The tube inside and outside heat transfer mechanism of Passive Residual Heat Removal Heat Exchanger (PRHR HX) was analyzed. The calculation method of this special heat exchanger under natural convection condition in I...The tube inside and outside heat transfer mechanism of Passive Residual Heat Removal Heat Exchanger (PRHR HX) was analyzed. The calculation method of this special heat exchanger under natural convection condition in In-containment Refueling Water Storage Tank (IRWST) was carried out. The single-tube coupling model three-dimensional natural circulation in the IRWST was simulated numerically using Fluent. The heat transfer and flow characteristics of the fluid in IRWST were obtained. The comparison of the results between theoretical arithmetic and numerical simulation showed that the theoretical calculation method is suitable for the heat transfer calculation of PRHR HX.展开更多
The nonlinear process of microwave heating chemical reaction is studied by means of numerical simulation. Especially,the variation of temperature in terms of space and time,as well as the hotspot and thermal runaway p...The nonlinear process of microwave heating chemical reaction is studied by means of numerical simulation. Especially,the variation of temperature in terms of space and time,as well as the hotspot and thermal runaway phenomena are discussed. Suppose the heated object is a cylinder and the incident electromagnetic(EM) wave is plane wave,the problem turns out to be a coupling calculation of 2D multi-physical fields. The integral equation of EM field is solved using the method of moment(MoM) and the thermal conduction equation is solved using a semi-analysis method. Moreover,a method to determine the equivalent complex permittivity of reactant under the heating is presented in order to perform the calculation. The numerical results for water and a dummy chemical reaction(A) show that the hotspot is a ubiquitous phenomenon in microwave heating process. When the radius of the heated object is small,the highest temperature occurs somewhere inside the object due to the concentration of the EM wave. While the radius increases to a certain degree,the highest temperature occurs somewhere close to the surface due to the skin effect,and the whole high temperature area shows crescent-shaped. That is in accordance with basic physical principles. If the radius is kept the same in the heating process,the hotspot position of water does not change,while that of reaction A with several radius values varies. For either water or A,the thermal runaway phenomenon in which small difference of radius results in large difference of highest temperature,occurs easily when the radius is small. On the contrary,it is not evident when the radius is large. Moreover,it is notable that the highest temperature in water shows oscillating decreasing trend with the increase of radius,but in reaction A almost decreases monotonously. Further study should be performed to determine if this difference is only an occasional occurrence.展开更多
Considering the characteristic of selective heating of microwave and the treatment of titania-bearing BF slag, a mathematical model for the heating of a slag specimen is developed. The temperature distribution in the ...Considering the characteristic of selective heating of microwave and the treatment of titania-bearing BF slag, a mathematical model for the heating of a slag specimen is developed. The temperature distribution in the specimen is studied by numerical simulation. The temperature in the center of the cylindrical slag specimen is the highest and the temperature decreases when the radius increases rapidly. In this case, the temperature rising rate decreases with heating time rapidly, and it tends to zero when the heating time is up to 150 s.展开更多
A simplified simulation method based on the FDTD technique that can handle active devices is proposed. This method well suits the electrical crosstalk analysis of multi-channel integrated, opto-electronic mixed module...A simplified simulation method based on the FDTD technique that can handle active devices is proposed. This method well suits the electrical crosstalk analysis of multi-channel integrated, opto-electronic mixed modules. We apply this method to an 8-channel integrated super-compact high-sensitivity optical module. The results show good agreement between simulations and measurements.展开更多
As hydraulic fracturing was forbidden in some countries due to possible negative environmental impacts and enhanced coalbed methane(ECBM)was restricted by in-situ conditions,microwave heating was proposed to enhance c...As hydraulic fracturing was forbidden in some countries due to possible negative environmental impacts and enhanced coalbed methane(ECBM)was restricted by in-situ conditions,microwave heating was proposed to enhance coalbed permeability.One of the mechanisms of improving coal permeability with microwave irradiation is that thermal expansion caused by microwave heating.To study the influence of microwave’s heating effect of coal samples,the simulations were conducted using a coupled electromagnetic,thermal and mechanical model in this paper.The temperature,Von-Mises stress and strain distribution of coal sample are recorded every 10 s.The permeability distribution is also obtained based on the relationship between strain and permeability from articles.It was found that volume average temperature,stress,strain and permeability increase almost linearly with time.The average permeability increased from 1.65 10×16 m^2 to 3.63 10×16 m^2 under 2.45 GHz and 500Wmicrowave radiation after 300 s.The significant increase proved microwave to be effective in coal seam permeability enhancement.展开更多
The interactions of electromagnetic waves with the human body are complex and depend on several factors related to the characteristics of the incident wave, including its frequency, its intensity, the polarization of ...The interactions of electromagnetic waves with the human body are complex and depend on several factors related to the characteristics of the incident wave, including its frequency, its intensity, the polarization of the tissue encountered, the geometry of the tissue and its electromagnetic properties. That’s to say, the dielectric permittivity, the conductivity and the type of coupling between the field and the exposed body. A biological system irradiated by an electromagnetic wave is traversed by induced currents of non-negligible density;the water molecules present in the biological tissues exposed to the electromagnetic field will begin to oscillate at the frequency of the incident wave, thus creating internal friction responsible for the heating of the irradiated tissues. This heating will be all the more important as the tissues are rich in water. This article presents the establishment from a mathematical and numerical analysis explaining the phenomena of interaction and consequences between electromagnetic waves and health. Since the total electric field in the biological system is unknown, that is why it can be determined by the Finite Difference Time Domain FDTD method to assess the electromagnetic power distribution in the biological system under study. For this purpose, the detailed on the mechanisms of interaction of microwave electromagnetic waves with the human body have been presented. Mathematical analysis using Maxwell’s equations as well as bio-heat equations is the basis of this study for a consistent result. Therefore, a thermal model of biological tissues based on an electrical analogy has been developed. By the principle of duality, an electrical model in the dielectric form of a multilayered human tissue was used in order to obtain a corresponding thermal model. This thermal model made it possible to evaluate the temperature profile of biological tissues during exposure to electromagnetic waves. The simulation results obtained from computer tools show that the temperature in the biological tissue is a linear function of the duration of exposure to microwave electromagnetic waves.展开更多
Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromag...Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromagnetic parameters were obtained from the previous studies. Owing to the induction heating of a high frequency electromagnetic field （20 kHz）, the thickness of initial solidification shell decreases, and the temperature of strand surface and slit copper mold increases when compared with the case without the electromagnetic filed. The viscosity of flux de- creases because of the induction heating of the high frequency electromagnetic field, and the dimension of the flux channel increases with electromagnetic pressure; thus, the deformation behavior of initial solidification shell was different before and after the action of high frequency electromagnetic field. Furthermore, the abatement mechanism of oscillation marks under high frequency electromagnetic field was explained.展开更多
Several parameter identification methods of thermal response test were evaluated through numerical and experimental study.A three-dimensional finite-volume numerical model was established under the assumption that the...Several parameter identification methods of thermal response test were evaluated through numerical and experimental study.A three-dimensional finite-volume numerical model was established under the assumption that the soil thermal conductivity had been known in the simulation of thermal response test.The thermal response curve was firstly obtained through numerical calculation.Then,the accuracy of the numerical model was verified with measured data obtained through a thermal response test.Based on the numerical and experimental thermal response curves,the thermal conductivity of the soil was calculated by different parameter identification methods.The calculated results were compared with the assumed value and then the accuracy of these methods was evaluated.Furthermore,the effects of test time,variable data quality,borehole radius,initial ground temperature,and heat injection rate were analyzed.The results show that the method based on cylinder-source model has a low precision and the identified thermal conductivity decreases with an increase in borehole radius.For parameter estimation,the measuring accuracy of the initial temperature of the deep ground soil has greater effect on identified thermal conductivity.展开更多
The boundary heat flow has important significance for the microstructures of directional solidified binary alloy.Interface evolution of the directional solidified microstructure with different boundary heat flow was d...The boundary heat flow has important significance for the microstructures of directional solidified binary alloy.Interface evolution of the directional solidified microstructure with different boundary heat flow was discussed.In this study, only one interface was allowed to have heat flow, and Neumann boundary conditions were imposed at the other three interfaces.From the calculated results, it was found that different boundary heat flows will result in different microstructures.When the boundary heat flow equals to 20 W·cm-2, the growth of longitudinal side branches is accelerated and the growth of transverse side branches is restrained, and meanwhile, there is dendritic remelting in the calculation domain.When the boundary heat flow equals to 40 W·cm-2, the growths of the transverse and longitudinal side branches compete with each other, and when the boundary heat flow equals to 100-200 W·cm-2, the growth of transverse side branches dominates absolutely.The temperature field of dendritic growth was analyzed and the relation between boundary heat flow and temperature field was also investigated.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
This work is focused on the development of computational algorithms to create a simulator for solving the heat transfer during the continuous casting process of steel. The temperatures and the solid shell thickness pr...This work is focused on the development of computational algorithms to create a simulator for solving the heat transfer during the continuous casting process of steel. The temperatures and the solid shell thickness profiles were calculated and displayed on the screen for a billet through a defined continuous casting plant （CCP）. The algorithms developed to calculate billet temperatures, involve the solutions of the corresponding equations for the heat removal conditions such as radiation, forced convection, and conduction according to the billet posi- tion through the CCP. This is done by a simultaneous comparison with the kinematics model previously developed. A finite difference method known as Cmnk-Nicholson is applied to solve the two-dimensional computational array （2D model）. Enthalpy （HIJ） and temperature （TIL） in every node are updated at each step time. The routines to display the results have been developed using a graphical user interface （GUI） in the programming language C＋＋. Finally, the results obtained are compared with those of industrial trials for the surface temperature of three steel casters with different plant configurations in different casting conditions.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
In order to investigate the temperature distribution, a three-dimensional finite element model （FEM） was developed to simulate the temperature regime in the channels of double-loop inductor, and the simulated result...In order to investigate the temperature distribution, a three-dimensional finite element model （FEM） was developed to simulate the temperature regime in the channels of double-loop inductor, and the simulated results were compared with experimental data from low load trials of a 400 kW inductor. The results of numerical simulations, such as the temperature and Joule heating rate, show reasonable correlation with experimental data. The results indicate that Joule heating rate and the temperature reach the maximum at the comers and the minimum at the centre of the cross-section area. The temperature difference between the inlet and outlet is in an inverse proportion to mass transport. Joule heating rate and the temperature are directly proportional to power frequency. It is concluded that mass transport and power frequency play a critical role in determining the temperature regime and Joule heating rate, the relative permeability of the magnetic core shows no significant influence on temperature regime and Joule heating rate, when the relative permeability varies from 5 000 to 10 000.展开更多
The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element ...The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.展开更多
In mine geothermal prediction, the unsteady heat transfer coefficient is an important parameter for heat transfer computation between country rock and mine airflow. In this paper, the rock temperature distributions in...In mine geothermal prediction, the unsteady heat transfer coefficient is an important parameter for heat transfer computation between country rock and mine airflow. In this paper, the rock temperature distributions in the geothermal fields have been derived in mathematics, the unsteady heat transfer coefficients that can expound the relation between its nature and influencing factors have been derived also based on this analytic formula. It is shown both by numerical simulations and through in situ measurernents that the new computation method for determining the unsteady heat transfer cofeeicient is accurate, rapid and simple.展开更多
文摘The tube inside and outside heat transfer mechanism of Passive Residual Heat Removal Heat Exchanger (PRHR HX) was analyzed. The calculation method of this special heat exchanger under natural convection condition in In-containment Refueling Water Storage Tank (IRWST) was carried out. The single-tube coupling model three-dimensional natural circulation in the IRWST was simulated numerically using Fluent. The heat transfer and flow characteristics of the fluid in IRWST were obtained. The comparison of the results between theoretical arithmetic and numerical simulation showed that the theoretical calculation method is suitable for the heat transfer calculation of PRHR HX.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 60801035 and 60531010)
文摘The nonlinear process of microwave heating chemical reaction is studied by means of numerical simulation. Especially,the variation of temperature in terms of space and time,as well as the hotspot and thermal runaway phenomena are discussed. Suppose the heated object is a cylinder and the incident electromagnetic(EM) wave is plane wave,the problem turns out to be a coupling calculation of 2D multi-physical fields. The integral equation of EM field is solved using the method of moment(MoM) and the thermal conduction equation is solved using a semi-analysis method. Moreover,a method to determine the equivalent complex permittivity of reactant under the heating is presented in order to perform the calculation. The numerical results for water and a dummy chemical reaction(A) show that the hotspot is a ubiquitous phenomenon in microwave heating process. When the radius of the heated object is small,the highest temperature occurs somewhere inside the object due to the concentration of the EM wave. While the radius increases to a certain degree,the highest temperature occurs somewhere close to the surface due to the skin effect,and the whole high temperature area shows crescent-shaped. That is in accordance with basic physical principles. If the radius is kept the same in the heating process,the hotspot position of water does not change,while that of reaction A with several radius values varies. For either water or A,the thermal runaway phenomenon in which small difference of radius results in large difference of highest temperature,occurs easily when the radius is small. On the contrary,it is not evident when the radius is large. Moreover,it is notable that the highest temperature in water shows oscillating decreasing trend with the increase of radius,but in reaction A almost decreases monotonously. Further study should be performed to determine if this difference is only an occasional occurrence.
基金This study was financially supported by the National Basic Research Program of China (No.2007CB613503).
文摘Considering the characteristic of selective heating of microwave and the treatment of titania-bearing BF slag, a mathematical model for the heating of a slag specimen is developed. The temperature distribution in the specimen is studied by numerical simulation. The temperature in the center of the cylindrical slag specimen is the highest and the temperature decreases when the radius increases rapidly. In this case, the temperature rising rate decreases with heating time rapidly, and it tends to zero when the heating time is up to 150 s.
文摘A simplified simulation method based on the FDTD technique that can handle active devices is proposed. This method well suits the electrical crosstalk analysis of multi-channel integrated, opto-electronic mixed modules. We apply this method to an 8-channel integrated super-compact high-sensitivity optical module. The results show good agreement between simulations and measurements.
文摘As hydraulic fracturing was forbidden in some countries due to possible negative environmental impacts and enhanced coalbed methane(ECBM)was restricted by in-situ conditions,microwave heating was proposed to enhance coalbed permeability.One of the mechanisms of improving coal permeability with microwave irradiation is that thermal expansion caused by microwave heating.To study the influence of microwave’s heating effect of coal samples,the simulations were conducted using a coupled electromagnetic,thermal and mechanical model in this paper.The temperature,Von-Mises stress and strain distribution of coal sample are recorded every 10 s.The permeability distribution is also obtained based on the relationship between strain and permeability from articles.It was found that volume average temperature,stress,strain and permeability increase almost linearly with time.The average permeability increased from 1.65 10×16 m^2 to 3.63 10×16 m^2 under 2.45 GHz and 500Wmicrowave radiation after 300 s.The significant increase proved microwave to be effective in coal seam permeability enhancement.
文摘The interactions of electromagnetic waves with the human body are complex and depend on several factors related to the characteristics of the incident wave, including its frequency, its intensity, the polarization of the tissue encountered, the geometry of the tissue and its electromagnetic properties. That’s to say, the dielectric permittivity, the conductivity and the type of coupling between the field and the exposed body. A biological system irradiated by an electromagnetic wave is traversed by induced currents of non-negligible density;the water molecules present in the biological tissues exposed to the electromagnetic field will begin to oscillate at the frequency of the incident wave, thus creating internal friction responsible for the heating of the irradiated tissues. This heating will be all the more important as the tissues are rich in water. This article presents the establishment from a mathematical and numerical analysis explaining the phenomena of interaction and consequences between electromagnetic waves and health. Since the total electric field in the biological system is unknown, that is why it can be determined by the Finite Difference Time Domain FDTD method to assess the electromagnetic power distribution in the biological system under study. For this purpose, the detailed on the mechanisms of interaction of microwave electromagnetic waves with the human body have been presented. Mathematical analysis using Maxwell’s equations as well as bio-heat equations is the basis of this study for a consistent result. Therefore, a thermal model of biological tissues based on an electrical analogy has been developed. By the principle of duality, an electrical model in the dielectric form of a multilayered human tissue was used in order to obtain a corresponding thermal model. This thermal model made it possible to evaluate the temperature profile of biological tissues during exposure to electromagnetic waves. The simulation results obtained from computer tools show that the temperature in the biological tissue is a linear function of the duration of exposure to microwave electromagnetic waves.
基金Item Sponsored by National Natural Science Foundation of China (59734080)
文摘Heat transfer and deformation of initial solidification shell in soft contact continuous casting mold under high frequency electromagnetic field were analyzed using numerical simulation method; the relative electromagnetic parameters were obtained from the previous studies. Owing to the induction heating of a high frequency electromagnetic field （20 kHz）, the thickness of initial solidification shell decreases, and the temperature of strand surface and slit copper mold increases when compared with the case without the electromagnetic filed. The viscosity of flux de- creases because of the induction heating of the high frequency electromagnetic field, and the dimension of the flux channel increases with electromagnetic pressure; thus, the deformation behavior of initial solidification shell was different before and after the action of high frequency electromagnetic field. Furthermore, the abatement mechanism of oscillation marks under high frequency electromagnetic field was explained.
基金Project(xjj20100078) supported by the Fundamental Research Funds for the Central Universities in China
文摘Several parameter identification methods of thermal response test were evaluated through numerical and experimental study.A three-dimensional finite-volume numerical model was established under the assumption that the soil thermal conductivity had been known in the simulation of thermal response test.The thermal response curve was firstly obtained through numerical calculation.Then,the accuracy of the numerical model was verified with measured data obtained through a thermal response test.Based on the numerical and experimental thermal response curves,the thermal conductivity of the soil was calculated by different parameter identification methods.The calculated results were compared with the assumed value and then the accuracy of these methods was evaluated.Furthermore,the effects of test time,variable data quality,borehole radius,initial ground temperature,and heat injection rate were analyzed.The results show that the method based on cylinder-source model has a low precision and the identified thermal conductivity decreases with an increase in borehole radius.For parameter estimation,the measuring accuracy of the initial temperature of the deep ground soil has greater effect on identified thermal conductivity.
文摘The boundary heat flow has important significance for the microstructures of directional solidified binary alloy.Interface evolution of the directional solidified microstructure with different boundary heat flow was discussed.In this study, only one interface was allowed to have heat flow, and Neumann boundary conditions were imposed at the other three interfaces.From the calculated results, it was found that different boundary heat flows will result in different microstructures.When the boundary heat flow equals to 20 W·cm-2, the growth of longitudinal side branches is accelerated and the growth of transverse side branches is restrained, and meanwhile, there is dendritic remelting in the calculation domain.When the boundary heat flow equals to 40 W·cm-2, the growths of the transverse and longitudinal side branches compete with each other, and when the boundary heat flow equals to 100-200 W·cm-2, the growth of transverse side branches dominates absolutely.The temperature field of dendritic growth was analyzed and the relation between boundary heat flow and temperature field was also investigated.
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.
文摘This work is focused on the development of computational algorithms to create a simulator for solving the heat transfer during the continuous casting process of steel. The temperatures and the solid shell thickness profiles were calculated and displayed on the screen for a billet through a defined continuous casting plant （CCP）. The algorithms developed to calculate billet temperatures, involve the solutions of the corresponding equations for the heat removal conditions such as radiation, forced convection, and conduction according to the billet posi- tion through the CCP. This is done by a simultaneous comparison with the kinematics model previously developed. A finite difference method known as Cmnk-Nicholson is applied to solve the two-dimensional computational array （2D model）. Enthalpy （HIJ） and temperature （TIL） in every node are updated at each step time. The routines to display the results have been developed using a graphical user interface （GUI） in the programming language C＋＋. Finally, the results obtained are compared with those of industrial trials for the surface temperature of three steel casters with different plant configurations in different casting conditions.
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(50876116) supported by the National Natural Science Foundation of ChinaProject(2007CK3077) supported by the Innovative Program of Hunan Science and Technology Agency, ChinaProject(1343-77225) supported by the Graduate School of Central South University, China
文摘In order to investigate the temperature distribution, a three-dimensional finite element model （FEM） was developed to simulate the temperature regime in the channels of double-loop inductor, and the simulated results were compared with experimental data from low load trials of a 400 kW inductor. The results of numerical simulations, such as the temperature and Joule heating rate, show reasonable correlation with experimental data. The results indicate that Joule heating rate and the temperature reach the maximum at the comers and the minimum at the centre of the cross-section area. The temperature difference between the inlet and outlet is in an inverse proportion to mass transport. Joule heating rate and the temperature are directly proportional to power frequency. It is concluded that mass transport and power frequency play a critical role in determining the temperature regime and Joule heating rate, the relative permeability of the magnetic core shows no significant influence on temperature regime and Joule heating rate, when the relative permeability varies from 5 000 to 10 000.
基金Project supported by the National Natural Science Foundation of China (Nos. 12102043, 12072375U2241240)the Natural Science Foundation of Hunan Province of China (Nos. 2023JJ40698 and 2021JJ40710)。
文摘The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.
文摘In mine geothermal prediction, the unsteady heat transfer coefficient is an important parameter for heat transfer computation between country rock and mine airflow. In this paper, the rock temperature distributions in the geothermal fields have been derived in mathematics, the unsteady heat transfer coefficients that can expound the relation between its nature and influencing factors have been derived also based on this analytic formula. It is shown both by numerical simulations and through in situ measurernents that the new computation method for determining the unsteady heat transfer cofeeicient is accurate, rapid and simple.
