A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids....A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).展开更多
Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively ...Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively volume heated as part of a fast capacitor discharge circuit. Time resolved measurements with sub-μs resolution of current through the specimen are performed with a Pearson probe, voltage drop across the specimen is measured with knife-edge contacts and ohmic voltage dividers and the radiance temperature of the sample with a pyrometer. These measurements allow to determine heat of fusion as well as heat capacity and electrical resistivity at initial geometry of Nimonic 80A as a function of temperature in the solid and in the liquid phase up to 2400 K.展开更多
Two quinary high-entropy alloys (HEAs) with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entr...Two quinary high-entropy alloys (HEAs) with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning cMorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face- centered cubic high-entropy phase plus a minor interdendritic (Cu) phase and display a lower entropy of fasion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubie high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are signitieantly larger than those of the latter At-doped M1oy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860-912 K.展开更多
In a previous paper it was shown that the normal spectral emissivity at 684.5 nm of a binary alloy can be lower than that of the pure constituent components. For the actual probes it was found that the observed values...In a previous paper it was shown that the normal spectral emissivity at 684.5 nm of a binary alloy can be lower than that of the pure constituent components. For the actual probes it was found that the observed values of normal spectral emissivity of the alloys are in between or higher than those of the pure constituent components. Experiments were conducted on the alloy systems Ni-Ti and Au-Ni. Their emissivity as well as electrical resistivity and enthalpy as a function of temperature is presented.展开更多
The thermophysical properties of API 5L X80 steel were experimentally measured, in order to use these in computational models to determine the temperature field in welded joints. In this work, values of thermal expans...The thermophysical properties of API 5L X80 steel were experimentally measured, in order to use these in computational models to determine the temperature field in welded joints. In this work, values of thermal expansion coefficient, specific heat, thermal diffusivity and thermal conductivity were experimentally obtained as a function of temperature. The thermal expansion coefficient was determined at temperatures of 20°C to 1200°C in a dilatometer DIL 402 PC. The specific heat was determined on a differential scanning calorimeter at temperatures between 300°C and 1200°C. The diffusivity and thermal conductivity were determined in the temperature range 100°C to 800°C in a 457 LFA diffusivimeter using laser flash technique. The thermal expansion coefficient remained approximately with constant value of 8.5 × 10-6 K-1 and suffered two falls reaching values -25 × 10-6 K-1 and -50 × 10-6 K-1 in the stages of heating and cooling respectively. It was observed for this material, minimum and maximum values of specific heat equal to 0.571 J/gK and 1.084 J/gK at temperatures of 300°C and 720°C, respectively. The behavior of thermal diffusivity and thermal conductivity in the temperature range 100°C to 800°C tends to decrease with increasing temperature. Based on the measured properties, computational modeling of the temperature field can be numerically obtained with better accuracy.展开更多
The influence of pressure and temperature on the thermodynamic properties of MgCu intermetallic compound was investigated by quasi-harmonic Debye model approximation.The equation of state(EoS)parameters has performed ...The influence of pressure and temperature on the thermodynamic properties of MgCu intermetallic compound was investigated by quasi-harmonic Debye model approximation.The equation of state(EoS)parameters has performed using plane-wave pseudopotential(PW-PP)approach in the framework of the density functional theory(DFT)and the generalized gradient approximation(GGA)for the exchange-correlation functional.Our results agree well with other data of the literature.The finite temperature thermophysical properties under pressure up to 16 GPa and high temperature up to 800 K,respectively were determined.Our results of the thermophysical properties are also agree very well with other data of the literature,where for example at ambient temperature,the deviation between our obtained value(11.05 Cal mol^(−1)K^(−1))of C V,and the theoretical value(11.21 Cal mol^(−1)K^(−1))reported in the literature is only around 1.44%.The finite temperature thermophysical properties were found varied monotonically with either temperature or pressure.Compared with other materials previously studied,similar behaviors were observed.展开更多
A good understanding of the thermophysical properties of hydrocarbon fuels at supercritical pressure is important to research on experiment and numerical simulation of fuel supercritical spray.Experimental measurement...A good understanding of the thermophysical properties of hydrocarbon fuels at supercritical pressure is important to research on experiment and numerical simulation of fuel supercritical spray.Experimental measurements are difficult to conduct directly because of the extremely high pressure and high temperature.In this study,back propagation(BP)neural network,BP optimized by mind evolution algorithm(MEA-BP)and BP neural network optimized by genetic algorithm(GA-BP)are established to determine the nonlinear temperature-dependent thermophysical properties of density,viscosity,and isobaric specific heat(C_(2))of hydrocarbon fuels at supercritical pressure.Meanwhile,approximate formulas for these properties prediction are primarily proposed using polynomial fitting.In this paper,models that can predict three types of physical properties of three kinds of hydrocarbon fuels and their mixtures in a wide temperature range under supercritical pressure are established.In the prediction of density and C_(2),BP neural network has a good prediction effect.The results show that the MAPE is lower than 2%in the prediction of density and C_(2),but the MAPE of viscosity prediction is slightly higher than 5%using BP.Furthermore,MEA and GA are used to optimize the prediction of viscosity.The optimization effect and computation of the MEA is better than that of GA because MEA does not have the local optimization and prematurity problems.The present work offers an efficient tool to predict the thermophysical properties of hydrocarbon fuels over a wide range of temperatures under supercritical pressure which can be easily extended to other fuels of interest.It will be beneficial to the experiment and numerical simulation studies of supercritical sprays.展开更多
The paper presents the results of a comprehensive study of the thermophysical properties(thermal conductivity,thermal diffusivity,heat capacity)of high-temperature multiferroic BiFeO_(3) modified with rare-earth eleme...The paper presents the results of a comprehensive study of the thermophysical properties(thermal conductivity,thermal diffusivity,heat capacity)of high-temperature multiferroic BiFeO_(3) modified with rare-earth elements(REEs)(La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Lu).The regularities of the formation of the mentioned characteristics were established.The assumptions about the nature of the observed phenomena were suggested.展开更多
A program CALTPP(CALculation of ThermoPhysical Properties)is developed in order to provide various thermophysical properties such as diffusion coefficient,interfacial energy,thermal conductivity,viscosity and molar vo...A program CALTPP(CALculation of ThermoPhysical Properties)is developed in order to provide various thermophysical properties such as diffusion coefficient,interfacial energy,thermal conductivity,viscosity and molar volume mainly as function of temperature and composition.These thermophysical properties are very important inputs for microstructure simulations and mechanical property predictions.The general structure of CALTPP is briefly described,and the CALPHAD-type models for the description of these thermophysical properties are presented.The CALTPP program contains the input module,calculation and/or optimization modules and output module.A few case studies including(a)the calculation of diffusion coefficient and optimization of atomic mobility,(b)the calculation of solid/liquid,coherent solid/solid and liquid/liquid interfacial energies,(c)the calculation of thermal conductivity,(d)the calculation of viscosity,and(e)the establishment of molar volume database in binary and ternary alloys are demonstrated to show the features of CALTPP.It is expected that CALTPP will be an effective contribution in both scientific research and education.展开更多
With the increasing requirements for fast charging and discharging,higher requirements have been put forward for the thermal management of power batteries.Therefore,there is an urgent need to develop efficient heat tr...With the increasing requirements for fast charging and discharging,higher requirements have been put forward for the thermal management of power batteries.Therefore,there is an urgent need to develop efficient heat transfer fluids.As a new type of heat transfer fluids,functional thermal fluids mainly includ-ing nanofluids(NFs)and phase change fluids(PCFs),have the advantages of high heat carrying density,high heat transfer rate,and broad operational temperature range.However,challenges that hinder their practical applications remain.In this paper,we firstly overview the classification,thermophysical prop-erties,drawbacks,and corresponding modifications of functional thermal fluids.For NFs,the high ther-mal conductivity and high convective heat transfer performance were mainly elaborated,while the stability and viscosity issues were also analyzed.And then for PCFs,the high heat carrying density was mainly elaborated,while the problems of supercooling,stability,and viscosity were also analyzed.On this basis,the composite fluids combined NFs and PCFs technology,has been summarized.Furthermore,the thermal properties of traditional fluids,NFs,PCFs,and composite fluids are compared,which proves that functional thermal fluids are a good choice to replace traditional fluids as coolants.Then,battery thermal management system(BTMS)based on functional thermal fluids is summarized in detail,and the thermal management effects and pump consumption are compared with that of water-based BTMS.Finally,the current technical challenges that parameters optimization of functional thermal fluids and structures optimization of BTMS systematically are presented.In the future,it is necessary to pay more attention to using machine learning to predict thermophysical properties of functional thermal fluids and their applications for BTMS under actual vehicle conditions.展开更多
As a ceramic material,AlN has very good thermophysical and mechanical properties.In addition,AlN is an effective refining agent for Mg alloys because it has a lattice constant similar to that of Mg.Therefore,AlN is an...As a ceramic material,AlN has very good thermophysical and mechanical properties.In addition,AlN is an effective refining agent for Mg alloys because it has a lattice constant similar to that of Mg.Therefore,AlN is an ideal reinforcement for magnesium matrix composites(MMCs),and is attracting increasing attention.This review addresses the development of preparation technologies for AlN-reinforced Mg matrix composites.The mainstream preparation techniques include stir casting,melt infiltration,powder metallurgy,and in-situ methods.In addition,the advantages and disadvantages of these techniques are analyzed in depth,and it is pointed out that the next direction for the preparation of high-performance AlN-reinforced MMCs is less aluminization and multiple technologies integration.展开更多
In this work,we have investigated the rotating effect on the thermodynamic properties of a 2D quantum ring.Accordingly,we have considered the radial potential of a 2D quantum ring and solved the Schrödinger equat...In this work,we have investigated the rotating effect on the thermodynamic properties of a 2D quantum ring.Accordingly,we have considered the radial potential of a 2D quantum ring and solved the Schrödinger equation in the presence of the Aharonov-Bohm effect and a uniform magnetic field for the considered potential.According to the solution of the equation,we calculated the eigenvalues and eigenfunctions of the considered system.Using the calculated energy spectrum,we obtained the partition function and thermodynamic properties of the system,such as the mean energy,specific heat,entropy and free energy.Our results show that the rotating effect has a significant influence on the thermophysical properties of a 2D quantum ring.We also study other effects of the rotating term:(1)the effect of different values of rotating parameters,and(2)the effect of negative rotation on the thermodynamic properties of the system.Our results are discussed in detail.展开更多
Thermophysical parameters are the main parameters affecting the utilization efficiency of shallow geothermal energy. Based on the research and evaluation data of shallow geothermal energy in capital cities of China, t...Thermophysical parameters are the main parameters affecting the utilization efficiency of shallow geothermal energy. Based on the research and evaluation data of shallow geothermal energy in capital cities of China, this paper analyzes the differences between two testing methods and finds that data measured in in-situ thermal conductivity test is closer to the actual utilization. This paper analyzes the influencing factors of thermophysical parameters from lithology, density, moisture content and porosity: The thermal conductivity coefficient of bedrock is generally higher than Quaternary system loose bed soil; as for the coefficient of bedrock, dolomite, shale and granite are higher while gabbro, sandstone and mudstone are lower; as for the coefficient of loose bed, pebble and gravel are higher while clay and silt are lower. As the particle size of sand decreases, the thermal conductivity coefficient declines accordingly. The thermal conductivity coefficient increases linearly with growing density and decreases in logarithm with growing moisture content as well as porosity; specific heat capacity decreases in logarithm with growing density, increases in power exponent with growing moisture content and decreases linearly with growing porosity. The thermal conductivity coefficient is high when hydrodynamic condition is good and vice versa. The conclusions of this paper have guiding significance for the research, evaluation and development of shallow geothermal energy in other areas.展开更多
We prepared the nano-inorganic phase-change "alloy" materials through the modification of Na2SO4·10H2O using Na2HPO4·12H2O and GO nano-nucleating agent, and further investigated their thermophysical proper...We prepared the nano-inorganic phase-change "alloy" materials through the modification of Na2SO4·10H2O using Na2HPO4·12H2O and GO nano-nucleating agent, and further investigated their thermophysical properties such as melting/solidification temperatures and enthalpies via differential scanning calorimetry. When the weight ratio of Na2SO4·10H2O and Na2HPO4·12H2O was 8:2 and the weight ratio of graphene oxide was 0.5% of phase change material, the phase change "alloy" material showed excellent performances, specifically, the melting temperature and latent heat were found to be 22 ℃ and 190 J/g with a degree of subcooling decreased from 8.6℃ to 2.1℃. In order to extend the application of the phase change "alloy" material to building energy saving field, it was adsorbed on expanded glass beads under vacuum and further covered with diatomite. When the adsorption rate of EGB(volume) and PCAM(weight) was 2.5:1, the particle size of diatomaceous earth was found to be 3.6μm, while the best packaging result was obtained with the melting temperature and latent heat being 21℃ and 135 J/g, and no leakage was observed.展开更多
During both hot and cold seasons,masonry walls play an important role in the thermal performance between the interior and the exterior of occupied spaces.It is thus essential to analyze the thermal behavior at the hol...During both hot and cold seasons,masonry walls play an important role in the thermal performance between the interior and the exterior of occupied spaces.It is thus essential to analyze the thermal behavior at the hollow block’s level in order to better understand the temperature and heat flux distribution in its structure and potentially limit as much as possible the heat transfer through the block.In this scope,this paper offers an experimental and numerical in-depth analysis of heat transfer phenomena inside a hollow block using a dedicated experimental setup including a well-insulated reference box and several thermocouples and fluxmeters distributed at the boundaries and inside the hollow block.The block was then numerically 3D modelled and simulated using COMSOL Multiphysics under the same conditions,properties,and dimensions as the experimentally tested block.The comparison between the numerical and experimental results provides very satisfactory results with relative difference of less than 4%for the computed thermal resistance.展开更多
A transient method with rectangular pulse heating has been developed to measure the thermal conductivity of highly porous materials such as activated carbon, zeolite and silica gel. By this method the thermal conducti...A transient method with rectangular pulse heating has been developed to measure the thermal conductivity of highly porous materials such as activated carbon, zeolite and silica gel. By this method the thermal conductivity can be measured quickly and accu-rately. In this paper, a set of automatically controlled testing equiptnent is presented.The measuring method is analysed. The thermal conductivities of some samples, such as activated carbon and zeolite, are measured by the equipment. A group of useful data has been obtained.展开更多
The generation and evaluation of severely high thermal stress(σ)is known to be responsible for failure of thermal barrier coatings(TBCs)during thermal cycling.It is crucial and challenging to capture fluctuations in...The generation and evaluation of severely high thermal stress(σ)is known to be responsible for failure of thermal barrier coatings(TBCs)during thermal cycling.It is crucial and challenging to capture fluctuations inσcaused by the phase transition,which has motivated us to develop a high-throughput multiscale evaluation method forσin TBCs that considers the phase transition of the top ceramic materials by coupling first-principles calculations with finite element simulations.The method quantitatively evaluates and visualizesσof the real TBC structure under thermal cycling by multifield coupling.Additionally,the thermophysical properties calculated by the first-principles calculations consider the effects of temperature and phase transition,which not only reduces the cost of obtaining data but also has a more physical connotation.In this work,rare earth tantalites(RETaO4)are introduced as ceramic layers,and the results demonstrate thatσundergoes a rapid escalation near the phase transition temperature(Tt),particularly in the TBCs_GdTaO4 system,where it rises from 224 to 435 MPa.This discontinuity inσmay originate from the significant alterations in Young’s modulus(increase by 27%–78%)and thermal conductivity(increase by 53%–146%)near Tt.The TBCs_NdTaO4 and TBCs_SmTaO4 systems exhibit noteworthy temperature drop gradients and minimalσfluctuations,which are beneficial for extending service lifetime of TBCs.This approach facilitates the prediction of failure mechanisms and provides theoretical guidance for the reverse design of TBC materials to obtain low thermal stress systems.展开更多
Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) a...Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) alloy.The liquid Ti_(85)Ni_(10)Al_(5) alloy was substantially undercooled up to 335 K(0.18T_(L)).As undercooling increased,the potential energy of the liquid alloy decreased and the alloy entered into a high metastable state.At this state,the atoms tended to bond with each other and the clusters were inclined to convert into high-coordinated clusters,as confirmed by the fraction of the high-coordinated clusters variation.The enlarged clusters and enhanced local structure stability contributed to the increase of the thermophysical parameters and crystal growth velocity,and eventually dendrite refinement.The density,the specific heat and the surface tension of liquid alloy exhibited a linear relation with temperature and the shear viscosity of liquid alloy showed exponential variation which showed good agreement with the calculation results by molecular dynamics simulation.The growth velocity first increased slowly and then dramatically once the undercooling exceeded the threshold.The achieved maximum crystal growth velocity was 12.4 m s^(−1) and it was up to 326 times of the value at 94 K undercooling.展开更多
Thermophysical analysis of the crustal rocks is important for heat transfer determination and insulation purposes to save energy in buildings.In the presented work,thermophysical properties of four limestones were inv...Thermophysical analysis of the crustal rocks is important for heat transfer determination and insulation purposes to save energy in buildings.In the presented work,thermophysical properties of four limestones were investigated in dry and moist state under ambient conditions by using a transient plane source method.A thermal constant analyzer was used to raise the sample temperature and to measure the thermal properties in the temperature range of 300 K to 433 K.Thermal conductivity and diffusivity were measured by developing a linear relationship between temperature response of TPS (transient plane source) sensor and dimensionless time function through least-square fitting method.The experimental observations and predicted thermal conductivity of samples have shown that in-situ observations are important to determine the thermal properties accurately.The effect of temperature on thermal properties of limestone was defined by considering the chemical composition of the samples and associated heat transfer mechanism.Both thermal conductivity and diffusivity of limestone decreased while specific heat capacity increased with a rise in temperature.The overall findings indicate that the spinoff of this research is useful in studying the reliance of thermophysical properties of rocks on their structures and lithology.展开更多
Nd_9Fe_(85–x)Ti_4C_2B_x(x=10–15) magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, ...Nd_9Fe_(85–x)Ti_4C_2B_x(x=10–15) magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, the liquidus temperatures TL of the alloys decreased from 1498.5 to 1472.5 K; the solidus temperatures TS of them increased from 1353.2 to 1358.3 K; and the nucleation undercooling of the alloy melts cooled at the rate of 40 K/min decreased from 122.8 to 95.9 K, resulting in the solidification structures consisting of Nd_2Fe_(14)B, Fe_3B, α-Fe, Nd1.1Fe4B4 and TiC nanocrystallines. Furthermore, the Nd_9Fe_(85–x)Ti_4C_2B_x(x=11, 13, 15) bulk alloys in sheet form with the thickness of 0.7 mm were prepared by copper mold suction casting and their solidification characteristics and solidification structures under sub-rapidly cooling rate were investigated. The results showed that partially amorphous structures were obtained in the as-cast bulk alloys and the amount of amorphous decreased with the increase of the B content. By annealing the as-cast bulk alloys at 923 K for 10 min, the nanocomposite microstructures composed with Nd_2Fe_(14)B, Fe_3B and α-Fe nanocrystallines, which showed a single-phase hard magnetic behavior and enhanced magnetic properties, were achieved.展开更多
文摘A possible way to increase thermal conductivity of working fluids, while keeping pressure drop at acceptable levels, is through nanofluids. Nanofluids are nano-sized particles dispersed in conventional working fluids. A great number of materials have potential to be used in nanoparticles production and then in nanofluids;one of them is Multi-Walled Carbon Nano Tubes (MWCNT). They have thermal conductivity around 3000 W/mK while other materials used as nanoparticles like CuO have thermal conductivity of 76.5 W/mK. Due to this fact, MWCNT nanoparticles have potential to be used in nanofluids production, aiming to increase heat transfer rate in energy systems. In this context, the main goal of this paper is to evaluate from the synthesis to the experimental measurement of thermal conductivity of nanofluid samples based on functionalized (-OH) MWCNT nanoparticles. They will be analyzed nanoparticles with different functionalization degrees (4% wt, 6% wt, and 9% wt). In addition, it will be quantified other thermophysical properties (dynamic viscosity, specific heat and specific mass) of the synthetized nanofluids. So, the present work can contribute with experimental data that will help researches in the study and development of MWCNT nanofluids. According to the results, the maximum increment obtained in thermal conductivity was 10.65% in relation to the base fluid (water).
基金This work was financially supported by the Austrian "Forschungsfrderungsgesellschaft mbH", Krntner Strasse 21-23, 1010 Vienna, under contract No. 810999.
文摘Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively volume heated as part of a fast capacitor discharge circuit. Time resolved measurements with sub-μs resolution of current through the specimen are performed with a Pearson probe, voltage drop across the specimen is measured with knife-edge contacts and ohmic voltage dividers and the radiance temperature of the sample with a pyrometer. These measurements allow to determine heat of fusion as well as heat capacity and electrical resistivity at initial geometry of Nimonic 80A as a function of temperature in the solid and in the liquid phase up to 2400 K.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51571163,51371150,51271150 and 51327901
文摘Two quinary high-entropy alloys (HEAs) with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning cMorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face- centered cubic high-entropy phase plus a minor interdendritic (Cu) phase and display a lower entropy of fasion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubie high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are signitieantly larger than those of the latter At-doped M1oy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860-912 K.
基金This work is financially supported by the "Austrian Science Fund - FWF", Sensengasse 1, 1090 Vienna, under contract No. P15055
文摘In a previous paper it was shown that the normal spectral emissivity at 684.5 nm of a binary alloy can be lower than that of the pure constituent components. For the actual probes it was found that the observed values of normal spectral emissivity of the alloys are in between or higher than those of the pure constituent components. Experiments were conducted on the alloy systems Ni-Ti and Au-Ni. Their emissivity as well as electrical resistivity and enthalpy as a function of temperature is presented.
文摘The thermophysical properties of API 5L X80 steel were experimentally measured, in order to use these in computational models to determine the temperature field in welded joints. In this work, values of thermal expansion coefficient, specific heat, thermal diffusivity and thermal conductivity were experimentally obtained as a function of temperature. The thermal expansion coefficient was determined at temperatures of 20°C to 1200°C in a dilatometer DIL 402 PC. The specific heat was determined on a differential scanning calorimeter at temperatures between 300°C and 1200°C. The diffusivity and thermal conductivity were determined in the temperature range 100°C to 800°C in a 457 LFA diffusivimeter using laser flash technique. The thermal expansion coefficient remained approximately with constant value of 8.5 × 10-6 K-1 and suffered two falls reaching values -25 × 10-6 K-1 and -50 × 10-6 K-1 in the stages of heating and cooling respectively. It was observed for this material, minimum and maximum values of specific heat equal to 0.571 J/gK and 1.084 J/gK at temperatures of 300°C and 720°C, respectively. The behavior of thermal diffusivity and thermal conductivity in the temperature range 100°C to 800°C tends to decrease with increasing temperature. Based on the measured properties, computational modeling of the temperature field can be numerically obtained with better accuracy.
文摘The influence of pressure and temperature on the thermodynamic properties of MgCu intermetallic compound was investigated by quasi-harmonic Debye model approximation.The equation of state(EoS)parameters has performed using plane-wave pseudopotential(PW-PP)approach in the framework of the density functional theory(DFT)and the generalized gradient approximation(GGA)for the exchange-correlation functional.Our results agree well with other data of the literature.The finite temperature thermophysical properties under pressure up to 16 GPa and high temperature up to 800 K,respectively were determined.Our results of the thermophysical properties are also agree very well with other data of the literature,where for example at ambient temperature,the deviation between our obtained value(11.05 Cal mol^(−1)K^(−1))of C V,and the theoretical value(11.21 Cal mol^(−1)K^(−1))reported in the literature is only around 1.44%.The finite temperature thermophysical properties were found varied monotonically with either temperature or pressure.Compared with other materials previously studied,similar behaviors were observed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51922076 and 91941102)
文摘A good understanding of the thermophysical properties of hydrocarbon fuels at supercritical pressure is important to research on experiment and numerical simulation of fuel supercritical spray.Experimental measurements are difficult to conduct directly because of the extremely high pressure and high temperature.In this study,back propagation(BP)neural network,BP optimized by mind evolution algorithm(MEA-BP)and BP neural network optimized by genetic algorithm(GA-BP)are established to determine the nonlinear temperature-dependent thermophysical properties of density,viscosity,and isobaric specific heat(C_(2))of hydrocarbon fuels at supercritical pressure.Meanwhile,approximate formulas for these properties prediction are primarily proposed using polynomial fitting.In this paper,models that can predict three types of physical properties of three kinds of hydrocarbon fuels and their mixtures in a wide temperature range under supercritical pressure are established.In the prediction of density and C_(2),BP neural network has a good prediction effect.The results show that the MAPE is lower than 2%in the prediction of density and C_(2),but the MAPE of viscosity prediction is slightly higher than 5%using BP.Furthermore,MEA and GA are used to optimize the prediction of viscosity.The optimization effect and computation of the MEA is better than that of GA because MEA does not have the local optimization and prematurity problems.The present work offers an efficient tool to predict the thermophysical properties of hydrocarbon fuels over a wide range of temperatures under supercritical pressure which can be easily extended to other fuels of interest.It will be beneficial to the experiment and numerical simulation studies of supercritical sprays.
基金This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation(State assignment in the field of scientific activity,Southern Federal University,2020).
文摘The paper presents the results of a comprehensive study of the thermophysical properties(thermal conductivity,thermal diffusivity,heat capacity)of high-temperature multiferroic BiFeO_(3) modified with rare-earth elements(REEs)(La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Lu).The regularities of the formation of the mentioned characteristics were established.The assumptions about the nature of the observed phenomena were suggested.
基金The financial supports from the National Natural Science Foundation of China(Grant Nos.51671219 and 51429101)National Key Research and Development Plan(Grant No.2016YFB0701202)are greatly acknowledged.The work of GK was supported by nano-Ginop Project GINOP-2.3.2-15-2016-00027 in the framework of the Szechenyi 2020 program,supported by the European Union.
文摘A program CALTPP(CALculation of ThermoPhysical Properties)is developed in order to provide various thermophysical properties such as diffusion coefficient,interfacial energy,thermal conductivity,viscosity and molar volume mainly as function of temperature and composition.These thermophysical properties are very important inputs for microstructure simulations and mechanical property predictions.The general structure of CALTPP is briefly described,and the CALPHAD-type models for the description of these thermophysical properties are presented.The CALTPP program contains the input module,calculation and/or optimization modules and output module.A few case studies including(a)the calculation of diffusion coefficient and optimization of atomic mobility,(b)the calculation of solid/liquid,coherent solid/solid and liquid/liquid interfacial energies,(c)the calculation of thermal conductivity,(d)the calculation of viscosity,and(e)the establishment of molar volume database in binary and ternary alloys are demonstrated to show the features of CALTPP.It is expected that CALTPP will be an effective contribution in both scientific research and education.
基金supported by the National Natural Science Foundation of China(Grant No.52271320)"Mechanics+"interdisciplinary innovation youth fund project of Ningbo University(LJ2023005).
文摘With the increasing requirements for fast charging and discharging,higher requirements have been put forward for the thermal management of power batteries.Therefore,there is an urgent need to develop efficient heat transfer fluids.As a new type of heat transfer fluids,functional thermal fluids mainly includ-ing nanofluids(NFs)and phase change fluids(PCFs),have the advantages of high heat carrying density,high heat transfer rate,and broad operational temperature range.However,challenges that hinder their practical applications remain.In this paper,we firstly overview the classification,thermophysical prop-erties,drawbacks,and corresponding modifications of functional thermal fluids.For NFs,the high ther-mal conductivity and high convective heat transfer performance were mainly elaborated,while the stability and viscosity issues were also analyzed.And then for PCFs,the high heat carrying density was mainly elaborated,while the problems of supercooling,stability,and viscosity were also analyzed.On this basis,the composite fluids combined NFs and PCFs technology,has been summarized.Furthermore,the thermal properties of traditional fluids,NFs,PCFs,and composite fluids are compared,which proves that functional thermal fluids are a good choice to replace traditional fluids as coolants.Then,battery thermal management system(BTMS)based on functional thermal fluids is summarized in detail,and the thermal management effects and pump consumption are compared with that of water-based BTMS.Finally,the current technical challenges that parameters optimization of functional thermal fluids and structures optimization of BTMS systematically are presented.In the future,it is necessary to pay more attention to using machine learning to predict thermophysical properties of functional thermal fluids and their applications for BTMS under actual vehicle conditions.
基金supported by the National Natural Science Foundation of China(Nos.52175321,and 51771080).
文摘As a ceramic material,AlN has very good thermophysical and mechanical properties.In addition,AlN is an effective refining agent for Mg alloys because it has a lattice constant similar to that of Mg.Therefore,AlN is an ideal reinforcement for magnesium matrix composites(MMCs),and is attracting increasing attention.This review addresses the development of preparation technologies for AlN-reinforced Mg matrix composites.The mainstream preparation techniques include stir casting,melt infiltration,powder metallurgy,and in-situ methods.In addition,the advantages and disadvantages of these techniques are analyzed in depth,and it is pointed out that the next direction for the preparation of high-performance AlN-reinforced MMCs is less aluminization and multiple technologies integration.
文摘In this work,we have investigated the rotating effect on the thermodynamic properties of a 2D quantum ring.Accordingly,we have considered the radial potential of a 2D quantum ring and solved the Schrödinger equation in the presence of the Aharonov-Bohm effect and a uniform magnetic field for the considered potential.According to the solution of the equation,we calculated the eigenvalues and eigenfunctions of the considered system.Using the calculated energy spectrum,we obtained the partition function and thermodynamic properties of the system,such as the mean energy,specific heat,entropy and free energy.Our results show that the rotating effect has a significant influence on the thermophysical properties of a 2D quantum ring.We also study other effects of the rotating term:(1)the effect of different values of rotating parameters,and(2)the effect of negative rotation on the thermodynamic properties of the system.Our results are discussed in detail.
基金supported by Development and Use of Shallow Part Geothermal Energy below the Earth Surface and Research on Geothermal Reinjection Technology, the Basic Research Funding Project (SK201501)
文摘Thermophysical parameters are the main parameters affecting the utilization efficiency of shallow geothermal energy. Based on the research and evaluation data of shallow geothermal energy in capital cities of China, this paper analyzes the differences between two testing methods and finds that data measured in in-situ thermal conductivity test is closer to the actual utilization. This paper analyzes the influencing factors of thermophysical parameters from lithology, density, moisture content and porosity: The thermal conductivity coefficient of bedrock is generally higher than Quaternary system loose bed soil; as for the coefficient of bedrock, dolomite, shale and granite are higher while gabbro, sandstone and mudstone are lower; as for the coefficient of loose bed, pebble and gravel are higher while clay and silt are lower. As the particle size of sand decreases, the thermal conductivity coefficient declines accordingly. The thermal conductivity coefficient increases linearly with growing density and decreases in logarithm with growing moisture content as well as porosity; specific heat capacity decreases in logarithm with growing density, increases in power exponent with growing moisture content and decreases linearly with growing porosity. The thermal conductivity coefficient is high when hydrodynamic condition is good and vice versa. The conclusions of this paper have guiding significance for the research, evaluation and development of shallow geothermal energy in other areas.
基金the National Key Technologies Research and Development Program of China(No.2016YFC0701002)
文摘We prepared the nano-inorganic phase-change "alloy" materials through the modification of Na2SO4·10H2O using Na2HPO4·12H2O and GO nano-nucleating agent, and further investigated their thermophysical properties such as melting/solidification temperatures and enthalpies via differential scanning calorimetry. When the weight ratio of Na2SO4·10H2O and Na2HPO4·12H2O was 8:2 and the weight ratio of graphene oxide was 0.5% of phase change material, the phase change "alloy" material showed excellent performances, specifically, the melting temperature and latent heat were found to be 22 ℃ and 190 J/g with a degree of subcooling decreased from 8.6℃ to 2.1℃. In order to extend the application of the phase change "alloy" material to building energy saving field, it was adsorbed on expanded glass beads under vacuum and further covered with diatomite. When the adsorption rate of EGB(volume) and PCAM(weight) was 2.5:1, the particle size of diatomaceous earth was found to be 3.6μm, while the best packaging result was obtained with the melting temperature and latent heat being 21℃ and 135 J/g, and no leakage was observed.
文摘During both hot and cold seasons,masonry walls play an important role in the thermal performance between the interior and the exterior of occupied spaces.It is thus essential to analyze the thermal behavior at the hollow block’s level in order to better understand the temperature and heat flux distribution in its structure and potentially limit as much as possible the heat transfer through the block.In this scope,this paper offers an experimental and numerical in-depth analysis of heat transfer phenomena inside a hollow block using a dedicated experimental setup including a well-insulated reference box and several thermocouples and fluxmeters distributed at the boundaries and inside the hollow block.The block was then numerically 3D modelled and simulated using COMSOL Multiphysics under the same conditions,properties,and dimensions as the experimentally tested block.The comparison between the numerical and experimental results provides very satisfactory results with relative difference of less than 4%for the computed thermal resistance.
文摘A transient method with rectangular pulse heating has been developed to measure the thermal conductivity of highly porous materials such as activated carbon, zeolite and silica gel. By this method the thermal conductivity can be measured quickly and accu-rately. In this paper, a set of automatically controlled testing equiptnent is presented.The measuring method is analysed. The thermal conductivities of some samples, such as activated carbon and zeolite, are measured by the equipment. A group of useful data has been obtained.
基金the financial support from Yunnan Major Scientific and Technological Projects(No.202302AG050010)the Yunnan Fundamental Research Projects(Nos.202101AW070011 and 202101BE070001-015)+1 种基金the National Natural Science Foundation of China(No.52303295)the Project Funds of“Xingdian Talent Support Program”.Thanks to Professor Song Chen from Kunming Institute of Precious Metals for the discussion and usage of COMSOL software.
文摘The generation and evaluation of severely high thermal stress(σ)is known to be responsible for failure of thermal barrier coatings(TBCs)during thermal cycling.It is crucial and challenging to capture fluctuations inσcaused by the phase transition,which has motivated us to develop a high-throughput multiscale evaluation method forσin TBCs that considers the phase transition of the top ceramic materials by coupling first-principles calculations with finite element simulations.The method quantitatively evaluates and visualizesσof the real TBC structure under thermal cycling by multifield coupling.Additionally,the thermophysical properties calculated by the first-principles calculations consider the effects of temperature and phase transition,which not only reduces the cost of obtaining data but also has a more physical connotation.In this work,rare earth tantalites(RETaO4)are introduced as ceramic layers,and the results demonstrate thatσundergoes a rapid escalation near the phase transition temperature(Tt),particularly in the TBCs_GdTaO4 system,where it rises from 224 to 435 MPa.This discontinuity inσmay originate from the significant alterations in Young’s modulus(increase by 27%–78%)and thermal conductivity(increase by 53%–146%)near Tt.The TBCs_NdTaO4 and TBCs_SmTaO4 systems exhibit noteworthy temperature drop gradients and minimalσfluctuations,which are beneficial for extending service lifetime of TBCs.This approach facilitates the prediction of failure mechanisms and provides theoretical guidance for the reverse design of TBC materials to obtain low thermal stress systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1806219,52073232,52088101 and U1660108)the Science Fund for Distinguished Young Scholars of Shaanxi Province(Grant No.2020JC-11)the Science Fund for Scientific and Technological Innovation Team of Shaanxi Province(Grant No.2021TD-14)。
文摘Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties,liquid structure and crystal growth dependence on undercooling of Ti_(85)Ni_(10)Al_(5) alloy.The liquid Ti_(85)Ni_(10)Al_(5) alloy was substantially undercooled up to 335 K(0.18T_(L)).As undercooling increased,the potential energy of the liquid alloy decreased and the alloy entered into a high metastable state.At this state,the atoms tended to bond with each other and the clusters were inclined to convert into high-coordinated clusters,as confirmed by the fraction of the high-coordinated clusters variation.The enlarged clusters and enhanced local structure stability contributed to the increase of the thermophysical parameters and crystal growth velocity,and eventually dendrite refinement.The density,the specific heat and the surface tension of liquid alloy exhibited a linear relation with temperature and the shear viscosity of liquid alloy showed exponential variation which showed good agreement with the calculation results by molecular dynamics simulation.The growth velocity first increased slowly and then dramatically once the undercooling exceeded the threshold.The achieved maximum crystal growth velocity was 12.4 m s^(−1) and it was up to 326 times of the value at 94 K undercooling.
基金Authors would like to thank the Deanship of Scientific Research at King Saud University,Saudi Arabia,for financing this research under Research Group Project No.RG-1440-095.
文摘Thermophysical analysis of the crustal rocks is important for heat transfer determination and insulation purposes to save energy in buildings.In the presented work,thermophysical properties of four limestones were investigated in dry and moist state under ambient conditions by using a transient plane source method.A thermal constant analyzer was used to raise the sample temperature and to measure the thermal properties in the temperature range of 300 K to 433 K.Thermal conductivity and diffusivity were measured by developing a linear relationship between temperature response of TPS (transient plane source) sensor and dimensionless time function through least-square fitting method.The experimental observations and predicted thermal conductivity of samples have shown that in-situ observations are important to determine the thermal properties accurately.The effect of temperature on thermal properties of limestone was defined by considering the chemical composition of the samples and associated heat transfer mechanism.Both thermal conductivity and diffusivity of limestone decreased while specific heat capacity increased with a rise in temperature.The overall findings indicate that the spinoff of this research is useful in studying the reliance of thermophysical properties of rocks on their structures and lithology.
基金Project supported by National Natural Science Foundation of China(51174121,51274125)Zhejiang Province Science and Technology Innovation Team of Key Projects(2010R50016-30)
文摘Nd_9Fe_(85–x)Ti_4C_2B_x(x=10–15) magnetic alloys were investigated by differential thermal analysis and X-ray diffraction analysis. The results showed that with the B content increasing from 10 at.% to 15 at.%, the liquidus temperatures TL of the alloys decreased from 1498.5 to 1472.5 K; the solidus temperatures TS of them increased from 1353.2 to 1358.3 K; and the nucleation undercooling of the alloy melts cooled at the rate of 40 K/min decreased from 122.8 to 95.9 K, resulting in the solidification structures consisting of Nd_2Fe_(14)B, Fe_3B, α-Fe, Nd1.1Fe4B4 and TiC nanocrystallines. Furthermore, the Nd_9Fe_(85–x)Ti_4C_2B_x(x=11, 13, 15) bulk alloys in sheet form with the thickness of 0.7 mm were prepared by copper mold suction casting and their solidification characteristics and solidification structures under sub-rapidly cooling rate were investigated. The results showed that partially amorphous structures were obtained in the as-cast bulk alloys and the amount of amorphous decreased with the increase of the B content. By annealing the as-cast bulk alloys at 923 K for 10 min, the nanocomposite microstructures composed with Nd_2Fe_(14)B, Fe_3B and α-Fe nanocrystallines, which showed a single-phase hard magnetic behavior and enhanced magnetic properties, were achieved.