Building is an important scenario for achieving global carbon peak and carbon neutrality goals,accounting for approximately 37%of global energy-related CO_(2) emissions in 2020.In the meanwhile,the construction and op...Building is an important scenario for achieving global carbon peak and carbon neutrality goals,accounting for approximately 37%of global energy-related CO_(2) emissions in 2020.In the meanwhile,the construction and operation of buildings was responsible for 36%of global energy consumption,of which 30%energy was used for space heating.Therefore,this paper proposes a low-carbon building heating system that is coupled to a new semiconductor radiation heating unit and distributed rooftop photovoltaic to reduce carbon emissions.To reveal its building heating characteristics,a dynamic model of heat transfer based on semiconductor low-temperature radiant heating is first established by analyzing the heat conduction,convection,and radiation models,and the uncertainty from both the distributed rooftop photovoltaic and building heating demand is considered in the building heating operation strategy.Then,a simulation model of a low-carbon building heating system is built in MATLAB/SIMULINK for two different climate zones in China(Beijing and Wuhan).When building and using the low-carbon building heating system stable for 30 years,the payback period is 5.2–8.2 years in Beijing and 6.4–11.6 years in Wuhan.Compared with the traditional grid-powered heating system,the simulation revealed that the carbon emissions of Beijing and Wuhan during the heating season are reduced by 44.9%and 44.3%,respectively,and the corresponding building heating cost is saved by 62.1%and 57.8%.展开更多
Numerical study was performed to evaluate the characteristics of combined heat transfer of radiation, conduction and convection in indirect near infrared ray （N/R） heating chamber. The effects of important design pa...Numerical study was performed to evaluate the characteristics of combined heat transfer of radiation, conduction and convection in indirect near infrared ray （N/R） heating chamber. The effects of important design parameters such as the shape of heat absorbing cylinder and heat releasing fin on the pressure drop and heat transfer coefficient were analyzed with different Reynolds numbers. The Reynolds numbers were varied from 103 to 3x106, which was defined based on the hydraulic diameter of the heat absorbing cylinder. Analyses were performed to obtain the inner and outer flow and the temperature distributions in the heat absorbing cylinder and the rates of radiation heat transfer and convection heat transfer. As the Reynolds number increases, the convection heat transfer rate is increased while the radiation heat transfer rate is decreased. The average convection heat transfer rate follows a power rule of the Reynolds number. Addition of three-dimensional heat releasing fin to the outside of the heat absorbing cylinder enhances the convection heat transfer.展开更多
This is the first report of using the microwave heating technique to synthesize calcium sulphide activated by europium whose structure is determined as the face-centered cubic by conventional X-ray powder diffraction ...This is the first report of using the microwave heating technique to synthesize calcium sulphide activated by europium whose structure is determined as the face-centered cubic by conventional X-ray powder diffraction method. The phosphor has maximum excitation peaks located at 280 urn and 560 urn and the maximum emission of the phosphor is 630 nm. When the concentration of Eu^(2+) in CaS increases from I .0 × 10^(-5) to l.0 × 10^(-2) mole per mole host, the body colour of the calcium sulphide activated with europium changes from white, through light-red to pink to deep-red. The phosphor obtains the longest afterglow at the concentration of 0.1% Eu^(2+)doped and is a kind of good material excited by sunlight.展开更多
Satellite-derived data of the outgoing longwave radiation (OLR), net shortwave radiation at thetropopause (SRT) and circulation information as predicted by NCEP are used in the work to study seasonal variations of net...Satellite-derived data of the outgoing longwave radiation (OLR), net shortwave radiation at thetropopause (SRT) and circulation information as predicted by NCEP are used in the work to study seasonal variations of net radiative heating in the earth-atmospheric system and its relationship with the Asian summer monsoon. As is shown in the result, the zonal deviations of the zonal deviations of the heating, manifested as mutations in direction between land and sea with seasons, is an indication of the thermal difference between them.Being a month earlier than that in the general circulation from spring to summer, the seasonal reversal of directionmay be playing an essential role in triggering the onset and withdrawal of summer monsoon in Asia.展开更多
A new hybrid method, Monte-Carlo-Heat-Flux （MCHF） method, was presented to analyze the radiative heat transfer of participating medium in a three-dimensional rectangular enclosure using combined the Monte-Carlo meth...A new hybrid method, Monte-Carlo-Heat-Flux （MCHF） method, was presented to analyze the radiative heat transfer of participating medium in a three-dimensional rectangular enclosure using combined the Monte-Carlo method with the heat flux method. Its accuracy and reliability was proved by comparing the computational results with exact results from classical ＂Zone Method＂.展开更多
This paper introduces a new model for the Fourier law of heat conduction with the time-fractional order to the generalized Maxwell fluid. The flow is influenced by magnetic field, radiation heat, and heat source. A fr...This paper introduces a new model for the Fourier law of heat conduction with the time-fractional order to the generalized Maxwell fluid. The flow is influenced by magnetic field, radiation heat, and heat source. A fractional calculus approach is used to establish the constitutive relationship coupling model of a viscoelastic fluid. We use the Laplace transform and solve ordinary differential equations with a matrix form to obtain the velocity and temperature in the Laplace domain. To obtain solutions from the Laplace space back to the original space, the numerical inversion of the Laplace transform is used. According to the results and graphs, a new theory can be constructed. Comparisons of the associated parameters and the corresponding flow and heat transfer characteristics are presented and analyzed in detail.展开更多
For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is develo...For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.展开更多
Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reve...Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reveal the influence of piloti on the radiant environment of residential blocks systematically. Taking the city of Guangzhou as an example,using 3-D Unsteady State Heat Balance Radiation Calculation Method,this paper shows that the mean radiant temperature( MRT) under piloti area increases with the increase of piloti ratio,and especially when piloti ratio is equal to 100%,the MRT increase trend becomes sharp. The MRT of exposed area decreases with the increase of piloti ratio,especially when piloti ratio reaches 100%,the decrease trend of MRT becomes sharp,which offers the reference for the study on piloti design in subtropical climate zones and further research on living environment by CFD simulation in residential blocks.展开更多
The results stemming from the calculation of heat transfer in torch furnaces by the laws, relating to radiation from solid surfaces and gas volumes are analyzed. The article presents the laws for radiation from gas vo...The results stemming from the calculation of heat transfer in torch furnaces by the laws, relating to radiation from solid surfaces and gas volumes are analyzed. The article presents the laws for radiation from gas volumes and the procedure for calculating heat transfer in torch furnaces, fire boxes, and combustion chambers, elaborated on their basis. The example of heat transfer calculation in a torch furnace is given, and it is significantly non-uniform in nature. Non-uniformity of heat flux distribution on heating surfaces is given. According to the results of calculations, a new furnace is designed to decrease the non-uniformity of ingot heating, fuel rate, and increase the furnace capacity. The calculation results of the distribution of heat fluxes on the heating surfaces are given in changing torch geometric dimensions. These results are confirmed by experimental studies.展开更多
A concise formula for computing radiation heat flow of in-cylinder soot is presented, based on the assumptions that in-cylinder heat transfer of diesel engines is a quasi-equilibrium process and in-cylinder soot parti...A concise formula for computing radiation heat flow of in-cylinder soot is presented, based on the assumptions that in-cylinder heat transfer of diesel engines is a quasi-equilibrium process and in-cylinder soot particles are spherical. That in this formula there consist neither constants needing adjustments nor variables related to engine types or operating conditions makes it universal and easy to use. Also it can be seen from the formula that radiation heat transfer is proportional to the quotient of in-cylinder soot mass over the average radius of primary particles. Besides, with the help of different algorithms it can be used for predicting cylinders＇ global as well as local radiation heat flows. As a demonstrative application on its global facet, a three-dimension simulation study about the soot-radiation-related heat flow in the combustion chamber of a diesel engine is carried out. Results show that the range of the soot-radiation-related heat flow computed by this formula agrees well with other researcher＇s earlier theoretic reasoning and experimental measurements.展开更多
The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a re...The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a refined soil parameterization scheme. Simulation results presented that as soil moisture availability increases, the Bowen ratio and the partition of net radiation flux into sensible and soil heat fluxes decrease. The partition of net radiation flux into latent heat flux, however, increases. Quantitative relationships between Bowen ratio and the partitions with soil moisture availability were also given in this study.展开更多
Micropores are decisive to mechanical properties and thermal deformation capabilities of powder met-allurgy(P/M)Ti alloys sintered compacts.As a result,achieving express densification is of prime im-portance and has a...Micropores are decisive to mechanical properties and thermal deformation capabilities of powder met-allurgy(P/M)Ti alloys sintered compacts.As a result,achieving express densification is of prime im-portance and has attracted increasing attention recently.Induction heating owns the merits of high effi-ciency,short process,and low cost,and thus has huge potential to be used as a sintering approach for the fabrication of P/M Ti alloys.Nevertheless,the facilitated densification behavior associated with induction heating sintering remains unclear so far.To address it,powder metallurgy Ti6Al4V is manufactured via induction heating sintering with which the underlying sintering mechanism is investigated in-depth.It is found that induction heating could generate a fully densified compact in a remarkably shortened time,demonstrating its superior sintering efficiency as compared with conventional resistance furnace heat-ing.COMSOL finite element analysis reveals that the maximum current density during induction heating can reach 10^(6)A m^(–2)though the magnetic field strength is solely 0.02 T,leading to a slight tempera-ture difference of approximately 30℃between the interior and exterior of the billet.Furthermore,the rapid heating essentially starts at sharp corners of particles due to the potent current concentration ef-fect,which facilitates the cracking of the particle surface oxide film and thus enhances the direct contact between them.Moreover,the electromigration effect caused by induction current promotes the diffusion capability of elements,giving rise to expedited densification,alloying,and chemical homogenization.This work provides not only critical insight into the sintering mechanism of induction heating sintering but also significant guidance for low-cost powder metallurgy materials preparation.展开更多
Phase change materials are one of the potential resources to replace fossil fuels in regards of supplying the energy of buildings.Basically,these materials absorb or release heat energy with the help of their latent h...Phase change materials are one of the potential resources to replace fossil fuels in regards of supplying the energy of buildings.Basically,these materials absorb or release heat energy with the help of their latent heat.Phase change materials have low thermal conductivity and this makes it possible to use the physical properties of these materials in the tropical regions where the solar radiation is more direct and concentrated over a smaller area.In this theoretical work,an attempt has been made to study the melting process of these materials by applying constant heat flux and temperature.It was found that by increasing the thickness of phase change materials’layers,due to the melting,more thermal energy is stored.Simultaneously it reduces the penetration of excessive heat into the chamber,so that by increasing the thickness of paraffin materials up to 20 mm,the rate of temperature reduction reaches more than 18%.It was also recognized that increasing the values of constant input heat flux increases buoyancy effects.Increasing the Stefan number from 0.1 to 0.3,increases the temperature by 6%.展开更多
This paper is concerned with the stationary plane contact of an insulated rigid punch and a half-space which is elastically anisotropic but thermally conducting. The frictional heat generation inside the contact regio...This paper is concerned with the stationary plane contact of an insulated rigid punch and a half-space which is elastically anisotropic but thermally conducting. The frictional heat generation inside the contact region due to the sliding of the punch over the half-space surface and the heat radiation outside the contact region are taken into account. With the help of Fourier integral transform, the problem is reduced to a system of two singular integral equations. The equations are solved numerically by using Gauss-Jacobi and trapezoidal-rule quadratures. The effects of anisotropy and thermal effects are shown graphically.展开更多
An innovative flat heat pipe radiator was put forward, and it has the features of high efficiency of heat dissipation, compact construction, low thermal resistance, light weight, low cost, and anti-dust-deposition. Th...An innovative flat heat pipe radiator was put forward, and it has the features of high efficiency of heat dissipation, compact construction, low thermal resistance, light weight, low cost, and anti-dust-deposition. The thermal analysis of the flat heat pipe radiator for cooling high-power light emitting diode （LED） array was conducted. The thermal characteristics of the flat heat pipe radiator under the different heat loads and incline angles were investigated experimentally in natural convection. An electro-thermal conversion method was used to measure the junction temperature of the LED chips. It is found that the integral temperature distribution of the flat heat pipe radiator is reasonable and uniform. The total thermal resistance of the flat heat pipe radiator varies in the range of 0.38-0.45 K/W. The junction temperatures of LED chips with the flat heat pipe radiator and with the aluminum board at the same forward current of 0.35 A are 52.5 and 75.2 ℃, respectively.展开更多
Spacecraft flexible appendages may experience thermally induced vibrations(TIV)under sudden heating loads,which in consequence will be unable to complete their intended missions.Isogeometric analysis(IGA)utilizes,in a...Spacecraft flexible appendages may experience thermally induced vibrations(TIV)under sudden heating loads,which in consequence will be unable to complete their intended missions.Isogeometric analysis(IGA)utilizes,in an isoparametric concept,the same high order and high continuity non-uniform rational B-splines(NURBS)to represent both the geometry and the physical field of the structure.Compared to the traditional Lagrange polynomial based finite element method where only C0-continuity across elements can be achieved,IGA is geometrically exact and naturally fulfills the C1-continuity requirement of Euler–Bernoulli(EB)beam elements,therefore,does not need extra rotational degrees-of-freedom.In this paper,we present a thermally induced vibration analysis framework based on the isogeometric method where thermal and structural behaviors are coupled.We fully exploited the higher order,higher continuous and geometric exactness of the NURBS basis with both benchmarks and sophisticated problems.In particular,we studied the thermally induced vibrations of the Hubble Space Telescope(HST)solar panel where main factors influencing thermal flutters are studied,and where possible improvements of the analytical reference methods are discussed.Additionally,thermally induced vibrations of the thin-walled lenticular tubes are studied and two new configurations of the tube are proposed to effectively suppress the thermally induced vibrations.Numerical examples of both benchmarks and sophisticated problems confirm the accuracy and efficiency of the isogeometric analysis framework for thermally induced vibration analysis of space structures.展开更多
This paper gives a brief description of annual period and seasonal variation in the wave height field entropy in the northeastern Pacific. A calculation of the quantity of the, received by lithosphere systems in the n...This paper gives a brief description of annual period and seasonal variation in the wave height field entropy in the northeastern Pacific. A calculation of the quantity of the, received by lithosphere systems in the northern hemisphere is introduced. The wave heat field entropy is compared with the difference in the quantity of the sun＇s radiation heat. Analysis on the transfer method, period and lag of this seasonal variation led to the conclusion that the annual period and seasonal variation in the entropy of the wave height field in the Northwestern Pacific is due to the seasonal variation of the sun＇s radiation heat. Furthermore, the inconsistency between thermodynamic entropy and information entropy was studied.展开更多
The purpose of this paper is to present the design and performance of a skylight using a mathematical model. This model uses weather data from the Finnish city Helsinki to assess its performance. This skylight could a...The purpose of this paper is to present the design and performance of a skylight using a mathematical model. This model uses weather data from the Finnish city Helsinki to assess its performance. This skylight could act as a radiative cooler or as a thermal insulator depending on the need. This versatile usage would thus decrease the need for traditional air-conditioning and hence save electricity. The skylight would consist of one normal silica glass window and of two polymer windows with a grcenhousc gas trapped in the spaces between the windows. The skylight would be in its cooling mode when the two spaces would be connected to each other and insulating when disconnected. Thus when cooling, a natural convective flow transports heat from the 1o~ er part of the skylight to the upper part of the skylight where the greenhouse gas is cooled by radiative heat exchange with the sky.展开更多
Based on the analysis of heat radiation intensity from flame, a new mathematical model ofthe tube-wall temperatmp of heated tubes is developed by taking down-fired, upright-tube cylindricalfurnace for example. The pro...Based on the analysis of heat radiation intensity from flame, a new mathematical model ofthe tube-wall temperatmp of heated tubes is developed by taking down-fired, upright-tube cylindricalfurnace for example. The proposed mathematical model can be employed to indicate both the positionand size of the hot spot at fire-facing wall of heated tube of combustion chamber, and is characteristicof simplicity and efficiency If coupled with thermoelectric couple or infrared viewer, the presentedlocation method of combustion hot spot can offer engineers very valuable proposal to keep furnacerunning more safely The same is true for any other type of tubular furnaces.展开更多
Satellite＇s thermal control subsystem （TCS） has to maintain components and structure within their specified temperature limits during satellite service life. TCS designers have to face the challenge of reducing bot...Satellite＇s thermal control subsystem （TCS） has to maintain components and structure within their specified temperature limits during satellite service life. TCS designers have to face the challenge of reducing both the weight of the system and required heater power while keeping components temperature within their design range. For a space based heat pipe radiator system, several researchers have published different approaches to reach such goal. This paper presents a thermal design and optimization of a heat pipe radiator applied to a practical engineering design application. For this study, a prospective communication satellite payload panel with applied passive thermal control techniques was considered. The thermal passive techniques used in this design mainly include multilayer insulation （MLI） blankets, optical solar reflectors （OSR）, selected thermal coatings, interface fillers and constant conductance heat pipes. The heat pipe network is comprised of some heat pipes embedded in the panel and some mounted on inner surface of the panel. Embedded heat pipes are placed under high heat dissipation equipments and their size is fixed; minimum weight of the radiator is achieved by a minimum weight of the mounted heat pipes. Hence, size of the mounted heat pipes is optimized. A thermal model was built and parameterized for transient thermal analysis and optimization. Temperature requirements of components in both worst case conditions （Hot case and cold case） were satisfied under optimal sizing of mounted heat pipes.展开更多
基金supported by the National Natural Science Foundation of China(No.52006114).
文摘Building is an important scenario for achieving global carbon peak and carbon neutrality goals,accounting for approximately 37%of global energy-related CO_(2) emissions in 2020.In the meanwhile,the construction and operation of buildings was responsible for 36%of global energy consumption,of which 30%energy was used for space heating.Therefore,this paper proposes a low-carbon building heating system that is coupled to a new semiconductor radiation heating unit and distributed rooftop photovoltaic to reduce carbon emissions.To reveal its building heating characteristics,a dynamic model of heat transfer based on semiconductor low-temperature radiant heating is first established by analyzing the heat conduction,convection,and radiation models,and the uncertainty from both the distributed rooftop photovoltaic and building heating demand is considered in the building heating operation strategy.Then,a simulation model of a low-carbon building heating system is built in MATLAB/SIMULINK for two different climate zones in China(Beijing and Wuhan).When building and using the low-carbon building heating system stable for 30 years,the payback period is 5.2–8.2 years in Beijing and 6.4–11.6 years in Wuhan.Compared with the traditional grid-powered heating system,the simulation revealed that the carbon emissions of Beijing and Wuhan during the heating season are reduced by 44.9%and 44.3%,respectively,and the corresponding building heating cost is saved by 62.1%and 57.8%.
基金supported by the Second Stage of Brain Korea 21 Projects
文摘Numerical study was performed to evaluate the characteristics of combined heat transfer of radiation, conduction and convection in indirect near infrared ray （N/R） heating chamber. The effects of important design parameters such as the shape of heat absorbing cylinder and heat releasing fin on the pressure drop and heat transfer coefficient were analyzed with different Reynolds numbers. The Reynolds numbers were varied from 103 to 3x106, which was defined based on the hydraulic diameter of the heat absorbing cylinder. Analyses were performed to obtain the inner and outer flow and the temperature distributions in the heat absorbing cylinder and the rates of radiation heat transfer and convection heat transfer. As the Reynolds number increases, the convection heat transfer rate is increased while the radiation heat transfer rate is decreased. The average convection heat transfer rate follows a power rule of the Reynolds number. Addition of three-dimensional heat releasing fin to the outside of the heat absorbing cylinder enhances the convection heat transfer.
基金This work was supported by the National NatUral Science Foundation of China! (No 59982003) Guangdong Provincial NatUral Scie
文摘This is the first report of using the microwave heating technique to synthesize calcium sulphide activated by europium whose structure is determined as the face-centered cubic by conventional X-ray powder diffraction method. The phosphor has maximum excitation peaks located at 280 urn and 560 urn and the maximum emission of the phosphor is 630 nm. When the concentration of Eu^(2+) in CaS increases from I .0 × 10^(-5) to l.0 × 10^(-2) mole per mole host, the body colour of the calcium sulphide activated with europium changes from white, through light-red to pink to deep-red. The phosphor obtains the longest afterglow at the concentration of 0.1% Eu^(2+)doped and is a kind of good material excited by sunlight.
文摘Satellite-derived data of the outgoing longwave radiation (OLR), net shortwave radiation at thetropopause (SRT) and circulation information as predicted by NCEP are used in the work to study seasonal variations of net radiative heating in the earth-atmospheric system and its relationship with the Asian summer monsoon. As is shown in the result, the zonal deviations of the zonal deviations of the heating, manifested as mutations in direction between land and sea with seasons, is an indication of the thermal difference between them.Being a month earlier than that in the general circulation from spring to summer, the seasonal reversal of directionmay be playing an essential role in triggering the onset and withdrawal of summer monsoon in Asia.
基金financially supported by the National Natural Science Foundation of China (No.50464004)
文摘A new hybrid method, Monte-Carlo-Heat-Flux （MCHF） method, was presented to analyze the radiative heat transfer of participating medium in a three-dimensional rectangular enclosure using combined the Monte-Carlo method with the heat flux method. Its accuracy and reliability was proved by comparing the computational results with exact results from classical ＂Zone Method＂.
基金Project supported by the China Postdoctoral Science Foundation(No.2015M580069)
文摘This paper introduces a new model for the Fourier law of heat conduction with the time-fractional order to the generalized Maxwell fluid. The flow is influenced by magnetic field, radiation heat, and heat source. A fractional calculus approach is used to establish the constitutive relationship coupling model of a viscoelastic fluid. We use the Laplace transform and solve ordinary differential equations with a matrix form to obtain the velocity and temperature in the Laplace domain. To obtain solutions from the Laplace space back to the original space, the numerical inversion of the Laplace transform is used. According to the results and graphs, a new theory can be constructed. Comparisons of the associated parameters and the corresponding flow and heat transfer characteristics are presented and analyzed in detail.
基金financially supported by the Program for New Century Excellent Talents in University(No.NCET-13-0229,NCET-09-0396)the National Science & Technology Key Projects of Numerical Control(No.2012ZX04010-031,2012ZX0412-011)the National High Technology Research and Development Program("863"Program)of China(No.2013031003)
文摘For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.
基金Sponsored by the Strategic Japanese-Chinese Cooperation Program (Grant No.2011DFA91210)the Fundamental Research Funds for the Central Universities (Grant No.HIT.NSRIF.2014075),the Fundamental Research Funds for the Central Universities (Grant No.HIT.KISTP.201419)the Natural Science Foundation of Heilongjiang Province (Grant No.E201316)
文摘Piloti is commonly used in tropical and subtropical climate zones to get high wind velocity and create shadowed areas in order to optimize the living environment of residential blocks,but there are few studies to reveal the influence of piloti on the radiant environment of residential blocks systematically. Taking the city of Guangzhou as an example,using 3-D Unsteady State Heat Balance Radiation Calculation Method,this paper shows that the mean radiant temperature( MRT) under piloti area increases with the increase of piloti ratio,and especially when piloti ratio is equal to 100%,the MRT increase trend becomes sharp. The MRT of exposed area decreases with the increase of piloti ratio,especially when piloti ratio reaches 100%,the decrease trend of MRT becomes sharp,which offers the reference for the study on piloti design in subtropical climate zones and further research on living environment by CFD simulation in residential blocks.
文摘The results stemming from the calculation of heat transfer in torch furnaces by the laws, relating to radiation from solid surfaces and gas volumes are analyzed. The article presents the laws for radiation from gas volumes and the procedure for calculating heat transfer in torch furnaces, fire boxes, and combustion chambers, elaborated on their basis. The example of heat transfer calculation in a torch furnace is given, and it is significantly non-uniform in nature. Non-uniformity of heat flux distribution on heating surfaces is given. According to the results of calculations, a new furnace is designed to decrease the non-uniformity of ingot heating, fuel rate, and increase the furnace capacity. The calculation results of the distribution of heat fluxes on the heating surfaces are given in changing torch geometric dimensions. These results are confirmed by experimental studies.
基金Sponsored by the National "973" Program Projects(652345)
文摘A concise formula for computing radiation heat flow of in-cylinder soot is presented, based on the assumptions that in-cylinder heat transfer of diesel engines is a quasi-equilibrium process and in-cylinder soot particles are spherical. That in this formula there consist neither constants needing adjustments nor variables related to engine types or operating conditions makes it universal and easy to use. Also it can be seen from the formula that radiation heat transfer is proportional to the quotient of in-cylinder soot mass over the average radius of primary particles. Besides, with the help of different algorithms it can be used for predicting cylinders＇ global as well as local radiation heat flows. As a demonstrative application on its global facet, a three-dimension simulation study about the soot-radiation-related heat flow in the combustion chamber of a diesel engine is carried out. Results show that the range of the soot-radiation-related heat flow computed by this formula agrees well with other researcher＇s earlier theoretic reasoning and experimental measurements.
文摘The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a refined soil parameterization scheme. Simulation results presented that as soil moisture availability increases, the Bowen ratio and the partition of net radiation flux into sensible and soil heat fluxes decrease. The partition of net radiation flux into latent heat flux, however, increases. Quantitative relationships between Bowen ratio and the partitions with soil moisture availability were also given in this study.
基金supported by the National Key Research and Development Program of China(No.2020YFB2008300)the National Natural Science Foundation of China(Nos.51971097 and 52301147)+2 种基金the Young Elite Scientist Sponsorship Program by China Association for Science and Technology(No.YESS20210054)the Hubei Province Natural Science Foundation(No.ZRMS2022000863)the Fundamental Research Funds for the Central Universities of Huazhong University of Science and Technology(No.2172021XXJS010)and the project supported by State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.
文摘Micropores are decisive to mechanical properties and thermal deformation capabilities of powder met-allurgy(P/M)Ti alloys sintered compacts.As a result,achieving express densification is of prime im-portance and has attracted increasing attention recently.Induction heating owns the merits of high effi-ciency,short process,and low cost,and thus has huge potential to be used as a sintering approach for the fabrication of P/M Ti alloys.Nevertheless,the facilitated densification behavior associated with induction heating sintering remains unclear so far.To address it,powder metallurgy Ti6Al4V is manufactured via induction heating sintering with which the underlying sintering mechanism is investigated in-depth.It is found that induction heating could generate a fully densified compact in a remarkably shortened time,demonstrating its superior sintering efficiency as compared with conventional resistance furnace heat-ing.COMSOL finite element analysis reveals that the maximum current density during induction heating can reach 10^(6)A m^(–2)though the magnetic field strength is solely 0.02 T,leading to a slight tempera-ture difference of approximately 30℃between the interior and exterior of the billet.Furthermore,the rapid heating essentially starts at sharp corners of particles due to the potent current concentration ef-fect,which facilitates the cracking of the particle surface oxide film and thus enhances the direct contact between them.Moreover,the electromigration effect caused by induction current promotes the diffusion capability of elements,giving rise to expedited densification,alloying,and chemical homogenization.This work provides not only critical insight into the sintering mechanism of induction heating sintering but also significant guidance for low-cost powder metallurgy materials preparation.
文摘Phase change materials are one of the potential resources to replace fossil fuels in regards of supplying the energy of buildings.Basically,these materials absorb or release heat energy with the help of their latent heat.Phase change materials have low thermal conductivity and this makes it possible to use the physical properties of these materials in the tropical regions where the solar radiation is more direct and concentrated over a smaller area.In this theoretical work,an attempt has been made to study the melting process of these materials by applying constant heat flux and temperature.It was found that by increasing the thickness of phase change materials’layers,due to the melting,more thermal energy is stored.Simultaneously it reduces the penetration of excessive heat into the chamber,so that by increasing the thickness of paraffin materials up to 20 mm,the rate of temperature reduction reaches more than 18%.It was also recognized that increasing the values of constant input heat flux increases buoyancy effects.Increasing the Stefan number from 0.1 to 0.3,increases the temperature by 6%.
文摘This paper is concerned with the stationary plane contact of an insulated rigid punch and a half-space which is elastically anisotropic but thermally conducting. The frictional heat generation inside the contact region due to the sliding of the punch over the half-space surface and the heat radiation outside the contact region are taken into account. With the help of Fourier integral transform, the problem is reduced to a system of two singular integral equations. The equations are solved numerically by using Gauss-Jacobi and trapezoidal-rule quadratures. The effects of anisotropy and thermal effects are shown graphically.
基金Project(50876016) support by the National Natural Science Foundation of China
文摘An innovative flat heat pipe radiator was put forward, and it has the features of high efficiency of heat dissipation, compact construction, low thermal resistance, light weight, low cost, and anti-dust-deposition. The thermal analysis of the flat heat pipe radiator for cooling high-power light emitting diode （LED） array was conducted. The thermal characteristics of the flat heat pipe radiator under the different heat loads and incline angles were investigated experimentally in natural convection. An electro-thermal conversion method was used to measure the junction temperature of the LED chips. It is found that the integral temperature distribution of the flat heat pipe radiator is reasonable and uniform. The total thermal resistance of the flat heat pipe radiator varies in the range of 0.38-0.45 K/W. The junction temperatures of LED chips with the flat heat pipe radiator and with the aluminum board at the same forward current of 0.35 A are 52.5 and 75.2 ℃, respectively.
基金Y.Guo would like to thank the National Natural Science Foundation of China(Grant No.11972187)and Priority Academic Program Development of Jiangsu Higher Education Institutions for their support.
文摘Spacecraft flexible appendages may experience thermally induced vibrations(TIV)under sudden heating loads,which in consequence will be unable to complete their intended missions.Isogeometric analysis(IGA)utilizes,in an isoparametric concept,the same high order and high continuity non-uniform rational B-splines(NURBS)to represent both the geometry and the physical field of the structure.Compared to the traditional Lagrange polynomial based finite element method where only C0-continuity across elements can be achieved,IGA is geometrically exact and naturally fulfills the C1-continuity requirement of Euler–Bernoulli(EB)beam elements,therefore,does not need extra rotational degrees-of-freedom.In this paper,we present a thermally induced vibration analysis framework based on the isogeometric method where thermal and structural behaviors are coupled.We fully exploited the higher order,higher continuous and geometric exactness of the NURBS basis with both benchmarks and sophisticated problems.In particular,we studied the thermally induced vibrations of the Hubble Space Telescope(HST)solar panel where main factors influencing thermal flutters are studied,and where possible improvements of the analytical reference methods are discussed.Additionally,thermally induced vibrations of the thin-walled lenticular tubes are studied and two new configurations of the tube are proposed to effectively suppress the thermally induced vibrations.Numerical examples of both benchmarks and sophisticated problems confirm the accuracy and efficiency of the isogeometric analysis framework for thermally induced vibration analysis of space structures.
基金Supported by the High-Tech Research and Development Program of China (863 Program, No. 2001AA633070 2003AA604040).
文摘This paper gives a brief description of annual period and seasonal variation in the wave height field entropy in the northeastern Pacific. A calculation of the quantity of the, received by lithosphere systems in the northern hemisphere is introduced. The wave heat field entropy is compared with the difference in the quantity of the sun＇s radiation heat. Analysis on the transfer method, period and lag of this seasonal variation led to the conclusion that the annual period and seasonal variation in the entropy of the wave height field in the Northwestern Pacific is due to the seasonal variation of the sun＇s radiation heat. Furthermore, the inconsistency between thermodynamic entropy and information entropy was studied.
文摘The purpose of this paper is to present the design and performance of a skylight using a mathematical model. This model uses weather data from the Finnish city Helsinki to assess its performance. This skylight could act as a radiative cooler or as a thermal insulator depending on the need. This versatile usage would thus decrease the need for traditional air-conditioning and hence save electricity. The skylight would consist of one normal silica glass window and of two polymer windows with a grcenhousc gas trapped in the spaces between the windows. The skylight would be in its cooling mode when the two spaces would be connected to each other and insulating when disconnected. Thus when cooling, a natural convective flow transports heat from the 1o~ er part of the skylight to the upper part of the skylight where the greenhouse gas is cooled by radiative heat exchange with the sky.
基金This project is supported by National Natural Science Foundation of China(No.50175081).
文摘Based on the analysis of heat radiation intensity from flame, a new mathematical model ofthe tube-wall temperatmp of heated tubes is developed by taking down-fired, upright-tube cylindricalfurnace for example. The proposed mathematical model can be employed to indicate both the positionand size of the hot spot at fire-facing wall of heated tube of combustion chamber, and is characteristicof simplicity and efficiency If coupled with thermoelectric couple or infrared viewer, the presentedlocation method of combustion hot spot can offer engineers very valuable proposal to keep furnacerunning more safely The same is true for any other type of tubular furnaces.
文摘Satellite＇s thermal control subsystem （TCS） has to maintain components and structure within their specified temperature limits during satellite service life. TCS designers have to face the challenge of reducing both the weight of the system and required heater power while keeping components temperature within their design range. For a space based heat pipe radiator system, several researchers have published different approaches to reach such goal. This paper presents a thermal design and optimization of a heat pipe radiator applied to a practical engineering design application. For this study, a prospective communication satellite payload panel with applied passive thermal control techniques was considered. The thermal passive techniques used in this design mainly include multilayer insulation （MLI） blankets, optical solar reflectors （OSR）, selected thermal coatings, interface fillers and constant conductance heat pipes. The heat pipe network is comprised of some heat pipes embedded in the panel and some mounted on inner surface of the panel. Embedded heat pipes are placed under high heat dissipation equipments and their size is fixed; minimum weight of the radiator is achieved by a minimum weight of the mounted heat pipes. Hence, size of the mounted heat pipes is optimized. A thermal model was built and parameterized for transient thermal analysis and optimization. Temperature requirements of components in both worst case conditions （Hot case and cold case） were satisfied under optimal sizing of mounted heat pipes.
