In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations...In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations which are widely used in metallic thermal protection systems on reusable launch vehicles and high-temperature fuel cells. The effective thermal conductivities（ECTs） which are measured experimentally can hardly be used separately to analyze the heat transfer behaviors of conduction and radiation for high-temperature insulation. By fitting the effective thermal conductivities with experimental data, the equivalent radiation transmittance, absorptivity and reflectivity, as well as a linear function to describe the relationship between temperature and conductivity can be estimated by an inverse problems method. The deviation between the calculated and measured effective thermal conductivities is less than 4%. Using the material parameters so obtained for conduction and radiation, the heat transfer process in multilayer thermal insulation（MTI） is calculated and the deviation between the calculated and the measured transient temperatures at a certain depth in the multilayer thermal insulation is less than 6.5%.展开更多
This research was conducted to study the performances of the heat and multilayer reflection insulators used for buildings in South Korea to realize eco-friendly, low-energy-consumption, green construction, and to cont...This research was conducted to study the performances of the heat and multilayer reflection insulators used for buildings in South Korea to realize eco-friendly, low-energy-consumption, green construction, and to contribute to energy consumption reduction in buildings and to the nation＇s greenhouse gas emission reduction policy （targeting 30% reduction compared to BAUCousiness as usual） by 2020）. The heat insulation performance test is about the temperatures on surfaces of test piece. The high air temperature and the low air temperature were measured to determine the overall heat transfer coefficient and thermal conductivity. The conclusions are drawn that the heat transmission coefficients for each type of existing reflection insulator are： A-1 （0.045 W/（m-K））, A-2 （0.031 W/（m.K））, A-3 （0.042 W/（m.K））, A-4 （0.078 W/（m.K））, and the average heat conductivity is 0.049 W/（m-K）; The heat conductivity for each type of Styrofoam insulator are 0.030 W/（m.K） for B-l, 0.032 W/（m-K） for B-2, 0.037 W/（m＇K） for B-3, 0.037 W/（m.K） for B-4, and the average heat conductivity is 0.035 W/（m＇K） regardless of the thickness of the insulator; The heat conductivity values of the multilayer reflection insulators are converted based on the thickness and type C-1 （0.020 W/（m.K））, C-2 （0.018 W/（m.K））, C-3 （0.016 W/（m.K））, and C-4 （0.012 W/（m.K））; The multilayer reflection insulator keeps the indoor-side surface temperature high （during winter） or low （in summer）, enhances the comfort of the building occupants, and conducts heating and moisture resistance to prevent dew condensation on the glass-outer-wall surface.展开更多
Light emission by inelastic tunneling(LEIT)from a metal-insulator-metal tunnel junction is an ultrafast emission process.It is a promising platform for ultrafast transduction from electrical signal to optical signal o...Light emission by inelastic tunneling(LEIT)from a metal-insulator-metal tunnel junction is an ultrafast emission process.It is a promising platform for ultrafast transduction from electrical signal to optical signal on integrated circuits.However,existing procedures of fabricating LEIT devices usually involve both top-down and bottom-up techniques,which reduces its compatibility with the modern microfabrication streamline and limits its potential applications in industrial scale-up.Here in this work,we lift these restrictions by using a multilayer insulator grown by atomic layer deposition as the tunnel barrier.For the first time,we fabricate an LEIT device fully by microfabrication techniques and show a stable performance under ambient conditions.Uniform electroluminescence is observed over the entire active region,with the emission spectrum shaped by metallic grating plasmons.The introduction of a multilayer insulator into the LEIT can provide an additional degree of freedom for engineering the energy band landscape of the tunnel barrier.The presented scheme of preparing a stable ultrathin tunnel barrier may also find some applications in a wide range of integrated optoelectronic devices.展开更多
We employ the Dirac cone model to explore the high Chern number(C)phases that are realized in the magnetic-doped topological insulator(TI)multilayer structures by Zhao et al.[Nature 588419(2020)].The Chern number is c...We employ the Dirac cone model to explore the high Chern number(C)phases that are realized in the magnetic-doped topological insulator(TI)multilayer structures by Zhao et al.[Nature 588419(2020)].The Chern number is calculated by capturing the evolution of the phase boundaries with the parameters,then the Chern number phase diagrams of the TI multilayer structures are obtained.The high-C behavior is attributed to the band inversion of the renormalized Dirac cones,along with which the spin polarization at theΓpoint will get increased.Moreover,another two TI multilayer structures as well as the TI superlattice structures are studied.展开更多
The paper introduces a microreactor with high thermal insulation properties,which has been developed forintegration with standard planar-type solid oxide fuel cells(SOFCs)in portable power generation applications.Whil...The paper introduces a microreactor with high thermal insulation properties,which has been developed forintegration with standard planar-type solid oxide fuel cells(SOFCs)in portable power generation applications.Whileplanar SOFCs offer high efficiency and energy density,their use has been largely limited to stationary applications dueto challenges in thermal management and slow start-up times.Our microreactor overcomes these barriers byproviding an effective thermal insulation system,allowing SOFCs to operate efficiently in a compact,portable format.We designed a cantilevered structure using yttria-stabilized zirconia(YSZ)to minimize thermal conduction andcombined it with a multilayer insulation(MLI)system to suppress thermal radiation loss.This flexible cantileveredstructure prevents cracking under thermal stress and maintains high temperatures up to 700℃,ensuring reliableoperation.Additionally,the MLI system features an inherent safety mechanism:when the insulation structure isdamaged by a drill,the loss of thermal insulation causes a rapid temperature drop,bringing the system below thehydrogen explosion threshold temperature within 5 minutes,thus preventing potential hazards.Our prototypesuccessfully demonstrated handheld power generation using a button-type metal-supported SOFC,achieving a rapidstart-up time of just 5 minutes and driving a motor.This breakthrough offers a new platform for miniaturized SOFCtechnology,bridging the gap between stationary and portable energy solutions.展开更多
In order to restrain cement kiln shell＇ s thermal loss and potential safety hazards,composite design was employed of working layer,thermal preservation layer and thermal insulation layer.Thermal preservation layer＇ ...In order to restrain cement kiln shell＇ s thermal loss and potential safety hazards,composite design was employed of working layer,thermal preservation layer and thermal insulation layer.Thermal preservation layer＇ s boundary and strain were analyzed and the overall thermal conductivity was calculated.The result shows that the sinusoidal curve boundary combination is adopted between the working layer and thermal preservation layer,and the slope-shape with angle of 135 degrees between the thermal preservation layer and thermal insulation layer could relieve the strain concentration.Comprehensive thermal conductivity of the composite mullite brick decreases from the working layer 2.74 W·m^（-1）·K^（-1） to1.54 W·m^（-1）·K^（-1）.When applying the composite bricks in cement kilns,the kiln shell temperature is from50 ℃ to 70 ℃ lower than using normal bricks.展开更多
Liquid hydrogen(LH2)is a highly preferred fuel for propelling large-ton Martian landers.Currently,composite insulation structures(CISs),consisting of multilayer insulation(MLI)and spray-on foam insulation(SOFI)are use...Liquid hydrogen(LH2)is a highly preferred fuel for propelling large-ton Martian landers.Currently,composite insulation structures(CISs),consisting of multilayer insulation(MLI)and spray-on foam insulation(SOFI)are used for the thermal protection of cryogenic propellant tanks.However,the Martian environment poses significant challenges for the thermal protection of LH2 tanks,primarily because of the presence of rarefied carbon dioxide(CO_(2)).CO_(2)can condense within the MLI microchannels,leading to significant deterioration in the insulation performance of CIS.This study investigates this unique phenomenon occurring on Mars.Two thermal-insulation schemes are designed for potential applications in Martian landers.Numerical models are developed to predict the insulation performance of CIS on Mars by coupling CO_(2)condensation and conduction calculations within microchannels.Several key findings emerge:(1)The heat leakage decreases by 82.22%as SOFI thickness increases from 5 to 50 mm.(2)The heat leakage initially rises sharply,and then increases gradually with ambient Martian temperature.(3)The insulation performance deteriorates rapidly and then stabilizes as the number of MLI layers increases,but the heat leakage of CIS exceeds 10 W/m^(2).(4)A new type of insulation scheme(NIS)aimed at solving the issue in finding(3)is designed for the Mars lander by prioritizing the minimum weight which results in an NIS heat leakage of 0.298 W/m2—two to four orders of magnitude lower than that of CISs.These findings provide valuable technical insights into enhancing the thermal protection of LH2 propellant tanks.展开更多
基金supported by China Building Materials Research Institute
文摘In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations which are widely used in metallic thermal protection systems on reusable launch vehicles and high-temperature fuel cells. The effective thermal conductivities（ECTs） which are measured experimentally can hardly be used separately to analyze the heat transfer behaviors of conduction and radiation for high-temperature insulation. By fitting the effective thermal conductivities with experimental data, the equivalent radiation transmittance, absorptivity and reflectivity, as well as a linear function to describe the relationship between temperature and conductivity can be estimated by an inverse problems method. The deviation between the calculated and measured effective thermal conductivities is less than 4%. Using the material parameters so obtained for conduction and radiation, the heat transfer process in multilayer thermal insulation（MTI） is calculated and the deviation between the calculated and the measured transient temperatures at a certain depth in the multilayer thermal insulation is less than 6.5%.
基金Project(NRF-2010-0024155) supported by the National Research Foundation of Korea
文摘This research was conducted to study the performances of the heat and multilayer reflection insulators used for buildings in South Korea to realize eco-friendly, low-energy-consumption, green construction, and to contribute to energy consumption reduction in buildings and to the nation＇s greenhouse gas emission reduction policy （targeting 30% reduction compared to BAUCousiness as usual） by 2020）. The heat insulation performance test is about the temperatures on surfaces of test piece. The high air temperature and the low air temperature were measured to determine the overall heat transfer coefficient and thermal conductivity. The conclusions are drawn that the heat transmission coefficients for each type of existing reflection insulator are： A-1 （0.045 W/（m-K））, A-2 （0.031 W/（m.K））, A-3 （0.042 W/（m.K））, A-4 （0.078 W/（m.K））, and the average heat conductivity is 0.049 W/（m-K）; The heat conductivity for each type of Styrofoam insulator are 0.030 W/（m.K） for B-l, 0.032 W/（m-K） for B-2, 0.037 W/（m＇K） for B-3, 0.037 W/（m.K） for B-4, and the average heat conductivity is 0.035 W/（m＇K） regardless of the thickness of the insulator; The heat conductivity values of the multilayer reflection insulators are converted based on the thickness and type C-1 （0.020 W/（m.K））, C-2 （0.018 W/（m.K））, C-3 （0.016 W/（m.K））, and C-4 （0.012 W/（m.K））; The multilayer reflection insulator keeps the indoor-side surface temperature high （during winter） or low （in summer）, enhances the comfort of the building occupants, and conducts heating and moisture resistance to prevent dew condensation on the glass-outer-wall surface.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12004222 and 91850207)the National Key Research and Development Program of China (Grant Nos. 2017YFA0303504 and 2017YFA0205800)+2 种基金the Fundamental Research Funds for the Central Universities, Chinathe Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000)the Postdoctoral Science Foundation of China (Grant No. 2020M682223)
文摘Light emission by inelastic tunneling(LEIT)from a metal-insulator-metal tunnel junction is an ultrafast emission process.It is a promising platform for ultrafast transduction from electrical signal to optical signal on integrated circuits.However,existing procedures of fabricating LEIT devices usually involve both top-down and bottom-up techniques,which reduces its compatibility with the modern microfabrication streamline and limits its potential applications in industrial scale-up.Here in this work,we lift these restrictions by using a multilayer insulator grown by atomic layer deposition as the tunnel barrier.For the first time,we fabricate an LEIT device fully by microfabrication techniques and show a stable performance under ambient conditions.Uniform electroluminescence is observed over the entire active region,with the emission spectrum shaped by metallic grating plasmons.The introduction of a multilayer insulator into the LEIT can provide an additional degree of freedom for engineering the energy band landscape of the tunnel barrier.The presented scheme of preparing a stable ultrathin tunnel barrier may also find some applications in a wide range of integrated optoelectronic devices.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11804122 and 11905054)the China Postdoctoral Science Foundation(Grant No.2021M690970)the Fundamental Research Funds for the Central Universities of China.
文摘We employ the Dirac cone model to explore the high Chern number(C)phases that are realized in the magnetic-doped topological insulator(TI)multilayer structures by Zhao et al.[Nature 588419(2020)].The Chern number is calculated by capturing the evolution of the phase boundaries with the parameters,then the Chern number phase diagrams of the TI multilayer structures are obtained.The high-C behavior is attributed to the band inversion of the renormalized Dirac cones,along with which the spin polarization at theΓpoint will get increased.Moreover,another two TI multilayer structures as well as the TI superlattice structures are studied.
基金supported by the following funding sources:JSPS KAKENHI Grant-in-Aid for Scientific Research(B),Grant Numbers 23K26749 and 23K21047the NEDO Project for the Promotion of Young Researchers in Industry-Academia-Government Collaboration+1 种基金and the ERCA Innovative Research and Development Program(Young Researcher Category)supported by joint research funds from Futaba Industrial Co.,Ltd.and TAIYO YUDEN Co.,Ltd.
文摘The paper introduces a microreactor with high thermal insulation properties,which has been developed forintegration with standard planar-type solid oxide fuel cells(SOFCs)in portable power generation applications.Whileplanar SOFCs offer high efficiency and energy density,their use has been largely limited to stationary applications dueto challenges in thermal management and slow start-up times.Our microreactor overcomes these barriers byproviding an effective thermal insulation system,allowing SOFCs to operate efficiently in a compact,portable format.We designed a cantilevered structure using yttria-stabilized zirconia(YSZ)to minimize thermal conduction andcombined it with a multilayer insulation(MLI)system to suppress thermal radiation loss.This flexible cantileveredstructure prevents cracking under thermal stress and maintains high temperatures up to 700℃,ensuring reliableoperation.Additionally,the MLI system features an inherent safety mechanism:when the insulation structure isdamaged by a drill,the loss of thermal insulation causes a rapid temperature drop,bringing the system below thehydrogen explosion threshold temperature within 5 minutes,thus preventing potential hazards.Our prototypesuccessfully demonstrated handheld power generation using a button-type metal-supported SOFC,achieving a rapidstart-up time of just 5 minutes and driving a motor.This breakthrough offers a new platform for miniaturized SOFCtechnology,bridging the gap between stationary and portable energy solutions.
基金National Key Technology Research and Development Program of China during the "12~(th) Five-Year Plan"(No. 2013BAE03B01-10)
文摘In order to restrain cement kiln shell＇ s thermal loss and potential safety hazards,composite design was employed of working layer,thermal preservation layer and thermal insulation layer.Thermal preservation layer＇ s boundary and strain were analyzed and the overall thermal conductivity was calculated.The result shows that the sinusoidal curve boundary combination is adopted between the working layer and thermal preservation layer,and the slope-shape with angle of 135 degrees between the thermal preservation layer and thermal insulation layer could relieve the strain concentration.Comprehensive thermal conductivity of the composite mullite brick decreases from the working layer 2.74 W·m^（-1）·K^（-1） to1.54 W·m^（-1）·K^（-1）.When applying the composite bricks in cement kilns,the kiln shell temperature is from50 ℃ to 70 ℃ lower than using normal bricks.
基金supported by the National Natural Science Foundation of China(Grant No.51906184)the China Postdoctoral Science Foundation(Grant Nos.2021T140538 and 2020M673391).
文摘Liquid hydrogen(LH2)is a highly preferred fuel for propelling large-ton Martian landers.Currently,composite insulation structures(CISs),consisting of multilayer insulation(MLI)and spray-on foam insulation(SOFI)are used for the thermal protection of cryogenic propellant tanks.However,the Martian environment poses significant challenges for the thermal protection of LH2 tanks,primarily because of the presence of rarefied carbon dioxide(CO_(2)).CO_(2)can condense within the MLI microchannels,leading to significant deterioration in the insulation performance of CIS.This study investigates this unique phenomenon occurring on Mars.Two thermal-insulation schemes are designed for potential applications in Martian landers.Numerical models are developed to predict the insulation performance of CIS on Mars by coupling CO_(2)condensation and conduction calculations within microchannels.Several key findings emerge:(1)The heat leakage decreases by 82.22%as SOFI thickness increases from 5 to 50 mm.(2)The heat leakage initially rises sharply,and then increases gradually with ambient Martian temperature.(3)The insulation performance deteriorates rapidly and then stabilizes as the number of MLI layers increases,but the heat leakage of CIS exceeds 10 W/m^(2).(4)A new type of insulation scheme(NIS)aimed at solving the issue in finding(3)is designed for the Mars lander by prioritizing the minimum weight which results in an NIS heat leakage of 0.298 W/m2—two to four orders of magnitude lower than that of CISs.These findings provide valuable technical insights into enhancing the thermal protection of LH2 propellant tanks.
