This work extensively investigates the thermal characteristic evolution of lithium-ion batteries under different degradation paths,and the evolution mechanism through multi-angle characterization is revealed.Under dif...This work extensively investigates the thermal characteristic evolution of lithium-ion batteries under different degradation paths,and the evolution mechanism through multi-angle characterization is revealed.Under different degradation paths,the evolution trend of temperature rise rate remains unchanged with respect to depth of discharge during the adiabatic discharge process,albeit to varying degrees of alteration.The temperature rise rate changes significantly with aging during the adiabatic discharge process under low-temperature cycling and high-rate cycling paths.The total heat generation rate,irreversible heat generation rate,and reversible heat generation rate exhibit similar evolution behavior with aging under different degradation paths.The interval range of endothermic process of reversible electrochemical reactions increases and the contribution of irreversible heat to the total heat increases with aging.To further standardize the assessment of different degradation paths on the thermal characteristics,this work introduces the innovative concept of“Ampere-hour temperature rise”.In low-temperature cycling and high-rate cycling paths,the ampere-hour temperature rise increases significantly with aging,particularly accentuated with higher discharge rates.Conversely,in high-temperature cycling and high-temperature storage paths,the ampere-hour temperature rise remains relatively stable during the initial stages of aging,yet undergoes a notable increase in the later stages of aging.The multi-angle characterization reveals distinct thermal evolution behavior under different degradation paths primarily attributed to different behavior changes of severe side reactions,such as lithium plating.The findings provide crucial insights for the safe utilization and management of lithium–ion batteries throughout the whole lifecycle.展开更多
Nitrocellulose,or cellulose nitrate,has received considerable interest due to its various applications,such as propellants,coating agents and gas generators.However,its high mechanical sensitivity caused many accident...Nitrocellulose,or cellulose nitrate,has received considerable interest due to its various applications,such as propellants,coating agents and gas generators.However,its high mechanical sensitivity caused many accidents during its storage and usage in ammunition.In this work,two kinds of insensitive step ladderstructured nitrocellulose(LNC)with different nitrogen contents were synthesized.The products were characterized by FT-IR,Raman,XRD,SEM,elemental analysis,TGA,DSC,accelerating rate calorimeter analysis(ARC),and drop weight test to study their molecular structure,thermal characteristics and desensitization performance.Compared with raw nitrocellulose,LNC has a sharper exothermic peak in the DSC and ARC curves.The H50values of the two kinds of LNC increased from 25.76 to 30.01 cm for low nitrogen content and from 18.02 to 21.84 cm for high nitrogen content,respectively.The results show that the ladder-structure of LNC which provides regular molecular arrangement and a soft buffer made with polyethylene glycol could affect the energy releasing process of LNC and reduce the sensitivity of LNC.Insensitive LNC provides an alternative to be used as a binder in insensitive propellants formulation.展开更多
The high-speed motorized spindle, as the key component of machining centers and other high-end CNC machine tools, has performance directly affecting machining accuracy. According to the internal motor character- istic...The high-speed motorized spindle, as the key component of machining centers and other high-end CNC machine tools, has performance directly affecting machining accuracy. According to the internal motor character- istics of the high speed motorized spindle in the paper, two major heat sources are analyzed and quantity of heat is calculated. The finite element analysis model of motorized spindle thermal characteristics is built through ap- plying the ANSYS Workbench. The thermal steady state, heat-structure coupling characteristics is carried out based on the cooling coefficient of thermal boundary conditions, and taking heating value of the bearing and mo- tor as thermal load, the temperature field distribution and thermal deformation of the spindle system are obtained, which prepare fox" the next thermal error modeling展开更多
Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases co...Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases corresponding to ZnS nanoparticles, PVA and PANI. Field emission scanning electron microscopy shows the formation of agglomerated PANI along the PVA backbone, within which the ZnS nanoparticles are dispersed.UV-visible spectroscopy is conducted to measure the transmittance spectra of samples revealing the electronic absorption characteristics of ZnS and PANI nanoparticles. Photo-acoustic(PA) setup is installed to investigate the thermal properties of samples. The PA spectroscopy indicates a high value of thermal diffusivity for samples due to the presence of ZnS and PANI nanoparticles. Moreover, at higher doses, the more polymerization and formation of PANI and ZnS nanoparticles result in enhancement of thermal diffusivity.展开更多
Towards the end to solve the problem of temperature rise in the power battery of electric vehicles,a method based on the coupling of electrochemical,thermal and hydrodynamic aspects is implemented.The method relies on...Towards the end to solve the problem of temperature rise in the power battery of electric vehicles,a method based on the coupling of electrochemical,thermal and hydrodynamic aspects is implemented.The method relies on the COMSOL Multiphysics software,which is used here to simulate the thermal behaviour,the related fluid-dynamics and the life attenuation of the power battery.A 3D battery model is built assuming a cylindrical geometry.The diameter of the battery is 18 mm,and its length is 65 mm.The battery charges and discharges at 3C,and the initial temperature is 25°C.Intake flow is set to 0.5 m/s after the air of the battery is cooled.The results show that:(1)The highest temperature of the battery unit increases significantly from 1.14°C of the original nylon heat pipe to 0.17°C of the hot pipe core shaft;(2)When the short circuit of the battery is simulated,the temperature rise of the single battery is close to 20°C,the minimum rise is about 12°C,and their difference reaches 8°C.展开更多
Thermal characteristics of Ianthanum heptamolybdate crystals grown by gel technique, employing thermoanalytical techniques, viz. TG, DTA and DSC, are reported. It is established that the rare-earth lanthanum heptamoly...Thermal characteristics of Ianthanum heptamolybdate crystals grown by gel technique, employing thermoanalytical techniques, viz. TG, DTA and DSC, are reported. It is established that the rare-earth lanthanum heptamolybdate crystals are associated with thirty water molecules;the composition being La2Mo7O24.3OH2O. It is shown that all the thirty water molecules associated with lanthanum heptamolybdate crystal are lost during its decomposition, leading to its anhydrous form. Results obtained on application of TG based models, viz. Horowitz-Metzger,Coats-Redfern and Piloyan-Novikova and of DSC based methods viz. Roger-Morris-Smith and Barret, regarding solid state reaction kinetics are also reported. The random nucleation model is shown to be the one that is relevant to the decomposition of lanthanum heptamolybdate. The kinetic parameters, viz.the order of reaction. frquency factor, energy of activation and entropy using above mentioned models are computed and shown to bear reasonably good agreement展开更多
This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be. obtained, the efficient design of magnetizer which produce desired magne...This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be. obtained, the efficient design of magnetizer which produce desired magnet will be possible using our modeling. For field modeling finite-element analysis is used as part of the design and analysis process for magnetizing fixture. The thermal modeling method of magnetizing fixture resistor uses multi-lumped model with equivalent thermal resistance and thermal capacitance.展开更多
Flow control using surface Dielectric Barrier Discharge(DBD)plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry.The induced flow field...Flow control using surface Dielectric Barrier Discharge(DBD)plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry.The induced flow field of the plasma actuator,with the starting vortex in the wall jet,plays an important role in flow control.However,the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator,and most of the total energy is used in gas heating and dielectric heating.Therefore,an in-depth analysis of the thermal characteristics of the plasma actuator is the key to develop its potential capability further.In addition,compared with the investigation on the aerodynamic characteristics of the plasma actuator,there is a relative lack of detail in the study of its thermal characteristics.Understanding the thermal characteristics of the plasma actuator is of great interest for providing a deeper insight into the underlying working principles,advancing its numerical simulation model,prolonging its life,and achieving several potential engineering applications,such as antiicing and deicing.The present paper reviews the thermal characteristics of the plasma actuator,summarizes the influence of the dielectric film and actuation parameters on heating,and discusses the formation and transfer mechanism of the induced heating based on the discharge regimes of the plasma actuator in one cycle.展开更多
The hydronic thermal barrier(HTB)makes the building envelope gradually regarded as a multifunctional element,which is an opportunity to transform thermal insulation solutions from high to zero-carbon attributes.Howeve...The hydronic thermal barrier(HTB)makes the building envelope gradually regarded as a multifunctional element,which is an opportunity to transform thermal insulation solutions from high to zero-carbon attributes.However,inappropriate design,construction,and operation control may lead to issues like low efficiency and high investment,and even the opposite technical effects.In this paper,a comprehensive uncertainty and variable ranking analysis is numerically conducted to explore the influence mechanism of twelve risk variables on three types and five thermal performance indexes under summer conditions.The uncertainty analysis results showed that the correct application of HTB could significantly reduce the heat gain that needs to be handled by the traditional air-conditioning system and even have the technical effect of auxiliary cooling if the variables are appropriately selected.The comprehensive influences of water temperature,room temperature,charging duration,and thermal conductivity of the HTB layer were in the first 1/3 range.Among them,the first two variables were identified as the two most influential variables,and they had a significant mutual restriction relationship in all other four indexes except for the exterior surface cold loss.The recommended charging duration was not less than eight hours in practical application,and the HTB layer with a higher thermal conductivity value but less than 3.3 W/(m·℃)was suggested.Besides,the climate zone was no longer the most influential variable affecting the mean radiant temperature of the interior surface due to the combined effects of HTB and static thermal insulation measures.In addition,pipe spacing should preferably be selected between 100 and 250 mm to help form a continuous thermal buffer zone inside the building envelope.展开更多
In this work,melting of a high-temperature inorganic phase change material(PCM)eutectic(with a melting point of 569℃)within a vertical cylindrical tank has been experimentally investigated.To promote the heat transfe...In this work,melting of a high-temperature inorganic phase change material(PCM)eutectic(with a melting point of 569℃)within a vertical cylindrical tank has been experimentally investigated.To promote the heat transfer rate,a periodic structure that is constructed by a commercial SS-304 mesh screen has been considered and immersed into the PCM tank.Thermal characteristics of the PCM-periodic structure tank under different initial temperatures(450,490 and 546℃)and wall temperatures(620,640,660,680 and 700℃),are then investigated and reported.The presented experimental data can facilitate practical engineers to find the best operating condition of similar PCM tanks;meanwhile,it can also be employed for the investigation of thermal response of transient heat conduction before melting starts.展开更多
The thermal characteristics of high voltage gg-LDMOS under ESD stress conditions are investigated in detail based on the Sentaurus process and device simulators.The total heat and lattice temperature distributions alo...The thermal characteristics of high voltage gg-LDMOS under ESD stress conditions are investigated in detail based on the Sentaurus process and device simulators.The total heat and lattice temperature distributions along the Si–SiO2 interface under different stress conditions are presented and the physical mechanisms are discussed in detail.The influence of structure parameters on peak lattice temperature is also discussed,which is useful for designers to optimize the parameters of LDMSO for better ESD performance.展开更多
In order to solve the conflict between indoor lighting and PV cells in building-integrated photovoltaic/thermal(BIPV/T) systems, a glass curtain wall system based on a tiny transmissive concentrator is proposed. This ...In order to solve the conflict between indoor lighting and PV cells in building-integrated photovoltaic/thermal(BIPV/T) systems, a glass curtain wall system based on a tiny transmissive concentrator is proposed. This glass curtain wall has a direct influence on the heat transfer between indoor and outdoor, and the operating parameters of air and water inlet temperature, indoor and outdoor temperature, and radiation intensity have a significant influence on the heat transfer characteristics of the glass curtain wall. The 3D model is established by SoildWorks software, and the thermal characteristics of the new glass curtain wall system are simulated through computational fluid dynamics(CFD) method. Thermal performance was tested under actual weather for the winter working conditions. The CFD simulation results are verified by the test results under actual weather. The results show that thermal efficiency simulation results are in good agreement with the experimental results of the new glass curtain wall system. The simulation conditions were designed by using the orthogonal method, and the significance analysis of the influencing factors of the indoor wall surface heat gain was carried out. With the increase of the bottom heat flux and the air velocity, the heat absorption of the inner wall surface increases. When the wind speed is 0.1 m/s, the heat flow on the bottom surface rises from 500 W/m^(2) to 2500 W/m^(2), and the heat flow intensity on the interior wall changes from 10.31 W/m^(2) to -29.12 W/m^(2). Under typical working conditions, the new glass curtain wall system can reduce the indoor heat load by 47.5% than ordinary glass curtain wall.展开更多
Architectural shade is an effective method for improving building energy efficiency.A new shade combined with the double skin façade(DSF)system,called middle shade(MS),was introduced and developed for buildings.I...Architectural shade is an effective method for improving building energy efficiency.A new shade combined with the double skin façade(DSF)system,called middle shade(MS),was introduced and developed for buildings.In this paper,a 3D dynamic simulation was conducted to analyze the influence of MS combined with DSF on the indoor thermal characteristics.The research on MS for DSF involves the temperature,the ventilation rate,the velocity distribution of the air flow duct,and the indoor temperature.The results show that the angle and position of the shade in the three seasons are different,and different conditions effectively enhance the indoor thermal characteristics.In summer,the appearance of MS in DSF makes the indoor temperature significantly lower.The indoor temperature is obviously lower than that of the air flow duct,and the temperature of the air flow duct is less affected by MS.The influence of the position of blinds on indoor temperature and ventilation rate is greater than the influence of the angle of blinds.According to the climate characteristics of winter and transition season,in winter,early spring,and late autumn,the indoor temperature decreases with the increase of the position of blinds at daytime,but the opposite is true at night.The results found in this paper can provide reference for the design and use of MS combined with DSF in hot summer and cold winter zone.展开更多
The Letter reports the thermal stability and strain response of Fabry–Perot(FP) cavity under different high temperatures. The FP cavity was made by thermal regeneration of two identical cascaded fiber Bragg gratings(...The Letter reports the thermal stability and strain response of Fabry–Perot(FP) cavity under different high temperatures. The FP cavity was made by thermal regeneration of two identical cascaded fiber Bragg gratings(FBGs). It is demonstrated that the FP cavity is capable of measuring temperatures from 300℃ to 900℃ with a temperature sensitivity of 15.97 pm/℃. The elongation of the fiber was observed through the drifted Bragg wavelength at 700℃ or above when weight was loaded. The elongation was further inferred by the slight change in the interference spectra of the FP cavity at 900℃.展开更多
The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M8 and Af temperatures in Ti5...The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M8 and Af temperatures in Ti50Pd50-xNix, (x=10, 20, 30) alloys, but no obvious thermal cycling effect was observed in Ti50Pd50Pd40Ni10 alloys and the aging effect shows a curious feature, i.e., the Af temperature does not saturate even after relatively long time aging, which is considered to be due to the occurrence of recovery recrystallization during aging.展开更多
Development of graphene field effect transistors (GFETs) faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order ...Development of graphene field effect transistors (GFETs) faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1-5 kΩ/□. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 kΩ/□ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process anneMing on its electrical fabrication.展开更多
The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the cu...The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the current research of the thermal characteristics of machines mainly focuses on steady simulation. To explore the influence of thermal characterizations on the precision of a jib boring machine assembled dual-drive feed system, the thermal equilibrium tests and the research on thermal-mechanical transient behaviors are carried out. A laser interferometer, infrared thermography and a temperature-displacement acquisition system are applied to measure the temperature distribution and thermal deformation at different feed speeds. Subsequently, the finite element method (FEM) is used to analyze the transient thermal behaviors of the boring machine. The complex boundary conditions, such as heat sources and convective heat transfer coefficient, are calculated. Finally, transient variances in temperatures and deformations are compared with the measured values, and the errors between the measurement and the simulation of the temperature and the thermal error are 2 ~C and 2.5 pm, respectively. The researching results demonstrate that the FEM model can predict the thermal error and temperature distribution very well under specified operating condition. Moreover, the uneven temperature gradient is due to the asynchronous dual-drive structure that results in thermal deformation. Additionally, the positioning accuracy decreases as the measured point became further away from the motor, and the thermal error and equilibrium period both increase with feed speeds. The research proposes a systematical method to measure and simulate the boring machine transient thermal behaviors.展开更多
The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron microscopy, and en...The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The con- centmte powder was composed mainly of free chalcopyrite and low quartz in about 3:1 weight ratio. The particle size was about 100 μm. Spectroscopic studies (FTIR, Raman, UV-visible) of the concentrate supported the XRD findings, and also revealed a marginal oxidation of the sulfide phase. The energy band gap of the sulfide was found to be 3.4 eV. Differential thermal analysis and thermogravimetry of the con- centrate showed a decomposition of chalcopyrite at 658 K with an activation energy of 208 kJ-mol 1, and two successive structural changes of silica at 848 K and 1145 K.展开更多
Based on first-principles calculations, Boltzmann transport equation and semiclassical analysis, we conduct a detailed study on the lattice thermal conductivity κL, Seebeck coefficient S, electrical conductivity σ, ...Based on first-principles calculations, Boltzmann transport equation and semiclassical analysis, we conduct a detailed study on the lattice thermal conductivity κL, Seebeck coefficient S, electrical conductivity σ, power factor S2σ and dimensionless figure of merit, zT, for K3IO. It is found that K3IO exhibits relatively low lattice thermal conductivity of 0.93 W·m-1·K-1 at 300 K, which is lower than the value 1.26 W·m-1·K-1 of the classical TE material PbTe. This is due to the smaller phonon group velocity νg and smaller relaxation time τλ. The low lattice thermal conductivity can lead to excellent thermoelectric properties. Thus maximum zT of 2.87 is obtained at 700 K, and the zT = 0.41 at 300 K indicate that K3IO is a potential excellent room temperature TE material. Our research on K3IO shows that it has excellent thermoelectric properties, and it is a promising candidate for applications in fields in terms of thermoelectricity.展开更多
In this paper, the thermal field of double wire welding is simulated by using ANSYS software. Simulation results were shown that the total heat input (E) is the most significant parameters to change the value of t8/5;...In this paper, the thermal field of double wire welding is simulated by using ANSYS software. Simulation results were shown that the total heat input (E) is the most significant parameters to change the value of t8/5;By the mean of rationally controlling the proportion of the front arc heat input (E1) in the total heat input (E) and appropriately selecting double wire spacing (L), It is effective means to get the double wire welding thermal cycle. By the way of simulation, it is possible to manage the thermal input in the double welding wires and to control the temperature field and cooling rate that are fundamental for the final joint quality, it is great importance guidance to optimize the double wire welding process parameters.展开更多
基金This work is supported by the National Natural Science Foundation of China(NSFC,Nos.52176199,and U20A20310)supported by the Program of Shanghai Academic/Technology Research Leader(22XD1423800).
文摘This work extensively investigates the thermal characteristic evolution of lithium-ion batteries under different degradation paths,and the evolution mechanism through multi-angle characterization is revealed.Under different degradation paths,the evolution trend of temperature rise rate remains unchanged with respect to depth of discharge during the adiabatic discharge process,albeit to varying degrees of alteration.The temperature rise rate changes significantly with aging during the adiabatic discharge process under low-temperature cycling and high-rate cycling paths.The total heat generation rate,irreversible heat generation rate,and reversible heat generation rate exhibit similar evolution behavior with aging under different degradation paths.The interval range of endothermic process of reversible electrochemical reactions increases and the contribution of irreversible heat to the total heat increases with aging.To further standardize the assessment of different degradation paths on the thermal characteristics,this work introduces the innovative concept of“Ampere-hour temperature rise”.In low-temperature cycling and high-rate cycling paths,the ampere-hour temperature rise increases significantly with aging,particularly accentuated with higher discharge rates.Conversely,in high-temperature cycling and high-temperature storage paths,the ampere-hour temperature rise remains relatively stable during the initial stages of aging,yet undergoes a notable increase in the later stages of aging.The multi-angle characterization reveals distinct thermal evolution behavior under different degradation paths primarily attributed to different behavior changes of severe side reactions,such as lithium plating.The findings provide crucial insights for the safe utilization and management of lithium–ion batteries throughout the whole lifecycle.
基金supported in part by the National Natural Science Foundation of China(No.22075146)。
文摘Nitrocellulose,or cellulose nitrate,has received considerable interest due to its various applications,such as propellants,coating agents and gas generators.However,its high mechanical sensitivity caused many accidents during its storage and usage in ammunition.In this work,two kinds of insensitive step ladderstructured nitrocellulose(LNC)with different nitrogen contents were synthesized.The products were characterized by FT-IR,Raman,XRD,SEM,elemental analysis,TGA,DSC,accelerating rate calorimeter analysis(ARC),and drop weight test to study their molecular structure,thermal characteristics and desensitization performance.Compared with raw nitrocellulose,LNC has a sharper exothermic peak in the DSC and ARC curves.The H50values of the two kinds of LNC increased from 25.76 to 30.01 cm for low nitrogen content and from 18.02 to 21.84 cm for high nitrogen content,respectively.The results show that the ladder-structure of LNC which provides regular molecular arrangement and a soft buffer made with polyethylene glycol could affect the energy releasing process of LNC and reduce the sensitivity of LNC.Insensitive LNC provides an alternative to be used as a binder in insensitive propellants formulation.
文摘The high-speed motorized spindle, as the key component of machining centers and other high-end CNC machine tools, has performance directly affecting machining accuracy. According to the internal motor character- istics of the high speed motorized spindle in the paper, two major heat sources are analyzed and quantity of heat is calculated. The finite element analysis model of motorized spindle thermal characteristics is built through ap- plying the ANSYS Workbench. The thermal steady state, heat-structure coupling characteristics is carried out based on the cooling coefficient of thermal boundary conditions, and taking heating value of the bearing and mo- tor as thermal load, the temperature field distribution and thermal deformation of the spindle system are obtained, which prepare fox" the next thermal error modeling
文摘Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases corresponding to ZnS nanoparticles, PVA and PANI. Field emission scanning electron microscopy shows the formation of agglomerated PANI along the PVA backbone, within which the ZnS nanoparticles are dispersed.UV-visible spectroscopy is conducted to measure the transmittance spectra of samples revealing the electronic absorption characteristics of ZnS and PANI nanoparticles. Photo-acoustic(PA) setup is installed to investigate the thermal properties of samples. The PA spectroscopy indicates a high value of thermal diffusivity for samples due to the presence of ZnS and PANI nanoparticles. Moreover, at higher doses, the more polymerization and formation of PANI and ZnS nanoparticles result in enhancement of thermal diffusivity.
文摘Towards the end to solve the problem of temperature rise in the power battery of electric vehicles,a method based on the coupling of electrochemical,thermal and hydrodynamic aspects is implemented.The method relies on the COMSOL Multiphysics software,which is used here to simulate the thermal behaviour,the related fluid-dynamics and the life attenuation of the power battery.A 3D battery model is built assuming a cylindrical geometry.The diameter of the battery is 18 mm,and its length is 65 mm.The battery charges and discharges at 3C,and the initial temperature is 25°C.Intake flow is set to 0.5 m/s after the air of the battery is cooled.The results show that:(1)The highest temperature of the battery unit increases significantly from 1.14°C of the original nylon heat pipe to 0.17°C of the hot pipe core shaft;(2)When the short circuit of the battery is simulated,the temperature rise of the single battery is close to 20°C,the minimum rise is about 12°C,and their difference reaches 8°C.
文摘Thermal characteristics of Ianthanum heptamolybdate crystals grown by gel technique, employing thermoanalytical techniques, viz. TG, DTA and DSC, are reported. It is established that the rare-earth lanthanum heptamolybdate crystals are associated with thirty water molecules;the composition being La2Mo7O24.3OH2O. It is shown that all the thirty water molecules associated with lanthanum heptamolybdate crystal are lost during its decomposition, leading to its anhydrous form. Results obtained on application of TG based models, viz. Horowitz-Metzger,Coats-Redfern and Piloyan-Novikova and of DSC based methods viz. Roger-Morris-Smith and Barret, regarding solid state reaction kinetics are also reported. The random nucleation model is shown to be the one that is relevant to the decomposition of lanthanum heptamolybdate. The kinetic parameters, viz.the order of reaction. frquency factor, energy of activation and entropy using above mentioned models are computed and shown to bear reasonably good agreement
文摘This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be. obtained, the efficient design of magnetizer which produce desired magnet will be possible using our modeling. For field modeling finite-element analysis is used as part of the design and analysis process for magnetizing fixture. The thermal modeling method of magnetizing fixture resistor uses multi-lumped model with equivalent thermal resistance and thermal capacitance.
基金support by the National Natural Science Foundation of China(No.11902336)State Key Laboratory of Aerodynamics Foundation of China(Nos.SKLA2019020201,JBKYC190103)+1 种基金CARDC Fundamental and Frontier Technology Research Fund,China(No.PJD20180144)China Scholarship Council.
文摘Flow control using surface Dielectric Barrier Discharge(DBD)plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry.The induced flow field of the plasma actuator,with the starting vortex in the wall jet,plays an important role in flow control.However,the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator,and most of the total energy is used in gas heating and dielectric heating.Therefore,an in-depth analysis of the thermal characteristics of the plasma actuator is the key to develop its potential capability further.In addition,compared with the investigation on the aerodynamic characteristics of the plasma actuator,there is a relative lack of detail in the study of its thermal characteristics.Understanding the thermal characteristics of the plasma actuator is of great interest for providing a deeper insight into the underlying working principles,advancing its numerical simulation model,prolonging its life,and achieving several potential engineering applications,such as antiicing and deicing.The present paper reviews the thermal characteristics of the plasma actuator,summarizes the influence of the dielectric film and actuation parameters on heating,and discusses the formation and transfer mechanism of the induced heating based on the discharge regimes of the plasma actuator in one cycle.
基金This study is co-sponsored by the Open Project Program of Engineering Research Center of Building Energy Efficiency Control and Evaluation,Ministry of Education(No.AHJZNX202103)Youth Fund of Anhui Natural Science Foundation(No.2208085QE163,No.2108085QE241)+3 种基金Fundamental Research Funds for the Central Universities(No.JZ2022HGTA0336,No.JZ2022HGQA0173)Natural Science Research Program of Anhui Colleges(No.KJ2020A0462)Scientific Research and Cultivation Project of Anhui Jianzhu University(No.2021XMK04)Open Project Program of Anhui Academy of Territory Space Planning and Ecology(No.GTY2021202).
文摘The hydronic thermal barrier(HTB)makes the building envelope gradually regarded as a multifunctional element,which is an opportunity to transform thermal insulation solutions from high to zero-carbon attributes.However,inappropriate design,construction,and operation control may lead to issues like low efficiency and high investment,and even the opposite technical effects.In this paper,a comprehensive uncertainty and variable ranking analysis is numerically conducted to explore the influence mechanism of twelve risk variables on three types and five thermal performance indexes under summer conditions.The uncertainty analysis results showed that the correct application of HTB could significantly reduce the heat gain that needs to be handled by the traditional air-conditioning system and even have the technical effect of auxiliary cooling if the variables are appropriately selected.The comprehensive influences of water temperature,room temperature,charging duration,and thermal conductivity of the HTB layer were in the first 1/3 range.Among them,the first two variables were identified as the two most influential variables,and they had a significant mutual restriction relationship in all other four indexes except for the exterior surface cold loss.The recommended charging duration was not less than eight hours in practical application,and the HTB layer with a higher thermal conductivity value but less than 3.3 W/(m·℃)was suggested.Besides,the climate zone was no longer the most influential variable affecting the mean radiant temperature of the interior surface due to the combined effects of HTB and static thermal insulation measures.In addition,pipe spacing should preferably be selected between 100 and 250 mm to help form a continuous thermal buffer zone inside the building envelope.
文摘In this work,melting of a high-temperature inorganic phase change material(PCM)eutectic(with a melting point of 569℃)within a vertical cylindrical tank has been experimentally investigated.To promote the heat transfer rate,a periodic structure that is constructed by a commercial SS-304 mesh screen has been considered and immersed into the PCM tank.Thermal characteristics of the PCM-periodic structure tank under different initial temperatures(450,490 and 546℃)and wall temperatures(620,640,660,680 and 700℃),are then investigated and reported.The presented experimental data can facilitate practical engineers to find the best operating condition of similar PCM tanks;meanwhile,it can also be employed for the investigation of thermal response of transient heat conduction before melting starts.
基金supported by the Natural Science Foundation of the Jiangsu Province(No.BK2008287)the Advanced Research of National Natural Science Foundation of Southeast University(No.XJ2008312)
文摘The thermal characteristics of high voltage gg-LDMOS under ESD stress conditions are investigated in detail based on the Sentaurus process and device simulators.The total heat and lattice temperature distributions along the Si–SiO2 interface under different stress conditions are presented and the physical mechanisms are discussed in detail.The influence of structure parameters on peak lattice temperature is also discussed,which is useful for designers to optimize the parameters of LDMSO for better ESD performance.
基金supported by the National Natural Science Foundation of China(51766013,51766012)the Inner Mongolia Natural Science Foundation of China(2020LH05014,2019MS05025)the Inner Mongolia Science and Technology Major Project in 2019。
文摘In order to solve the conflict between indoor lighting and PV cells in building-integrated photovoltaic/thermal(BIPV/T) systems, a glass curtain wall system based on a tiny transmissive concentrator is proposed. This glass curtain wall has a direct influence on the heat transfer between indoor and outdoor, and the operating parameters of air and water inlet temperature, indoor and outdoor temperature, and radiation intensity have a significant influence on the heat transfer characteristics of the glass curtain wall. The 3D model is established by SoildWorks software, and the thermal characteristics of the new glass curtain wall system are simulated through computational fluid dynamics(CFD) method. Thermal performance was tested under actual weather for the winter working conditions. The CFD simulation results are verified by the test results under actual weather. The results show that thermal efficiency simulation results are in good agreement with the experimental results of the new glass curtain wall system. The simulation conditions were designed by using the orthogonal method, and the significance analysis of the influencing factors of the indoor wall surface heat gain was carried out. With the increase of the bottom heat flux and the air velocity, the heat absorption of the inner wall surface increases. When the wind speed is 0.1 m/s, the heat flow on the bottom surface rises from 500 W/m^(2) to 2500 W/m^(2), and the heat flow intensity on the interior wall changes from 10.31 W/m^(2) to -29.12 W/m^(2). Under typical working conditions, the new glass curtain wall system can reduce the indoor heat load by 47.5% than ordinary glass curtain wall.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51408184)Tianjin Natural Science Foundation(15JCQNJC07800)Excellent Youth Foundation of Hebei Educational Committee(YQ2014005).
文摘Architectural shade is an effective method for improving building energy efficiency.A new shade combined with the double skin façade(DSF)system,called middle shade(MS),was introduced and developed for buildings.In this paper,a 3D dynamic simulation was conducted to analyze the influence of MS combined with DSF on the indoor thermal characteristics.The research on MS for DSF involves the temperature,the ventilation rate,the velocity distribution of the air flow duct,and the indoor temperature.The results show that the angle and position of the shade in the three seasons are different,and different conditions effectively enhance the indoor thermal characteristics.In summer,the appearance of MS in DSF makes the indoor temperature significantly lower.The indoor temperature is obviously lower than that of the air flow duct,and the temperature of the air flow duct is less affected by MS.The influence of the position of blinds on indoor temperature and ventilation rate is greater than the influence of the angle of blinds.According to the climate characteristics of winter and transition season,in winter,early spring,and late autumn,the indoor temperature decreases with the increase of the position of blinds at daytime,but the opposite is true at night.The results found in this paper can provide reference for the design and use of MS combined with DSF in hot summer and cold winter zone.
基金supported by the Program for Changjiang Scholars and Innovative Research Team in the University of Ministry of Education of China(No.IRT_16R07)the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions(No.IDHT20170510)
文摘The Letter reports the thermal stability and strain response of Fabry–Perot(FP) cavity under different high temperatures. The FP cavity was made by thermal regeneration of two identical cascaded fiber Bragg gratings(FBGs). It is demonstrated that the FP cavity is capable of measuring temperatures from 300℃ to 900℃ with a temperature sensitivity of 15.97 pm/℃. The elongation of the fiber was observed through the drifted Bragg wavelength at 700℃ or above when weight was loaded. The elongation was further inferred by the slight change in the interference spectra of the FP cavity at 900℃.
基金This work was supported by a Grant-in-Aid fOrEncouragement of Young Scientists (W.C.) (l998-1999) from the Ministry of Educat
文摘The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M8 and Af temperatures in Ti50Pd50-xNix, (x=10, 20, 30) alloys, but no obvious thermal cycling effect was observed in Ti50Pd50Pd40Ni10 alloys and the aging effect shows a curious feature, i.e., the Af temperature does not saturate even after relatively long time aging, which is considered to be due to the occurrence of recovery recrystallization during aging.
文摘Development of graphene field effect transistors (GFETs) faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1-5 kΩ/□. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 kΩ/□ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process anneMing on its electrical fabrication.
基金Supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2012AA040701)
文摘The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the current research of the thermal characteristics of machines mainly focuses on steady simulation. To explore the influence of thermal characterizations on the precision of a jib boring machine assembled dual-drive feed system, the thermal equilibrium tests and the research on thermal-mechanical transient behaviors are carried out. A laser interferometer, infrared thermography and a temperature-displacement acquisition system are applied to measure the temperature distribution and thermal deformation at different feed speeds. Subsequently, the finite element method (FEM) is used to analyze the transient thermal behaviors of the boring machine. The complex boundary conditions, such as heat sources and convective heat transfer coefficient, are calculated. Finally, transient variances in temperatures and deformations are compared with the measured values, and the errors between the measurement and the simulation of the temperature and the thermal error are 2 ~C and 2.5 pm, respectively. The researching results demonstrate that the FEM model can predict the thermal error and temperature distribution very well under specified operating condition. Moreover, the uneven temperature gradient is due to the asynchronous dual-drive structure that results in thermal deformation. Additionally, the positioning accuracy decreases as the measured point became further away from the motor, and the thermal error and equilibrium period both increase with feed speeds. The research proposes a systematical method to measure and simulate the boring machine transient thermal behaviors.
文摘The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The con- centmte powder was composed mainly of free chalcopyrite and low quartz in about 3:1 weight ratio. The particle size was about 100 μm. Spectroscopic studies (FTIR, Raman, UV-visible) of the concentrate supported the XRD findings, and also revealed a marginal oxidation of the sulfide phase. The energy band gap of the sulfide was found to be 3.4 eV. Differential thermal analysis and thermogravimetry of the con- centrate showed a decomposition of chalcopyrite at 658 K with an activation energy of 208 kJ-mol 1, and two successive structural changes of silica at 848 K and 1145 K.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974302,11774396,and 11704322)the Shandong Natural Science Funds for Doctoral Program,China(Grant No.ZR2017BA017).
文摘Based on first-principles calculations, Boltzmann transport equation and semiclassical analysis, we conduct a detailed study on the lattice thermal conductivity κL, Seebeck coefficient S, electrical conductivity σ, power factor S2σ and dimensionless figure of merit, zT, for K3IO. It is found that K3IO exhibits relatively low lattice thermal conductivity of 0.93 W·m-1·K-1 at 300 K, which is lower than the value 1.26 W·m-1·K-1 of the classical TE material PbTe. This is due to the smaller phonon group velocity νg and smaller relaxation time τλ. The low lattice thermal conductivity can lead to excellent thermoelectric properties. Thus maximum zT of 2.87 is obtained at 700 K, and the zT = 0.41 at 300 K indicate that K3IO is a potential excellent room temperature TE material. Our research on K3IO shows that it has excellent thermoelectric properties, and it is a promising candidate for applications in fields in terms of thermoelectricity.
文摘In this paper, the thermal field of double wire welding is simulated by using ANSYS software. Simulation results were shown that the total heat input (E) is the most significant parameters to change the value of t8/5;By the mean of rationally controlling the proportion of the front arc heat input (E1) in the total heat input (E) and appropriately selecting double wire spacing (L), It is effective means to get the double wire welding thermal cycle. By the way of simulation, it is possible to manage the thermal input in the double welding wires and to control the temperature field and cooling rate that are fundamental for the final joint quality, it is great importance guidance to optimize the double wire welding process parameters.