The phase transformation of hydroxyapatite (HAP, Ca10(PO4)6(OH)2) to the beta tricalcium phosphate phase (β-TCP, β-Ca3(PO4)2) at 1100°C is well known. However, in the case of human tooth, the HAP phase transfor...The phase transformation of hydroxyapatite (HAP, Ca10(PO4)6(OH)2) to the beta tricalcium phosphate phase (β-TCP, β-Ca3(PO4)2) at 1100°C is well known. However, in the case of human tooth, the HAP phase transformation is still an open area. For example, the CaO phase has sometimes been reported in the set of phases that make up the teeth. In this study, physical changes of human teeth when subjected to heat treatment in inert atmosphere (argon) were studied. The results were compared with those obtained in air atmosphere, from room temperature (25°C) up to 1200°C. Morphological changes were analyzed by light and scanning electron microscopy (SEM). The HAP to β-TCP phase transformation was followed in powder samples by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Heating of teeth results in the removal of organic material and structural water before the HAP to β-TCP phase transformation, the increment in hardness and the induced crystal growth. The percentage of the phases, crystal growth and lattice parameter variations as a function of temperature was quantified by Rietveld analysis. The black color was observed in dentin heated under argon atmosphere. Differences in expansivity produce fractures in dentin at 300°C in argon and at 400°C in air. In dentin, the coexistence of the HAP and β-TCP phases was observed after 800°C in argon and after 600°C in air;in enamel it was observed at 600°C in argon compared with 400°C in air. In general, the role played by the argon atmosphere during the thermal treatment of the teeth is to retard the processes observed in air.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
Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The...Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The laboratory uniaxial compression experiments were also conducted.Then,a coupled thermo-mechanical ordinary state-based peridynamic(OSB-PD)model and corresponding numerical scheme were developed to simulate the damage of rocks after the heating and cooling processes,and the change of crack evolution process was predicted.The results demonstrate that elevated heating temperatures exacerbate the thermal damage to the specimens,resulting in a decrease in peak strength and an increase in ductility of granite.The escalating occurrence of thermal-induced cracks significantly affects the crack evolution process during the loading phase.The numerical results accurately reproduce the damage and fracture characteristics of the granite under different final heating temperatures(FHTs),which are consistent with the test results in terms of strength,crack evolution process,and failure mode.展开更多
Stabilization of tearing modes and neoclassical tearing modes is of great importance for tokamak operation.Electron cyclotron waves(ECWs)have been extensively used to stabilize the tearing modes with the virtue of hig...Stabilization of tearing modes and neoclassical tearing modes is of great importance for tokamak operation.Electron cyclotron waves(ECWs)have been extensively used to stabilize the tearing modes with the virtue of highly localized power deposition.Complete suppression of the m/n=2/1 tearing mode(TM)by electron cyclotron resonance heating(ECRH)has been achieved successfully on the J-TEXT tokamak.The effects of ECW deposition location and power amplitude on the 2/1 TM suppression have been investigated.It is found that the suppression is more effective when the ECW power is deposited closer to the rational surface.As the ECW power increases to approximately 230 k W,the 2/1 TM can be completely suppressed.The island rotation frequency is increased when the island width is reduced.The experimental results show that the local heating inside the magnetic island and the resulting temperature perturbation increase at the O-point of the island play dominant roles in TM suppression.As the ECW power increases,the 2/1 island is suppressed to smaller island width,and the flow shear also plays a stabilizing effect on small magnetic islands.With the stabilizing contribution of heating and flow shear,the 2/1 TM can be completely suppressed.展开更多
Based on the first and second laws of thermodynamics,the heat transfer and flow(thermohydraulic)characteristics of horizontal supercritical pressure CO_(2)(S-CO_(2))in a circular pipe under heating conditions were inv...Based on the first and second laws of thermodynamics,the heat transfer and flow(thermohydraulic)characteristics of horizontal supercritical pressure CO_(2)(S-CO_(2))in a circular pipe under heating conditions were investigated numerically.Heating flows in two different diameters(d)of 4 and 6 mm were simulated in pipes with pressures of 8 MPa,mass fluxes(G)of 300 and 400 kg/(m^(2)·s),and heat fluxes(q)of 50,75 and 100 kW/m^(2).In the d=4 mm pipe,the peak heat transfer coefficient(hb)was about 3 times higher than in the d=6 mm pipe,while the entropy production due to fluid friction in the 4 mm pipe was on average 1.1 times higher,and the entropy production due to heat transfer was on average about 67%lower.A 4 mm tube was employed to further evaluate the influence of the applied wall heat flux,the results demonstrated that the irreversibility due to heat transfer was on average more than 4 times higher when heat flux density was 100 kW/m^(2)than when the heat flux density was 50 kW/m^(2),while the peak of heat transfer coefficient increased by 1.4 times as q was decreased from 100 to 50 kW/m^(2).The effect of thermal acceleration was ignored,while the buoyancy effect resulted in secondary flow and significantly affected the flow and heat transfer features.The jet flows were found in the vicinity of the lower wall of the pipe,which made the two fields of velocity and temperature gradient more synergistic,leading to an enhancement in heat transfer in the vicinity of the upper wall.The aggravation of heat transfer resulted in high irreversibility of heat transfer in the cross-sectional area near the wall,while the local friction irreversibility was less affected by the buoyancy effect,and the distribution was uniform.The uneven distribution of thermophysical properties also confirmed that the enhanced heat transfer occurred near the wall area at the bottom of the pipe.展开更多
The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea...The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea continental shelf is still not clear due to the sparsity of observations.By employing a coupled regional ocean-sea ice-ice shelf model for the Ross Sea,this study analyzes the heat budget of water masses over the continental shelf and in the RIS cavity.According to the topographic features and the HC density,the continental shelf region is divided into 17 subdomains.The heat budget of the middle layer for every subdomain is analyzed.In addition,the heat budget for the RIS cavity is assessed for the first time.Owing to Modified Circumpolar Deep Water intrusion,water masses over the eastern shelf are warmer than over the western shelf,with the coldest water identified in the southwestern inner shelf.The horizontal heat flux mainly provides heat to the continental shelf,while the atmospheric forcing tends to warm up the ocean during the ice-melting period and cool down the ocean during the ice-freezing period.The vertical heat flux is generally upward and transports heat from the deep layer to the upper layer.In the RIS cavity,the seasonal cycle of the HC is dominated by the horizontal flux across the RIS front rather than the basal thermal forcing of the RIS.展开更多
The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the ...The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the compact integration of the OMP presents challenges inefficiently dissipating internal heat,leading to a performance degradation of the EHA due to ele-vated temperatures.Therefore,accurately modeling and predicting the internal thermal dynamicsof the OMP hold considerable significance for monitoring the operational condition of the EHA.In view of this,a modeling method considering cumulative thermal coupling was hereby proposed.Based on the proposed method,the thermal models of the motor and the pump were established,taking into account heat accumulation and transfer.Taking the leakage oil as the heat couplingpoint between the motor and the pump,the dynamic thermal coupling model of the OMP wasdeveloped,with the thermal characteristics of the oil considered.Additionally,the comparativeexperiments were conducted to illustrate the efficiency of the proposed model.The experimentalresults demonstrate that the proposed dynamic thermal coupling model accurately captured thethermal behavior of OMP,outperforming the static thermal parameter model.Overall,thisadvancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.展开更多
For nickel-based superalloys with medium volume-fractionγʹphase(20%-40%),dual or multi-stage aging treatments are usually conducted to generate a microstructure containing the multimodal distri-bution ofγʹfor a bala...For nickel-based superalloys with medium volume-fractionγʹphase(20%-40%),dual or multi-stage aging treatments are usually conducted to generate a microstructure containing the multimodal distri-bution ofγʹfor a balance of strength and plasticity.In the present study,the microstructure and high-temperature properties of a novel cast nickel-based superalloy K4800 were investigated after being sub-jected to three heat treatments(HT)procedures,namely HT1:1180℃/4 h+1090℃/2 h+800℃/16 h,HT2:1180℃/4 h+1060℃/2 h+800℃/16 h and HT3:1180℃/4 h+800℃/16 h.It was found that the sub-solvus aging treatments at 1090 and 1060℃ precipitated sub-micron-sized(∼300 nm)primaryγʹphase which enhanced the ductility during 800℃ tensile(the total elongation of T1,T2,and T3 sam-ples were 6.75%,7.3%,and 3.25%,respectively)without evidently impairing the strength.After careful microstructure observation and deformation mechanism analysis,the enhancement of elongation was ra-tionalized that the precipitation of the sub-micron-sized primaryγʹphase decreased the volume-fraction and size of the nanometer-sizedγʹphase which was precipitated at 800℃,and simultaneously,pro-moted the dislocation movement by suppressing the non-planar slip.However,an excessive amount of the sub-micron-sized primaryγʹphase led to a faster ripening process of the nanometer-sizedγʹduring creep,which decreased the creep life at 800℃/430 MPa(T1:125 h,T2:199 h,and T3:198 h).Based on this,we monitored the number density of nanometer-sizedγʹphase coexisting with different amounts of largeγʹduring creep.An area fraction less than 7%of the sub-micron-sizedγʹphase was considered to have little detrimental effect on the creep life of K4800 alloy,which corresponded to a sub-solvus temperature range about 1080-1090℃.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
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
Laser additively manufactured(LAM)Ni-based superalloys commonly exhibit low strength and high residual stress in the as-built state,requiring post-heat treatment to improve mechanical properties.We propose a modified ...Laser additively manufactured(LAM)Ni-based superalloys commonly exhibit low strength and high residual stress in the as-built state,requiring post-heat treatment to improve mechanical properties.We propose a modified heat treatment(MHT)process that only involves a single-step aging at 650℃ for 4 h to achieve high strength,high ductility,and low residual stress simultaneously in a laser powder bed fusion(LPBF)-processed Inconel 718(IN718)alloy.The MHT treated alloy exhibits comparable tensile strength(1368 MPa)to the conventional solution plus two-step aging(SA)treated alloy(1398 MPa),while the tensile elongation(∼21.7%for MHT treated alloy and 13.4%for SA treated alloy)is 60%higher and the residual stress(∼195 MPa)is 20%lower than the SA treated alloy.The balanced high performance of the MHT IN718 alloy was mainly attributed to the precipitation of abundantγ’’phase with a size of∼5 nm,while the original nano-sized Laves precipitates and dislocation cells were mostly retained.The finer size and higher fraction ofγ”of the MHT sample mainly result from the dislocation structure and compositional variations in the as-built IN718,which promotes precipitation during aging.The retention of Laves phase,and cellular dislocation network in the MHT alloy also contributes to work hardening during tension and suspends the occurrence of necking.This study unveils a unique strengthening and toughening mechanism in the Ni-based superalloy produced by LAM with the presence of abundant Laves precipitates and provides a simple,low energy-consumption and cost-effective heat treatment route for achieving desirable mechanical properties.展开更多
Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,i...Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.展开更多
The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the micr...The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the microstructure evolution and mechanical properties of the joint was analyzed,and the joint electrochemical corrosion behavior as well as the hot corrosion behavior was studied.The results show that the joint hardness of Base Metal(BM)increases after pre-weld heat treatment,and the strengthening phasesγ′andγ″further precipitate.However,the precipitation phases dissolve significantly in the Weld Zone(WZ)due to the thermal process of LFW.The corrosion resistance in BM is reduced after the pre-weld heat treatment,while it is similar in WZ with a slight decrease.The surface morphology of the BM and WZ can be generally divided into a loose and porous matrix and a scattered oxide particle layer after hot corrosion.The joint cross section exhibits a Cr-depleted zone with the diffusion of Cr to form an oxide film.The corrosion product mainly consists of Fe_(2)O_(3)/Fe_(3)O_(4) as the outer layer and Cr_(2)O_(3) as the inner layer.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 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
This study investigates the feasibility and efficiency of geothermal energy for heating applications in Azerbaijan,with a specific focus on the Khachmaz region.Despite the country’s growing interest in sustainable en...This study investigates the feasibility and efficiency of geothermal energy for heating applications in Azerbaijan,with a specific focus on the Khachmaz region.Despite the country’s growing interest in sustainable energy,limited research has addressed the potential of ground-source heat pump(GSHP)systems under local climatic and soil conditions.To address this gap,the study employs GeoT*SOL simulation to evaluate systemperformance,incorporating site-specific parameters such as soil thermal conductivity,heating demand profiles,and regional weather data.The results show that the GSHP system achieves a maximum seasonal performance factor(SPF)of 5.62 and an average SPF of 4.86,indicating high operational efficiency.Additionally,the system provides an estimated annual CO_(2) emissions reduction of 1956 kg per household,highlighting its environmental benefits.Comparative analysis with conventional heating systems demonstrates considerable energy savings and emissions mitigation.The study identifies technical(e.g.,initial installation complexity)and economic(e.g.,high upfront costs)challenges to widespread implementation.Based on these insights,practical recommendations are proposed:policymakers are encouraged to support financial incentives and policy frameworks;urban planners should consider GSHP integration in regional heating plans;and engineers may adopt the simulation-based approach presented here for feasibility studies.This research contributes to the strategic advancement of renewable heating technologies in Azerbaijan.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
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
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
文摘The phase transformation of hydroxyapatite (HAP, Ca10(PO4)6(OH)2) to the beta tricalcium phosphate phase (β-TCP, β-Ca3(PO4)2) at 1100°C is well known. However, in the case of human tooth, the HAP phase transformation is still an open area. For example, the CaO phase has sometimes been reported in the set of phases that make up the teeth. In this study, physical changes of human teeth when subjected to heat treatment in inert atmosphere (argon) were studied. The results were compared with those obtained in air atmosphere, from room temperature (25°C) up to 1200°C. Morphological changes were analyzed by light and scanning electron microscopy (SEM). The HAP to β-TCP phase transformation was followed in powder samples by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Heating of teeth results in the removal of organic material and structural water before the HAP to β-TCP phase transformation, the increment in hardness and the induced crystal growth. The percentage of the phases, crystal growth and lattice parameter variations as a function of temperature was quantified by Rietveld analysis. The black color was observed in dentin heated under argon atmosphere. Differences in expansivity produce fractures in dentin at 300°C in argon and at 400°C in air. In dentin, the coexistence of the HAP and β-TCP phases was observed after 800°C in argon and after 600°C in air;in enamel it was observed at 600°C in argon compared with 400°C in air. In general, the role played by the argon atmosphere during the thermal treatment of the teeth is to retard the processes observed in air.
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funded by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_0613)the National Natural Science Foundation of China(Grant Nos.41831278 and 51878249).
文摘Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects.This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures.The laboratory uniaxial compression experiments were also conducted.Then,a coupled thermo-mechanical ordinary state-based peridynamic(OSB-PD)model and corresponding numerical scheme were developed to simulate the damage of rocks after the heating and cooling processes,and the change of crack evolution process was predicted.The results demonstrate that elevated heating temperatures exacerbate the thermal damage to the specimens,resulting in a decrease in peak strength and an increase in ductility of granite.The escalating occurrence of thermal-induced cracks significantly affects the crack evolution process during the loading phase.The numerical results accurately reproduce the damage and fracture characteristics of the granite under different final heating temperatures(FHTs),which are consistent with the test results in terms of strength,crack evolution process,and failure mode.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China(No.2019YFE03010004)the Hubei Provincial Natural Science Foundation of China(No.2022CFA072)National Natural Science Foundation of China(No.51821005)。
文摘Stabilization of tearing modes and neoclassical tearing modes is of great importance for tokamak operation.Electron cyclotron waves(ECWs)have been extensively used to stabilize the tearing modes with the virtue of highly localized power deposition.Complete suppression of the m/n=2/1 tearing mode(TM)by electron cyclotron resonance heating(ECRH)has been achieved successfully on the J-TEXT tokamak.The effects of ECW deposition location and power amplitude on the 2/1 TM suppression have been investigated.It is found that the suppression is more effective when the ECW power is deposited closer to the rational surface.As the ECW power increases to approximately 230 k W,the 2/1 TM can be completely suppressed.The island rotation frequency is increased when the island width is reduced.The experimental results show that the local heating inside the magnetic island and the resulting temperature perturbation increase at the O-point of the island play dominant roles in TM suppression.As the ECW power increases,the 2/1 island is suppressed to smaller island width,and the flow shear also plays a stabilizing effect on small magnetic islands.With the stabilizing contribution of heating and flow shear,the 2/1 TM can be completely suppressed.
基金supported by the European Union’s Horizon 2020 Research and Innovation Programme Project(No.882628)(Guo,https://cinea.ec.europa.eu/programmes/horizon-europe_en)(acceseed on 08 October 2024),and the Fundamental Research Funds for the Central Universities(buctrc202406)(Guo,https://english.buct.edu.cn/)(accessed on 08 October 2024).
文摘Based on the first and second laws of thermodynamics,the heat transfer and flow(thermohydraulic)characteristics of horizontal supercritical pressure CO_(2)(S-CO_(2))in a circular pipe under heating conditions were investigated numerically.Heating flows in two different diameters(d)of 4 and 6 mm were simulated in pipes with pressures of 8 MPa,mass fluxes(G)of 300 and 400 kg/(m^(2)·s),and heat fluxes(q)of 50,75 and 100 kW/m^(2).In the d=4 mm pipe,the peak heat transfer coefficient(hb)was about 3 times higher than in the d=6 mm pipe,while the entropy production due to fluid friction in the 4 mm pipe was on average 1.1 times higher,and the entropy production due to heat transfer was on average about 67%lower.A 4 mm tube was employed to further evaluate the influence of the applied wall heat flux,the results demonstrated that the irreversibility due to heat transfer was on average more than 4 times higher when heat flux density was 100 kW/m^(2)than when the heat flux density was 50 kW/m^(2),while the peak of heat transfer coefficient increased by 1.4 times as q was decreased from 100 to 50 kW/m^(2).The effect of thermal acceleration was ignored,while the buoyancy effect resulted in secondary flow and significantly affected the flow and heat transfer features.The jet flows were found in the vicinity of the lower wall of the pipe,which made the two fields of velocity and temperature gradient more synergistic,leading to an enhancement in heat transfer in the vicinity of the upper wall.The aggravation of heat transfer resulted in high irreversibility of heat transfer in the cross-sectional area near the wall,while the local friction irreversibility was less affected by the buoyancy effect,and the distribution was uniform.The uneven distribution of thermophysical properties also confirmed that the enhanced heat transfer occurred near the wall area at the bottom of the pipe.
基金supported by the National Key R&D Program of China (Grant No. 2024YFF0506603)the Independent Research Foundation of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant Nos. SML2023SP201 and SML2021SP306)+2 种基金the Natural Science Foundation of Guangdong Province, China (Grant No. 2024A1515012717)the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant Nos. 313021004, 313022009 and 313022001)the Program of Innovation 2030 on Smart Ocean, Zhejiang University
文摘The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea continental shelf is still not clear due to the sparsity of observations.By employing a coupled regional ocean-sea ice-ice shelf model for the Ross Sea,this study analyzes the heat budget of water masses over the continental shelf and in the RIS cavity.According to the topographic features and the HC density,the continental shelf region is divided into 17 subdomains.The heat budget of the middle layer for every subdomain is analyzed.In addition,the heat budget for the RIS cavity is assessed for the first time.Owing to Modified Circumpolar Deep Water intrusion,water masses over the eastern shelf are warmer than over the western shelf,with the coldest water identified in the southwestern inner shelf.The horizontal heat flux mainly provides heat to the continental shelf,while the atmospheric forcing tends to warm up the ocean during the ice-melting period and cool down the ocean during the ice-freezing period.The vertical heat flux is generally upward and transports heat from the deep layer to the upper layer.In the RIS cavity,the seasonal cycle of the HC is dominated by the horizontal flux across the RIS front rather than the basal thermal forcing of the RIS.
基金supported by the National Key R&D Program of China(No.2021YFB2011300)the National Natural Science Foundation of China(Nos.52275044,U2233212)。
文摘The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the compact integration of the OMP presents challenges inefficiently dissipating internal heat,leading to a performance degradation of the EHA due to ele-vated temperatures.Therefore,accurately modeling and predicting the internal thermal dynamicsof the OMP hold considerable significance for monitoring the operational condition of the EHA.In view of this,a modeling method considering cumulative thermal coupling was hereby proposed.Based on the proposed method,the thermal models of the motor and the pump were established,taking into account heat accumulation and transfer.Taking the leakage oil as the heat couplingpoint between the motor and the pump,the dynamic thermal coupling model of the OMP wasdeveloped,with the thermal characteristics of the oil considered.Additionally,the comparativeexperiments were conducted to illustrate the efficiency of the proposed model.The experimentalresults demonstrate that the proposed dynamic thermal coupling model accurately captured thethermal behavior of OMP,outperforming the static thermal parameter model.Overall,thisadvancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.
文摘For nickel-based superalloys with medium volume-fractionγʹphase(20%-40%),dual or multi-stage aging treatments are usually conducted to generate a microstructure containing the multimodal distri-bution ofγʹfor a balance of strength and plasticity.In the present study,the microstructure and high-temperature properties of a novel cast nickel-based superalloy K4800 were investigated after being sub-jected to three heat treatments(HT)procedures,namely HT1:1180℃/4 h+1090℃/2 h+800℃/16 h,HT2:1180℃/4 h+1060℃/2 h+800℃/16 h and HT3:1180℃/4 h+800℃/16 h.It was found that the sub-solvus aging treatments at 1090 and 1060℃ precipitated sub-micron-sized(∼300 nm)primaryγʹphase which enhanced the ductility during 800℃ tensile(the total elongation of T1,T2,and T3 sam-ples were 6.75%,7.3%,and 3.25%,respectively)without evidently impairing the strength.After careful microstructure observation and deformation mechanism analysis,the enhancement of elongation was ra-tionalized that the precipitation of the sub-micron-sized primaryγʹphase decreased the volume-fraction and size of the nanometer-sizedγʹphase which was precipitated at 800℃,and simultaneously,pro-moted the dislocation movement by suppressing the non-planar slip.However,an excessive amount of the sub-micron-sized primaryγʹphase led to a faster ripening process of the nanometer-sizedγʹduring creep,which decreased the creep life at 800℃/430 MPa(T1:125 h,T2:199 h,and T3:198 h).Based on this,we monitored the number density of nanometer-sizedγʹphase coexisting with different amounts of largeγʹduring creep.An area fraction less than 7%of the sub-micron-sizedγʹphase was considered to have little detrimental effect on the creep life of K4800 alloy,which corresponded to a sub-solvus temperature range about 1080-1090℃.
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.
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financially supported by the Ministry of Science and Technology of China via the National Key Research&Development Plan(Nos.2022YFB3707105 and 2020YFA0405900)Jiangsu Department of Science and Technology via Provincial Key Research&Development(Industrial Foresight and Key Core Technology,No.BE2021037)+1 种基金Department of the National Science Foundation of China(No.52204390)the Natural Science Foundation of Jiangsu Province(No.BK20202010).
文摘Laser additively manufactured(LAM)Ni-based superalloys commonly exhibit low strength and high residual stress in the as-built state,requiring post-heat treatment to improve mechanical properties.We propose a modified heat treatment(MHT)process that only involves a single-step aging at 650℃ for 4 h to achieve high strength,high ductility,and low residual stress simultaneously in a laser powder bed fusion(LPBF)-processed Inconel 718(IN718)alloy.The MHT treated alloy exhibits comparable tensile strength(1368 MPa)to the conventional solution plus two-step aging(SA)treated alloy(1398 MPa),while the tensile elongation(∼21.7%for MHT treated alloy and 13.4%for SA treated alloy)is 60%higher and the residual stress(∼195 MPa)is 20%lower than the SA treated alloy.The balanced high performance of the MHT IN718 alloy was mainly attributed to the precipitation of abundantγ’’phase with a size of∼5 nm,while the original nano-sized Laves precipitates and dislocation cells were mostly retained.The finer size and higher fraction ofγ”of the MHT sample mainly result from the dislocation structure and compositional variations in the as-built IN718,which promotes precipitation during aging.The retention of Laves phase,and cellular dislocation network in the MHT alloy also contributes to work hardening during tension and suspends the occurrence of necking.This study unveils a unique strengthening and toughening mechanism in the Ni-based superalloy produced by LAM with the presence of abundant Laves precipitates and provides a simple,low energy-consumption and cost-effective heat treatment route for achieving desirable mechanical properties.
基金supported by 2024 Central Guidance Local Science and Technology Development Fund Project"Study on the mechanism and evaluation method of thermal pollution in water bodies,as well as research on thermal carrying capacity".(Grant 246Z4506G)Key Research and Development Project in Hebei Province:"Key Technologies and Equipment Research and Demonstration of Multiple Energy Complementary(Electricity,Heat,Cold System)for Solar Energy,Geothermal Energy,Phase Change Energy"(Grant 236Z4310G)the Hebei Academy of Sciences Key Research and Development Program"Research on Heat Transfer Mechanisms and Efficient Applications of Intermediate and Deep Geothermal Energy"(22702)。
文摘Ground source heat pump systems demonstrate significant potential for northern rural heating applications;however,the effectiveness of these systems is often limited by challenging geological conditions.For instance,in certain regions,the installation of buried pipes for heat exchangers may be complicated,and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system.To address this issue,the current study explored the use of solar-energy-collecting equipment to supplement buried pipes.In this design,both solar energy and geothermal energy provide low-temperature heat to the heat pump.First,a simulation model of a solar‒ground source heat pump coupling system was established using TRNSYS.The accuracy of this model was validated through experiments and simulations on various system configurations,including varying numbers of buried pipes,different areas of solar collectors,and varying volumes of water tanks.The simulations examined the coupling characteristics of these components and their influence on system performance.The results revealed that the operating parameters of the system remained consistent across the following configurations:three buried pipes,burial depth of 20 m,collector area of 6 m^(2),and water tank volume of 0.5 m^(3);four buried pipes,burial depth of 20 m,collector area of 3 m^(2),and water tank volume of 0.5 m^(3);and five buried pipes with a burial depth of 20 m.Furthermore,the heat collection capacity of the solar collectors spanning an area of 3 m^(2)was found to be equivalent to that of one buried pipe.Moreover,the findings revealed that the solar‒ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system,presenting a reduction of 5.31%compared to the energy consumption of the latter.
基金supported by the National Natural Science Foundation of China(Nos.52074228,52305420 and 51875470)the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University,China(No.PF2024053)the Xi’an Beilin District Science and Technology Planning Project,China(No.GX2349).
文摘The pre-weld heat treatment was carried out to obtain different initial microstructures of the GH4169 superalloy,and then Linear Friction Welding(LFW)was performed.The effect of the pre-weld heat treatment on the microstructure evolution and mechanical properties of the joint was analyzed,and the joint electrochemical corrosion behavior as well as the hot corrosion behavior was studied.The results show that the joint hardness of Base Metal(BM)increases after pre-weld heat treatment,and the strengthening phasesγ′andγ″further precipitate.However,the precipitation phases dissolve significantly in the Weld Zone(WZ)due to the thermal process of LFW.The corrosion resistance in BM is reduced after the pre-weld heat treatment,while it is similar in WZ with a slight decrease.The surface morphology of the BM and WZ can be generally divided into a loose and porous matrix and a scattered oxide particle layer after hot corrosion.The joint cross section exhibits a Cr-depleted zone with the diffusion of Cr to form an oxide film.The corrosion product mainly consists of Fe_(2)O_(3)/Fe_(3)O_(4) as the outer layer and Cr_(2)O_(3) as the inner layer.
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.
文摘This study investigates the feasibility and efficiency of geothermal energy for heating applications in Azerbaijan,with a specific focus on the Khachmaz region.Despite the country’s growing interest in sustainable energy,limited research has addressed the potential of ground-source heat pump(GSHP)systems under local climatic and soil conditions.To address this gap,the study employs GeoT*SOL simulation to evaluate systemperformance,incorporating site-specific parameters such as soil thermal conductivity,heating demand profiles,and regional weather data.The results show that the GSHP system achieves a maximum seasonal performance factor(SPF)of 5.62 and an average SPF of 4.86,indicating high operational efficiency.Additionally,the system provides an estimated annual CO_(2) emissions reduction of 1956 kg per household,highlighting its environmental benefits.Comparative analysis with conventional heating systems demonstrates considerable energy savings and emissions mitigation.The study identifies technical(e.g.,initial installation complexity)and economic(e.g.,high upfront costs)challenges to widespread implementation.Based on these insights,practical recommendations are proposed:policymakers are encouraged to support financial incentives and policy frameworks;urban planners should consider GSHP integration in regional heating plans;and engineers may adopt the simulation-based approach presented here for feasibility studies.This research contributes to the strategic advancement of renewable heating technologies in Azerbaijan.
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 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.
