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
In the application of clean energy heating,the development of a low-carbon winter heat supply in severe cold regions of China is hindered by the stability of heat sources.To ensure the smooth transformation of traditi...In the application of clean energy heating,the development of a low-carbon winter heat supply in severe cold regions of China is hindered by the stability of heat sources.To ensure the smooth transformation of traditional energy to clean energy heating modes,the feasibility of a heating system coupling traditional and clean energies was studied using the heating system of an office building in a cold region of China as the research object.The air-source heat pump(ASHP)heating system used in the office building in this study was field-tested.The problems existing in the heating system were analysed using testing data combined with the existing conditions of the building.Solar-air source heat pump coupled heating system based on heat grid(NH-SASHP)was proposed,and the system model was established using TRNSYS software.The operation effect of the NH-SASHP coupling system was analysed,and the control strategy of the coupling system was optimized.The results showed that NH-SASHP system possessed certain advantages over the ASHP system during the heating season,and the energy saving rate is 50.79%compared with the ASHP system.Under the most unfavourable working conditions in the middle of severe cold,the indoor temperature compliance rate was 100%.The average coefficient of performance of the heat pump system(COPsys)of NH-SASHP system and ASHP system were 6.27 and 3.55,respectively.The operating cost of the NH-SASHP system is approximately 72.3%of the ASHP system.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
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
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
With the widespread application of combined heat and power(CHP)units,the economic dispatch of integrated electric and district heating systems(IEHSs)has drawn increasing attention.Because the electric power system(EPS...With the widespread application of combined heat and power(CHP)units,the economic dispatch of integrated electric and district heating systems(IEHSs)has drawn increasing attention.Because the electric power system(EPS)and district heating system(DHS)are generally managed separately,the decentralized dispatch pattern is preferable for the IEHS dispatch problem.However,many common decentralized methods suffer from the drawbacks of slow and local convergence.Moreover,the uncertainties of renewable generation cannot be ignored in a decentralized pattern.Additionally,the most commonly used individual chance constraints in distributionally robust optimization cannot consider safety constraints simultaneously,so the safe operation of an IEHS cannot be guaranteed.Thus,distributionally robust joint chance constraints and robust constraints are jointly introduced into the IEHS dispatch problem in this paper to obtain a stronger safety guarantee,and a method combined with Bonferroni and conditional value at risk(CVaR)approximation is presented to transform the original model into a quadratic program.Additionally,a dynamic boundary response(DBR)-based distributed algorithm based on multiparametric programming is proposed for a fast solution.Case studies showcase the necessity of using mixed distributionally robust joint chance constraints and robust constraints,as well as the effectiveness of the DBR algorithm.展开更多
Intermittent heating is an energy-saving heating mode,which can save energy in terms of time,and thus is worth promoting,particularly in residential heating scenarios.Conventional radiant heating terminals,that is flo...Intermittent heating is an energy-saving heating mode,which can save energy in terms of time,and thus is worth promoting,particularly in residential heating scenarios.Conventional radiant heating terminals,that is floor heating,and convective heating terminals,that is fan coils,cannot achieve both intermittent and thermal comfort during intermittent heating.Therefore,this study proposes a switchable convective-radiant heating regulation method for floor heating and fan coils to achieve a comfortable indoor environment with high thermal response speed.Furthermore,a novel combined radiant-convective heating terminal was proposed for a reliable and effective solution.Results showed that the proposed switchable method could increase both intermittence and thermal comfort.In addition,the heating terminal showed better heating performance than the combination of two conventional terminals at the key points of heating capacity,flexibility,and thermal response.It could initially heat up a typical residential space within 20-40 min and then stabilize the room temperature in a comfortable range of 18-22℃,showing great potential for intermittent heating in room-scale heating conditions.This study provides a reference technique for intermittent heating with reduced system complexity and precise environmental control.展开更多
Lithium-ion batteries(LIBs)are critical for the rapid growth of electric vehicles(EVs),but their inherent lifespan leads to numerous retirements and resource challenges.The efficacy of conventional recycling technique...Lithium-ion batteries(LIBs)are critical for the rapid growth of electric vehicles(EVs),but their inherent lifespan leads to numerous retirements and resource challenges.The efficacy of conventional recycling techniques is increasingly compromised by their high energy consumption and secondary pollution,rendering them less responsive to greener and more sustainable requirement of rapid development.Thus,the direct recycling process emerged and was considered as a more expedient and convenient method of recycling compared to the conventional recycling modes that are currently in study.However,due to the reliance on the indispensable sintering process,direct recycling still faces considerable challenges,motivating researchers to explore faster,greener,and more cost-effective strategies for LIBs recycling,Inspiringly,Joule heating recycling(JHR),an emerging technique,offers rapid,efficient impurity removal and material regeneration with minimal environmental impact,addressing limitations of existing methods.This method reduces the time for direct recycling of spent LIBs by a factor of at least three orders of magnitude and exhibits significant potential for future industrial production.Unfortunately,due to the lack of systematic organization and reporting,this next generation approach to direct recycling of spent LIBs has not yet gained much interest.To facilitate a more profound comprehension of rising flash recycling strategy,in this study,JHR is distinguished into two distinctive implementation pathways(including flash Joule heating and carbon thermal shock),designed to accommodate varying pretreatment stages and diverse spent LIBs materials.Subsequently,the advantages of the recently developed JHR of spent LIBs in terms of material performance,environmental friendliness,and economic viability are discussed in detail.Ultimately,with the goal of achieving more attractive society effects,the future direction of JHR of spent LIBs and its potential for practical application are proposed and envisaged.展开更多
Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency...Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency of FRAM,which depends only on friction to generate heat,is low,and the thermal-accumulation effect of the deposition process must be addressed.An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling(PC-FRAM)is devised in this study,and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head.Additionally,2195-T87 Al-Li alloy is used as the feed material,and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated.The results show that water cooling significantly improves heat accumulation during the deposition process.The cooling rate increases by 11.7 times,and the high-temperature residence time decreases by more than 50%.The grain size of the PC-FRAM sample is the smallest,i.e.,3.77±1.03μm,its dislocation density is the highest,and the number density of precipitates is the highest,the size of precipitates is the smallest,which shows the best precipitation-strengthening effect.The hardness test results are consistent with the precipitation distribution.The ultimate tensile strength,yield strength and elongation of the PC-FRAM samples are the highest(351±15.6 MPa,251.3±15.8 MPa and 16.25%±1.25%,respectively)among the samples investigated.The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples.The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.展开更多
Self-regulating heating and self-powered flexibility are pivotal for future wearable devices.However,the low energy-conversion rate of wearable devices at low temperatures limits their application in plateaus and othe...Self-regulating heating and self-powered flexibility are pivotal for future wearable devices.However,the low energy-conversion rate of wearable devices at low temperatures limits their application in plateaus and other environments.This study introduces an azopolymer with remarkable semicrystallinity and reversible photoinduced solid-liquid transition ability that is obtained through copolymerization of azoben-zene(Azo)monomers and styrene.A composite of one such copolymer with an Azo:styrene molar ratio of 9:1(copolymer is denoted as PAzo9:1-co-polystyrene(PS))and nylon fabrics(NFs)is prepared(composite is denoted as PAzo9:1-co-PS@NF).PAzo9:1-co-PS@NF exhibits hydrophobicity and high wear resistance.Moreover,it shows good responsiveness(0.624 s^(−1))during isomerization under solid ultraviolet(UV)light(365 nm)with an energy density of 70.6 kJ kg^(−1).In addition,the open-circuit voltage,short-circuit current and quantity values of PAzo9:1-co-PS@NF exhibit small variations in a temperature range of−20℃ to 25℃ and remain at 170 V,5 μA,and 62 nC,respectively.Notably,the involved NFs were cut and sewn into gloves to be worn on a human hand model.When the model was exposed to both UV radiation and friction,the temperature of the finger coated with PAzo9:1-co-PS was approximately 6.0°C higher than that of the other parts.Therefore,developing triboelectric nanogenerators based on the in situ photothermal cycles of Azo in wearable devices is important to develop low-temperature self-regulating heating and self-powered flexible devices for extreme environments.展开更多
Coal dependence and inefficient decentralized heating have significantly increased China’s energy consumption for winter heating,increasing air pollution and exacerbating the greenhouse effect.In 2017,China implement...Coal dependence and inefficient decentralized heating have significantly increased China’s energy consumption for winter heating,increasing air pollution and exacerbating the greenhouse effect.In 2017,China implemented the Pilot Policy on Clean Winter Heating in Northern China,aiming to achieve high central heating coverage and cleaner energy consumption.Studying the effects of this policy can help promote its implementation and serve as a reference for effective adjustment of the contents in the future.However,few studies have investigated this policy and its carbon reduction effects,and most focus on the provincial or city levels.Therefore,this paper considers the policy’s influence on air pollution and carbon emissions at the county level to provide a precise and comprehensive assessment of the policy effects.We use panel data from 1290 counties in 15 provinces in Northern China from 2014 to 2021,applying a multiperiod difference-in-differences model to quantify the impact of the policy on carbon emissions and air quality in the pilot area.We then conduct a series of tests to demonstrate the robustness of the results and analyze the mechanisms of the policy effects from two perspectives,namely,central heating and natural gas use,through a mediating effect model.Finally,we examine the heterogeneity of policy effects between counties based on geographic location and per capita income levels of rural residents through a moderating effect model.The results reveal that the policy significantly reduces air pollution and carbon emissions in the pilot area by increasing the central heating area and natural gas use.Compared with the central and western regions in the north and areas with low-income rural residents,the policy effects in the eastern regions in the north and areas with high-income rural residents are more pronounced.展开更多
Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the...Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the Zener factor,the diameter and number density of precipitates of interrupted testing samples were statistically calculated.The effect of precipitate ripening on the Goss texture and magnetic property was investigated.Data indicated that the trend of Zener factor was similar under different heating rates,first increasing and then decreasing,and that the precipitate maturing was greatly inhibited as the heating rate increased.Secondary recrystallization was developed at the temperature of 1010℃when a heating rate of 5℃/h was used,resulting in Goss,Brass and{110}<227>oriented grains growing abnormally and a magnetic induction intensity of 1.90T.Furthermore,increasing the heating rate to 20℃/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture.However,when the heating rate was extremely fast,such as 40℃/h,poor secondary recrystallization was developed with many island grains,corresponding to a decrease in magnetic induction intensity to 1.87 T.At a suitable heating rate of 20℃/h,the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1020℃were found among the experimental variables in this study.The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates,leading to the deviation and dispersion of Goss texture,thereby reducing the magnetic properties.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
Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in buildi...Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems,which are essential for decision-making.Therefore,this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems.Based on the geological parameters of Xi’an,China and commonly used borehole heat exchanger structures,numerical simulationmethods are employed to analyze performance and economic efficiency.The results indicate that increasing the spacing between shallow borehole heat exchangers can effectively reduce thermal interference between the pipes and improve heat extraction performance.As the flow rate increases,the outlet water temperature ranges from 279.3 to 279.7 K,with heat extraction power varying between 595 and 609 W.For medium-deep borehole heat exchangers,performance predictions show that a higher flow rate results in greater heat extraction power.However,when the flow rate exceeds 30 m^(3)/h,further increases in flow rate have only a minor effect on enhancing heat extraction power.Additionally,the economic analysis reveals that the payback period for shallow geothermal heating systems ranges from 10 to 11 years,while for medium-deep geothermal heating systems,it varies more widely from 3 to 25 years.Therefore,the payback period for medium-deep geothermal heating systems is more significantly influenced by operational and installation parameters,and optimizing these parameters can considerably shorten the payback period.The results of this study are expected to provide valuable insights into the efficient and cost-effective utilization of geothermal energy for building heating.展开更多
The development of efficient and clean heating technologies is crucial for reducing carbon emissions in regions with severe cold regions.This research designs a novel two-stage phase change heat storage coupled solar-...The development of efficient and clean heating technologies is crucial for reducing carbon emissions in regions with severe cold regions.This research designs a novel two-stage phase change heat storage coupled solar-air source heat pump heating system structure that is specifically designed for such regions.The two-stage heat storage device in this heating system expands the storage temperature range of solar heat.The utilization of the two-stage heat storage device not onlymakes up for the instability of the solar heating system,but can also directlymeet the building heating temperature,and can reduce the influence of low-temperature outdoor environments in severe cold regions on the heating performance of the air source heat pump by using solar energy.Therefore,the two-stage phase change heat storage coupled to the solar energy-air source heat pump heating system effectively improves the utilization rate of solar energy.A numerical model of the system components and their integration was developed using TRNSYS software in this study,and various performance aspects of the system were simulated and analyzed.The simulation results demonstrated that the two-stage heat storage device can effectively store solar energy,enabling its hierarchical utilization.The low-temperature solar energy stored by the two-stage phase change heat storage device enhances the coefficient of performance of the air source heat pump by 11.1%in severe cold conditions.Using the Hooke-Jeeves optimization method,the annual cost and carbon emissions are taken as optimization objectives,with the optimized solar heat supply accounting for 52.5%.This study offers valuable insights into operational strategies and site selection for engineering applications,providing a solid theoretical foundation for the widespread implementation of this system in severe cold regions.展开更多
The demand for flexible electric heating devices has increased due to technology advancement and improved living standards.These devices have various applications including personal thermal management,hyperthermia,def...The demand for flexible electric heating devices has increased due to technology advancement and improved living standards.These devices have various applications including personal thermal management,hyperthermia,defrosting,agricultural heating film,and oil-water separation.Joule heat,generated by electric currents,is commonly used in electrical appliances.To incorporate Joule heating into flexible electronics,new materials with excellent mechanical properties are necessary.Traditional polymers,used as reinforcements,limit the continuity of conductive networks in composites.Therefore,there is a need to develop flexible Joule thermal composite materials with enhanced mechanical strength and conductivity.Cellulose,a widely available renewable resource,is attracting attention for its excellent mechanical properties.It can be used as a dispersant and reinforcing agent for conductive fillers in cellulose-based composites,creating highly conductive networks.Various forms of cellulose,such as wood,nanocellulose,pulp fiber,bacterial cellulose,cellulose paper,textile clothing,and aramid fiber,have been utilized to achieve high-performance Joule thermal composites.Researchers have achieved excellent mechanical properties and developed efficient electric heating devices by designing cellulose-based composites with different structures.The scalable production methods enable large-scale application of cellulose-based devices,each with unique advantages in 1D,2D,and 3D structures.This review summarizes recent advancements in cellulose-based Joule thermal composites,providing insights into different structural devices,and discussing prospects and challenges in the field.展开更多
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.
文摘In the application of clean energy heating,the development of a low-carbon winter heat supply in severe cold regions of China is hindered by the stability of heat sources.To ensure the smooth transformation of traditional energy to clean energy heating modes,the feasibility of a heating system coupling traditional and clean energies was studied using the heating system of an office building in a cold region of China as the research object.The air-source heat pump(ASHP)heating system used in the office building in this study was field-tested.The problems existing in the heating system were analysed using testing data combined with the existing conditions of the building.Solar-air source heat pump coupled heating system based on heat grid(NH-SASHP)was proposed,and the system model was established using TRNSYS software.The operation effect of the NH-SASHP coupling system was analysed,and the control strategy of the coupling system was optimized.The results showed that NH-SASHP system possessed certain advantages over the ASHP system during the heating season,and the energy saving rate is 50.79%compared with the ASHP system.Under the most unfavourable working conditions in the middle of severe cold,the indoor temperature compliance rate was 100%.The average coefficient of performance of the heat pump system(COPsys)of NH-SASHP system and ASHP system were 6.27 and 3.55,respectively.The operating cost of the NH-SASHP system is approximately 72.3%of the ASHP system.
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.
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 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 National Natural Science Foundation of China(52377107,52007105)and the Taishan Scholars Program.
文摘With the widespread application of combined heat and power(CHP)units,the economic dispatch of integrated electric and district heating systems(IEHSs)has drawn increasing attention.Because the electric power system(EPS)and district heating system(DHS)are generally managed separately,the decentralized dispatch pattern is preferable for the IEHS dispatch problem.However,many common decentralized methods suffer from the drawbacks of slow and local convergence.Moreover,the uncertainties of renewable generation cannot be ignored in a decentralized pattern.Additionally,the most commonly used individual chance constraints in distributionally robust optimization cannot consider safety constraints simultaneously,so the safe operation of an IEHS cannot be guaranteed.Thus,distributionally robust joint chance constraints and robust constraints are jointly introduced into the IEHS dispatch problem in this paper to obtain a stronger safety guarantee,and a method combined with Bonferroni and conditional value at risk(CVaR)approximation is presented to transform the original model into a quadratic program.Additionally,a dynamic boundary response(DBR)-based distributed algorithm based on multiparametric programming is proposed for a fast solution.Case studies showcase the necessity of using mixed distributionally robust joint chance constraints and robust constraints,as well as the effectiveness of the DBR algorithm.
基金supported by the China National Key Research and Development Program"Integrated convection/radiation coupling terminals for local environment"(2022YFC3801502)the National Natural Science Foundation of China(52108082,52130803,and 52394223)+2 种基金the China Postdoctoral Science Foundation(2023M732479)the Natural Science Foundation of Sichuan Province of China(2024NSFSC0916)the New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘Intermittent heating is an energy-saving heating mode,which can save energy in terms of time,and thus is worth promoting,particularly in residential heating scenarios.Conventional radiant heating terminals,that is floor heating,and convective heating terminals,that is fan coils,cannot achieve both intermittent and thermal comfort during intermittent heating.Therefore,this study proposes a switchable convective-radiant heating regulation method for floor heating and fan coils to achieve a comfortable indoor environment with high thermal response speed.Furthermore,a novel combined radiant-convective heating terminal was proposed for a reliable and effective solution.Results showed that the proposed switchable method could increase both intermittence and thermal comfort.In addition,the heating terminal showed better heating performance than the combination of two conventional terminals at the key points of heating capacity,flexibility,and thermal response.It could initially heat up a typical residential space within 20-40 min and then stabilize the room temperature in a comfortable range of 18-22℃,showing great potential for intermittent heating in room-scale heating conditions.This study provides a reference technique for intermittent heating with reduced system complexity and precise environmental control.
基金financially supported by the National Key Research and Development Program of China(No.2023YFC3904800)the National Outstanding Young Scientists Fund(No.5a2125002)+7 种基金the National Science Foundation of China(No.22476073)the Key Project of Jiangxi Provincial Research and Development Program(Nos.20223BBG74006 and 20243BBI91001)the China Postdoctoral Science Foundation(No.2024M751282)the “Thousand Talents Program”of Jiangxi Province(S_(2)021GDQN2161)the Key Project of Ganzhou City Research and Development Program(No.2023PGX17350)the Science&Technology Talent Lifting Project of Hunan Province(No.2022TJ-N16)the Natural Science Foundation of Hunan Province China(No.2024JJ4022,2023JJ30277)the Open-End Fund for National-Local Joint Engineering Research Center of Heavy Metals Pollutants Control and Resource Utilization(ES_(2)02480184)。
文摘Lithium-ion batteries(LIBs)are critical for the rapid growth of electric vehicles(EVs),but their inherent lifespan leads to numerous retirements and resource challenges.The efficacy of conventional recycling techniques is increasingly compromised by their high energy consumption and secondary pollution,rendering them less responsive to greener and more sustainable requirement of rapid development.Thus,the direct recycling process emerged and was considered as a more expedient and convenient method of recycling compared to the conventional recycling modes that are currently in study.However,due to the reliance on the indispensable sintering process,direct recycling still faces considerable challenges,motivating researchers to explore faster,greener,and more cost-effective strategies for LIBs recycling,Inspiringly,Joule heating recycling(JHR),an emerging technique,offers rapid,efficient impurity removal and material regeneration with minimal environmental impact,addressing limitations of existing methods.This method reduces the time for direct recycling of spent LIBs by a factor of at least three orders of magnitude and exhibits significant potential for future industrial production.Unfortunately,due to the lack of systematic organization and reporting,this next generation approach to direct recycling of spent LIBs has not yet gained much interest.To facilitate a more profound comprehension of rising flash recycling strategy,in this study,JHR is distinguished into two distinctive implementation pathways(including flash Joule heating and carbon thermal shock),designed to accommodate varying pretreatment stages and diverse spent LIBs materials.Subsequently,the advantages of the recently developed JHR of spent LIBs in terms of material performance,environmental friendliness,and economic viability are discussed in detail.Ultimately,with the goal of achieving more attractive society effects,the future direction of JHR of spent LIBs and its potential for practical application are proposed and envisaged.
基金supported by the National Natural Science Foundation of China(Nos.52275299,52105313)R&D Program of Beijing Municipal Education Commission(No.KM202210005036)+1 种基金Natural Science Foundation of Chongqing,China(No.CSTB2023NSCQ-MSX0701)National Defense Basic Research Projects of China(No.JCKY2022405C002).
文摘Friction rolling additive manufacturing(FRAM)is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head.The thermal efficiency of FRAM,which depends only on friction to generate heat,is low,and the thermal-accumulation effect of the deposition process must be addressed.An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling(PC-FRAM)is devised in this study,and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head.Additionally,2195-T87 Al-Li alloy is used as the feed material,and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated.The results show that water cooling significantly improves heat accumulation during the deposition process.The cooling rate increases by 11.7 times,and the high-temperature residence time decreases by more than 50%.The grain size of the PC-FRAM sample is the smallest,i.e.,3.77±1.03μm,its dislocation density is the highest,and the number density of precipitates is the highest,the size of precipitates is the smallest,which shows the best precipitation-strengthening effect.The hardness test results are consistent with the precipitation distribution.The ultimate tensile strength,yield strength and elongation of the PC-FRAM samples are the highest(351±15.6 MPa,251.3±15.8 MPa and 16.25%±1.25%,respectively)among the samples investigated.The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples.The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect.
基金supported by the China Postdoctoral Science Foundation(No.2023M732344)the National Natural Science Foundation of China(Nos.51973119,52327802,52173078)+4 种基金Shenzhen Key Laboratory of Photonics and Biophotonics(ZDSYS20210623092006020)Shenzhen Key Laboratory for Low-carbon Natural Science Foundation of Guangdong Province(No.2024A1515010639)Construction Material and Technology(No.ZDSYS20220606100406016)National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment(Shenzhen)(No.868-000003010103)Joint Funds of Ministry of Education(No.8091B022225).
文摘Self-regulating heating and self-powered flexibility are pivotal for future wearable devices.However,the low energy-conversion rate of wearable devices at low temperatures limits their application in plateaus and other environments.This study introduces an azopolymer with remarkable semicrystallinity and reversible photoinduced solid-liquid transition ability that is obtained through copolymerization of azoben-zene(Azo)monomers and styrene.A composite of one such copolymer with an Azo:styrene molar ratio of 9:1(copolymer is denoted as PAzo9:1-co-polystyrene(PS))and nylon fabrics(NFs)is prepared(composite is denoted as PAzo9:1-co-PS@NF).PAzo9:1-co-PS@NF exhibits hydrophobicity and high wear resistance.Moreover,it shows good responsiveness(0.624 s^(−1))during isomerization under solid ultraviolet(UV)light(365 nm)with an energy density of 70.6 kJ kg^(−1).In addition,the open-circuit voltage,short-circuit current and quantity values of PAzo9:1-co-PS@NF exhibit small variations in a temperature range of−20℃ to 25℃ and remain at 170 V,5 μA,and 62 nC,respectively.Notably,the involved NFs were cut and sewn into gloves to be worn on a human hand model.When the model was exposed to both UV radiation and friction,the temperature of the finger coated with PAzo9:1-co-PS was approximately 6.0°C higher than that of the other parts.Therefore,developing triboelectric nanogenerators based on the in situ photothermal cycles of Azo in wearable devices is important to develop low-temperature self-regulating heating and self-powered flexible devices for extreme environments.
基金supported by the National Social Science Fund of China[Grant No.21BGL181]to Yan Chen.
文摘Coal dependence and inefficient decentralized heating have significantly increased China’s energy consumption for winter heating,increasing air pollution and exacerbating the greenhouse effect.In 2017,China implemented the Pilot Policy on Clean Winter Heating in Northern China,aiming to achieve high central heating coverage and cleaner energy consumption.Studying the effects of this policy can help promote its implementation and serve as a reference for effective adjustment of the contents in the future.However,few studies have investigated this policy and its carbon reduction effects,and most focus on the provincial or city levels.Therefore,this paper considers the policy’s influence on air pollution and carbon emissions at the county level to provide a precise and comprehensive assessment of the policy effects.We use panel data from 1290 counties in 15 provinces in Northern China from 2014 to 2021,applying a multiperiod difference-in-differences model to quantify the impact of the policy on carbon emissions and air quality in the pilot area.We then conduct a series of tests to demonstrate the robustness of the results and analyze the mechanisms of the policy effects from two perspectives,namely,central heating and natural gas use,through a mediating effect model.Finally,we examine the heterogeneity of policy effects between counties based on geographic location and per capita income levels of rural residents through a moderating effect model.The results reveal that the policy significantly reduces air pollution and carbon emissions in the pilot area by increasing the central heating area and natural gas use.Compared with the central and western regions in the north and areas with low-income rural residents,the policy effects in the eastern regions in the north and areas with high-income rural residents are more pronounced.
文摘Grain-oriented silicon steels were prepared at different heating rates during high temperature annealing,in which the evolution of magnetic properties,grain orientations and precipitates were studied.To illustrate the Zener factor,the diameter and number density of precipitates of interrupted testing samples were statistically calculated.The effect of precipitate ripening on the Goss texture and magnetic property was investigated.Data indicated that the trend of Zener factor was similar under different heating rates,first increasing and then decreasing,and that the precipitate maturing was greatly inhibited as the heating rate increased.Secondary recrystallization was developed at the temperature of 1010℃when a heating rate of 5℃/h was used,resulting in Goss,Brass and{110}<227>oriented grains growing abnormally and a magnetic induction intensity of 1.90T.Furthermore,increasing the heating rate to 20℃/h would inhibit the development of undesirable oriented grains and obtain a sharp Goss texture.However,when the heating rate was extremely fast,such as 40℃/h,poor secondary recrystallization was developed with many island grains,corresponding to a decrease in magnetic induction intensity to 1.87 T.At a suitable heating rate of 20℃/h,the sharpest Goss texture and the highest magnetic induction of 1.94 T with an onset secondary recrystallization temperature of 1020℃were found among the experimental variables in this study.The heating rate affected the initial temperature of secondary recrystallization by controlling the maturation of precipitates,leading to the deviation and dispersion of Goss texture,thereby reducing the magnetic properties.
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support by the Shanghai Engineering Research Center for Shallow Geothermal Energy(DRZX-202306)Shaanxi Coal Geology Group Co.,Ltd.(SMDZ-ZD2024-23)+4 种基金Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Natural Resources,China(ZP2020-1)Shaanxi Investment Group Co.,Ltd.(SIGC2023-KY-05)Key Research and Development Projects of Shaanxi Province(2023-GHZD-54)Shaanxi Qinchuangyuan Scientist+Engineer Team Construction Project(2022KXJ-049)China Postdoctoral Science Foundation(2023M742802,2024T170721).
文摘Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems,which are essential for decision-making.Therefore,this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems.Based on the geological parameters of Xi’an,China and commonly used borehole heat exchanger structures,numerical simulationmethods are employed to analyze performance and economic efficiency.The results indicate that increasing the spacing between shallow borehole heat exchangers can effectively reduce thermal interference between the pipes and improve heat extraction performance.As the flow rate increases,the outlet water temperature ranges from 279.3 to 279.7 K,with heat extraction power varying between 595 and 609 W.For medium-deep borehole heat exchangers,performance predictions show that a higher flow rate results in greater heat extraction power.However,when the flow rate exceeds 30 m^(3)/h,further increases in flow rate have only a minor effect on enhancing heat extraction power.Additionally,the economic analysis reveals that the payback period for shallow geothermal heating systems ranges from 10 to 11 years,while for medium-deep geothermal heating systems,it varies more widely from 3 to 25 years.Therefore,the payback period for medium-deep geothermal heating systems is more significantly influenced by operational and installation parameters,and optimizing these parameters can considerably shorten the payback period.The results of this study are expected to provide valuable insights into the efficient and cost-effective utilization of geothermal energy for building heating.
基金This work was supported by the project of the Research on Energy Consumption of Office Space in Colleges and Universities under the“Dual Carbon Target”(No.CJ202301006).
文摘The development of efficient and clean heating technologies is crucial for reducing carbon emissions in regions with severe cold regions.This research designs a novel two-stage phase change heat storage coupled solar-air source heat pump heating system structure that is specifically designed for such regions.The two-stage heat storage device in this heating system expands the storage temperature range of solar heat.The utilization of the two-stage heat storage device not onlymakes up for the instability of the solar heating system,but can also directlymeet the building heating temperature,and can reduce the influence of low-temperature outdoor environments in severe cold regions on the heating performance of the air source heat pump by using solar energy.Therefore,the two-stage phase change heat storage coupled to the solar energy-air source heat pump heating system effectively improves the utilization rate of solar energy.A numerical model of the system components and their integration was developed using TRNSYS software in this study,and various performance aspects of the system were simulated and analyzed.The simulation results demonstrated that the two-stage heat storage device can effectively store solar energy,enabling its hierarchical utilization.The low-temperature solar energy stored by the two-stage phase change heat storage device enhances the coefficient of performance of the air source heat pump by 11.1%in severe cold conditions.Using the Hooke-Jeeves optimization method,the annual cost and carbon emissions are taken as optimization objectives,with the optimized solar heat supply accounting for 52.5%.This study offers valuable insights into operational strategies and site selection for engineering applications,providing a solid theoretical foundation for the widespread implementation of this system in severe cold regions.
基金supported by the fund of the National Natural Science Foundation of China(Nos.22378249,22078184,and 22171170)the China Postdoctoral Science Foundation(No.2019M653853XB)the Natural Science Advance Research Foundation of Shaanxi University of Science and Technology(No.2018QNBJ-03).
文摘The demand for flexible electric heating devices has increased due to technology advancement and improved living standards.These devices have various applications including personal thermal management,hyperthermia,defrosting,agricultural heating film,and oil-water separation.Joule heat,generated by electric currents,is commonly used in electrical appliances.To incorporate Joule heating into flexible electronics,new materials with excellent mechanical properties are necessary.Traditional polymers,used as reinforcements,limit the continuity of conductive networks in composites.Therefore,there is a need to develop flexible Joule thermal composite materials with enhanced mechanical strength and conductivity.Cellulose,a widely available renewable resource,is attracting attention for its excellent mechanical properties.It can be used as a dispersant and reinforcing agent for conductive fillers in cellulose-based composites,creating highly conductive networks.Various forms of cellulose,such as wood,nanocellulose,pulp fiber,bacterial cellulose,cellulose paper,textile clothing,and aramid fiber,have been utilized to achieve high-performance Joule thermal composites.Researchers have achieved excellent mechanical properties and developed efficient electric heating devices by designing cellulose-based composites with different structures.The scalable production methods enable large-scale application of cellulose-based devices,each with unique advantages in 1D,2D,and 3D structures.This review summarizes recent advancements in cellulose-based Joule thermal composites,providing insights into different structural devices,and discussing prospects and challenges in the field.
