusselt numbers,demonstrating enhanced convective heat transfer.Secondary vortices induced by magnetic forcing improve fluid mixing,particularly in curved regions of the pipe.A mesh-independence study and model validation with benchmark data support the reliability of the numerical framework.This work highlights the potential of magnetic-field-assisted thermal control in energy-efficient cooling applications and provides a foundation for the further development of advanced ferrofluid-based heat transfer systems.
基金supported by the National Natural Science Foundation of China(52276196)the Foundation of State Key Laboratory of Coal Combustion(FSKLCCA2508)the High-level Talent Foundation of Anhui Agricultural University(rc412307).
文摘Flash Joule heating(FJH),as a high-efficiency and low-energy consumption technology for advanced materials synthesis,has shown significant potential in the synthesis of graphene and other functional carbon materials.Based on the Joule effect,the solid carbon sources can be rapidly heated to ultra-high temperatures(>3000 K)through instantaneous high-energy current pulses during FJH,thus driving the rapid rearrangement and graphitization of carbon atoms.This technology demonstrates numerous advantages,such as solvent-and catalyst-free features,high energy conversion efficiency,and a short process cycle.In this review,we have systematically summarized the technology principle and equipment design for FJH,as well as its raw materials selection and pretreatment strategies.The research progress in the FJH synthesis of flash graphene,carbon nanotubes,graphene fibers,and anode hard carbon,as well as its by-products,is also presented.FJH can precisely optimize the microstructures of carbon materials(e.g.,interlayer spacing of turbostratic graphene,defect concentration,and heteroatom doping)by regulating its operation parameters like flash voltage and flash time,thereby enhancing their performances in various applications,such as composite reinforcement,metal-ion battery electrodes,supercapacitors,and electrocatalysts.However,this technology is still challenged by low process yield,macroscopic material uniformity,and green power supply system construction.More research efforts are also required to promote the transition of FJH from laboratory to industrial-scale applications,thus providing innovative solutions for advanced carbon materials manufacturing and waste management toward carbon neutrality.
基金supported by the National Natural Science Foundation of China(12401279,12371219)the Academic and Technical Leaders Training Plan of Jiangxi Province(20212BCJ23027).
文摘This paper is concerned with an initial boundary value problem for the planar magnetohydrodynamic compressible flow with temperature dependent heat conductivity in a half-line.In particular,the transverse magnetic field is assumed to satisfy the Neumann boundary condition,which was first investigated by Kazhikhov in 1987.We establish the global existence of the unique strong solutions to the MHD equations without any smallness conditions on the initial data.More precisely,our result can be regarded as a natural generalization of Kazhikov’s result for applying the constant heat-conductivity in bounded domains to the degenerate case in unbounded domains.
基金supported by the National Natural Science Foundation of China(Nos.12422207 and 12372199).
文摘An efficient data-driven numerical framework is developed for transient heat conduction analysis in thin-walled structures.The proposed approach integrates spectral time discretization with neural network approximation,forming a spectral-integrated neural network(SINN)scheme tailored for problems characterized by long-time evolution.Temporal derivatives are treated through a spectral integration strategy based on orthogonal polynomial expansions,which significantly alleviates stability constraints associated with conventional time-marching schemes.A fully connected neural network is employed to approximate the temperature-related variables,while governing equa-tions and boundary conditions are enforced through a physics-informed loss formulation.Numerical investigations demonstrate that the proposed method maintains high accuracy even when large time steps are adopted,where standard numerical solvers often suffer from instability or excessive computational cost.Moreover,the framework exhibits strong robustness for ultrathin configurations with extreme aspect ratios,achieving relative errors on the order of 10−5 or lower.These results indicate that the SINN framework provides a reliable and efficient alternative for transient thermal analysis of thin-walled structures under challenging computational conditions.
